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* [PATCH v10 00/12] Appended signatures support for IMA appraisal
@ 2019-04-18  3:51 Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 01/12] MODSIGN: Export module signature definitions Thiago Jung Bauermann
                   ` (11 more replies)
  0 siblings, 12 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Hello,

There are two big changes in this version:

1. The modsig contents aren't stored anymore in the struct xattr_value which
is passed around in IMA for the xattr sig or digest. Instead, a new struct
modsig argument is passed alongside xattr_value in relevant IMA functions.
This change was suggested by Mimi Zohar, and allowed cleaner handling of the
modsig in the code (especially in process_measurement()).

2. There are separate template fields for the modsig and its digest. This
was also suggested by Mimi Zhoar. Because of this change, we don't need to
know anymore at measurement time whether the modsig or the xattr sig will be
used for appraisal (in the case where a file has both types of signature
available). This avoids needing to peek at the xattr sig and at the modsig
to see if their signatures use known keys, which we had to do before in
order to know at measurement time which sig would be used for appraisal, so
that we would store the correct signature in the measurement list.

The changelog below has the details. The patches apply on today's
linux-integrity/next-integrity.

Original cover letter:

On the OpenPOWER platform, secure boot and trusted boot are being
implemented using IMA for taking measurements and verifying signatures.
Since the kernel image on Power servers is an ELF binary, kernels are
signed using the scripts/sign-file tool and thus use the same signature
format as signed kernel modules.

This patch series adds support in IMA for verifying those signatures.
It adds flexibility to OpenPOWER secure boot, because it allows it to boot
kernels with the signature appended to them as well as kernels where the
signature is stored in the IMA extended attribute.

Changes since v9:

- Patch "MODSIGN: Export module signature definitions"
  - Moved mod_check_sig() to a new file so that CONFIG_IMA_APPRAISE_MODSIG
    doesn't have to depend on CONFIG_MODULES.
  - Changed scripts/Makefile to build sign-file if CONFIG_MODULE_SIG_FORMAT
    is set.
  - Removed Mimi's Reviewed-by because of the changes in this version.

- Patch "PKCS#7: Refactor verify_pkcs7_signature()"
  - Don't add function pkcs7_get_message_sig() anymore, since it's not
    needed in the current version.

- Patch "PKCS#7: Introduce pkcs7_get_digest()"
  - Changed 'len' argument from 'u8 *' to 'u32 *'.
  - Added 'hash_algo' argument to obtain the algo used for the digest.
  - Don't check whether 'buf', 'len' and 'hash_algo' output arguments are NULL,
    since the function's only caller always sets them.
  - Removed Mimi's Reviewed-by because of the changes in this version.

- Patch "integrity: Introduce asymmetric_sig_has_known_key()"
  - Dropped.

- Patch "integrity: Introduce integrity_keyring_from_id"
  - Squashed into "ima: Implement support for module-style appended signatures"
  - Changed integrity_keyring_from_id() to a static function (suggested by Mimi
    Zohar).

- Patch "ima: Introduce is_signed()"
  - Dropped.

- Patch "ima: Export func_tokens"
  - Squashed into "ima: Implement support for module-style appended signatures"

- Patch "ima: Use designated initializers for struct ima_event_data"
  - New patch.

- Patch "ima: Factor xattr_verify() out of ima_appraise_measurement()"
  - New patch.

- Patch "ima: Implement support for module-style appended signatures"
  - Renamed 'struct modsig_hdr' to 'struct modsig'.
  - Added integrity_modsig_verify() to integrity/digsig.c so that it's not
    necessary to export integrity_keyring_from_id() (Suggested by Mimi Zohar).
  - Don't add functions ima_xattr_sig_known_key() and
    modsig_has_known_key() since they're not necessary anymore.
  - Added modsig argument to ima_appraise_measurement().
  - Verify modsig in a separate function called by ima_appraise_measurement().
  - Renamed ima_read_collect_modsig() to ima_read_modsig(), with a separate
    collect function added in patch "ima: Collect modsig" (suggested by Mimi
    Zohar).
  - In ima_read_modsig(), moved code saving of raw PKCS7 data to 'struct
    modsig' to patch "ima: Collect modsig".
  - In ima_read_modsig(), moved all parts related to the modsig hash to
    patch "ima: Collect modsig".
  - In ima_read_modsig(), don't check if the buf pointer is NULL since it's
    never supposed to happen.
  - Renamed ima_free_xattr_data() to ima_free_modsig().
  - No need to check for modsig in ima_read_xattr() and
    ima_inode_set_xattr() anymore.
  - In ima_modsig_verify(), don't check if the modsig pointer is NULL since
    it's not supposed to happen.
  - Don't define IMA_MODSIG element in enum evm_ima_xattr_type.

- Patch "ima: Collect modsig"
  - New patch.

- Patch "ima: Define ima-modsig template"
  - Patch renamed from "ima: Add new "d-sig" template field"
  - Renamed 'd-sig' template field to 'd-modsig'.
  - Added 'modsig' template field.
  - Added 'ima-modsig' defined template descriptor.
  - Renamed ima_modsig_serialize_data() to ima_modsig_serialize().
  - Renamed ima_get_modsig_hash() to ima_get_modsig_digest(). Also the
    function is a lot simpler now since what it used to do is now done in
    ima_collect_modsig() and pkcs7_get_digest().
  - Added check for failed modsig collection in ima_eventdigest_modsig_init().
  - Added modsig argument to ima_store_measurement().
  - Added 'modsig' field to struct ima_event_data.
  - Removed check for modsig == NULL in ima_get_modsig_digest() and in
    ima_modsig_serialize_data() since their callers already performs that
    check.
  - Moved check_current_template_modsig() to this patch, previously was in
    "ima: Store the measurement again when appraising a modsig".

- Patch "ima: Store the measurement again when appraising a modsig"
  - Renamed ima_template_has_sig() to ima_template_has_modsig().
  - Added a change to ima_collect_measurement(), making it to call
    ima_collect_modsig() even if IMA_COLLECT is set in iint->flags.
  - Removed IMA_READ_MEASURE flag.
  - Renamed template_has_sig global variable to template_has_modsig.
  - Renamed find_sig_in_template() to find_modsig_in_template().

Changes since v8:
- Patch "MODSIGN: Export module signature definitions"
  - Renamed validate_module_sig() to mod_check_sig(). (Suggested by
    Mimi Zohar).

- Patch "integrity: Introduce struct evm_xattr"
  - Added comment mentioning that the evm_xattr usage is limited to HMAC
    before the structure definition. (Suggested by Mimi Zohar)

- Patch "ima: Add modsig appraise_type option for module-style appended
         signatures"
  - Added MODULE_CHECK to whitelist of hooks allowed to use modsig, and
    removed FIRMWARE_CHECK. (Suggested by Mimi Zohar and James Morris)

- Patch "ima: Implement support for module-style appended signatures"
  - Moved call to ima_modsig_verify() from ima_appraise_measurement() to
    integrity_digsig_verify(). (Suggested by Mimi Zohar)
  - Renamed ima_read_modsig() to ima_read_collect_modsig() and made it force
    PKCS7 code to calculate the file hash. (Suggested by Mimi Zohar)
  - Build sign-file tool if IMA_APPRAISE_MODSIG is enabled.
  - Check whether the signing key is in the platform keyring as a fallback
    for the KEXEC_KERNEL hook. (Suggested by Mimi Zohar)

- Patch "ima: Store the measurement again when appraising a modsig"
  - In process_measurement(), when a new measurement needs to be stored
    re-add IMA_MEASURE flag when the modsig is read rather than changing the
    if condition when calling ima_store_measurement(). (Suggested by Mimi
    Zohar)
  - Check whether ima_template has "sig" and "d-sig" fields at
    initialization rather than at the first time the check is needed.
    (suggested by Mimi Zohar)

Changes since v7:
- Patch "MODSIGN: Export module signature definitions"
  - Added module name parameter to validate_module_sig() so that it can be
    shown in error messages.

- Patch "integrity: Introduce struct evm_xattr"
  - Dropped use of struct evm_xattr in evm_update_evmxattr() and
    evm_verify_hmac(). It's not needed there anymore because of changes
    to support portable EVM signatures.

Thiago Jung Bauermann (12):
  MODSIGN: Export module signature definitions
  PKCS#7: Refactor verify_pkcs7_signature()
  PKCS#7: Introduce pkcs7_get_digest()
  integrity: Introduce struct evm_xattr
  integrity: Select CONFIG_KEYS instead of depending on it
  ima: Use designated initializers for struct ima_event_data
  ima: Add modsig appraise_type option for module-style appended
    signatures
  ima: Factor xattr_verify() out of ima_appraise_measurement()
  ima: Implement support for module-style appended signatures
  ima: Collect modsig
  ima: Define ima-modsig template
  ima: Store the measurement again when appraising a modsig

 Documentation/ABI/testing/ima_policy      |   6 +-
 Documentation/security/IMA-templates.rst  |   7 +-
 certs/system_keyring.c                    |  61 +++++--
 crypto/asymmetric_keys/pkcs7_verify.c     |  33 ++++
 include/crypto/pkcs7.h                    |   4 +
 include/linux/module.h                    |   3 -
 include/linux/module_signature.h          |  44 +++++
 include/linux/verification.h              |  10 ++
 init/Kconfig                              |   6 +-
 kernel/Makefile                           |   1 +
 kernel/module.c                           |   1 +
 kernel/module_signature.c                 |  45 +++++
 kernel/module_signing.c                   |  56 +-----
 scripts/Makefile                          |   2 +-
 security/integrity/Kconfig                |   2 +-
 security/integrity/digsig.c               |  39 ++++-
 security/integrity/evm/evm_main.c         |   8 +-
 security/integrity/ima/Kconfig            |  13 ++
 security/integrity/ima/Makefile           |   1 +
 security/integrity/ima/ima.h              |  61 ++++++-
 security/integrity/ima/ima_api.c          |  33 +++-
 security/integrity/ima/ima_appraise.c     | 198 ++++++++++++++--------
 security/integrity/ima/ima_init.c         |   4 +-
 security/integrity/ima/ima_main.c         |  23 ++-
 security/integrity/ima/ima_modsig.c       | 169 ++++++++++++++++++
 security/integrity/ima/ima_policy.c       |  64 ++++++-
 security/integrity/ima/ima_template.c     |  31 +++-
 security/integrity/ima/ima_template_lib.c |  60 ++++++-
 security/integrity/ima/ima_template_lib.h |   4 +
 security/integrity/integrity.h            |  26 +++
 30 files changed, 836 insertions(+), 179 deletions(-)
 create mode 100644 include/linux/module_signature.h
 create mode 100644 kernel/module_signature.c
 create mode 100644 security/integrity/ima/ima_modsig.c


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 01/12] MODSIGN: Export module signature definitions
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 15:42   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 02/12] PKCS#7: Refactor verify_pkcs7_signature() Thiago Jung Bauermann
                   ` (10 subsequent siblings)
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

IMA will use the module_signature format for append signatures, so export
the relevant definitions and factor out the code which verifies that the
appended signature trailer is valid.

Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
and be able to use mod_check_sig() without having to depend on either
CONFIG_MODULE_SIG or CONFIG_MODULES.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Jessica Yu <jeyu@kernel.org>
---
 include/linux/module.h           |  3 --
 include/linux/module_signature.h | 44 +++++++++++++++++++++++++
 init/Kconfig                     |  6 +++-
 kernel/Makefile                  |  1 +
 kernel/module.c                  |  1 +
 kernel/module_signature.c        | 45 +++++++++++++++++++++++++
 kernel/module_signing.c          | 56 +++++---------------------------
 scripts/Makefile                 |  2 +-
 8 files changed, 105 insertions(+), 53 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 73ee2b10e816..cd919ec972d6 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -25,9 +25,6 @@
 #include <linux/percpu.h>
 #include <asm/module.h>
 
-/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
-#define MODULE_SIG_STRING "~Module signature appended~\n"
-
 /* Not Yet Implemented */
 #define MODULE_SUPPORTED_DEVICE(name)
 
diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
new file mode 100644
index 000000000000..523617fc5b6a
--- /dev/null
+++ b/include/linux/module_signature.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Module signature handling.
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_MODULE_SIGNATURE_H
+#define _LINUX_MODULE_SIGNATURE_H
+
+/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
+#define MODULE_SIG_STRING "~Module signature appended~\n"
+
+enum pkey_id_type {
+	PKEY_ID_PGP,		/* OpenPGP generated key ID */
+	PKEY_ID_X509,		/* X.509 arbitrary subjectKeyIdentifier */
+	PKEY_ID_PKCS7,		/* Signature in PKCS#7 message */
+};
+
+/*
+ * Module signature information block.
+ *
+ * The constituents of the signature section are, in order:
+ *
+ *	- Signer's name
+ *	- Key identifier
+ *	- Signature data
+ *	- Information block
+ */
+struct module_signature {
+	u8	algo;		/* Public-key crypto algorithm [0] */
+	u8	hash;		/* Digest algorithm [0] */
+	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
+	u8	signer_len;	/* Length of signer's name [0] */
+	u8	key_id_len;	/* Length of key identifier [0] */
+	u8	__pad[3];
+	__be32	sig_len;	/* Length of signature data */
+};
+
+int mod_check_sig(const struct module_signature *ms, size_t file_len,
+		  const char *name);
+
+#endif /* _LINUX_MODULE_SIGNATURE_H */
diff --git a/init/Kconfig b/init/Kconfig
index 4592bf7997c0..a71019553ee1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
 config MODULE_SIG
 	bool "Module signature verification"
 	depends on MODULES
-	select SYSTEM_DATA_VERIFICATION
+	select MODULE_SIG_FORMAT
 	help
 	  Check modules for valid signatures upon load: the signature
 	  is simply appended to the module. For more information see
@@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
 
 endif # MODULES
 
+config MODULE_SIG_FORMAT
+	def_bool n
+	select SYSTEM_DATA_VERIFICATION
+
 config MODULES_TREE_LOOKUP
 	def_bool y
 	depends on PERF_EVENTS || TRACING
diff --git a/kernel/Makefile b/kernel/Makefile
index 6c57e78817da..d2f2488f80ab 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -57,6 +57,7 @@ endif
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_MODULE_SIG) += module_signing.o
+obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_CRASH_CORE) += crash_core.o
diff --git a/kernel/module.c b/kernel/module.c
index 985caa467aef..326ddeb364dd 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -19,6 +19,7 @@
 #include <linux/export.h>
 #include <linux/extable.h>
 #include <linux/moduleloader.h>
+#include <linux/module_signature.h>
 #include <linux/trace_events.h>
 #include <linux/init.h>
 #include <linux/kallsyms.h>
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
new file mode 100644
index 000000000000..6d5e59f27f55
--- /dev/null
+++ b/kernel/module_signature.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Module signature checker
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/errno.h>
+#include <linux/printk.h>
+#include <linux/module_signature.h>
+#include <asm/byteorder.h>
+
+/**
+ * mod_check_sig - check that the given signature is sane
+ *
+ * @ms:		Signature to check.
+ * @file_len:	Size of the file to which @ms is appended.
+ */
+int mod_check_sig(const struct module_signature *ms, size_t file_len,
+		  const char *name)
+{
+	if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
+		return -EBADMSG;
+
+	if (ms->id_type != PKEY_ID_PKCS7) {
+		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
+		       name);
+		return -ENOPKG;
+	}
+
+	if (ms->algo != 0 ||
+	    ms->hash != 0 ||
+	    ms->signer_len != 0 ||
+	    ms->key_id_len != 0 ||
+	    ms->__pad[0] != 0 ||
+	    ms->__pad[1] != 0 ||
+	    ms->__pad[2] != 0) {
+		pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
+		       name);
+		return -EBADMSG;
+	}
+
+	return 0;
+}
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 6b9a926fd86b..cdd04a6b8074 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -11,37 +11,13 @@
 
