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* [PATCH v7 00/16] fscrypt: key management improvements
@ 2019-07-26 22:41 Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h> Eric Biggers
                   ` (15 more replies)
  0 siblings, 16 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

Hello,

[Note: I'd like to apply this for v5.4.  Additional review is greatly
 appreciated, especially of the API before it's set in stone.  Thanks!]

This patchset makes major improvements to how keys are added, removed,
and derived in fscrypt, aka ext4/f2fs/ubifs encryption.  It does this by
adding new ioctls that add and remove encryption keys directly to/from
the filesystem, and by adding a new encryption policy version ("v2")
where the user-provided keys are only used as input to HKDF-SHA512 and
are identified by their cryptographic hash.

All new APIs and all cryptosystem changes are documented in
Documentation/filesystems/fscrypt.rst.  Userspace can use the new key
management ioctls with existing encrypted directories, but migrating to
v2 encryption policies is needed for the full benefits.

These changes solve four interrelated problems:

(1) Providing fscrypt keys via process-subscribed keyrings is abusing
    encryption as an OS-level access control mechanism, causing many
    bugs where processes don't get access to the keys they need -- e.g.,
    when a 'sudo' command or a system service needs to access encrypted
    files.  It's also inconsistent with the filesystem/VFS "view" of
    encrypted files which is global, so sometimes things randomly happen
    to work anyway due to caching.  Regardless, currently almost all
    fscrypt users actually do need global keys, so they're having to use
    workarounds that heavily abuse the session or user keyrings, e.g.
    Android and Chromium OS both use a systemwide "session keyring" and
    the 'fscrypt' tool links all user keyrings into root's user keyring.

(2) Currently there's no way to securely and efficiently remove a
    fscrypt key such that not only is the original key wiped, but also
    all files and directories protected by that key are "locked" and
    their per-file keys wiped.  Many users want this and are using
    'echo 2 > /proc/sys/vm/drop_caches' as a workaround, but this is
    root-only, and also is overkill so can be a performance disaster.

(3) The key derivation function (KDF) that fscrypt uses to derive
    per-file keys is nonstandard, inflexible, and has some weaknesses
    such as being reversible and not evenly distributing the entropy
    from the user-provided keys.

(4) fscrypt doesn't check that the correct key was supplied.  This can
    be a security vulnerability, since it allows malicious local users
    to associate the wrong key with files to which they have read-only
    access, causing other users' processes to read/write the wrong data.

Ultimately, the solutions to these problems all tie into each other.  By
adding a filesystem-level encryption keyring with ioctls to add/remove
keys to/from it, the keys are made usable filesystem-wide (solves
problem #1).  It also becomes easy to track the inodes that were
"unlocked" with each key, so they can be evicted when the key is removed
(solves problem #2).  Moreover, the filesystem-level keyring is a
natural place to store an HMAC transform keyed by each key, thus making
it easy and efficient to switch the KDF to HKDF (solves problem #3).

Finally, to check that the correct key was supplied, I use HKDF to
derive a cryptographically secure key_identifier for each key (solves
problem #4).  This in combination with key quotas and other careful
precautions also makes it safe to allow non-root users to add and remove
keys to/from the filesystem-level keyring.  Thus, all problems are
solved without having to restrict the fscrypt API to root only.

The patchset is organized as follows:

- Patches 1-8 add new ioctls FS_IOC_ADD_ENCRYPTION_KEY,
  FS_IOC_REMOVE_ENCRYPTION_KEY, and FS_IOC_GET_ENCRYPTION_KEY_STATUS.
  Adding a key logically "unlocks" all files on the filesystem that are
  protected by that key; removing a key "locks" them again.

- Patches 9-12 add support for v2 encryption policies.

- Patches 13-15 wire up the new ioctls to ext4, f2fs, and ubifs.

- Patch 16 updates the fscrypt documentation for all the changes.

This patchset applies to v5.3-rc1 with the pending fscrypt cleanup
patches applied (https://patchwork.kernel.org/patch/11057589/ and
https://patchwork.kernel.org/cover/11057583/).
You can also get it from git at:

	Repository:   https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git
	Branch:       fscrypt-key-mgmt-improvements-v7

I've written xfstests for the new APIs.  They test the APIs themselves
as well as verify the correctness of the ciphertext stored on-disk for
v2 encryption policies.  The tests can be found at:

	Repository:   https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/xfstests-dev.git
	Branch:       fscrypt-key-mgmt-improvements

The xfstests depend on new xfs_io commands which can be found at:

	Repository:   https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/xfsprogs-dev.git
	Branch:       fscrypt-key-mgmt-improvements

I've also made proof-of-concept changes to the 'fscrypt' userspace
program (https://github.com/google/fscrypt) to make it support v2
encryption policies.  You can find these changes in git at:

	Repository:   https://github.com/ebiggers/fscrypt.git
	Branch:       fscrypt-key-mgmt-improvements

To make the 'fscrypt' userspace program experimentally use v2 encryption
policies on new encrypted directories, add the following to
/etc/fscrypt.conf within the "options" section:

	"policy_version": "2"

Finally, it's also planned for Android and Chromium OS to switch to the
new ioctls and eventually to v2 encryption policies.  Work-in-progress,
proof-of-concept changes by Satya Tangirala for AOSP can be found at
https://android-review.googlesource.com/q/topic:fscrypt-key-mgmt-improvements

Changes v6 => v7:
    - Rebase onto v5.3-rc1 and the pending fscrypt cleanups.
    - Work around false positive compile-time buffer overflow check in
      copy_from_user() in fscrypt_ioctl_set_policy() when building an
      i386 kernel in a specific config with an old gcc version.
    - A few very minor cleanups.

Changes v5 => v6:
    - Change HKDF to use the specification-defined default salt rather
      than a custom fixed salt, and prepend the string "fscrypt" to
      'info' instead.  This is arguably needed to match how RFC 5869 and
      SP 800-56C are worded.  Both ways are secure in this context, so
      prefer the "boring" way that clearly matches the standards.
    - Rebase onto v5.2-rc1.
    - A few small cleanups.

Changes v4 => v5:
    - Simplify shrink_dcache_inode(), as suggested by Al Viro;
      also move it into fs/crypto/.
    - Fix a build error on some architectures by calling
      copy_from_user() rather than get_user() with a __u64 pointer.

Changes v3 => v4:
    - Introduce fscrypt_sb_free() to avoid an extra #ifdef.
    - Fix UBIFS's ->drop_inode().
    - Add 'version' to union fscrypt_policy and union fscrypt_context.

Changes v2 => v3:
    - Use ->drop_inode() to trigger the inode eviction during/after
      FS_IOC_REMOVE_ENCRYPTION_KEY, as suggested by Dave Chinner.
    - A few small cleanups.

v1 of this patchset was sent in October 2017 with title "fscrypt:
filesystem-level keyring and v2 policy support".  This revived version
follows the same basic design but incorporates numerous improvements,
such as splitting keyinfo.c into multiple files for much better
understandability, and introducing "per-mode" encryption keys to
implement the semantics of the DIRECT_KEY encryption policy flag.

Eric Biggers (16):
  fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h>
  fscrypt: use FSCRYPT_ prefix for uapi constants
  fscrypt: use FSCRYPT_* definitions, not FS_*
  fscrypt: add ->ci_inode to fscrypt_info
  fscrypt: refactor v1 policy key setup into keysetup_legacy.c
  fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl
  fscrypt: add an HKDF-SHA512 implementation
  fscrypt: v2 encryption policy support
  fscrypt: allow unprivileged users to add/remove keys for v2 policies
  fscrypt: require that key be added when setting a v2 encryption policy
  ext4: wire up new fscrypt ioctls
  f2fs: wire up new fscrypt ioctls
  ubifs: wire up new fscrypt ioctls
  fscrypt: document the new ioctls and policy version

 Documentation/filesystems/fscrypt.rst | 670 ++++++++++++++----
 MAINTAINERS                           |   1 +
 fs/crypto/Kconfig                     |   2 +
 fs/crypto/Makefile                    |  10 +-
 fs/crypto/crypto.c                    |  12 +-
 fs/crypto/fname.c                     |   5 +-
 fs/crypto/fscrypt_private.h           | 366 +++++++++-
 fs/crypto/hkdf.c                      | 181 +++++
 fs/crypto/keyinfo.c                   | 627 -----------------
 fs/crypto/keyring.c                   | 957 ++++++++++++++++++++++++++
 fs/crypto/keysetup.c                  | 569 +++++++++++++++
 fs/crypto/keysetup_legacy.c           | 340 +++++++++
 fs/crypto/policy.c                    | 428 +++++++++---
 fs/ext4/ioctl.c                       |  24 +
 fs/ext4/super.c                       |   3 +
 fs/f2fs/file.c                        |  46 ++
 fs/f2fs/super.c                       |   2 +
 fs/super.c                            |   2 +
 fs/ubifs/ioctl.c                      |  16 +
 fs/ubifs/super.c                      |  11 +
 include/linux/fs.h                    |   1 +
 include/linux/fscrypt.h               |  48 +-
 include/uapi/linux/fs.h               |  54 +-
 include/uapi/linux/fscrypt.h          | 164 +++++
 24 files changed, 3583 insertions(+), 956 deletions(-)
 create mode 100644 fs/crypto/hkdf.c
 delete mode 100644 fs/crypto/keyinfo.c
 create mode 100644 fs/crypto/keyring.c
 create mode 100644 fs/crypto/keysetup.c
 create mode 100644 fs/crypto/keysetup_legacy.c
 create mode 100644 include/uapi/linux/fscrypt.h

-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h>
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 15:08   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 02/16] fscrypt: use FSCRYPT_ prefix for uapi constants Eric Biggers
                   ` (14 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

More fscrypt definitions are being added, and we shouldn't use a
disproportionate amount of space in <linux/fs.h> for fscrypt stuff.
So move the fscrypt definitions to a new header <linux/fscrypt.h>.

For source compatibility with existing userspace programs, <linux/fs.h>
still includes the new header.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 MAINTAINERS                  |  1 +
 include/linux/fscrypt.h      |  1 +
 include/uapi/linux/fs.h      | 54 ++-----------------------------
 include/uapi/linux/fscrypt.h | 61 ++++++++++++++++++++++++++++++++++++
 4 files changed, 66 insertions(+), 51 deletions(-)
 create mode 100644 include/uapi/linux/fscrypt.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 783569e3c4b48..e7c473fb08163 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6598,6 +6598,7 @@ T:	git git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git
 S:	Supported
 F:	fs/crypto/
 F:	include/linux/fscrypt*.h
+F:	include/uapi/linux/fscrypt.h
 F:	Documentation/filesystems/fscrypt.rst
 
 FSI SUBSYSTEM
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index bd8f207a2fb68..81c0c754f8b21 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -16,6 +16,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <uapi/linux/fscrypt.h>
 
 #define FS_CRYPTO_BLOCK_SIZE		16
 
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 59c71fa8c553a..41bd84d25a980 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -13,6 +13,9 @@
 #include <linux/limits.h>
 #include <linux/ioctl.h>
 #include <linux/types.h>
+#ifndef __KERNEL__
+#include <linux/fscrypt.h>
+#endif
 
 /* Use of MS_* flags within the kernel is restricted to core mount(2) code. */
 #if !defined(__KERNEL__)
@@ -212,57 +215,6 @@ struct fsxattr {
 #define FS_IOC_GETFSLABEL		_IOR(0x94, 49, char[FSLABEL_MAX])
 #define FS_IOC_SETFSLABEL		_IOW(0x94, 50, char[FSLABEL_MAX])
 
-/*
- * File system encryption support
- */
-/* Policy provided via an ioctl on the topmost directory */
-#define FS_KEY_DESCRIPTOR_SIZE	8
-
-#define FS_POLICY_FLAGS_PAD_4		0x00
-#define FS_POLICY_FLAGS_PAD_8		0x01
-#define FS_POLICY_FLAGS_PAD_16		0x02
-#define FS_POLICY_FLAGS_PAD_32		0x03
-#define FS_POLICY_FLAGS_PAD_MASK	0x03
-#define FS_POLICY_FLAG_DIRECT_KEY	0x04	/* use master key directly */
-#define FS_POLICY_FLAGS_VALID		0x07
-
-/* Encryption algorithms */
-#define FS_ENCRYPTION_MODE_INVALID		0
-#define FS_ENCRYPTION_MODE_AES_256_XTS		1
-#define FS_ENCRYPTION_MODE_AES_256_GCM		2
-#define FS_ENCRYPTION_MODE_AES_256_CBC		3
-#define FS_ENCRYPTION_MODE_AES_256_CTS		4
-#define FS_ENCRYPTION_MODE_AES_128_CBC		5
-#define FS_ENCRYPTION_MODE_AES_128_CTS		6
-#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_ADIANTUM		9
-
-struct fscrypt_policy {
-	__u8 version;
-	__u8 contents_encryption_mode;
-	__u8 filenames_encryption_mode;
-	__u8 flags;
-	__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
-};
-
-#define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
-#define FS_IOC_GET_ENCRYPTION_PWSALT	_IOW('f', 20, __u8[16])
-#define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
-
-/* Parameters for passing an encryption key into the kernel keyring */
-#define FS_KEY_DESC_PREFIX		"fscrypt:"
-#define FS_KEY_DESC_PREFIX_SIZE		8
-
-/* Structure that userspace passes to the kernel keyring */
-#define FS_MAX_KEY_SIZE			64
-
-struct fscrypt_key {
-	__u32 mode;
-	__u8 raw[FS_MAX_KEY_SIZE];
-	__u32 size;
-};
-
 /*
  * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)
  *
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
new file mode 100644
index 0000000000000..26f6d2c19afd3
--- /dev/null
+++ b/include/uapi/linux/fscrypt.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * fscrypt user API
+ *
+ * These ioctls can be used on filesystems that support fscrypt.  See the
+ * "User API" section of Documentation/filesystems/fscrypt.rst.
+ */
+#ifndef _UAPI_LINUX_FSCRYPT_H
+#define _UAPI_LINUX_FSCRYPT_H
+
+#include <linux/types.h>
+
+#define FS_KEY_DESCRIPTOR_SIZE	8
+
+/* Encryption policy flags */
+#define FS_POLICY_FLAGS_PAD_4		0x00
+#define FS_POLICY_FLAGS_PAD_8		0x01
+#define FS_POLICY_FLAGS_PAD_16		0x02
+#define FS_POLICY_FLAGS_PAD_32		0x03
+#define FS_POLICY_FLAGS_PAD_MASK	0x03
+#define FS_POLICY_FLAG_DIRECT_KEY	0x04	/* use master key directly */
+#define FS_POLICY_FLAGS_VALID		0x07
+
+/* Encryption algorithms */
+#define FS_ENCRYPTION_MODE_INVALID		0
+#define FS_ENCRYPTION_MODE_AES_256_XTS		1
+#define FS_ENCRYPTION_MODE_AES_256_GCM		2
+#define FS_ENCRYPTION_MODE_AES_256_CBC		3
+#define FS_ENCRYPTION_MODE_AES_256_CTS		4
+#define FS_ENCRYPTION_MODE_AES_128_CBC		5
+#define FS_ENCRYPTION_MODE_AES_128_CTS		6
+#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7 /* Removed, do not use. */
+#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8 /* Removed, do not use. */
+#define FS_ENCRYPTION_MODE_ADIANTUM		9
+
+struct fscrypt_policy {
+	__u8 version;
+	__u8 contents_encryption_mode;
+	__u8 filenames_encryption_mode;
+	__u8 flags;
+	__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+};
+
+#define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
+#define FS_IOC_GET_ENCRYPTION_PWSALT	_IOW('f', 20, __u8[16])
+#define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
+
+/* Parameters for passing an encryption key into the kernel keyring */
+#define FS_KEY_DESC_PREFIX		"fscrypt:"
+#define FS_KEY_DESC_PREFIX_SIZE		8
+
+/* Structure that userspace passes to the kernel keyring */
+#define FS_MAX_KEY_SIZE			64
+
+struct fscrypt_key {
+	__u32 mode;
+	__u8 raw[FS_MAX_KEY_SIZE];
+	__u32 size;
+};
+
+#endif /* _UAPI_LINUX_FSCRYPT_H */
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 02/16] fscrypt: use FSCRYPT_ prefix for uapi constants
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h> Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 03/16] fscrypt: use FSCRYPT_* definitions, not FS_* Eric Biggers
                   ` (13 subsequent siblings)
  15 siblings, 0 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Prefix all filesystem encryption UAPI constants except the ioctl numbers
with "FSCRYPT_" rather than with "FS_".  This namespaces the constants
more appropriately and makes it clear that they are related specifically
to the filesystem encryption feature, and to the 'fscrypt_*' structures.
With some of the old names like "FS_POLICY_FLAGS_VALID", it was not
immediately clear that the constant had anything to do with encryption.

This is also useful because we'll be adding more encryption-related
constants, e.g. for the policy version, and we'd otherwise have to
choose whether to use unclear names like FS_POLICY_V1 or inconsistent
names like FS_ENCRYPTION_POLICY_V1.

For source compatibility with existing userspace programs, keep the old
names defined as aliases to the new names.

Finally, as long as new names are being defined anyway, I skipped
defining new names for the fscrypt mode numbers that aren't actually
used: INVALID (0), AES_256_GCM (2), AES_256_CBC (3), SPECK128_256_XTS
(7), and SPECK128_256_CTS (8).

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 Documentation/filesystems/fscrypt.rst | 36 +++++++--------
 include/uapi/linux/fscrypt.h          | 65 +++++++++++++++++----------
 2 files changed, 60 insertions(+), 41 deletions(-)

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 82efa41b0e6c0..2c4b6e56b81c5 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -225,9 +225,10 @@ a little endian number, except that:
   is encrypted with AES-256 where the AES-256 key is the SHA-256 hash
   of the file's data encryption key.
 
-- In the "direct key" configuration (FS_POLICY_FLAG_DIRECT_KEY set in
-  the fscrypt_policy), the file's nonce is also appended to the IV.
-  Currently this is only allowed with the Adiantum encryption mode.
+- In the "direct key" configuration (FSCRYPT_POLICY_FLAG_DIRECT_KEY
+  set in the fscrypt_policy), the file's nonce is also appended to the
+  IV.  Currently this is only allowed with the Adiantum encryption
+  mode.
 
 Filenames encryption
 --------------------
@@ -274,14 +275,14 @@ empty directory or verifies that a directory or regular file already
 has the specified encryption policy.  It takes in a pointer to a
 :c:type:`struct fscrypt_policy`, defined as follows::
 
-    #define FS_KEY_DESCRIPTOR_SIZE  8
+    #define FSCRYPT_KEY_DESCRIPTOR_SIZE  8
 
     struct fscrypt_policy {
             __u8 version;
             __u8 contents_encryption_mode;
             __u8 filenames_encryption_mode;
             __u8 flags;
-            __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+            __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
     };
 
 This structure must be initialized as follows:
@@ -290,18 +291,17 @@ This structure must be initialized as follows:
 
 - ``contents_encryption_mode`` and ``filenames_encryption_mode`` must
   be set to constants from ``<linux/fs.h>`` which identify the
-  encryption modes to use.  If unsure, use
-  FS_ENCRYPTION_MODE_AES_256_XTS (1) for ``contents_encryption_mode``
-  and FS_ENCRYPTION_MODE_AES_256_CTS (4) for
-  ``filenames_encryption_mode``.
+  encryption modes to use.  If unsure, use FSCRYPT_MODE_AES_256_XTS
+  (1) for ``contents_encryption_mode`` and FSCRYPT_MODE_AES_256_CTS
+  (4) for ``filenames_encryption_mode``.
 
 - ``flags`` must contain a value from ``<linux/fs.h>`` which
   identifies the amount of NUL-padding to use when encrypting
-  filenames.  If unsure, use FS_POLICY_FLAGS_PAD_32 (0x3).
-  In addition, if the chosen encryption modes are both
-  FS_ENCRYPTION_MODE_ADIANTUM, this can contain
-  FS_POLICY_FLAG_DIRECT_KEY to specify that the master key should be
-  used directly, without key derivation.
+  filenames.  If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3).  In
+  addition, if the chosen encryption modes are both
+  FSCRYPT_MODE_ADIANTUM, this can contain
+  FSCRYPT_POLICY_FLAG_DIRECT_KEY to specify that the master key should
+  be used directly, without key derivation.
 
 - ``master_key_descriptor`` specifies how to find the master key in
   the keyring; see `Adding keys`_.  It is up to userspace to choose a
@@ -401,11 +401,11 @@ followed by the 16-character lower case hex representation of the
 ``master_key_descriptor`` that was set in the encryption policy.  The
 key payload must conform to the following structure::
 
-    #define FS_MAX_KEY_SIZE 64
+    #define FSCRYPT_MAX_KEY_SIZE 64
 
     struct fscrypt_key {
             u32 mode;
-            u8 raw[FS_MAX_KEY_SIZE];
+            u8 raw[FSCRYPT_MAX_KEY_SIZE];
             u32 size;
     };
 
@@ -574,7 +574,7 @@ much confusion if an encryption policy were to be added to or removed
 from anything other than an empty directory.)  The struct is defined
 as follows::
 
-    #define FS_KEY_DESCRIPTOR_SIZE  8
+    #define FSCRYPT_KEY_DESCRIPTOR_SIZE  8
     #define FS_KEY_DERIVATION_NONCE_SIZE 16
 
     struct fscrypt_context {
@@ -582,7 +582,7 @@ as follows::
             u8 contents_encryption_mode;
             u8 filenames_encryption_mode;
             u8 flags;
-            u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+            u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
             u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
     };
 
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 26f6d2c19afd3..674b0452ef575 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -10,35 +10,30 @@
 
 #include <linux/types.h>
 
-#define FS_KEY_DESCRIPTOR_SIZE	8
+#define FSCRYPT_KEY_DESCRIPTOR_SIZE	8
 
 /* Encryption policy flags */
-#define FS_POLICY_FLAGS_PAD_4		0x00
-#define FS_POLICY_FLAGS_PAD_8		0x01
-#define FS_POLICY_FLAGS_PAD_16		0x02
-#define FS_POLICY_FLAGS_PAD_32		0x03
-#define FS_POLICY_FLAGS_PAD_MASK	0x03
-#define FS_POLICY_FLAG_DIRECT_KEY	0x04	/* use master key directly */
-#define FS_POLICY_FLAGS_VALID		0x07
+#define FSCRYPT_POLICY_FLAGS_PAD_4		0x00
+#define FSCRYPT_POLICY_FLAGS_PAD_8		0x01
+#define FSCRYPT_POLICY_FLAGS_PAD_16		0x02
+#define FSCRYPT_POLICY_FLAGS_PAD_32		0x03
+#define FSCRYPT_POLICY_FLAGS_PAD_MASK		0x03
+#define FSCRYPT_POLICY_FLAG_DIRECT_KEY		0x04	/* use master key directly */
+#define FSCRYPT_POLICY_FLAGS_VALID		0x07
 
 /* Encryption algorithms */
-#define FS_ENCRYPTION_MODE_INVALID		0
-#define FS_ENCRYPTION_MODE_AES_256_XTS		1
-#define FS_ENCRYPTION_MODE_AES_256_GCM		2
-#define FS_ENCRYPTION_MODE_AES_256_CBC		3
-#define FS_ENCRYPTION_MODE_AES_256_CTS		4
-#define FS_ENCRYPTION_MODE_AES_128_CBC		5
-#define FS_ENCRYPTION_MODE_AES_128_CTS		6
-#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_ADIANTUM		9
+#define FSCRYPT_MODE_AES_256_XTS		1
+#define FSCRYPT_MODE_AES_256_CTS		4
+#define FSCRYPT_MODE_AES_128_CBC		5
+#define FSCRYPT_MODE_AES_128_CTS		6
+#define FSCRYPT_MODE_ADIANTUM			9
 
 struct fscrypt_policy {
 	__u8 version;
 	__u8 contents_encryption_mode;
 	__u8 filenames_encryption_mode;
 	__u8 flags;
-	__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+	__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 };
 
 #define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
@@ -46,16 +41,40 @@ struct fscrypt_policy {
 #define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
 
 /* Parameters for passing an encryption key into the kernel keyring */
-#define FS_KEY_DESC_PREFIX		"fscrypt:"
-#define FS_KEY_DESC_PREFIX_SIZE		8
+#define FSCRYPT_KEY_DESC_PREFIX		"fscrypt:"
+#define FSCRYPT_KEY_DESC_PREFIX_SIZE		8
 
 /* Structure that userspace passes to the kernel keyring */
-#define FS_MAX_KEY_SIZE			64
+#define FSCRYPT_MAX_KEY_SIZE			64
 
 struct fscrypt_key {
 	__u32 mode;
-	__u8 raw[FS_MAX_KEY_SIZE];
+	__u8 raw[FSCRYPT_MAX_KEY_SIZE];
 	__u32 size;
 };
+/**********************************************************************/
+
+/* old names; don't add anything new here! */
+#define FS_KEY_DESCRIPTOR_SIZE		FSCRYPT_KEY_DESCRIPTOR_SIZE
+#define FS_POLICY_FLAGS_PAD_4		FSCRYPT_POLICY_FLAGS_PAD_4
+#define FS_POLICY_FLAGS_PAD_8		FSCRYPT_POLICY_FLAGS_PAD_8
+#define FS_POLICY_FLAGS_PAD_16		FSCRYPT_POLICY_FLAGS_PAD_16
+#define FS_POLICY_FLAGS_PAD_32		FSCRYPT_POLICY_FLAGS_PAD_32
+#define FS_POLICY_FLAGS_PAD_MASK	FSCRYPT_POLICY_FLAGS_PAD_MASK
+#define FS_POLICY_FLAG_DIRECT_KEY	FSCRYPT_POLICY_FLAG_DIRECT_KEY
+#define FS_POLICY_FLAGS_VALID		FSCRYPT_POLICY_FLAGS_VALID
+#define FS_ENCRYPTION_MODE_INVALID	0	/* never used */
+#define FS_ENCRYPTION_MODE_AES_256_XTS	FSCRYPT_MODE_AES_256_XTS
+#define FS_ENCRYPTION_MODE_AES_256_GCM	2	/* never used */
+#define FS_ENCRYPTION_MODE_AES_256_CBC	3	/* never used */
+#define FS_ENCRYPTION_MODE_AES_256_CTS	FSCRYPT_MODE_AES_256_CTS
+#define FS_ENCRYPTION_MODE_AES_128_CBC	FSCRYPT_MODE_AES_128_CBC
+#define FS_ENCRYPTION_MODE_AES_128_CTS	FSCRYPT_MODE_AES_128_CTS
+#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7	/* removed */
+#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8	/* removed */
+#define FS_ENCRYPTION_MODE_ADIANTUM	FSCRYPT_MODE_ADIANTUM
+#define FS_KEY_DESC_PREFIX		FSCRYPT_KEY_DESC_PREFIX
+#define FS_KEY_DESC_PREFIX_SIZE		FSCRYPT_KEY_DESC_PREFIX_SIZE
+#define FS_MAX_KEY_SIZE			FSCRYPT_MAX_KEY_SIZE
 
 #endif /* _UAPI_LINUX_FSCRYPT_H */
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 03/16] fscrypt: use FSCRYPT_* definitions, not FS_*
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h> Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 02/16] fscrypt: use FSCRYPT_ prefix for uapi constants Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 04/16] fscrypt: add ->ci_inode to fscrypt_info Eric Biggers
                   ` (12 subsequent siblings)
  15 siblings, 0 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Update fs/crypto/ to use the new names for the UAPI constants rather
than the old names, then make the old definitions conditional on
!__KERNEL__.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/crypto.c           |  2 +-
 fs/crypto/fname.c            |  2 +-
 fs/crypto/fscrypt_private.h  | 16 +++++------
 fs/crypto/keyinfo.c          | 53 ++++++++++++++++++------------------
 fs/crypto/policy.c           | 14 +++++-----
 include/uapi/linux/fscrypt.h |  2 ++
 6 files changed, 46 insertions(+), 43 deletions(-)

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index 3e4624cfe4b54..7502c1f0ede9e 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -141,7 +141,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 	memset(iv, 0, ci->ci_mode->ivsize);
 	iv->lblk_num = cpu_to_le64(lblk_num);
 
-	if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
+	if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
 		memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 
 	if (ci->ci_essiv_tfm != NULL)
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 5cab3bb2d1fc0..f4977d44d69b8 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -182,7 +182,7 @@ bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
 				  u32 max_len, u32 *encrypted_len_ret)
 {
 	int padding = 4 << (inode->i_crypt_info->ci_flags &
-			    FS_POLICY_FLAGS_PAD_MASK);
+			    FSCRYPT_POLICY_FLAGS_PAD_MASK);
 	u32 encrypted_len;
 
 	if (orig_len > max_len)
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 4d715708c6e1f..fae411b2f78dc 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -34,7 +34,7 @@ struct fscrypt_context {
 	u8 contents_encryption_mode;
 	u8 filenames_encryption_mode;
 	u8 flags;
-	u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+	u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 	u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
 } __packed;
 
@@ -84,7 +84,7 @@ struct fscrypt_info {
 	u8 ci_data_mode;
 	u8 ci_filename_mode;
 	u8 ci_flags;
-	u8 ci_master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+	u8 ci_master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 	u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
 };
 
@@ -98,16 +98,16 @@ typedef enum {
 static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
 					   u32 filenames_mode)
 {
-	if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC &&
-	    filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS)
+	if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
+	    filenames_mode == FSCRYPT_MODE_AES_128_CTS)
 		return true;
 
-	if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS &&
-	    filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
+	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
+	    filenames_mode == FSCRYPT_MODE_AES_256_CTS)
 		return true;
 
-	if (contents_mode == FS_ENCRYPTION_MODE_ADIANTUM &&
-	    filenames_mode == FS_ENCRYPTION_MODE_ADIANTUM)
+	if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
+	    filenames_mode == FSCRYPT_MODE_ADIANTUM)
 		return true;
 
 	return false;
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 2129943002335..22345ddede119 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -20,7 +20,7 @@
 
 static struct crypto_shash *essiv_hash_tfm;
 
-/* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */
+/* Table of keys referenced by DIRECT_KEY policies */
 static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
 static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
 
@@ -77,7 +77,7 @@ static int derive_key_aes(const u8 *master_key,
  */
 static struct key *
 find_and_lock_process_key(const char *prefix,
-			  const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
+			  const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE],
 			  unsigned int min_keysize,
 			  const struct fscrypt_key **payload_ret)
 {
@@ -87,7 +87,7 @@ find_and_lock_process_key(const char *prefix,
 	const struct fscrypt_key *payload;
 
 	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
-				FS_KEY_DESCRIPTOR_SIZE, descriptor);
+				FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor);
 	if (!description)
 		return ERR_PTR(-ENOMEM);
 
@@ -105,7 +105,7 @@ find_and_lock_process_key(const char *prefix,
 	payload = (const struct fscrypt_key *)ukp->data;
 
 	if (ukp->datalen != sizeof(struct fscrypt_key) ||
-	    payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) {
+	    payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) {
 		fscrypt_warn(NULL,
 			     "key with description '%s' has invalid payload",
 			     key->description);
@@ -129,32 +129,32 @@ find_and_lock_process_key(const char *prefix,
 }
 
 static struct fscrypt_mode available_modes[] = {
-	[FS_ENCRYPTION_MODE_AES_256_XTS] = {
+	[FSCRYPT_MODE_AES_256_XTS] = {
 		.friendly_name = "AES-256-XTS",
 		.cipher_str = "xts(aes)",
 		.keysize = 64,
 		.ivsize = 16,
 	},
-	[FS_ENCRYPTION_MODE_AES_256_CTS] = {
+	[FSCRYPT_MODE_AES_256_CTS] = {
 		.friendly_name = "AES-256-CTS-CBC",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 32,
 		.ivsize = 16,
 	},
-	[FS_ENCRYPTION_MODE_AES_128_CBC] = {
+	[FSCRYPT_MODE_AES_128_CBC] = {
 		.friendly_name = "AES-128-CBC",
 		.cipher_str = "cbc(aes)",
 		.keysize = 16,
 		.ivsize = 16,
 		.needs_essiv = true,
 	},
-	[FS_ENCRYPTION_MODE_AES_128_CTS] = {
+	[FSCRYPT_MODE_AES_128_CTS] = {
 		.friendly_name = "AES-128-CTS-CBC",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 16,
 		.ivsize = 16,
 	},
-	[FS_ENCRYPTION_MODE_ADIANTUM] = {
+	[FSCRYPT_MODE_ADIANTUM] = {
 		.friendly_name = "Adiantum",
 		.cipher_str = "adiantum(xchacha12,aes)",
 		.keysize = 32,
@@ -192,7 +192,7 @@ static int find_and_derive_key(const struct inode *inode,
 	const struct fscrypt_key *payload;
 	int err;
 
-	key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
+	key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX,
 					ctx->master_key_descriptor,
 					mode->keysize, &payload);
 	if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
@@ -203,7 +203,7 @@ static int find_and_derive_key(const struct inode *inode,
 	if (IS_ERR(key))
 		return PTR_ERR(key);
 
-	if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) {
+	if (ctx->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
 		if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
 			fscrypt_warn(inode,
 				     "Direct key mode not allowed with %s",
@@ -272,14 +272,14 @@ allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
 	return ERR_PTR(err);
 }
 
-/* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */
+/* Master key referenced by DIRECT_KEY policy */
 struct fscrypt_master_key {
 	struct hlist_node mk_node;
 	refcount_t mk_refcount;
 	const struct fscrypt_mode *mk_mode;
 	struct crypto_skcipher *mk_ctfm;
-	u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE];
-	u8 mk_raw[FS_MAX_KEY_SIZE];
+	u8 mk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+	u8 mk_raw[FSCRYPT_MAX_KEY_SIZE];
 };
 
 static void free_master_key(struct fscrypt_master_key *mk)
@@ -320,13 +320,13 @@ find_or_insert_master_key(struct fscrypt_master_key *to_insert,
 	 * raw key, and use crypto_memneq() when comparing raw keys.
 	 */
 
-	BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE);
+	BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE);
 	memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
 
 	spin_lock(&fscrypt_master_keys_lock);
 	hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) {
 		if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor,
-			   FS_KEY_DESCRIPTOR_SIZE) != 0)
+			   FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0)
 			continue;
 		if (mode != mk->mk_mode)
 			continue;
@@ -370,7 +370,7 @@ fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
 		goto err_free_mk;
 	}
 	memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
-	       FS_KEY_DESCRIPTOR_SIZE);
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
 	memcpy(mk->mk_raw, raw_key, mode->keysize);
 
 	return find_or_insert_master_key(mk, raw_key, mode, ci);
@@ -448,8 +448,8 @@ static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
 
 /*
  * Given the encryption mode and key (normally the derived key, but for
- * FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's
- * symmetric cipher transform object(s).
+ * DIRECT_KEY mode it's the master key), set up the inode's symmetric cipher
+ * transform object(s).
  */
 static int setup_crypto_transform(struct fscrypt_info *ci,
 				  struct fscrypt_mode *mode,
@@ -459,7 +459,7 @@ static int setup_crypto_transform(struct fscrypt_info *ci,
 	struct crypto_skcipher *ctfm;
 	int err;
 
-	if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) {
+	if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
 		mk = fscrypt_get_master_key(ci, mode, raw_key, inode);
 		if (IS_ERR(mk))
 			return PTR_ERR(mk);
@@ -476,7 +476,7 @@ static int setup_crypto_transform(struct fscrypt_info *ci,
 	if (mode->needs_essiv) {
 		/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
 		WARN_ON(mode->ivsize != AES_BLOCK_SIZE);
-		WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY);
+		WARN_ON(ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
 
 		err = init_essiv_generator(ci, raw_key, mode->keysize);
 		if (err) {
@@ -530,9 +530,10 @@ int fscrypt_get_encryption_info(struct inode *inode)
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));
 		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-		ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
-		ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
-		memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
+		ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
+		ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
+		memset(ctx.master_key_descriptor, 0x42,
+		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
 	} else if (res != sizeof(ctx)) {
 		fscrypt_warn(inode,
 			     "Unknown encryption context size (%d bytes)", res);
@@ -545,7 +546,7 @@ int fscrypt_get_encryption_info(struct inode *inode)
 		return -EINVAL;
 	}
 
-	if (ctx.flags & ~FS_POLICY_FLAGS_VALID) {
+	if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
 		fscrypt_warn(inode, "Unknown encryption context flags (0x%02x)",
 			     ctx.flags);
 		return -EINVAL;
@@ -559,7 +560,7 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 	memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
-	       FS_KEY_DESCRIPTOR_SIZE);
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
 	memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 
 	mode = select_encryption_mode(crypt_info, inode);
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 4941fe8471cef..da7ae9c8b4ad0 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -22,7 +22,7 @@ static bool is_encryption_context_consistent_with_policy(
 				const struct fscrypt_policy *policy)
 {
 	return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
-		      FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+		      FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
 		(ctx->flags == policy->flags) &&
 		(ctx->contents_encryption_mode ==
 		 policy->contents_encryption_mode) &&
@@ -37,13 +37,13 @@ static int create_encryption_context_from_policy(struct inode *inode,
 
 	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
 	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
-					FS_KEY_DESCRIPTOR_SIZE);
+					FSCRYPT_KEY_DESCRIPTOR_SIZE);
 
 	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
 				     policy->filenames_encryption_mode))
 		return -EINVAL;
 
-	if (policy->flags & ~FS_POLICY_FLAGS_VALID)
+	if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID)
 		return -EINVAL;
 
 	ctx.contents_encryption_mode = policy->contents_encryption_mode;
@@ -128,7 +128,7 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 	policy.filenames_encryption_mode = ctx.filenames_encryption_mode;
 	policy.flags = ctx.flags;
 	memcpy(policy.master_key_descriptor, ctx.master_key_descriptor,
-				FS_KEY_DESCRIPTOR_SIZE);
+				FSCRYPT_KEY_DESCRIPTOR_SIZE);
 
 	if (copy_to_user(arg, &policy, sizeof(policy)))
 		return -EFAULT;
@@ -202,7 +202,7 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 	if (parent_ci && child_ci) {
 		return memcmp(parent_ci->ci_master_key_descriptor,
 			      child_ci->ci_master_key_descriptor,
-			      FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+			      FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
 			(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
 			(parent_ci->ci_filename_mode ==
 			 child_ci->ci_filename_mode) &&
@@ -219,7 +219,7 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 
 	return memcmp(parent_ctx.master_key_descriptor,
 		      child_ctx.master_key_descriptor,
-		      FS_KEY_DESCRIPTOR_SIZE) == 0 &&
+		      FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
 		(parent_ctx.contents_encryption_mode ==
 		 child_ctx.contents_encryption_mode) &&
 		(parent_ctx.filenames_encryption_mode ==
@@ -257,7 +257,7 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child,
 	ctx.filenames_encryption_mode = ci->ci_filename_mode;
 	ctx.flags = ci->ci_flags;
 	memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor,
-	       FS_KEY_DESCRIPTOR_SIZE);
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
 	get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 	BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
 	res = parent->i_sb->s_cop->set_context(child, &ctx,
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 674b0452ef575..29a945d165def 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -55,6 +55,7 @@ struct fscrypt_key {
 /**********************************************************************/
 
 /* old names; don't add anything new here! */
+#ifndef __KERNEL__
 #define FS_KEY_DESCRIPTOR_SIZE		FSCRYPT_KEY_DESCRIPTOR_SIZE
 #define FS_POLICY_FLAGS_PAD_4		FSCRYPT_POLICY_FLAGS_PAD_4
 #define FS_POLICY_FLAGS_PAD_8		FSCRYPT_POLICY_FLAGS_PAD_8
@@ -76,5 +77,6 @@ struct fscrypt_key {
 #define FS_KEY_DESC_PREFIX		FSCRYPT_KEY_DESC_PREFIX
 #define FS_KEY_DESC_PREFIX_SIZE		FSCRYPT_KEY_DESC_PREFIX_SIZE
 #define FS_MAX_KEY_SIZE			FSCRYPT_MAX_KEY_SIZE
+#endif /* !__KERNEL__ */
 
 #endif /* _UAPI_LINUX_FSCRYPT_H */
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 04/16] fscrypt: add ->ci_inode to fscrypt_info
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (2 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 03/16] fscrypt: use FSCRYPT_* definitions, not FS_* Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 15:09   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c Eric Biggers
                   ` (11 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Add an inode back-pointer to 'struct fscrypt_info', such that
inode->i_crypt_info->ci_inode == inode.

This will be useful for:

1. Evicting the inodes when a fscrypt key is removed, since we'll track
   the inodes using a given key by linking their fscrypt_infos together,
   rather than the inodes directly.  This avoids bloating 'struct inode'
   with a new list_head.

2. Simplifying the per-file key setup, since the inode pointer won't
   have to be passed around everywhere just in case something goes wrong
   and it's needed for fscrypt_warn().

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/fscrypt_private.h | 3 +++
 fs/crypto/keyinfo.c         | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index fae411b2f78dc..d345a7d28df8c 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -73,6 +73,9 @@ struct fscrypt_info {
 	 */
 	struct fscrypt_mode *ci_mode;
 
+	/* Back-pointer to the inode */
+	struct inode *ci_inode;
+
 	/*
 	 * If non-NULL, then this inode uses a master key directly rather than a
 	 * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm.
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 22345ddede119..2d45a86f09db2 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -556,6 +556,8 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	if (!crypt_info)
 		return -ENOMEM;
 
+	crypt_info->ci_inode = inode;
+
 	crypt_info->ci_flags = ctx.flags;
 	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (3 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 04/16] fscrypt: add ->ci_inode to fscrypt_info Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 15:40   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Eric Biggers
                   ` (10 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

In preparation for introducing v2 encryption policies which will find
and derive encryption keys differently from the current v1 encryption
policies, refactor the v1 policy-specific key setup code from keyinfo.c
into keysetup_legacy.c.  Then rename keyinfo.c to keysetup.c.

