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* [PATCH v7 00/21] add integrity and security to TPM2 transactions
@ 2024-02-13 17:13 James Bottomley
  2024-02-13 17:13 ` [PATCH v7 01/21] tpm: Remove unused tpm_buf_tag() James Bottomley
                   ` (21 more replies)
  0 siblings, 22 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

The interest in securing the TPM against interposers, both active and
passive has risen to fever pitch with the demonstration of key
recovery against windows bitlocker:

https://dolosgroup.io/blog/2021/7/9/from-stolen-laptop-to-inside-the-company-network

And subsequently the same attack being successful against all the
Linux TPM based security solutions:

https://www.secura.com/blog/tpm-sniffing-attacks-against-non-bitlocker-targets

The attacks fall into two categories:

1. Passive Interposers, which sit on the bus and merely observe
2. Active Interposers, which try to manipulate TPM transactions on the
   bus using man in the middle and packet stealing to create TPM state
   the interposer owner desires.

Our broadest interposer target is the use of TPM_RS_PW for password
authorization which sends the actual password to the TPM without any
obfuscation and effectively hands it to any interposer. The way to fix
this is to use real sessions for HMAC capabilities to ensure integrity
and to use parameter and response encryption to ensure confidentiality
of the data flowing over the TPM bus.  HMAC sessions by agreeing a
challenge with the TPM and then giving a response which is a HMAC of
the password and the challenge, so the application proves knowledge of
the password to the TPM without ever transmitting the password itself.
Using HMAC sessions when sending commands to the TPM also provides
some measure of protection against active interposers, since the
interposer can't interfere with or delete a HMAC'd command (because
they can't manufacture a response with the correct HMAC).

To protect TPM transactions where there isn't a shared secret
(i.e. the command is something like a PCR extension which doesn't
involve a TPM object with a password) we have to do a bit more work to
set up sessions with a passed in encrypted secret (called a salt) to
act in place of the shared secret in the HMAC.  This secret salt is
effectively a random number encrypted to a public key of the TPM.  The
final piece of the puzzle is using parameter input and response return
encryption, so any interposer can't see the data passing from the
application to the TPM and vice versa.

The most insidious interposer attack of all is a reset attack: since
the interposer has access to the TPM bus, it can assert the TPM reset
line any time it wants.  When a TPM resets it mostly comes back in the
same state except that all the PCRs are reset to their initial values.
Controlling the reset line allows the interposer to change the PCR
state after the fact by resetting the TPM and then replaying PCR
extends to get the PCRs into a valid state to release secrets, so even
if an attack event was recorded, the record is erased.  This reset
attack violates the fundamental princible of non-repudiability of TPM
logs.  Defeating the reset attack involves tying all TPM operations
within the kernel to a property which will change detectably if the
TPM is reset.  For that reason, we tie all TPM sessions to the null
hierarchy we obtain at start of day and whose seed changes on every
reset.  If an active interposer asserts a TPM reset, the new null
primary won't match the kernel's stored one and all TPM operations
will start failing because of HMAC mismatches in the sessions.  So if
the kernel TPM code keeps operating, it guarantees that a reset hasn't
occurred.

The final part of the puzzle is that the machine owner must have a
fixed idea of the EK of their TPM and should have certified this with
the TPM manufacturer.  On every boot, the certified EK public key
should be used to do a make credential/activate credential attestation
key insertion and then the null key certified with the attestation
key.  We can follow a trust on first use model where an OS
installation will extract and verify a public EK and save it to a read
only file.

This patch series adds a simple API which can ensure the above
properties as a layered addition to the existing TPM handling code.
This series now includes protections for PCR extend, getting random
numbers from the TPM and data sealing and unsealing.  It therefore
eliminates all uses of TPM2_RS_PW in the kernel and adds encryption
protection to sensitive data flowing into and out of the TPM.  The
first four patches add more sophisticated buffer handling to the TPM
which is needed to build the more complex encryption and
authentication based commands.  Patch 6 adds all the generic
cryptography primitives and patches 7-9 use them in critical TPM
operations where we want to avoid or detect interposers.  Patch 10
exports the name of the null key we used for boot/run time
verification and patch 11 documents the security guarantees and
expectations.