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/module_signature.h>
 #include <linux/string.h>
 #include <linux/verification.h>
 #include <crypto/public_key.h>
 #include "module-internal.h"
 
-enum pkey_id_type {
-	PKEY_ID_PGP,		/* OpenPGP generated key ID */
-	PKEY_ID_X509,		/* X.509 arbitrary subjectKeyIdentifier */
-	PKEY_ID_PKCS7,		/* Signature in PKCS#7 message */
-};
-
-/*
- * Module signature information block.
- *
- * The constituents of the signature section are, in order:
- *
- *	- Signer's name
- *	- Key identifier
- *	- Signature data
- *	- Information block
- */
-struct module_signature {
-	u8	algo;		/* Public-key crypto algorithm [0] */
-	u8	hash;		/* Digest algorithm [0] */
-	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
-	u8	signer_len;	/* Length of signer's name [0] */
-	u8	key_id_len;	/* Length of key identifier [0] */
-	u8	__pad[3];
-	__be32	sig_len;	/* Length of signature data */
-};
-
 /*
  * Verify the signature on a module.
  */
@@ -49,6 +25,7 @@ int mod_verify_sig(const void *mod, struct load_info *info)
 {
 	struct module_signature ms;
 	size_t sig_len, modlen = info->len;
+	int ret;
 
 	pr_devel("==>%s(,%zu)\n", __func__, modlen);
 
@@ -56,32 +33,15 @@ int mod_verify_sig(const void *mod, struct load_info *info)
 		return -EBADMSG;
 
 	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
-	modlen -= sizeof(ms);
+
+	ret = mod_check_sig(&ms, modlen, info->name);
+	if (ret)
+		return ret;
 
 	sig_len = be32_to_cpu(ms.sig_len);
-	if (sig_len >= modlen)
-		return -EBADMSG;
-	modlen -= sig_len;
+	modlen -= sig_len + sizeof(ms);
 	info->len = modlen;
 
-	if (ms.id_type != PKEY_ID_PKCS7) {
-		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
-		       info->name);
-		return -ENOPKG;
-	}
-
-	if (ms.algo != 0 ||
-	    ms.hash != 0 ||
-	    ms.signer_len != 0 ||
-	    ms.key_id_len != 0 ||
-	    ms.__pad[0] != 0 ||
-	    ms.__pad[1] != 0 ||
-	    ms.__pad[2] != 0) {
-		pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
-		       info->name);
-		return -EBADMSG;
-	}
-
 	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
 				      VERIFY_USE_SECONDARY_KEYRING,
 				      VERIFYING_MODULE_SIGNATURE,
diff --git a/scripts/Makefile b/scripts/Makefile
index 9d442ee050bd..52098b080ab7 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -17,7 +17,7 @@ hostprogs-$(CONFIG_VT)           += conmakehash
 hostprogs-$(BUILD_C_RECORDMCOUNT) += recordmcount
 hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable
 hostprogs-$(CONFIG_ASN1)	 += asn1_compiler
-hostprogs-$(CONFIG_MODULE_SIG)	 += sign-file
+hostprogs-$(CONFIG_MODULE_SIG_FORMAT) += sign-file
 hostprogs-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += extract-cert
 hostprogs-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE) += insert-sys-cert
 


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 02/12] PKCS#7: Refactor verify_pkcs7_signature()
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 01/12] MODSIGN: Export module signature definitions Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 15:42   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 03/12] PKCS#7: Introduce pkcs7_get_digest() Thiago Jung Bauermann
                   ` (9 subsequent siblings)
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

IMA will need to verify a PKCS#7 signature which has already been parsed.
For this reason, factor out the code which does that from
verify_pkcs7_signature() into a new function which takes a struct
pkcs7_message instead of a data buffer.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
---
 certs/system_keyring.c       | 61 ++++++++++++++++++++++++++----------
 include/linux/verification.h | 10 ++++++
 2 files changed, 55 insertions(+), 16 deletions(-)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index c05c29ae4d5d..4ba82e52e4b4 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -194,33 +194,27 @@ late_initcall(load_system_certificate_list);
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 
 /**
- * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
+ * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
  * @data: The data to be verified (NULL if expecting internal data).
  * @len: Size of @data.
- * @raw_pkcs7: The PKCS#7 message that is the signature.
- * @pkcs7_len: The size of @raw_pkcs7.
+ * @pkcs7: The PKCS#7 message that is the signature.
  * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
  *					(void *)1UL for all trusted keys).
  * @usage: The use to which the key is being put.
  * @view_content: Callback to gain access to content.
  * @ctx: Context for callback.
  */
-int verify_pkcs7_signature(const void *data, size_t len,
-			   const void *raw_pkcs7, size_t pkcs7_len,
-			   struct key *trusted_keys,
-			   enum key_being_used_for usage,
-			   int (*view_content)(void *ctx,
-					       const void *data, size_t len,
-					       size_t asn1hdrlen),
-			   void *ctx)
+int verify_pkcs7_message_sig(const void *data, size_t len,
+			     struct pkcs7_message *pkcs7,
+			     struct key *trusted_keys,
+			     enum key_being_used_for usage,
+			     int (*view_content)(void *ctx,
+						 const void *data, size_t len,
+						 size_t asn1hdrlen),
+			     void *ctx)
 {
-	struct pkcs7_message *pkcs7;
 	int ret;
 
-	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
-	if (IS_ERR(pkcs7))
-		return PTR_ERR(pkcs7);
-
 	/* The data should be detached - so we need to supply it. */
 	if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 		pr_err("PKCS#7 signature with non-detached data\n");
@@ -273,6 +267,41 @@ int verify_pkcs7_signature(const void *data, size_t len,
 	}
 
 error:
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;
+}
+
+/**
+ * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
+ * @data: The data to be verified (NULL if expecting internal data).
+ * @len: Size of @data.
+ * @raw_pkcs7: The PKCS#7 message that is the signature.
+ * @pkcs7_len: The size of @raw_pkcs7.
+ * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
+ *					(void *)1UL for all trusted keys).
+ * @usage: The use to which the key is being put.
+ * @view_content: Callback to gain access to content.
+ * @ctx: Context for callback.
+ */
+int verify_pkcs7_signature(const void *data, size_t len,
+			   const void *raw_pkcs7, size_t pkcs7_len,
+			   struct key *trusted_keys,
+			   enum key_being_used_for usage,
+			   int (*view_content)(void *ctx,
+					       const void *data, size_t len,
+					       size_t asn1hdrlen),
+			   void *ctx)
+{
+	struct pkcs7_message *pkcs7;
+	int ret;
+
+	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
+	if (IS_ERR(pkcs7))
+		return PTR_ERR(pkcs7);
+
+	ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
+				       view_content, ctx);
+
 	pkcs7_free_message(pkcs7);
 	pr_devel("<==%s() = %d\n", __func__, ret);
 	return ret;
diff --git a/include/linux/verification.h b/include/linux/verification.h
index 018fb5f13d44..5e1d41f2b336 100644
--- a/include/linux/verification.h
+++ b/include/linux/verification.h
@@ -36,6 +36,7 @@ extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR];
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 
 struct key;
+struct pkcs7_message;
 
 extern int verify_pkcs7_signature(const void *data, size_t len,
 				  const void *raw_pkcs7, size_t pkcs7_len,
@@ -45,6 +46,15 @@ extern int verify_pkcs7_signature(const void *data, size_t len,
 						      const void *data, size_t len,
 						      size_t asn1hdrlen),
 				  void *ctx);
+extern int verify_pkcs7_message_sig(const void *data, size_t len,
+				    struct pkcs7_message *pkcs7,
+				    struct key *trusted_keys,
+				    enum key_being_used_for usage,
+				    int (*view_content)(void *ctx,
+							const void *data,
+							size_t len,
+							size_t asn1hdrlen),
+				    void *ctx);
 
 #ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
 extern int verify_pefile_signature(const void *pebuf, unsigned pelen,


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 03/12] PKCS#7: Introduce pkcs7_get_digest()
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 01/12] MODSIGN: Export module signature definitions Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 02/12] PKCS#7: Refactor verify_pkcs7_signature() Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 15:42   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 04/12] integrity: Introduce struct evm_xattr Thiago Jung Bauermann
                   ` (8 subsequent siblings)
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

IMA will need to access the digest of the PKCS7 message (as calculated by
the kernel) before the signature is verified, so introduce
pkcs7_get_digest() for that purpose.

Also, modify pkcs7_digest() to detect when the digest was already
calculated so that it doesn't have to do redundant work. Verifying that
sinfo->sig->digest isn't NULL is sufficient because both places which
allocate sinfo->sig (pkcs7_parse_message() and pkcs7_note_signed_info())
use kzalloc() so sig->digest is always initialized to zero.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
---
 crypto/asymmetric_keys/pkcs7_verify.c | 33 +++++++++++++++++++++++++++
 include/crypto/pkcs7.h                |  4 ++++
 2 files changed, 37 insertions(+)

diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 97c77f66b20d..5c3de46b0b73 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -16,6 +16,7 @@
 #include <linux/err.h>
 #include <linux/asn1.h>
 #include <crypto/hash.h>
+#include <crypto/hash_info.h>
 #include <crypto/public_key.h>
 #include "pkcs7_parser.h"
 
@@ -33,6 +34,10 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7,
 
 	kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo);
 
+	/* The digest was calculated already. */
+	if (sig->digest)
+		return 0;
+
 	if (!sinfo->sig->hash_algo)
 		return -ENOPKG;
 
@@ -122,6 +127,34 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7,
 	return ret;
 }
 
+int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf, u32 *len,
+		     enum hash_algo *hash_algo)
+{
+	struct pkcs7_signed_info *sinfo = pkcs7->signed_infos;
+	int i, ret;
+
+	/*
+	 * This function doesn't support messages with more than one signature.
+	 */
+	if (sinfo == NULL || sinfo->next != NULL)
+		return -EBADMSG;
+
+	ret = pkcs7_digest(pkcs7, sinfo);
+	if (ret)
+		return ret;
+
+	*buf = sinfo->sig->digest;
+	*len = sinfo->sig->digest_size;
+
+	for (i = 0; i < HASH_ALGO__LAST; i++)
+		if (!strcmp(hash_algo_name[i], sinfo->sig->hash_algo)) {
+			*hash_algo = i;
+			break;
+		}
+
+	return 0;
+}
+
 /*
  * Find the key (X.509 certificate) to use to verify a PKCS#7 message.  PKCS#7
  * uses the issuer's name and the issuing certificate serial number for
diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index 583f199400a3..3bfe6829eaae 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -13,6 +13,7 @@
 #define _CRYPTO_PKCS7_H
 
 #include <linux/verification.h>
+#include <linux/hash_info.h>
 #include <crypto/public_key.h>
 
 struct key;
@@ -44,4 +45,7 @@ extern int pkcs7_verify(struct pkcs7_message *pkcs7,
 extern int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
 				      const void *data, size_t datalen);
 
+extern int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf,
+			    u32 *len, enum hash_algo *hash_algo);
+
 #endif /* _CRYPTO_PKCS7_H */


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 04/12] integrity: Introduce struct evm_xattr
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (2 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 03/12] PKCS#7: Introduce pkcs7_get_digest() Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 05/12] integrity: Select CONFIG_KEYS instead of depending on it Thiago Jung Bauermann
                   ` (7 subsequent siblings)
  11 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Even though struct evm_ima_xattr_data includes a fixed-size array to hold a
SHA1 digest, most of the code ignores the array and uses the struct to mean
"type indicator followed by data of unspecified size" and tracks the real
size of what the struct represents in a separate length variable.

The only exception to that is the EVM code, which correctly uses the
definition of struct evm_ima_xattr_data.

So make this explicit in the code by removing the length specification from
the array in struct evm_ima_xattr_data. Also, change the name of the
element from digest to data since in most places the array doesn't hold a
digest.