Note: the code moved into keysetup_legacy.c includes the table of master
keys referenced by v1 DIRECT_KEY policies.  I've chosen to keep this
table as-is rather than trying to replace it with using the
filesystem-level keyring, since the latter would add more complexity
than it would save especially given the requirement to continue to
support the keys actually being provided in a process-subscribed
keyring.  However, to distinguish the structures in this table from the
structures that will go in the filesystem-level keyring, I renamed them
from 'struct fscrypt_master_key' to 'struct fscrypt_direct_key'.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/Makefile          |   8 +-
 fs/crypto/fscrypt_private.h |  37 ++-
 fs/crypto/keyinfo.c         | 630 ------------------------------------
 fs/crypto/keysetup.c        | 346 ++++++++++++++++++++
 fs/crypto/keysetup_legacy.c | 338 +++++++++++++++++++
 include/linux/fscrypt.h     |   4 +-
 6 files changed, 722 insertions(+), 641 deletions(-)
 delete mode 100644 fs/crypto/keyinfo.c
 create mode 100644 fs/crypto/keysetup.c
 create mode 100644 fs/crypto/keysetup_legacy.c

diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile
index 4f0df5e682e49..3bf9939c8ce17 100644
--- a/fs/crypto/Makefile
+++ b/fs/crypto/Makefile
@@ -1,5 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_FS_ENCRYPTION)	+= fscrypto.o
 
-fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o
+fscrypto-y := crypto.o \
+	      fname.o \
+	      hooks.o \
+	      keysetup.o \
+	      keysetup_legacy.o \
+	      policy.o
+
 fscrypto-$(CONFIG_BLOCK) += bio.o
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index d345a7d28df8c..a624d48b77354 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -4,9 +4,8 @@
  *
  * Copyright (C) 2015, Google, Inc.
  *
- * This contains encryption key functions.
- *
- * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
+ * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
+ * Heavily modified since then.
  */
 
 #ifndef _FSCRYPT_PRIVATE_H
@@ -77,11 +76,10 @@ struct fscrypt_info {
 	struct inode *ci_inode;
 
 	/*
-	 * If non-NULL, then this inode uses a master key directly rather than a
-	 * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm.
-	 * Otherwise, this inode uses a derived key.
+	 * If non-NULL, then encryption is done using the master key directly
+	 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
 	 */
-	struct fscrypt_master_key *ci_master_key;
+	struct fscrypt_direct_key *ci_direct_key;
 
 	/* fields from the fscrypt_context */
 	u8 ci_data_mode;
@@ -158,7 +156,7 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
 					 u32 orig_len, u32 max_len,
 					 u32 *encrypted_len_ret);
 
-/* keyinfo.c */
+/* keysetup.c */
 
 struct fscrypt_mode {
 	const char *friendly_name;
@@ -169,4 +167,27 @@ struct fscrypt_mode {
 	bool needs_essiv;
 };
 
+static inline bool
+fscrypt_mode_supports_direct_key(const struct fscrypt_mode *mode)
+{
+	return mode->ivsize >= offsetofend(union fscrypt_iv, nonce);
+}
+
+extern struct crypto_skcipher *
+fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
+			  const struct inode *inode);
+
+extern int fscrypt_set_derived_key(struct fscrypt_info *ci,
+				   const u8 *derived_key);
+
+/* keysetup_legacy.c */
+
+extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
+
+extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
+				     const u8 *raw_master_key);
+
+extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
+					struct fscrypt_info *ci);
+
 #endif /* _FSCRYPT_PRIVATE_H */
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
deleted file mode 100644
index 2d45a86f09db2..0000000000000
--- a/fs/crypto/keyinfo.c
+++ /dev/null
@@ -1,630 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * key management facility for FS encryption support.
- *
- * Copyright (C) 2015, Google, Inc.
- *
- * This contains encryption key functions.
- *
- * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
- */
-
-#include <keys/user-type.h>
-#include <linux/hashtable.h>
-#include <linux/scatterlist.h>
-#include <crypto/aes.h>
-#include <crypto/algapi.h>
-#include <crypto/sha.h>
-#include <crypto/skcipher.h>
-#include "fscrypt_private.h"
-
-static struct crypto_shash *essiv_hash_tfm;
-
-/* Table of keys referenced by DIRECT_KEY policies */
-static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
-static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
-
-/*
- * Key derivation function.  This generates the derived key by encrypting the
- * master key with AES-128-ECB using the inode's nonce as the AES key.
- *
- * The master key must be at least as long as the derived key.  If the master
- * key is longer, then only the first 'derived_keysize' bytes are used.
- */
-static int derive_key_aes(const u8 *master_key,
-			  const struct fscrypt_context *ctx,
-			  u8 *derived_key, unsigned int derived_keysize)
-{
-	int res = 0;
-	struct skcipher_request *req = NULL;
-	DECLARE_CRYPTO_WAIT(wait);
-	struct scatterlist src_sg, dst_sg;
-	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
-
-	if (IS_ERR(tfm)) {
-		res = PTR_ERR(tfm);
-		tfm = NULL;
-		goto out;
-	}
-	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
-	req = skcipher_request_alloc(tfm, GFP_NOFS);
-	if (!req) {
-		res = -ENOMEM;
-		goto out;
-	}
-	skcipher_request_set_callback(req,
-			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
-			crypto_req_done, &wait);
-	res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce));
-	if (res < 0)
-		goto out;
-
-	sg_init_one(&src_sg, master_key, derived_keysize);
-	sg_init_one(&dst_sg, derived_key, derived_keysize);
-	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
-				   NULL);
-	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
-out:
-	skcipher_request_free(req);
-	crypto_free_skcipher(tfm);
-	return res;
-}
-
-/*
- * Search the current task's subscribed keyrings for a "logon" key with
- * description prefix:descriptor, and if found acquire a read lock on it and
- * return a pointer to its validated payload in *payload_ret.
- */
-static struct key *
-find_and_lock_process_key(const char *prefix,
-			  const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE],
-			  unsigned int min_keysize,
-			  const struct fscrypt_key **payload_ret)
-{
-	char *description;
-	struct key *key;
-	const struct user_key_payload *ukp;
-	const struct fscrypt_key *payload;
-
-	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
-				FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor);
-	if (!description)
-		return ERR_PTR(-ENOMEM);
-
-	key = request_key(&key_type_logon, description, NULL);
-	kfree(description);
-	if (IS_ERR(key))
-		return key;
-
-	down_read(&key->sem);
-	ukp = user_key_payload_locked(key);
-
-	if (!ukp) /* was the key revoked before we acquired its semaphore? */
-		goto invalid;
-
-	payload = (const struct fscrypt_key *)ukp->data;
-
-	if (ukp->datalen != sizeof(struct fscrypt_key) ||
-	    payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) {
-		fscrypt_warn(NULL,
-			     "key with description '%s' has invalid payload",
-			     key->description);
-		goto invalid;
-	}
-
-	if (payload->size < min_keysize) {
-		fscrypt_warn(NULL,
-			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
-			     key->description, payload->size, min_keysize);
-		goto invalid;
-	}
-
-	*payload_ret = payload;
-	return key;
-
-invalid:
-	up_read(&key->sem);
-	key_put(key);
-	return ERR_PTR(-ENOKEY);
-}
-
-static struct fscrypt_mode available_modes[] = {
-	[FSCRYPT_MODE_AES_256_XTS] = {
-		.friendly_name = "AES-256-XTS",
-		.cipher_str = "xts(aes)",
-		.keysize = 64,
-		.ivsize = 16,
-	},
-	[FSCRYPT_MODE_AES_256_CTS] = {
-		.friendly_name = "AES-256-CTS-CBC",
-		.cipher_str = "cts(cbc(aes))",
-		.keysize = 32,
-		.ivsize = 16,
-	},
-	[FSCRYPT_MODE_AES_128_CBC] = {
-		.friendly_name = "AES-128-CBC",
-		.cipher_str = "cbc(aes)",
-		.keysize = 16,
-		.ivsize = 16,
-		.needs_essiv = true,
-	},
-	[FSCRYPT_MODE_AES_128_CTS] = {
-		.friendly_name = "AES-128-CTS-CBC",
-		.cipher_str = "cts(cbc(aes))",
-		.keysize = 16,
-		.ivsize = 16,
-	},
-	[FSCRYPT_MODE_ADIANTUM] = {
-		.friendly_name = "Adiantum",
-		.cipher_str = "adiantum(xchacha12,aes)",
-		.keysize = 32,
-		.ivsize = 32,
-	},
-};
-
-static struct fscrypt_mode *
-select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
-{
-	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
-		fscrypt_warn(inode,
-			     "Unsupported encryption modes (contents mode %d, filenames mode %d)",
-			     ci->ci_data_mode, ci->ci_filename_mode);
-		return ERR_PTR(-EINVAL);
-	}
-
-	if (S_ISREG(inode->i_mode))
-		return &available_modes[ci->ci_data_mode];
-
-	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
-		return &available_modes[ci->ci_filename_mode];
-
-	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
-		  inode->i_ino, (inode->i_mode & S_IFMT));
-	return ERR_PTR(-EINVAL);
-}
-
-/* Find the master key, then derive the inode's actual encryption key */
-static int find_and_derive_key(const struct inode *inode,
-			       const struct fscrypt_context *ctx,
-			       u8 *derived_key, const struct fscrypt_mode *mode)
-{
-	struct key *key;
-	const struct fscrypt_key *payload;
-	int err;
-
-	key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX,
-					ctx->master_key_descriptor,
-					mode->keysize, &payload);
-	if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
-		key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
-						ctx->master_key_descriptor,
-						mode->keysize, &payload);
-	}
-	if (IS_ERR(key))
-		return PTR_ERR(key);
-
-	if (ctx->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
-		if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
-			fscrypt_warn(inode,
-				     "Direct key mode not allowed with %s",
-				     mode->friendly_name);
-			err = -EINVAL;
-		} else if (ctx->contents_encryption_mode !=
-			   ctx->filenames_encryption_mode) {
-			fscrypt_warn(inode,
-				     "Direct key mode not allowed with different contents and filenames modes");
-			err = -EINVAL;
-		} else {
-			memcpy(derived_key, payload->raw, mode->keysize);
-			err = 0;
-		}
-	} else {
-		err = derive_key_aes(payload->raw, ctx, derived_key,
-				     mode->keysize);
-	}
-	up_read(&key->sem);
-	key_put(key);
-	return err;
-}
-
-/* Allocate and key a symmetric cipher object for the given encryption mode */
-static struct crypto_skcipher *
-allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
-			   const struct inode *inode)
-{
-	struct crypto_skcipher *tfm;
-	int err;
-
-	tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
-	if (IS_ERR(tfm)) {
-		if (PTR_ERR(tfm) == -ENOENT) {
-			fscrypt_warn(inode,
-				     "Missing crypto API support for %s (API name: \"%s\")",
-				     mode->friendly_name, mode->cipher_str);
-			return ERR_PTR(-ENOPKG);
-		}
-		fscrypt_err(inode, "Error allocating '%s' transform: %ld",
-			    mode->cipher_str, PTR_ERR(tfm));
-		return tfm;
-	}
-	if (unlikely(!mode->logged_impl_name)) {
-		/*
-		 * fscrypt performance can vary greatly depending on which
-		 * crypto algorithm implementation is used.  Help people debug
-		 * performance problems by logging the ->cra_driver_name the
-		 * first time a mode is used.  Note that multiple threads can
-		 * race here, but it doesn't really matter.
-		 */
-		mode->logged_impl_name = true;
-		pr_info("fscrypt: %s using implementation \"%s\"\n",
-			mode->friendly_name,
-			crypto_skcipher_alg(tfm)->base.cra_driver_name);
-	}
-	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
-	err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
-	if (err)
-		goto err_free_tfm;
-
-	return tfm;
-
-err_free_tfm:
-	crypto_free_skcipher(tfm);
-	return ERR_PTR(err);
-}
-
-/* Master key referenced by DIRECT_KEY policy */
-struct fscrypt_master_key {
-	struct hlist_node mk_node;
-	refcount_t mk_refcount;
-	const struct fscrypt_mode *mk_mode;
-	struct crypto_skcipher *mk_ctfm;
-	u8 mk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
-	u8 mk_raw[FSCRYPT_MAX_KEY_SIZE];
-};
-
-static void free_master_key(struct fscrypt_master_key *mk)
-{
-	if (mk) {
-		crypto_free_skcipher(mk->mk_ctfm);
-		kzfree(mk);
-	}
-}
-
-static void put_master_key(struct fscrypt_master_key *mk)
-{
-	if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock))
-		return;
-	hash_del(&mk->mk_node);
-	spin_unlock(&fscrypt_master_keys_lock);
-
-	free_master_key(mk);
-}
-
-/*
- * Find/insert the given master key into the fscrypt_master_keys table.  If
- * found, it is returned with elevated refcount, and 'to_insert' is freed if
- * non-NULL.  If not found, 'to_insert' is inserted and returned if it's
- * non-NULL; otherwise NULL is returned.
- */
-static struct fscrypt_master_key *
-find_or_insert_master_key(struct fscrypt_master_key *to_insert,
-			  const u8 *raw_key, const struct fscrypt_mode *mode,
-			  const struct fscrypt_info *ci)
-{
-	unsigned long hash_key;
-	struct fscrypt_master_key *mk;
-
-	/*
-	 * Careful: to avoid potentially leaking secret key bytes via timing
-	 * information, we must key the hash table by descriptor rather than by
-	 * raw key, and use crypto_memneq() when comparing raw keys.
-	 */
-
-	BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
-
-	spin_lock(&fscrypt_master_keys_lock);
-	hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) {
-		if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor,
-			   FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0)
-			continue;
-		if (mode != mk->mk_mode)
-			continue;
-		if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize))
-			continue;
-		/* using existing tfm with same (descriptor, mode, raw_key) */
-		refcount_inc(&mk->mk_refcount);
-		spin_unlock(&fscrypt_master_keys_lock);
-		free_master_key(to_insert);
-		return mk;
-	}
-	if (to_insert)
-		hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key);
-	spin_unlock(&fscrypt_master_keys_lock);
-	return to_insert;
-}
-
-/* Prepare to encrypt directly using the master key in the given mode */
-static struct fscrypt_master_key *
-fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
-		       const u8 *raw_key, const struct inode *inode)
-{
-	struct fscrypt_master_key *mk;
-	int err;
-
-	/* Is there already a tfm for this key? */
-	mk = find_or_insert_master_key(NULL, raw_key, mode, ci);
-	if (mk)
-		return mk;
-
-	/* Nope, allocate one. */
-	mk = kzalloc(sizeof(*mk), GFP_NOFS);
-	if (!mk)
-		return ERR_PTR(-ENOMEM);
-	refcount_set(&mk->mk_refcount, 1);
-	mk->mk_mode = mode;
-	mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
-	if (IS_ERR(mk->mk_ctfm)) {
-		err = PTR_ERR(mk->mk_ctfm);
-		mk->mk_ctfm = NULL;
-		goto err_free_mk;
-	}
-	memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
-	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	memcpy(mk->mk_raw, raw_key, mode->keysize);
-
-	return find_or_insert_master_key(mk, raw_key, mode, ci);
-
-err_free_mk:
-	free_master_key(mk);
-	return ERR_PTR(err);
-}
-
-static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
-{
-	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
-
-	/* init hash transform on demand */
-	if (unlikely(!tfm)) {
-		struct crypto_shash *prev_tfm;
-
-		tfm = crypto_alloc_shash("sha256", 0, 0);
-		if (IS_ERR(tfm)) {
-			if (PTR_ERR(tfm) == -ENOENT) {
-				fscrypt_warn(NULL,
-					     "Missing crypto API support for SHA-256");
-				return -ENOPKG;
-			}
-			fscrypt_err(NULL,
-				    "Error allocating SHA-256 transform: %ld",
-				    PTR_ERR(tfm));
-			return PTR_ERR(tfm);
-		}
-		prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
-		if (prev_tfm) {
-			crypto_free_shash(tfm);
-			tfm = prev_tfm;
-		}
-	}
-
-	{
-		SHASH_DESC_ON_STACK(desc, tfm);
-		desc->tfm = tfm;
-
-		return crypto_shash_digest(desc, key, keysize, salt);
-	}
-}
-
-static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
-				int keysize)
-{
-	int err;
-	struct crypto_cipher *essiv_tfm;
-	u8 salt[SHA256_DIGEST_SIZE];
-
-	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
-	if (IS_ERR(essiv_tfm))
-		return PTR_ERR(essiv_tfm);
-
-	ci->ci_essiv_tfm = essiv_tfm;
-
-	err = derive_essiv_salt(raw_key, keysize, salt);
-	if (err)
-		goto out;
-
-	/*
-	 * Using SHA256 to derive the salt/key will result in AES-256 being
-	 * used for IV generation. File contents encryption will still use the
-	 * configured keysize (AES-128) nevertheless.
-	 */
-	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
-	if (err)
-		goto out;
-
-out:
-	memzero_explicit(salt, sizeof(salt));
-	return err;
-}
-
-/*
- * Given the encryption mode and key (normally the derived key, but for
- * DIRECT_KEY mode it's the master key), set up the inode's symmetric cipher
- * transform object(s).
- */
-static int setup_crypto_transform(struct fscrypt_info *ci,
-				  struct fscrypt_mode *mode,
-				  const u8 *raw_key, const struct inode *inode)
-{
-	struct fscrypt_master_key *mk;
-	struct crypto_skcipher *ctfm;
-	int err;
-
-	if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
-		mk = fscrypt_get_master_key(ci, mode, raw_key, inode);
-		if (IS_ERR(mk))
-			return PTR_ERR(mk);
-		ctfm = mk->mk_ctfm;
-	} else {
-		mk = NULL;
-		ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
-		if (IS_ERR(ctfm))
-			return PTR_ERR(ctfm);
-	}
-	ci->ci_master_key = mk;
-	ci->ci_ctfm = ctfm;
-
-	if (mode->needs_essiv) {
-		/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
-		WARN_ON(mode->ivsize != AES_BLOCK_SIZE);
-		WARN_ON(ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
-
-		err = init_essiv_generator(ci, raw_key, mode->keysize);
-		if (err) {
-			fscrypt_warn(inode,
-				     "Error initializing ESSIV generator: %d",
-				     err);
-			return err;
-		}
-	}
-	return 0;
-}
-
-static void put_crypt_info(struct fscrypt_info *ci)
-{
-	if (!ci)
-		return;
-
-	if (ci->ci_master_key) {
-		put_master_key(ci->ci_master_key);
-	} else {
-		crypto_free_skcipher(ci->ci_ctfm);
-		crypto_free_cipher(ci->ci_essiv_tfm);
-	}
-	kmem_cache_free(fscrypt_info_cachep, ci);
-}
-
-int fscrypt_get_encryption_info(struct inode *inode)
-{
-	struct fscrypt_info *crypt_info;
-	struct fscrypt_context ctx;
-	struct fscrypt_mode *mode;
-	u8 *raw_key = NULL;
-	int res;
-
-	if (fscrypt_has_encryption_key(inode))
-		return 0;
-
-	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
-	if (res)
-		return res;
-
-	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
-	if (res < 0) {
-		if (!fscrypt_dummy_context_enabled(inode) ||
-		    IS_ENCRYPTED(inode)) {
-			fscrypt_warn(inode,
-				     "Error %d getting encryption context",
-				     res);
-			return res;
-		}
-		/* Fake up a context for an unencrypted directory */
-		memset(&ctx, 0, sizeof(ctx));
-		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-		ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
-		ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
-		memset(ctx.master_key_descriptor, 0x42,
-		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	} else if (res != sizeof(ctx)) {
-		fscrypt_warn(inode,
-			     "Unknown encryption context size (%d bytes)", res);
-		return -EINVAL;
-	}
-
-	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) {
-		fscrypt_warn(inode, "Unknown encryption context version (%d)",
-			     ctx.format);
-		return -EINVAL;
-	}
-
-	if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
-		fscrypt_warn(inode, "Unknown encryption context flags (0x%02x)",
-			     ctx.flags);
-		return -EINVAL;
-	}
-
-	crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
-	if (!crypt_info)
-		return -ENOMEM;
-
-	crypt_info->ci_inode = inode;
-
-	crypt_info->ci_flags = ctx.flags;
-	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
-	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
-	memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
-	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
-
-	mode = select_encryption_mode(crypt_info, inode);
-	if (IS_ERR(mode)) {
-		res = PTR_ERR(mode);
-		goto out;
-	}
-	WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
-	crypt_info->ci_mode = mode;
-
-	/*
-	 * This cannot be a stack buffer because it may be passed to the
-	 * scatterlist crypto API as part of key derivation.
-	 */
-	res = -ENOMEM;
-	raw_key = kmalloc(mode->keysize, GFP_NOFS);
-	if (!raw_key)
-		goto out;
-
-	res = find_and_derive_key(inode, &ctx, raw_key, mode);
-	if (res)
-		goto out;
-
-	res = setup_crypto_transform(crypt_info, mode, raw_key, inode);
-	if (res)
-		goto out;
-
-	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL)
-		crypt_info = NULL;
-out:
-	if (res == -ENOKEY)
-		res = 0;
-	put_crypt_info(crypt_info);
-	kzfree(raw_key);
-	return res;
-}
-EXPORT_SYMBOL(fscrypt_get_encryption_info);
-
-/**
- * fscrypt_put_encryption_info - free most of an inode's fscrypt data
- *
- * Free the inode's fscrypt_info.  Filesystems must call this when the inode is
- * being evicted.  An RCU grace period need not have elapsed yet.
- */
-void fscrypt_put_encryption_info(struct inode *inode)
-{
-	put_crypt_info(inode->i_crypt_info);
-	inode->i_crypt_info = NULL;
-}
-EXPORT_SYMBOL(fscrypt_put_encryption_info);
-
-/**
- * fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay
- *
- * Free the inode's cached decrypted symlink target, if any.  Filesystems must
- * call this after an RCU grace period, just before they free the inode.
- */
-void fscrypt_free_inode(struct inode *inode)
-{
-	if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
-		kfree(inode->i_link);
-		inode->i_link = NULL;
-	}
-}
-EXPORT_SYMBOL(fscrypt_free_inode);
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
new file mode 100644
index 0000000000000..479128998ae7a
--- /dev/null
+++ b/fs/crypto/keysetup.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Key setup facility for FS encryption support.
+ *
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
+ * Heavily modified since then.
+ */
+
+#include <crypto/aes.h>
+#include <crypto/sha.h>
+#include <crypto/skcipher.h>
+#include <linux/key.h>
+
+#include "fscrypt_private.h"
+
+static struct crypto_shash *essiv_hash_tfm;
+
+static struct fscrypt_mode available_modes[] = {
+	[FSCRYPT_MODE_AES_256_XTS] = {
+		.friendly_name = "AES-256-XTS",
+		.cipher_str = "xts(aes)",
+		.keysize = 64,
+		.ivsize = 16,
+	},
+	[FSCRYPT_MODE_AES_256_CTS] = {
+		.friendly_name = "AES-256-CTS-CBC",
+		.cipher_str = "cts(cbc(aes))",
+		.keysize = 32,
+		.ivsize = 16,
+	},
+	[FSCRYPT_MODE_AES_128_CBC] = {
+		.friendly_name = "AES-128-CBC",
+		.cipher_str = "cbc(aes)",
+		.keysize = 16,
+		.ivsize = 16,
+		.needs_essiv = true,
+	},
+	[FSCRYPT_MODE_AES_128_CTS] = {
+		.friendly_name = "AES-128-CTS-CBC",
+		.cipher_str = "cts(cbc(aes))",
+		.keysize = 16,
+		.ivsize = 16,
+	},
+	[FSCRYPT_MODE_ADIANTUM] = {
+		.friendly_name = "Adiantum",
+		.cipher_str = "adiantum(xchacha12,aes)",
+		.keysize = 32,
+		.ivsize = 32,
+	},
+};
+
+static struct fscrypt_mode *
+select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
+{
+	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
+		fscrypt_warn(inode,
+			     "Unsupported encryption modes (contents mode %d, filenames mode %d)",
+			     ci->ci_data_mode, ci->ci_filename_mode);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (S_ISREG(inode->i_mode))
+		return &available_modes[ci->ci_data_mode];
+
+	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
+		return &available_modes[ci->ci_filename_mode];
+
+	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
+		  inode->i_ino, (inode->i_mode & S_IFMT));
+	return ERR_PTR(-EINVAL);
+}
+
+/* Create a symmetric cipher object for the given encryption mode and key */
+struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode,
+						  const u8 *raw_key,
+						  const struct inode *inode)
+{
+	struct crypto_skcipher *tfm;
+	int err;
+
+	tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
+	if (IS_ERR(tfm)) {
+		if (PTR_ERR(tfm) == -ENOENT) {
+			fscrypt_warn(inode,
+				     "Missing crypto API support for %s (API name: \"%s\")",
+				     mode->friendly_name, mode->cipher_str);
+			return ERR_PTR(-ENOPKG);
+		}
+		fscrypt_err(inode, "Error allocating '%s' transform: %ld",
+			    mode->cipher_str, PTR_ERR(tfm));
+		return tfm;
+	}
+	if (unlikely(!mode->logged_impl_name)) {
+		/*
+		 * fscrypt performance can vary greatly depending on which
+		 * crypto algorithm implementation is used.  Help people debug
+		 * performance problems by logging the ->cra_driver_name the
+		 * first time a mode is used.  Note that multiple threads can
+		 * race here, but it doesn't really matter.
+		 */
+		mode->logged_impl_name = true;
+		pr_info("fscrypt: %s using implementation \"%s\"\n",
+			mode->friendly_name,
+			crypto_skcipher_alg(tfm)->base.cra_driver_name);
+	}
+	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
+	err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
+	if (err)
+		goto err_free_tfm;
+
+	return tfm;
+
+err_free_tfm:
+	crypto_free_skcipher(tfm);
+	return ERR_PTR(err);
+}
+
+static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
+{
+	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
+
+	/* init hash transform on demand */
+	if (unlikely(!tfm)) {
+		struct crypto_shash *prev_tfm;
+
+		tfm = crypto_alloc_shash("sha256", 0, 0);
+		if (IS_ERR(tfm)) {
+			if (PTR_ERR(tfm) == -ENOENT) {
+				fscrypt_warn(NULL,
+					     "Missing crypto API support for SHA-256");
+				return -ENOPKG;
+			}
+			fscrypt_err(NULL,
+				    "Error allocating SHA-256 transform: %ld",
+				    PTR_ERR(tfm));
+			return PTR_ERR(tfm);
+		}
+		prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
+		if (prev_tfm) {
+			crypto_free_shash(tfm);
+			tfm = prev_tfm;
+		}
+	}
+
+	{
+		SHASH_DESC_ON_STACK(desc, tfm);
+		desc->tfm = tfm;
+
+		return crypto_shash_digest(desc, key, keysize, salt);
+	}
+}
+
+static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
+				int keysize)
+{
+	int err;
+	struct crypto_cipher *essiv_tfm;
+	u8 salt[SHA256_DIGEST_SIZE];
+
+	if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE))
+		return -EINVAL;
+
+	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
+	if (IS_ERR(essiv_tfm))
+		return PTR_ERR(essiv_tfm);
+
+	ci->ci_essiv_tfm = essiv_tfm;
+
+	err = derive_essiv_salt(raw_key, keysize, salt);
+	if (err)
+		goto out;
+
+	/*
+	 * Using SHA256 to derive the salt/key will result in AES-256 being
+	 * used for IV generation. File contents encryption will still use the
+	 * configured keysize (AES-128) nevertheless.
+	 */
+	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
+	if (err)
+		goto out;
+
+out:
+	memzero_explicit(salt, sizeof(salt));
+	return err;
+}
+
+void __exit fscrypt_essiv_cleanup(void)
+{
+	crypto_free_shash(essiv_hash_tfm);
+}
+
+/* Given the per-file key, set up the file's crypto transform object(s) */
+int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key)
+{
+	struct fscrypt_mode *mode = ci->ci_mode;
+	struct crypto_skcipher *ctfm;
+	int err;
+
+	ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode);
+	if (IS_ERR(ctfm))
+		return PTR_ERR(ctfm);
+
+	ci->ci_ctfm = ctfm;
+
+	if (mode->needs_essiv) {
+		err = init_essiv_generator(ci, derived_key, mode->keysize);
+		if (err) {
+			fscrypt_warn(ci->ci_inode,
+				     "Error initializing ESSIV generator: %d",
+				     err);
+			return err;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Find the master key, then set up the inode's actual encryption key.
+ */
+static int setup_file_encryption_key(struct fscrypt_info *ci)
+{
+	return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+}
+
+static void put_crypt_info(struct fscrypt_info *ci)
+{
+	if (!ci)
+		return;
+
+	if (ci->ci_direct_key) {
+		fscrypt_put_direct_key(ci->ci_direct_key);
+	} else {
+		crypto_free_skcipher(ci->ci_ctfm);
+		crypto_free_cipher(ci->ci_essiv_tfm);
+	}
+	kmem_cache_free(fscrypt_info_cachep, ci);
+}
+
+int fscrypt_get_encryption_info(struct inode *inode)
+{
+	struct fscrypt_info *crypt_info;
+	struct fscrypt_context ctx;
+	struct fscrypt_mode *mode;
+	int res;
+
+	if (fscrypt_has_encryption_key(inode))
+		return 0;
+
+	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
+	if (res)
+		return res;
+
+	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+	if (res < 0) {
+		if (!fscrypt_dummy_context_enabled(inode) ||
+		    IS_ENCRYPTED(inode))
+			return res;
+		/* Fake up a context for an unencrypted directory */
+		memset(&ctx, 0, sizeof(ctx));
+		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
+		ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
+		ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
+		memset(ctx.master_key_descriptor, 0x42,
+		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	} else if (res != sizeof(ctx)) {
+		fscrypt_warn(inode,
+			     "Unknown encryption context size (%d bytes)", res);
+		return -EINVAL;
+	}
+
+	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) {
+		fscrypt_warn(inode, "Unknown encryption context version (%d)",
+			     ctx.format);
+		return -EINVAL;
+	}
+
+	if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
+		fscrypt_warn(inode, "Unknown encryption context flags (0x%02x)",
+			     ctx.flags);
+		return -EINVAL;
+	}
+
+	crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
+	if (!crypt_info)
+		return -ENOMEM;
+
+	crypt_info->ci_inode = inode;
+
+	crypt_info->ci_flags = ctx.flags;
+	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
+	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
+	memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+
+	mode = select_encryption_mode(crypt_info, inode);
+	if (IS_ERR(mode)) {
+		res = PTR_ERR(mode);
+		goto out;
+	}
+	WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
+	crypt_info->ci_mode = mode;
+
+	res = setup_file_encryption_key(crypt_info);
+	if (res)
+		goto out;
+
+	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL)
+		crypt_info = NULL;
+out:
+	if (res == -ENOKEY)
+		res = 0;
+	put_crypt_info(crypt_info);
+	return res;
+}
+EXPORT_SYMBOL(fscrypt_get_encryption_info);
+
+/**
+ * fscrypt_put_encryption_info - free most of an inode's fscrypt data
+ *
+ * Free the inode's fscrypt_info.  Filesystems must call this when the inode is
+ * being evicted.  An RCU grace period need not have elapsed yet.
+ */
+void fscrypt_put_encryption_info(struct inode *inode)
+{
+	put_crypt_info(inode->i_crypt_info);
+	inode->i_crypt_info = NULL;
+}
+EXPORT_SYMBOL(fscrypt_put_encryption_info);
+
+/**
+ * fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay
+ *
+ * Free the inode's cached decrypted symlink target, if any.  Filesystems must
+ * call this after an RCU grace period, just before they free the inode.
+ */
+void fscrypt_free_inode(struct inode *inode)
+{
+	if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
+		kfree(inode->i_link);
+		inode->i_link = NULL;
+	}
+}
+EXPORT_SYMBOL(fscrypt_free_inode);
diff --git a/fs/crypto/keysetup_legacy.c b/fs/crypto/keysetup_legacy.c
new file mode 100644
index 0000000000000..b3c06322afa3c
--- /dev/null
+++ b/fs/crypto/keysetup_legacy.c
@@ -0,0 +1,338 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Key setup for v1 encryption policies
+ *
+ * Copyright 2015, 2019 Google LLC
+ */
+
+/*
+ * This file implements compatibility functions for the original encryption
+ * policy version ("v1"), including:
+ *
+ * - Deriving per-file keys using the AES-128-ECB based KDF
+ *   (rather than the new method of using HKDF-SHA512)
+ *
+ * - Retrieving fscrypt master keys from process-subscribed keyrings
+ *   (rather than the new method of using a filesystem-level keyring)
+ *
+ * - Handling policies with the DIRECT_KEY flag set using a master key table
+ *   (rather than the new method of implementing DIRECT_KEY with per-mode keys
+ *    managed alongside the master keys in the filesystem-level keyring)
+ */
+
+#include <crypto/algapi.h>
+#include <crypto/skcipher.h>
+#include <keys/user-type.h>
+#include <linux/hashtable.h>
+#include <linux/scatterlist.h>
+
+#include "fscrypt_private.h"
+
+/* Table of keys referenced by DIRECT_KEY policies */
+static DEFINE_HASHTABLE(fscrypt_direct_keys, 6); /* 6 bits = 64 buckets */
+static DEFINE_SPINLOCK(fscrypt_direct_keys_lock);
+
+/*
+ * Legacy key derivation function.  This generates the derived key by encrypting
+ * the master key with AES-128-ECB using the nonce as the AES key.  This
+ * provides a unique derived key with sufficient entropy for each inode.
+ * However, it's nonstandard, non-extensible, doesn't evenly distribute the
+ * entropy from the master key, and is trivially reversible: an attacker who
+ * compromises a derived key can "decrypt" it to get back to the master key,
+ * then derive any other key.  For all new code, use HKDF instead.
+ *
+ * The master key must be at least as long as the derived key.  If the master
+ * key is longer, then only the first 'derived_keysize' bytes are used.
+ */
+static int derive_key_aes(const u8 *master_key,
+			  const u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE],
+			  u8 *derived_key, unsigned int derived_keysize)
+{
+	int res = 0;
+	struct skcipher_request *req = NULL;
+	DECLARE_CRYPTO_WAIT(wait);
+	struct scatterlist src_sg, dst_sg;
+	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
+
+	if (IS_ERR(tfm)) {
+		res = PTR_ERR(tfm);
+		tfm = NULL;
+		goto out;
+	}
+	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
+	req = skcipher_request_alloc(tfm, GFP_NOFS);
+	if (!req) {
+		res = -ENOMEM;
+		goto out;
+	}
+	skcipher_request_set_callback(req,
+			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+			crypto_req_done, &wait);
+	res = crypto_skcipher_setkey(tfm, nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	if (res < 0)
+		goto out;
+
+	sg_init_one(&src_sg, master_key, derived_keysize);
+	sg_init_one(&dst_sg, derived_key, derived_keysize);
+	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
+				   NULL);
+	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+out:
+	skcipher_request_free(req);
+	crypto_free_skcipher(tfm);
+	return res;
+}
+
+/*
+ * Search the current task's subscribed keyrings for a "logon" key with
+ * description prefix:descriptor, and if found acquire a read lock on it and
+ * return a pointer to its validated payload in *payload_ret.
+ */
+static struct key *
+find_and_lock_process_key(const char *prefix,
+			  const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE],
+			  unsigned int min_keysize,
+			  const struct fscrypt_key **payload_ret)
+{
+	char *description;
+	struct key *key;
+	const struct user_key_payload *ukp;
+	const struct fscrypt_key *payload;
+
+	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
+				FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor);
+	if (!description)
+		return ERR_PTR(-ENOMEM);
+
+	key = request_key(&key_type_logon, description, NULL);
+	kfree(description);
+	if (IS_ERR(key))
+		return key;
+
+	down_read(&key->sem);
+	ukp = user_key_payload_locked(key);
+
+	if (!ukp) /* was the key revoked before we acquired its semaphore? */
+		goto invalid;
+
+	payload = (const struct fscrypt_key *)ukp->data;
+
+	if (ukp->datalen != sizeof(struct fscrypt_key) ||
+	    payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' has invalid payload",
+			     key->description);
+		goto invalid;
+	}
+
+	if (payload->size < min_keysize) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
+			     key->description, payload->size, min_keysize);
+		goto invalid;
+	}
+
+	*payload_ret = payload;
+	return key;
+
+invalid:
+	up_read(&key->sem);
+	key_put(key);
+	return ERR_PTR(-ENOKEY);
+}
+
+/* Master key referenced by DIRECT_KEY policy */
+struct fscrypt_direct_key {
+	struct hlist_node		dk_node;
+	refcount_t			dk_refcount;
+	const struct fscrypt_mode	*dk_mode;
+	struct crypto_skcipher		*dk_ctfm;
+	u8				dk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+	u8				dk_raw[FSCRYPT_MAX_KEY_SIZE];
+};
+
+static void free_direct_key(struct fscrypt_direct_key *dk)
+{
+	if (dk) {
+		crypto_free_skcipher(dk->dk_ctfm);
+		kzfree(dk);
+	}
+}
+
+void fscrypt_put_direct_key(struct fscrypt_direct_key *dk)
+{
+	if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock))
+		return;
+	hash_del(&dk->dk_node);
+	spin_unlock(&fscrypt_direct_keys_lock);
+
+	free_direct_key(dk);
+}
+
+/*
+ * Find/insert the given key into the fscrypt_direct_keys table.  If found, it
+ * is returned with elevated refcount, and 'to_insert' is freed if non-NULL.  If
+ * not found, 'to_insert' is inserted and returned if it's non-NULL; otherwise
+ * NULL is returned.
+ */
+static struct fscrypt_direct_key *
+find_or_insert_direct_key(struct fscrypt_direct_key *to_insert,
+			  const u8 *raw_key, const struct fscrypt_info *ci)
+{
+	unsigned long hash_key;
+	struct fscrypt_direct_key *dk;
+
+	/*
+	 * Careful: to avoid potentially leaking secret key bytes via timing
+	 * information, we must key the hash table by descriptor rather than by
+	 * raw key, and use crypto_memneq() when comparing raw keys.
+	 */
+
+	BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
+
+	spin_lock(&fscrypt_direct_keys_lock);
+	hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) {
+		if (memcmp(ci->ci_master_key_descriptor, dk->dk_descriptor,
+			   FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0)
+			continue;
+		if (ci->ci_mode != dk->dk_mode)
+			continue;
+		if (crypto_memneq(raw_key, dk->dk_raw, ci->ci_mode->keysize))
+			continue;
+		/* using existing tfm with same (descriptor, mode, raw_key) */
+		refcount_inc(&dk->dk_refcount);
+		spin_unlock(&fscrypt_direct_keys_lock);
+		free_direct_key(to_insert);
+		return dk;
+	}
+	if (to_insert)
+		hash_add(fscrypt_direct_keys, &to_insert->dk_node, hash_key);
+	spin_unlock(&fscrypt_direct_keys_lock);
+	return to_insert;
+}
+
+/* Prepare to encrypt directly using the master key in the given mode */
+static struct fscrypt_direct_key *
+fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key)
+{
+	struct fscrypt_direct_key *dk;
+	int err;
+
+	/* Is there already a tfm for this key? */
+	dk = find_or_insert_direct_key(NULL, raw_key, ci);
+	if (dk)
+		return dk;
+
+	/* Nope, allocate one. */
+	dk = kzalloc(sizeof(*dk), GFP_NOFS);
+	if (!dk)
+		return ERR_PTR(-ENOMEM);
+	refcount_set(&dk->dk_refcount, 1);
+	dk->dk_mode = ci->ci_mode;
+	dk->dk_ctfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key,
+						ci->ci_inode);
+	if (IS_ERR(dk->dk_ctfm)) {
+		err = PTR_ERR(dk->dk_ctfm);
+		dk->dk_ctfm = NULL;
+		goto err_free_dk;
+	}
+	memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor,
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize);
+
+	return find_or_insert_direct_key(dk, raw_key, ci);
+
+err_free_dk:
+	free_direct_key(dk);
+	return ERR_PTR(err);
+}
+
+/* v1 policy, DIRECT_KEY: use the master key directly */
+static int setup_v1_file_key_direct(struct fscrypt_info *ci,
+				    const u8 *raw_master_key)
+{
+	const struct fscrypt_mode *mode = ci->ci_mode;
+	struct fscrypt_direct_key *dk;
+
+	if (!fscrypt_mode_supports_direct_key(mode)) {
+		fscrypt_warn(ci->ci_inode,
+			     "Direct key mode not allowed with %s",
+			     mode->friendly_name);
+		return -EINVAL;
+	}
+
+	if (ci->ci_data_mode != ci->ci_filename_mode) {
+		fscrypt_warn(ci->ci_inode,
+			     "Direct key mode not allowed with different contents and filenames modes");
+		return -EINVAL;
+	}
+
+	/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
+	if (WARN_ON(mode->needs_essiv))
+		return -EINVAL;
+
+	dk = fscrypt_get_direct_key(ci, raw_master_key);
+	if (IS_ERR(dk))
+		return PTR_ERR(dk);
+	ci->ci_direct_key = dk;
+	ci->ci_ctfm = dk->dk_ctfm;
+	return 0;
+}
+
+/* v1 policy, !DIRECT_KEY: derive the file's encryption key */
+static int setup_v1_file_key_derived(struct fscrypt_info *ci,
+				     const u8 *raw_master_key)
+{
+	u8 *derived_key;
+	int err;
+
+	/*
+	 * This cannot be a stack buffer because it will be passed to the
+	 * scatterlist crypto API during derive_key_aes().
+	 */
+	derived_key = kmalloc(ci->ci_mode->keysize, GFP_NOFS);
+	if (!derived_key)
+		return -ENOMEM;
+
+	err = derive_key_aes(raw_master_key, ci->ci_nonce,
+			     derived_key, ci->ci_mode->keysize);
+	if (err)
+		goto out;
+
+	err = fscrypt_set_derived_key(ci, derived_key);
+out:
+	kzfree(derived_key);
+	return err;
+}
+
+int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key)
+{
+	if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
+		return setup_v1_file_key_direct(ci, raw_master_key);
+	else
+		return setup_v1_file_key_derived(ci, raw_master_key);
+}
+
+int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci)
+{
+	struct key *key;
+	const struct fscrypt_key *payload;
+	int err;
+
+	key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX,
+					ci->ci_master_key_descriptor,
+					ci->ci_mode->keysize, &payload);
+	if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) {
+		key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix,
+						ci->ci_master_key_descriptor,
+						ci->ci_mode->keysize, &payload);
+	}
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	err = fscrypt_setup_v1_file_key(ci, payload->raw);
+	up_read(&key->sem);
+	key_put(key);
+	return err;
+}
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 81c0c754f8b21..583802cb2e35d 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -138,7 +138,7 @@ extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 					void *, bool);
-/* keyinfo.c */
+/* keysetup.c */
 extern int fscrypt_get_encryption_info(struct inode *);
 extern void fscrypt_put_encryption_info(struct inode *);
 extern void fscrypt_free_inode(struct inode *);
@@ -367,7 +367,7 @@ static inline int fscrypt_inherit_context(struct inode *parent,
 	return -EOPNOTSUPP;
 }
 
-/* keyinfo.c */
+/* keysetup.c */
 static inline int fscrypt_get_encryption_info(struct inode *inode)
 {
 	return -EOPNOTSUPP;
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (4 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 18:50   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl Eric Biggers
                   ` (9 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Add a new fscrypt ioctl, FS_IOC_ADD_ENCRYPTION_KEY.  This ioctl adds an
encryption key to the filesystem's fscrypt keyring ->s_master_keys,
making any files encrypted with that key appear "unlocked".