This was originally sent over four years ago, with the last iteration
being:

https://lore.kernel.org/linux-integrity/1568031515.6613.31.camel@HansenPartnership.com/

I'm dusting it off now because various forces at Microsoft and Google
via the Open Compute Platform are making a lot of noise about
interposers and we in the linux kernel look critically lacking in that
regard, particularly for TPM trusted keys.

---
v2 fixes the problems smatch reported and adds more explanation about
the code motion in the first few patches
v3 rebases the encryption to be against Ard's new library function, the
aescfb addition of which appears as patch 1.
v4 refreshes Ard's patch, adds kernel doc (including a new patch to
add it to the moved tpm-buf functions) updates and rewords some commit
logs
v5: update to proposed tpm-buf implementation (for ease of use all
precursor patches are part of this series, so the actual session HMAC
and encryption begins at patch 10) and add review feedback
v6: split the original sessions patch into three and change the config
variable name
v7: Collect reviews and add extra patch to check for and disable the TPM on
detecting a reset attack.

James

---

Ard Biesheuvel (1):
  crypto: lib - implement library version of AES in CFB mode

James Bottomley (13):
  tpm: Move buffer handling from static inlines to real functions
  tpm: add buffer function to point to returned parameters
  tpm: export the context save and load commands
  tpm: Add NULL primary creation
  tpm: Add HMAC session start and end functions
  tpm: Add HMAC session name/handle append
  tpm: Add the rest of the session HMAC API
  tpm: add hmac checks to tpm2_pcr_extend()
  tpm: add session encryption protection to tpm2_get_random()
  KEYS: trusted: Add session encryption protection to the seal/unseal
    path
  tpm: add the null key name as a sysfs export
  Documentation: add tpm-security.rst
  tpm: disable the TPM if NULL name changes

Jarkko Sakkinen (7):
  tpm: Remove unused tpm_buf_tag()
  tpm: Remove tpm_send()
  tpm: Update struct tpm_buf documentation comments
  tpm: Store the length of the tpm_buf data separately.
  tpm: TPM2B formatted buffers
  tpm: Add tpm_buf_read_{u8,u16,u32}
  KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers

 Documentation/security/tpm/tpm-security.rst |  216 ++++
 drivers/char/tpm/Kconfig                    |   14 +
 drivers/char/tpm/Makefile                   |    2 +
 drivers/char/tpm/tpm-buf.c                  |  251 ++++
 drivers/char/tpm/tpm-chip.c                 |    6 +
 drivers/char/tpm/tpm-interface.c            |   26 +-
 drivers/char/tpm/tpm-sysfs.c                |   18 +
 drivers/char/tpm/tpm.h                      |   14 +
 drivers/char/tpm/tpm2-cmd.c                 |   53 +-
 drivers/char/tpm/tpm2-sessions.c            | 1223 +++++++++++++++++++
 drivers/char/tpm/tpm2-space.c               |   11 +-
 include/crypto/aes.h                        |    5 +
 include/keys/trusted_tpm.h                  |    2 -
 include/linux/tpm.h                         |  296 +++--
 lib/crypto/Kconfig                          |    5 +
 lib/crypto/Makefile                         |    3 +
 lib/crypto/aescfb.c                         |  257 ++++
 security/keys/trusted-keys/trusted_tpm1.c   |   23 +-
 security/keys/trusted-keys/trusted_tpm2.c   |  136 ++-
 19 files changed, 2366 insertions(+), 195 deletions(-)
 create mode 100644 Documentation/security/tpm/tpm-security.rst
 create mode 100644 drivers/char/tpm/tpm-buf.c
 create mode 100644 drivers/char/tpm/tpm2-sessions.c
 create mode 100644 lib/crypto/aescfb.c

-- 
2.35.3


^ permalink raw reply	[flat|nested] 48+ messages in thread

* [PATCH v7 01/21] tpm: Remove unused tpm_buf_tag()
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 02/21] tpm: Remove tpm_send() James Bottomley
                   ` (20 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

The helper function has no call sites. Thus, remove it.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 include/linux/tpm.h | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 4ee9d13749ad..6588ca87cf93 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -358,13 +358,6 @@ static inline u32 tpm_buf_length(struct tpm_buf *buf)
 	return be32_to_cpu(head->length);
 }
 