A separate struct evm_xattr is introduced, with the original definition of
evm_ima_xattr_data to be used in the places that actually expect that
definition, specifically the EVM HMAC code.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/evm/evm_main.c     | 8 ++++----
 security/integrity/ima/ima_appraise.c | 7 ++++---
 security/integrity/integrity.h        | 6 ++++++
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index b6d9f14bc234..588f22f1b5bd 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -169,7 +169,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 	/* check value type */
 	switch (xattr_data->type) {
 	case EVM_XATTR_HMAC:
-		if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
+		if (xattr_len != sizeof(struct evm_xattr)) {
 			evm_status = INTEGRITY_FAIL;
 			goto out;
 		}
@@ -179,7 +179,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 				   xattr_value_len, &digest);
 		if (rc)
 			break;
-		rc = crypto_memneq(xattr_data->digest, digest.digest,
+		rc = crypto_memneq(xattr_data->data, digest.digest,
 				   SHA1_DIGEST_SIZE);
 		if (rc)
 			rc = -EINVAL;
@@ -523,7 +523,7 @@ int evm_inode_init_security(struct inode *inode,
 				 const struct xattr *lsm_xattr,
 				 struct xattr *evm_xattr)
 {
-	struct evm_ima_xattr_data *xattr_data;
+	struct evm_xattr *xattr_data;
 	int rc;
 
 	if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
@@ -533,7 +533,7 @@ int evm_inode_init_security(struct inode *inode,
 	if (!xattr_data)
 		return -ENOMEM;
 
-	xattr_data->type = EVM_XATTR_HMAC;
+	xattr_data->data.type = EVM_XATTR_HMAC;
 	rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
 	if (rc < 0)
 		goto out;
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 5fb7127bbe68..ea8fa29f07d3 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -168,7 +168,8 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
 		return sig->hash_algo;
 		break;
 	case IMA_XATTR_DIGEST_NG:
-		ret = xattr_value->digest[0];
+		/* first byte contains algorithm id */
+		ret = xattr_value->data[0];
 		if (ret < HASH_ALGO__LAST)
 			return ret;
 		break;
@@ -176,7 +177,7 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
 		/* this is for backward compatibility */
 		if (xattr_len == 21) {
 			unsigned int zero = 0;
-			if (!memcmp(&xattr_value->digest[16], &zero, 4))
+			if (!memcmp(&xattr_value->data[16], &zero, 4))
 				return HASH_ALGO_MD5;
 			else
 				return HASH_ALGO_SHA1;
@@ -275,7 +276,7 @@ int ima_appraise_measurement(enum ima_hooks func,
 			/* xattr length may be longer. md5 hash in previous
 			   version occupied 20 bytes in xattr, instead of 16
 			 */
-			rc = memcmp(&xattr_value->digest[hash_start],
+			rc = memcmp(&xattr_value->data[hash_start],
 				    iint->ima_hash->digest,
 				    iint->ima_hash->length);
 		else
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 7de59f44cba3..88a29f72a74f 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -79,6 +79,12 @@ enum evm_ima_xattr_type {
 
 struct evm_ima_xattr_data {
 	u8 type;
+	u8 data[];
+} __packed;
+
+/* Only used in the EVM HMAC code. */
+struct evm_xattr {
+	struct evm_ima_xattr_data data;
 	u8 digest[SHA1_DIGEST_SIZE];
 } __packed;
 


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 05/12] integrity: Select CONFIG_KEYS instead of depending on it
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (3 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 04/12] integrity: Introduce struct evm_xattr Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 06/12] ima: Use designated initializers for struct ima_event_data Thiago Jung Bauermann
                   ` (6 subsequent siblings)
  11 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

This avoids a dependency cycle in soon-to-be-introduced
CONFIG_IMA_APPRAISE_MODSIG: it will select CONFIG_MODULE_SIG_FORMAT
which in turn selects CONFIG_KEYS. Kconfig then complains that
CONFIG_INTEGRITY_SIGNATURE depends on CONFIG_KEYS.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
index 2ea4ec9991d5..bf76f842fcb8 100644
--- a/security/integrity/Kconfig
+++ b/security/integrity/Kconfig
@@ -17,8 +17,8 @@ if INTEGRITY
 
 config INTEGRITY_SIGNATURE
 	bool "Digital signature verification using multiple keyrings"
-	depends on KEYS
 	default n
+	select KEYS
 	select SIGNATURE
 	help
 	  This option enables digital signature verification support


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 06/12] ima: Use designated initializers for struct ima_event_data
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (4 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 05/12] integrity: Select CONFIG_KEYS instead of depending on it Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 15:46   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 07/12] ima: Add modsig appraise_type option for module-style appended signatures Thiago Jung Bauermann
                   ` (5 subsequent siblings)
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Designated initializers allow specifying only the members of the struct
that need initialization. Non-mentioned members are initialized to zero.

This makes the code a bit clearer (particularly in ima_add_boot_aggregate()
and also allows adding a new member to the struct without having to update
all struct initializations.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 security/integrity/ima/ima_api.c  | 11 +++++++----
 security/integrity/ima/ima_init.c |  4 ++--
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index c7505fb122d4..0639d0631f2c 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -133,8 +133,9 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
 {
 	struct ima_template_entry *entry;
 	struct inode *inode = file_inode(file);
-	struct ima_event_data event_data = {iint, file, filename, NULL, 0,
-					    cause};
+	struct ima_event_data event_data = { .iint = iint, .file = file,
+					     .filename = filename,
+					     .violation = cause };
 	int violation = 1;
 	int result;
 
@@ -284,8 +285,10 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
 	int result = -ENOMEM;
 	struct inode *inode = file_inode(file);
 	struct ima_template_entry *entry;
-	struct ima_event_data event_data = {iint, file, filename, xattr_value,
-					    xattr_len, NULL};
+	struct ima_event_data event_data = { .iint = iint, .file = file,
+					     .filename = filename,
+					     .xattr_value = xattr_value,
+					     .xattr_len = xattr_len };
 	int violation = 0;
 
 	if (iint->measured_pcrs & (0x1 << pcr))
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 6c9295449751..ef6c3a26296e 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -49,8 +49,8 @@ static int __init ima_add_boot_aggregate(void)
 	const char *audit_cause = "ENOMEM";
 	struct ima_template_entry *entry;
 	struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
-	struct ima_event_data event_data = {iint, NULL, boot_aggregate_name,
-					    NULL, 0, NULL};
+	struct ima_event_data event_data = { .iint = iint,
+					     .filename = boot_aggregate_name };
 	int result = -ENOMEM;
 	int violation = 0;
 	struct {


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 07/12] ima: Add modsig appraise_type option for module-style appended signatures
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (5 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 06/12] ima: Use designated initializers for struct ima_event_data Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 08/12] ima: Factor xattr_verify() out of ima_appraise_measurement() Thiago Jung Bauermann
                   ` (4 subsequent siblings)
  11 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Introduce the modsig keyword to the IMA policy syntax to specify that
a given hook should expect the file to have the IMA signature appended
to it. Here is how it can be used in a rule:

appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig

With this rule, IMA will accept either a signature stored in the extended
attribute or an appended signature.

For now, the rule above will behave exactly the same as if
appraise_type=imasig was specified. The actual modsig implementation
will be introduced separately.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 Documentation/ABI/testing/ima_policy |  6 +++++-
 security/integrity/ima/Kconfig       | 10 +++++++++
 security/integrity/ima/Makefile      |  1 +
 security/integrity/ima/ima.h         |  9 ++++++++
 security/integrity/ima/ima_modsig.c  | 31 ++++++++++++++++++++++++++++
 security/integrity/ima/ima_policy.c  | 12 +++++++++--
 security/integrity/integrity.h       |  1 +
 7 files changed, 67 insertions(+), 3 deletions(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 74c6702de74e..9d1dfd0a8891 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -37,7 +37,7 @@ Description:
 			euid:= decimal value
 			fowner:= decimal value
 		lsm:  	are LSM specific
-		option:	appraise_type:= [imasig]
+		option:	appraise_type:= [imasig] [imasig|modsig]
 			pcr:= decimal value
 
 		default policy:
@@ -103,3 +103,7 @@ Description:
 
 			measure func=KEXEC_KERNEL_CHECK pcr=4
 			measure func=KEXEC_INITRAMFS_CHECK pcr=5
+
+		Example of appraise rule allowing modsig appended signatures:
+
+			appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index a18f8c6d13b5..bba19f9ea184 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -231,6 +231,16 @@ config IMA_APPRAISE_BOOTPARAM
 	  This option enables the different "ima_appraise=" modes
 	  (eg. fix, log) from the boot command line.
 
+config IMA_APPRAISE_MODSIG
+	bool "Support module-style signatures for appraisal"
+	depends on IMA_APPRAISE
+	default n
+	help
+	   Adds support for signatures appended to files. The format of the
+	   appended signature is the same used for signed kernel modules.
+	   The modsig keyword can be used in the IMA policy to allow a hook
+	   to accept such signatures.
+
 config IMA_TRUSTED_KEYRING
 	bool "Require all keys on the .ima keyring be signed (deprecated)"
 	depends on IMA_APPRAISE && SYSTEM_TRUSTED_KEYRING
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index d921dc4f9eb0..31d57cdf2421 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -9,5 +9,6 @@ obj-$(CONFIG_IMA) += ima.o
 ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
 	 ima_policy.o ima_template.o ima_template_lib.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
+ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
 ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index d213e835c498..0c3e5a59270f 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -293,6 +293,15 @@ static inline int ima_read_xattr(struct dentry *dentry,
 
 #endif /* CONFIG_IMA_APPRAISE */
 
+#ifdef CONFIG_IMA_APPRAISE_MODSIG
+bool ima_hook_supports_modsig(enum ima_hooks func);
+#else
+static inline bool ima_hook_supports_modsig(enum ima_hooks func)
+{
+	return false;
+}
+#endif /* CONFIG_IMA_APPRAISE_MODSIG */
+
 /* LSM based policy rules require audit */
 #ifdef CONFIG_IMA_LSM_RULES
 
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
new file mode 100644
index 000000000000..87503bfe8c8b
--- /dev/null
+++ b/security/integrity/ima/ima_modsig.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * IMA support for appraising module-style appended signatures.
+ *
+ * Copyright (C) 2019  IBM Corporation
+ *
+ * Author:
+ * Thiago Jung Bauermann <bauerman@linux.ibm.com>
+ */
+
+#include "ima.h"
+
+/**
+ * ima_hook_supports_modsig - can the policy allow modsig for this hook?
+ *
+ * modsig is only supported by hooks using ima_post_read_file(), because only
+ * they preload the contents of the file in a buffer. FILE_CHECK does that in
+ * some cases, but not when reached from vfs_open(). POLICY_CHECK can support
+ * it, but it's not useful in practice because it's a text file so deny.
+ */
+bool ima_hook_supports_modsig(enum ima_hooks func)
+{
+	switch (func) {
+	case KEXEC_KERNEL_CHECK:
+	case KEXEC_INITRAMFS_CHECK:
+	case MODULE_CHECK:
+		return true;
+	default:
+		return false;
+	}
+}
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index e0cc323f948f..fca7a3f23321 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1038,6 +1038,10 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 			ima_log_string(ab, "appraise_type", args[0].from);
 			if ((strcmp(args[0].from, "imasig")) == 0)
 				entry->flags |= IMA_DIGSIG_REQUIRED;
+			else if (ima_hook_supports_modsig(entry->func) &&
+				 strcmp(args[0].from, "imasig|modsig") == 0)
+				entry->flags |= IMA_DIGSIG_REQUIRED
+						| IMA_MODSIG_ALLOWED;
 			else
 				result = -EINVAL;
 			break;
@@ -1330,8 +1334,12 @@ int ima_policy_show(struct seq_file *m, void *v)
 			}
 		}
 	}
-	if (entry->flags & IMA_DIGSIG_REQUIRED)
-		seq_puts(m, "appraise_type=imasig ");
+	if (entry->flags & IMA_DIGSIG_REQUIRED) {
+		if (entry->flags & IMA_MODSIG_ALLOWED)
+			seq_puts(m, "appraise_type=imasig|modsig ");
+		else
+			seq_puts(m, "appraise_type=imasig ");
+	}
 	if (entry->flags & IMA_PERMIT_DIRECTIO)
 		seq_puts(m, "permit_directio ");
 	rcu_read_unlock();
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 88a29f72a74f..0e7330a36a9d 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -36,6 +36,7 @@
 #define IMA_NEW_FILE		0x04000000
 #define EVM_IMMUTABLE_DIGSIG	0x08000000
 #define IMA_FAIL_UNVERIFIABLE_SIGS	0x10000000
+#define IMA_MODSIG_ALLOWED	0x20000000
 
 #define IMA_DO_MASK		(IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \
 				 IMA_HASH | IMA_APPRAISE_SUBMASK)


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 08/12] ima: Factor xattr_verify() out of ima_appraise_measurement()
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (6 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 07/12] ima: Add modsig appraise_type option for module-style appended signatures Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 15:53   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 09/12] ima: Implement support for module-style appended signatures Thiago Jung Bauermann
                   ` (3 subsequent siblings)
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Verify xattr signature in a separate function so that the logic in
ima_appraise_measurement() remains clear when it gains the ability to also
verify an appended module signature.

The code in the switch statement is unchanged except for having to
dereference the status and cause variables (since they're now pointers),
and fixing the style of a block comment to appease checkpatch.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 security/integrity/ima/ima_appraise.c | 141 +++++++++++++++-----------
 1 file changed, 81 insertions(+), 60 deletions(-)

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index ea8fa29f07d3..b3837e26bb27 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -202,6 +202,83 @@ int ima_read_xattr(struct dentry *dentry,
 	return ret;
 }
 
+/*
+ * xattr_verify - verify xattr digest or signature
+ *
+ * Verify whether the hash or signature matches the file contents.
+ *
+ * Return 0 on success, error code otherwise.
+ */
+static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
+			struct evm_ima_xattr_data *xattr_value, int xattr_len,
+			enum integrity_status *status, const char **cause)
+{
+	int rc = -EINVAL, hash_start = 0;
+
+	switch (xattr_value->type) {
+	case IMA_XATTR_DIGEST_NG:
+		/* first byte contains algorithm id */
+		hash_start = 1;
+		/* fall through */
+	case IMA_XATTR_DIGEST:
+		if (iint->flags & IMA_DIGSIG_REQUIRED) {
+			*cause = "IMA-signature-required";
+			*status = INTEGRITY_FAIL;
+			break;
+		}
+		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
+		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
+				iint->ima_hash->length)
+			/*
+			 * xattr length may be longer. md5 hash in previous
+			 * version occupied 20 bytes in xattr, instead of 16
+			 */
+			rc = memcmp(&xattr_value->data[hash_start],
+				    iint->ima_hash->digest,
+				    iint->ima_hash->length);
+		else
+			rc = -EINVAL;
+		if (rc) {
+			*cause = "invalid-hash";
+			*status = INTEGRITY_FAIL;
+			break;
+		}
+		*status = INTEGRITY_PASS;
+		break;
+	case EVM_IMA_XATTR_DIGSIG:
+		set_bit(IMA_DIGSIG, &iint->atomic_flags);
+		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
+					     (const char *)xattr_value,
+					     xattr_len,
+					     iint->ima_hash->digest,
+					     iint->ima_hash->length);
+		if (rc == -EOPNOTSUPP) {
+			*status = INTEGRITY_UNKNOWN;
+			break;
+		}
+		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
+		    func == KEXEC_KERNEL_CHECK)
+			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
+						     (const char *)xattr_value,
+						     xattr_len,
+						     iint->ima_hash->digest,
+						     iint->ima_hash->length);
+		if (rc) {
+			*cause = "invalid-signature";
+			*status = INTEGRITY_FAIL;
+		} else {
+			*status = INTEGRITY_PASS;
+		}
+		break;
+	default:
+		*status = INTEGRITY_UNKNOWN;
+		*cause = "unknown-ima-data";
+		break;
+	}
+
+	return rc;
+}
+
 /*
  * ima_appraise_measurement - appraise file measurement
  *
@@ -221,7 +298,7 @@ int ima_appraise_measurement(enum ima_hooks func,
 	struct dentry *dentry = file_dentry(file);
 	struct inode *inode = d_backing_inode(dentry);
 	enum integrity_status status = INTEGRITY_UNKNOWN;
-	int rc = xattr_len, hash_start = 0;
+	int rc = xattr_len;
 
 	if (!(inode->i_opflags & IOP_XATTR))
 		return INTEGRITY_UNKNOWN;
@@ -259,65 +336,9 @@ int ima_appraise_measurement(enum ima_hooks func,
 		WARN_ONCE(true, "Unexpected integrity status %d\n", status);
 	}
 
-	switch (xattr_value->type) {
-	case IMA_XATTR_DIGEST_NG:
-		/* first byte contains algorithm id */
-		hash_start = 1;
-		/* fall through */
-	case IMA_XATTR_DIGEST:
-		if (iint->flags & IMA_DIGSIG_REQUIRED) {
-			cause = "IMA-signature-required";
-			status = INTEGRITY_FAIL;
-			break;
-		}
-		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
-		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
-				iint->ima_hash->length)
-			/* xattr length may be longer. md5 hash in previous
-			   version occupied 20 bytes in xattr, instead of 16
-			 */
-			rc = memcmp(&xattr_value->data[hash_start],
-				    iint->ima_hash->digest,
-				    iint->ima_hash->length);
-		else
-			rc = -EINVAL;
-		if (rc) {
-			cause = "invalid-hash";
-			status = INTEGRITY_FAIL;
-			break;
-		}
-		status = INTEGRITY_PASS;
-		break;
-	case EVM_IMA_XATTR_DIGSIG:
-		set_bit(IMA_DIGSIG, &iint->atomic_flags);
-		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
-					     (const char *)xattr_value,
-					     xattr_len,
-					     iint->ima_hash->digest,
-					     iint->ima_hash->length);
-		if (rc == -EOPNOTSUPP) {
-			status = INTEGRITY_UNKNOWN;
-			break;
-		}
-		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
-		    func == KEXEC_KERNEL_CHECK)
-			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
-						     (const char *)xattr_value,
-						     xattr_len,
-						     iint->ima_hash->digest,
-						     iint->ima_hash->length);
-		if (rc) {
-			cause = "invalid-signature";
-			status = INTEGRITY_FAIL;
-		} else {
-			status = INTEGRITY_PASS;
-		}
-		break;
-	default:
-		status = INTEGRITY_UNKNOWN;
-		cause = "unknown-ima-data";
-		break;
-	}
+	if (xattr_value)
+		rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
+				  &cause);
 
 out:
 	/*


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 09/12] ima: Implement support for module-style appended signatures
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (7 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 08/12] ima: Factor xattr_verify() out of ima_appraise_measurement() Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 23:01   ` Mimi Zohar
  2019-05-14 12:09   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 10/12] ima: Collect modsig Thiago Jung Bauermann
                   ` (2 subsequent siblings)
  11 siblings, 2 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Implement the appraise_type=imasig|modsig option, allowing IMA to read and
verify modsig signatures.