Why we need this
~~~~~~~~~~~~~~~~

The main problem is that the "locked/unlocked" (ciphertext/plaintext)
status of encrypted files is global, but the fscrypt keys are not.
fscrypt only looks for keys in the keyring(s) the process accessing the
filesystem is subscribed to: the thread keyring, process keyring, and
session keyring, where the session keyring may contain the user keyring.

Therefore, userspace has to put fscrypt keys in the keyrings for
individual users or sessions.  But this means that when a process with a
different keyring tries to access encrypted files, whether they appear
"unlocked" or not is nondeterministic.  This is because it depends on
whether the files are currently present in the inode cache.

Fixing this by consistently providing each process its own view of the
filesystem depending on whether it has the key or not isn't feasible due
to how the VFS caches work.  Furthermore, while sometimes users expect
this behavior, it is misguided for two reasons.  First, it would be an
OS-level access control mechanism largely redundant with existing access
control mechanisms such as UNIX file permissions, ACLs, LSMs, etc.
Encryption is actually for protecting the data at rest.

Second, almost all users of fscrypt actually do need the keys to be
global.  The largest users of fscrypt, Android and Chromium OS, achieve
this by having PID 1 create a "session keyring" that is inherited by
every process.  This works, but it isn't scalable because it prevents
session keyrings from being used for any other purpose.

On general-purpose Linux distros, the 'fscrypt' userspace tool [1] can't
similarly abuse the session keyring, so to make 'sudo' work on all
systems it has to link all the user keyrings into root's user keyring
[2].  This is ugly and raises security concerns.  Moreover it can't make
the keys available to system services, such as sshd trying to access the
user's '~/.ssh' directory (see [3], [4]) or NetworkManager trying to
read certificates from the user's home directory (see [5]); or to Docker
containers (see [6], [7]).

By having an API to add a key to the *filesystem* we'll be able to fix
the above bugs, remove userspace workarounds, and clearly express the
intended semantics: the locked/unlocked status of an encrypted directory
is global, and encryption is orthogonal to OS-level access control.

Why not use the add_key() syscall
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We use an ioctl for this API rather than the existing add_key() system
call because the ioctl gives us the flexibility needed to implement
fscrypt-specific semantics that will be introduced in later patches:

- Supporting key removal with the semantics such that the secret is
  removed immediately and any unused inodes using the key are evicted;
  also, the eviction of any in-use inodes can be retried.

- Calculating a key-dependent cryptographic identifier and returning it
  to userspace.

- Allowing keys to be added and removed by non-root users, but only keys
  for v2 encryption policies; and to prevent denial-of-service attacks,
  users can only remove keys they themselves have added, and a key is
  only really removed after all users who added it have removed it.

Trying to shoehorn these semantics into the keyrings syscalls would be
very difficult, whereas the ioctls make things much easier.

However, to reuse code the implementation still uses the keyrings
service internally.  Thus we get lockless RCU-mode key lookups without
having to re-implement it, and the keys automatically show up in
/proc/keys for debugging purposes.

References:

    [1] https://github.com/google/fscrypt
    [2] https://goo.gl/55cCrI#heading=h.vf09isp98isb
    [3] https://github.com/google/fscrypt/issues/111#issuecomment-444347939
    [4] https://github.com/google/fscrypt/issues/116
    [5] https://bugs.launchpad.net/ubuntu/+source/fscrypt/+bug/1770715
    [6] https://github.com/google/fscrypt/issues/128
    [7] https://askubuntu.com/questions/1130306/cannot-run-docker-on-an-encrypted-filesystem

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/Makefile           |   1 +
 fs/crypto/crypto.c           |  10 +-
 fs/crypto/fscrypt_private.h  |  43 +++++-
 fs/crypto/keyring.c          | 289 +++++++++++++++++++++++++++++++++++
 fs/crypto/keysetup.c         |  34 ++++-
 fs/super.c                   |   2 +
 include/linux/fs.h           |   1 +
 include/linux/fscrypt.h      |  14 ++
 include/uapi/linux/fscrypt.h |  40 +++--
 9 files changed, 421 insertions(+), 13 deletions(-)
 create mode 100644 fs/crypto/keyring.c

diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile
index 3bf9939c8ce17..a640d486800da 100644
--- a/fs/crypto/Makefile
+++ b/fs/crypto/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_FS_ENCRYPTION)	+= fscrypto.o
 fscrypto-y := crypto.o \
 	      fname.o \
 	      hooks.o \
+	      keyring.o \
 	      keysetup.o \
 	      keysetup_legacy.o \
 	      policy.o
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index 7502c1f0ede9e..65ca077e8d585 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -478,6 +478,8 @@ void fscrypt_msg(const struct inode *inode, const char *level,
  */
 static int __init fscrypt_init(void)
 {
+	int err = -ENOMEM;
+
 	/*
 	 * Use an unbound workqueue to allow bios to be decrypted in parallel
 	 * even when they happen to complete on the same CPU.  This sacrifices
@@ -500,13 +502,19 @@ static int __init fscrypt_init(void)
 	if (!fscrypt_info_cachep)
 		goto fail_free_ctx;
 
+	err = fscrypt_init_keyring();
+	if (err)
+		goto fail_free_info;
+
 	return 0;
 
+fail_free_info:
+	kmem_cache_destroy(fscrypt_info_cachep);
 fail_free_ctx:
 	kmem_cache_destroy(fscrypt_ctx_cachep);
 fail_free_queue:
 	destroy_workqueue(fscrypt_read_workqueue);
 fail:
-	return -ENOMEM;
+	return err;
 }
 late_initcall(fscrypt_init)
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index a624d48b77354..86153a0044ba7 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -14,9 +14,12 @@
 #include <linux/fscrypt.h>
 #include <crypto/hash.h>
 
-/* Encryption parameters */
+#define CONST_STRLEN(str)	(sizeof(str) - 1)
+
 #define FS_KEY_DERIVATION_NONCE_SIZE	16
 
+#define FSCRYPT_MIN_KEY_SIZE		16
+
 /**
  * Encryption context for inode
  *
@@ -156,6 +159,44 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
 					 u32 orig_len, u32 max_len,
 					 u32 *encrypted_len_ret);
 
+/* keyring.c */
+
+/*
+ * fscrypt_master_key_secret - secret key material of an in-use master key
+ */
+struct fscrypt_master_key_secret {
+
+	/* Size of the raw key in bytes */
+	u32			size;
+
+	/* The raw key */
+	u8			raw[FSCRYPT_MAX_KEY_SIZE];
+
+} __randomize_layout;
+
+/*
+ * fscrypt_master_key - an in-use master key
+ *
+ * This represents a master encryption key which has been added to the
+ * filesystem and can be used to "unlock" the encrypted files which were
+ * encrypted with it.
+ */
+struct fscrypt_master_key {
+
+	/* The secret key material */
+	struct fscrypt_master_key_secret	mk_secret;
+
+	/* Arbitrary key descriptor which was assigned by userspace */
+	struct fscrypt_key_specifier		mk_spec;
+
+} __randomize_layout;
+
+extern struct key *
+fscrypt_find_master_key(struct super_block *sb,
+			const struct fscrypt_key_specifier *mk_spec);
+
+extern int __init fscrypt_init_keyring(void);
+
 /* keysetup.c */
 
 struct fscrypt_mode {
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
new file mode 100644
index 0000000000000..bd489433bba04
--- /dev/null
+++ b/fs/crypto/keyring.c
@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Filesystem-level keyring for fscrypt
+ *
+ * Copyright 2019 Google LLC
+ */
+
+/*
+ * This file implements management of fscrypt master keys in the
+ * filesystem-level keyring, including the ioctls:
+ *
+ * - FS_IOC_ADD_ENCRYPTION_KEY: add a key
+ */
+
+#include <linux/key-type.h>
+#include <linux/seq_file.h>
+
+#include "fscrypt_private.h"
+
+static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret)
+{
+	memzero_explicit(secret, sizeof(*secret));
+}
+
+static void move_master_key_secret(struct fscrypt_master_key_secret *dst,
+				   struct fscrypt_master_key_secret *src)
+{
+	memcpy(dst, src, sizeof(*dst));
+	memzero_explicit(src, sizeof(*src));
+}
+
+static void free_master_key(struct fscrypt_master_key *mk)
+{
+	wipe_master_key_secret(&mk->mk_secret);
+	kzfree(mk);
+}
+
+static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
+{
+	switch (spec->type) {
+	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
+		return FSCRYPT_KEY_DESCRIPTOR_SIZE;
+	}
+	return 0;
+}
+
+static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec)
+{
+	if (spec->__reserved)
+		return false;
+	return master_key_spec_len(spec) != 0;
+}
+
+static int fscrypt_key_instantiate(struct key *key,
+				   struct key_preparsed_payload *prep)
+{
+	key->payload.data[0] = (struct fscrypt_master_key *)prep->data;
+	return 0;
+}
+
+static void fscrypt_key_destroy(struct key *key)
+{
+	free_master_key(key->payload.data[0]);
+}
+
+static void fscrypt_key_describe(const struct key *key, struct seq_file *m)
+{
+	seq_puts(m, key->description);
+}
+
+/*
+ * Type of key in ->s_master_keys.  Each key of this type represents a master
+ * key which has been added to the filesystem.  Its payload is a
+ * 'struct fscrypt_master_key'.  The "." prefix in the key type name prevents
+ * users from adding keys of this type via the keyrings syscalls rather than via
+ * the intended method of FS_IOC_ADD_ENCRYPTION_KEY.
+ */
+static struct key_type key_type_fscrypt = {
+	.name			= "._fscrypt",
+	.instantiate		= fscrypt_key_instantiate,
+	.destroy		= fscrypt_key_destroy,
+	.describe		= fscrypt_key_describe,
+};
+
+/* Search ->s_master_keys */
+static struct key *search_fscrypt_keyring(struct key *keyring,
+					  struct key_type *type,
+					  const char *description)
+{
+	/*
+	 * We need to mark the keyring reference as "possessed" so that we
+	 * acquire permission to search it, via the KEY_POS_SEARCH permission.
+	 */
+	key_ref_t keyref = make_key_ref(keyring, true /* possessed */);
+
+	keyref = keyring_search(keyref, type, description, false);
+	if (IS_ERR(keyref)) {
+		if (PTR_ERR(keyref) == -EAGAIN || /* not found */
+		    PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */
+			keyref = ERR_PTR(-ENOKEY);
+		return ERR_CAST(keyref);
+	}
+	return key_ref_to_ptr(keyref);
+}
+
+#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE	\
+	(CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id))
+
+#define FSCRYPT_MK_DESCRIPTION_SIZE	(2 * FSCRYPT_KEY_DESCRIPTOR_SIZE + 1)
+
+static void format_fs_keyring_description(
+			char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
+			const struct super_block *sb)
+{
+	sprintf(description, "fscrypt-%s", sb->s_id);
+}
+
+static void format_mk_description(
+			char description[FSCRYPT_MK_DESCRIPTION_SIZE],
+			const struct fscrypt_key_specifier *mk_spec)
+{
+	sprintf(description, "%*phN",
+		master_key_spec_len(mk_spec), (u8 *)&mk_spec->u);
+}
+
+/* Create ->s_master_keys if needed.  Synchronized by fscrypt_add_key_mutex. */
+static int allocate_filesystem_keyring(struct super_block *sb)
+{
+	char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE];
+	struct key *keyring;
+
+	if (sb->s_master_keys)
+		return 0;
+
+	format_fs_keyring_description(description, sb);
+	keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+				current_cred(), KEY_POS_SEARCH |
+				  KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	/* Pairs with READ_ONCE() in fscrypt_find_master_key() */
+	smp_store_release(&sb->s_master_keys, keyring);
+	return 0;
+}
+
+void fscrypt_sb_free(struct super_block *sb)
+{
+	key_put(sb->s_master_keys);
+	sb->s_master_keys = NULL;
+}
+
+/*
+ * Find the specified master key in ->s_master_keys.
+ * Returns ERR_PTR(-ENOKEY) if not found.
+ */
+struct key *fscrypt_find_master_key(struct super_block *sb,
+				    const struct fscrypt_key_specifier *mk_spec)
+{
+	struct key *keyring;
+	char description[FSCRYPT_MK_DESCRIPTION_SIZE];
+
+	/* pairs with smp_store_release() in allocate_filesystem_keyring() */
+	keyring = READ_ONCE(sb->s_master_keys);
+	if (keyring == NULL)
+		return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */
+
+	format_mk_description(description, mk_spec);
+	return search_fscrypt_keyring(keyring, &key_type_fscrypt, description);
+}
+
+/*
+ * Allocate a new fscrypt_master_key which contains the given secret, set it as
+ * the payload of a new 'struct key' of type fscrypt, and link the 'struct key'
+ * into the given keyring.  Synchronized by fscrypt_add_key_mutex.
+ */
+static int add_new_master_key(struct fscrypt_master_key_secret *secret,
+			      const struct fscrypt_key_specifier *mk_spec,
+			      struct key *keyring)
+{
+	struct fscrypt_master_key *mk;
+	char description[FSCRYPT_MK_DESCRIPTION_SIZE];
+	struct key *key;
+	int err;
+
+	mk = kzalloc(sizeof(*mk), GFP_KERNEL);
+	if (!mk)
+		return -ENOMEM;
+
+	mk->mk_spec = *mk_spec;
+
+	move_master_key_secret(&mk->mk_secret, secret);
+
+	format_mk_description(description, mk_spec);
+	key = key_alloc(&key_type_fscrypt, description,
+			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
+			KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW,
+			KEY_ALLOC_NOT_IN_QUOTA, NULL);
+	if (IS_ERR(key)) {
+		err = PTR_ERR(key);
+		goto out_free_mk;
+	}
+	err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL);
+	key_put(key);
+	if (err)
+		goto out_free_mk;
+
+	return 0;
+
+out_free_mk:
+	free_master_key(mk);
+	return err;
+}
+
+static int add_master_key(struct super_block *sb,
+			  struct fscrypt_master_key_secret *secret,
+			  const struct fscrypt_key_specifier *mk_spec)
+{
+	static DEFINE_MUTEX(fscrypt_add_key_mutex);
+	struct key *key;
+	int err;
+
+	mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */
+	key = fscrypt_find_master_key(sb, mk_spec);
+	if (IS_ERR(key)) {
+		err = PTR_ERR(key);
+		if (err != -ENOKEY)
+			goto out_unlock;
+		/* Didn't find the key in ->s_master_keys.  Add it. */
+		err = allocate_filesystem_keyring(sb);
+		if (err)
+			goto out_unlock;
+		err = add_new_master_key(secret, mk_spec, sb->s_master_keys);
+	} else {
+		key_put(key);
+		err = 0;
+	}
+out_unlock:
+	mutex_unlock(&fscrypt_add_key_mutex);
+	return err;
+}
+
+/*
+ * Add a master encryption key to the filesystem, causing all files which were
+ * encrypted with it to appear "unlocked" (decrypted) when accessed.
+ */
+int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+	struct fscrypt_add_key_arg __user *uarg = _uarg;
+	struct fscrypt_add_key_arg arg;
+	struct fscrypt_master_key_secret secret;
+	int err;
+
+	if (copy_from_user(&arg, uarg, sizeof(arg)))
+		return -EFAULT;
+
+	if (!valid_key_spec(&arg.key_spec))
+		return -EINVAL;
+
+	if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE ||
+	    arg.raw_size > FSCRYPT_MAX_KEY_SIZE)
+		return -EINVAL;
+
+	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
+		return -EINVAL;
+
+	memset(&secret, 0, sizeof(secret));
+	secret.size = arg.raw_size;
+	err = -EFAULT;
+	if (copy_from_user(secret.raw, uarg->raw, secret.size))
+		goto out_wipe_secret;
+
+	err = -EACCES;
+	if (!capable(CAP_SYS_ADMIN))
+		goto out_wipe_secret;
+
+	err = add_master_key(sb, &secret, &arg.key_spec);
+out_wipe_secret:
+	wipe_master_key_secret(&secret);
+	return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
+
+int __init fscrypt_init_keyring(void)
+{
+	return register_key_type(&key_type_fscrypt);
+}
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 479128998ae7a..a457f5aefde5a 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -221,7 +221,39 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key)
  */
 static int setup_file_encryption_key(struct fscrypt_info *ci)
 {
-	return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+	struct key *key;
+	struct fscrypt_master_key *mk = NULL;
+	struct fscrypt_key_specifier mk_spec;
+	int err;
+
+	mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+	memcpy(mk_spec.u.descriptor, ci->ci_master_key_descriptor,
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+
+	key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
+	if (IS_ERR(key)) {
+		if (key != ERR_PTR(-ENOKEY))
+			return PTR_ERR(key);
+
+		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+	}
+
+	mk = key->payload.data[0];
+
+	if (mk->mk_secret.size < ci->ci_mode->keysize) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
+			     key->description, mk->mk_secret.size,
+			     ci->ci_mode->keysize);
+		err = -ENOKEY;
+		goto out_release_key;
+	}
+
+	err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+
+out_release_key:
+	key_put(key);
+	return err;
 }
 
 static void put_crypt_info(struct fscrypt_info *ci)
diff --git a/fs/super.c b/fs/super.c
index 113c58f194255..5df6c84727dc7 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -32,6 +32,7 @@
 #include <linux/backing-dev.h>
 #include <linux/rculist_bl.h>
 #include <linux/cleancache.h>
+#include <linux/fscrypt.h>
 #include <linux/fsnotify.h>
 #include <linux/lockdep.h>
 #include <linux/user_namespace.h>
@@ -290,6 +291,7 @@ static void __put_super(struct super_block *s)
 		WARN_ON(s->s_inode_lru.node);
 		WARN_ON(!list_empty(&s->s_mounts));
 		security_sb_free(s);
+		fscrypt_sb_free(s);
 		put_user_ns(s->s_user_ns);
 		kfree(s->s_subtype);
 		call_rcu(&s->rcu, destroy_super_rcu);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 56b8e358af5c1..e41be2953c553 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1427,6 +1427,7 @@ struct super_block {
 	const struct xattr_handler **s_xattr;
 #ifdef CONFIG_FS_ENCRYPTION
 	const struct fscrypt_operations	*s_cop;
+	struct key		*s_master_keys; /* master crypto keys in use */
 #endif
 	struct hlist_bl_head	s_roots;	/* alternate root dentries for NFS */
 	struct list_head	s_mounts;	/* list of mounts; _not_ for fs use */
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 583802cb2e35d..46bf66cf76ef8 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -138,6 +138,10 @@ extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 					void *, bool);
+/* keyring.c */
+extern void fscrypt_sb_free(struct super_block *sb);
+extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
+
 /* keysetup.c */
 extern int fscrypt_get_encryption_info(struct inode *);
 extern void fscrypt_put_encryption_info(struct inode *);
@@ -367,6 +371,16 @@ static inline int fscrypt_inherit_context(struct inode *parent,
 	return -EOPNOTSUPP;
 }
 
+/* keyring.c */
+static inline void fscrypt_sb_free(struct super_block *sb)
+{
+}
+
+static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
 /* keysetup.c */
 static inline int fscrypt_get_encryption_info(struct inode *inode)
 {
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 29a945d165def..93d6eabaa7de4 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -36,22 +36,42 @@ struct fscrypt_policy {
 	__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 };
 
-#define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
-#define FS_IOC_GET_ENCRYPTION_PWSALT	_IOW('f', 20, __u8[16])
-#define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
-
-/* Parameters for passing an encryption key into the kernel keyring */
+/*
+ * Process-subscribed "logon" key description prefix and payload format.
+ * Deprecated; prefer FS_IOC_ADD_ENCRYPTION_KEY instead.
+ */
 #define FSCRYPT_KEY_DESC_PREFIX		"fscrypt:"
-#define FSCRYPT_KEY_DESC_PREFIX_SIZE		8
-
-/* Structure that userspace passes to the kernel keyring */
-#define FSCRYPT_MAX_KEY_SIZE			64
-
+#define FSCRYPT_KEY_DESC_PREFIX_SIZE	8
+#define FSCRYPT_MAX_KEY_SIZE		64
 struct fscrypt_key {
 	__u32 mode;
 	__u8 raw[FSCRYPT_MAX_KEY_SIZE];
 	__u32 size;
 };
+
+struct fscrypt_key_specifier {
+#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR	1
+	__u32 type;
+	__u32 __reserved;
+	union {
+		__u8 __reserved[32]; /* reserve some extra space */
+		__u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+	} u;
+};
+
+/* Struct passed to FS_IOC_ADD_ENCRYPTION_KEY */
+struct fscrypt_add_key_arg {
+	struct fscrypt_key_specifier key_spec;
+	__u32 raw_size;
+	__u32 __reserved[9];
+	__u8 raw[];
+};
+
+#define FS_IOC_SET_ENCRYPTION_POLICY	  _IOR('f', 19, struct fscrypt_policy)
+#define FS_IOC_GET_ENCRYPTION_PWSALT	  _IOW('f', 20, __u8[16])
+#define FS_IOC_GET_ENCRYPTION_POLICY	  _IOW('f', 21, struct fscrypt_policy)
+#define FS_IOC_ADD_ENCRYPTION_KEY	 _IOWR('f', 23, struct fscrypt_add_key_arg)
+
 /**********************************************************************/
 
 /* old names; don't add anything new here! */
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (5 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 19:24   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 08/16] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl Eric Biggers
                   ` (8 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Add a new fscrypt ioctl, FS_IOC_REMOVE_ENCRYPTION_KEY.  This ioctl
removes an encryption key that was added by FS_IOC_ADD_ENCRYPTION_KEY.
It wipes the secret key itself, then "locks" the encrypted files and
directories that had been unlocked using that key -- implemented by
evicting the relevant dentries and inodes from the VFS caches.

The problem this solves is that many fscrypt users want the ability to
remove encryption keys, causing the corresponding encrypted directories
to appear "locked" (presented in ciphertext form) again.  Moreover,
users want removing an encryption key to *really* remove it, in the
sense that the removed keys cannot be recovered even if kernel memory is
compromised, e.g. by the exploit of a kernel security vulnerability or
by a physical attack.  This is desirable after a user logs out of the
system, for example.  In many cases users even already assume this to be
the case and are surprised to hear when it's not.

It is not sufficient to simply unlink the master key from the keyring
(or to revoke or invalidate it), since the actual encryption transform
objects are still pinned in memory by their inodes.  Therefore, to
really remove a key we must also evict the relevant inodes.

Currently one workaround is to run 'sync && echo 2 >
/proc/sys/vm/drop_caches'.  But, that evicts all unused inodes in the
system rather than just the inodes associated with the key being
removed, causing severe performance problems.  Moreover, it requires
root privileges, so regular users can't "lock" their encrypted files.

Another workaround, used in Chromium OS kernels, is to add a new
VFS-level ioctl FS_IOC_DROP_CACHE which is a more restricted version of
drop_caches that operates on a single super_block.  It does:

        shrink_dcache_sb(sb);
        invalidate_inodes(sb, false);

But it's still a hack.  Yet, the major users of filesystem encryption
want this feature badly enough that they are actually using these hacks.

To properly solve the problem, start maintaining a list of the inodes
which have been "unlocked" using each master key.  Originally this
wasn't possible because the kernel didn't keep track of in-use master
keys at all.  But, with the ->s_master_keys keyring it is now possible.

Then, add an ioctl FS_IOC_REMOVE_ENCRYPTION_KEY.  It finds the specified
master key in ->s_master_keys, then wipes the secret key itself, which
prevents any additional inodes from being unlocked with the key.  Then,
it syncs the filesystem and evicts the inodes in the key's list.  The
normal inode eviction code will free and wipe the per-file keys (in
->i_crypt_info).  Note that freeing ->i_crypt_info without evicting the
inodes was also considered, but would have been racy.

Some inodes may still be in use when a master key is removed, and we
can't simply revoke random file descriptors, mmap's, etc.  Thus, the
ioctl simply skips in-use inodes, and returns -EBUSY to indicate that
some inodes weren't evicted.  The master key *secret* is still removed,
but the fscrypt_master_key struct remains to keep track of the remaining
inodes.  Userspace can then retry the ioctl to evict the remaining
inodes.  Alternatively, if userspace adds the key again, the refreshed
secret will be associated with the existing list of inodes so they
remain correctly tracked for future key removals.

The ioctl doesn't wipe pagecache pages.  Thus, we tolerate that after a
kernel compromise some portions of plaintext file contents may still be
recoverable from memory.  This can be solved by enabling page poisoning
system-wide, which security conscious users may choose to do.  But it's
very difficult to solve otherwise, e.g. note that plaintext file
contents may have been read in other places than pagecache pages.

Like FS_IOC_ADD_ENCRYPTION_KEY, FS_IOC_REMOVE_ENCRYPTION_KEY is
initially restricted to privileged users only.  This is sufficient for
some use cases, but not all.  A later patch will relax this restriction,
but it will require introducing key hashes, among other changes.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/fscrypt_private.h  |  53 +++++++-
 fs/crypto/keyring.c          | 247 ++++++++++++++++++++++++++++++++++-
 fs/crypto/keysetup.c         | 103 ++++++++++++++-
 include/linux/fscrypt.h      |  13 ++
 include/uapi/linux/fscrypt.h |   7 +
 5 files changed, 418 insertions(+), 5 deletions(-)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 86153a0044ba7..3616232b4798e 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -78,6 +78,19 @@ struct fscrypt_info {
 	/* Back-pointer to the inode */
 	struct inode *ci_inode;
 
+	/*
+	 * The master key with which this inode was unlocked (decrypted).  This
+	 * will be NULL if the master key was found in a process-subscribed
+	 * keyring rather than in the filesystem-level keyring.
+	 */
+	struct key *ci_master_key;
+
+	/*
+	 * Link in list of inodes that were unlocked with the master key.
+	 * Only used when ->ci_master_key is set.
+	 */
+	struct list_head ci_master_key_link;
+
 	/*
 	 * If non-NULL, then encryption is done using the master key directly
 	 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
@@ -183,14 +196,52 @@ struct fscrypt_master_key_secret {
  */
 struct fscrypt_master_key {
 
-	/* The secret key material */
+	/*
+	 * The secret key material.  After FS_IOC_REMOVE_ENCRYPTION_KEY is
+	 * executed, this is wiped and no new inodes can be unlocked with this
+	 * key; however, there may still be inodes in ->mk_decrypted_inodes
+	 * which could not be evicted.  As long as some inodes still remain,
+	 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
+	 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
+	 *
+	 * Locking: protected by key->sem.
+	 */
 	struct fscrypt_master_key_secret	mk_secret;
 
 	/* Arbitrary key descriptor which was assigned by userspace */
 	struct fscrypt_key_specifier		mk_spec;
 
+	/*
+	 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
+	 * Once this goes to 0, the master key is removed from ->s_master_keys.
+	 * The 'struct fscrypt_master_key' will continue to live as long as the
+	 * 'struct key' whose payload it is, but we won't let this reference
+	 * count rise again.
+	 */
+	refcount_t		mk_refcount;
+
+	/*
+	 * List of inodes that were unlocked using this key.  This allows the
+	 * inodes to be evicted efficiently if the key is removed.
+	 */
+	struct list_head	mk_decrypted_inodes;
+	spinlock_t		mk_decrypted_inodes_lock;
+
 } __randomize_layout;
 
+static inline bool
+is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
+{
+	/*
+	 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
+	 * fscrypt_key_describe().  These run in atomic context, so they can't
+	 * take key->sem and thus 'secret' can change concurrently which would
+	 * be a data race.  But they only need to know whether the secret *was*
+	 * present at the time of check, so READ_ONCE() suffices.
+	 */
+	return READ_ONCE(secret->size) != 0;
+}
+
 extern struct key *
 fscrypt_find_master_key(struct super_block *sb,
 			const struct fscrypt_key_specifier *mk_spec);
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index bd489433bba04..ce33c38955233 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -10,6 +10,7 @@
  * filesystem-level keyring, including the ioctls:
  *
  * - FS_IOC_ADD_ENCRYPTION_KEY: add a key
+ * - FS_IOC_REMOVE_ENCRYPTION_KEY: remove a key
  */
 
 #include <linux/key-type.h>
@@ -66,6 +67,13 @@ static void fscrypt_key_destroy(struct key *key)
 static void fscrypt_key_describe(const struct key *key, struct seq_file *m)
 {
 	seq_puts(m, key->description);
+
+	if (key_is_positive(key)) {
+		const struct fscrypt_master_key *mk = key->payload.data[0];
+
+		if (!is_master_key_secret_present(&mk->mk_secret))
+			seq_puts(m, ": secret removed");
+	}
 }
 
 /*
@@ -192,6 +200,10 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret,
 
 	move_master_key_secret(&mk->mk_secret, secret);
 
+	refcount_set(&mk->mk_refcount, 1); /* secret is present */
+	INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
+	spin_lock_init(&mk->mk_decrypted_inodes_lock);
+
 	format_mk_description(description, mk_spec);
 	key = key_alloc(&key_type_fscrypt, description,
 			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
@@ -213,6 +225,22 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret,
 	return err;
 }
 
+#define KEY_DEAD	1
+
+static int add_existing_master_key(struct fscrypt_master_key *mk,
+				   struct fscrypt_master_key_secret *secret,
+				   const struct fscrypt_key_specifier *mk_spec)
+{
+	if (is_master_key_secret_present(&mk->mk_secret))
+		return 0;
+
+	if (!refcount_inc_not_zero(&mk->mk_refcount))
+		return KEY_DEAD;
+
+	move_master_key_secret(&mk->mk_secret, secret);
+	return 0;
+}
+
 static int add_master_key(struct super_block *sb,
 			  struct fscrypt_master_key_secret *secret,
 			  const struct fscrypt_key_specifier *mk_spec)
@@ -222,6 +250,7 @@ static int add_master_key(struct super_block *sb,
 	int err;
 
 	mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */
+retry:
 	key = fscrypt_find_master_key(sb, mk_spec);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);
@@ -233,8 +262,21 @@ static int add_master_key(struct super_block *sb,
 			goto out_unlock;
 		err = add_new_master_key(secret, mk_spec, sb->s_master_keys);
 	} else {
+		/*
+		 * Found the key in ->s_master_keys.  Re-add the secret if
+		 * needed.
+		 */
+		down_write(&key->sem);
+		err = add_existing_master_key(key->payload.data[0], secret,
+					      mk_spec);
+		up_write(&key->sem);
+		if (err == KEY_DEAD) {
+			/* Key being removed or needs to be removed */
+			key_invalidate(key);
+			key_put(key);
+			goto retry;
+		}
 		key_put(key);
-		err = 0;
 	}
 out_unlock:
 	mutex_unlock(&fscrypt_add_key_mutex);
@@ -283,6 +325,209 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 }
 EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
 
+static void shrink_dcache_inode(struct inode *inode)
+{
+	struct dentry *dentry;
+
+	if (S_ISDIR(inode->i_mode)) {
+		dentry = d_find_any_alias(inode);
+		if (dentry) {
+			shrink_dcache_parent(dentry);
+			dput(dentry);
+		}
+	}
+	d_prune_aliases(inode);
+}
+
+static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk)
+{
+	struct fscrypt_info *ci;
+	struct inode *inode;
+	struct inode *toput_inode = NULL;
+
+	spin_lock(&mk->mk_decrypted_inodes_lock);
+
+	list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) {
+		inode = ci->ci_inode;
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&mk->mk_decrypted_inodes_lock);
+
+		shrink_dcache_inode(inode);
+		iput(toput_inode);
+		toput_inode = inode;
+
+		spin_lock(&mk->mk_decrypted_inodes_lock);
+	}
+
+	spin_unlock(&mk->mk_decrypted_inodes_lock);
+	iput(toput_inode);
+}
+
+static int check_for_busy_inodes(struct super_block *sb,
+				 struct fscrypt_master_key *mk)
+{
+	struct list_head *pos;
+	size_t busy_count = 0;
+	unsigned long ino;
+	struct dentry *dentry;
+	char _path[256];
+	char *path = NULL;
+
+	spin_lock(&mk->mk_decrypted_inodes_lock);
+
+	list_for_each(pos, &mk->mk_decrypted_inodes)
+		busy_count++;
+
+	if (busy_count == 0) {
+		spin_unlock(&mk->mk_decrypted_inodes_lock);
+		return 0;
+	}
+
+	{
+		/* select an example file to show for debugging purposes */
+		struct inode *inode =
+			list_first_entry(&mk->mk_decrypted_inodes,
+					 struct fscrypt_info,
+					 ci_master_key_link)->ci_inode;
+		ino = inode->i_ino;
+		dentry = d_find_alias(inode);
+	}
+	spin_unlock(&mk->mk_decrypted_inodes_lock);
+
+	if (dentry) {
+		path = dentry_path(dentry, _path, sizeof(_path));
+		dput(dentry);
+	}
+	if (IS_ERR_OR_NULL(path))
+		path = "(unknown)";
+
+	fscrypt_warn(NULL,
+		     "%s: %zu inodes still busy after removing key with description %*phN, including ino %lu (%s)",
+		     sb->s_id, busy_count, master_key_spec_len(&mk->mk_spec),
+		     (u8 *)&mk->mk_spec.u, ino, path);
+	return -EBUSY;
+}
+
+static int try_to_lock_encrypted_files(struct super_block *sb,
+				       struct fscrypt_master_key *mk)
+{
+	int err1;
+	int err2;
+
+	/*
+	 * An inode can't be evicted while it is dirty or has dirty pages.
+	 * Thus, we first have to clean the inodes in ->mk_decrypted_inodes.
+	 *
+	 * Just do it the easy way: call sync_filesystem().  It's overkill, but
+	 * it works, and it's more important to minimize the amount of caches we
+	 * drop than the amount of data we sync.  Also, unprivileged users can
+	 * already call sync_filesystem() via sys_syncfs() or sys_sync().
+	 */
+	down_read(&sb->s_umount);
+	err1 = sync_filesystem(sb);
+	up_read(&sb->s_umount);
+	/* If a sync error occurs, still try to evict as much as possible. */
+
+	/*
+	 * Inodes are pinned by their dentries, so we have to evict their
+	 * dentries.  shrink_dcache_sb() would suffice, but would be overkill
+	 * and inappropriate for use by unprivileged users.  So instead go
+	 * through the inodes' alias lists and try to evict each dentry.
+	 */
+	evict_dentries_for_decrypted_inodes(mk);
+
+	/*
+	 * evict_dentries_for_decrypted_inodes() already iput() each inode in
+	 * the list; any inodes for which that dropped the last reference will
+	 * have been evicted due to fscrypt_drop_inode() detecting the key
+	 * removal and telling the VFS to evict the inode.  So to finish, we
+	 * just need to check whether any inodes couldn't be evicted.
+	 */
+	err2 = check_for_busy_inodes(sb, mk);
+
+	return err1 ?: err2;
+}
+
+/*
+ * Try to remove an fscrypt master encryption key.  If other users have also
+ * added the key, we'll remove the current user's usage of the key, then return
+ * -EUSERS.  Otherwise we'll continue on and try to actually remove the key.
+ *
+ * First we wipe the actual master key secret from memory, so that no more
+ * inodes can be unlocked with it.  Then, we try to evict all cached inodes that
+ * had been unlocked using the key.  Since this can fail for in-use inodes, this
+ * is expected to be used in cooperation with userspace ensuring that none of
+ * the files are still open.
+ *
+ * If, nevertheless, some inodes could not be evicted, we return -EBUSY
+ * (although we still evicted as many inodes as possible) and keep the 'struct
+ * key' and the 'struct fscrypt_master_key' around to keep track of the list of
+ * remaining inodes.  Userspace can then retry the ioctl later to retry evicting
+ * the remaining inodes, or alternatively can add the secret key again.
+ *
+ * Note that even though we wipe the encryption *keys* from memory, decrypted
+ * data can likely still be found in memory, e.g. in pagecache pages that have
+ * been freed.  Wiping such data is currently out of scope, short of users who
+ * may choose to enable page and slab poisoning systemwide.
+ */
+int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+	struct fscrypt_remove_key_arg arg;
+	struct key *key;
+	struct fscrypt_master_key *mk;
+	int err;
+	bool dead;
+
+	if (copy_from_user(&arg, uarg, sizeof(arg)))
+		return -EFAULT;
+
+	if (!valid_key_spec(&arg.key_spec))
+		return -EINVAL;
+
+	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
+		return -EINVAL;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	/* Find the key being removed. */
+	key = fscrypt_find_master_key(sb, &arg.key_spec);
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+	mk = key->payload.data[0];
+
+	down_write(&key->sem);
+
+	/* Wipe the secret. */
+	dead = false;
+	if (is_master_key_secret_present(&mk->mk_secret)) {
+		wipe_master_key_secret(&mk->mk_secret);
+		dead = refcount_dec_and_test(&mk->mk_refcount);
+	}
+	up_write(&key->sem);
+	if (dead) {
+		/*
+		 * We wiped the secret and no inodes reference the key anymore,
+		 * so it's free to remove.
+		 */
+		key_invalidate(key);
+		err = 0;
+	} else {
+		/* Some inodes still reference this key; try to evict them. */
+		err = try_to_lock_encrypted_files(sb, mk);
+	}
+	key_put(key);
+	return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
+
 int __init fscrypt_init_keyring(void)
 {
 	return register_key_type(&key_type_fscrypt);
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index a457f5aefde5a..6b35c550e87a4 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -218,8 +218,16 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key)
 
 /*
  * Find the master key, then set up the inode's actual encryption key.
+ *
+ * If the master key is found in the filesystem-level keyring, then the
+ * corresponding 'struct key' is returned in *master_key_ret with
+ * ->sem read-locked.  This is needed to ensure that only one task links the
+ * fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race to create
+ * an fscrypt_info for the same inode), and to synchronize the master key being
+ * removed with a new inode starting to use it.
  */
-static int setup_file_encryption_key(struct fscrypt_info *ci)
+static int setup_file_encryption_key(struct fscrypt_info *ci,
+				     struct key **master_key_ret)
 {
 	struct key *key;
 	struct fscrypt_master_key *mk = NULL;
@@ -239,6 +247,13 @@ static int setup_file_encryption_key(struct fscrypt_info *ci)
 	}
 
 	mk = key->payload.data[0];
+	down_read(&key->sem);
+
+	/* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
+	if (!is_master_key_secret_present(&mk->mk_secret)) {
+		err = -ENOKEY;
+		goto out_release_key;
+	}
 
 	if (mk->mk_secret.size < ci->ci_mode->keysize) {
 		fscrypt_warn(NULL,
@@ -250,14 +265,22 @@ static int setup_file_encryption_key(struct fscrypt_info *ci)
 	}
 
 	err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+	if (err)
+		goto out_release_key;
+
+	*master_key_ret = key;
+	return 0;
 
 out_release_key:
+	up_read(&key->sem);
 	key_put(key);
 	return err;
 }
 
 static void put_crypt_info(struct fscrypt_info *ci)
 {
+	struct key *key;
+
 	if (!ci)
 		return;
 
@@ -267,6 +290,26 @@ static void put_crypt_info(struct fscrypt_info *ci)
 		crypto_free_skcipher(ci->ci_ctfm);
 		crypto_free_cipher(ci->ci_essiv_tfm);
 	}
+
+	key = ci->ci_master_key;
+	if (key) {
+		struct fscrypt_master_key *mk = key->payload.data[0];
+
+		/*
+		 * Remove this inode from the list of inodes that were unlocked
+		 * with the master key.
+		 *
+		 * In addition, if we're removing the last inode from a key that
+		 * already had its secret removed, invalidate the key so that it
+		 * gets removed from ->s_master_keys.
+		 */
+		spin_lock(&mk->mk_decrypted_inodes_lock);
+		list_del(&ci->ci_master_key_link);
+		spin_unlock(&mk->mk_decrypted_inodes_lock);
+		if (refcount_dec_and_test(&mk->mk_refcount))
+			key_invalidate(key);
+		key_put(key);
+	}
 	kmem_cache_free(fscrypt_info_cachep, ci);
 }
 
@@ -275,6 +318,7 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	struct fscrypt_info *crypt_info;
 	struct fscrypt_context ctx;
 	struct fscrypt_mode *mode;
+	struct key *master_key = NULL;
 	int res;
 
 	if (fscrypt_has_encryption_key(inode))
@@ -335,13 +379,30 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
 	crypt_info->ci_mode = mode;
 
-	res = setup_file_encryption_key(crypt_info);
+	res = setup_file_encryption_key(crypt_info, &master_key);
 	if (res)
 		goto out;
 
-	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL)
+	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
+		if (master_key) {
+			struct fscrypt_master_key *mk =
+				master_key->payload.data[0];
+
+			refcount_inc(&mk->mk_refcount);
+			crypt_info->ci_master_key = key_get(master_key);
+			spin_lock(&mk->mk_decrypted_inodes_lock);
+			list_add(&crypt_info->ci_master_key_link,
+				 &mk->mk_decrypted_inodes);
+			spin_unlock(&mk->mk_decrypted_inodes_lock);
+		}
 		crypt_info = NULL;
+	}
+	res = 0;
 out:
+	if (master_key) {
+		up_read(&master_key->sem);
+		key_put(master_key);
+	}
 	if (res == -ENOKEY)
 		res = 0;
 	put_crypt_info(crypt_info);
@@ -376,3 +437,39 @@ void fscrypt_free_inode(struct inode *inode)
 	}
 }
 EXPORT_SYMBOL(fscrypt_free_inode);
+
+/**
+ * fscrypt_drop_inode - check whether the inode's master key has been removed
+ *
+ * Filesystems supporting fscrypt must call this from their ->drop_inode()
+ * method so that encrypted inodes are evicted as soon as they're no longer in
+ * use and their master key has been removed.
+ *
+ * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
+ */
+int fscrypt_drop_inode(struct inode *inode)
+{
+	const struct fscrypt_info *ci = READ_ONCE(inode->i_crypt_info);
+	const struct fscrypt_master_key *mk;
+
+	/*
+	 * If ci is NULL, then the inode doesn't have an encryption key set up
+	 * so it's irrelevant.  If ci_master_key is NULL, then the master key
+	 * was provided via the legacy mechanism of the process-subscribed
+	 * keyrings, so we don't know whether it's been removed or not.
+	 */
+	if (!ci || !ci->ci_master_key)
+		return 0;
+	mk = ci->ci_master_key->payload.data[0];
+
+	/*
+	 * Note: since we aren't holding key->sem, the result here can
+	 * immediately become outdated.  But there's no correctness problem with
+	 * unnecessarily evicting.  Nor is there a correctness problem with not
+	 * evicting while iput() is racing with the key being removed, since
+	 * then the thread removing the key will either evict the inode itself
+	 * or will correctly detect that it wasn't evicted due to the race.
+	 */
+	return !is_master_key_secret_present(&mk->mk_secret);
+}
+EXPORT_SYMBOL(fscrypt_drop_inode);
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 46bf66cf76ef8..c1b80b981cec2 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -141,11 +141,13 @@ extern int fscrypt_inherit_context(struct inode *, struct inode *,
 /* keyring.c */
 extern void fscrypt_sb_free(struct super_block *sb);
 extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
+extern int fscrypt_ioctl_remove_key(struct file *filp, const void __user *arg);
 
 /* keysetup.c */
 extern int fscrypt_get_encryption_info(struct inode *);
 extern void fscrypt_put_encryption_info(struct inode *);
 extern void fscrypt_free_inode(struct inode *);
+extern int fscrypt_drop_inode(struct inode *inode);
 
 /* fname.c */
 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
@@ -381,6 +383,12 @@ static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
 	return -EOPNOTSUPP;
 }
 
+static inline int fscrypt_ioctl_remove_key(struct file *filp,
+					   const void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
 /* keysetup.c */
 static inline int fscrypt_get_encryption_info(struct inode *inode)
 {
@@ -396,6 +404,11 @@ static inline void fscrypt_free_inode(struct inode *inode)
 {
 }
 
+static inline int fscrypt_drop_inode(struct inode *inode)
+{
+	return 0;
+}
+
  /* fname.c */
 static inline int fscrypt_setup_filename(struct inode *dir,
 					 const struct qstr *iname,
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 93d6eabaa7de4..cbe1ec46a4b56 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -67,10 +67,17 @@ struct fscrypt_add_key_arg {
 	__u8 raw[];
 };
 
+/* Struct passed to FS_IOC_REMOVE_ENCRYPTION_KEY */
+struct fscrypt_remove_key_arg {
+	struct fscrypt_key_specifier key_spec;
+	__u32 __reserved[6];
+};
+
 #define FS_IOC_SET_ENCRYPTION_POLICY	  _IOR('f', 19, struct fscrypt_policy)
 #define FS_IOC_GET_ENCRYPTION_PWSALT	  _IOW('f', 20, __u8[16])
 #define FS_IOC_GET_ENCRYPTION_POLICY	  _IOW('f', 21, struct fscrypt_policy)
 #define FS_IOC_ADD_ENCRYPTION_KEY	 _IOWR('f', 23, struct fscrypt_add_key_arg)
+#define FS_IOC_REMOVE_ENCRYPTION_KEY	  _IOW('f', 24, struct fscrypt_remove_key_arg)
 
 /**********************************************************************/
 
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 08/16] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (6 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 19:30   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation Eric Biggers
                   ` (7 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Add a new fscrypt ioctl, FS_IOC_GET_ENCRYPTION_KEY_STATUS.  Given a key
specified by 'struct fscrypt_key_specifier' (the same way a key is
specified for the other fscrypt key management ioctls), it returns
status information in a 'struct fscrypt_get_key_status_arg'.

The main motivation for this is that applications need to be able to
check whether an encrypted directory is "unlocked" or not, so that they
can add the key if it is not, and avoid adding the key (which may
involve prompting the user for a passphrase) if it already is.

It's possible to use some workarounds such as checking whether opening a
regular file fails with ENOKEY, or checking whether the filenames "look
like gibberish" or not.  However, no workaround is usable in all cases.

Like the other key management ioctls, the keyrings syscalls may seem at
first to be a good fit for this.  Unfortunately, they are not.  Even if
we exposed the keyring ID of the ->s_master_keys keyring and gave
everyone Search permission on it (note: currently the keyrings
permission system would also allow everyone to "invalidate" the keyring
too), the fscrypt keys have an additional state that doesn't map cleanly
to the keyrings API: the secret can be removed, but we can be still
tracking the files that were using the key, and the removal can be
re-attempted or the secret added again.

After later patches, some applications will also need a way to determine
whether a key was added by the current user vs. by some other user.
Reserved fields are included in fscrypt_get_key_status_arg for this and
other future extensions.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/keyring.c          | 60 ++++++++++++++++++++++++++++++++++++
 include/linux/fscrypt.h      |  7 +++++
 include/uapi/linux/fscrypt.h | 15 +++++++++
 3 files changed, 82 insertions(+)

diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index ce33c38955233..02a94d7cc739e 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -11,6 +11,7 @@
  *
  * - FS_IOC_ADD_ENCRYPTION_KEY: add a key
  * - FS_IOC_REMOVE_ENCRYPTION_KEY: remove a key
+ * - FS_IOC_GET_ENCRYPTION_KEY_STATUS: get key status
  */
 
 #include <linux/key-type.h>
@@ -528,6 +529,65 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg)
 }
 EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
 
+/*
+ * Retrieve the status of an fscrypt master encryption key.
+ *
+ * We set ->status to indicate whether the key is absent, present, or
+ * incompletely removed.  "Incompletely removed" means that the master key
+ * secret has been removed, but some files which had been unlocked with it are
+ * still in use.  This field allows applications to easily determine the state
+ * of an encrypted directory without using a hack such as trying to open a
+ * regular file in it (which can confuse the "incompletely removed" state with
+ * absent or present).
+ */
+int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+	struct fscrypt_get_key_status_arg arg;
+	struct key *key;
+	struct fscrypt_master_key *mk;
+	int err;
+
+	if (copy_from_user(&arg, uarg, sizeof(arg)))
+		return -EFAULT;
+
+	if (!valid_key_spec(&arg.key_spec))
+		return -EINVAL;
+
+	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