-static inline u16 tpm_buf_tag(struct tpm_buf *buf)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	return be16_to_cpu(head->tag);
-}
-
 static inline void tpm_buf_append(struct tpm_buf *buf,
 				  const unsigned char *new_data,
 				  unsigned int new_len)
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 02/21] tpm: Remove tpm_send()
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
  2024-02-13 17:13 ` [PATCH v7 01/21] tpm: Remove unused tpm_buf_tag() James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 03/21] tpm: Move buffer handling from static inlines to real functions James Bottomley
                   ` (19 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

Open code the last remaining call site for tpm_send().

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-interface.c          | 25 -----------------------
 include/linux/tpm.h                       |  5 -----
 security/keys/trusted-keys/trusted_tpm1.c | 14 +++++++++++--
 3 files changed, 12 insertions(+), 32 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 66b16d26eecc..163ae247bff2 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -342,31 +342,6 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 }
 EXPORT_SYMBOL_GPL(tpm_pcr_extend);
 
-/**
- * tpm_send - send a TPM command
- * @chip:	a &struct tpm_chip instance, %NULL for the default chip
- * @cmd:	a TPM command buffer
- * @buflen:	the length of the TPM command buffer
- *
- * Return: same as with tpm_transmit_cmd()
- */
-int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
-{
-	struct tpm_buf buf;
-	int rc;
-
-	chip = tpm_find_get_ops(chip);
-	if (!chip)
-		return -ENODEV;
-
-	buf.data = cmd;
-	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to a send a command");
-
-	tpm_put_ops(chip);
-	return rc;
-}
-EXPORT_SYMBOL_GPL(tpm_send);
-
 int tpm_auto_startup(struct tpm_chip *chip)
 {
 	int rc;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6588ca87cf93..d9d645e9c52c 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -422,7 +422,6 @@ extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 			struct tpm_digest *digest);
 extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 			  struct tpm_digest *digests);
-extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
 extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
 extern struct tpm_chip *tpm_default_chip(void);
 void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
@@ -443,10 +442,6 @@ static inline int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	return -ENODEV;
 }
 
-static inline int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
-{
-	return -ENODEV;
-}
 static inline int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max)
 {
 	return -ENODEV;
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index aa108bea6739..37bce84eef99 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -356,17 +356,27 @@ static int TSS_checkhmac2(unsigned char *buffer,
  */
 int trusted_tpm_send(unsigned char *cmd, size_t buflen)
 {
+	struct tpm_buf buf;
 	int rc;
 
 	if (!chip)
 		return -ENODEV;
 
+	rc = tpm_try_get_ops(chip);
+	if (rc)
+		return rc;
+
+	buf.flags = 0;
+	buf.data = cmd;
 	dump_tpm_buf(cmd);
-	rc = tpm_send(chip, cmd, buflen);
+	rc = tpm_transmit_cmd(chip, &buf, 4, "sending data");
 	dump_tpm_buf(cmd);
+
 	if (rc > 0)
-		/* Can't return positive return codes values to keyctl */
+		/* TPM error */
 		rc = -EPERM;
+
+	tpm_put_ops(chip);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(trusted_tpm_send);
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 03/21] tpm: Move buffer handling from static inlines to real functions
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
  2024-02-13 17:13 ` [PATCH v7 01/21] tpm: Remove unused tpm_buf_tag() James Bottomley
  2024-02-13 17:13 ` [PATCH v7 02/21] tpm: Remove tpm_send() James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 04/21] tpm: Update struct tpm_buf documentation comments James Bottomley
                   ` (18 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

separate out the tpm_buf_... handling functions from static inlines in
tpm.h and move them to their own tpm-buf.c file.  This is a precursor
to adding new functions for other TPM type handling because the amount
of code will grow from the current 70 lines in tpm.h to about 200
lines when the additions are done.  200 lines of inline functions is a
bit too much to keep in a header file.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/Makefile  |  1 +
 drivers/char/tpm/tpm-buf.c | 87 ++++++++++++++++++++++++++++++++++++++
 include/linux/tpm.h        | 80 ++++-------------------------------
 3 files changed, 97 insertions(+), 71 deletions(-)
 create mode 100644 drivers/char/tpm/tpm-buf.c

diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 0222b1ddb310..ad3594e383e1 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -15,6 +15,7 @@ tpm-y += tpm-sysfs.o
 tpm-y += eventlog/common.o
 tpm-y += eventlog/tpm1.o
 tpm-y += eventlog/tpm2.o
+tpm-y += tpm-buf.o
 
 tpm-$(CONFIG_ACPI) += tpm_ppi.o eventlog/acpi.o
 tpm-$(CONFIG_EFI) += eventlog/efi.o
diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
new file mode 100644
index 000000000000..96cee41d5b9c
--- /dev/null
+++ b/drivers/char/tpm/tpm-buf.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Handling of TPM command and other buffers.
+ */
+
+#include <linux/module.h>
+#include <linux/tpm.h>
+
+int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!buf->data)
+		return -ENOMEM;
+
+	buf->flags = 0;
+	tpm_buf_reset(buf, tag, ordinal);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init);
+
+void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	head->tag = cpu_to_be16(tag);
+	head->length = cpu_to_be32(sizeof(*head));
+	head->ordinal = cpu_to_be32(ordinal);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_reset);
+
+void tpm_buf_destroy(struct tpm_buf *buf)
+{
+	free_page((unsigned long)buf->data);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_destroy);
+
+u32 tpm_buf_length(struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	return be32_to_cpu(head->length);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_length);
+
+void tpm_buf_append(struct tpm_buf *buf,
+		    const unsigned char *new_data,
+		    unsigned int new_len)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	u32 len = tpm_buf_length(buf);
+
+	/* Return silently if overflow has already happened. */
+	if (buf->flags & TPM_BUF_OVERFLOW)
+		return;
+
+	if ((len + new_len) > PAGE_SIZE) {
+		WARN(1, "tpm_buf: overflow\n");
+		buf->flags |= TPM_BUF_OVERFLOW;
+		return;
+	}
+
+	memcpy(&buf->data[len], new_data, new_len);
+	head->length = cpu_to_be32(len + new_len);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append);
+
+void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value)
+{
+	tpm_buf_append(buf, &value, 1);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u8);
+
+void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value)
+{
+	__be16 value2 = cpu_to_be16(value);
+
+	tpm_buf_append(buf, (u8 *)&value2, 2);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u16);
+
+void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
+{
+	__be32 value2 = cpu_to_be32(value);
+
+	tpm_buf_append(buf, (u8 *)&value2, 4);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index d9d645e9c52c..bb0e8718a432 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -326,77 +326,15 @@ struct tpm2_hash {
 	unsigned int tpm_id;
 };
 
-static inline void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	head->tag = cpu_to_be16(tag);
-	head->length = cpu_to_be32(sizeof(*head));
-	head->ordinal = cpu_to_be32(ordinal);
-}
-
-static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
-{
-	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
-	if (!buf->data)
-		return -ENOMEM;
-
-	buf->flags = 0;
-	tpm_buf_reset(buf, tag, ordinal);
-	return 0;
-}
-
-static inline void tpm_buf_destroy(struct tpm_buf *buf)
-{
-	free_page((unsigned long)buf->data);
-}
-
-static inline u32 tpm_buf_length(struct tpm_buf *buf)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	return be32_to_cpu(head->length);
-}
-
-static inline void tpm_buf_append(struct tpm_buf *buf,
-				  const unsigned char *new_data,
-				  unsigned int new_len)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-	u32 len = tpm_buf_length(buf);
-
-	/* Return silently if overflow has already happened. */
-	if (buf->flags & TPM_BUF_OVERFLOW)
-		return;
-
-	if ((len + new_len) > PAGE_SIZE) {
-		WARN(1, "tpm_buf: overflow\n");
-		buf->flags |= TPM_BUF_OVERFLOW;
-		return;
-	}
-
-	memcpy(&buf->data[len], new_data, new_len);
-	head->length = cpu_to_be32(len + new_len);
-}
-
-static inline void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value)
-{
-	tpm_buf_append(buf, &value, 1);
-}
-
-static inline void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value)
-{
-	__be16 value2 = cpu_to_be16(value);
-
-	tpm_buf_append(buf, (u8 *) &value2, 2);
-}
-
-static inline void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
-{
-	__be32 value2 = cpu_to_be32(value);
-
-	tpm_buf_append(buf, (u8 *) &value2, 4);
-}
+int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
+void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
+void tpm_buf_destroy(struct tpm_buf *buf);
+u32 tpm_buf_length(struct tpm_buf *buf);
+void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
+		    unsigned int new_len);
+void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
+void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
+void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 04/21] tpm: Update struct tpm_buf documentation comments
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (2 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 03/21] tpm: Move buffer handling from static inlines to real functions James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 05/21] tpm: Store the length of the tpm_buf data separately James Bottomley
                   ` (17 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