In case a file has both an xattr signature and an appended modsig, IMA will
only use the appended signature if the key used by the xattr signature
isn't present in the IMA or platform keyring.

Because modsig verification needs to convert from an integrity keyring id
to the keyring itself, add an integrity_keyring_from_id() function in
digsig.c so that integrity_modsig_verify() can use it.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/digsig.c           | 39 ++++++++++++---
 security/integrity/ima/Kconfig        |  3 ++
 security/integrity/ima/ima.h          | 22 ++++++++-
 security/integrity/ima/ima_appraise.c | 50 +++++++++++++++++--
 security/integrity/ima/ima_main.c     | 11 ++++-
 security/integrity/ima/ima_modsig.c   | 71 +++++++++++++++++++++++++++
 security/integrity/ima/ima_policy.c   | 12 ++---
 security/integrity/integrity.h        | 19 +++++++
 8 files changed, 206 insertions(+), 21 deletions(-)

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index e19c2eb72c51..ce79d2f6bc7e 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -43,11 +43,10 @@ static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
 #define restrict_link_to_ima restrict_link_by_builtin_trusted
 #endif
 
-int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
-			    const char *digest, int digestlen)
+static struct key *integrity_keyring_from_id(const unsigned int id)
 {
-	if (id >= INTEGRITY_KEYRING_MAX || siglen < 2)
-		return -EINVAL;
+	if (id >= INTEGRITY_KEYRING_MAX)
+		return ERR_PTR(-EINVAL);
 
 	if (!keyring[id]) {
 		keyring[id] =
@@ -56,23 +55,49 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 			int err = PTR_ERR(keyring[id]);
 			pr_err("no %s keyring: %d\n", keyring_name[id], err);
 			keyring[id] = NULL;
-			return err;
+			return ERR_PTR(err);
 		}
 	}
 
+	return keyring[id];
+}
+
+int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
+			    const char *digest, int digestlen)
+{
+	struct key *keyring;
+
+	if (siglen < 2)
+		return -EINVAL;
+
+	keyring = integrity_keyring_from_id(id);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
 	switch (sig[1]) {
 	case 1:
 		/* v1 API expect signature without xattr type */
-		return digsig_verify(keyring[id], sig + 1, siglen - 1,
+		return digsig_verify(keyring, sig + 1, siglen - 1,
 				     digest, digestlen);
 	case 2:
-		return asymmetric_verify(keyring[id], sig, siglen,
+		return asymmetric_verify(keyring, sig, siglen,
 					 digest, digestlen);
 	}
 
 	return -EOPNOTSUPP;
 }
 
+int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
+{
+	struct key *keyring;
+
+	keyring = integrity_keyring_from_id(id);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	return ima_modsig_verify(keyring, modsig);
+}
+
 static int __integrity_init_keyring(const unsigned int id, key_perm_t perm,
 				    struct key_restriction *restriction)
 {
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index bba19f9ea184..0fb542455698 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -234,6 +234,9 @@ config IMA_APPRAISE_BOOTPARAM
 config IMA_APPRAISE_MODSIG
 	bool "Support module-style signatures for appraisal"
 	depends on IMA_APPRAISE
+	depends on INTEGRITY_ASYMMETRIC_KEYS
+	select PKCS7_MESSAGE_PARSER
+	select MODULE_SIG_FORMAT
 	default n
 	help
 	   Adds support for signatures appended to files. The format of the
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 0c3e5a59270f..9f69befd8674 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -191,6 +191,10 @@ enum ima_hooks {
 	__ima_hooks(__ima_hook_enumify)
 };
 
+extern const char *const func_tokens[];
+
+struct modsig;
+
 /* LIM API function definitions */
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
 		   int mask, enum ima_hooks func, int *pcr);
@@ -240,7 +244,7 @@ int ima_appraise_measurement(enum ima_hooks func,
 			     struct integrity_iint_cache *iint,
 			     struct file *file, const unsigned char *filename,
 			     struct evm_ima_xattr_data *xattr_value,
-			     int xattr_len);
+			     int xattr_len, const struct modsig *modsig);
 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func);
 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file);
 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
@@ -256,7 +260,8 @@ static inline int ima_appraise_measurement(enum ima_hooks func,
 					   struct file *file,
 					   const unsigned char *filename,
 					   struct evm_ima_xattr_data *xattr_value,
-					   int xattr_len)
+					   int xattr_len,
+					   const struct modsig *modsig)
 {
 	return INTEGRITY_UNKNOWN;
 }
@@ -295,11 +300,24 @@ static inline int ima_read_xattr(struct dentry *dentry,
 
 #ifdef CONFIG_IMA_APPRAISE_MODSIG
 bool ima_hook_supports_modsig(enum ima_hooks func);
+int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
+		    struct modsig **modsig);
+void ima_free_modsig(struct modsig *modsig);
 #else
 static inline bool ima_hook_supports_modsig(enum ima_hooks func)
 {
 	return false;
 }
+
+static inline int ima_read_modsig(enum ima_hooks func, const void *buf,
+				  loff_t buf_len, struct modsig **modsig)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void ima_free_modsig(struct modsig *modsig)
+{
+}
 #endif /* CONFIG_IMA_APPRAISE_MODSIG */
 
 /* LSM based policy rules require audit */
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index b3837e26bb27..b8cc5897f16a 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -279,6 +279,33 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
 	return rc;
 }
 
+/*
+ * modsig_verify - verify modsig signature
+ *
+ * Verify whether the signature matches the file contents.
+ *
+ * Return 0 on success, error code otherwise.
+ */
+static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
+			 enum integrity_status *status, const char **cause)
+{
+	int rc;
+
+	rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
+	if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
+	    func == KEXEC_KERNEL_CHECK)
+		rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
+					     modsig);
+	if (rc) {
+		*cause = "invalid-signature";
+		*status = INTEGRITY_FAIL;
+	} else {
+		*status = INTEGRITY_PASS;
+	}
+
+	return rc;
+}
+
 /*
  * ima_appraise_measurement - appraise file measurement
  *
@@ -291,7 +318,7 @@ int ima_appraise_measurement(enum ima_hooks func,
 			     struct integrity_iint_cache *iint,
 			     struct file *file, const unsigned char *filename,
 			     struct evm_ima_xattr_data *xattr_value,
-			     int xattr_len)
+			     int xattr_len, const struct modsig *modsig)
 {
 	static const char op[] = "appraise_data";
 	const char *cause = "unknown";
@@ -299,11 +326,14 @@ int ima_appraise_measurement(enum ima_hooks func,
 	struct inode *inode = d_backing_inode(dentry);
 	enum integrity_status status = INTEGRITY_UNKNOWN;
 	int rc = xattr_len;
+	bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
 
-	if (!(inode->i_opflags & IOP_XATTR))
+	/* If not appraising a modsig, we need an xattr. */
+	if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
 		return INTEGRITY_UNKNOWN;
 
-	if (rc <= 0) {
+	/* If reading the xattr failed and there's no modsig, error out. */
+	if (rc <= 0 && !try_modsig) {
 		if (rc && rc != -ENODATA)
 			goto out;
 
@@ -326,6 +356,10 @@ int ima_appraise_measurement(enum ima_hooks func,
 	case INTEGRITY_UNKNOWN:
 		break;
 	case INTEGRITY_NOXATTRS:	/* No EVM protected xattrs. */
+		/* It's fine not to have xattrs when using a modsig. */
+		if (try_modsig)
+			break;
+		/* fall through */
 	case INTEGRITY_NOLABEL:		/* No security.evm xattr. */
 		cause = "missing-HMAC";
 		goto out;
@@ -340,6 +374,14 @@ int ima_appraise_measurement(enum ima_hooks func,
 		rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
 				  &cause);
 
+	/*
+	 * If we have a modsig and either no imasig or the imasig's key isn't
+	 * known, then try verifying the modsig.
+	 */
+	if (status != INTEGRITY_PASS && try_modsig &&
+	    (!xattr_value || rc == -ENOKEY))
+		rc = modsig_verify(func, modsig, &status, &cause);
+
 out:
 	/*
 	 * File signatures on some filesystems can not be properly verified.
@@ -356,7 +398,7 @@ int ima_appraise_measurement(enum ima_hooks func,
 				    op, cause, rc, 0);
 	} else if (status != INTEGRITY_PASS) {
 		/* Fix mode, but don't replace file signatures. */
-		if ((ima_appraise & IMA_APPRAISE_FIX) &&
+		if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig &&
 		    (!xattr_value ||
 		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
 			if (!ima_fix_xattr(dentry, iint))
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 357edd140c09..722d4e9c72ac 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -181,6 +181,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
 	int rc = 0, action, must_appraise = 0;
 	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 	struct evm_ima_xattr_data *xattr_value = NULL;
+	struct modsig *modsig = NULL;
 	int xattr_len = 0;
 	bool violation_check;
 	enum hash_algo hash_algo;
@@ -277,10 +278,15 @@ static int process_measurement(struct file *file, const struct cred *cred,
 
 	template_desc = ima_template_desc_current();
 	if ((action & IMA_APPRAISE_SUBMASK) ||
-		    strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
+	    strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) {
 		/* read 'security.ima' */
 		xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
 
+		/* Read the appended modsig if allowed by the policy. */
+		if (iint->flags & IMA_MODSIG_ALLOWED)
+			ima_read_modsig(func, buf, size, &modsig);
+	}
+
 	hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
 
 	rc = ima_collect_measurement(iint, file, buf, size, hash_algo);
@@ -296,7 +302,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
 	if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
 		inode_lock(inode);
 		rc = ima_appraise_measurement(func, iint, file, pathname,
-					      xattr_value, xattr_len);
+					      xattr_value, xattr_len, modsig);
 		inode_unlock(inode);
 	}
 	if (action & IMA_AUDIT)
@@ -310,6 +316,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
 		rc = -EACCES;
 	mutex_unlock(&iint->mutex);
 	kfree(xattr_value);
+	ima_free_modsig(modsig);
 out:
 	if (pathbuf)
 		__putname(pathbuf);
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index 87503bfe8c8b..ac0f44fb52ce 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -8,8 +8,17 @@
  * Thiago Jung Bauermann <bauerman@linux.ibm.com>
  */
 
+#include <linux/types.h>
+#include <linux/module_signature.h>
+#include <keys/asymmetric-type.h>
+#include <crypto/pkcs7.h>
+
 #include "ima.h"
 
+struct modsig {
+	struct pkcs7_message *pkcs7_msg;
+};
+
 /**
  * ima_hook_supports_modsig - can the policy allow modsig for this hook?
  *
@@ -29,3 +38,65 @@ bool ima_hook_supports_modsig(enum ima_hooks func)
 		return false;
 	}
 }
+
+/*
+ * ima_read_modsig - Read modsig from buf.
+ *
+ * Return: 0 on success, error code otherwise.
+ */
+int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
+		    struct modsig **modsig)
+{
+	const size_t marker_len = strlen(MODULE_SIG_STRING);
+	const struct module_signature *sig;
+	struct modsig *hdr;
+	size_t sig_len;
+	const void *p;
+	int rc;
+
+	if (buf_len <= marker_len + sizeof(*sig))
+		return -ENOENT;
+
+	p = buf + buf_len - marker_len;
+	if (memcmp(p, MODULE_SIG_STRING, marker_len))
+		return -ENOENT;
+
+	buf_len -= marker_len;
+	sig = (const struct module_signature *) (p - sizeof(*sig));
+
+	rc = mod_check_sig(sig, buf_len, func_tokens[func]);
+	if (rc)
+		return rc;
+
+	sig_len = be32_to_cpu(sig->sig_len);
+	buf_len -= sig_len + sizeof(*sig);
+
+	hdr = kmalloc(sizeof(*hdr), GFP_KERNEL);
+	if (!hdr)
+		return -ENOMEM;
+
+	hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
+	if (IS_ERR(hdr->pkcs7_msg)) {
+		kfree(hdr);
+		return PTR_ERR(hdr->pkcs7_msg);
+	}
+
+	*modsig = hdr;
+
+	return 0;
+}
+
+int ima_modsig_verify(struct key *keyring, const struct modsig *modsig)
+{
+	return verify_pkcs7_message_sig(NULL, 0, modsig->pkcs7_msg, keyring,
+					VERIFYING_MODULE_SIGNATURE, NULL, NULL);
+}
+
+void ima_free_modsig(struct modsig *modsig)
+{
+	if (!modsig)
+		return;
+
+	pkcs7_free_message(modsig->pkcs7_msg);
+	kfree(modsig);
+}
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index fca7a3f23321..a7a20a8c15c1 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1144,6 +1144,12 @@ void ima_delete_rules(void)
 	}
 }
 
+#define __ima_hook_stringify(str)	(#str),
+
+const char *const func_tokens[] = {
+	__ima_hooks(__ima_hook_stringify)
+};
+
 #ifdef	CONFIG_IMA_READ_POLICY
 enum {
 	mask_exec = 0, mask_write, mask_read, mask_append
@@ -1156,12 +1162,6 @@ static const char *const mask_tokens[] = {
 	"MAY_APPEND"
 };
 
-#define __ima_hook_stringify(str)	(#str),
-
-static const char *const func_tokens[] = {
-	__ima_hooks(__ima_hook_stringify)
-};
-
 void *ima_policy_start(struct seq_file *m, loff_t *pos)
 {
 	loff_t l = *pos;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 0e7330a36a9d..c6e7f41db470 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -153,10 +153,13 @@ int integrity_kernel_read(struct file *file, loff_t offset,
 
 extern struct dentry *integrity_dir;
 
+struct modsig;
+
 #ifdef CONFIG_INTEGRITY_SIGNATURE
 
 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 			    const char *digest, int digestlen);
+int integrity_modsig_verify(unsigned int id, const struct modsig *modsig);
 
 int __init integrity_init_keyring(const unsigned int id);
 int __init integrity_load_x509(const unsigned int id, const char *path);
@@ -171,6 +174,12 @@ static inline int integrity_digsig_verify(const unsigned int id,
 	return -EOPNOTSUPP;
 }
 
+static inline int integrity_modsig_verify(unsigned int id,
+					  const struct modsig *modsig)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int integrity_init_keyring(const unsigned int id)
 {
 	return 0;
@@ -196,6 +205,16 @@ static inline int asymmetric_verify(struct key *keyring, const char *sig,
 }
 #endif
 
+#ifdef CONFIG_IMA_APPRAISE_MODSIG
+int ima_modsig_verify(struct key *keyring, const struct modsig *modsig);
+#else
+static inline int ima_modsig_verify(struct key *keyring,
+				    const struct modsig *modsig)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 #ifdef CONFIG_IMA_LOAD_X509
 void __init ima_load_x509(void);
 #else


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 10/12] ima: Collect modsig
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (8 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 09/12] ima: Implement support for module-style appended signatures Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 11/12] ima: Define ima-modsig template Thiago Jung Bauermann
  2019-04-18  3:51 ` [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig Thiago Jung Bauermann
  11 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Obtain the modsig and calculate its corresponding hash in
ima_collect_measurement().