+		return -EINVAL;
+
+	memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved));
+
+	key = fscrypt_find_master_key(sb, &arg.key_spec);
+	if (IS_ERR(key)) {
+		if (key != ERR_PTR(-ENOKEY))
+			return PTR_ERR(key);
+		arg.status = FSCRYPT_KEY_STATUS_ABSENT;
+		err = 0;
+		goto out;
+	}
+	mk = key->payload.data[0];
+	down_read(&key->sem);
+
+	if (!is_master_key_secret_present(&mk->mk_secret)) {
+		arg.status = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED;
+		err = 0;
+		goto out_release_key;
+	}
+
+	arg.status = FSCRYPT_KEY_STATUS_PRESENT;
+	err = 0;
+out_release_key:
+	up_read(&key->sem);
+	key_put(key);
+out:
+	if (!err && copy_to_user(uarg, &arg, sizeof(arg)))
+		err = -EFAULT;
+	return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status);
+
 int __init fscrypt_init_keyring(void)
 {
 	return register_key_type(&key_type_fscrypt);
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index c1b80b981cec2..cf41d2a596b3d 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -142,6 +142,7 @@ extern int fscrypt_inherit_context(struct inode *, struct inode *,
 extern void fscrypt_sb_free(struct super_block *sb);
 extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
 extern int fscrypt_ioctl_remove_key(struct file *filp, const void __user *arg);
+extern int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg);
 
 /* keysetup.c */
 extern int fscrypt_get_encryption_info(struct inode *);
@@ -389,6 +390,12 @@ static inline int fscrypt_ioctl_remove_key(struct file *filp,
 	return -EOPNOTSUPP;
 }
 
+static inline int fscrypt_ioctl_get_key_status(struct file *filp,
+					       void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
 /* keysetup.c */
 static inline int fscrypt_get_encryption_info(struct inode *inode)
 {
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index cbe1ec46a4b56..4f507f8d12261 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -73,11 +73,26 @@ struct fscrypt_remove_key_arg {
 	__u32 __reserved[6];
 };
 
+/* Struct passed to FS_IOC_GET_ENCRYPTION_KEY_STATUS */
+struct fscrypt_get_key_status_arg {
+	/* input */
+	struct fscrypt_key_specifier key_spec;
+	__u32 __reserved[6];
+
+	/* output */
+#define FSCRYPT_KEY_STATUS_ABSENT		1
+#define FSCRYPT_KEY_STATUS_PRESENT		2
+#define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED	3
+	__u32 status;
+	__u32 __out_reserved[15];
+};
+
 #define FS_IOC_SET_ENCRYPTION_POLICY	  _IOR('f', 19, struct fscrypt_policy)
 #define FS_IOC_GET_ENCRYPTION_PWSALT	  _IOW('f', 20, __u8[16])
 #define FS_IOC_GET_ENCRYPTION_POLICY	  _IOW('f', 21, struct fscrypt_policy)
 #define FS_IOC_ADD_ENCRYPTION_KEY	 _IOWR('f', 23, struct fscrypt_add_key_arg)
 #define FS_IOC_REMOVE_ENCRYPTION_KEY	  _IOW('f', 24, struct fscrypt_remove_key_arg)
+#define FS_IOC_GET_ENCRYPTION_KEY_STATUS _IOWR('f', 25, struct fscrypt_get_key_status_arg)
 
 /**********************************************************************/
 
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (7 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 08/16] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 19:39   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 10/16] fscrypt: v2 encryption policy support Eric Biggers
                   ` (6 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Add an implementation of HKDF (RFC 5869) to fscrypt, for the purpose of
deriving additional key material from the fscrypt master keys for v2
encryption policies.  HKDF is a key derivation function built on top of
HMAC.  We choose SHA-512 for the underlying unkeyed hash, and use an
"hmac(sha512)" transform allocated from the crypto API.

We'll be using this to replace the AES-ECB based KDF currently used to
derive the per-file encryption keys.  While the AES-ECB based KDF is
believed to meet the original security requirements, it is nonstandard
and has problems that don't exist in modern KDFs such as HKDF:

1. It's reversible.  Given a derived key and nonce, an attacker can
   easily compute the master key.  This is okay if the master key and
   derived keys are equally hard to compromise, but now we'd like to be
   more robust against threats such as a derived key being compromised
   through a timing attack, or a derived key for an in-use file being
   compromised after the master key has already been removed.

2. It doesn't evenly distribute the entropy from the master key; each 16
   input bytes only affects the corresponding 16 output bytes.

3. It isn't easily extensible to deriving other values or keys, such as
   a public hash for securely identifying the key, or per-mode keys.
   Per-mode keys will be immediately useful for Adiantum encryption, for
   which fscrypt currently uses the master key directly, introducing
   unnecessary usage constraints.  Per-mode keys will also be useful for
   hardware inline encryption, which is currently being worked on.

HKDF solves all the above problems.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/Kconfig           |   2 +
 fs/crypto/Makefile          |   1 +
 fs/crypto/fscrypt_private.h |  15 +++
 fs/crypto/hkdf.c            | 181 ++++++++++++++++++++++++++++++++++++
 4 files changed, 199 insertions(+)
 create mode 100644 fs/crypto/hkdf.c

diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
index 5fdf24877c178..ff5a1746cbae4 100644
--- a/fs/crypto/Kconfig
+++ b/fs/crypto/Kconfig
@@ -7,6 +7,8 @@ config FS_ENCRYPTION
 	select CRYPTO_ECB
 	select CRYPTO_XTS
 	select CRYPTO_CTS
+	select CRYPTO_SHA512
+	select CRYPTO_HMAC
 	select KEYS
 	help
 	  Enable encryption of files and directories.  This
diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile
index a640d486800da..3333e2ac859fa 100644
--- a/fs/crypto/Makefile
+++ b/fs/crypto/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_FS_ENCRYPTION)	+= fscrypto.o
 
 fscrypto-y := crypto.o \
 	      fname.o \
+	      hkdf.o \
 	      hooks.o \
 	      keyring.o \
 	      keysetup.o \
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 3616232b4798e..92567efec2cd5 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -172,6 +172,21 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
 					 u32 orig_len, u32 max_len,
 					 u32 *encrypted_len_ret);
 
+/* hkdf.c */
+
+struct fscrypt_hkdf {
+	struct crypto_shash *hmac_tfm;
+};
+
+extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
+			     unsigned int master_key_size);
+
+extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
+			       const u8 *info, unsigned int infolen,
+			       u8 *okm, unsigned int okmlen);
+
+extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
+
 /* keyring.c */
 
 /*
diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
new file mode 100644
index 0000000000000..f21873e1b4674
--- /dev/null
+++ b/fs/crypto/hkdf.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
+ * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
+ * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
+ *
+ * This is used to derive keys from the fscrypt master keys.
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <crypto/hash.h>
+#include <crypto/sha.h>
+
+#include "fscrypt_private.h"
+
+/*
+ * HKDF supports any unkeyed cryptographic hash algorithm, but fscrypt uses
+ * SHA-512 because it is reasonably secure and efficient; and since it produces
+ * a 64-byte digest, deriving an AES-256-XTS key preserves all 64 bytes of
+ * entropy from the master key and requires only one iteration of HKDF-Expand.
+ */
+#define HKDF_HMAC_ALG		"hmac(sha512)"
+#define HKDF_HASHLEN		SHA512_DIGEST_SIZE
+
+/*
+ * HKDF consists of two steps:
+ *
+ * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from
+ *    the input keying material and optional salt.
+ * 2. HKDF-Expand: expand the pseudorandom key into output keying material of
+ *    any length, parameterized by an application-specific info string.
+ *
+ * HKDF-Extract can be skipped if the input is already a pseudorandom key of
+ * length HKDF_HASHLEN bytes.  However, cipher modes other than AES-256-XTS take
+ * shorter keys, and we don't want to force users of those modes to provide
+ * unnecessarily long master keys.  Thus fscrypt still does HKDF-Extract.  No
+ * salt is used, since fscrypt master keys should already be pseudorandom and
+ * there's no way to persist a random salt per master key from kernel mode.
+ */
+
+/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
+static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
+{
+	static const u8 default_salt[HKDF_HASHLEN];
+	SHASH_DESC_ON_STACK(desc, hmac_tfm);
+	int err;
+
+	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
+	if (err)
+		return err;
+
+	desc->tfm = hmac_tfm;
+	err = crypto_shash_digest(desc, ikm, ikmlen, prk);
+	shash_desc_zero(desc);
+	return err;
+}
+
+/*
+ * Compute HKDF-Extract using the given master key as the input keying material,
+ * and prepare an HMAC transform object keyed by the resulting pseudorandom key.
+ *
+ * Afterwards, the keyed HMAC transform object can be used for HKDF-Expand many
+ * times without having to recompute HKDF-Extract each time.
+ */
+int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
+		      unsigned int master_key_size)
+{
+	struct crypto_shash *hmac_tfm;
+	u8 prk[HKDF_HASHLEN];
+	int err;
+
+	hmac_tfm = crypto_alloc_shash(HKDF_HMAC_ALG, 0, 0);
+	if (IS_ERR(hmac_tfm)) {
+		fscrypt_err(NULL, "Error allocating " HKDF_HMAC_ALG ": %ld",
+			    PTR_ERR(hmac_tfm));
+		return PTR_ERR(hmac_tfm);
+	}
+
+	if (WARN_ON(crypto_shash_digestsize(hmac_tfm) != sizeof(prk))) {
+		err = -EINVAL;
+		goto err_free_tfm;
+	}
+
+	err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk);
+	if (err)
+		goto err_free_tfm;
+
+	err = crypto_shash_setkey(hmac_tfm, prk, sizeof(prk));
+	if (err)
+		goto err_free_tfm;
+
+	hkdf->hmac_tfm = hmac_tfm;
+	goto out;
+
+err_free_tfm:
+	crypto_free_shash(hmac_tfm);
+out:
+	memzero_explicit(prk, sizeof(prk));
+	return err;
+}
+
+/*
+ * HKDF-Expand (RFC 5869 section 2.3).  This expands the pseudorandom key, which
+ * was already keyed into 'hkdf->hmac_tfm' by fscrypt_init_hkdf(), into 'okmlen'
+ * bytes of output keying material parameterized by the application-specific
+ * 'info' of length 'infolen' bytes, prefixed by "fscrypt\0" and the 'context'
+ * byte.  This is thread-safe and may be called by multiple threads in parallel.
+ *
+ * ('context' isn't part of the HKDF specification; it's just a prefix fscrypt
+ * adds to its application-specific info strings to guarantee that it doesn't
+ * accidentally repeat an info string when using HKDF for different purposes.)
+ */
+int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
+			const u8 *info, unsigned int infolen,
+			u8 *okm, unsigned int okmlen)
+{
+	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
+	u8 prefix[9];
+	unsigned int i;
+	int err;
+	const u8 *prev = NULL;
+	u8 counter = 1;
+	u8 tmp[HKDF_HASHLEN];
+
+	if (WARN_ON(okmlen > 255 * HKDF_HASHLEN))
+		return -EINVAL;
+
+	desc->tfm = hkdf->hmac_tfm;
+
+	memcpy(prefix, "fscrypt\0", 8);
+	prefix[8] = context;
+
+	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
+
+		err = crypto_shash_init(desc);
+		if (err)
+			goto out;
+
+		if (prev) {
+			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
+			if (err)
+				goto out;
+		}
+
+		err = crypto_shash_update(desc, prefix, sizeof(prefix));
+		if (err)
+			goto out;
+
+		err = crypto_shash_update(desc, info, infolen);
+		if (err)
+			goto out;
+
+		BUILD_BUG_ON(sizeof(counter) != 1);
+		if (okmlen - i < HKDF_HASHLEN) {
+			err = crypto_shash_finup(desc, &counter, 1, tmp);
+			if (err)
+				goto out;
+			memcpy(&okm[i], tmp, okmlen - i);
+			memzero_explicit(tmp, sizeof(tmp));
+		} else {
+			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
+			if (err)
+				goto out;
+		}
+		counter++;
+		prev = &okm[i];
+	}
+	err = 0;
+out:
+	if (unlikely(err))
+		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
+	shash_desc_zero(desc);
+	return err;
+}
+
+void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf)
+{
+	crypto_free_shash(hkdf->hmac_tfm);
+}
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 10/16] fscrypt: v2 encryption policy support
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (8 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 21:17   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 11/16] fscrypt: allow unprivileged users to add/remove keys for v2 policies Eric Biggers
                   ` (5 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Add a new fscrypt policy version, "v2".  It has the following changes
from the original policy version, which we call "v1" (*):

- Master keys (the user-provided encryption keys) are only ever used as
  input to HKDF-SHA512.  This is more flexible and less error-prone, and
  it avoids the quirks and limitations of the AES-128-ECB based KDF.
  Three classes of cryptographically isolated subkeys are defined:

    - Per-file keys, like used in v1 policies except for the new KDF.

    - Per-mode keys.  These implement the semantics of the DIRECT_KEY
      flag, which for v1 policies made the master key be used directly.
      These are also planned to be used for inline encryption when
      support for it is added.

    - Key identifiers (see below).

- Each master key is identified by a 16-byte master_key_identifier,
  which is derived from the key itself using HKDF-SHA512.  This prevents
  users from associating the wrong key with an encrypted file or
  directory.  This was easily possible with v1 policies, which
  identified the key by an arbitrary 8-byte master_key_descriptor.

- The key must be provided in the filesystem-level keyring, not in a
  process-subscribed keyring.

The following UAPI additions are made:

- The existing ioctl FS_IOC_SET_ENCRYPTION_POLICY can now be passed a
  fscrypt_policy_v2 to set a v2 encryption policy.  It's disambiguated
  from fscrypt_policy/fscrypt_policy_v1 by the version code prefix.

- A new ioctl FS_IOC_GET_ENCRYPTION_POLICY_EX is added.  It allows
  getting the v1 or v2 encryption policy of an encrypted file or
  directory.  The existing FS_IOC_GET_ENCRYPTION_POLICY ioctl could not
  be used because it did not have a way for userspace to indicate which
  policy structure is expected.  The new ioctl includes a size field, so
  it is extensible to future fscrypt policy versions.

- The ioctls FS_IOC_ADD_ENCRYPTION_KEY, FS_IOC_REMOVE_ENCRYPTION_KEY,
  and FS_IOC_GET_ENCRYPTION_KEY_STATUS now support managing keys for v2
  encryption policies.  Such keys are kept logically separate from keys
  for v1 encryption policies, and are identified by 'identifier' rather
  than by 'descriptor'.  The 'identifier' need not be provided when
  adding a key, since the kernel will calculate it anyway.

This patch temporarily keeps adding/removing v2 policy keys behind the
same permission check done for adding/removing v1 policy keys:
capable(CAP_SYS_ADMIN).  However, the next patch will carefully take
advantage of the cryptographically secure master_key_identifier to allow
non-root users to add/remove v2 policy keys, thus providing a full
replacement for v1 policies.

(*) Actually, in the API fscrypt_policy::version is 0 while on-disk
    fscrypt_context::format is 1.  But I believe it makes the most sense
    to advance both to '2' to have them be in sync, and to consider the
    numbering to start at 1 except for the API quirk.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/crypto.c           |   2 +-
 fs/crypto/fname.c            |   3 +-
 fs/crypto/fscrypt_private.h  | 183 ++++++++++++---
 fs/crypto/keyring.c          |  37 ++-
 fs/crypto/keysetup.c         | 180 +++++++++++----
 fs/crypto/keysetup_legacy.c  |  18 +-
 fs/crypto/policy.c           | 422 ++++++++++++++++++++++++++---------
 include/linux/fscrypt.h      |   9 +-
 include/uapi/linux/fscrypt.h |  43 +++-
 9 files changed, 707 insertions(+), 190 deletions(-)

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index 65ca077e8d585..32a7ad0098cc2 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -141,7 +141,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 	memset(iv, 0, ci->ci_mode->ivsize);
 	iv->lblk_num = cpu_to_le64(lblk_num);
 
-	if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
+	if (fscrypt_is_direct_key_policy(&ci->ci_policy))
 		memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 
 	if (ci->ci_essiv_tfm != NULL)
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index f4977d44d69b8..3da3707c10e33 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -181,7 +181,8 @@ static int base64_decode(const char *src, int len, u8 *dst)
 bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
 				  u32 max_len, u32 *encrypted_len_ret)
 {
-	int padding = 4 << (inode->i_crypt_info->ci_flags &
+	const struct fscrypt_info *ci = inode->i_crypt_info;
+	int padding = 4 << (fscrypt_policy_flags(&ci->ci_policy) &
 			    FSCRYPT_POLICY_FLAGS_PAD_MASK);
 	u32 encrypted_len;
 
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 92567efec2cd5..1e596cfd085bf 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -20,27 +20,127 @@
 
 #define FSCRYPT_MIN_KEY_SIZE		16
 
-/**
- * Encryption context for inode
- *
- * Protector format:
- *  1 byte: Protector format (1 = this version)
- *  1 byte: File contents encryption mode
- *  1 byte: File names encryption mode
- *  1 byte: Flags
- *  8 bytes: Master Key descriptor
- *  16 bytes: Encryption Key derivation nonce
- */
-struct fscrypt_context {
-	u8 format;
+#define FSCRYPT_CONTEXT_V1	1
+#define FSCRYPT_CONTEXT_V2	2
+
+struct fscrypt_context_v1 {
+	u8 version; /* FSCRYPT_CONTEXT_V1 */
 	u8 contents_encryption_mode;
 	u8 filenames_encryption_mode;
 	u8 flags;
 	u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 	u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
-} __packed;
+};
+
+struct fscrypt_context_v2 {
+	u8 version; /* FSCRYPT_CONTEXT_V2 */
+	u8 contents_encryption_mode;
+	u8 filenames_encryption_mode;
+	u8 flags;
+	u8 __reserved[4];
+	u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+	u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
+};
+
+/**
+ * fscrypt_context - the encryption context of an inode
+ *
+ * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
+ * encrypted file usually in a hidden extended attribute.  It contains the
+ * fields from the fscrypt_policy, in order to identify the encryption algorithm
+ * and key with which the file is encrypted.  It also contains a nonce that was
+ * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
+ * to cause different files to be encrypted differently.
+ */
+union fscrypt_context {
+	u8 version;
+	struct fscrypt_context_v1 v1;
+	struct fscrypt_context_v2 v2;
+};
+
+/*
+ * Return the size expected for the given fscrypt_context based on its version
+ * number, or 0 if the context version is unrecognized.
+ */
+static inline int fscrypt_context_size(const union fscrypt_context *ctx)
+{
+	switch (ctx->version) {
+	case FSCRYPT_CONTEXT_V1:
+		BUILD_BUG_ON(sizeof(ctx->v1) != 28);
+		return sizeof(ctx->v1);
+	case FSCRYPT_CONTEXT_V2:
+		BUILD_BUG_ON(sizeof(ctx->v2) != 40);
+		return sizeof(ctx->v2);
+	}
+	return 0;
+}
+
+#undef fscrypt_policy
+union fscrypt_policy {
+	__u8 version;
+	struct fscrypt_policy_v1 v1;
+	struct fscrypt_policy_v2 v2;
+};
+
+/*
+ * Return the size expected for the given fscrypt_policy based on its version
+ * number, or 0 if the policy version is unrecognized.
+ */
+static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return sizeof(policy->v1);
+	case FSCRYPT_POLICY_V2:
+		return sizeof(policy->v2);
+	}
+	return 0;
+}
 
-#define FS_ENCRYPTION_CONTEXT_FORMAT_V1		1
+/* Return the contents encryption mode of a valid encryption policy */
+static inline u8
+fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return policy->v1.contents_encryption_mode;
+	case FSCRYPT_POLICY_V2:
+		return policy->v2.contents_encryption_mode;
+	}
+	BUG();
+}
+
+/* Return the filenames encryption mode of a valid encryption policy */
+static inline u8
+fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return policy->v1.filenames_encryption_mode;
+	case FSCRYPT_POLICY_V2:
+		return policy->v2.filenames_encryption_mode;
+	}
+	BUG();
+}
+
+/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
+static inline u8
+fscrypt_policy_flags(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return policy->v1.flags;
+	case FSCRYPT_POLICY_V2:
+		return policy->v2.flags;
+	}
+	BUG();
+}
+
+static inline bool
+fscrypt_is_direct_key_policy(const union fscrypt_policy *policy)
+{
+	return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY;
+}
 
 /**
  * For encrypted symlinks, the ciphertext length is stored at the beginning
@@ -70,8 +170,8 @@ struct fscrypt_info {
 	struct crypto_cipher *ci_essiv_tfm;
 
 	/*
-	 * Encryption mode used for this inode.  It corresponds to either
-	 * ci_data_mode or ci_filename_mode, depending on the inode type.
+	 * Encryption mode used for this inode.  It corresponds to either the
+	 * contents or filenames encryption mode, depending on the inode type.
 	 */
 	struct fscrypt_mode *ci_mode;
 
@@ -97,11 +197,10 @@ struct fscrypt_info {
 	 */
 	struct fscrypt_direct_key *ci_direct_key;
 
-	/* fields from the fscrypt_context */
-	u8 ci_data_mode;
-	u8 ci_filename_mode;
-	u8 ci_flags;
-	u8 ci_master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+	/* The encryption policy used by this inode */
+	union fscrypt_policy ci_policy;
+
+	/* This inode's nonce, copied from the fscrypt_context */
 	u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
 };
 
@@ -181,6 +280,17 @@ struct fscrypt_hkdf {
 extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 			     unsigned int master_key_size);
 
+/*
+ * The list of contexts in which fscrypt uses HKDF.  These values are used as
+ * the first byte of the HKDF application-specific info string to guarantee that
+ * info strings are never repeated between contexts.  This ensures that all HKDF
+ * outputs are unique and cryptographically isolated, i.e. knowledge of one
+ * output doesn't reveal another.
+ */
+#define HKDF_CONTEXT_KEY_IDENTIFIER	1
+#define HKDF_CONTEXT_PER_FILE_KEY	2
+#define HKDF_CONTEXT_PER_MODE_KEY	3
+
 extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
 			       const u8 *info, unsigned int infolen,
 			       u8 *okm, unsigned int okmlen);
@@ -194,10 +304,16 @@ extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
  */
 struct fscrypt_master_key_secret {
 
-	/* Size of the raw key in bytes */
+	/*
+	 * For v2 policy keys: HKDF context keyed by this master key.
+	 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
+	 */
+	struct fscrypt_hkdf	hkdf;
+
+	/* Size of the raw key in bytes.  Set even if ->raw isn't set. */
 	u32			size;
 
-	/* The raw key */
+	/* For v1 policy keys: the raw key.  Wiped for v2 policy keys. */
 	u8			raw[FSCRYPT_MAX_KEY_SIZE];
 
 } __randomize_layout;
@@ -223,7 +339,12 @@ struct fscrypt_master_key {
 	 */
 	struct fscrypt_master_key_secret	mk_secret;
 
-	/* Arbitrary key descriptor which was assigned by userspace */
+	/*
+	 * For v1 policy keys: an arbitrary key descriptor which was assigned by
+	 * userspace (->descriptor).
+	 *
+	 * For v2 policy keys: a cryptographic hash of this key (->identifier).
+	 */
 	struct fscrypt_key_specifier		mk_spec;
 
 	/*
@@ -242,6 +363,9 @@ struct fscrypt_master_key {
 	struct list_head	mk_decrypted_inodes;
 	spinlock_t		mk_decrypted_inodes_lock;
 
+	/* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */
+	struct crypto_skcipher	*mk_mode_keys[__FSCRYPT_MODE_MAX + 1];
+
 } __randomize_layout;
 
 static inline bool
@@ -296,5 +420,14 @@ extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
 
 extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
 					struct fscrypt_info *ci);
+/* policy.c */
+
+extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
+				   const union fscrypt_policy *policy2);
+extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
+				     const struct inode *inode);
+extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
+				       const union fscrypt_context *ctx_u,
+				       int ctx_size);
 
 #endif /* _FSCRYPT_PRIVATE_H */
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index 02a94d7cc739e..56e085c2ed8c6 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -14,6 +14,7 @@
  * - FS_IOC_GET_ENCRYPTION_KEY_STATUS: get key status
  */
 
+#include <crypto/skcipher.h>
 #include <linux/key-type.h>
 #include <linux/seq_file.h>
 
@@ -21,6 +22,7 @@
 
 static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret)
 {
+	fscrypt_destroy_hkdf(&secret->hkdf);
 	memzero_explicit(secret, sizeof(*secret));
 }
 
@@ -33,7 +35,13 @@ static void move_master_key_secret(struct fscrypt_master_key_secret *dst,
 
 static void free_master_key(struct fscrypt_master_key *mk)
 {
+	size_t i;
+
 	wipe_master_key_secret(&mk->mk_secret);
+
+	for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
+		crypto_free_skcipher(mk->mk_mode_keys[i]);
+
 	kzfree(mk);
 }
 
@@ -42,6 +50,8 @@ static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
 	switch (spec->type) {
 	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
 		return FSCRYPT_KEY_DESCRIPTOR_SIZE;
+	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
+		return FSCRYPT_KEY_IDENTIFIER_SIZE;
 	}
 	return 0;
 }
@@ -115,7 +125,7 @@ static struct key *search_fscrypt_keyring(struct key *keyring,
 #define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE	\
 	(CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id))
 
-#define FSCRYPT_MK_DESCRIPTION_SIZE	(2 * FSCRYPT_KEY_DESCRIPTOR_SIZE + 1)
+#define FSCRYPT_MK_DESCRIPTION_SIZE	(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1)
 
 static void format_fs_keyring_description(
 			char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
@@ -319,6 +329,31 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 	if (!capable(CAP_SYS_ADMIN))
 		goto out_wipe_secret;
 
+	if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {
+		err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size);
+		if (err)
+			goto out_wipe_secret;
+
+		/*
+		 * Now that the HKDF context is initialized, the raw key is no
+		 * longer needed.
+		 */
+		memzero_explicit(secret.raw, secret.size);
+
+		/* Calculate the key identifier and return it to userspace. */
+		err = fscrypt_hkdf_expand(&secret.hkdf,
+					  HKDF_CONTEXT_KEY_IDENTIFIER,
+					  NULL, 0, arg.key_spec.u.identifier,
+					  FSCRYPT_KEY_IDENTIFIER_SIZE);
+		if (err)
+			goto out_wipe_secret;
+		err = -EFAULT;
+		if (copy_to_user(uarg->key_spec.u.identifier,
+				 arg.key_spec.u.identifier,
+				 FSCRYPT_KEY_IDENTIFIER_SIZE))
+			goto out_wipe_secret;
+	}
+
 	err = add_master_key(sb, &secret, &arg.key_spec);
 out_wipe_secret:
 	wipe_master_key_secret(&secret);
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 6b35c550e87a4..358883cde0c9e 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -52,20 +52,14 @@ static struct fscrypt_mode available_modes[] = {
 };
 
 static struct fscrypt_mode *
-select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
+select_encryption_mode(const union fscrypt_policy *policy,
+		       const struct inode *inode)
 {
-	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
-		fscrypt_warn(inode,
-			     "Unsupported encryption modes (contents mode %d, filenames mode %d)",
-			     ci->ci_data_mode, ci->ci_filename_mode);
-		return ERR_PTR(-EINVAL);
-	}
-
 	if (S_ISREG(inode->i_mode))
-		return &available_modes[ci->ci_data_mode];
+		return &available_modes[fscrypt_policy_contents_mode(policy)];
 
 	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
-		return &available_modes[ci->ci_filename_mode];
+		return &available_modes[fscrypt_policy_fnames_mode(policy)];
 
 	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
 		  inode->i_ino, (inode->i_mode & S_IFMT));
@@ -216,6 +210,82 @@ int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key)
 	return 0;
 }
 
+static int setup_per_mode_key(struct fscrypt_info *ci,
+			      struct fscrypt_master_key *mk)
+{
+	struct fscrypt_mode *mode = ci->ci_mode;
+	u8 mode_num = mode - available_modes;
+	struct crypto_skcipher *tfm, *prev_tfm;
+	u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
+	int err;
+
+	if (WARN_ON(mode_num >= ARRAY_SIZE(mk->mk_mode_keys)))
+		return -EINVAL;
+
+	/* pairs with cmpxchg() below */
+	tfm = READ_ONCE(mk->mk_mode_keys[mode_num]);
+	if (likely(tfm != NULL))
+		goto done;
+
+	BUILD_BUG_ON(sizeof(mode_num) != 1);
+	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
+				  HKDF_CONTEXT_PER_MODE_KEY,
+				  &mode_num, sizeof(mode_num),
+				  mode_key, mode->keysize);
+	if (err)
+		return err;
+	tfm = fscrypt_allocate_skcipher(mode, mode_key, ci->ci_inode);
+	memzero_explicit(mode_key, mode->keysize);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	/* pairs with READ_ONCE() above */
+	prev_tfm = cmpxchg(&mk->mk_mode_keys[mode_num], NULL, tfm);
+	if (prev_tfm != NULL) {
+		crypto_free_skcipher(tfm);
+		tfm = prev_tfm;
+	}
+done:
+	ci->ci_ctfm = tfm;
+	return 0;
+}
+
+static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
+				     struct fscrypt_master_key *mk)
+{
+	u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
+	int err;
+
+	if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
+		/*
+		 * DIRECT_KEY: instead of deriving per-file keys, the per-file
+		 * nonce will be included in all the IVs.  But unlike v1
+		 * policies, for v2 policies in this case we don't encrypt with
+		 * the master key directly but rather derive a per-mode key.
+		 * This ensures that the master key is consistently used only
+		 * for HKDF, avoiding key reuse issues.
+		 */
+		if (!fscrypt_mode_supports_direct_key(ci->ci_mode)) {
+			fscrypt_warn(ci->ci_inode,
+				     "Direct key flag not allowed with %s",
+				     ci->ci_mode->friendly_name);
+			return -EINVAL;
+		}
+		return setup_per_mode_key(ci, mk);
+	}
+
+	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
+				  HKDF_CONTEXT_PER_FILE_KEY,
+				  ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE,
+				  derived_key, ci->ci_mode->keysize);
+	if (err)
+		return err;
+
+	err = fscrypt_set_derived_key(ci, derived_key);
+	memzero_explicit(derived_key, ci->ci_mode->keysize);
+	return err;
+}
+
 /*
  * Find the master key, then set up the inode's actual encryption key.
  *
@@ -234,15 +304,30 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 	struct fscrypt_key_specifier mk_spec;
 	int err;
 
-	mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
-	memcpy(mk_spec.u.descriptor, ci->ci_master_key_descriptor,
-	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	if (ci->ci_policy.version == FSCRYPT_POLICY_V1) {
+		mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+		memcpy(mk_spec.u.descriptor,
+		       ci->ci_policy.v1.master_key_descriptor,
+		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	} else {
+		mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+		memcpy(mk_spec.u.identifier,
+		       ci->ci_policy.v2.master_key_identifier,
+		       FSCRYPT_KEY_IDENTIFIER_SIZE);
+	}
 
 	key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
 	if (IS_ERR(key)) {
-		if (key != ERR_PTR(-ENOKEY))
+		if (key != ERR_PTR(-ENOKEY) ||
+		    ci->ci_policy.version != FSCRYPT_POLICY_V1)
 			return PTR_ERR(key);
 
+		/*
+		 * As a legacy fallback for v1 policies, search for the key in
+		 * the current task's subscribed keyrings too.  Don't move this
+		 * to before the search of ->s_master_keys, since users
+		 * shouldn't be able to override filesystem-level keys.
+		 */
 		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
 	}
 
@@ -255,6 +340,12 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 		goto out_release_key;
 	}
 
+	/*
+	 * Require that the master key be at least as long as the derived key.
+	 * Otherwise, the derived key cannot possibly contain as much entropy as
+	 * that required by the encryption mode it will be used for.  For v1
+	 * policies it's also required for the KDF to work at all.
+	 */
 	if (mk->mk_secret.size < ci->ci_mode->keysize) {
 		fscrypt_warn(NULL,
 			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
@@ -264,7 +355,10 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 		goto out_release_key;
 	}
 
-	err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+	if (ci->ci_policy.version == FSCRYPT_POLICY_V1)
+		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+	else
+		err = fscrypt_setup_v2_file_key(ci, mk);
 	if (err)
 		goto out_release_key;
 
@@ -286,7 +380,8 @@ static void put_crypt_info(struct fscrypt_info *ci)
 
 	if (ci->ci_direct_key) {
 		fscrypt_put_direct_key(ci->ci_direct_key);
-	} else {
+	} else if ((ci->ci_ctfm != NULL || ci->ci_essiv_tfm != NULL) &&
+		   !fscrypt_is_direct_key_policy(&ci->ci_policy)) {
 		crypto_free_skcipher(ci->ci_ctfm);
 		crypto_free_cipher(ci->ci_essiv_tfm);
 	}
@@ -316,7 +411,7 @@ static void put_crypt_info(struct fscrypt_info *ci)
 int fscrypt_get_encryption_info(struct inode *inode)
 {
 	struct fscrypt_info *crypt_info;
-	struct fscrypt_context ctx;
+	union fscrypt_context ctx;
 	struct fscrypt_mode *mode;
 	struct key *master_key = NULL;
 	int res;
@@ -335,27 +430,12 @@ int fscrypt_get_encryption_info(struct inode *inode)
 			return res;
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));
-		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-		ctx.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
-		ctx.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
-		memset(ctx.master_key_descriptor, 0x42,
+		ctx.version = FSCRYPT_CONTEXT_V1;
+		ctx.v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
+		ctx.v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
+		memset(ctx.v1.master_key_descriptor, 0x42,
 		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	} else if (res != sizeof(ctx)) {
-		fscrypt_warn(inode,
-			     "Unknown encryption context size (%d bytes)", res);
-		return -EINVAL;
-	}
-
-	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) {
-		fscrypt_warn(inode, "Unknown encryption context version (%d)",
-			     ctx.format);
-		return -EINVAL;
-	}
-
-	if (ctx.flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
-		fscrypt_warn(inode, "Unknown encryption context flags (0x%02x)",
-			     ctx.flags);
-		return -EINVAL;
+		res = sizeof(ctx.v1);
 	}
 
 	crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
@@ -364,14 +444,26 @@ int fscrypt_get_encryption_info(struct inode *inode)
 
 	crypt_info->ci_inode = inode;
 
-	crypt_info->ci_flags = ctx.flags;
-	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
-	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
-	memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
-	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	res = fscrypt_policy_from_context(&crypt_info->ci_policy, &ctx, res);
+	if (res) {
+		fscrypt_warn(inode,
+			     "Unrecognized or corrupt encryption context");
+		goto out;
+	}
+
+	if (ctx.version == FSCRYPT_CONTEXT_V1)
+		memcpy(crypt_info->ci_nonce, ctx.v1.nonce,
+		       FS_KEY_DERIVATION_NONCE_SIZE);
+	else
+		memcpy(crypt_info->ci_nonce, ctx.v2.nonce,
+		       FS_KEY_DERIVATION_NONCE_SIZE);
+
+	if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) {
+		res = -EINVAL;
+		goto out;
+	}
 
-	mode = select_encryption_mode(crypt_info, inode);
+	mode = select_encryption_mode(&crypt_info->ci_policy, inode);
 	if (IS_ERR(mode)) {
 		res = PTR_ERR(mode);
 		goto out;
diff --git a/fs/crypto/keysetup_legacy.c b/fs/crypto/keysetup_legacy.c
index b3c06322afa3c..67a85415e4b17 100644
--- a/fs/crypto/keysetup_legacy.c
+++ b/fs/crypto/keysetup_legacy.c
@@ -189,12 +189,13 @@ find_or_insert_direct_key(struct fscrypt_direct_key *to_insert,
 	 */
 
 	BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
+	memcpy(&hash_key, ci->ci_policy.v1.master_key_descriptor,
+	       sizeof(hash_key));
 
 	spin_lock(&fscrypt_direct_keys_lock);
 	hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) {
-		if (memcmp(ci->ci_master_key_descriptor, dk->dk_descriptor,
-			   FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0)
+		if (memcmp(ci->ci_policy.v1.master_key_descriptor,
+			   dk->dk_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0)
 			continue;
 		if (ci->ci_mode != dk->dk_mode)
 			continue;
@@ -237,7 +238,7 @@ fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key)
 		dk->dk_ctfm = NULL;
 		goto err_free_dk;
 	}
-	memcpy(dk->dk_descriptor, ci->ci_master_key_descriptor,
+	memcpy(dk->dk_descriptor, ci->ci_policy.v1.master_key_descriptor,
 	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
 	memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize);
 
@@ -262,7 +263,8 @@ static int setup_v1_file_key_direct(struct fscrypt_info *ci,
 		return -EINVAL;
 	}
 
-	if (ci->ci_data_mode != ci->ci_filename_mode) {
+	if (ci->ci_policy.v1.contents_encryption_mode !=
+	    ci->ci_policy.v1.filenames_encryption_mode) {
 		fscrypt_warn(ci->ci_inode,
 			     "Direct key mode not allowed with different contents and filenames modes");
 		return -EINVAL;
@@ -308,7 +310,7 @@ static int setup_v1_file_key_derived(struct fscrypt_info *ci,
 
 int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key)
 {
-	if (ci->ci_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
+	if (ci->ci_policy.v1.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
 		return setup_v1_file_key_direct(ci, raw_master_key);
 	else
 		return setup_v1_file_key_derived(ci, raw_master_key);
@@ -321,11 +323,11 @@ int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci)
 	int err;
 
 	key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX,
-					ci->ci_master_key_descriptor,
+					ci->ci_policy.v1.master_key_descriptor,
 					ci->ci_mode->keysize, &payload);
 	if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) {
 		key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix,
-						ci->ci_master_key_descriptor,
+						ci->ci_policy.v1.master_key_descriptor,
 						ci->ci_mode->keysize, &payload);
 	}
 	if (IS_ERR(key))
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index da7ae9c8b4ad0..0141d338c1fdb 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -5,8 +5,9 @@
  * Copyright (C) 2015, Google, Inc.
  * Copyright (C) 2015, Motorola Mobility.
  *
- * Written by Michael Halcrow, 2015.
+ * Originally written by Michael Halcrow, 2015.
  * Modified by Jaegeuk Kim, 2015.
+ * Modified by Eric Biggers, 2019 for v2 policy support.
  */
 
 #include <linux/random.h>
@@ -14,70 +15,291 @@
 #include <linux/mount.h>
 #include "fscrypt_private.h"
 
-/*
- * check whether an encryption policy is consistent with an encryption context
+/**
+ * fscrypt_policies_equal - check whether two encryption policies are the same
+ *
+ * Return: %true if equal, else %false
  */
-static bool is_encryption_context_consistent_with_policy(
-				const struct fscrypt_context *ctx,
-				const struct fscrypt_policy *policy)
+bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
+			    const union fscrypt_policy *policy2)
 {
-	return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
-		      FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
-		(ctx->flags == policy->flags) &&
-		(ctx->contents_encryption_mode ==
-		 policy->contents_encryption_mode) &&
-		(ctx->filenames_encryption_mode ==
-		 policy->filenames_encryption_mode);
+	if (policy1->version != policy2->version)
+		return false;
+
+	return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
 }
 
-static int create_encryption_context_from_policy(struct inode *inode,
-				const struct fscrypt_policy *policy)
+/**
+ * fscrypt_supported_policy - check whether an encryption policy is supported
+ *
+ * Given an encryption policy, check whether all its encryption modes and other
+ * settings are supported by this kernel.  (But we don't currently don't check
+ * for crypto API support here, so attempting to use an algorithm not configured
+ * into the crypto API will still fail later.)
+ *
+ * Return: %true if supported, else %false
+ */
+bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
+			      const struct inode *inode)
 {
-	struct fscrypt_context ctx;
+	switch (policy_u->version) {
+	case FSCRYPT_POLICY_V1: {
+		const struct fscrypt_policy_v1 *policy = &policy_u->v1;
+
+		if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
+					     policy->filenames_encryption_mode)) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption modes (contents %d, filenames %d)",
+				     policy->contents_encryption_mode,
+				     policy->filenames_encryption_mode);
+			return false;
+		}
+
+		if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption flags (0x%02x)",
+				     policy->flags);
+			return false;
+		}
+
+		return true;
+	}
+	case FSCRYPT_POLICY_V2: {
+		const struct fscrypt_policy_v2 *policy = &policy_u->v2;
+
+		if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
+					     policy->filenames_encryption_mode)) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption modes (contents %d, filenames %d)",
+				     policy->contents_encryption_mode,
+				     policy->filenames_encryption_mode);
+			return false;
+		}
+
+		if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption flags (0x%02x)",
+				     policy->flags);
+			return false;
+		}
+
+		if (memchr_inv(policy->__reserved, 0,
+			       sizeof(policy->__reserved))) {
+			fscrypt_warn(inode,
+				     "Reserved bits set in encryption policy");
+			return false;
+		}
+
+		return true;
+	}
+	}
+	return false;
+}
+
+/**
+ * fscrypt_new_context_from_policy - create a new fscrypt_context from a policy
+ *
+ * Create an fscrypt_context for an inode that is being assigned the given
+ * encryption policy.  A new nonce is randomly generated.
+ *
+ * Return: the size of the new context in bytes.
+ */
+static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u,
+					   const union fscrypt_policy *policy_u)
+{
+	memset(ctx_u, 0, sizeof(*ctx_u));
+
+	switch (policy_u->version) {
+	case FSCRYPT_POLICY_V1: {
+		const struct fscrypt_policy_v1 *policy = &policy_u->v1;
+		struct fscrypt_context_v1 *ctx = &ctx_u->v1;
+
+		ctx->version = FSCRYPT_CONTEXT_V1;
+		ctx->contents_encryption_mode =
+			policy->contents_encryption_mode;
+		ctx->filenames_encryption_mode =
+			policy->filenames_encryption_mode;
+		ctx->flags = policy->flags;
+		memcpy(ctx->master_key_descriptor,
+		       policy->master_key_descriptor,
+		       sizeof(ctx->master_key_descriptor));
+		get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
+		return sizeof(*ctx);
+	}
+	case FSCRYPT_POLICY_V2: {
+		const struct fscrypt_policy_v2 *policy = &policy_u->v2;
+		struct fscrypt_context_v2 *ctx = &ctx_u->v2;
+
+		ctx->version = FSCRYPT_CONTEXT_V2;
+		ctx->contents_encryption_mode =
+			policy->contents_encryption_mode;
+		ctx->filenames_encryption_mode =
+			policy->filenames_encryption_mode;
+		ctx->flags = policy->flags;
+		memcpy(ctx->master_key_identifier,
+		       policy->master_key_identifier,
+		       sizeof(ctx->master_key_identifier));
+		get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
+		return sizeof(*ctx);
+	}
+	}
+	BUG();
+}
 
-	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
-					FSCRYPT_KEY_DESCRIPTOR_SIZE);
+/**
+ * fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy
+ *
+ * Given an fscrypt_context, build the corresponding fscrypt_policy.
+ *
+ * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
+ * version number or size.
+ *
+ * This does *not* validate the settings within the policy itself, e.g. the
+ * modes, flags, and reserved bits.  Use fscrypt_supported_policy() for that.
+ */
+int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
+				const union fscrypt_context *ctx_u,
+				int ctx_size)
+{
+	memset(policy_u, 0, sizeof(*policy_u));
 
-	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
-				     policy->filenames_encryption_mode))
+	if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u))
 		return -EINVAL;
 
-	if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID)
+	switch (ctx_u->version) {
+	case FSCRYPT_CONTEXT_V1: {
+		const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
+		struct fscrypt_policy_v1 *policy = &policy_u->v1;
+
+		policy->version = FSCRYPT_POLICY_V1;
+		policy->contents_encryption_mode =
+			ctx->contents_encryption_mode;
+		policy->filenames_encryption_mode =
+			ctx->filenames_encryption_mode;
+		policy->flags = ctx->flags;
+		memcpy(policy->master_key_descriptor,
+		       ctx->master_key_descriptor,
+		       sizeof(policy->master_key_descriptor));
+		return 0;
+	}
+	case FSCRYPT_CONTEXT_V2: {
+		const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
+		struct fscrypt_policy_v2 *policy = &policy_u->v2;
+
+		policy->version = FSCRYPT_POLICY_V2;
+		policy->contents_encryption_mode =
+			ctx->contents_encryption_mode;
+		policy->filenames_encryption_mode =
+			ctx->filenames_encryption_mode;
+		policy->flags = ctx->flags;
+		memcpy(policy->__reserved, ctx->__reserved,
+		       sizeof(policy->__reserved));
+		memcpy(policy->master_key_identifier,
+		       ctx->master_key_identifier,
+		       sizeof(policy->master_key_identifier));
+		return 0;
+	}
+	}
+	/* unreachable */
+	return -EINVAL;
+}
+
+/* Retrieve an inode's encryption policy */
+static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
+{
+	const struct fscrypt_info *ci;
+	union fscrypt_context ctx;
+	int ret;
+
+	ci = READ_ONCE(inode->i_crypt_info);
+	if (ci) {
+		/* key available, use the cached policy */
+		*policy = ci->ci_policy;
+		return 0;
+	}
+
+	if (!IS_ENCRYPTED(inode))
+		return -ENODATA;
+
+	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+	if (ret < 0)
+		return (ret == -ERANGE) ? -EINVAL : ret;
+
+	return fscrypt_policy_from_context(policy, &ctx, ret);
+}
+
+static int set_encryption_policy(struct inode *inode,
+				 const union fscrypt_policy *policy)
+{
+	union fscrypt_context ctx;
+	int ctxsize;
+
+	if (!fscrypt_supported_policy(policy, inode))
 		return -EINVAL;
 
-	ctx.contents_encryption_mode = policy->contents_encryption_mode;
-	ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
-	ctx.flags = policy->flags;
-	BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
-	get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	if (policy->version == FSCRYPT_POLICY_V1) {
+		/*
+		 * The original encryption policy version provided no way of
+		 * verifying that the correct master key was supplied, which was
+		 * insecure in scenarios where multiple users have access to the
+		 * same encrypted files (even just read-only access).  The new
+		 * encryption policy version fixes this and also implies use of
+		 * an improved key derivation function and allows non-root users
+		 * to securely remove keys.  So as long as compatibility with
+		 * old kernels isn't required, it is recommended to use the new
+		 * policy version for all new encrypted directories.
+		 */
+		pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
+			     current->comm, current->pid);
+	}
 
-	return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
+	ctxsize = fscrypt_new_context_from_policy(&ctx, policy);
+
+	return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
 }
 
 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 {
-	struct fscrypt_policy policy;
+	union fscrypt_policy policy;
+	union fscrypt_policy existing_policy;
 	struct inode *inode = file_inode(filp);
+	u8 version;
+	int size;
 	int ret;
-	struct fscrypt_context ctx;
 
-	if (copy_from_user(&policy, arg, sizeof(policy)))
+	if (get_user(policy.version, (const u8 __user *)arg))
 		return -EFAULT;
 
+	size = fscrypt_policy_size(&policy);
+	if (size <= 0)
+		return -EINVAL;
+
+	/*
+	 * We should just copy the remaining 'size - 1' bytes here, but a
+	 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
+	 * think that size can be 0 here (despite the check above!) *and* that