Remove deprecated portions and document enum values.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 include/linux/tpm.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index bb0e8718a432..0a8c1351adc2 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -297,15 +297,14 @@ struct tpm_header {
 	};
 } __packed;
 
-/* A string buffer type for constructing TPM commands. This is based on the
- * ideas of string buffer code in security/keys/trusted.h but is heap based
- * in order to keep the stack usage minimal.
- */
-
 enum tpm_buf_flags {
+	/* the capacity exceeded: */
 	TPM_BUF_OVERFLOW	= BIT(0),
 };
 
+/*
+ * A string buffer type for constructing TPM commands.
+ */
 struct tpm_buf {
 	unsigned int flags;
 	u8 *data;
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 05/21] tpm: Store the length of the tpm_buf data separately.
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (3 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 04/21] tpm: Update struct tpm_buf documentation comments James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 06/21] tpm: TPM2B formatted buffers James Bottomley
                   ` (16 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

TPM2B buffers, or sized buffers, have a two byte header, which contains the
length of the payload as a 16-bit big-endian number, without counting in
the space taken by the header. This differs from encoding in the TPM header
where the length includes also the bytes taken by the header.

Unbound the length of a tpm_buf from the value stored to the TPM command
header. A separate encoding and decoding step so that different buffer
types can be supported, with variant header format and length encoding.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c                | 48 +++++++++++++++++------
 drivers/char/tpm/tpm-interface.c          |  1 +
 include/keys/trusted_tpm.h                |  2 -
 include/linux/tpm.h                       |  6 +--
 security/keys/trusted-keys/trusted_tpm1.c |  9 +++--
 5 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 96cee41d5b9c..3f39893f3bb1 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -3,25 +3,44 @@
  * Handling of TPM command and other buffers.
  */
 
+#include <linux/tpm_command.h>
 #include <linux/module.h>
 #include <linux/tpm.h>
 
+/**
+ * tpm_buf_init() - Allocate and initialize a TPM command
+ * @buf:	A &tpm_buf
+ * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
+ * @ordinal:	A command ordinal
+ *
+ * Return: 0 or -ENOMEM
+ */
 int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
 {
 	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
 	if (!buf->data)
 		return -ENOMEM;
 
-	buf->flags = 0;
 	tpm_buf_reset(buf, tag, ordinal);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_buf_init);
 
+/**
+ * tpm_buf_reset() - Initialize a TPM command
+ * @buf:	A &tpm_buf
+ * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
+ * @ordinal:	A command ordinal
+ */
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
 
+	WARN_ON(tag != TPM_TAG_RQU_COMMAND && tag != TPM2_ST_NO_SESSIONS &&
+		tag != TPM2_ST_SESSIONS && tag != 0);
+
+	buf->flags = 0;
+	buf->length = sizeof(*head);
 	head->tag = cpu_to_be16(tag);
 	head->length = cpu_to_be32(sizeof(*head));
 	head->ordinal = cpu_to_be32(ordinal);
@@ -34,33 +53,40 @@ void tpm_buf_destroy(struct tpm_buf *buf)
 }
 EXPORT_SYMBOL_GPL(tpm_buf_destroy);
 
+/**
+ * tpm_buf_length() - Return the number of bytes consumed by the data
+ *
+ * Return: The number of bytes consumed by the buffer
+ */
 u32 tpm_buf_length(struct tpm_buf *buf)
 {
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	return be32_to_cpu(head->length);
+	return buf->length;
 }
 EXPORT_SYMBOL_GPL(tpm_buf_length);
 