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 security/integrity/ima/ima.h          |  8 ++++-
 security/integrity/ima/ima_api.c      |  5 ++-
 security/integrity/ima/ima_appraise.c |  2 +-
 security/integrity/ima/ima_main.c     |  2 +-
 security/integrity/ima/ima_modsig.c   | 50 ++++++++++++++++++++++++++-
 5 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 9f69befd8674..e051477badf4 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -201,7 +201,7 @@ int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
 int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
 int ima_collect_measurement(struct integrity_iint_cache *iint,
 			    struct file *file, void *buf, loff_t size,
-			    enum hash_algo algo);
+			    enum hash_algo algo, struct modsig *modsig);
 void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   const unsigned char *filename,
 			   struct evm_ima_xattr_data *xattr_value,
@@ -302,6 +302,7 @@ static inline int ima_read_xattr(struct dentry *dentry,
 bool ima_hook_supports_modsig(enum ima_hooks func);
 int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 		    struct modsig **modsig);
+void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size);
 void ima_free_modsig(struct modsig *modsig);
 #else
 static inline bool ima_hook_supports_modsig(enum ima_hooks func)
@@ -315,6 +316,11 @@ static inline int ima_read_modsig(enum ima_hooks func, const void *buf,
 	return -EOPNOTSUPP;
 }
 
+static inline void ima_collect_modsig(struct modsig *modsig, const void *buf,
+				      loff_t size)
+{
+}
+
 static inline void ima_free_modsig(struct modsig *modsig)
 {
 }
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 0639d0631f2c..7c01b0a57a5a 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -198,7 +198,7 @@ int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
  */
 int ima_collect_measurement(struct integrity_iint_cache *iint,
 			    struct file *file, void *buf, loff_t size,
-			    enum hash_algo algo)
+			    enum hash_algo algo, struct modsig *modsig)
 {
 	const char *audit_cause = "failed";
 	struct inode *inode = file_inode(file);
@@ -245,6 +245,9 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
 	memcpy(iint->ima_hash, &hash, length);
 	iint->version = i_version;
 
+	if (modsig)
+		ima_collect_modsig(modsig, buf, size);
+
 	/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
 	if (!result)
 		iint->flags |= IMA_COLLECTED;
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index b8cc5897f16a..119034a59627 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -437,7 +437,7 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
 	    !(iint->flags & IMA_HASH))
 		return;
 
-	rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
+	rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL);
 	if (rc < 0)
 		return;
 
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 722d4e9c72ac..b5e44d03a0e3 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -289,7 +289,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
 
 	hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
 
-	rc = ima_collect_measurement(iint, file, buf, size, hash_algo);
+	rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
 	if (rc != 0 && rc != -EBADF && rc != -EINVAL)
 		goto out_locked;
 
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index ac0f44fb52ce..22a49f127437 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -17,6 +17,19 @@
 
 struct modsig {
 	struct pkcs7_message *pkcs7_msg;
+
+	enum hash_algo hash_algo;
+
+	/* This digest will go in the 'd-modsig' field of the IMA template. */
+	const u8 *digest;
+	u32 digest_size;
+
+	/*
+	 * This is what will go to the measurement list if the template requires
+	 * storing the signature.
+	 */
+	int raw_pkcs7_len;
+	u8 raw_pkcs7[];
 };
 
 /**
@@ -71,7 +84,8 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 	sig_len = be32_to_cpu(sig->sig_len);
 	buf_len -= sig_len + sizeof(*sig);
 
-	hdr = kmalloc(sizeof(*hdr), GFP_KERNEL);
+	/* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */
+	hdr = kzalloc(sizeof(*hdr) + sig_len, GFP_KERNEL);
 	if (!hdr)
 		return -ENOMEM;
 
@@ -81,11 +95,45 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 		return PTR_ERR(hdr->pkcs7_msg);
 	}
 
+	memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
+	hdr->raw_pkcs7_len = sig_len;
+
+	/* We don't know the hash algorithm yet. */
+	hdr->hash_algo = HASH_ALGO__LAST;
+
 	*modsig = hdr;
 
 	return 0;
 }
 
+/**
+ * ima_collect_modsig - Calculate the file hash without the appended signature.
+ *
+ * Since the modsig is part of the file contents, the hash used in its signature
+ * isn't the same one ordinarily calculated by IMA. Therefore PKCS7 code
+ * calculates a separate one for signature verification.
+ */
+void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size)
+{
+	int rc;
+
+	/*
+	 * Provide the file contents (minus the appended sig) so that the PKCS7
+	 * code can calculate the file hash.
+	 */
+	size -= modsig->raw_pkcs7_len + strlen(MODULE_SIG_STRING) +
+		sizeof(struct module_signature);
+	rc = pkcs7_supply_detached_data(modsig->pkcs7_msg, buf, size);
+	if (rc)
+		return;
+
+	/* Ask the PKCS7 code to calculate the file hash. */
+	rc = pkcs7_get_digest(modsig->pkcs7_msg, &modsig->digest,
+			      &modsig->digest_size, &modsig->hash_algo);
+	if (rc)
+		return;
+}
+
 int ima_modsig_verify(struct key *keyring, const struct modsig *modsig)
 {
 	return verify_pkcs7_message_sig(NULL, 0, modsig->pkcs7_msg, keyring,


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 11/12] ima: Define ima-modsig template
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (9 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 10/12] ima: Collect modsig Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-09 23:01   ` Mimi Zohar
  2019-04-18  3:51 ` [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig Thiago Jung Bauermann
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

Define new "d-modsig" template field which holds the digest that is
expected to match the one contained in the modsig, and also new "modsig"
template field which holds the appended file signature.

Add a new "ima-modsig" defined template descriptor with the new fields as
well as the ones from the "ima-sig" descriptor.

Change ima_store_measurement() to accept a struct modsig * argument so that
it can be passed along to the templates via struct ima_event_data.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 Documentation/security/IMA-templates.rst  |  7 ++-
 security/integrity/ima/ima.h              | 21 +++++++-
 security/integrity/ima/ima_api.c          |  6 ++-
 security/integrity/ima/ima_main.c         |  2 +-
 security/integrity/ima/ima_modsig.c       | 19 +++++++
 security/integrity/ima/ima_policy.c       | 42 +++++++++++++++-
 security/integrity/ima/ima_template.c     |  7 ++-
 security/integrity/ima/ima_template_lib.c | 60 ++++++++++++++++++++++-
 security/integrity/ima/ima_template_lib.h |  4 ++
 9 files changed, 158 insertions(+), 10 deletions(-)

diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
index 2cd0e273cc9a..8da20b444be0 100644
--- a/Documentation/security/IMA-templates.rst
+++ b/Documentation/security/IMA-templates.rst
@@ -68,15 +68,18 @@ descriptors by adding their identifier to the format string
  - 'd-ng': the digest of the event, calculated with an arbitrary hash
    algorithm (field format: [<hash algo>:]digest, where the digest
    prefix is shown only if the hash algorithm is not SHA1 or MD5);
+ - 'd-modsig': the digest of the event without the appended modsig;
  - 'n-ng': the name of the event, without size limitations;
- - 'sig': the file signature.
+ - 'sig': the file signature;
+ - 'modsig' the appended file signature.
 
 
 Below, there is the list of defined template descriptors:
 
  - "ima": its format is ``d|n``;
  - "ima-ng" (default): its format is ``d-ng|n-ng``;
- - "ima-sig": its format is ``d-ng|n-ng|sig``.
+ - "ima-sig": its format is ``d-ng|n-ng|sig``;
+ - "ima-modsig": its format is ``d-ng|n-ng|sig|d-modsig|modsig``.
 
 
 
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e051477badf4..4e51290b149d 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -64,6 +64,7 @@ struct ima_event_data {
 	const unsigned char *filename;
 	struct evm_ima_xattr_data *xattr_value;
 	int xattr_len;
+	const struct modsig *modsig;
 	const char *violation;
 };
 
@@ -205,7 +206,8 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
 void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   const unsigned char *filename,
 			   struct evm_ima_xattr_data *xattr_value,
-			   int xattr_len, int pcr);
+			   int xattr_len, const struct modsig *modsig,
+			   int pcr);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
 			   const unsigned char *filename);
 int ima_alloc_init_template(struct ima_event_data *event_data,
@@ -303,6 +305,10 @@ bool ima_hook_supports_modsig(enum ima_hooks func);
 int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 		    struct modsig **modsig);
 void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size);
+int ima_get_modsig_digest(const struct modsig *modsig, enum hash_algo *algo,
+			  const u8 **digest, u32 *digest_size);
+int ima_modsig_serialize(const struct modsig *modsig, const void **data,
+			 u32 *data_len);
 void ima_free_modsig(struct modsig *modsig);
 #else
 static inline bool ima_hook_supports_modsig(enum ima_hooks func)
@@ -321,6 +327,19 @@ static inline void ima_collect_modsig(struct modsig *modsig, const void *buf,
 {
 }
 
+static inline int ima_get_modsig_digest(const struct modsig *modsig,
+					enum hash_algo *algo,
+					const u8 **digest, u32 *digest_size)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int ima_modsig_serialize(const struct modsig *modsig,
+				       const void **data, u32 *data_len)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline void ima_free_modsig(struct modsig *modsig)
 {
 }
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 7c01b0a57a5a..3ef48d516f02 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -281,7 +281,8 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
 void ima_store_measurement(struct integrity_iint_cache *iint,
 			   struct file *file, const unsigned char *filename,
 			   struct evm_ima_xattr_data *xattr_value,
-			   int xattr_len, int pcr)
+			   int xattr_len, const struct modsig *modsig,
+			   int pcr)
 {
 	static const char op[] = "add_template_measure";
 	static const char audit_cause[] = "ENOMEM";
@@ -291,7 +292,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
 	struct ima_event_data event_data = { .iint = iint, .file = file,
 					     .filename = filename,
 					     .xattr_value = xattr_value,
-					     .xattr_len = xattr_len };
+					     .xattr_len = xattr_len,
+					     .modsig = modsig };
 	int violation = 0;
 
 	if (iint->measured_pcrs & (0x1 << pcr))
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index b5e44d03a0e3..8e6475854351 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -298,7 +298,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
 
 	if (action & IMA_MEASURE)
 		ima_store_measurement(iint, file, pathname,
-				      xattr_value, xattr_len, pcr);
+				      xattr_value, xattr_len, modsig, pcr);
 	if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
 		inode_lock(inode);
 		rc = ima_appraise_measurement(func, iint, file, pathname,
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index 22a49f127437..3956a40ba60c 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -140,6 +140,25 @@ int ima_modsig_verify(struct key *keyring, const struct modsig *modsig)
 					VERIFYING_MODULE_SIGNATURE, NULL, NULL);
 }
 
+int ima_get_modsig_digest(const struct modsig *modsig, enum hash_algo *algo,
+			  const u8 **digest, u32 *digest_size)
+{
+	*algo = modsig->hash_algo;
+	*digest = modsig->digest;
+	*digest_size = modsig->digest_size;
+
+	return 0;
+}
+
+int ima_modsig_serialize(const struct modsig *modsig, const void **data,
+			 u32 *data_len)
+{
+	*data = &modsig->raw_pkcs7;
+	*data_len = modsig->raw_pkcs7_len;
+
+	return 0;
+}
+
 void ima_free_modsig(struct modsig *modsig)
 {
 	if (!modsig)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index a7a20a8c15c1..65989ffc05b1 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -10,6 +10,9 @@
  *	- initialize default measure policy rules
  *
  */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/fs.h>
@@ -756,6 +759,40 @@ static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
 	ima_log_string_op(ab, key, value, NULL);
 }
 
+/*
+ * Validating the appended signature included in the measurement list requires
+ * the file hash calculated without the appended signature (i.e., the 'd-modsig'
+ * field). Therefore, notify the user if they have the 'modsig' field but not
+ * the 'd-modsig' field in the template.
+ */
+static void check_current_template_modsig(void)
+{
+#define MSG "template with 'modsig' field also needs 'd-modsig' field\n"
+	struct ima_template_desc *template;
+	bool has_modsig, has_dmodsig;
+	static bool checked;
+	int i;
+
+	/* We only need to notify the user once. */
+	if (checked)
+		return;
+
+	has_modsig = has_dmodsig = false;
+	template = ima_template_desc_current();
+	for (i = 0; i < template->num_fields; i++) {
+		if (!strcmp(template->fields[i]->field_id, "modsig"))
+			has_modsig = true;
+		else if (!strcmp(template->fields[i]->field_id, "d-modsig"))
+			has_dmodsig = true;
+	}
+
+	if (has_modsig && !has_dmodsig)
+		pr_notice(MSG);
+
+	checked = true;
+#undef MSG
+}
+
 static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 {
 	struct audit_buffer *ab;
@@ -1039,10 +1076,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 			if ((strcmp(args[0].from, "imasig")) == 0)
 				entry->flags |= IMA_DIGSIG_REQUIRED;
 			else if (ima_hook_supports_modsig(entry->func) &&
-				 strcmp(args[0].from, "imasig|modsig") == 0)
+				 strcmp(args[0].from, "imasig|modsig") == 0) {
 				entry->flags |= IMA_DIGSIG_REQUIRED
 						| IMA_MODSIG_ALLOWED;
-			else
+				check_current_template_modsig();
+			} else
 				result = -EINVAL;
 			break;
 		case Opt_permit_directio:
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index b631b8bc7624..b05a14821a08 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -26,6 +26,7 @@ static struct ima_template_desc builtin_templates[] = {
 	{.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
 	{.name = "ima-ng", .fmt = "d-ng|n-ng"},
 	{.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
+	{.name = "ima-modsig", .fmt = "d-ng|n-ng|sig|d-modsig|modsig"},
 	{.name = "", .fmt = ""},	/* placeholder for a custom format */
 };
 