+	 * it's a compile-time constant.  Thus it would think copy_from_user()
+	 * is passed compile-time constant ULONG_MAX, causing the compile-time
+	 * buffer overflow check to fail, breaking the build. This only occurred
+	 * when building an i386 kernel with -Os and branch profiling enabled.
+	 *
+	 * Work around it by just copying the first byte again...
+	 */
+	version = policy.version;
+	if (copy_from_user(&policy, arg, size))
+		return -EFAULT;
+	policy.version = version;
+
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
-	if (policy.version != 0)
-		return -EINVAL;
-
 	ret = mnt_want_write_file(filp);
 	if (ret)
 		return ret;
 
 	inode_lock(inode);
 
-	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+	ret = fscrypt_get_policy(inode, &existing_policy);
 	if (ret == -ENODATA) {
 		if (!S_ISDIR(inode->i_mode))
 			ret = -ENOTDIR;
@@ -86,14 +308,10 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 		else if (!inode->i_sb->s_cop->empty_dir(inode))
 			ret = -ENOTEMPTY;
 		else
-			ret = create_encryption_context_from_policy(inode,
-								    &policy);
-	} else if (ret == sizeof(ctx) &&
-		   is_encryption_context_consistent_with_policy(&ctx,
-								&policy)) {
-		/* The file already uses the same encryption policy. */
-		ret = 0;
-	} else if (ret >= 0 || ret == -ERANGE) {
+			ret = set_encryption_policy(inode, &policy);
+	} else if (ret == -EINVAL ||
+		   (ret == 0 && !fscrypt_policies_equal(&policy,
+							&existing_policy))) {
 		/* The file already uses a different encryption policy. */
 		ret = -EEXIST;
 	}
@@ -105,37 +323,57 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 }
 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
 
+/* Original ioctl version; can only get the original policy version */
 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 {
-	struct inode *inode = file_inode(filp);
-	struct fscrypt_context ctx;
-	struct fscrypt_policy policy;
-	int res;
+	union fscrypt_policy policy;
+	int err;
 
-	if (!IS_ENCRYPTED(inode))
-		return -ENODATA;
+	err = fscrypt_get_policy(file_inode(filp), &policy);
+	if (err)
+		return err;
 
-	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
-	if (res < 0 && res != -ERANGE)
-		return res;
-	if (res != sizeof(ctx))
-		return -EINVAL;
-	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
+	if (policy.version != FSCRYPT_POLICY_V1)
 		return -EINVAL;
 
-	policy.version = 0;
-	policy.contents_encryption_mode = ctx.contents_encryption_mode;
-	policy.filenames_encryption_mode = ctx.filenames_encryption_mode;
-	policy.flags = ctx.flags;
-	memcpy(policy.master_key_descriptor, ctx.master_key_descriptor,
-				FSCRYPT_KEY_DESCRIPTOR_SIZE);
-
-	if (copy_to_user(arg, &policy, sizeof(policy)))
+	if (copy_to_user(arg, &policy, sizeof(policy.v1)))
 		return -EFAULT;
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
 
+/* Extended ioctl version; can get policies of any version */
+int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
+{
+	struct fscrypt_get_policy_ex_arg arg;
+	union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
+	size_t policy_size;
+	int err;
+
+	/* arg is policy_size, then policy */
+	BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
+	BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
+		     offsetof(typeof(arg), policy));
+	BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
+
+	err = fscrypt_get_policy(file_inode(filp), policy);
+	if (err)
+		return err;
+	policy_size = fscrypt_policy_size(policy);
+
+	if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
+		return -EFAULT;
+
+	if (policy_size > arg.policy_size)
+		return -EOVERFLOW;
+	arg.policy_size = policy_size;
+
+	if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
+		return -EFAULT;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
+
 /**
  * fscrypt_has_permitted_context() - is a file's encryption policy permitted
  *				     within its directory?
@@ -157,10 +395,8 @@ EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
  */
 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 {
-	const struct fscrypt_operations *cops = parent->i_sb->s_cop;
-	const struct fscrypt_info *parent_ci, *child_ci;
-	struct fscrypt_context parent_ctx, child_ctx;
-	int res;
+	union fscrypt_policy parent_policy, child_policy;
+	int err;
 
 	/* No restrictions on file types which are never encrypted */
 	if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
@@ -190,41 +426,22 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 	 * In any case, if an unexpected error occurs, fall back to "forbidden".
 	 */
 
-	res = fscrypt_get_encryption_info(parent);
-	if (res)
+	err = fscrypt_get_encryption_info(parent);
+	if (err)
 		return 0;
-	res = fscrypt_get_encryption_info(child);
-	if (res)
+	err = fscrypt_get_encryption_info(child);
+	if (err)
 		return 0;
-	parent_ci = READ_ONCE(parent->i_crypt_info);
-	child_ci = READ_ONCE(child->i_crypt_info);
-
-	if (parent_ci && child_ci) {
-		return memcmp(parent_ci->ci_master_key_descriptor,
-			      child_ci->ci_master_key_descriptor,
-			      FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
-			(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
-			(parent_ci->ci_filename_mode ==
-			 child_ci->ci_filename_mode) &&
-			(parent_ci->ci_flags == child_ci->ci_flags);
-	}
 
-	res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx));
-	if (res != sizeof(parent_ctx))
+	err = fscrypt_get_policy(parent, &parent_policy);
+	if (err)
 		return 0;
 
-	res = cops->get_context(child, &child_ctx, sizeof(child_ctx));
-	if (res != sizeof(child_ctx))
+	err = fscrypt_get_policy(child, &child_policy);
+	if (err)
 		return 0;
 
-	return memcmp(parent_ctx.master_key_descriptor,
-		      child_ctx.master_key_descriptor,
-		      FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
-		(parent_ctx.contents_encryption_mode ==
-		 child_ctx.contents_encryption_mode) &&
-		(parent_ctx.filenames_encryption_mode ==
-		 child_ctx.filenames_encryption_mode) &&
-		(parent_ctx.flags == child_ctx.flags);
+	return fscrypt_policies_equal(&parent_policy, &child_policy);
 }
 EXPORT_SYMBOL(fscrypt_has_permitted_context);
 
@@ -240,7 +457,8 @@ EXPORT_SYMBOL(fscrypt_has_permitted_context);
 int fscrypt_inherit_context(struct inode *parent, struct inode *child,
 						void *fs_data, bool preload)
 {
-	struct fscrypt_context ctx;
+	union fscrypt_context ctx;
+	int ctxsize;
 	struct fscrypt_info *ci;
 	int res;
 
@@ -252,16 +470,10 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child,
 	if (ci == NULL)
 		return -ENOKEY;
 
-	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-	ctx.contents_encryption_mode = ci->ci_data_mode;
-	ctx.filenames_encryption_mode = ci->ci_filename_mode;
-	ctx.flags = ci->ci_flags;
-	memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor,
-	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
-	get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy);
+
 	BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
-	res = parent->i_sb->s_cop->set_context(child, &ctx,
-						sizeof(ctx), fs_data);
+	res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data);
 	if (res)
 		return res;
 	return preload ? fscrypt_get_encryption_info(child): 0;
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index cf41d2a596b3d..606c0a0f8b828 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -43,7 +43,7 @@ struct fscrypt_name {
 #define fname_len(p)		((p)->disk_name.len)
 
 /* Maximum value for the third parameter of fscrypt_operations.set_context(). */
-#define FSCRYPT_SET_CONTEXT_MAX_SIZE	28
+#define FSCRYPT_SET_CONTEXT_MAX_SIZE	40
 
 #ifdef CONFIG_FS_ENCRYPTION
 /*
@@ -135,6 +135,7 @@ extern void fscrypt_free_bounce_page(struct page *bounce_page);
 /* policy.c */
 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
 extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
+extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *);
 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 					void *, bool);
@@ -361,6 +362,12 @@ static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 	return -EOPNOTSUPP;
 }
 
+static inline int fscrypt_ioctl_get_policy_ex(struct file *filp,
+					      void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int fscrypt_has_permitted_context(struct inode *parent,
 						struct inode *child)
 {
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 4f507f8d12261..78811564c95f1 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -10,15 +10,13 @@
 
 #include <linux/types.h>
 
-#define FSCRYPT_KEY_DESCRIPTOR_SIZE	8
-
 /* Encryption policy flags */
 #define FSCRYPT_POLICY_FLAGS_PAD_4		0x00
 #define FSCRYPT_POLICY_FLAGS_PAD_8		0x01
 #define FSCRYPT_POLICY_FLAGS_PAD_16		0x02
 #define FSCRYPT_POLICY_FLAGS_PAD_32		0x03
 #define FSCRYPT_POLICY_FLAGS_PAD_MASK		0x03
-#define FSCRYPT_POLICY_FLAG_DIRECT_KEY		0x04	/* use master key directly */
+#define FSCRYPT_POLICY_FLAG_DIRECT_KEY		0x04
 #define FSCRYPT_POLICY_FLAGS_VALID		0x07
 
 /* Encryption algorithms */
@@ -27,14 +25,24 @@
 #define FSCRYPT_MODE_AES_128_CBC		5
 #define FSCRYPT_MODE_AES_128_CTS		6
 #define FSCRYPT_MODE_ADIANTUM			9
+#define __FSCRYPT_MODE_MAX			9
 
-struct fscrypt_policy {
+/*
+ * Legacy policy version; ad-hoc KDF and no key verification.
+ * For new encrypted directories, use fscrypt_policy_v2 instead.
+ *
+ * Careful: the .version field for this is actually 0, not 1.
+ */
+#define FSCRYPT_POLICY_V1		0
+#define FSCRYPT_KEY_DESCRIPTOR_SIZE	8
+struct fscrypt_policy_v1 {
 	__u8 version;
 	__u8 contents_encryption_mode;
 	__u8 filenames_encryption_mode;
 	__u8 flags;
 	__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 };
+#define fscrypt_policy	fscrypt_policy_v1
 
 /*
  * Process-subscribed "logon" key description prefix and payload format.
@@ -49,13 +57,39 @@ struct fscrypt_key {
 	__u32 size;
 };
 
+/*
+ * New policy version with HKDF and key verification (recommended).
+ */
+#define FSCRYPT_POLICY_V2		2
+#define FSCRYPT_KEY_IDENTIFIER_SIZE	16
+struct fscrypt_policy_v2 {
+	__u8 version;
+	__u8 contents_encryption_mode;
+	__u8 filenames_encryption_mode;
+	__u8 flags;
+	__u8 __reserved[4];
+	__u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+};
+
+/* Struct passed to FS_IOC_GET_ENCRYPTION_POLICY_EX */
+struct fscrypt_get_policy_ex_arg {
+	__u64 policy_size; /* input/output */
+	union {
+		__u8 version;
+		struct fscrypt_policy_v1 v1;
+		struct fscrypt_policy_v2 v2;
+	} policy; /* output */
+};
+
 struct fscrypt_key_specifier {
 #define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR	1
+#define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER	2
 	__u32 type;
 	__u32 __reserved;
 	union {
 		__u8 __reserved[32]; /* reserve some extra space */
 		__u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+		__u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
 	} u;
 };
 
@@ -90,6 +124,7 @@ struct fscrypt_get_key_status_arg {
 #define FS_IOC_SET_ENCRYPTION_POLICY	  _IOR('f', 19, struct fscrypt_policy)
 #define FS_IOC_GET_ENCRYPTION_PWSALT	  _IOW('f', 20, __u8[16])
 #define FS_IOC_GET_ENCRYPTION_POLICY	  _IOW('f', 21, struct fscrypt_policy)
+#define FS_IOC_GET_ENCRYPTION_POLICY_EX	 _IOWR('f', 22, __u8[9]) /* size + version */
 #define FS_IOC_ADD_ENCRYPTION_KEY	 _IOWR('f', 23, struct fscrypt_add_key_arg)
 #define FS_IOC_REMOVE_ENCRYPTION_KEY	  _IOW('f', 24, struct fscrypt_remove_key_arg)
 #define FS_IOC_GET_ENCRYPTION_KEY_STATUS _IOWR('f', 25, struct fscrypt_get_key_status_arg)
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 11/16] fscrypt: allow unprivileged users to add/remove keys for v2 policies
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (9 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 10/16] fscrypt: v2 encryption policy support Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 21:22   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 12/16] fscrypt: require that key be added when setting a v2 encryption policy Eric Biggers
                   ` (4 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Allow the FS_IOC_ADD_ENCRYPTION_KEY and FS_IOC_REMOVE_ENCRYPTION_KEY
ioctls to be used by non-root users to add and remove encryption keys
from the filesystem-level crypto keyrings, subject to limitations.

Motivation: while privileged fscrypt key management is sufficient for
some users (e.g. Android and Chromium OS, where a privileged process
manages all keys), the old API by design also allows non-root users to
set up and use encrypted directories, and we don't want to regress on
that.  Especially, we don't want to force users to continue using the
old API, running into the visibility mismatch between files and keyrings
and being unable to "lock" encrypted directories.

Intuitively, the ioctls have to be privileged since they manipulate
filesystem-level state.  However, it's actually safe to make them
unprivileged if we very carefully enforce some specific limitations.

First, each key must be identified by a cryptographic hash so that a
user can't add the wrong key for another user's files.  For v2
encryption policies, we use the key_identifier for this.  v1 policies
don't have this, so managing keys for them remains privileged.

Second, each key a user adds is charged to their quota for the keyrings
service.  Thus, a user can't exhaust memory by adding a huge number of
keys.  By default each non-root user is allowed up to 200 keys; this can
be changed using the existing sysctl 'kernel.keys.maxkeys'.

Third, if multiple users add the same key, we keep track of those users
of the key (of which there remains a single copy), and won't really
remove the key, i.e. "lock" the encrypted files, until all those users
have removed it.  This prevents denial of service attacks that would be
possible under simpler schemes, such allowing the first user who added a
key to remove it -- since that could be a malicious user who has
compromised the key.  Of course, encryption keys should be kept secret,
but the idea is that using encryption should never be *less* secure than
not using encryption, even if your key was compromised.

We tolerate that a user will be unable to really remove a key, i.e.
unable to "lock" their encrypted files, if another user has added the
same key.  But in a sense, this is actually a good thing because it will
avoid providing a false notion of security where a key appears to have
been removed when actually it's still in memory, available to any
attacker who compromises the operating system kernel.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/fscrypt_private.h  |  31 +++-
 fs/crypto/keyring.c          | 309 +++++++++++++++++++++++++++++++++--
 fs/crypto/keysetup.c         |  18 +-
 include/uapi/linux/fscrypt.h |   9 +-
 4 files changed, 339 insertions(+), 28 deletions(-)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 1e596cfd085bf..2445b0fc4f01c 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -335,9 +335,16 @@ struct fscrypt_master_key {
 	 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
 	 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
 	 *
-	 * Locking: protected by key->sem.
+	 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
+	 * The reason for two locks is that key->sem also protects modifying
+	 * mk_users, which ranks it above the semaphore for the keyring key
+	 * type, which is in turn above page faults (via keyring_read).  But
+	 * sometimes filesystems call fscrypt_get_encryption_info() from within
+	 * a transaction, which ranks it below page faults.  So we need a
+	 * separate lock which protects mk_secret but not also mk_users.
 	 */
 	struct fscrypt_master_key_secret	mk_secret;
+	struct rw_semaphore			mk_secret_sem;
 
 	/*
 	 * For v1 policy keys: an arbitrary key descriptor which was assigned by
@@ -347,6 +354,22 @@ struct fscrypt_master_key {
 	 */
 	struct fscrypt_key_specifier		mk_spec;
 
+	/*
+	 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
+	 * user who has added this key.  Normally each key will be added by just
+	 * one user, but it's possible that multiple users share a key, and in
+	 * that case we need to keep track of those users so that one user can't
+	 * remove the key before the others want it removed too.
+	 *
+	 * This is NULL for v1 policy keys; those can only be added by root.
+	 *
+	 * Locking: in addition to this keyrings own semaphore, this is
+	 * protected by the master key's key->sem, so we can do atomic
+	 * search+insert.  It can also be searched without taking any locks, but
+	 * in that case the returned key may have already been removed.
+	 */
+	struct key		*mk_users;
+
 	/*
 	 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
 	 * Once this goes to 0, the master key is removed from ->s_master_keys.
@@ -374,9 +397,9 @@ is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
 	/*
 	 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
 	 * fscrypt_key_describe().  These run in atomic context, so they can't
-	 * take key->sem and thus 'secret' can change concurrently which would
-	 * be a data race.  But they only need to know whether the secret *was*
-	 * present at the time of check, so READ_ONCE() suffices.
+	 * take ->mk_secret_sem and thus 'secret' can change concurrently which
+	 * would be a data race.  But they only need to know whether the secret
+	 * *was* present at the time of check, so READ_ONCE() suffices.
 	 */
 	return READ_ONCE(secret->size) != 0;
 }
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index 56e085c2ed8c6..307533d4d7c51 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -42,6 +42,7 @@ static void free_master_key(struct fscrypt_master_key *mk)
 	for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
 		crypto_free_skcipher(mk->mk_mode_keys[i]);
 
+	key_put(mk->mk_users);
 	kzfree(mk);
 }
 
@@ -101,7 +102,39 @@ static struct key_type key_type_fscrypt = {
 	.describe		= fscrypt_key_describe,
 };
 
-/* Search ->s_master_keys */
+static int fscrypt_user_key_instantiate(struct key *key,
+					struct key_preparsed_payload *prep)
+{
+	/*
+	 * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for
+	 * each key, regardless of the exact key size.  The amount of memory
+	 * actually used is greater than the size of the raw key anyway.
+	 */
+	return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE);
+}
+
+static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m)
+{
+	seq_puts(m, key->description);
+}
+
+/*
+ * Type of key in ->mk_users.  Each key of this type represents a particular
+ * user who has added a particular master key.
+ *
+ * Note that the name of this key type really should be something like
+ * ".fscrypt-user" instead of simply ".fscrypt".  But the shorter name is chosen
+ * mainly for simplicity of presentation in /proc/keys when read by a non-root
+ * user.  And it is expected to be rare that a key is actually added by multiple
+ * users, since users should keep their encryption keys confidential.
+ */
+static struct key_type key_type_fscrypt_user = {
+	.name			= ".fscrypt",
+	.instantiate		= fscrypt_user_key_instantiate,
+	.describe		= fscrypt_user_key_describe,
+};
+
+/* Search ->s_master_keys or ->mk_users */
 static struct key *search_fscrypt_keyring(struct key *keyring,
 					  struct key_type *type,
 					  const char *description)
@@ -127,6 +160,13 @@ static struct key *search_fscrypt_keyring(struct key *keyring,
 
 #define FSCRYPT_MK_DESCRIPTION_SIZE	(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1)
 
+#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE	\
+	(CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \
+	 CONST_STRLEN("-users") + 1)
+
+#define FSCRYPT_MK_USER_DESCRIPTION_SIZE	\
+	(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1)
+
 static void format_fs_keyring_description(
 			char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
 			const struct super_block *sb)
@@ -142,6 +182,23 @@ static void format_mk_description(
 		master_key_spec_len(mk_spec), (u8 *)&mk_spec->u);
 }
 
+static void format_mk_users_keyring_description(
+			char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE],
+			const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+	sprintf(description, "fscrypt-%*phN-users",
+		FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier);
+}
+
+static void format_mk_user_description(
+			char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE],
+			const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+
+	sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE,
+		mk_identifier, __kuid_val(current_fsuid()));
+}
+
 /* Create ->s_master_keys if needed.  Synchronized by fscrypt_add_key_mutex. */
 static int allocate_filesystem_keyring(struct super_block *sb)
 {
@@ -189,6 +246,81 @@ struct key *fscrypt_find_master_key(struct super_block *sb,
 	return search_fscrypt_keyring(keyring, &key_type_fscrypt, description);
 }
 
+static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk)
+{
+	char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE];
+	struct key *keyring;
+
+	format_mk_users_keyring_description(description,
+					    mk->mk_spec.u.identifier);
+	keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+				current_cred(), KEY_POS_SEARCH |
+				  KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	mk->mk_users = keyring;
+	return 0;
+}
+
+/*
+ * Find the current user's key in the master key's ->mk_users.
+ * Returns ERR_PTR(-ENOKEY) if not found.
+ */
+static struct key *find_master_key_user(struct fscrypt_master_key *mk)
+{
+	char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
+
+	format_mk_user_description(description, mk->mk_spec.u.identifier);
+	return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user,
+				      description);
+}
+
+/*
+ * Give the current user a key in ->mk_users.  This charges the user's quota and
+ * marks the master key as added by the current user, so that it cannot be
+ * removed by another user with the key.  Either the master key's key->sem must
+ * be held for write, or the master key must be still undergoing initialization.
+ */
+static int add_master_key_user(struct fscrypt_master_key *mk)
+{
+	char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
+	struct key *mk_user;
+	int err;
+
+	format_mk_user_description(description, mk->mk_spec.u.identifier);
+	mk_user = key_alloc(&key_type_fscrypt_user, description,
+			    current_fsuid(), current_gid(), current_cred(),
+			    KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL);
+	if (IS_ERR(mk_user))
+		return PTR_ERR(mk_user);
+
+	err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL);
+	key_put(mk_user);
+	return err;
+}
+
+/*
+ * Remove the current user's key from ->mk_users, if present.
+ * The master key's key->sem must be held for write.
+ */
+static int remove_master_key_user(struct fscrypt_master_key *mk)
+{
+	struct key *mk_user;
+	int err;
+
+	mk_user = find_master_key_user(mk);
+	if (IS_ERR(mk_user)) {
+		if (mk_user != ERR_PTR(-ENOKEY))
+			return PTR_ERR(mk_user);
+		return 0;
+	}
+	err = key_unlink(mk->mk_users, mk_user);
+	key_put(mk_user);
+	return err;
+}
+
 /*
  * Allocate a new fscrypt_master_key which contains the given secret, set it as
  * the payload of a new 'struct key' of type fscrypt, and link the 'struct key'
@@ -210,11 +342,26 @@ static int add_new_master_key(struct fscrypt_master_key_secret *secret,
 	mk->mk_spec = *mk_spec;
 
 	move_master_key_secret(&mk->mk_secret, secret);
+	init_rwsem(&mk->mk_secret_sem);
 
 	refcount_set(&mk->mk_refcount, 1); /* secret is present */
 	INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
 	spin_lock_init(&mk->mk_decrypted_inodes_lock);
 
+	if (mk_spec->type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {
+		err = allocate_master_key_users_keyring(mk);
+		if (err)
+			goto out_free_mk;
+		err = add_master_key_user(mk);
+		if (err)
+			goto out_free_mk;
+	}
+
+	/*
+	 * Note that we don't charge this key to anyone's quota, since when
+	 * ->mk_users is in use those keys are charged instead, and otherwise
+	 * (when ->mk_users isn't in use) only root can add these keys.
+	 */
 	format_mk_description(description, mk_spec);
 	key = key_alloc(&key_type_fscrypt, description,
 			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
@@ -242,13 +389,45 @@ static int add_existing_master_key(struct fscrypt_master_key *mk,
 				   struct fscrypt_master_key_secret *secret,
 				   const struct fscrypt_key_specifier *mk_spec)
 {
-	if (is_master_key_secret_present(&mk->mk_secret))
-		return 0;
+	struct key *mk_user;
+	bool rekey;
+	int err;
 
-	if (!refcount_inc_not_zero(&mk->mk_refcount))
+	/*
+	 * If the current user is already in ->mk_users, then there's nothing to
+	 * do.  (Not applicable for v1 policy keys, which have NULL ->mk_users.)
+	 */
+	if (mk->mk_users) {
+		mk_user = find_master_key_user(mk);
+		if (mk_user != ERR_PTR(-ENOKEY)) {
+			if (IS_ERR(mk_user))
+				return PTR_ERR(mk_user);
+			key_put(mk_user);
+			return 0;
+		}
+	}
+
+	/* If we'll be re-adding ->mk_secret, try to take the reference. */
+	rekey = !is_master_key_secret_present(&mk->mk_secret);
+	if (rekey && !refcount_inc_not_zero(&mk->mk_refcount))
 		return KEY_DEAD;
 
-	move_master_key_secret(&mk->mk_secret, secret);
+	/* Add the current user to ->mk_users, if applicable. */
+	if (mk->mk_users) {
+		err = add_master_key_user(mk);
+		if (err) {
+			if (rekey && refcount_dec_and_test(&mk->mk_refcount))
+				return KEY_DEAD;
+			return err;
+		}
+	}
+
+	/* Re-add the secret if needed. */
+	if (rekey) {
+		down_write(&mk->mk_secret_sem);
+		move_master_key_secret(&mk->mk_secret, secret);
+		up_write(&mk->mk_secret_sem);
+	}
 	return 0;
 }
 
@@ -275,7 +454,7 @@ static int add_master_key(struct super_block *sb,
 	} else {
 		/*
 		 * Found the key in ->s_master_keys.  Re-add the secret if
-		 * needed.
+		 * needed, and add the user to ->mk_users if needed.
 		 */
 		down_write(&key->sem);
 		err = add_existing_master_key(key->payload.data[0], secret,
@@ -297,6 +476,23 @@ static int add_master_key(struct super_block *sb,
 /*
  * Add a master encryption key to the filesystem, causing all files which were
  * encrypted with it to appear "unlocked" (decrypted) when accessed.
+ *
+ * When adding a key for use by v1 encryption policies, this ioctl is
+ * privileged, and userspace must provide the 'key_descriptor'.
+ *
+ * When adding a key for use by v2+ encryption policies, this ioctl is
+ * unprivileged.  This is needed, in general, to allow non-root users to use
+ * encryption without encountering the visibility problems of process-subscribed
+ * keyrings and the inability to properly remove keys.  This works by having
+ * each key identified by its cryptographically secure hash --- the
+ * 'key_identifier'.  The cryptographic hash ensures that a malicious user
+ * cannot add the wrong key for a given identifier.  Furthermore, each added key
+ * is charged to the appropriate user's quota for the keyrings service, which
+ * prevents a malicious user from adding too many keys.  Finally, we forbid a
+ * user from removing a key while other users have added it too, which prevents
+ * a user who knows another user's key from causing a denial-of-service by
+ * removing it at an inopportune time.  (We tolerate that a user who knows a key
+ * can prevent other users from removing it.)
  */
 int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 {
@@ -325,11 +521,16 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 	if (copy_from_user(secret.raw, uarg->raw, secret.size))
 		goto out_wipe_secret;
 
-	err = -EACCES;
-	if (!capable(CAP_SYS_ADMIN))
-		goto out_wipe_secret;
-
-	if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {
+	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {
+		/*
+		 * Only root can add keys that are identified by an arbitrary
+		 * descriptor rather than by a cryptographic hash --- since
+		 * otherwise a malicious user could add the wrong key.
+		 */
+		err = -EACCES;
+		if (!capable(CAP_SYS_ADMIN))
+			goto out_wipe_secret;
+	} else {
 		err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size);
 		if (err)
 			goto out_wipe_secret;
@@ -527,10 +728,26 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg)
 	if (!valid_key_spec(&arg.key_spec))
 		return -EINVAL;
 
+	if (arg.flags & ~FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)
+		return -EINVAL;
+
 	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
 		return -EINVAL;
 
-	if (!capable(CAP_SYS_ADMIN))
+	/*
+	 * Only root can request that the key be removed no matter how many
+	 * users have added it.
+	 */
+	if ((arg.flags & FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS) &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	/*
+	 * Only root can add and remove keys that are identified by an arbitrary
+	 * descriptor rather than by a cryptographic hash.
+	 */
+	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
+	    !capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
 	/* Find the key being removed. */
@@ -541,11 +758,35 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg)
 
 	down_write(&key->sem);
 
-	/* Wipe the secret. */
+	/* If relevant, remove current user's (or all users) usage of the key */
+	if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) {
+		if (arg.flags & FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)
+			err = keyring_clear(mk->mk_users);
+		else
+			err = remove_master_key_user(mk);
+		if (err) {
+			up_write(&key->sem);
+			goto out_put_key;
+		}
+		if (mk->mk_users->keys.nr_leaves_on_tree != 0) {
+			/*
+			 * Other users have still added the key too.  We removed
+			 * the current user's usage of the key if there was one,
+			 * but we still can't remove the key itself.
+			 */
+			err = -EUSERS;
+			up_write(&key->sem);
+			goto out_put_key;
+		}
+	}
+
+	/* No usages remaining.  Go ahead and wipe the secret. */
 	dead = false;
 	if (is_master_key_secret_present(&mk->mk_secret)) {
+		down_write(&mk->mk_secret_sem);
 		wipe_master_key_secret(&mk->mk_secret);
 		dead = refcount_dec_and_test(&mk->mk_refcount);
+		up_write(&mk->mk_secret_sem);
 	}
 	up_write(&key->sem);
 	if (dead) {
@@ -559,6 +800,7 @@ int fscrypt_ioctl_remove_key(struct file *filp, const void __user *uarg)
 		/* Some inodes still reference this key; try to evict them. */
 		err = try_to_lock_encrypted_files(sb, mk);
 	}
+out_put_key:
 	key_put(key);
 	return err;
 }
@@ -574,6 +816,15 @@ EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
  * of an encrypted directory without using a hack such as trying to open a
  * regular file in it (which can confuse the "incompletely removed" state with
  * absent or present).
+ *
+ * In addition, for v2 policy keys we allow applications to determine, via
+ * ->status_flags and ->user_count, whether the key has been added by the
+ * current user, by other users, or by both.  Most applications should not need
+ * this, since ordinarily only one user should know a given key.  However, if a
+ * secret key is shared by multiple users, applications may wish to add an
+ * already-present key to prevent other users from removing it.  This ioctl can
+ * be used to check whether that really is the case before the work is done to
+ * add the key --- which might e.g. require prompting the user for a passphrase.
  */
 int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
 {
@@ -592,6 +843,8 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
 	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
 		return -EINVAL;
 
+	arg.status_flags = 0;
+	arg.user_count = 0;
 	memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved));
 
 	key = fscrypt_find_master_key(sb, &arg.key_spec);
@@ -612,6 +865,20 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
 	}
 
 	arg.status = FSCRYPT_KEY_STATUS_PRESENT;
+	if (mk->mk_users) {
+		struct key *mk_user;
+
+		arg.user_count = mk->mk_users->keys.nr_leaves_on_tree;
+		mk_user = find_master_key_user(mk);
+		if (!IS_ERR(mk_user)) {
+			arg.status_flags |=
+				FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF;
+			key_put(mk_user);
+		} else if (mk_user != ERR_PTR(-ENOKEY)) {
+			err = PTR_ERR(mk_user);
+			goto out_release_key;
+		}
+	}
 	err = 0;
 out_release_key:
 	up_read(&key->sem);
@@ -625,5 +892,19 @@ EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status);
 
 int __init fscrypt_init_keyring(void)
 {
-	return register_key_type(&key_type_fscrypt);
+	int err;
+
+	err = register_key_type(&key_type_fscrypt);
+	if (err)
+		return err;
+
+	err = register_key_type(&key_type_fscrypt_user);
+	if (err)
+		goto err_unregister_fscrypt;
+
+	return 0;
+
+err_unregister_fscrypt:
+	unregister_key_type(&key_type_fscrypt);
+	return err;
 }
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 358883cde0c9e..ba69ac0c0e3c8 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -291,10 +291,10 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
  *
  * If the master key is found in the filesystem-level keyring, then the
  * corresponding 'struct key' is returned in *master_key_ret with
- * ->sem read-locked.  This is needed to ensure that only one task links the
- * fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race to create
- * an fscrypt_info for the same inode), and to synchronize the master key being
- * removed with a new inode starting to use it.
+ * ->mk_secret_sem read-locked.  This is needed to ensure that only one task
+ * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race
+ * to create an fscrypt_info for the same inode), and to synchronize the master
+ * key being removed with a new inode starting to use it.
  */
 static int setup_file_encryption_key(struct fscrypt_info *ci,
 				     struct key **master_key_ret)
@@ -332,7 +332,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 	}
 
 	mk = key->payload.data[0];
-	down_read(&key->sem);
+	down_read(&mk->mk_secret_sem);
 
 	/* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
 	if (!is_master_key_secret_present(&mk->mk_secret)) {
@@ -366,7 +366,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 	return 0;
 
 out_release_key:
-	up_read(&key->sem);
+	up_read(&mk->mk_secret_sem);
 	key_put(key);
 	return err;
 }
@@ -492,7 +492,9 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	res = 0;
 out:
 	if (master_key) {
-		up_read(&master_key->sem);
+		struct fscrypt_master_key *mk = master_key->payload.data[0];
+
+		up_read(&mk->mk_secret_sem);
 		key_put(master_key);
 	}
 	if (res == -ENOKEY)
@@ -555,7 +557,7 @@ int fscrypt_drop_inode(struct inode *inode)
 	mk = ci->ci_master_key->payload.data[0];
 
 	/*
-	 * Note: since we aren't holding key->sem, the result here can
+	 * Note: since we aren't holding ->mk_secret_sem, the result here can
 	 * immediately become outdated.  But there's no correctness problem with
 	 * unnecessarily evicting.  Nor is there a correctness problem with not
 	 * evicting while iput() is racing with the key being removed, since
diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
index 78811564c95f1..e292d920ad2a0 100644
--- a/include/uapi/linux/fscrypt.h
+++ b/include/uapi/linux/fscrypt.h
@@ -104,7 +104,9 @@ struct fscrypt_add_key_arg {
 /* Struct passed to FS_IOC_REMOVE_ENCRYPTION_KEY */
 struct fscrypt_remove_key_arg {
 	struct fscrypt_key_specifier key_spec;
-	__u32 __reserved[6];
+#define FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS	0x00000001
+	__u32 flags;
+	__u32 __reserved[5];
 };
 
 /* Struct passed to FS_IOC_GET_ENCRYPTION_KEY_STATUS */
@@ -118,7 +120,10 @@ struct fscrypt_get_key_status_arg {
 #define FSCRYPT_KEY_STATUS_PRESENT		2
 #define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED	3
 	__u32 status;
-	__u32 __out_reserved[15];
+#define FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF   0x00000001
+	__u32 status_flags;
+	__u32 user_count;
+	__u32 __out_reserved[13];
 };
 
 #define FS_IOC_SET_ENCRYPTION_POLICY	  _IOR('f', 19, struct fscrypt_policy)
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 12/16] fscrypt: require that key be added when setting a v2 encryption policy
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (10 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 11/16] fscrypt: allow unprivileged users to add/remove keys for v2 policies Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 21:24   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 13/16] ext4: wire up new fscrypt ioctls Eric Biggers
                   ` (3 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

By looking up the master keys in a filesystem-level keyring rather than
in the calling processes' key hierarchy, it becomes possible for a user
to set an encryption policy which refers to some key they don't actually
know, then encrypt their files using that key.  Cryptographically this
isn't much of a problem, but the semantics of this would be a bit weird.
Thus, enforce that a v2 encryption policy can only be set if the user
has previously added the key, or has capable(CAP_FOWNER).

We tolerate that this problem will continue to exist for v1 encryption
policies, however; there is no way around that.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/fscrypt_private.h |  3 +++
 fs/crypto/keyring.c         | 47 +++++++++++++++++++++++++++++++++++++
 fs/crypto/policy.c          |  6 +++++
 3 files changed, 56 insertions(+)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 2445b0fc4f01c..8d61f410aa677 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -408,6 +408,9 @@ extern struct key *
 fscrypt_find_master_key(struct super_block *sb,
 			const struct fscrypt_key_specifier *mk_spec);
 
+extern int fscrypt_verify_key_added(struct super_block *sb,
+				    const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
+
 extern int __init fscrypt_init_keyring(void);
 
 /* keysetup.c */
diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index 307533d4d7c51..258409d0c7409 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -562,6 +562,53 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 }
 EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
 
+/*
+ * Verify that the current user has added a master key with the given identifier
+ * (returns -ENOKEY if not).  This is needed to prevent a user from encrypting
+ * their files using some other user's key which they don't actually know.
+ * Cryptographically this isn't much of a problem, but the semantics of this
+ * would be a bit weird, so it's best to just forbid it.
+ *
+ * The system administrator (CAP_FOWNER) can override this, which should be
+ * enough for any use cases where encryption policies are being set using keys
+ * that were chosen ahead of time but aren't available at the moment.
+ *
+ * Note that the key may have already removed by the time this returns, but
+ * that's okay; we just care whether the key was there at some point.
+ *
+ * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code
+ */
+int fscrypt_verify_key_added(struct super_block *sb,
+			     const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+	struct fscrypt_key_specifier mk_spec;
+	struct key *key, *mk_user;
+	struct fscrypt_master_key *mk;
+	int err;
+
+	mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+	memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
+
+	key = fscrypt_find_master_key(sb, &mk_spec);
+	if (IS_ERR(key)) {
+		err = PTR_ERR(key);
+		goto out;
+	}
+	mk = key->payload.data[0];
+	mk_user = find_master_key_user(mk);
+	if (IS_ERR(mk_user)) {
+		err = PTR_ERR(mk_user);
+	} else {
+		key_put(mk_user);
+		err = 0;
+	}
+	key_put(key);
+out:
+	if (err == -ENOKEY && capable(CAP_FOWNER))
+		err = 0;
+	return err;
+}
+
 static void shrink_dcache_inode(struct inode *inode)
 {
 	struct dentry *dentry;
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 0141d338c1fdb..60de9048ed4d1 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -233,6 +233,7 @@ static int set_encryption_policy(struct inode *inode,
 {
 	union fscrypt_context ctx;
 	int ctxsize;
+	int err;
 
 	if (!fscrypt_supported_policy(policy, inode))
 		return -EINVAL;
@@ -251,6 +252,11 @@ static int set_encryption_policy(struct inode *inode,
 		 */
 		pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
 			     current->comm, current->pid);
+	} else {
+		err = fscrypt_verify_key_added(inode->i_sb,
+					       policy->v2.master_key_identifier);
+		if (err)
+			return err;
 	}
 
 	ctxsize = fscrypt_new_context_from_policy(&ctx, policy);
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 13/16] ext4: wire up new fscrypt ioctls
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (11 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 12/16] fscrypt: require that key be added when setting a v2 encryption policy Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-28 21:24   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 14/16] f2fs: " Eric Biggers
                   ` (2 subsequent siblings)
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Wire up the new ioctls for adding and removing fscrypt keys to/from the
filesystem, and the new ioctl for retrieving v2 encryption policies.

FS_IOC_REMOVE_ENCRYPTION_KEY also required making ext4_drop_inode() call
fscrypt_drop_inode().

For more details see Documentation/filesystems/fscrypt.rst and the
fscrypt patches that added the implementation of these ioctls.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/ext4/ioctl.c | 24 ++++++++++++++++++++++++
 fs/ext4/super.c |  3 +++
 2 files changed, 27 insertions(+)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 442f7ef873fc3..616fcf9eb52ec 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1115,6 +1115,26 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_GET_ENCRYPTION_POLICY:
 		return fscrypt_ioctl_get_policy(filp, (void __user *)arg);
 
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg);
+
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_add_key(filp, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_remove_key(filp, (const void __user *)arg);
+
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
+
 	case EXT4_IOC_FSGETXATTR:
 	{
 		struct fsxattr fa;
@@ -1231,6 +1251,10 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_SET_ENCRYPTION_POLICY:
 	case EXT4_IOC_GET_ENCRYPTION_PWSALT:
 	case EXT4_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
 	case EXT4_IOC_SHUTDOWN:
 	case FS_IOC_GETFSMAP:
 		break;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4079605d437ae..757819139b8f7 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1107,6 +1107,9 @@ static int ext4_drop_inode(struct inode *inode)
 {
 	int drop = generic_drop_inode(inode);
 
+	if (!drop)
+		drop = fscrypt_drop_inode(inode);
+
 	trace_ext4_drop_inode(inode, drop);
 	return drop;
 }
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 14/16] f2fs: wire up new fscrypt ioctls
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (12 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 13/16] ext4: wire up new fscrypt ioctls Eric Biggers
@ 2019-07-26 22:41 ` " Eric Biggers
  2019-07-30  0:36   ` Jaegeuk Kim
  2019-08-02  8:10   ` Chao Yu
  2019-07-26 22:41 ` [PATCH v7 15/16] ubifs: " Eric Biggers
  2019-07-26 22:41 ` [PATCH v7 16/16] fscrypt: document the new ioctls and policy version Eric Biggers
  15 siblings, 2 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Wire up the new ioctls for adding and removing fscrypt keys to/from the
filesystem, and the new ioctl for retrieving v2 encryption policies.

FS_IOC_REMOVE_ENCRYPTION_KEY also required making f2fs_drop_inode() call
fscrypt_drop_inode().

For more details see Documentation/filesystems/fscrypt.rst and the
fscrypt patches that added the implementation of these ioctls.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/f2fs/file.c  | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/f2fs/super.c |  2 ++
 2 files changed, 48 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f8d46df8fa9ee..d81dda290b829 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2184,6 +2184,40 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 	return err;
 }
 
+static int f2fs_ioc_get_encryption_policy_ex(struct file *filp,
+					     unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg);
+}
+
+static int f2fs_ioc_add_encryption_key(struct file *filp, unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_add_key(filp, (void __user *)arg);
+}
+
+static int f2fs_ioc_remove_encryption_key(struct file *filp, unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_remove_key(filp, (const void __user *)arg);
+}
+
+static int f2fs_ioc_get_encryption_key_status(struct file *filp,
+					      unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
+}
+
 static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -3109,6 +3143,14 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return f2fs_ioc_get_encryption_policy(filp, arg);
 	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
 		return f2fs_ioc_get_encryption_pwsalt(filp, arg);
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		return f2fs_ioc_get_encryption_policy_ex(filp, arg);
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		return f2fs_ioc_add_encryption_key(filp, arg);
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		return f2fs_ioc_remove_encryption_key(filp, arg);
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		return f2fs_ioc_get_encryption_key_status(filp, arg);
 	case F2FS_IOC_GARBAGE_COLLECT:
 		return f2fs_ioc_gc(filp, arg);
 	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
@@ -3236,6 +3278,10 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case F2FS_IOC_SET_ENCRYPTION_POLICY:
 	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
 	case F2FS_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
 	case F2FS_IOC_GARBAGE_COLLECT:
 	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
 	case F2FS_IOC_WRITE_CHECKPOINT:
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 6de6cda440315..f5fae8d511a20 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -913,6 +913,8 @@ static int f2fs_drop_inode(struct inode *inode)
 		return 0;
 	}
 	ret = generic_drop_inode(inode);
+	if (!ret)
+		ret = fscrypt_drop_inode(inode);
 	trace_f2fs_drop_inode(inode, ret);
 	return ret;
 }
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 15/16] ubifs: wire up new fscrypt ioctls
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (13 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 14/16] f2fs: " Eric Biggers
@ 2019-07-26 22:41 ` " Eric Biggers
  2019-07-30  0:39   ` Theodore Y. Ts'o
  2019-07-26 22:41 ` [PATCH v7 16/16] fscrypt: document the new ioctls and policy version Eric Biggers
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Wire up the new ioctls for adding and removing fscrypt keys to/from the
filesystem, and the new ioctl for retrieving v2 encryption policies.

FS_IOC_REMOVE_ENCRYPTION_KEY also required making UBIFS use
fscrypt_drop_inode().

For more details see Documentation/filesystems/fscrypt.rst and the
fscrypt patches that added the implementation of these ioctls.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/ubifs/ioctl.c | 16 ++++++++++++++++
 fs/ubifs/super.c | 11 +++++++++++
 2 files changed, 27 insertions(+)

diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c
index 034ad14710d14..a0dbf58780409 100644
--- a/fs/ubifs/ioctl.c
+++ b/fs/ubifs/ioctl.c
@@ -185,6 +185,18 @@ long ubifs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case FS_IOC_GET_ENCRYPTION_POLICY:
 		return fscrypt_ioctl_get_policy(file, (void __user *)arg);
 
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		return fscrypt_ioctl_get_policy_ex(file, (void __user *)arg);
+
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		return fscrypt_ioctl_add_key(file, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		return fscrypt_ioctl_remove_key(file, (const void __user *)arg);
+
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		return fscrypt_ioctl_get_key_status(file, (void __user *)arg);
+
 	default:
 		return -ENOTTY;
 	}
@@ -202,6 +214,10 @@ long ubifs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		break;
 	case FS_IOC_SET_ENCRYPTION_POLICY:
 	case FS_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
 		break;
 	default:
 		return -ENOIOCTLCMD;
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 2c0803b0ac3aa..3ad6620f14fb8 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -318,6 +318,16 @@ static int ubifs_write_inode(struct inode *inode, struct writeback_control *wbc)
 	return err;
 }
 
+static int ubifs_drop_inode(struct inode *inode)
+{
+	int drop = generic_drop_inode(inode);
+
+	if (!drop)
+		drop = fscrypt_drop_inode(inode);
+
+	return drop;
+}
+
 static void ubifs_evict_inode(struct inode *inode)
 {
 	int err;
@@ -1990,6 +2000,7 @@ const struct super_operations ubifs_super_operations = {
 	.free_inode    = ubifs_free_inode,
 	.put_super     = ubifs_put_super,
 	.write_inode   = ubifs_write_inode,
+	.drop_inode    = ubifs_drop_inode,
 	.evict_inode   = ubifs_evict_inode,
 	.statfs        = ubifs_statfs,
 	.dirty_inode   = ubifs_dirty_inode,
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* [PATCH v7 16/16] fscrypt: document the new ioctls and policy version
  2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
                   ` (14 preceding siblings ...)
  2019-07-26 22:41 ` [PATCH v7 15/16] ubifs: " Eric Biggers
@ 2019-07-26 22:41 ` Eric Biggers
  2019-07-29  2:00   ` Theodore Y. Ts'o
  15 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-26 22:41 UTC (permalink / raw)
  To: linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

Update the fscrypt documentation file to catch up to all the latest
changes, including the new ioctls to manage master encryption keys in
the filesystem-level keyring and the support for v2 encryption policies.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 Documentation/filesystems/fscrypt.rst | 648 +++++++++++++++++++++-----
 1 file changed, 532 insertions(+), 116 deletions(-)

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 2c4b6e56b81c5..d88bfeff410c7 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -72,6 +72,9 @@ Online attacks
 fscrypt (and storage encryption in general) can only provide limited
 protection, if any at all, against online attacks.  In detail:
 
+Side-channel attacks
+~~~~~~~~~~~~~~~~~~~~
+
 fscrypt is only resistant to side-channel attacks, such as timing or
 electromagnetic attacks, to the extent that the underlying Linux
 Cryptographic API algorithms are.  If a vulnerable algorithm is used,
@@ -80,29 +83,84 @@ attacker to mount a side channel attack against the online system.
 Side channel attacks may also be mounted against applications
 consuming decrypted data.
 
-After an encryption key has been provided, fscrypt is not designed to
-hide the plaintext file contents or filenames from other users on the
-same system, regardless of the visibility of the keyring key.
-Instead, existing access control mechanisms such as file mode bits,
-POSIX ACLs, LSMs, or mount namespaces should be used for this purpose.
-Also note that as long as the encryption keys are *anywhere* in
-memory, an online attacker can necessarily compromise them by mounting
-a physical attack or by exploiting any kernel security vulnerability
-which provides an arbitrary memory read primitive.
-
-While it is ostensibly possible to "evict" keys from the system,
-recently accessed encrypted files will remain accessible at least
-until the filesystem is unmounted or the VFS caches are dropped, e.g.
-using ``echo 2 > /proc/sys/vm/drop_caches``.  Even after that, if the
-RAM is compromised before being powered off, it will likely still be
-possible to recover portions of the plaintext file contents, if not
-some of the encryption keys as well.  (Since Linux v4.12, all
-in-kernel keys related to fscrypt are sanitized before being freed.
-However, userspace would need to do its part as well.)
-
-Currently, fscrypt does not prevent a user from maliciously providing
-an incorrect key for another user's existing encrypted files.  A
-protection against this is planned.
+Unauthorized file access
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+After an encryption key has been added, fscrypt does not hide the
+plaintext file contents or filenames from other users on the same
+system.  Instead, existing access control mechanisms such as file mode
+bits, POSIX ACLs, LSMs, or namespaces should be used for this purpose.
+
+(For the reasoning behind this, understand that while the key is
+added, the confidentiality of the data, from the perspective of the
+system itself, is *not* protected by the mathematical properties of
+encryption but rather only by the correctness of the kernel.
+Therefore, any encryption-specific access control checks would merely
+be enforced by kernel *code* and therefore would be largely redundant
+with the wide variety of access control mechanisms already available.)
+
+Kernel memory compromise
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+An attacker who compromises the system enough to read from arbitrary
+memory, e.g. by mounting a physical attack or by exploiting a kernel
+security vulnerability, can compromise all encryption keys that are
+currently in use.
+
+However, fscrypt allows encryption keys to be removed from the kernel,
+which may protect them from later compromise.
+
+In more detail, the FS_IOC_REMOVE_ENCRYPTION_KEY ioctl will wipe a
+master encryption key from kernel memory.  Moreover, it will try to
+evict all cached inodes which had been "unlocked" using the key,
+thereby wiping their per-file keys and making them once again appear
+"locked", i.e. in ciphertext or encrypted form.
+
+However, FS_IOC_REMOVE_ENCRYPTION_KEY has some limitations:
+
+- Per-file keys for in-use files will *not* be removed or wiped.
+  Therefore, for maximum effect, userspace should close the relevant
+  encrypted files and directories before removing a master key, as
+  well as kill any processes whose working directory is in an affected
+  encrypted directory.
+
+- The kernel cannot magically wipe copies of the master key(s) that
+  userspace might have as well.  Therefore, userspace must wipe all
+  copies of the master key(s) it makes as well.  Naturally, the same
+  also applies to all higher levels in the key hierarchy.  Userspace
+  should also follow other security precautions such as mlock()ing
+  memory containing keys to prevent it from being swapped out.
+
+- In general, decrypted contents and filenames in the kernel VFS
+  caches are freed but not wiped.  Therefore, portions thereof may be
+  recoverable from freed memory, even after the corresponding key(s)
+  were wiped.  To partially solve this, you can set
+  CONFIG_PAGE_POISONING=y in your kernel config and add page_poison=1
+  to your kernel command line.  However, this has a performance cost.
+
+- Secret keys might still exist in CPU registers, in crypto
+  accelerator hardware (if used by the crypto API to implement any of
+  the algorithms), or in other places not explicitly considered here.
+
+Limitations of v1 policies
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+v1 encryption policies have some weaknesses with respect to online
+attacks:
+
+- There is no verification that the provided master key is correct.
+  Consequently, malicious users can associate the wrong key with
+  encrypted files, even files to which they have only read-only
+  access.
+
+- A compromise of a per-file key also compromises the master key from
+  which it was derived.
+
+- Non-root users cannot securely remove encryption keys.
+
+All the above problems are fixed with v2 encryption policies.  For
+this reason among others, it is recommended to use v2 encryption
+policies on all new encrypted directories.
 
 Key hierarchy
 =============
@@ -123,11 +181,46 @@ appropriate master key.  There can be any number of master keys, each
 of which protects any number of directory trees on any number of
 filesystems.
 
-Userspace should generate master keys either using a cryptographically
-secure random number generator, or by using a KDF (Key Derivation
-Function).  Note that whenever a KDF is used to "stretch" a
-lower-entropy secret such as a passphrase, it is critical that a KDF
-designed for this purpose be used, such as scrypt, PBKDF2, or Argon2.
+Master keys should be pseudorandom, i.e. indistinguishable from random
+bytestrings of the same length.  This implies that users **must not**
+directly use a password as a master key, zero-pad a shorter key, or
+repeat a shorter key.  Instead, users should generate master keys
+either using a cryptographically secure random number generator, or by
+using a KDF (Key Derivation Function).  Note that whenever a KDF is
+used to "stretch" a lower-entropy secret such as a passphrase, it is
+critical that a KDF designed for this purpose be used, such as scrypt,
+PBKDF2, or Argon2.
+
+Key derivation function
+-----------------------
+
+With one exception, fscrypt never uses the master key(s) for
+encryption directly.  Instead, they are only used as input to a KDF
+(Key Derivation Function) to derive the actual keys.
+
+The KDF used for a particular master key differs depending on whether
+the key is used for v1 encryption policies or for v2 encryption
+policies.  Users **must not** use the same key for both v1 and v2
+encryption policies.
+
+For v1 encryption policies, the KDF only supports deriving per-file
+encryption keys.  It works by encrypting the master key with
+AES-128-ECB, using the file's 16-byte nonce as the AES key.  The
+resulting ciphertext is used as the derived key.  If the ciphertext is
+longer than needed, then it is truncated to the needed length.
+
+For v2 encryption policies, the KDF is HKDF-SHA512.  The master key is
+passed as the "input keying material", no salt is used, and a distinct
+"application-specific information string" is used for each distinct
+key to be derived.  For example, when a per-file encryption key is
+derived, the application-specific information string is the file's
+nonce prefixed with "fscrypt\\0" and a context byte.  Different
+context bytes are used for other types of derived keys.
+
+HKDF-SHA512 is preferred to the original AES-128-ECB based KDF because
+HKDF is more flexible, is nonreversible, and evenly distributes
+entropy from the master key.  HKDF is also standardized and widely
+used by other software, whereas the AES-128-ECB based KDF is ad-hoc.
 
 Per-file keys
 -------------
@@ -138,29 +231,9 @@ files doesn't map to the same ciphertext, or vice versa.  In most
 cases, fscrypt does this by deriving per-file keys.  When a new
 encrypted inode (regular file, directory, or symlink) is created,
 fscrypt randomly generates a 16-byte nonce and stores it in the
-inode's encryption xattr.  Then, it uses a KDF (Key Derivation
-Function) to derive the file's key from the master key and nonce.
-
-The Adiantum encryption mode (see `Encryption modes and usage`_) is
-special, since it accepts longer IVs and is suitable for both contents
-and filenames encryption.  For it, a "direct key" option is offered
-where the file's nonce is included in the IVs and the master key is
-used for encryption directly.  This improves performance; however,
-users must not use the same master key for any other encryption mode.
-
-Below, the KDF and design considerations are described in more detail.
-
-The current KDF works by encrypting the master key with AES-128-ECB,
-using the file's nonce as the AES key.  The output is used as the
-derived key.  If the output is longer than needed, then it is
-truncated to the needed length.
-
-Note: this KDF meets the primary security requirement, which is to
-produce unique derived keys that preserve the entropy of the master
-key, assuming that the master key is already a good pseudorandom key.
-However, it is nonstandard and has some problems such as being
-reversible, so it is generally considered to be a mistake!  It may be
-replaced with HKDF or another more standard KDF in the future.
+inode's encryption xattr.  Then, it uses a KDF (as described in `Key
+derivation function`_) to derive the file's key from the master key
+and nonce.
 
 Key derivation was chosen over key wrapping because wrapped keys would
 require larger xattrs which would be less likely to fit in-line in the
@@ -176,6 +249,37 @@ rejected as it would have prevented ext4 filesystems from being
 resized, and by itself still wouldn't have been sufficient to prevent
 the same key from being directly reused for both XTS and CTS-CBC.
 
+DIRECT_KEY and per-mode keys
+----------------------------
+
+The Adiantum encryption mode (see `Encryption modes and usage`_) is
+suitable for both contents and filenames encryption, and it accepts
+long IVs --- long enough to hold both an 8-byte logical block number
+and a 16-byte per-file nonce.  Also, the overhead of each Adiantum key
+is greater than that of an AES-256-XTS key.
+
+Therefore, to improve performance and save memory, for Adiantum a
+"direct key" configuration is supported.  When the user has enabled
+this by setting FSCRYPT_POLICY_FLAG_DIRECT_KEY in the fscrypt policy,
+per-file keys are not used.  Instead, whenever any data (contents or
+filenames) is encrypted, the file's 16-byte nonce is included in the
+IV.  Moreover:
+
+- For v1 encryption policies, the encryption is done directly with the
+  master key.  Because of this, users **must not** use the same master
+  key for any other purpose, even for other v1 policies.
+
+- For v2 encryption policies, the encryption is done with a per-mode
+  key derived using the KDF.  Users may use the same master key for
+  other v2 encryption policies.
+
+Key identifiers
+---------------
+
+For master keys used for v2 encryption policies, a unique 16-byte "key
+identifier" is also derived using the KDF.  This value is stored in
+the clear, since it is needed to reliably identify the key itself.
+
 Encryption modes and usage
 ==========================
 
@@ -273,21 +377,38 @@ Setting an encryption policy
 The FS_IOC_SET_ENCRYPTION_POLICY ioctl sets an encryption policy on an
 empty directory or verifies that a directory or regular file already
 has the specified encryption policy.  It takes in a pointer to a
-:c:type:`struct fscrypt_policy`, defined as follows::
+:c:type:`struct fscrypt_policy_v1` or a :c:type:`struct
+fscrypt_policy_v2`, defined as follows::
 
-    #define FSCRYPT_KEY_DESCRIPTOR_SIZE  8
-
-    struct fscrypt_policy {
+    #define FSCRYPT_POLICY_V1               0
+    #define FSCRYPT_KEY_DESCRIPTOR_SIZE     8
+    struct fscrypt_policy_v1 {
             __u8 version;
             __u8 contents_encryption_mode;
             __u8 filenames_encryption_mode;
             __u8 flags;
             __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
     };
+    #define fscrypt_policy  fscrypt_policy_v1
+
+    #define FSCRYPT_POLICY_V2               2
+    #define FSCRYPT_KEY_IDENTIFIER_SIZE     16
+    struct fscrypt_policy_v2 {
+            __u8 version;
+            __u8 contents_encryption_mode;
+            __u8 filenames_encryption_mode;
+            __u8 flags;
+            __u8 __reserved[4];
+            __u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+    };
 
 This structure must be initialized as follows:
 
-- ``version`` must be 0.
+- ``version`` must be FSCRYPT_POLICY_V1 (0) if the struct is
+  :c:type:`fscrypt_policy_v1` or FSCRYPT_POLICY_V2 (2) if the struct
+  is :c:type:`fscrypt_policy_v2`.  (Note: we refer to the original
+  policy version as "v1", though its version code is really 0.)  For
+  new encrypted directories, use v2 policies.
 
 - ``contents_encryption_mode`` and ``filenames_encryption_mode`` must
   be set to constants from ``<linux/fs.h>`` which identify the
@@ -297,21 +418,30 @@ This structure must be initialized as follows:
 
 - ``flags`` must contain a value from ``<linux/fs.h>`` which
   identifies the amount of NUL-padding to use when encrypting
-  filenames.  If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3).  In
-  addition, if the chosen encryption modes are both
+  filenames.  If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3).
+  Additionally, if the encryption modes are both
   FSCRYPT_MODE_ADIANTUM, this can contain
-  FSCRYPT_POLICY_FLAG_DIRECT_KEY to specify that the master key should
-  be used directly, without key derivation.
+  FSCRYPT_POLICY_FLAG_DIRECT_KEY; see `DIRECT_KEY and per-mode keys`_.
 
-- ``master_key_descriptor`` specifies how to find the master key in
-  the keyring; see `Adding keys`_.  It is up to userspace to choose a
-  unique ``master_key_descriptor`` for each master key.  The e4crypt
-  and fscrypt tools use the first 8 bytes of
+- For v2 encryption policies, ``__reserved`` must be zeroed.
+
+- For v1 encryption policies, ``master_key_descriptor`` specifies how
+  to find the master key in a keyring; see `Adding keys`_.  It is up
+  to userspace to choose a unique ``master_key_descriptor`` for each
+  master key.  The e4crypt and fscrypt tools use the first 8 bytes of
   ``SHA-512(SHA-512(master_key))``, but this particular scheme is not
   required.  Also, the master key need not be in the keyring yet when
   FS_IOC_SET_ENCRYPTION_POLICY is executed.  However, it must be added
   before any files can be created in the encrypted directory.
 
+  For v2 encryption policies, ``master_key_descriptor`` has been
+  replaced with ``master_key_identifier``, which is longer and cannot
+  be arbitrarily chosen.  Instead, the key must first be added using
+  FS_IOC_ADD_ENCRYPTION_KEY, as described in `Adding keys`_.  Then,
+  the ``key_spec.u.identifier`` the kernel returned in the
+  :c:type:`struct fscrypt_add_key_arg` must be used as the
+  ``master_key_identifier`` in the :c:type:`struct fscrypt_policy_v2`.
+
 If the file is not yet encrypted, then FS_IOC_SET_ENCRYPTION_POLICY
 verifies that the file is an empty directory.  If so, the specified
 encryption policy is assigned to the directory, turning it into an
@@ -327,6 +457,15 @@ policy exactly matches the actual one.  If they match, then the ioctl
 returns 0.  Otherwise, it fails with EEXIST.  This works on both
 regular files and directories, including nonempty directories.
 
+When a v2 encryption policy is assigned to a directory, it is also
+required that either the specified key has been added by the current
+user or that the caller has CAP_FOWNER in the initial user namespace.
+(This is needed to prevent a user from encrypting their data with
+another user's key.)  The key must remain added while
+FS_IOC_SET_ENCRYPTION_POLICY is executing.  However, if the new
+encrypted directory does not need to be accessed immediately, then the
+key can be removed right away afterwards.
+
 Note that the ext4 filesystem does not allow the root directory to be
 encrypted, even if it is empty.  Users who want to encrypt an entire
 filesystem with one key should consider using dm-crypt instead.
@@ -339,7 +478,11 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors:
 - ``EEXIST``: the file is already encrypted with an encryption policy
   different from the one specified
 - ``EINVAL``: an invalid encryption policy was specified (invalid
-  version, mode(s), or flags)
+  version, mode(s), or flags; or reserved bits were set)
+- ``ENOKEY``: a v2 encryption policy was specified, but the key with
+  the specified ``master_key_identifier`` has not been added, nor does
+  the process have the CAP_FOWNER capability in the initial user
+  namespace
 - ``ENOTDIR``: the file is unencrypted and is a regular file, not a
   directory
 - ``ENOTEMPTY``: the file is unencrypted and is a nonempty directory
@@ -358,25 +501,78 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors:
 Getting an encryption policy
 ----------------------------
 
-The FS_IOC_GET_ENCRYPTION_POLICY ioctl retrieves the :c:type:`struct
-fscrypt_policy`, if any, for a directory or regular file.  See above
-for the struct definition.  No additional permissions are required
-beyond the ability to open the file.
+Two ioctls are available to get a file's encryption policy:
+
+- FS_IOC_GET_ENCRYPTION_POLICY_EX
+- FS_IOC_GET_ENCRYPTION_POLICY
+
+The extended (_EX) version of the ioctl is more general and is
+recommended to use when possible.  However, on older kernels only the
+original ioctl is available.  Applications should try the extended
+version, and if it fails with ENOTTY fall back to the original
+version.
+
+Preferred method
+~~~~~~~~~~~~~~~~
+
+The FS_IOC_GET_ENCRYPTION_POLICY_EX ioctl retrieves the encryption
+policy, if any, for a directory or regular file.  No additional
+permissions are required beyond the ability to open the file.  It
+takes in a pointer to a :c:type:`struct fscrypt_get_policy_ex_arg`,
+defined as follows::
+
+    struct fscrypt_get_policy_ex_arg {
+            __u64 policy_size; /* input/output */
+            union {
+                    __u8 version;
+                    struct fscrypt_policy_v1 v1;
+                    struct fscrypt_policy_v2 v2;
+            } policy; /* output */
+    };
+
+The caller must initialize ``policy_size`` to the size available for
+the policy struct, i.e. ``sizeof(arg.policy)``.
+
+On success, the policy struct is returned in ``policy``, and its
+actual size is returned in ``policy_size``.  ``policy.version`` should
+be checked to determine the version of policy returned.  Note that the
+version code for the "v1" policy is actually 0 (FSCRYPT_POLICY_V1).
 
-FS_IOC_GET_ENCRYPTION_POLICY can fail with the following errors:
+FS_IOC_GET_ENCRYPTION_POLICY_EX can fail with the following errors:
 
 - ``EINVAL``: the file is encrypted, but it uses an unrecognized
-  encryption context format
+  encryption policy version
 - ``ENODATA``: the file is not encrypted
-- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``ENOTTY``: this type of filesystem does not implement encryption,
+  or this kernel is too old to support FS_IOC_GET_ENCRYPTION_POLICY_EX
+  (try FS_IOC_GET_ENCRYPTION_POLICY instead)
 - ``EOPNOTSUPP``: the kernel was not configured with encryption
   support for this filesystem
+- ``EOVERFLOW``: the file is encrypted and uses a recognized
+  encryption policy version, but the policy struct does not fit into
+  the provided buffer
 
 Note: if you only need to know whether a file is encrypted or not, on
 most filesystems it is also possible to use the FS_IOC_GETFLAGS ioctl
 and check for FS_ENCRYPT_FL, or to use the statx() system call and
 check for STATX_ATTR_ENCRYPTED in stx_attributes.
 
+Legacy method
+~~~~~~~~~~~~~
+
+The FS_IOC_GET_ENCRYPTION_POLICY ioctl can also retrieve the
+encryption policy, if any, for a directory or regular file.  However,
+unlike the extended version (FS_IOC_GET_ENCRYPTION_POLICY_EX),
+FS_IOC_GET_ENCRYPTION_POLICY only supports the original policy
+version.  It takes in a pointer directly to a :c:type:`struct
+fscrypt_policy_v1` rather than a :c:type:`struct
+fscrypt_get_policy_ex_arg`.
+
+The error codes for FS_IOC_GET_ENCRYPTION_POLICY are the same as those
+for FS_IOC_GET_ENCRYPTION_POLICY_EX, except that
+FS_IOC_GET_ENCRYPTION_POLICY also returns ``EINVAL`` if the file is
+encrypted using a newer encryption policy version.
+
 Getting the per-filesystem salt
 -------------------------------
 
@@ -392,8 +588,98 @@ generate and manage any needed salt(s) in userspace.
 Adding keys
 -----------
 
-To provide a master key, userspace must add it to an appropriate
-keyring using the add_key() system call (see:
+Preferred method
+~~~~~~~~~~~~~~~~
+
+The FS_IOC_ADD_ENCRYPTION_KEY ioctl adds a master encryption key to
+the filesystem, making all files on the filesystem which were
+encrypted using that key appear "unlocked", i.e. in plaintext form.
+It can be executed on any file or directory on the target filesystem,
+but using the filesystem's root directory is recommended.  It takes in
+a pointer to a :c:type:`struct fscrypt_add_key_arg`, defined as
+follows::
+
+    struct fscrypt_add_key_arg {
+            struct fscrypt_key_specifier key_spec;
+            __u32 raw_size;
+            __u32 __reserved[9];
+            __u8 raw[];
+    };
+
+    struct fscrypt_key_specifier {
+    #define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR        1
+    #define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER        2
+            __u32 type;
+            __u32 __reserved;
+            union {
+                    __u8 __reserved[32]; /* reserve some extra space */
+                    __u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+                    __u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+            } u;
+    };
+
+:c:type:`struct fscrypt_add_key_arg` must be zeroed, then initialized
+as follows:
+
+- If the key is being added for use by v1 encryption policies, then
+  ``key_spec.type`` must contain FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR, and
+  ``key_spec.u.descriptor`` must contain the descriptor of the key
+  being added, corresponding to the value in the
+  ``master_key_descriptor`` field of :c:type:`struct
+  fscrypt_policy_v1`.  To add this type of key, the calling process
+  must have the CAP_SYS_ADMIN capability in the initial user
+  namespace.
+
+  Alternatively, if the key is being added for use by v2 encryption
+  policies, then ``key_spec.type`` must contain
+  FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER, and ``key_spec.u.identifier`` is
+  an *output* field which the kernel fills in with a cryptographic
+  hash of the key.  To add this type of key, the calling process does
+  not need any privileges.  However, the number of keys that can be
+  added is limited by the user's quota for the keyrings service (see
+  ``Documentation/security/keys/core.rst``).
+
+- ``raw_size`` must be the size of the ``raw`` key provided, in bytes.
+
+- ``raw`` is a variable-length field which must contain the actual
+  key, ``raw_size`` bytes long.
+
+FS_IOC_ADD_ENCRYPTION_KEY can fail with the following errors:
+
+- ``EACCES``: FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR was specified, but the
+  caller does not have the CAP_SYS_ADMIN capability in the initial
+  user namespace
+- ``EDQUOT``: the key quota for this user would be exceeded by adding
+  the key
+- ``EINVAL``: invalid key size or key specifier type, or reserved bits
+  were set
+- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``EOPNOTSUPP``: the kernel was not configured with encryption
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+
+Legacy method
+~~~~~~~~~~~~~
+
+For v1 encryption policies, a master encryption key can also be
+provided by adding it to a process-subscribed keyring, e.g. to a
+session keyring, or to a user keyring if the user keyring is linked
+into the session keyring.
+
+This method is deprecated (and not supported for v2 encryption
+policies) for several reasons.  First, it cannot be used in
+combination with FS_IOC_REMOVE_ENCRYPTION_KEY (see `Removing keys`_),
+so for removing a key a workaround such as keyctl_unlink() in
+combination with ``sync; echo 2 > /proc/sys/vm/drop_caches`` would
+have to be used.  Second, it doesn't match the fact that the
+locked/unlocked status of encrypted files (i.e. whether they appear to
+be in plaintext form or in ciphertext form) is global.  This mismatch
+has caused much confusion as well as real problems when processes
+running under different UIDs, such as a ``sudo`` command, need to
+access encrypted files.
+
+Nevertheless, to add a key to one of the process-subscribed keyrings,
+the add_key() system call can be used (see:
 ``Documentation/security/keys/core.rst``).  The key type must be
 "logon"; keys of this type are kept in kernel memory and cannot be
 read back by userspace.  The key description must be "fscrypt:"
@@ -401,12 +687,12 @@ followed by the 16-character lower case hex representation of the
 ``master_key_descriptor`` that was set in the encryption policy.  The
 key payload must conform to the following structure::
 
-    #define FSCRYPT_MAX_KEY_SIZE 64
+    #define FSCRYPT_MAX_KEY_SIZE            64
 
     struct fscrypt_key {
-            u32 mode;
-            u8 raw[FSCRYPT_MAX_KEY_SIZE];
-            u32 size;
+            __u32 mode;
+            __u8 raw[FSCRYPT_MAX_KEY_SIZE];
+            __u32 size;
     };
 
 ``mode`` is ignored; just set it to 0.  The actual key is provided in
@@ -418,26 +704,145 @@ with a filesystem-specific prefix such as "ext4:".  However, the
 filesystem-specific prefixes are deprecated and should not be used in
 new programs.
 
-There are several different types of keyrings in which encryption keys
-may be placed, such as a session keyring, a user session keyring, or a
-user keyring.  Each key must be placed in a keyring that is "attached"
-to all processes that might need to access files encrypted with it, in
-the sense that request_key() will find the key.  Generally, if only
-processes belonging to a specific user need to access a given
-encrypted directory and no session keyring has been installed, then
-that directory's key should be placed in that user's user session
-keyring or user keyring.  Otherwise, a session keyring should be
-installed if needed, and the key should be linked into that session
-keyring, or in a keyring linked into that session keyring.
-
-Note: introducing the complex visibility semantics of keyrings here
-was arguably a mistake --- especially given that by design, after any
-process successfully opens an encrypted file (thereby setting up the
-per-file key), possessing the keyring key is not actually required for
-any process to read/write the file until its in-memory inode is
-evicted.  In the future there probably should be a way to provide keys
-directly to the filesystem instead, which would make the intended
-semantics clearer.
+Removing keys
+-------------
+
+The FS_IOC_REMOVE_ENCRYPTION_KEY ioctl can be used to remove a master
+encryption key from the kernel, wiping the corresponding secrets from
+memory and causing any files which were "unlocked" with the key to
+appear "locked" again.  It can be executed on any file or directory on
+the target filesystem, but using the filesystem's root directory is
+recommended.  It takes in a pointer to a :c:type:`struct
+fscrypt_remove_key_arg`, defined as follows::
+
+    struct fscrypt_remove_key_arg {
+            struct fscrypt_key_specifier key_spec;
+    #define FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS       0x00000001
+            __u32 flags;
+            __u32 __reserved[5];
+    };
+
+This structure must be zeroed, then initialized as follows:
+
+- The key to remove is specified by ``key_spec``:
+
+    - To remove a key used by v1 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
+      in ``key_spec.u.descriptor``.  To remove this type of key, the
+      calling process must have the CAP_SYS_ADMIN capability in the
+      initial user namespace.
+
+    - To remove a key used by v2 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
+      in ``key_spec.u.identifier``.  To remove this type of key, no
+      privileges are needed.  However, users can only remove keys that
+      they added themselves, subject to privileged override with
+      FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS.
+
+- ``flags`` can contain the following flags:
+
+    - ``FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS`` specifies that the key
+      should be removed even if it has also been added by other users.
+      Specifying this flag requires the CAP_SYS_ADMIN capability in
+      the initial user namespace.
+
+FS_IOC_REMOVE_ENCRYPTION_KEY can fail with the following errors:
+
+- ``EACCES``: The FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR key specifier type
+  and/or the FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS flag was specified, but
+  the caller does not have the CAP_SYS_ADMIN capability in the initial
+  user namespace
+- ``EBUSY``: the master key secret was wiped from memory, but some
+  files which were unlocked with it are still in use.  Such files
+  could not be locked, nor could their per-file keys be wiped from
+  memory.  The ioctl may be retried later to re-attempt locking the
+  remaining files.  Note: if the files cease being used, the key
+  removal may (but is not guaranteed to) complete before this ioctl is
+  retried; in this case, retrying this ioctl will return ``ENOKEY``.
+- ``EINVAL``: invalid flags or key specifier type, or reserved bits
+  were set
+- ``ENOKEY``: the key is not present or has already been fully removed
+- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``EOPNOTSUPP``: the kernel was not configured with encryption
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+- ``EUSERS``: the key cannot be removed because other users have added
+  it too
+
+Before using this ioctl, read the `Kernel memory compromise`_ section
+for a discussion of the security goals and limitations of this ioctl.
+
+Getting key status
+------------------
+
+The FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl retrieves the status of a
+master encryption key.  It can be executed on any file or directory on
+the target filesystem, but using the filesystem's root directory is
+recommended.  It takes in a pointer to a :c:type:`struct
+fscrypt_get_key_status_arg`, defined as follows::
+
+    struct fscrypt_get_key_status_arg {
+            /* input */
+            struct fscrypt_key_specifier key_spec;
+            __u32 __reserved[6];
+
+            /* output */
+    #define FSCRYPT_KEY_STATUS_ABSENT               1
+    #define FSCRYPT_KEY_STATUS_PRESENT              2
+    #define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED 3
+            __u32 status;
+    #define FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF   0x00000001
+            __u32 status_flags;
+            __u32 user_count;
+            __u32 __out_reserved[13];
+    };
+
+The caller must zero all input fields, then fill in ``key_spec``:
+
+    - To get the status of a key for v1 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
+      in ``key_spec.u.descriptor``.
+
+    - To get the status of a key for v2 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
+      in ``key_spec.u.identifier``.
+
+On success, 0 is returned and the kernel fills in the output fields:
+
+- ``status`` indicates whether the key is absent, present, or
+  incompletely removed.  Incompletely removed means that the master
+  secret has been removed, but some files are still in use; i.e.,
+  FS_IOC_REMOVE_ENCRYPTION_KEY returned EBUSY.
+
+- ``status_flags`` can contain the following flags:
+
+    - ``FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF`` indicates that the key
+      has added by the current user.  This is only set for keys
+      identified by ``identifier`` rather than by ``descriptor``.
+
+- ``user_count`` specifies the number of users who have added the key.
+  This is only set for keys identified by ``identifier`` rather than
+  by ``descriptor``.
+
+FS_IOC_GET_ENCRYPTION_KEY_STATUS can fail with the following errors:
+
+- ``EINVAL``: invalid key specifier type, or reserved bits were set
+- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``EOPNOTSUPP``: the kernel was not configured with encryption
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+
+Among other use cases, FS_IOC_GET_ENCRYPTION_KEY_STATUS might be
+useful for determining whether the key for a given encrypted directory
+needs to be added before prompting the user for the passphrase needed
+to derive the key.
+
+FS_IOC_GET_ENCRYPTION_KEY_STATUS can only get the status of keys in
+the filesystem-level keyring, i.e. the keyring managed by
+FS_IOC_ADD_ENCRYPTION_KEY and FS_IOC_REMOVE_ENCRYPTION_KEY.  It cannot
+get the status of a key that has only been added for use by v1
+encryption policies using the legacy mechanism involving
+process-subscribed keyrings.
 
 Access semantics
 ================
@@ -500,7 +905,7 @@ Without the key
 
 Some filesystem operations may be performed on encrypted regular
 files, directories, and symlinks even before their encryption key has
-been provided:
+been added, or after their encryption key has been removed:
 
 - File metadata may be read, e.g. using stat().
 
@@ -565,20 +970,20 @@ Encryption context
 ------------------
 
 An encryption policy is represented on-disk by a :c:type:`struct
-fscrypt_context`.  It is up to individual filesystems to decide where
-to store it, but normally it would be stored in a hidden extended
-attribute.  It should *not* be exposed by the xattr-related system
-calls such as getxattr() and setxattr() because of the special
-semantics of the encryption xattr.  (In particular, there would be
-much confusion if an encryption policy were to be added to or removed
-from anything other than an empty directory.)  The struct is defined
-as follows::
+fscrypt_context_v1` or a :c:type:`struct fscrypt_context_v2`.  It is
+up to individual filesystems to decide where to store it, but normally
+it would be stored in a hidden extended attribute.  It should *not* be
+exposed by the xattr-related system calls such as getxattr() and
+setxattr() because of the special semantics of the encryption xattr.
+(In particular, there would be much confusion if an encryption policy
+were to be added to or removed from anything other than an empty
+directory.)  These structs are defined as follows::
 
-    #define FSCRYPT_KEY_DESCRIPTOR_SIZE  8
     #define FS_KEY_DERIVATION_NONCE_SIZE 16
 
-    struct fscrypt_context {
-            u8 format;
+    #define FSCRYPT_KEY_DESCRIPTOR_SIZE  8
+    struct fscrypt_context_v1 {
+            u8 version;
             u8 contents_encryption_mode;
             u8 filenames_encryption_mode;
             u8 flags;
@@ -586,12 +991,23 @@ as follows::
             u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
     };
 
-Note that :c:type:`struct fscrypt_context` contains the same
-information as :c:type:`struct fscrypt_policy` (see `Setting an
-encryption policy`_), except that :c:type:`struct fscrypt_context`
-also contains a nonce.  The nonce is randomly generated by the kernel
-and is used to derive the inode's encryption key as described in
-`Per-file keys`_.
+    #define FSCRYPT_KEY_IDENTIFIER_SIZE  16
+    struct fscrypt_context_v2 {
+            u8 version;
+            u8 contents_encryption_mode;
+            u8 filenames_encryption_mode;
+            u8 flags;
+            u8 __reserved[4];
+            u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+            u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
+    };
+
+The context structs contain the same information as the corresponding
+policy structs (see `Setting an encryption policy`_), except that the
+context structs also contain a nonce.  The nonce is randomly generated
+by the kernel and is used as KDF input or as a tweak to cause
+different files to be encrypted differently; see `Per-file keys`_ and
+`DIRECT_KEY and per-mode keys`_.
 
 Data path changes
 -----------------
-- 
2.22.0


^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h>
  2019-07-26 22:41 ` [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h> Eric Biggers
@ 2019-07-28 15:08   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 15:08 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:26PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> More fscrypt definitions are being added, and we shouldn't use a
> disproportionate amount of space in <linux/fs.h> for fscrypt stuff.
> So move the fscrypt definitions to a new header <linux/fscrypt.h>.
> 
> For source compatibility with existing userspace programs, <linux/fs.h>
> still includes the new header.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good, feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>


^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 04/16] fscrypt: add ->ci_inode to fscrypt_info
  2019-07-26 22:41 ` [PATCH v7 04/16] fscrypt: add ->ci_inode to fscrypt_info Eric Biggers
@ 2019-07-28 15:09   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 15:09 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:29PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add an inode back-pointer to 'struct fscrypt_info', such that
> inode->i_crypt_info->ci_inode == inode.
> 
> This will be useful for:
> 
> 1. Evicting the inodes when a fscrypt key is removed, since we'll track
>    the inodes using a given key by linking their fscrypt_infos together,
>    rather than the inodes directly.  This avoids bloating 'struct inode'
>    with a new list_head.
> 
> 2. Simplifying the per-file key setup, since the inode pointer won't
>    have to be passed around everywhere just in case something goes wrong
>    and it's needed for fscrypt_warn().
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good, feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c
  2019-07-26 22:41 ` [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c Eric Biggers
@ 2019-07-28 15:40   ` Theodore Y. Ts'o
  2019-07-29 19:37     ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 15:40 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:30PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> In preparation for introducing v2 encryption policies which will find
> and derive encryption keys differently from the current v1 encryption
> policies, refactor the v1 policy-specific key setup code from keyinfo.c
> into keysetup_legacy.c.  Then rename keyinfo.c to keysetup.c.

I'd use keysetup_v1.c, myself.  We can hope that we've gotten it right
with v2 and we'll never need to do another version, but *something* is
going to come up eventually which will require a v3 keysetup , whether
it's post-quantuum cryptography or something else we can't anticipate
right now.

For an example of the confusion that can result, one good example is
in the fs/quota subsystem, where QFMT_VFS_OLD, QFMT_VFS_V0, and
QFMT_VFS_V1 maps to quota_v1 and quota_v2 in an amusing and
non-obvious way.  (Go ahead, try to guess before you go look at the
code.  :-)

Other than that, looks good.  We can always move code around or rename
files in the future, so I'm not going to insist on doing it now (but
it would be my preference).

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted
						

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  2019-07-26 22:41 ` [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Eric Biggers
@ 2019-07-28 18:50   ` Theodore Y. Ts'o
  2019-07-29 19:46     ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 18:50 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:31PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a new fscrypt ioctl, FS_IOC_ADD_ENCRYPTION_KEY.  This ioctl adds an
> encryption key to the filesystem's fscrypt keyring ->s_master_keys,
> making any files encrypted with that key appear "unlocked".

Note: it think it's going to be useful to make the keyring id
available someplace like /sys/fs/<fs>/<blkdev>/keyring, or preferably
in the new fsinfo system call.  Yes, the system administrator can paw
through /proc/keys and try to figure it out, but it will be nicer if
there's a direct way to do that.

For that matter, we could just add a new ioctl which returns the file
system's keyring id.  That way an application program won't have to
try to figure out what a file's underlying sb->s_id happens to be.
(Especially if things like overlayfs are involved.)

> diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
> index 29a945d165def..93d6eabaa7de4 100644
> --- a/include/uapi/linux/fscrypt.h
> +++ b/include/uapi/linux/fscrypt.h
> +
> +struct fscrypt_key_specifier {
> +#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR	1
> +	__u32 type;
> +	__u32 __reserved;

Can you move the definition of FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR
outside of the structure definition, and then add a comment about what
is a "descriptor" key spec?  (And then in a later patch, please add a
comment about what is an "identifier" key type.)  There's an
explanation in Documentation/filesystems/fscrypt.rst, I know, but a
one or two line comment plus a pointer to
Documentation/filesystems/fscrypt.rst in the header file would be
really helpful.

Otherwise, it looks good.   Feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-07-26 22:41 ` [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl Eric Biggers
@ 2019-07-28 19:24   ` Theodore Y. Ts'o
  2019-07-29 19:58     ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 19:24 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:32PM -0700, Eric Biggers wrote:
> +	fscrypt_warn(NULL,
> +		     "%s: %zu inodes still busy after removing key with description %*phN, including ino %lu (%s)",

nit: s/inodes/inode(s)/

> +
> +/*
> + * Try to remove an fscrypt master encryption key.  If other users have also
> + * added the key, we'll remove the current user's usage of the key, then return
> + * -EUSERS.  Otherwise we'll continue on and try to actually remove the key.

Nit: this should be moved to patch #11

Also, perror(EUSERS) will display "Too many users" which is going to
be confusing.  I understand why you chose this; we would like to
distinguish between there are still inodes using this key, and there
are other users using this key.

Do we really need to return EUSERS in this case?  It's actually not an
*error* that other users are using the key.  After all, the unlink(2)
system call doesn't return an advisory error when you delete a file
which has other hard links.  And an application which does care about
this detail can always call FS_IOC_ENCRYPTION_KEY_STATUS() and check
user_count.

Other than these nits, looks good.  Feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 08/16] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl
  2019-07-26 22:41 ` [PATCH v7 08/16] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl Eric Biggers
@ 2019-07-28 19:30   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 19:30 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:33PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a new fscrypt ioctl, FS_IOC_GET_ENCRYPTION_KEY_STATUS.  Given a key
> specified by 'struct fscrypt_key_specifier' (the same way a key is
> specified for the other fscrypt key management ioctls), it returns
> status information in a 'struct fscrypt_get_key_status_arg'.
> 
> The main motivation for this is that applications need to be able to
> check whether an encrypted directory is "unlocked" or not, so that they
> can add the key if it is not, and avoid adding the key (which may
> involve prompting the user for a passphrase) if it already is.
> 
> It's possible to use some workarounds such as checking whether opening a
> regular file fails with ENOKEY, or checking whether the filenames "look
> like gibberish" or not.  However, no workaround is usable in all cases.
> 
> Like the other key management ioctls, the keyrings syscalls may seem at
> first to be a good fit for this.  Unfortunately, they are not.  Even if
> we exposed the keyring ID of the ->s_master_keys keyring and gave
> everyone Search permission on it (note: currently the keyrings
> permission system would also allow everyone to "invalidate" the keyring
> too), the fscrypt keys have an additional state that doesn't map cleanly
> to the keyrings API: the secret can be removed, but we can be still
> tracking the files that were using the key, and the removal can be
> re-attempted or the secret added again.
> 