@@ -43,8 +44,12 @@ static const struct ima_template_field supported_fields[] = {
 	 .field_show = ima_show_template_string},
 	{.field_id = "sig", .field_init = ima_eventsig_init,
 	 .field_show = ima_show_template_sig},
+	{.field_id = "d-modsig", .field_init = ima_eventdigest_modsig_init,
+	 .field_show = ima_show_template_digest_ng},
+	{.field_id = "modsig", .field_init = ima_eventmodsig_init,
+	 .field_show = ima_show_template_sig},
 };
-#define MAX_TEMPLATE_NAME_LEN 15
+#define MAX_TEMPLATE_NAME_LEN sizeof("d|n|d-ng|n-ng|sig|d-modisg|modsig")
 
 static struct ima_template_desc *ima_template;
 static struct ima_template_desc *lookup_template_desc(const char *name);
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 513b457ae900..f549710f58ce 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -223,7 +223,8 @@ int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
 	return 0;
 }
 
-static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
+static int ima_eventdigest_init_common(const u8 *digest, u32 digestsize,
+				       u8 hash_algo,
 				       struct ima_field_data *field_data)
 {
 	/*
@@ -326,6 +327,41 @@ int ima_eventdigest_ng_init(struct ima_event_data *event_data,
 					   hash_algo, field_data);
 }
 
+/*
+ * This function writes the digest of the file which is expected to match the
+ * digest contained in the file's embedded signature.
+ */
+int ima_eventdigest_modsig_init(struct ima_event_data *event_data,
+				struct ima_field_data *field_data)
+{
+	enum hash_algo hash_algo;
+	const u8 *cur_digest;
+	u32 cur_digestsize;
+
+	if (!event_data->modsig)
+		return 0;
+
+	if (event_data->violation) {
+		/* Recording a violation. */
+		hash_algo = HASH_ALGO_SHA1;
+		cur_digest = NULL;
+		cur_digestsize = 0;
+	} else {
+		int rc;
+
+		rc = ima_get_modsig_digest(event_data->modsig, &hash_algo,
+					   &cur_digest, &cur_digestsize);
+		if (rc)
+			return rc;
+		else if (hash_algo == HASH_ALGO__LAST || cur_digestsize == 0)
+			/* There was some error collecting the digest. */
+			return -EINVAL;
+	}
+
+	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
+					   hash_algo, field_data);
+}
+
 static int ima_eventname_init_common(struct ima_event_data *event_data,
 				     struct ima_field_data *field_data,
 				     bool size_limit)
@@ -389,3 +425,25 @@ int ima_eventsig_init(struct ima_event_data *event_data,
 	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
 					     DATA_FMT_HEX, field_data);
 }
+
+int ima_eventmodsig_init(struct ima_event_data *event_data,
+			 struct ima_field_data *field_data)
+{
+	const void *data;
+	u32 data_len;
+	int rc;
+
+	if (!event_data->modsig)
+		return 0;
+
+	/*
+	 * The xattr_value for IMA_MODSIG is a runtime structure containing
+	 * pointers. Get its raw data instead.
+	 */
+	rc = ima_modsig_serialize(event_data->modsig, &data, &data_len);
+	if (rc)
+		return rc;
+
+	return ima_write_template_field_data(data, data_len,
+					     DATA_FMT_HEX, field_data);
+}
diff --git a/security/integrity/ima/ima_template_lib.h b/security/integrity/ima/ima_template_lib.h
index 6a3d8b831deb..1d7c690ebae5 100644
--- a/security/integrity/ima/ima_template_lib.h
+++ b/security/integrity/ima/ima_template_lib.h
@@ -38,8 +38,12 @@ int ima_eventname_init(struct ima_event_data *event_data,
 		       struct ima_field_data *field_data);
 int ima_eventdigest_ng_init(struct ima_event_data *event_data,
 			    struct ima_field_data *field_data);
+int ima_eventdigest_modsig_init(struct ima_event_data *event_data,
+				struct ima_field_data *field_data);
 int ima_eventname_ng_init(struct ima_event_data *event_data,
 			  struct ima_field_data *field_data);
 int ima_eventsig_init(struct ima_event_data *event_data,
 		      struct ima_field_data *field_data);
+int ima_eventmodsig_init(struct ima_event_data *event_data,
+			 struct ima_field_data *field_data);
 #endif /* __LINUX_IMA_TEMPLATE_LIB_H */


^ permalink raw reply	[flat|nested] 28+ messages in thread

* [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig
  2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
                   ` (10 preceding siblings ...)
  2019-04-18  3:51 ` [PATCH v10 11/12] ima: Define ima-modsig template Thiago Jung Bauermann
@ 2019-04-18  3:51 ` Thiago Jung Bauermann
  2019-05-28 14:09   ` Mimi Zohar
  11 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-04-18  3:51 UTC (permalink / raw)
  To: linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Mimi Zohar, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro, Thiago Jung Bauermann

If the IMA template contains the "modsig" or "d-modsig" field, then the
modsig should be added to the measurement list when the file is appraised.

And that is what normally happens, but if a measurement rule caused a file
containing a modsig to be measured before a different rule causes it to be
appraised, the resulting measurement entry will not contain the modsig
because it is only fetched during appraisal. When the appraisal rule
triggers, it won't store a new measurement containing the modsig because
the file was already measured.

We need to detect that situation and store an additional measurement with
the modsig. This is done by adding an IMA_MEASURE action flag if we read a
modsig and the IMA template contains a modsig field.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 security/integrity/ima/ima.h          |  1 +
 security/integrity/ima/ima_api.c      | 19 +++++++++++++++----
 security/integrity/ima/ima_main.c     | 14 +++++++++++---
 security/integrity/ima/ima_template.c | 24 ++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 7 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 4e51290b149d..4e504c011b69 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -148,6 +148,7 @@ int ima_init_crypto(void);
 void ima_putc(struct seq_file *m, void *data, int datalen);
 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
 struct ima_template_desc *ima_template_desc_current(void);
+bool ima_template_has_modsig(void);
 int ima_restore_measurement_entry(struct ima_template_entry *entry);
 int ima_restore_measurement_list(loff_t bufsize, void *buf);
 int ima_measurements_show(struct seq_file *m, void *v);
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 3ef48d516f02..663805887fac 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -212,6 +212,14 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
 		char digest[IMA_MAX_DIGEST_SIZE];
 	} hash;
 
+	/*
+	 * Always collect the modsig, because IMA might have already collected
+	 * the file digest without collecting the modsig in a previous
+	 * measurement rule.
+	 */
+	if (modsig)
+		ima_collect_modsig(modsig, buf, size);
+
 	if (iint->flags & IMA_COLLECTED)
 		goto out;
 
@@ -245,9 +253,6 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
 	memcpy(iint->ima_hash, &hash, length);
 	iint->version = i_version;
 
-	if (modsig)
-		ima_collect_modsig(modsig, buf, size);
-
 	/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
 	if (!result)
 		iint->flags |= IMA_COLLECTED;
@@ -296,7 +301,13 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
 					     .modsig = modsig };
 	int violation = 0;
 
-	if (iint->measured_pcrs & (0x1 << pcr))
+	/*
+	 * We still need to store the measurement in the case of MODSIG because
+	 * we only have its contents to put in the list at the time of
+	 * appraisal, but a file measurement from earlier might already exist in
+	 * the measurement list.
+	 */
+	if (iint->measured_pcrs & (0x1 << pcr) && !modsig)
 		return;
 
 	result = ima_alloc_init_template(&event_data, &entry);
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 8e6475854351..f91ed4189f98 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -282,9 +282,17 @@ static int process_measurement(struct file *file, const struct cred *cred,
 		/* read 'security.ima' */
 		xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
 
-		/* Read the appended modsig if allowed by the policy. */
-		if (iint->flags & IMA_MODSIG_ALLOWED)
-			ima_read_modsig(func, buf, size, &modsig);
+		/*
+		 * Read the appended modsig, if allowed by the policy, and allow
+		 * an additional measurement list entry, if needed, based on the
+		 * template format.
+		 */
+		if (iint->flags & IMA_MODSIG_ALLOWED) {
+			rc = ima_read_modsig(func, buf, size, &modsig);
+
+			if (!rc && ima_template_has_modsig())
+				action |= IMA_MEASURE;
+		}
 	}
 
 	hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index b05a14821a08..db3b4257e58b 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -57,6 +57,26 @@ static int template_desc_init_fields(const char *template_fmt,
 				     const struct ima_template_field ***fields,
 				     int *num_fields);
 
+/* Whether the current template has fields referencing a file's signature. */
+static bool template_has_modsig;
+
+static bool find_modsig_in_template(void)
+{
+	int i;
+
+	for (i = 0; i < ima_template->num_fields; i++)
+		if (!strcmp(ima_template->fields[i]->field_id, "modsig") ||
+		    !strcmp(ima_template->fields[i]->field_id, "d-modsig"))
+			return true;
+
+	return false;
+}
+
+bool ima_template_has_modsig(void)
+{
+	return template_has_modsig;
+}
+
 static int __init ima_template_setup(char *str)
 {
 	struct ima_template_desc *template_desc;
@@ -89,6 +109,8 @@ static int __init ima_template_setup(char *str)
 	}
 
 	ima_template = template_desc;
+	template_has_modsig = find_modsig_in_template();
+
 	return 1;
 }
 __setup("ima_template=", ima_template_setup);
@@ -108,6 +130,7 @@ static int __init ima_template_fmt_setup(char *str)
 
 	builtin_templates[num_templates - 1].fmt = str;
 	ima_template = builtin_templates + num_templates - 1;
+	template_has_modsig = find_modsig_in_template();
 
 	return 1;
 }
@@ -230,6 +253,7 @@ struct ima_template_desc *ima_template_desc_current(void)
 		ima_init_template_list();
 		ima_template =
 		    lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
+		template_has_modsig = find_modsig_in_template();
 	}
 	return ima_template;
 }


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 01/12] MODSIGN: Export module signature definitions
  2019-04-18  3:51 ` [PATCH v10 01/12] MODSIGN: Export module signature definitions Thiago Jung Bauermann
@ 2019-05-09 15:42   ` Mimi Zohar
  2019-05-28 19:03     ` Thiago Jung Bauermann
  0 siblings, 1 reply; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 15:42 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> IMA will use the module_signature format for append signatures, so export
> the relevant definitions and factor out the code which verifies that the
> appended signature trailer is valid.
> 
> Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
> and be able to use mod_check_sig() without having to depend on either
> CONFIG_MODULE_SIG or CONFIG_MODULES.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Cc: Jessica Yu <jeyu@kernel.org>

Just a couple minor questions/comments below.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

> ---

< snip >


> diff --git a/init/Kconfig b/init/Kconfig
> index 4592bf7997c0..a71019553ee1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
>  config MODULE_SIG
>  	bool "Module signature verification"
>  	depends on MODULES
> -	select SYSTEM_DATA_VERIFICATION
> +	select MODULE_SIG_FORMAT
>  	help
>  	  Check modules for valid signatures upon load: the signature
>  	  is simply appended to the module. For more information see
> @@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
>  
>  endif # MODULES
>  
> +config MODULE_SIG_FORMAT
> +	def_bool n
> +	select SYSTEM_DATA_VERIFICATION

Normally Kconfigs, in the same file, are defined before they are used.
 I'm not sure if that is required or just a convention.


>  config MODULES_TREE_LOOKUP
>  	def_bool y
>  	depends on PERF_EVENTS || TRACING
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 6c57e78817da..d2f2488f80ab 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -57,6 +57,7 @@ endif
>  obj-$(CONFIG_UID16) += uid16.o
>  obj-$(CONFIG_MODULES) += module.o
>  obj-$(CONFIG_MODULE_SIG) += module_signing.o
> +obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
>  obj-$(CONFIG_KALLSYMS) += kallsyms.o
>  obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
>  obj-$(CONFIG_CRASH_CORE) += crash_core.o
> diff --git a/kernel/module.c b/kernel/module.c
> index 985caa467aef..326ddeb364dd 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -19,6 +19,7 @@
>  #include <linux/export.h>
>  #include <linux/extable.h>
>  #include <linux/moduleloader.h>
> +#include <linux/module_signature.h>
>  #include <linux/trace_events.h>
>  #include <linux/init.h>
>  #include <linux/kallsyms.h>
> diff --git a/kernel/module_signature.c b/kernel/module_signature.c
> new file mode 100644
> index 000000000000..6d5e59f27f55
> --- /dev/null
> +++ b/kernel/module_signature.c
> @@ -0,0 +1,45 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Module signature checker
> + *
> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
> + * Written by David Howells (dhowells@redhat.com)
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/printk.h>
> +#include <linux/module_signature.h>
> +#include <asm/byteorder.h>
> +
> +/**
> + * mod_check_sig - check that the given signature is sane
> + *
> + * @ms:		Signature to check.
> + * @file_len:	Size of the file to which @ms is appended.

"name" is missing.

Mimi

> + */


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 03/12] PKCS#7: Introduce pkcs7_get_digest()
  2019-04-18  3:51 ` [PATCH v10 03/12] PKCS#7: Introduce pkcs7_get_digest() Thiago Jung Bauermann
@ 2019-05-09 15:42   ` Mimi Zohar
  0 siblings, 0 replies; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 15:42 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> IMA will need to access the digest of the PKCS7 message (as calculated by
> the kernel) before the signature is verified, so introduce
> pkcs7_get_digest() for that purpose.
> 
> Also, modify pkcs7_digest() to detect when the digest was already
> calculated so that it doesn't have to do redundant work. Verifying that
> sinfo->sig->digest isn't NULL is sufficient because both places which
> allocate sinfo->sig (pkcs7_parse_message() and pkcs7_note_signed_info())
> use kzalloc() so sig->digest is always initialized to zero.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: "David S. Miller" <davem@davemloft.net>

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 02/12] PKCS#7: Refactor verify_pkcs7_signature()
  2019-04-18  3:51 ` [PATCH v10 02/12] PKCS#7: Refactor verify_pkcs7_signature() Thiago Jung Bauermann
@ 2019-05-09 15:42   ` Mimi Zohar
  0 siblings, 0 replies; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 15:42 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> IMA will need to verify a PKCS#7 signature which has already been parsed.
> For this reason, factor out the code which does that from
> verify_pkcs7_signature() into a new function which takes a struct
> pkcs7_message instead of a data buffer.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Cc: David Howells <dhowells@redhat.com>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: "David S. Miller" <davem@davemloft.net>

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 06/12] ima: Use designated initializers for struct ima_event_data
  2019-04-18  3:51 ` [PATCH v10 06/12] ima: Use designated initializers for struct ima_event_data Thiago Jung Bauermann
@ 2019-05-09 15:46   ` Mimi Zohar
  0 siblings, 0 replies; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 15:46 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> Designated initializers allow specifying only the members of the struct
> that need initialization. Non-mentioned members are initialized to zero.
> 
> This makes the code a bit clearer (particularly in ima_add_boot_aggregate()
> and also allows adding a new member to the struct without having to update
> all struct initializations.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

Reviewed-by:  Mimi Zohar <zohar@linux.ibm.com>

> ---
>  security/integrity/ima/ima_api.c  | 11 +++++++----
>  security/integrity/ima/ima_init.c |  4 ++--
>  2 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index c7505fb122d4..0639d0631f2c 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -133,8 +133,9 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>  {
>  	struct ima_template_entry *entry;
>  	struct inode *inode = file_inode(file);
> -	struct ima_event_data event_data = {iint, file, filename, NULL, 0,
> -					    cause};
> +	struct ima_event_data event_data = { .iint = iint, .file = file,
> +					     .filename = filename,
> +					     .violation = cause };
>  	int violation = 1;
>  	int result;
>  
> @@ -284,8 +285,10 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
>  	int result = -ENOMEM;
>  	struct inode *inode = file_inode(file);
>  	struct ima_template_entry *entry;
> -	struct ima_event_data event_data = {iint, file, filename, xattr_value,
> -					    xattr_len, NULL};
> +	struct ima_event_data event_data = { .iint = iint, .file = file,
> +					     .filename = filename,
> +					     .xattr_value = xattr_value,
> +					     .xattr_len = xattr_len };
>  	int violation = 0;
>  
>  	if (iint->measured_pcrs & (0x1 << pcr))
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 6c9295449751..ef6c3a26296e 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -49,8 +49,8 @@ static int __init ima_add_boot_aggregate(void)
>  	const char *audit_cause = "ENOMEM";
>  	struct ima_template_entry *entry;
>  	struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
> -	struct ima_event_data event_data = {iint, NULL, boot_aggregate_name,
> -					    NULL, 0, NULL};
> +	struct ima_event_data event_data = { .iint = iint,
> +					     .filename = boot_aggregate_name };
>  	int result = -ENOMEM;
>  	int violation = 0;
>  	struct {


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 08/12] ima: Factor xattr_verify() out of ima_appraise_measurement()
  2019-04-18  3:51 ` [PATCH v10 08/12] ima: Factor xattr_verify() out of ima_appraise_measurement() Thiago Jung Bauermann
@ 2019-05-09 15:53   ` Mimi Zohar
  0 siblings, 0 replies; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 15:53 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> Verify xattr signature in a separate function so that the logic in
> ima_appraise_measurement() remains clear when it gains the ability to also
> verify an appended module signature.
> 
> The code in the switch statement is unchanged except for having to
> dereference the status and cause variables (since they're now pointers),
> and fixing the style of a block comment to appease checkpatch.
> 
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

Reviewed-by:  Mimi Zohar <zohar@linux.ibm.com>


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 09/12] ima: Implement support for module-style appended signatures
  2019-04-18  3:51 ` [PATCH v10 09/12] ima: Implement support for module-style appended signatures Thiago Jung Bauermann
@ 2019-05-09 23:01   ` Mimi Zohar
  2019-05-28 19:23     ` Thiago Jung Bauermann
  2019-05-14 12:09   ` Mimi Zohar
  1 sibling, 1 reply; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 23:01 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

Hi Thiago,

> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index fca7a3f23321..a7a20a8c15c1 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1144,6 +1144,12 @@ void ima_delete_rules(void)
>  	}
>  }
>  
> +#define __ima_hook_stringify(str)	(#str),
> +
> +const char *const func_tokens[] = {
> +	__ima_hooks(__ima_hook_stringify)
> +};
> +
>  #ifdef	CONFIG_IMA_READ_POLICY
>  enum {
>  	mask_exec = 0, mask_write, mask_read, mask_append
> @@ -1156,12 +1162,6 @@ static const char *const mask_tokens[] = {
>  	"MAY_APPEND"
>  };
>  
> -#define __ima_hook_stringify(str)	(#str),
> -
> -static const char *const func_tokens[] = {
> -	__ima_hooks(__ima_hook_stringify)
> -};
> -
>  void *ima_policy_start(struct seq_file *m, loff_t *pos)
>  {
>  	loff_t l = *pos;

Is moving this something left over from previous versions or there is
a need for this change?

Other than this, the patch looks good.

Mimi


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 11/12] ima: Define ima-modsig template
  2019-04-18  3:51 ` [PATCH v10 11/12] ima: Define ima-modsig template Thiago Jung Bauermann
@ 2019-05-09 23:01   ` Mimi Zohar
  2019-05-28 19:09     ` Thiago Jung Bauermann
  0 siblings, 1 reply; 28+ messages in thread
From: Mimi Zohar @ 2019-05-09 23:01 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> Define new "d-modsig" template field which holds the digest that is
> expected to match the one contained in the modsig, and also new "modsig"
> template field which holds the appended file signature.
> 
> Add a new "ima-modsig" defined template descriptor with the new fields as
> well as the ones from the "ima-sig" descriptor.
> 
> Change ima_store_measurement() to accept a struct modsig * argument so that
> it can be passed along to the templates via struct ima_event_data.
> 
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

Thanks, Roberto.  Just some thoughts inline below.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

> ---

<snip>

> +/*
> + * Validating the appended signature included in the measurement list requires
> + * the file hash calculated without the appended signature (i.e., the 'd-modsig'
> + * field). Therefore, notify the user if they have the 'modsig' field but not
> + * the 'd-modsig' field in the template.
> + */
> +static void check_current_template_modsig(void)
> +{
> +#define MSG "template with 'modsig' field also needs 'd-modsig' field\n"
> +	struct ima_template_desc *template;
> +	bool has_modsig, has_dmodsig;
> +	static bool checked;
> +	int i;
> +
> +	/* We only need to notify the user once. */
> +	if (checked)
> +		return;
> +
> +	has_modsig = has_dmodsig = false;
> +	template = ima_template_desc_current();
> +	for (i = 0; i < template->num_fields; i++) {
> +		if (!strcmp(template->fields[i]->field_id, "modsig"))
> +			has_modsig = true;
> +		else if (!strcmp(template->fields[i]->field_id, "d-modsig"))
> +			has_dmodsig = true;
> +	}
> +
> +	if (has_modsig && !has_dmodsig)
> +		pr_notice(MSG);
> +
> +	checked = true;
> +#undef MSG
> +}
> +

There was some recent discussion about supporting per IMA policy rule
template formats.  This feature will allow just the kexec kernel image
to require ima-modsig.  When per policy rule template formats support
is upstreamed, this function will need to be updated.

<snip>
> 
> @@ -389,3 +425,25 @@ int ima_eventsig_init(struct ima_event_data *event_data,
>  	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
>  					     DATA_FMT_HEX, field_data);
>  }
> +
> +int ima_eventmodsig_init(struct ima_event_data *event_data,
> +			 struct ima_field_data *field_data)
> +{
> +	const void *data;
> +	u32 data_len;
> +	int rc;
> +
> +	if (!event_data->modsig)
> +		return 0;
> +
> +	/*
> +	 * The xattr_value for IMA_MODSIG is a runtime structure containing
> +	 * pointers. Get its raw data instead.
> +	 */

"xattr_value"?  The comment needs some clarification.

Mimi

> +	rc = ima_modsig_serialize(event_data->modsig, &data, &data_len);
> +	if (rc)
> +		return rc;
> +
> +	return ima_write_template_field_data(data, data_len,
> +					     DATA_FMT_HEX, field_data);
> +}


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 09/12] ima: Implement support for module-style appended signatures
  2019-04-18  3:51 ` [PATCH v10 09/12] ima: Implement support for module-style appended signatures Thiago Jung Bauermann
  2019-05-09 23:01   ` Mimi Zohar
@ 2019-05-14 12:09   ` Mimi Zohar
  2019-05-28 19:27     ` Thiago Jung Bauermann
  1 sibling, 1 reply; 28+ messages in thread
From: Mimi Zohar @ 2019-05-14 12:09 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

Hi Thiago,

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> 
> @@ -326,6 +356,10 @@ int ima_appraise_measurement(enum ima_hooks func,
>         case INTEGRITY_UNKNOWN:
>                 break;
>         case INTEGRITY_NOXATTRS:        /* No EVM protected xattrs. */
> +               /* It's fine not to have xattrs when using a modsig. */
> +               if (try_modsig)
> +                       break;
> +               /* fall through */
>         case INTEGRITY_NOLABEL:         /* No security.evm xattr. */
>                 cause = "missing-HMAC";
>                 goto out;
> @@ -340,6 +374,14 @@ int ima_appraise_measurement(enum ima_hooks func,
>                 rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
>                                   &cause);
>  
> +       /*
> +        * If we have a modsig and either no imasig or the imasig's key isn't
> +        * known, then try verifying the modsig.
> +        */
> +       if (status != INTEGRITY_PASS && try_modsig &&
> +           (!xattr_value || rc == -ENOKEY))
> +               rc = modsig_verify(func, modsig, &status, &cause);

EVM protects other security xattrs, not just security.ima, if they
exist.  As a result, evm_verifyxattr() could pass based on the other
security xattrs.

Mimi

> +
>  out:
>         /*
>          * File signatures on some filesystems can not be properly verified.


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig
  2019-04-18  3:51 ` [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig Thiago Jung Bauermann
@ 2019-05-28 14:09   ` Mimi Zohar
  2019-05-28 19:14     ` Thiago Jung Bauermann
  0 siblings, 1 reply; 28+ messages in thread
From: Mimi Zohar @ 2019-05-28 14:09 UTC (permalink / raw)
  To: Thiago Jung Bauermann, linux-integrity
  Cc: linux-security-module, keyrings, linux-crypto, linuxppc-dev,
	linux-doc, linux-kernel, Dmitry Kasatkin, James Morris,
	Serge E. Hallyn, David Howells, David Woodhouse, Jessica Yu,
	Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI, Takahiro

Hi Thiago,

On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> If the IMA template contains the "modsig" or "d-modsig" field, then the
> modsig should be added to the measurement list when the file is appraised.
> 
> And that is what normally happens, but if a measurement rule caused a file
> containing a modsig to be measured before a different rule causes it to be
> appraised, the resulting measurement entry will not contain the modsig
> because it is only fetched during appraisal. When the appraisal rule
> triggers, it won't store a new measurement containing the modsig because
> the file was already measured.
> 
> We need to detect that situation and store an additional measurement with
> the modsig. This is done by adding an IMA_MEASURE action flag if we read a
> modsig and the IMA template contains a modsig field.

With the new per policy rule "template" support being added, this
patch needs to be modified so that the per policy "template" format is
checked.  ima_template_has_modsig() should be called with the
template_desc being used.

thanks,

Mimi


> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 8e6475854351..f91ed4189f98 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -282,9 +282,17 @@ static int process_measurement(struct file *file, const struct cred *cred,
>  		/* read 'security.ima' */
>  		xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
>  
> -		/* Read the appended modsig if allowed by the policy. */
> -		if (iint->flags & IMA_MODSIG_ALLOWED)
> -			ima_read_modsig(func, buf, size, &modsig);
> +		/*
> +		 * Read the appended modsig, if allowed by the policy, and allow
> +		 * an additional measurement list entry, if needed, based on the
> +		 * template format.
> +		 */
> +		if (iint->flags & IMA_MODSIG_ALLOWED) {
> +			rc = ima_read_modsig(func, buf, size, &modsig);
> +
> +			if (!rc && ima_template_has_modsig())
> +				action |= IMA_MEASURE;
> +		}
> 


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 01/12] MODSIGN: Export module signature definitions
  2019-05-09 15:42   ` Mimi Zohar
@ 2019-05-28 19:03     ` Thiago Jung Bauermann
  0 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-05-28 19:03 UTC (permalink / raw)
  To: Mimi Zohar
  Cc: linux-integrity, linux-security-module, keyrings, linux-crypto,
	linuxppc-dev, linux-doc, linux-kernel, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI\,
	Takahiro


Mimi Zohar <zohar@linux.ibm.com> writes:

> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> IMA will use the module_signature format for append signatures, so export
>> the relevant definitions and factor out the code which verifies that the
>> appended signature trailer is valid.
>> 
>> Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
>> and be able to use mod_check_sig() without having to depend on either
>> CONFIG_MODULE_SIG or CONFIG_MODULES.
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>> Cc: Jessica Yu <jeyu@kernel.org>
>
> Just a couple minor questions/comments below.
>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Thanks for your review and your comments!

>> diff --git a/init/Kconfig b/init/Kconfig
>> index 4592bf7997c0..a71019553ee1 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
>>  config MODULE_SIG
>>  	bool "Module signature verification"
>>  	depends on MODULES
>> -	select SYSTEM_DATA_VERIFICATION
>> +	select MODULE_SIG_FORMAT
>>  	help
>>  	  Check modules for valid signatures upon load: the signature
>>  	  is simply appended to the module. For more information see
>> @@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
>>  
>>  endif # MODULES
>>  
>> +config MODULE_SIG_FORMAT
>> +	def_bool n
>> +	select SYSTEM_DATA_VERIFICATION
>
> Normally Kconfigs, in the same file, are defined before they are used.
>  I'm not sure if that is required or just a convention.

I think it's a convention, because it seemed to work in the current way.
For the next version I moved the config MODULE_SIG_FORMAT definition to
just before "menuconfig MODULES"

>> diff --git a/kernel/module_signature.c b/kernel/module_signature.c
>> new file mode 100644
>> index 000000000000..6d5e59f27f55
>> --- /dev/null
>> +++ b/kernel/module_signature.c
>> @@ -0,0 +1,45 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * Module signature checker
>> + *
>> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
>> + * Written by David Howells (dhowells@redhat.com)
>> + */
>> +
>> +#include <linux/errno.h>
>> +#include <linux/printk.h>
>> +#include <linux/module_signature.h>
>> +#include <asm/byteorder.h>
>> +
>> +/**
>> + * mod_check_sig - check that the given signature is sane
>> + *
>> + * @ms:		Signature to check.
>> + * @file_len:	Size of the file to which @ms is appended.
>
> "name" is missing.