> After later patches, some applications will also need a way to determine
> whether a key was added by the current user vs. by some other user.
> Reserved fields are included in fscrypt_get_key_status_arg for this and
> other future extensions.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good, feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>


^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation
  2019-07-26 22:41 ` [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation Eric Biggers
@ 2019-07-28 19:39   ` Theodore Y. Ts'o
  2019-07-29 20:29     ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 19:39 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:34PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add an implementation of HKDF (RFC 5869) to fscrypt, for the purpose of
> deriving additional key material from the fscrypt master keys for v2
> encryption policies.  HKDF is a key derivation function built on top of
> HMAC.  We choose SHA-512 for the underlying unkeyed hash, and use an
> "hmac(sha512)" transform allocated from the crypto API.
> 
> We'll be using this to replace the AES-ECB based KDF currently used to
> derive the per-file encryption keys.  While the AES-ECB based KDF is
> believed to meet the original security requirements, it is nonstandard
> and has problems that don't exist in modern KDFs such as HKDF:
> 
> 1. It's reversible.  Given a derived key and nonce, an attacker can
>    easily compute the master key.  This is okay if the master key and
>    derived keys are equally hard to compromise, but now we'd like to be
>    more robust against threats such as a derived key being compromised
>    through a timing attack, or a derived key for an in-use file being
>    compromised after the master key has already been removed.
> 
> 2. It doesn't evenly distribute the entropy from the master key; each 16
>    input bytes only affects the corresponding 16 output bytes.
> 
> 3. It isn't easily extensible to deriving other values or keys, such as
>    a public hash for securely identifying the key, or per-mode keys.
>    Per-mode keys will be immediately useful for Adiantum encryption, for
>    which fscrypt currently uses the master key directly, introducing
>    unnecessary usage constraints.  Per-mode keys will also be useful for
>    hardware inline encryption, which is currently being worked on.
> 
> HKDF solves all the above problems.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Unless I missed something there's nothing here which is fscrypt
specific.  Granted that it's somewhat unlikely that someone would want
to implement (the very bloated) IKE from IPSEC in the kernel, I wonder
if there might be other users of HKDF, and whether this would be
better placed in lib/ or crypto/ instead of fs/crypto?

Other than that, looks good.  Feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>


^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 10/16] fscrypt: v2 encryption policy support
  2019-07-26 22:41 ` [PATCH v7 10/16] fscrypt: v2 encryption policy support Eric Biggers
@ 2019-07-28 21:17   ` Theodore Y. Ts'o
  2019-07-29 20:46     ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 21:17 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:35PM -0700, Eric Biggers wrote:
> @@ -319,6 +329,31 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
>  	if (!capable(CAP_SYS_ADMIN))
>  		goto out_wipe_secret;
>  
> +	if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {

This should be "== FSCRYPT_KEY_SPEC_TYPE_INDENTIFIER" instead.  That's
because you use the identifier part of the union:

> +		/* Calculate the key identifier and return it to userspace. */
> +		err = fscrypt_hkdf_expand(&secret.hkdf,
> +					  HKDF_CONTEXT_KEY_IDENTIFIER,
> +					  NULL, 0, arg.key_spec.u.identifier,

If we ever add a new key specifier type, and alternative in the union,
this is going to come back to bite us.

> +	if (policy->version == FSCRYPT_POLICY_V1) {
> +		/*
> +		 * The original encryption policy version provided no way of
> +		 * verifying that the correct master key was supplied, which was
> +		 * insecure in scenarios where multiple users have access to the
> +		 * same encrypted files (even just read-only access).

Which scenario do you have in mind?  With read-only access, Alice can
fetch the encryption policy for a directory, and introduce a key with
the same descriptor, but the "wrong" key, but that's only going to
affect Alice's use of the key.  It won't affect what key is used by
Bob, since Alice doesn't have write access to Bob's keyrings.

If what you mean is the risk when there is a single global
filesystem-specific keyring, where Alice could introduce a "wrong" key
identified with a specific descriptor, then sure, Alice could trick
Bob into encrypting his data with the wrong key (one known to Alice).
But we don't allow keys usable by V1 policies to be used in the
filesystem-specific keyring, do we?

						- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 11/16] fscrypt: allow unprivileged users to add/remove keys for v2 policies
  2019-07-26 22:41 ` [PATCH v7 11/16] fscrypt: allow unprivileged users to add/remove keys for v2 policies Eric Biggers
@ 2019-07-28 21:22   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 21:22 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:36PM -0700, Eric Biggers wrote:
> diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
> index 56e085c2ed8c6..307533d4d7c51 100644
> --- a/fs/crypto/keyring.c
> +++ b/fs/crypto/keyring.c
> +		if (mk->mk_users->keys.nr_leaves_on_tree != 0) {
> +			/*
> +			 * Other users have still added the key too.  We removed
> +			 * the current user's usage of the key if there was one,
> +			 * but we still can't remove the key itself.
> +			 */
> +			err = -EUSERS;
> +			up_write(&key->sem);
> +			goto out_put_key;

I commented about this on an earlier patch, but I'm not convinced we
should be returning EUSERS here.  Returning success might be a better
choice.

					- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 12/16] fscrypt: require that key be added when setting a v2 encryption policy
  2019-07-26 22:41 ` [PATCH v7 12/16] fscrypt: require that key be added when setting a v2 encryption policy Eric Biggers
@ 2019-07-28 21:24   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 21:24 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:37PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> By looking up the master keys in a filesystem-level keyring rather than
> in the calling processes' key hierarchy, it becomes possible for a user
> to set an encryption policy which refers to some key they don't actually
> know, then encrypt their files using that key.  Cryptographically this
> isn't much of a problem, but the semantics of this would be a bit weird.
> Thus, enforce that a v2 encryption policy can only be set if the user
> has previously added the key, or has capable(CAP_FOWNER).
> 
> We tolerate that this problem will continue to exist for v1 encryption
> policies, however; there is no way around that.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good, feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

					- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 13/16] ext4: wire up new fscrypt ioctls
  2019-07-26 22:41 ` [PATCH v7 13/16] ext4: wire up new fscrypt ioctls Eric Biggers
@ 2019-07-28 21:24   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-28 21:24 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:38PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Wire up the new ioctls for adding and removing fscrypt keys to/from the
> filesystem, and the new ioctl for retrieving v2 encryption policies.
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY also required making ext4_drop_inode() call
> fscrypt_drop_inode().
> 
> For more details see Documentation/filesystems/fscrypt.rst and the
> fscrypt patches that added the implementation of these ioctls.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good, feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 16/16] fscrypt: document the new ioctls and policy version
  2019-07-26 22:41 ` [PATCH v7 16/16] fscrypt: document the new ioctls and policy version Eric Biggers
@ 2019-07-29  2:00   ` Theodore Y. Ts'o
  2019-07-29 21:36     ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-29  2:00 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:41PM -0700, Eric Biggers wrote:
> +- The kernel cannot magically wipe copies of the master key(s) that
> +  userspace might have as well.  Therefore, userspace must wipe all
> +  copies of the master key(s) it makes as well.  Naturally, the same
> +  also applies to all higher levels in the key hierarchy.  Userspace
> +  should also follow other security precautions such as mlock()ing
> +  memory containing keys to prevent it from being swapped out.

Normally, shouldn't userspace have wiped all copies of the master key
after they have called ADD_KEY?  Why should they be left hanging
around?  Waiting until REMOVE_KEY to remove other copies of the master
key seems.... late.

> +- In general, decrypted contents and filenames in the kernel VFS
> +  caches are freed but not wiped.  Therefore, portions thereof may be
> +  recoverable from freed memory, even after the corresponding key(s)
> +  were wiped.  To partially solve this, you can set
> +  CONFIG_PAGE_POISONING=y in your kernel config and add page_poison=1
> +  to your kernel command line.  However, this has a performance cost.

... and even this won't help if you have swap configured....

> +v1 encryption policies have some weaknesses with respect to online
> +attacks:
> +
> +- There is no verification that the provided master key is correct.
> +  Consequently, malicious users can associate the wrong key with
> +  encrypted files, even files to which they have only read-only
> +  access.

Yes, but they won't be able to trick other users into using that
incorrect key.  With the old interface, it gets written into the
user's session keyring, which won't get used by another user.  And
with the newer interface, only root is allowed to set v1 key.

> +Master keys should be pseudorandom, i.e. indistinguishable from random
> +bytestrings of the same length.  This implies that users **must not**
> +directly use a password as a master key, zero-pad a shorter key, or
> +repeat a shorter key.

These paragraphs starts a bit funny, since we first say "should" in
the first sentence, and then it's followed up by "**must not**" in the
second sentence.  Basically, they *could* do this, but it would just
weaken the security of the system significantly.

At the very least, we should explain the basis of the recommendation.

> +The KDF used for a particular master key differs depending on whether
> +the key is used for v1 encryption policies or for v2 encryption
> +policies.  Users **must not** use the same key for both v1 and v2
> +encryption policies.

"Must not" seems a bit strong.  If they do, and a v1 per-file key and
nonce leaks out, then the encryption key will be compromised.  So the
strength of the key will be limited by the weaknesses of the v1
scheme.  But it's not like using a that was originally meant for v1,
and then using it for v2, causes any additional weakness.  Right?

    	       	      	  	 - Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c
  2019-07-28 15:40   ` Theodore Y. Ts'o
@ 2019-07-29 19:37     ` Eric Biggers
  0 siblings, 0 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-29 19:37 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

Hi Ted, thanks for the review!

On Sun, Jul 28, 2019 at 11:40:32AM -0400, Theodore Y. Ts'o wrote:
> On Fri, Jul 26, 2019 at 03:41:30PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > In preparation for introducing v2 encryption policies which will find
> > and derive encryption keys differently from the current v1 encryption
> > policies, refactor the v1 policy-specific key setup code from keyinfo.c
> > into keysetup_legacy.c.  Then rename keyinfo.c to keysetup.c.
> 
> I'd use keysetup_v1.c, myself.  We can hope that we've gotten it right
> with v2 and we'll never need to do another version, but *something* is
> going to come up eventually which will require a v3 keysetup , whether
> it's post-quantuum cryptography or something else we can't anticipate
> right now.
> 
> For an example of the confusion that can result, one good example is
> in the fs/quota subsystem, where QFMT_VFS_OLD, QFMT_VFS_V0, and
> QFMT_VFS_V1 maps to quota_v1 and quota_v2 in an amusing and
> non-obvious way.  (Go ahead, try to guess before you go look at the
> code.  :-)
> 
> Other than that, looks good.  We can always move code around or rename
> files in the future, so I'm not going to insist on doing it now (but
> it would be my preference).
> 
> Reviewed-by: Theodore Ts'o <tytso@mit.edu>
> 

Agreed, I'll call it keysetup_v1.c instead.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  2019-07-28 18:50   ` Theodore Y. Ts'o
@ 2019-07-29 19:46     ` Eric Biggers
  2019-07-29 20:14       ` Theodore Y. Ts'o
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-29 19:46 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Sun, Jul 28, 2019 at 02:50:03PM -0400, Theodore Y. Ts'o wrote:
> On Fri, Jul 26, 2019 at 03:41:31PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Add a new fscrypt ioctl, FS_IOC_ADD_ENCRYPTION_KEY.  This ioctl adds an
> > encryption key to the filesystem's fscrypt keyring ->s_master_keys,
> > making any files encrypted with that key appear "unlocked".
> 
> Note: it think it's going to be useful to make the keyring id
> available someplace like /sys/fs/<fs>/<blkdev>/keyring, or preferably
> in the new fsinfo system call.  Yes, the system administrator can paw
> through /proc/keys and try to figure it out, but it will be nicer if
> there's a direct way to do that.
> 
> For that matter, we could just add a new ioctl which returns the file
> system's keyring id.  That way an application program won't have to
> try to figure out what a file's underlying sb->s_id happens to be.
> (Especially if things like overlayfs are involved.)

Keep in mind that the new ioctls (FS_IOC_ADD_ENCRYPTION_KEY,
FS_IOC_REMOVE_ENCRYPTION_KEY, FS_IOC_GET_ENCRYPTION_KEY_STATUS) don't take the
keyring ID as a parameter, since it's already known from the filesystem the
ioctl is executed on.  So there actually isn't much that can be done with the
keyring ID.  But sure, if it's needed later we can add an API to get it.

> 
> > diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
> > index 29a945d165def..93d6eabaa7de4 100644
> > --- a/include/uapi/linux/fscrypt.h
> > +++ b/include/uapi/linux/fscrypt.h
> > +
> > +struct fscrypt_key_specifier {
> > +#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR	1
> > +	__u32 type;
> > +	__u32 __reserved;
> 
> Can you move the definition of FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR
> outside of the structure definition, and then add a comment about what
> is a "descriptor" key spec?  (And then in a later patch, please add a
> comment about what is an "identifier" key type.)  There's an
> explanation in Documentation/filesystems/fscrypt.rst, I know, but a
> one or two line comment plus a pointer to
> Documentation/filesystems/fscrypt.rst in the header file would be
> really helpful.

I'll add a brief comment that explains the key specifier.

I've already added a pointer to Documentation/filesystems/fscrypt.rst at the top
of the header (this was one of the cleanups in v6 => v7):

/*
 * fscrypt user API
 *
 * These ioctls can be used on filesystems that support fscrypt.  See the
 * "User API" section of Documentation/filesystems/fscrypt.rst.
 */

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-07-28 19:24   ` Theodore Y. Ts'o
@ 2019-07-29 19:58     ` Eric Biggers
  2019-07-31 18:38       ` Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-29 19:58 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Sun, Jul 28, 2019 at 03:24:17PM -0400, Theodore Y. Ts'o wrote:
> > +
> > +/*
> > + * Try to remove an fscrypt master encryption key.  If other users have also
> > + * added the key, we'll remove the current user's usage of the key, then return
> > + * -EUSERS.  Otherwise we'll continue on and try to actually remove the key.
> 
> Nit: this should be moved to patch #11
> 
> Also, perror(EUSERS) will display "Too many users" which is going to
> be confusing.  I understand why you chose this; we would like to
> distinguish between there are still inodes using this key, and there
> are other users using this key.
> 
> Do we really need to return EUSERS in this case?  It's actually not an
> *error* that other users are using the key.  After all, the unlink(2)
> system call doesn't return an advisory error when you delete a file
> which has other hard links.  And an application which does care about
> this detail can always call FS_IOC_ENCRYPTION_KEY_STATUS() and check
> user_count.
> 

Returning 0 when the key wasn't fully removed might also be confusing.  But I
guess you're right that returning an error doesn't match how syscalls usually
work.  It did remove the current user's usage of the key, after all, rather than
completely fail.  And as you point out, if someone cares about other users
having added the key, they can use FS_IOC_GET_ENCRYPTION_KEY_STATUS.

So I guess I'll change it to 0.

Thanks!

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  2019-07-29 19:46     ` Eric Biggers
@ 2019-07-29 20:14       ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-29 20:14 UTC (permalink / raw)
  To: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Mon, Jul 29, 2019 at 12:46:45PM -0700, Eric Biggers wrote:
> > For that matter, we could just add a new ioctl which returns the file
> > system's keyring id.  That way an application program won't have to
> > try to figure out what a file's underlying sb->s_id happens to be.
> > (Especially if things like overlayfs are involved.)
> 
> Keep in mind that the new ioctls (FS_IOC_ADD_ENCRYPTION_KEY,
> FS_IOC_REMOVE_ENCRYPTION_KEY, FS_IOC_GET_ENCRYPTION_KEY_STATUS) don't take the
> keyring ID as a parameter, since it's already known from the filesystem the
> ioctl is executed on.  So there actually isn't much that can be done with the
> keyring ID.  But sure, if it's needed later we can add an API to get it.

Yeah, I was thinking about for testing/debugging purposes so that we
could use keyctl to examine the per-file system keyring and see what
keys are attached to a file system.  This is only going to be usable
by root, so I guess we can just try to figure it out by going through
/proc/keys and searching by sb->s_id.  If there are ambiguities that
make this hard to do, we can add an interface to make this easier.

     	       	      	     - Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation
  2019-07-28 19:39   ` Theodore Y. Ts'o
@ 2019-07-29 20:29     ` Eric Biggers
  2019-07-29 21:42       ` James Bottomley
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-29 20:29 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Sun, Jul 28, 2019 at 03:39:49PM -0400, Theodore Y. Ts'o wrote:
> On Fri, Jul 26, 2019 at 03:41:34PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Add an implementation of HKDF (RFC 5869) to fscrypt, for the purpose of
> > deriving additional key material from the fscrypt master keys for v2
> > encryption policies.  HKDF is a key derivation function built on top of
> > HMAC.  We choose SHA-512 for the underlying unkeyed hash, and use an
> > "hmac(sha512)" transform allocated from the crypto API.
> > 
> > We'll be using this to replace the AES-ECB based KDF currently used to
> > derive the per-file encryption keys.  While the AES-ECB based KDF is
> > believed to meet the original security requirements, it is nonstandard
> > and has problems that don't exist in modern KDFs such as HKDF:
> > 
> > 1. It's reversible.  Given a derived key and nonce, an attacker can
> >    easily compute the master key.  This is okay if the master key and
> >    derived keys are equally hard to compromise, but now we'd like to be
> >    more robust against threats such as a derived key being compromised
> >    through a timing attack, or a derived key for an in-use file being
> >    compromised after the master key has already been removed.
> > 
> > 2. It doesn't evenly distribute the entropy from the master key; each 16
> >    input bytes only affects the corresponding 16 output bytes.
> > 
> > 3. It isn't easily extensible to deriving other values or keys, such as
> >    a public hash for securely identifying the key, or per-mode keys.
> >    Per-mode keys will be immediately useful for Adiantum encryption, for
> >    which fscrypt currently uses the master key directly, introducing
> >    unnecessary usage constraints.  Per-mode keys will also be useful for
> >    hardware inline encryption, which is currently being worked on.
> > 
> > HKDF solves all the above problems.
> > 
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> 
> Unless I missed something there's nothing here which is fscrypt
> specific.  Granted that it's somewhat unlikely that someone would want
> to implement (the very bloated) IKE from IPSEC in the kernel, I wonder
> if there might be other users of HKDF, and whether this would be
> better placed in lib/ or crypto/ instead of fs/crypto?
> 

This is standard HKDF-SHA512; only the choice of parameters is fscrypt-specific.
So it could indeed use a common implementation of HKDF if one were available.

However, I don't think there are any other HKDF users in the kernel currently.
Also, while there was a patch to support HKDF via the crypto_rng API, there was
no consensus about whether this was actually the best way to add KDF support:
https://lore.kernel.org/linux-crypto/2423373.Zd5ThvQH5g@positron.chronox.de

So for now, to avoid unnecessarily blocking this patchset I think we should just
go with this implementation in fs/crypto/.  It can always be changed later, once
we decide on the best way to add KDFs to the crypto API.

[To be clear: this patch already uses "hmac(sha512)" from the crypto API.  It's
only the actual HKDF part that we're talking about here.

Also, its correctness is tested by the ciphertext verification xfstests.]

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 10/16] fscrypt: v2 encryption policy support
  2019-07-28 21:17   ` Theodore Y. Ts'o
@ 2019-07-29 20:46     ` Eric Biggers
  0 siblings, 0 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-29 20:46 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Sun, Jul 28, 2019 at 05:17:30PM -0400, Theodore Y. Ts'o wrote:
> On Fri, Jul 26, 2019 at 03:41:35PM -0700, Eric Biggers wrote:
> > @@ -319,6 +329,31 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
> >  	if (!capable(CAP_SYS_ADMIN))
> >  		goto out_wipe_secret;
> >  
> > +	if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {
> 
> This should be "== FSCRYPT_KEY_SPEC_TYPE_INDENTIFIER" instead.  That's
> because you use the identifier part of the union:
> 
> > +		/* Calculate the key identifier and return it to userspace. */
> > +		err = fscrypt_hkdf_expand(&secret.hkdf,
> > +					  HKDF_CONTEXT_KEY_IDENTIFIER,
> > +					  NULL, 0, arg.key_spec.u.identifier,
> 
> If we ever add a new key specifier type, and alternative in the union,
> this is going to come back to bite us.

Well, I did it this way because the next patch changes the code to:

	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) {
		...
	} else {
		...
	}

We already validated that it's either TYPE_DESCRIPTOR or TYPE_IDENTIFIER.

But I guess to be more clear I'll just make it handle the default case again.

	switch (arg.key_spec.type) {
	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
		...
		break;
	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
		...
		break;
	default:
		err = -EINVAL;
		break;
	}

> 
> > +	if (policy->version == FSCRYPT_POLICY_V1) {
> > +		/*
> > +		 * The original encryption policy version provided no way of
> > +		 * verifying that the correct master key was supplied, which was
> > +		 * insecure in scenarios where multiple users have access to the
> > +		 * same encrypted files (even just read-only access).
> 
> Which scenario do you have in mind?  With read-only access, Alice can
> fetch the encryption policy for a directory, and introduce a key with
> the same descriptor, but the "wrong" key, but that's only going to
> affect Alice's use of the key.  It won't affect what key is used by
> Bob, since Alice doesn't have write access to Bob's keyrings.
> 
> If what you mean is the risk when there is a single global
> filesystem-specific keyring, where Alice could introduce a "wrong" key
> identified with a specific descriptor, then sure, Alice could trick
> Bob into encrypting his data with the wrong key (one known to Alice).
> But we don't allow keys usable by V1 policies to be used in the
> filesystem-specific keyring, do we?
> 

The scenario is that Alice lists the directory with the wrong key, then Bob
lists the directory too and gets the wrong filenames.  This happens because the
inode, fscrypt_info, dentry cache, page cache, etc. are the same for everyone.
Bob's key is never looked up because the inode already has a key cached.

This also applies to regular files and symlinks.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 16/16] fscrypt: document the new ioctls and policy version
  2019-07-29  2:00   ` Theodore Y. Ts'o
@ 2019-07-29 21:36     ` Eric Biggers
  0 siblings, 0 replies; 51+ messages in thread
From: Eric Biggers @ 2019-07-29 21:36 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Sun, Jul 28, 2019 at 10:00:09PM -0400, Theodore Y. Ts'o wrote:
> On Fri, Jul 26, 2019 at 03:41:41PM -0700, Eric Biggers wrote:
> > +- The kernel cannot magically wipe copies of the master key(s) that
> > +  userspace might have as well.  Therefore, userspace must wipe all
> > +  copies of the master key(s) it makes as well.  Naturally, the same
> > +  also applies to all higher levels in the key hierarchy.  Userspace
> > +  should also follow other security precautions such as mlock()ing
> > +  memory containing keys to prevent it from being swapped out.
> 
> Normally, shouldn't userspace have wiped all copies of the master key
> after they have called ADD_KEY?  Why should they be left hanging
> around?  Waiting until REMOVE_KEY to remove other copies of the master
> key seems.... late.

Correct, normally userspace should wipe its copy of the key immediately after
adding it to the kernel.  I'll clarify that here.

> 
> > +- In general, decrypted contents and filenames in the kernel VFS
> > +  caches are freed but not wiped.  Therefore, portions thereof may be
> > +  recoverable from freed memory, even after the corresponding key(s)
> > +  were wiped.  To partially solve this, you can set
> > +  CONFIG_PAGE_POISONING=y in your kernel config and add page_poison=1
> > +  to your kernel command line.  However, this has a performance cost.
> 
> ... and even this won't help if you have swap configured....

Yes, but that's a larger issue.  Unencrypted data can be written to swap and
then be recovered from disk offline.  This has nothing to do with whether the
key is ever removed on-line or not.  So swap really could use its own mention
somewhere else, maybe in the "Offline attacks" section.

> 
> > +v1 encryption policies have some weaknesses with respect to online
> > +attacks:
> > +
> > +- There is no verification that the provided master key is correct.
> > +  Consequently, malicious users can associate the wrong key with
> > +  encrypted files, even files to which they have only read-only
> > +  access.
> 
> Yes, but they won't be able to trick other users into using that
> incorrect key.  With the old interface, it gets written into the
> user's session keyring, which won't get used by another user.  And
> with the newer interface, only root is allowed to set v1 key.
> 

As mentioned in a previous reply, they *can* trick other users into using that
incorrect key, by opening files using that incorrect key.  The incorrect key is
then cached for everyone.  (This assumes the other users have at least read
access to the file.  If it's mode 0700, this won't work.)

> > +Master keys should be pseudorandom, i.e. indistinguishable from random
> > +bytestrings of the same length.  This implies that users **must not**
> > +directly use a password as a master key, zero-pad a shorter key, or
> > +repeat a shorter key.
> 
> These paragraphs starts a bit funny, since we first say "should" in
> the first sentence, and then it's followed up by "**must not**" in the
> second sentence.  Basically, they *could* do this, but it would just
> weaken the security of the system significantly.
> 
> At the very least, we should explain the basis of the recommendation.

I think we should go with "must" instead of "should".

Basically the point of this paragraph is to explain that the API takes a real
cryptographic key of the full given length.

Otherwise the security guarantees for the algorithms the master key may be used
in (AES-128-ECB KDF, HKDF-SHA512, or Adiantum) aren't guaranteed to hold.

One can argue about how much of a problem this actually is, like how unsalted
HKDF on a key with unevenly distributed entropy is *probably* fine in practice
(and much better than the AES-128-ECB KDF).  But the security proof for unsalted
HKDF actually still assumes a pseudorandom key.  It's only randomly salted HKDF
that doesn't.

I'd strongly prefer to go with *must* for things that are necessary for the
security proofs or cryptanalysis to apply, even if they *might* still be "good
enough" in practice.

I'll try to find a better way to word this paragraph.

> 
> > +The KDF used for a particular master key differs depending on whether
> > +the key is used for v1 encryption policies or for v2 encryption
> > +policies.  Users **must not** use the same key for both v1 and v2
> > +encryption policies.
> 
> "Must not" seems a bit strong.  If they do, and a v1 per-file key and
> nonce leaks out, then the encryption key will be compromised.  So the
> strength of the key will be limited by the weaknesses of the v1
> scheme.  But it's not like using a that was originally meant for v1,
> and then using it for v2, causes any additional weakness.  Right?
> 

Probably, but we don't know for sure.  It's theoretically possible that
cryptanalysis of two cryptographic primitives A and B, where they are each given
the same key, could be much easier than attacking A or B individually.

So again, I'd prefer to go with *must not* for things where there is no theory
of cryptography that says it is okay, even if *probably* someone could get away
with doing it in practice.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation
  2019-07-29 20:29     ` Eric Biggers
@ 2019-07-29 21:42       ` James Bottomley
  0 siblings, 0 replies; 51+ messages in thread
From: James Bottomley @ 2019-07-29 21:42 UTC (permalink / raw)
  To: Eric Biggers, Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Mon, 2019-07-29 at 13:29 -0700, Eric Biggers wrote:
> On Sun, Jul 28, 2019 at 03:39:49PM -0400, Theodore Y. Ts'o wrote:
> > On Fri, Jul 26, 2019 at 03:41:34PM -0700, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@google.com>
[...]
> > > HKDF solves all the above problems.
> > > 
> > > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > 
> > Unless I missed something there's nothing here which is fscrypt
> > specific.  Granted that it's somewhat unlikely that someone would
> > want to implement (the very bloated) IKE from IPSEC in the kernel,
> > I wonder if there might be other users of HKDF, and whether this
> > would be better placed in lib/ or crypto/ instead of fs/crypto?
> 
> This is standard HKDF-SHA512; only the choice of parameters is
> fscrypt-specific. So it could indeed use a common implementation of
> HKDF if one were available.
> 
> However, I don't think there are any other HKDF users in the kernel
> currently.

Well, I'm still trying to add the TPM ones, but they're based on SP800-
108 for arbitrary keys and SP800-56A for elliptic curve ones.  These
are similar to the RFC5869 except that they do extract/expand in a
single operation.  Plus, of course, the TPM mandates we use the name
algorithm (usually sha256, which is what I hardcoded) as the hash.

Note: since you don't use the extract step either in your
implementation, effectively you're equivalent to SP800-108 as well. 
This is effectively the same reason as the TPM: we need deterministic
keys, so we've nowhere to get the salt from that would persist.

> Also, while there was a patch to support HKDF via the crypto_rng API,
> there was no consensus about whether this was actually the best way
> to add KDF support:
> https://lore.kernel.org/linux-crypto/2423373.Zd5ThvQH5g@positron.chro
> nox.de
> 
> So for now, to avoid unnecessarily blocking this patchset I think we
> should just go with this implementation in fs/crypto/.  It can always
> be changed later, once we decide on the best way to add KDFs to the
> crypto API.
> 
> [To be clear: this patch already uses "hmac(sha512)" from the crypto
> API.  It's only the actual HKDF part that we're talking about here.

Right, once you have the hmac + hash available, the rest is easy, so
this is what we have for the TPM KDFa:

static void KDFa(u8 *key, int keylen, const char *label, u8 *u,
		 u8 *v, int bytes, u8 *out)
{
	u32 counter;
	const __be32 bits = cpu_to_be32(bytes * 8);

	for (counter = 1; bytes > 0; bytes -= SHA256_DIGEST_SIZE, counter++,
		     out += SHA256_DIGEST_SIZE) {
		SHASH_DESC_ON_STACK(desc, sha256_hash);
		__be32 c = cpu_to_be32(counter);

		hmac_init(desc, key, keylen);
		crypto_shash_update(desc, (u8 *)&c, sizeof(c));
		crypto_shash_update(desc, label, strlen(label)+1);
		crypto_shash_update(desc, u, SHA256_DIGEST_SIZE);
		crypto_shash_update(desc, v, SHA256_DIGEST_SIZE);
		crypto_shash_update(desc, (u8 *)&bits, sizeof(bits));
		hmac_final(desc, key, keylen, out);
	}
}

I honestly think these things are so simplistic with the correct hmac
that it would make it more confusing to try to produce a general KDF
than it would simply to hard code them where we need them.

James



^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 14/16] f2fs: wire up new fscrypt ioctls
  2019-07-26 22:41 ` [PATCH v7 14/16] f2fs: " Eric Biggers
@ 2019-07-30  0:36   ` Jaegeuk Kim
  2019-08-02  8:10   ` Chao Yu
  1 sibling, 0 replies; 51+ messages in thread
From: Jaegeuk Kim @ 2019-07-30  0:36 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On 07/26, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Wire up the new ioctls for adding and removing fscrypt keys to/from the
> filesystem, and the new ioctl for retrieving v2 encryption policies.
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY also required making f2fs_drop_inode() call
> fscrypt_drop_inode().
> 
> For more details see Documentation/filesystems/fscrypt.rst and the
> fscrypt patches that added the implementation of these ioctls.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>

Thanks,

> ---
>  fs/f2fs/file.c  | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  fs/f2fs/super.c |  2 ++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index f8d46df8fa9ee..d81dda290b829 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -2184,6 +2184,40 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
>  	return err;
>  }
>  
> +static int f2fs_ioc_get_encryption_policy_ex(struct file *filp,
> +					     unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg);
> +}
> +
> +static int f2fs_ioc_add_encryption_key(struct file *filp, unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_add_key(filp, (void __user *)arg);
> +}
> +
> +static int f2fs_ioc_remove_encryption_key(struct file *filp, unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_remove_key(filp, (const void __user *)arg);
> +}
> +
> +static int f2fs_ioc_get_encryption_key_status(struct file *filp,
> +					      unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
> +}
> +
>  static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
>  {
>  	struct inode *inode = file_inode(filp);
> @@ -3109,6 +3143,14 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		return f2fs_ioc_get_encryption_policy(filp, arg);
>  	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
>  		return f2fs_ioc_get_encryption_pwsalt(filp, arg);
> +	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
> +		return f2fs_ioc_get_encryption_policy_ex(filp, arg);
> +	case FS_IOC_ADD_ENCRYPTION_KEY:
> +		return f2fs_ioc_add_encryption_key(filp, arg);
> +	case FS_IOC_REMOVE_ENCRYPTION_KEY:
> +		return f2fs_ioc_remove_encryption_key(filp, arg);
> +	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
> +		return f2fs_ioc_get_encryption_key_status(filp, arg);
>  	case F2FS_IOC_GARBAGE_COLLECT:
>  		return f2fs_ioc_gc(filp, arg);
>  	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
> @@ -3236,6 +3278,10 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	case F2FS_IOC_SET_ENCRYPTION_POLICY:
>  	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
>  	case F2FS_IOC_GET_ENCRYPTION_POLICY:
> +	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
> +	case FS_IOC_ADD_ENCRYPTION_KEY:
> +	case FS_IOC_REMOVE_ENCRYPTION_KEY:
> +	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
>  	case F2FS_IOC_GARBAGE_COLLECT:
>  	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
>  	case F2FS_IOC_WRITE_CHECKPOINT:
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 6de6cda440315..f5fae8d511a20 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -913,6 +913,8 @@ static int f2fs_drop_inode(struct inode *inode)
>  		return 0;
>  	}
>  	ret = generic_drop_inode(inode);
> +	if (!ret)
> +		ret = fscrypt_drop_inode(inode);
>  	trace_f2fs_drop_inode(inode, ret);
>  	return ret;
>  }
> -- 
> 2.22.0

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 15/16] ubifs: wire up new fscrypt ioctls
  2019-07-26 22:41 ` [PATCH v7 15/16] ubifs: " Eric Biggers
@ 2019-07-30  0:39   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-30  0:39 UTC (permalink / raw)
  To: Eric Biggers
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Jul 26, 2019 at 03:41:40PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Wire up the new ioctls for adding and removing fscrypt keys to/from the
> filesystem, and the new ioctl for retrieving v2 encryption policies.
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY also required making UBIFS use
> fscrypt_drop_inode().
> 
> For more details see Documentation/filesystems/fscrypt.rst and the
> fscrypt patches that added the implementation of these ioctls.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

					- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-07-29 19:58     ` Eric Biggers
@ 2019-07-31 18:38       ` Eric Biggers
  2019-07-31 23:38         ` Theodore Y. Ts'o
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-07-31 18:38 UTC (permalink / raw)
  To: Theodore Y. Ts'o, linux-fscrypt, linux-fsdevel, linux-ext4,
	linux-f2fs-devel, linux-mtd, linux-api, linux-crypto, keyrings,
	Paul Crowley, Satya Tangirala

On Mon, Jul 29, 2019 at 12:58:28PM -0700, Eric Biggers wrote:
> On Sun, Jul 28, 2019 at 03:24:17PM -0400, Theodore Y. Ts'o wrote:
> > > +
> > > +/*
> > > + * Try to remove an fscrypt master encryption key.  If other users have also
> > > + * added the key, we'll remove the current user's usage of the key, then return
> > > + * -EUSERS.  Otherwise we'll continue on and try to actually remove the key.
> > 
> > Nit: this should be moved to patch #11
> > 
> > Also, perror(EUSERS) will display "Too many users" which is going to
> > be confusing.  I understand why you chose this; we would like to
> > distinguish between there are still inodes using this key, and there
> > are other users using this key.
> > 
> > Do we really need to return EUSERS in this case?  It's actually not an
> > *error* that other users are using the key.  After all, the unlink(2)
> > system call doesn't return an advisory error when you delete a file
> > which has other hard links.  And an application which does care about
> > this detail can always call FS_IOC_ENCRYPTION_KEY_STATUS() and check
> > user_count.
> > 
> 
> Returning 0 when the key wasn't fully removed might also be confusing.  But I
> guess you're right that returning an error doesn't match how syscalls usually
> work.  It did remove the current user's usage of the key, after all, rather than
> completely fail.  And as you point out, if someone cares about other users
> having added the key, they can use FS_IOC_GET_ENCRYPTION_KEY_STATUS.
> 
> So I guess I'll change it to 0.
> 

So after making this change and thinking about it some more, I'm not sure it's
actually an improvement.

The normal use case for this ioctl is to "lock" some encrypted directory(s).  If
it returns 0 and doesn't lock the directory(s), that's unexpected.

This is perhaps different from what users expect from unlink().  It's well known
that unlink() just deletes the filename, not the file itself if it's still open
or has other links.  And unlink() by itself isn't meant for use cases where the
file absolutely must be securely erased.  But FS_IOC_REMOVE_ENCRYPTION_KEY
really is meant primarily for that sort of thing.

To give a concrete example: my patch for the userspace tool
https://github.com/google/fscrypt adds a command 'fscrypt lock' which locks an
encrypted directory.  If, say, someone runs 'fscrypt unlock' as uid 0 and then
'fscrypt lock' as uid 1000, then FS_IOC_REMOVE_ENCRYPTION_KEY can't actually
remove the key.  I need to make the tool show a proper error message in this
case.  To do so, it would help to get a unique error code (e.g. EUSERS) from
FS_IOC_REMOVE_ENCRYPTION_KEY, rather than get the ambiguous error code ENOKEY
and have to call FS_IOC_GET_ENCRYPTION_KEY_STATUS to get the real status.

Also, we already have the EBUSY case.  This means that the ioctl removed the
master key secret itself; however, some files were still in-use, so the key
remains in the "incompletely removed" state.  If we were actually going for
unlink() semantics, then for consistency this case really ought to return 0 and
unlink the key object, and people who care about in-use files would need to use
FS_IOC_GET_ENCRYPTION_KEY_STATUS.  But most people *will* care about this, and
may even want to retry the ioctl later, which isn't something you can do with
pure unlink() semantics.

So I'm leaning towards keeping the EUSERS and EBUSY errors.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-07-31 18:38       ` Eric Biggers
@ 2019-07-31 23:38         ` Theodore Y. Ts'o
  2019-08-01  1:11           ` [f2fs-dev] " Eric Biggers
  0 siblings, 1 reply; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-07-31 23:38 UTC (permalink / raw)
  To: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Wed, Jul 31, 2019 at 11:38:02AM -0700, Eric Biggers wrote:
> 
> This is perhaps different from what users expect from unlink().  It's well known
> that unlink() just deletes the filename, not the file itself if it's still open
> or has other links.  And unlink() by itself isn't meant for use cases where the
> file absolutely must be securely erased.  But FS_IOC_REMOVE_ENCRYPTION_KEY
> really is meant primarily for that sort of thing.

Seems to me that part of the confusion is FS_IOC_REMOVE_ENCRYPTION_KEY
does two things.  One is "remove the user's handle on the key".  The
other is "purge all keys" (which requires root).  So it does two
different things with one ioctl.

> To give a concrete example: my patch for the userspace tool
> https://github.com/google/fscrypt adds a command 'fscrypt lock' which locks an
> encrypted directory.  If, say, someone runs 'fscrypt unlock' as uid 0 and then
> 'fscrypt lock' as uid 1000, then FS_IOC_REMOVE_ENCRYPTION_KEY can't actually
> remove the key.  I need to make the tool show a proper error message in this
> case.  To do so, it would help to get a unique error code (e.g. EUSERS) from
> FS_IOC_REMOVE_ENCRYPTION_KEY, rather than get the ambiguous error code ENOKEY
> and have to call FS_IOC_GET_ENCRYPTION_KEY_STATUS to get the real status.

What about having "fscrypt lock" call FS_IOC_GET_ENCRYPTION_KEY_STATUS
and print a warning message saying, "we can't lock it because N other
users who have registered a key".  I'd argue fscrypt should do this
regardless of whether or not FS_IOC_REMOVE_ENCRYPTION_KEY returns
EUSERS or not.

> Also, we already have the EBUSY case.  This means that the ioctl removed the
> master key secret itself; however, some files were still in-use, so the key
> remains in the "incompletely removed" state.  If we were actually going for
> unlink() semantics, then for consistency this case really ought to return 0 and
> unlink the key object, and people who care about in-use files would need to use
> FS_IOC_GET_ENCRYPTION_KEY_STATUS.  But most people *will* care about this, and
> may even want to retry the ioctl later, which isn't something youh can do with
> pure unlink() semantics.

It seems to me that the EBUSY and EUSERS errors should be status bits
which gets returned to the user in a bitfield --- and if the key has
been removed, or the user's claim on the key's existence has been
removed, the ioctl returns success.

That way we don't have to deal with the semantic disconnect where some
errors don't actually change system state, and other errors that *do*
change system state (as in, the key gets removed, or the user's claim
on the key gets removed), but still returns than error.

We could also add a flag which indicates where if there are files that
are still busy, or there are other users keeping a key in use, the
ioctl fails hard and returns an error.  At least that way we keep
consistency where an error means, "nothing has changed".

	    	     	   	  	   - Ted

P.S.  BTW, one of the comments which I didn't make was the
documentation didn't adequately explain which error codes means,
"success but with a caveat", and which errors means, "we failed and
didn't do anything".  But since I was arguing for changing the
behavior, I decided not to complain about the documentation.


^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [f2fs-dev] [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-07-31 23:38         ` Theodore Y. Ts'o
@ 2019-08-01  1:11           ` " Eric Biggers
  2019-08-01  5:31             ` Theodore Y. Ts'o
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-08-01  1:11 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Wed, Jul 31, 2019 at 07:38:43PM -0400, Theodore Y. Ts'o wrote:
> On Wed, Jul 31, 2019 at 11:38:02AM -0700, Eric Biggers wrote:
> > 
> > This is perhaps different from what users expect from unlink().  It's well known
> > that unlink() just deletes the filename, not the file itself if it's still open
> > or has other links.  And unlink() by itself isn't meant for use cases where the
> > file absolutely must be securely erased.  But FS_IOC_REMOVE_ENCRYPTION_KEY
> > really is meant primarily for that sort of thing.
> 
> Seems to me that part of the confusion is FS_IOC_REMOVE_ENCRYPTION_KEY
> does two things.  One is "remove the user's handle on the key".  The
> other is "purge all keys" (which requires root).  So it does two
> different things with one ioctl.
> 

Well, it's either

1a. Remove the user's handle.
	OR 
1b. Remove all users' handles.  (FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)

Then

2. If no handles remain, try to evict all inodes that use the key.

By "purge all keys" do you mean step (2)?  Note that it doesn't require root by