Fixed.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 11/12] ima: Define ima-modsig template
  2019-05-09 23:01   ` Mimi Zohar
@ 2019-05-28 19:09     ` Thiago Jung Bauermann
  0 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-05-28 19:09 UTC (permalink / raw)
  To: Mimi Zohar
  Cc: linux-integrity, linux-security-module, keyrings, linux-crypto,
	linuxppc-dev, linux-doc, linux-kernel, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI\,
	Takahiro


Mimi Zohar <zohar@linux.ibm.com> writes:

> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> Define new "d-modsig" template field which holds the digest that is
>> expected to match the one contained in the modsig, and also new "modsig"
>> template field which holds the appended file signature.
>>
>> Add a new "ima-modsig" defined template descriptor with the new fields as
>> well as the ones from the "ima-sig" descriptor.
>>
>> Change ima_store_measurement() to accept a struct modsig * argument so that
>> it can be passed along to the templates via struct ima_event_data.
>>
>> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>
> Thanks, Roberto. Just some thoughts inline below.
>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Thanks!

>> +/*
>> + * Validating the appended signature included in the measurement list requires
>> + * the file hash calculated without the appended signature (i.e., the 'd-modsig'
>> + * field). Therefore, notify the user if they have the 'modsig' field but not
>> + * the 'd-modsig' field in the template.
>> + */
>> +static void check_current_template_modsig(void)
>> +{
>> +#define MSG "template with 'modsig' field also needs 'd-modsig' field\n"
>> +	struct ima_template_desc *template;
>> +	bool has_modsig, has_dmodsig;
>> +	static bool checked;
>> +	int i;
>> +
>> +	/* We only need to notify the user once. */
>> +	if (checked)
>> +		return;
>> +
>> +	has_modsig = has_dmodsig = false;
>> +	template = ima_template_desc_current();
>> +	for (i = 0; i < template->num_fields; i++) {
>> +		if (!strcmp(template->fields[i]->field_id, "modsig"))
>> +			has_modsig = true;
>> +		else if (!strcmp(template->fields[i]->field_id, "d-modsig"))
>> +			has_dmodsig = true;
>> +	}
>> +
>> +	if (has_modsig && !has_dmodsig)
>> +		pr_notice(MSG);
>> +
>> +	checked = true;
>> +#undef MSG
>> +}
>> +
>
> There was some recent discussion about supporting per IMA policy rule
> template formats. This feature will allow just the kexec kernel image
> to require ima-modsig. When per policy rule template formats support
> is upstreamed, this function will need to be updated.

Indeed. Thanks for the clarification. For the next iteration I rebased
on top of Matthew Garret's "IMA: Allow profiles to define the desired
IMA template" patch. I'm currently adapting this check accordingly.

>> @@ -389,3 +425,25 @@ int ima_eventsig_init(struct ima_event_data *event_data,
>>  	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
>>  					     DATA_FMT_HEX, field_data);
>>  }
>> +
>> +int ima_eventmodsig_init(struct ima_event_data *event_data,
>> +			 struct ima_field_data *field_data)
>> +{
>> +	const void *data;
>> +	u32 data_len;
>> +	int rc;
>> +
>> +	if (!event_data->modsig)
>> +		return 0;
>> +
>> +	/*
>> +	 * The xattr_value for IMA_MODSIG is a runtime structure containing
>> +	 * pointers. Get its raw data instead.
>> +	 */
>
> "xattr_value"? The comment needs some clarification.

Oops, forgot to update this comment. This is the new version:

	/*
	 * modsig is a runtime structure containing pointers. Get its raw data
	 * instead.
	 */

--
Thiago Jung Bauermann
IBM Linux Technology Center


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig
  2019-05-28 14:09   ` Mimi Zohar
@ 2019-05-28 19:14     ` Thiago Jung Bauermann
  0 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-05-28 19:14 UTC (permalink / raw)
  To: Mimi Zohar
  Cc: linux-integrity, linux-security-module, keyrings, linux-crypto,
	linuxppc-dev, linux-doc, linux-kernel, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI\,
	Takahiro


Mimi Zohar <zohar@linux.ibm.com> writes:

> Hi Thiago,
>
> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> If the IMA template contains the "modsig" or "d-modsig" field, then the
>> modsig should be added to the measurement list when the file is appraised.
>>
>> And that is what normally happens, but if a measurement rule caused a file
>> containing a modsig to be measured before a different rule causes it to be
>> appraised, the resulting measurement entry will not contain the modsig
>> because it is only fetched during appraisal. When the appraisal rule
>> triggers, it won't store a new measurement containing the modsig because
>> the file was already measured.
>>
>> We need to detect that situation and store an additional measurement with
>> the modsig. This is done by adding an IMA_MEASURE action flag if we read a
>> modsig and the IMA template contains a modsig field.
>
> With the new per policy rule "template" support being added, this
> patch needs to be modified so that the per policy "template" format is
> checked. ima_template_has_modsig() should be called with the
> template_desc being used.

Right. Thanks for point out what needs to be done. After rebasing on top
of Matthew Garret's "IMA: Allow profiles to define the desired IMA
template" patch I changed ima_template_has_modsig() to check the
template_desc obtained from process_measurement().

--
Thiago Jung Bauermann
IBM Linux Technology Center


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 09/12] ima: Implement support for module-style appended signatures
  2019-05-09 23:01   ` Mimi Zohar
@ 2019-05-28 19:23     ` Thiago Jung Bauermann
  2019-05-28 20:06       ` Mimi Zohar
  0 siblings, 1 reply; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-05-28 19:23 UTC (permalink / raw)
  To: Mimi Zohar
  Cc: linux-integrity, linux-security-module, keyrings, linux-crypto,
	linuxppc-dev, linux-doc, linux-kernel, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI\,
	Takahiro


Mimi Zohar <zohar@linux.ibm.com> writes:

> Hi Thiago,
>
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index fca7a3f23321..a7a20a8c15c1 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -1144,6 +1144,12 @@ void ima_delete_rules(void)
>>  	}
>>  }
>>
>> +#define __ima_hook_stringify(str)	(#str),
>> +
>> +const char *const func_tokens[] = {
>> +	__ima_hooks(__ima_hook_stringify)
>> +};
>> +
>>  #ifdef	CONFIG_IMA_READ_POLICY
>>  enum {
>>  	mask_exec = 0, mask_write, mask_read, mask_append
>> @@ -1156,12 +1162,6 @@ static const char *const mask_tokens[] = {
>>  	"MAY_APPEND"
>>  };
>>
>> -#define __ima_hook_stringify(str)	(#str),
>> -
>> -static const char *const func_tokens[] = {
>> -	__ima_hooks(__ima_hook_stringify)
>> -};
>> -
>>  void *ima_policy_start(struct seq_file *m, loff_t *pos)
>>  {
>>  	loff_t l = *pos;
>
> Is moving this something left over from previous versions or there is
> a need for this change?

Well, it's not a strong need, but it's still relevant in the current
version. I use func_tokens in ima_read_modsig() in order to be able to
mention the hook name in mod_check_sig()'s error message:

In ima_read_modsig():

	rc = mod_check_sig(sig, buf_len, func_tokens[func]);

And in mod_check_sig():

		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
		       name);

If you think it's not worth it to expose func_tokens, I can make
ima_read_modsig() pass a more generic const string such as "IMA modsig"
for example.

> Other than this, the patch looks good.

Nice!

--
Thiago Jung Bauermann
IBM Linux Technology Center


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 09/12] ima: Implement support for module-style appended signatures
  2019-05-14 12:09   ` Mimi Zohar
@ 2019-05-28 19:27     ` Thiago Jung Bauermann
  0 siblings, 0 replies; 28+ messages in thread
From: Thiago Jung Bauermann @ 2019-05-28 19:27 UTC (permalink / raw)
  To: Mimi Zohar
  Cc: linux-integrity, linux-security-module, keyrings, linux-crypto,
	linuxppc-dev, linux-doc, linux-kernel, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI\,
	Takahiro


Mimi Zohar <zohar@linux.ibm.com> writes:

> Hi Thiago,
>
> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> 
>> @@ -326,6 +356,10 @@ int ima_appraise_measurement(enum ima_hooks func,
>> case INTEGRITY_UNKNOWN:
>> break;
>> case INTEGRITY_NOXATTRS:/* No EVM protected xattrs. */
>> +/* It's fine not to have xattrs when using a modsig. */
>> +if (try_modsig)
>> +break;
>> +/* fall through */
>> case INTEGRITY_NOLABEL:/* No security.evm xattr. */
>> cause = "missing-HMAC";
>> goto out;
>> @@ -340,6 +374,14 @@ int ima_appraise_measurement(enum ima_hooks func,
>> rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
>>  &cause);
>> 
>> +/*
>> + * If we have a modsig and either no imasig or the imasig's key isn't
>> + * known, then try verifying the modsig.
>> + */
>> +if (status != INTEGRITY_PASS && try_modsig &&
>> + (!xattr_value || rc == -ENOKEY))
>> +rc = modsig_verify(func, modsig, &status, &cause);
>
> EVM protects other security xattrs, not just security.ima, if they
> exist. As a result, evm_verifyxattr() could pass based on the other
> security xattrs.

Indeed! It doesn't make sense to test for status != INTEGRITY_PASS here.
Not sure what I was thinking. Thanks for spotting it. With your other
comments about this if clause, this code now reads:

	/*
	 * If we have a modsig and either no imasig or the imasig's key isn't
	 * known, then try verifying the modsig.
	 */
	if (try_modsig &&
	    (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
	     rc == -ENOKEY))
		rc = modsig_verify(func, modsig, &status, &cause);

-- 
Thiago Jung Bauermann
IBM Linux Technology Center


^ permalink raw reply	[flat|nested] 28+ messages in thread

* Re: [PATCH v10 09/12] ima: Implement support for module-style appended signatures
  2019-05-28 19:23     ` Thiago Jung Bauermann
@ 2019-05-28 20:06       ` Mimi Zohar
  0 siblings, 0 replies; 28+ messages in thread
From: Mimi Zohar @ 2019-05-28 20:06 UTC (permalink / raw)
  To: Thiago Jung Bauermann
  Cc: linux-integrity, linux-security-module, keyrings, linux-crypto,
	linuxppc-dev, linux-doc, linux-kernel, Dmitry Kasatkin,
	James Morris, Serge E. Hallyn, David Howells, David Woodhouse,
	Jessica Yu, Herbert Xu, David S. Miller, Jonathan Corbet, AKASHI,
	Takahiro

On Tue, 2019-05-28 at 16:23 -0300, Thiago Jung Bauermann wrote:
> Mimi Zohar <zohar@linux.ibm.com> writes:
> 
> > Hi Thiago,
> >
> >> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> >> index fca7a3f23321..a7a20a8c15c1 100644
> >> --- a/security/integrity/ima/ima_policy.c
> >> +++ b/security/integrity/ima/ima_policy.c
> >> @@ -1144,6 +1144,12 @@ void ima_delete_rules(void)
> >>  	}
> >>  }
> >>
> >> +#define __ima_hook_stringify(str)	(#str),
> >> +
> >> +const char *const func_tokens[] = {
> >> +	__ima_hooks(__ima_hook_stringify)
> >> +};
> >> +
> >>  #ifdef	CONFIG_IMA_READ_POLICY
> >>  enum {
> >>  	mask_exec = 0, mask_write, mask_read, mask_append
> >> @@ -1156,12 +1162,6 @@ static const char *const mask_tokens[] = {
> >>  	"MAY_APPEND"
> >>  };
> >>
> >> -#define __ima_hook_stringify(str)	(#str),
> >> -
> >> -static const char *const func_tokens[] = {
> >> -	__ima_hooks(__ima_hook_stringify)
> >> -};
> >> -
> >>  void *ima_policy_start(struct seq_file *m, loff_t *pos)
> >>  {
> >>  	loff_t l = *pos;
> >
> > Is moving this something left over from previous versions or there is
> > a need for this change?
> 
> Well, it's not a strong need, but it's still relevant in the current
> version. I use func_tokens in ima_read_modsig() in order to be able to
> mention the hook name in mod_check_sig()'s error message:
> 
> In ima_read_modsig():
> 
> 	rc = mod_check_sig(sig, buf_len, func_tokens[func]);
> 
> And in mod_check_sig():
> 
> 		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
> 		       name);
> 
> If you think it's not worth it to expose func_tokens, I can make
> ima_read_modsig() pass a more generic const string such as "IMA modsig"
> for example.

This is fine.  I somehow missed moving func_tokens[] outside of the
ifdef was in order to make it independent of "CONFIG_IMA_READ_POLICY".

thanks,

Mimi


^ permalink raw reply	[flat|nested] 28+ messages in thread

end of thread, back to index

Thread overview: 28+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-04-18  3:51 [PATCH v10 00/12] Appended signatures support for IMA appraisal Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 01/12] MODSIGN: Export module signature definitions Thiago Jung Bauermann
2019-05-09 15:42   ` Mimi Zohar
2019-05-28 19:03     ` Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 02/12] PKCS#7: Refactor verify_pkcs7_signature() Thiago Jung Bauermann
2019-05-09 15:42   ` Mimi Zohar
2019-04-18  3:51 ` [PATCH v10 03/12] PKCS#7: Introduce pkcs7_get_digest() Thiago Jung Bauermann
2019-05-09 15:42   ` Mimi Zohar
2019-04-18  3:51 ` [PATCH v10 04/12] integrity: Introduce struct evm_xattr Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 05/12] integrity: Select CONFIG_KEYS instead of depending on it Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 06/12] ima: Use designated initializers for struct ima_event_data Thiago Jung Bauermann
2019-05-09 15:46   ` Mimi Zohar
2019-04-18  3:51 ` [PATCH v10 07/12] ima: Add modsig appraise_type option for module-style appended signatures Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 08/12] ima: Factor xattr_verify() out of ima_appraise_measurement() Thiago Jung Bauermann
2019-05-09 15:53   ` Mimi Zohar
2019-04-18  3:51 ` [PATCH v10 09/12] ima: Implement support for module-style appended signatures Thiago Jung Bauermann
2019-05-09 23:01   ` Mimi Zohar
2019-05-28 19:23     ` Thiago Jung Bauermann
2019-05-28 20:06       ` Mimi Zohar
2019-05-14 12:09   ` Mimi Zohar
2019-05-28 19:27     ` Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 10/12] ima: Collect modsig Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 11/12] ima: Define ima-modsig template Thiago Jung Bauermann
2019-05-09 23:01   ` Mimi Zohar
2019-05-28 19:09     ` Thiago Jung Bauermann
2019-04-18  3:51 ` [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig Thiago Jung Bauermann
2019-05-28 14:09   ` Mimi Zohar
2019-05-28 19:14     ` Thiago Jung Bauermann

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