itself; root is only required to remove other users' handles (1b).

It could be argued that (2) should be a separate ioctl, so we'd have UNLINK_KEY
then LOCK_KEY.  But is there a real use case for this split?  I.e. would anyone
ever want to UNLINK_KEY without also LOCK_KEY?  Is that really something we
want/need to support?  I'd really like the API to be as straightforward as
possible for the normal use case of locking a directory, and not require some
series of multiple ioctl's, which would be more difficult to use correctly.

> > To give a concrete example: my patch for the userspace tool
> > https://github.com/google/fscrypt adds a command 'fscrypt lock' which locks an
> > encrypted directory.  If, say, someone runs 'fscrypt unlock' as uid 0 and then
> > 'fscrypt lock' as uid 1000, then FS_IOC_REMOVE_ENCRYPTION_KEY can't actually
> > remove the key.  I need to make the tool show a proper error message in this
> > case.  To do so, it would help to get a unique error code (e.g. EUSERS) from
> > FS_IOC_REMOVE_ENCRYPTION_KEY, rather than get the ambiguous error code ENOKEY
> > and have to call FS_IOC_GET_ENCRYPTION_KEY_STATUS to get the real status.
> 
> What about having "fscrypt lock" call FS_IOC_GET_ENCRYPTION_KEY_STATUS
> and print a warning message saying, "we can't lock it because N other
> users who have registered a key".  I'd argue fscrypt should do this
> regardless of whether or not FS_IOC_REMOVE_ENCRYPTION_KEY returns
> EUSERS or not.

Shouldn't "fscrypt lock" still remove the user's handle, as opposed to refuse to
do anything, though?  So it would still need to call
FS_IOC_REMOVE_ENCRYPTION_KEY, and could get the status from it rather than also
needing to call FS_IOC_GET_ENCRYPTION_KEY_STATUS.

Though, FS_IOC_GET_ENCRYPTION_KEY_STATUS would be needed if we wanted to show
the specific count of other users.

> 
> > Also, we already have the EBUSY case.  This means that the ioctl removed the
> > master key secret itself; however, some files were still in-use, so the key
> > remains in the "incompletely removed" state.  If we were actually going for
> > unlink() semantics, then for consistency this case really ought to return 0 and
> > unlink the key object, and people who care about in-use files would need to use
> > FS_IOC_GET_ENCRYPTION_KEY_STATUS.  But most people *will* care about this, and
> > may even want to retry the ioctl later, which isn't something youh can do with
> > pure unlink() semantics.
> 
> It seems to me that the EBUSY and EUSERS errors should be status bits
> which gets returned to the user in a bitfield --- and if the key has
> been removed, or the user's claim on the key's existence has been
> removed, the ioctl returns success.
> 
> That way we don't have to deal with the semantic disconnect where some
> errors don't actually change system state, and other errors that *do*
> change system state (as in, the key gets removed, or the user's claim
> on the key gets removed), but still returns than error.
> 
> We could also add a flag which indicates where if there are files that
> are still busy, or there are other users keeping a key in use, the
> ioctl fails hard and returns an error.  At least that way we keep
> consistency where an error means, "nothing has changed".
> 
> 	    	     	   	  	   - Ted

Do you mean use a positive return value, or do you mean add an output field to
the struct passed to the ioctl?

The latter might be more error-prone, since it invites bugs where a directory
silently fails to be locked, because the second field was not checked.

Either way note that it doesn't really need to be a bitfield, since you can't
have both statuses at the same time.  I.e. if there are still other users, we
couldn't have even gotten to checking for in-use files.

> 
> P.S.  BTW, one of the comments which I didn't make was the
> documentation didn't adequately explain which error codes means,
> "success but with a caveat", and which errors means, "we failed and
> didn't do anything".  But since I was arguing for changing the
> behavior, I decided not to complain about the documentation.
> 

Yes, in any case the FS_IOC_REMOVE_ENCRYPTION_KEY documentation needs
improvement.  I have some updates pending for it.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [f2fs-dev] [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-08-01  1:11           ` [f2fs-dev] " Eric Biggers
@ 2019-08-01  5:31             ` Theodore Y. Ts'o
  2019-08-01 18:35               ` Eric Biggers
  2019-08-01 22:04               ` Eric Biggers
  0 siblings, 2 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-08-01  5:31 UTC (permalink / raw)
  To: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Wed, Jul 31, 2019 at 06:11:40PM -0700, Eric Biggers wrote:
> 
> Well, it's either
> 
> 1a. Remove the user's handle.
> 	OR 
> 1b. Remove all users' handles.  (FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)
> 
> Then
> 
> 2. If no handles remain, try to evict all inodes that use the key.
> 
> By "purge all keys" do you mean step (2)?  Note that it doesn't require root by
> itself; root is only required to remove other users' handles (1b).

No, I was talking about 1b.  I'd argue that 1a and 1b should be
different ioctl.  1b requires root, and 1a doesn't.

And 1a should just mean, "I don't need to use the encrypted files any
more".  In the PAM passphrase case, when you are just logging out, 1a
is what's needed, and success is just fine.  pam_session won't *care*
whether or not there are other users keeping the key in use.

The problem with "fscrypt lock" is that the non-privileged user sort
of wants to do REMOVE_FLAG_KEY_FLAG_FOR_ALL_USERS, but they doesn't
have the privileges to do it, and they are hoping that removing their
own key removes it the key from the system.  That to me seems to be
the fundamental disconnect.  The "fscrypt unlock" and "fscrypt lock"
commands comes from the v1 key management, and requires root.  It's
the translation to unprivileged mode where "fscrypt lock" seems to
have problems.

> > What about having "fscrypt lock" call FS_IOC_GET_ENCRYPTION_KEY_STATUS
> > and print a warning message saying, "we can't lock it because N other
> > users who have registered a key".  I'd argue fscrypt should do this
> > regardless of whether or not FS_IOC_REMOVE_ENCRYPTION_KEY returns
> > EUSERS or not.
> 
> Shouldn't "fscrypt lock" still remove the user's handle, as opposed to refuse to
> do anything, though?  So it would still need to callh
> FS_IOC_REMOVE_ENCRYPTION_KEY, and could get the status from it rather than also
> needing to call FS_IOC_GET_ENCRYPTION_KEY_STATUS.
> 
> Though, FS_IOC_GET_ENCRYPTION_KEY_STATUS would be needed if we wanted to show
> the specific count of other users.
 
So my perspective is that the ioctl's should have very clean
semantics, and errors should be consistent with how the Unix system
calls and error reporting.

If we need to make "fscrypt lock" and "fscrypt unlock" have semantics
that are more consistent with previous user interface choices, then
fscrypt can use FS_IOC_GET_ENCRYPTION_KEY_STATUS to print the warning
before it calls FS_IOC_REMOVE_ENCRYPTION_KEY --- with "fscrypt purge_keys"
calling something like FS_IOC_REMOVE_ALL_USER_ENCRYPTION_KEYS.

> > It seems to me that the EBUSY and EUSERS errors should be status bits
> > which gets returned to the user in a bitfield --- and if the key has
> > been removed, or the user's claim on the key's existence has been
> > removed, the ioctl returns success.
> > 
> > That way we don't have to deal with the semantic disconnect where some
> > errors don't actually change system state, and other errors that *do*
> > change system state (as in, the key gets removed, or the user's claim
> > on the key gets removed), but still returns than error.
> > 
> 
> Do you mean use a positive return value, or do you mean add an output field to
> the struct passed to the ioctl?

I meant adding an output field.  I see EBUSY and EUSERS as status bits
which *some* use cases might find useful.  Other use cases, such as in
the pam_keys session logout code, we won't care at *all* about those
status reporting (or error codes).  So if EBUSY and EUSERS are
returned as errors, then it adds to complexity of those programs
whichd don't care.  (And even for those that do, it's still a bit more
complex since they has to distinguish between EBUSY, EUSERS, or other
errors --- in fact, *all* programs which use
FS_IOC_REMOVE_ENCRYPTION_KEY will *have* to check for EBUSY and
ESUSERS whether they care or not.)

> Either way note that it doesn't really need to be a bitfield, since you can't
> have both statuses at the same time.  I.e. if there are still other users, we
> couldn't have even gotten to checking for in-use files.

That's actually an implementation detail, though, right?  In theory,
we could check to see if there are any in-use files, independently of
whether there are any users or not.

					- Ted

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-08-01  5:31             ` Theodore Y. Ts'o
@ 2019-08-01 18:35               ` Eric Biggers
  2019-08-01 18:46                 ` Eric Biggers
  2019-08-01 22:04               ` Eric Biggers
  1 sibling, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-08-01 18:35 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Thu, Aug 01, 2019 at 01:31:08AM -0400, Theodore Y. Ts'o wrote:
> On Wed, Jul 31, 2019 at 06:11:40PM -0700, Eric Biggers wrote:
> > 
> > Well, it's either
> > 
> > 1a. Remove the user's handle.
> > 	OR 
> > 1b. Remove all users' handles.  (FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)
> > 
> > Then
> > 
> > 2. If no handles remain, try to evict all inodes that use the key.
> > 
> > By "purge all keys" do you mean step (2)?  Note that it doesn't require root by
> > itself; root is only required to remove other users' handles (1b).
> 
> No, I was talking about 1b.  I'd argue that 1a and 1b should be
> different ioctl.  1b requires root, and 1a doesn't.
> 
> And 1a should just mean, "I don't need to use the encrypted files any
> more".  In the PAM passphrase case, when you are just logging out, 1a
> is what's needed, and success is just fine.  pam_session won't *care*
> whether or not there are other users keeping the key in use.

But in both cases, we still need to do the same things if the last user is
removed: remove the master key secret, try to evict the inodes, and (if all
inodes could be evicted) unlink the key object from the filesystem-level
keyring.  So the ioctls would be nearly the same; it's just the
"remove key user(s)" step that would be different.

So in my view, these are variants of the same action, which is why it's a flag.
Likewise, there aren't separate ioctls for v1 and v2 policy keys, since
adding/removing those are variants on the same actions, and it allows the ioctls
to be extended to v3 in the future if it ever becomes necessary.

Now, I don't have *that* much of an issue with making it an separate ioctl
FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS.  We can make them call the same function
internally, with a bool argument to distinguish the two ioctls.  It just seems
like an unnecessary complication.

> 
> The problem with "fscrypt lock" is that the non-privileged user sort
> of wants to do REMOVE_FLAG_KEY_FLAG_FOR_ALL_USERS, but they doesn't
> have the privileges to do it, and they are hoping that removing their
> own key removes it the key from the system.  That to me seems to be
> the fundamental disconnect.  The "fscrypt unlock" and "fscrypt lock"
> commands comes from the v1 key management, and requires root.  It's
> the translation to unprivileged mode where "fscrypt lock" seems to
> have problems.

"fscrypt lock" actually doesn't exist yet; it's a missing feature.  My patch to
the fscrypt tool adds it.  So we get to decide on the semantics.  We don't want
to require root, though; so for v2 policy keys, the real semantics have to be
that "fscrypt lock" registers the key for the user, and "fscrypt unlock"
unregisters it for the user.

One could argue that because of this they should be named "fscrypt register_key"
and "fscrypt unregister_key".  However, in the vast majority of cases these will
be run as a single user, with a key that is not shared with any other user.

[In fact, I recently changed the fscrypt tool to automatically set mode 0700 on
new encrypted directories, since most people found it surprising that their
unlocked encrypted files weren't private to them by default.  So if someone
wants to share their encrypted directory with another user, they now also need
to explicitly chmod it, unless the root user is involved.]

So presenting the commands as locking/unlocking a directory is a useful
simplication that makes them much easier to use, IMO.  People shouldn't need to
understand multi-user key registration in order to unlock/lock their personal
encrypted directories.

And if "fscrypt lock" does nevertheless hit the case where other users remain, I
think it would be most user-friendly to print a warning like this:

	Directory not fully locked; other users have added the key.
 	Run 'sudo fscrypt lock --all-users DIR' if you want to force-lock the directory.

We *could* make the --all-users option a separate subcommand like
"fscrypt force_lock", but again to me it seems like a variant of the same thing.

> > > It seems to me that the EBUSY and EUSERS errors should be status bits
> > > which gets returned to the user in a bitfield --- and if the key has
> > > been removed, or the user's claim on the key's existence has been
> > > removed, the ioctl returns success.
> > > 
> > > That way we don't have to deal with the semantic disconnect where some
> > > errors don't actually change system state, and other errors that *do*
> > > change system state (as in, the key gets removed, or the user's claim
> > > on the key gets removed), but still returns than error.
> > > 
> > 
> > Do you mean use a positive return value, or do you mean add an output field to
> > the struct passed to the ioctl?
> 
> I meant adding an output field.  I see EBUSY and EUSERS as status bits
> which *some* use cases might find useful.  Other use cases, such as in
> the pam_keys session logout code, we won't care at *all* about those
> status reporting (or error codes).  So if EBUSY and EUSERS are
> returned as errors, then it adds to complexity of those programs
> whichd don't care.  (And even for those that do, it's still a bit more
> complex since they has to distinguish between EBUSY, EUSERS, or other
> errors --- in fact, *all* programs which use
> FS_IOC_REMOVE_ENCRYPTION_KEY will *have* to check for EBUSY and
> ESUSERS whether they care or not.)
> 

I see it a little differently: I'd prefer for the API to be "secure by default",
i.e. it tries hard to really remove the key, and it returns an error if it
couldn't really be removed (but still did as much as possible).  And if the
caller is fine with some case(s) where the key wasn't truly removed, then they
can just explicitly handle those case(s).

You're suggesting the opposite: the ioctl will return 0 if the key was
unregistered for current user only, or if some files are still in use; and if
someone cares whether the key was *really* removed, then they'd need to check
the additional status bits.

That's easier to misuse in the more important ways, in my view.  Now, it's not a
huge deal, as the API provides the same information either way, and regardless
of which one we choose, I'll make sure it's used correctly in fscrypt, Android,
Chrome OS, etc...

> > Either way note that it doesn't really need to be a bitfield, since you can't
> > have both statuses at the same time.  I.e. if there are still other users, we
> > couldn't have even gotten to checking for in-use files.
> 
> That's actually an implementation detail, though, right?  In theory,
> we could check to see if there are any in-use files, independently of
> whether there are any users or not.
> 

Yes, but wouldn't people assume that if the bitfield is provided, that all the
bits are actually filled in?  Remember that to determine the "in-use files" bit
we have to actually go through the inode list and try to evict all the inodes.
That's not really something we should be doing before the last user is removed.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-08-01 18:35               ` Eric Biggers
@ 2019-08-01 18:46                 ` Eric Biggers
  0 siblings, 0 replies; 51+ messages in thread
From: Eric Biggers @ 2019-08-01 18:46 UTC (permalink / raw)
  To: Theodore Y. Ts'o, linux-fscrypt, linux-fsdevel, linux-ext4,
	linux-f2fs-devel, linux-mtd, linux-api, linux-crypto, keyrings,
	Paul Crowley, Satya Tangirala

On Thu, Aug 01, 2019 at 11:35:56AM -0700, Eric Biggers wrote:
> 
> "fscrypt lock" actually doesn't exist yet; it's a missing feature.  My patch to
> the fscrypt tool adds it.  So we get to decide on the semantics.  We don't want
> to require root, though; so for v2 policy keys, the real semantics have to be
> that "fscrypt lock" registers the key for the user, and "fscrypt unlock"
> unregisters it for the user.
> 

I meant the other way around, of course: "fscrypt unlock" registers the key for
the user, and "fscrypt lock" unregisters it for the user.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-08-01  5:31             ` Theodore Y. Ts'o
  2019-08-01 18:35               ` Eric Biggers
@ 2019-08-01 22:04               ` Eric Biggers
  2019-08-02  4:38                 ` Eric Biggers
  1 sibling, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-08-01 22:04 UTC (permalink / raw)
  To: Theodore Y. Ts'o
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Thu, Aug 01, 2019 at 01:31:08AM -0400, Theodore Y. Ts'o wrote:
> On Wed, Jul 31, 2019 at 06:11:40PM -0700, Eric Biggers wrote:
> > 
> > Well, it's either
> > 
> > 1a. Remove the user's handle.
> > 	OR 
> > 1b. Remove all users' handles.  (FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)
> > 
> > Then
> > 
> > 2. If no handles remain, try to evict all inodes that use the key.
> > 
> > By "purge all keys" do you mean step (2)?  Note that it doesn't require root by
> > itself; root is only required to remove other users' handles (1b).
> 
> No, I was talking about 1b.  I'd argue that 1a and 1b should be
> different ioctl.  1b requires root, and 1a doesn't.
> 
[...]
> > 
> > Do you mean use a positive return value, or do you mean add an output field to
> > the struct passed to the ioctl?
> 
> I meant adding an output field.  I see EBUSY and EUSERS as status bits
> which *some* use cases might find useful.

Ted, would you be happy with the following API?

Removing keys
-------------

Two ioctls are available for removing a key that was added by
FS_IOC_ADD_ENCRYPTION_KEY: FS_IOC_REMOVE_ENCRYPTION_KEY and
FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS.  They differ only in cases
where v2 policy keys are added or removed by non-root users.

These ioctls don't work on keys that were added via the legacy
process-subscribed keyrings mechanism.

Before using these ioctls, read the `Kernel memory compromise`_
section for a discussion of the security goals and limitations of
these ioctls.

FS_IOC_REMOVE_ENCRYPTION_KEY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The FS_IOC_REMOVE_ENCRYPTION_KEY ioctl removes a claim to an fscrypt
master encryption key from the filesystem, and possibly removes the
key itself.  It can be executed on any file or directory on the target
filesystem, but using the filesystem's root directory is recommended.
It takes in a pointer to a :c:type:`struct fscrypt_remove_key_arg`,
defined as follows::

    struct fscrypt_remove_key_arg {
            struct fscrypt_key_specifier key_spec;
    #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS     0x00000001
    #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY      0x00000002
            __u32 removal_status_flags;     /* output */
            __u32 __reserved[5];
    };

This structure must be zeroed, then initialized as follows:

- The key to remove is specified by ``key_spec``:

    - To remove a key used by v1 encryption policies, set
      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
      in ``key_spec.u.descriptor``.  To remove this type of key, the
      calling process must have the CAP_SYS_ADMIN capability in the
      initial user namespace.

    - To remove a key used by v2 encryption policies, set
      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
      in ``key_spec.u.identifier``.  To remove this type of key, no
      privileges are needed.  However, users can only remove keys that
      they added themselves, subject to privileged override with
      FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS.

For v2 policy keys, this ioctl is usable by non-root users.  However,
to make this possible, it actually just removes the current user's
claim to the key, undoing a single call to FS_IOC_ADD_ENCRYPTION_KEY.
Only after all claims are removed is the key really removed.

For example, if FS_IOC_ADD_ENCRYPTION_KEY was called with uid 1000,
then the key will be "claimed" by uid 1000, and
FS_IOC_REMOVE_ENCRYPTION_KEY will only succeed as uid 1000.  Or, if
both uids 1000 and 2000 added the key, then for each uid
FS_IOC_REMOVE_ENCRYPTION_KEY will only remove their own claim.  Only
once *both* are removed is the key really removed.  (Think of it like
unlinking a file that may have hard links.)

If FS_IOC_REMOVE_ENCRYPTION_KEY really removes the key, it will also
try to "lock" all files that had been unlocked with the key.  It won't
lock files that are still in-use.  If necessary, the ioctl can be
executed again later to retry locking any remaining files.

FS_IOC_REMOVE_ENCRYPTION_KEY returns 0 if either the key was removed
(but may still have files remaining to be locked), the user's claim to
the key was removed, or the key was already removed but had files
remaining to be the locked so the ioctl retried locking them.  In any
of these cases, ``removal_status_flags`` is filled in with the
following informational status flags:

- ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS``: set if only the
  user's claim to the key was removed, not the key itself
- ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY``: set if some file(s)
  are still in-use.  Not guaranteed to be set in the case where only
  the user's claim to the key was removed.

FS_IOC_REMOVE_ENCRYPTION_KEY can fail with the following errors:

- ``EACCES``: The FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR key specifier type
  was specified, but the caller does not have the CAP_SYS_ADMIN
  capability in the initial user namespace
- ``EINVAL``: invalid flags or key specifier type, or reserved bits
  were set
- ``ENOKEY``: the key object was not found at all, i.e. it was never
  added in the first place or was already fully removed including all
  files locked; or, the user does not have a claim to the key.
- ``ENOTTY``: this type of filesystem does not implement encryption
- ``EOPNOTSUPP``: the kernel was not configured with encryption
  support for this filesystem, or the filesystem superblock has not
  had encryption enabled on it

FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS is exactly the same as
FS_IOC_REMOVE_ENCRYPTION_KEY, except that for v2 policy keys, the
ALL_USERS version of the ioctl will remove all users' claims to the
key, not just the current user's.  I.e., the key itself will always be
removed, no matter how many users have added it.  This difference is
only meaningful if non-root users are adding and removing keys.

Because of this, FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS also requires
"root", namely the CAP_SYS_ADMIN capability in the initial user
namespace.  Otherwise it will fail with ``EACCES``.

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-08-01 22:04               ` Eric Biggers
@ 2019-08-02  4:38                 ` Eric Biggers
  2019-08-12 14:16                   ` Theodore Y. Ts'o
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-08-02  4:38 UTC (permalink / raw)
  To: Theodore Y. Ts'o, linux-fscrypt, linux-fsdevel, linux-ext4,
	linux-f2fs-devel, linux-mtd, linux-api, linux-crypto, keyrings,
	Paul Crowley, Satya Tangirala

On Thu, Aug 01, 2019 at 03:04:34PM -0700, Eric Biggers wrote:
> On Thu, Aug 01, 2019 at 01:31:08AM -0400, Theodore Y. Ts'o wrote:
> > On Wed, Jul 31, 2019 at 06:11:40PM -0700, Eric Biggers wrote:
> > > 
> > > Well, it's either
> > > 
> > > 1a. Remove the user's handle.
> > > 	OR 
> > > 1b. Remove all users' handles.  (FSCRYPT_REMOVE_KEY_FLAG_ALL_USERS)
> > > 
> > > Then
> > > 
> > > 2. If no handles remain, try to evict all inodes that use the key.
> > > 
> > > By "purge all keys" do you mean step (2)?  Note that it doesn't require root by
> > > itself; root is only required to remove other users' handles (1b).
> > 
> > No, I was talking about 1b.  I'd argue that 1a and 1b should be
> > different ioctl.  1b requires root, and 1a doesn't.
> > 
> [...]
> > > 
> > > Do you mean use a positive return value, or do you mean add an output field to
> > > the struct passed to the ioctl?
> > 
> > I meant adding an output field.  I see EBUSY and EUSERS as status bits
> > which *some* use cases might find useful.
> 
> Ted, would you be happy with the following API?
> 

Here's a slightly updated version (I missed removing some stale text):

Removing keys
-------------

Two ioctls are available for removing a key that was added by
`FS_IOC_ADD_ENCRYPTION_KEY`_:

- `FS_IOC_REMOVE_ENCRYPTION_KEY`_
- `FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS`_

These two ioctls differ only in cases where v2 policy keys are added
or removed by non-root users.

These ioctls don't work on keys that were added via the legacy
process-subscribed keyrings mechanism.

Before using these ioctls, read the `Kernel memory compromise`_
section for a discussion of the security goals and limitations of
these ioctls.

FS_IOC_REMOVE_ENCRYPTION_KEY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The FS_IOC_REMOVE_ENCRYPTION_KEY ioctl removes a claim to a master
encryption key from the filesystem, and possibly removes the key
itself.  It can be executed on any file or directory on the target
filesystem, but using the filesystem's root directory is recommended.
It takes in a pointer to a :c:type:`struct fscrypt_remove_key_arg`,
defined as follows::

    struct fscrypt_remove_key_arg {
            struct fscrypt_key_specifier key_spec;
    #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY      0x00000001
    #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS     0x00000002
            __u32 removal_status_flags;     /* output */
            __u32 __reserved[5];
    };

This structure must be zeroed, then initialized as follows:

- The key to remove is specified by ``key_spec``:

    - To remove a key used by v1 encryption policies, set
      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
      in ``key_spec.u.descriptor``.  To remove this type of key, the
      calling process must have the CAP_SYS_ADMIN capability in the
      initial user namespace.

    - To remove a key used by v2 encryption policies, set
      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
      in ``key_spec.u.identifier``.

For v2 policy keys, this ioctl is usable by non-root users.  However,
to make this possible, it actually just removes the current user's
claim to the key, undoing a single call to FS_IOC_ADD_ENCRYPTION_KEY.
Only after all claims are removed is the key really removed.

For example, if FS_IOC_ADD_ENCRYPTION_KEY was called with uid 1000,
then the key will be "claimed" by uid 1000, and
FS_IOC_REMOVE_ENCRYPTION_KEY will only succeed as uid 1000.  Or, if
both uids 1000 and 2000 added the key, then for each uid
FS_IOC_REMOVE_ENCRYPTION_KEY will only remove their own claim.  Only
once *both* are removed is the key really removed.  (Think of it like
unlinking a file that may have hard links.)

If FS_IOC_REMOVE_ENCRYPTION_KEY really removes the key, it will also
try to "lock" all files that had been unlocked with the key.  It won't
lock files that are still in-use, so this ioctl is expected to be used
in cooperation with userspace ensuring that none of the files are
still open.  However, if necessary, the ioctl can be executed again
later to retry locking any remaining files.

FS_IOC_REMOVE_ENCRYPTION_KEY returns 0 if either the key was removed
(but may still have files remaining to be locked), the user's claim to
the key was removed, or the key was already removed but had files
remaining to be the locked so the ioctl retried locking them.  In any
of these cases, ``removal_status_flags`` is filled in with the
following informational status flags:

- ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY``: set if some file(s)
  are still in-use.  Not guaranteed to be set in the case where only
  the user's claim to the key was removed.
- ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS``: set if only the
  user's claim to the key was removed, not the key itself

FS_IOC_REMOVE_ENCRYPTION_KEY can fail with the following errors:

- ``EACCES``: The FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR key specifier type
  was specified, but the caller does not have the CAP_SYS_ADMIN
  capability in the initial user namespace
- ``EINVAL``: invalid key specifier type, or reserved bits were set
- ``ENOKEY``: the key object was not found at all, i.e. it was never
  added in the first place or was already fully removed including all
  files locked; or, the user does not have a claim to the key.
- ``ENOTTY``: this type of filesystem does not implement encryption
- ``EOPNOTSUPP``: the kernel was not configured with encryption
  support for this filesystem, or the filesystem superblock has not
  had encryption enabled on it

FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS is exactly the same as
`FS_IOC_REMOVE_ENCRYPTION_KEY`_, except that for v2 policy keys, the
ALL_USERS version of the ioctl will remove all users' claims to the
key, not just the current user's.  I.e., the key itself will always be
removed, no matter how many users have added it.  This difference is
only meaningful if non-root users are adding and removing keys.

Because of this, FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS also requires
"root", namely the CAP_SYS_ADMIN capability in the initial user
namespace.  Otherwise it will fail with ``EACCES``.

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 14/16] f2fs: wire up new fscrypt ioctls
  2019-07-26 22:41 ` [PATCH v7 14/16] f2fs: " Eric Biggers
  2019-07-30  0:36   ` Jaegeuk Kim
@ 2019-08-02  8:10   ` Chao Yu
  2019-08-02 17:31     ` Eric Biggers
  1 sibling, 1 reply; 51+ messages in thread
From: Chao Yu @ 2019-08-02  8:10 UTC (permalink / raw)
  To: Eric Biggers, linux-fscrypt
  Cc: linux-fsdevel, linux-ext4, linux-f2fs-devel, linux-mtd,
	linux-api, linux-crypto, keyrings, Paul Crowley, Satya Tangirala

Hi Eric,

On 2019/7/27 6:41, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Wire up the new ioctls for adding and removing fscrypt keys to/from the
> filesystem, and the new ioctl for retrieving v2 encryption policies.
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY also required making f2fs_drop_inode() call
> fscrypt_drop_inode().
> 
> For more details see Documentation/filesystems/fscrypt.rst and the
> fscrypt patches that added the implementation of these ioctls.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

BTW, do you think it needs to make xxfs_has_support_encrypt() function be a
common interface defined in struct fscrypt_operations, as I see all
fscrypt_ioctl_*() needs to check with it, tho such cleanup is minor...

Thanks,

> ---
>  fs/f2fs/file.c  | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  fs/f2fs/super.c |  2 ++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index f8d46df8fa9ee..d81dda290b829 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -2184,6 +2184,40 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
>  	return err;
>  }
>  
> +static int f2fs_ioc_get_encryption_policy_ex(struct file *filp,
> +					     unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg);
> +}
> +
> +static int f2fs_ioc_add_encryption_key(struct file *filp, unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_add_key(filp, (void __user *)arg);
> +}
> +
> +static int f2fs_ioc_remove_encryption_key(struct file *filp, unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_remove_key(filp, (const void __user *)arg);
> +}
> +
> +static int f2fs_ioc_get_encryption_key_status(struct file *filp,
> +					      unsigned long arg)
> +{
> +	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
> +		return -EOPNOTSUPP;
> +
> +	return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
> +}
> +
>  static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
>  {
>  	struct inode *inode = file_inode(filp);
> @@ -3109,6 +3143,14 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		return f2fs_ioc_get_encryption_policy(filp, arg);
>  	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
>  		return f2fs_ioc_get_encryption_pwsalt(filp, arg);
> +	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
> +		return f2fs_ioc_get_encryption_policy_ex(filp, arg);
> +	case FS_IOC_ADD_ENCRYPTION_KEY:
> +		return f2fs_ioc_add_encryption_key(filp, arg);
> +	case FS_IOC_REMOVE_ENCRYPTION_KEY:
> +		return f2fs_ioc_remove_encryption_key(filp, arg);
> +	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
> +		return f2fs_ioc_get_encryption_key_status(filp, arg);
>  	case F2FS_IOC_GARBAGE_COLLECT:
>  		return f2fs_ioc_gc(filp, arg);
>  	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
> @@ -3236,6 +3278,10 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	case F2FS_IOC_SET_ENCRYPTION_POLICY:
>  	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
>  	case F2FS_IOC_GET_ENCRYPTION_POLICY:
> +	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
> +	case FS_IOC_ADD_ENCRYPTION_KEY:
> +	case FS_IOC_REMOVE_ENCRYPTION_KEY:
> +	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
>  	case F2FS_IOC_GARBAGE_COLLECT:
>  	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
>  	case F2FS_IOC_WRITE_CHECKPOINT:
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 6de6cda440315..f5fae8d511a20 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -913,6 +913,8 @@ static int f2fs_drop_inode(struct inode *inode)
>  		return 0;
>  	}
>  	ret = generic_drop_inode(inode);
> +	if (!ret)
> +		ret = fscrypt_drop_inode(inode);
>  	trace_f2fs_drop_inode(inode, ret);
>  	return ret;
>  }
> 

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 14/16] f2fs: wire up new fscrypt ioctls
  2019-08-02  8:10   ` Chao Yu
@ 2019-08-02 17:31     ` Eric Biggers
  2019-08-04  9:42       ` [f2fs-dev] " Chao Yu
  0 siblings, 1 reply; 51+ messages in thread
From: Eric Biggers @ 2019-08-02 17:31 UTC (permalink / raw)
  To: Chao Yu
  Cc: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Fri, Aug 02, 2019 at 04:10:15PM +0800, Chao Yu wrote:
> Hi Eric,
> 
> On 2019/7/27 6:41, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Wire up the new ioctls for adding and removing fscrypt keys to/from the
> > filesystem, and the new ioctl for retrieving v2 encryption policies.
> > 
> > FS_IOC_REMOVE_ENCRYPTION_KEY also required making f2fs_drop_inode() call
> > fscrypt_drop_inode().
> > 
> > For more details see Documentation/filesystems/fscrypt.rst and the
> > fscrypt patches that added the implementation of these ioctls.
> > 
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> 
> Reviewed-by: Chao Yu <yuchao0@huawei.com>
> 
> BTW, do you think it needs to make xxfs_has_support_encrypt() function be a
> common interface defined in struct fscrypt_operations, as I see all
> fscrypt_ioctl_*() needs to check with it, tho such cleanup is minor...
> 

Maybe.  It would work nicely for ext4 and f2fs, but ubifs does things
differently since it automatically enables the encryption feature if needed.
So we'd have to make the callback optional.

In any case, I think this should be separate from this patchset.

- Eric

^ permalink raw reply	[flat|nested] 51+ messages in thread

* [f2fs-dev] [PATCH v7 14/16] f2fs: wire up new fscrypt ioctls
  2019-08-02 17:31     ` Eric Biggers
@ 2019-08-04  9:42       ` " Chao Yu
  0 siblings, 0 replies; 51+ messages in thread
From: Chao Yu @ 2019-08-04  9:42 UTC (permalink / raw)
  To: Chao Yu, linux-fscrypt, linux-fsdevel, linux-ext4,
	linux-f2fs-devel, linux-mtd, linux-api, linux-crypto, keyrings,
	Paul Crowley, Satya Tangirala

On 2019-8-3 1:31, Eric Biggers wrote:
> On Fri, Aug 02, 2019 at 04:10:15PM +0800, Chao Yu wrote:
>> Hi Eric,
>>
>> On 2019/7/27 6:41, Eric Biggers wrote:
>>> From: Eric Biggers <ebiggers@google.com>
>>>
>>> Wire up the new ioctls for adding and removing fscrypt keys to/from the
>>> filesystem, and the new ioctl for retrieving v2 encryption policies.
>>>
>>> FS_IOC_REMOVE_ENCRYPTION_KEY also required making f2fs_drop_inode() call
>>> fscrypt_drop_inode().
>>>
>>> For more details see Documentation/filesystems/fscrypt.rst and the
>>> fscrypt patches that added the implementation of these ioctls.
>>>
>>> Signed-off-by: Eric Biggers <ebiggers@google.com>
>>
>> Reviewed-by: Chao Yu <yuchao0@huawei.com>
>>
>> BTW, do you think it needs to make xxfs_has_support_encrypt() function be a
>> common interface defined in struct fscrypt_operations, as I see all
>> fscrypt_ioctl_*() needs to check with it, tho such cleanup is minor...
>>
> 
> Maybe.  It would work nicely for ext4 and f2fs, but ubifs does things
> differently since it automatically enables the encryption feature if needed.
> So we'd have to make the callback optional.

Correct, ubifs can leave the callback as NULL function pointer.

> 
> In any case, I think this should be separate from this patchset.

Yup, it can be done in a separated patch if need.

Thanks,

> 
> - Eric
> 
> 
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> 

^ permalink raw reply	[flat|nested] 51+ messages in thread

* Re: [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  2019-08-02  4:38                 ` Eric Biggers
@ 2019-08-12 14:16                   ` Theodore Y. Ts'o
  0 siblings, 0 replies; 51+ messages in thread
From: Theodore Y. Ts'o @ 2019-08-12 14:16 UTC (permalink / raw)
  To: linux-fscrypt, linux-fsdevel, linux-ext4, linux-f2fs-devel,
	linux-mtd, linux-api, linux-crypto, keyrings, Paul Crowley,
	Satya Tangirala

On Thu, Aug 01, 2019 at 09:38:27PM -0700, Eric Biggers wrote:
> 
> Here's a slightly updated version (I missed removing some stale text):

Apologies for the delaying in getting back.  Thanks, this looks great.

	      	  	      	      	     - Ted

> 
> Removing keys
> -------------
> 
> Two ioctls are available for removing a key that was added by
> `FS_IOC_ADD_ENCRYPTION_KEY`_:
> 
> - `FS_IOC_REMOVE_ENCRYPTION_KEY`_
> - `FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS`_
> 
> These two ioctls differ only in cases where v2 policy keys are added
> or removed by non-root users.
> 
> These ioctls don't work on keys that were added via the legacy
> process-subscribed keyrings mechanism.
> 
> Before using these ioctls, read the `Kernel memory compromise`_
> section for a discussion of the security goals and limitations of
> these ioctls.
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> The FS_IOC_REMOVE_ENCRYPTION_KEY ioctl removes a claim to a master
> encryption key from the filesystem, and possibly removes the key
> itself.  It can be executed on any file or directory on the target
> filesystem, but using the filesystem's root directory is recommended.
> It takes in a pointer to a :c:type:`struct fscrypt_remove_key_arg`,
> defined as follows::
> 
>     struct fscrypt_remove_key_arg {
>             struct fscrypt_key_specifier key_spec;
>     #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY      0x00000001
>     #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS     0x00000002
>             __u32 removal_status_flags;     /* output */
>             __u32 __reserved[5];
>     };
> 
> This structure must be zeroed, then initialized as follows:
> 
> - The key to remove is specified by ``key_spec``:
> 
>     - To remove a key used by v1 encryption policies, set
>       ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
>       in ``key_spec.u.descriptor``.  To remove this type of key, the
>       calling process must have the CAP_SYS_ADMIN capability in the
>       initial user namespace.
> 
>     - To remove a key used by v2 encryption policies, set
>       ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
>       in ``key_spec.u.identifier``.
> 
> For v2 policy keys, this ioctl is usable by non-root users.  However,
> to make this possible, it actually just removes the current user's
> claim to the key, undoing a single call to FS_IOC_ADD_ENCRYPTION_KEY.
> Only after all claims are removed is the key really removed.
> 
> For example, if FS_IOC_ADD_ENCRYPTION_KEY was called with uid 1000,
> then the key will be "claimed" by uid 1000, and
> FS_IOC_REMOVE_ENCRYPTION_KEY will only succeed as uid 1000.  Or, if
> both uids 1000 and 2000 added the key, then for each uid
> FS_IOC_REMOVE_ENCRYPTION_KEY will only remove their own claim.  Only
> once *both* are removed is the key really removed.  (Think of it like
> unlinking a file that may have hard links.)
> 
> If FS_IOC_REMOVE_ENCRYPTION_KEY really removes the key, it will also
> try to "lock" all files that had been unlocked with the key.  It won't
> lock files that are still in-use, so this ioctl is expected to be used
> in cooperation with userspace ensuring that none of the files are
> still open.  However, if necessary, the ioctl can be executed again
> later to retry locking any remaining files.
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY returns 0 if either the key was removed
> (but may still have files remaining to be locked), the user's claim to
> the key was removed, or the key was already removed but had files
> remaining to be the locked so the ioctl retried locking them.  In any
> of these cases, ``removal_status_flags`` is filled in with the
> following informational status flags:
> 
> - ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY``: set if some file(s)
>   are still in-use.  Not guaranteed to be set in the case where only
>   the user's claim to the key was removed.
> - ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS``: set if only the
>   user's claim to the key was removed, not the key itself
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY can fail with the following errors:
> 
> - ``EACCES``: The FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR key specifier type
>   was specified, but the caller does not have the CAP_SYS_ADMIN
>   capability in the initial user namespace
> - ``EINVAL``: invalid key specifier type, or reserved bits were set
> - ``ENOKEY``: the key object was not found at all, i.e. it was never
>   added in the first place or was already fully removed including all
>   files locked; or, the user does not have a claim to the key.
> - ``ENOTTY``: this type of filesystem does not implement encryption
> - ``EOPNOTSUPP``: the kernel was not configured with encryption
>   support for this filesystem, or the filesystem superblock has not
>   had encryption enabled on it
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS is exactly the same as
> `FS_IOC_REMOVE_ENCRYPTION_KEY`_, except that for v2 policy keys, the
> ALL_USERS version of the ioctl will remove all users' claims to the
> key, not just the current user's.  I.e., the key itself will always be
> removed, no matter how many users have added it.  This difference is
> only meaningful if non-root users are adding and removing keys.
> 
> Because of this, FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS also requires
> "root", namely the CAP_SYS_ADMIN capability in the initial user
> namespace.  Otherwise it will fail with ``EACCES``.

^ permalink raw reply	[flat|nested] 51+ messages in thread

end of thread, back to index

Thread overview: 51+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-26 22:41 [PATCH v7 00/16] fscrypt: key management improvements Eric Biggers
2019-07-26 22:41 ` [PATCH v7 01/16] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h> Eric Biggers
2019-07-28 15:08   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 02/16] fscrypt: use FSCRYPT_ prefix for uapi constants Eric Biggers
2019-07-26 22:41 ` [PATCH v7 03/16] fscrypt: use FSCRYPT_* definitions, not FS_* Eric Biggers
2019-07-26 22:41 ` [PATCH v7 04/16] fscrypt: add ->ci_inode to fscrypt_info Eric Biggers
2019-07-28 15:09   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 05/16] fscrypt: refactor v1 policy key setup into keysetup_legacy.c Eric Biggers
2019-07-28 15:40   ` Theodore Y. Ts'o
2019-07-29 19:37     ` Eric Biggers
2019-07-26 22:41 ` [PATCH v7 06/16] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Eric Biggers
2019-07-28 18:50   ` Theodore Y. Ts'o
2019-07-29 19:46     ` Eric Biggers
2019-07-29 20:14       ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 07/16] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl Eric Biggers
2019-07-28 19:24   ` Theodore Y. Ts'o
2019-07-29 19:58     ` Eric Biggers
2019-07-31 18:38       ` Eric Biggers
2019-07-31 23:38         ` Theodore Y. Ts'o
2019-08-01  1:11           ` [f2fs-dev] " Eric Biggers
2019-08-01  5:31             ` Theodore Y. Ts'o
2019-08-01 18:35               ` Eric Biggers
2019-08-01 18:46                 ` Eric Biggers
2019-08-01 22:04               ` Eric Biggers
2019-08-02  4:38                 ` Eric Biggers
2019-08-12 14:16                   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 08/16] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl Eric Biggers
2019-07-28 19:30   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 09/16] fscrypt: add an HKDF-SHA512 implementation Eric Biggers
2019-07-28 19:39   ` Theodore Y. Ts'o
2019-07-29 20:29     ` Eric Biggers
2019-07-29 21:42       ` James Bottomley
2019-07-26 22:41 ` [PATCH v7 10/16] fscrypt: v2 encryption policy support Eric Biggers
2019-07-28 21:17   ` Theodore Y. Ts'o
2019-07-29 20:46     ` Eric Biggers
2019-07-26 22:41 ` [PATCH v7 11/16] fscrypt: allow unprivileged users to add/remove keys for v2 policies Eric Biggers
2019-07-28 21:22   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 12/16] fscrypt: require that key be added when setting a v2 encryption policy Eric Biggers
2019-07-28 21:24   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 13/16] ext4: wire up new fscrypt ioctls Eric Biggers
2019-07-28 21:24   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 14/16] f2fs: " Eric Biggers
2019-07-30  0:36   ` Jaegeuk Kim
2019-08-02  8:10   ` Chao Yu
2019-08-02 17:31     ` Eric Biggers
2019-08-04  9:42       ` [f2fs-dev] " Chao Yu
2019-07-26 22:41 ` [PATCH v7 15/16] ubifs: " Eric Biggers
2019-07-30  0:39   ` Theodore Y. Ts'o
2019-07-26 22:41 ` [PATCH v7 16/16] fscrypt: document the new ioctls and policy version Eric Biggers
2019-07-29  2:00   ` Theodore Y. Ts'o
2019-07-29 21:36     ` Eric Biggers

Linux-Crypto Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-crypto/0 linux-crypto/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-crypto linux-crypto/ https://lore.kernel.org/linux-crypto \
		linux-crypto@vger.kernel.org linux-crypto@archiver.kernel.org
	public-inbox-index linux-crypto


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-crypto


AGPL code for this site: git clone https://public-inbox.org/ public-inbox