-void tpm_buf_append(struct tpm_buf *buf,
-		    const unsigned char *new_data,
-		    unsigned int new_len)
+/**
+ * tpm_buf_append() - Append data to an initialized buffer
+ * @buf:	A &tpm_buf
+ * @new_data:	A data blob
+ * @new_length:	Size of the appended data
+ */
+void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
-	u32 len = tpm_buf_length(buf);
 
 	/* Return silently if overflow has already happened. */
 	if (buf->flags & TPM_BUF_OVERFLOW)
 		return;
 
-	if ((len + new_len) > PAGE_SIZE) {
+	if ((buf->length + new_length) > PAGE_SIZE) {
 		WARN(1, "tpm_buf: overflow\n");
 		buf->flags |= TPM_BUF_OVERFLOW;
 		return;
 	}
 
-	memcpy(&buf->data[len], new_data, new_len);
-	head->length = cpu_to_be32(len + new_len);
+	memcpy(&buf->data[buf->length], new_data, new_length);
+	buf->length += new_length;
+	head->length = cpu_to_be32(buf->length);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append);
 
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 163ae247bff2..ea75f2776c2f 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -232,6 +232,7 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf *buf,
 	if (len < min_rsp_body_length + TPM_HEADER_SIZE)
 		return -EFAULT;
 
+	buf->length = len;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_transmit_cmd);
diff --git a/include/keys/trusted_tpm.h b/include/keys/trusted_tpm.h
index 7769b726863a..a088b33fd0e3 100644
--- a/include/keys/trusted_tpm.h
+++ b/include/keys/trusted_tpm.h
@@ -6,8 +6,6 @@
 #include <linux/tpm_command.h>
 
 /* implementation specific TPM constants */
-#define MAX_BUF_SIZE			1024
-#define TPM_GETRANDOM_SIZE		14
 #define TPM_SIZE_OFFSET			2
 #define TPM_RETURN_OFFSET		6
 #define TPM_DATA_OFFSET			10
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 0a8c1351adc2..1d7b39b5c383 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -306,7 +306,8 @@ enum tpm_buf_flags {
  * A string buffer type for constructing TPM commands.
  */
 struct tpm_buf {
-	unsigned int flags;
+	u32 flags;
+	u32 length;
 	u8 *data;
 };
 
@@ -329,8 +330,7 @@ int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
-void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
-		    unsigned int new_len);
+void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
 void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
 void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
 void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 37bce84eef99..89c9798d1800 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -367,6 +367,7 @@ int trusted_tpm_send(unsigned char *cmd, size_t buflen)
 		return rc;
 
 	buf.flags = 0;
+	buf.length = buflen;
 	buf.data = cmd;
 	dump_tpm_buf(cmd);
 	rc = tpm_transmit_cmd(chip, &buf, 4, "sending data");
@@ -417,7 +418,7 @@ static int osap(struct tpm_buf *tb, struct osapsess *s,
 	tpm_buf_append_u32(tb, handle);
 	tpm_buf_append(tb, ononce, TPM_NONCE_SIZE);
 
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0)
 		return ret;
 
@@ -441,7 +442,7 @@ int oiap(struct tpm_buf *tb, uint32_t *handle, unsigned char *nonce)
 		return -ENODEV;
 
 	tpm_buf_reset(tb, TPM_TAG_RQU_COMMAND, TPM_ORD_OIAP);
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0)
 		return ret;
 
@@ -553,7 +554,7 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
 	tpm_buf_append_u8(tb, cont);
 	tpm_buf_append(tb, td->pubauth, SHA1_DIGEST_SIZE);
 
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0)
 		goto out;
 
@@ -644,7 +645,7 @@ static int tpm_unseal(struct tpm_buf *tb,
 	tpm_buf_append_u8(tb, cont);
 	tpm_buf_append(tb, authdata2, SHA1_DIGEST_SIZE);
 
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0) {
 		pr_info("authhmac failed (%d)\n", ret);
 		return ret;
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 06/21] tpm: TPM2B formatted buffers
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (4 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 05/21] tpm: Store the length of the tpm_buf data separately James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 07/21] tpm: Add tpm_buf_read_{u8,u16,u32} James Bottomley
                   ` (15 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

Declare tpm_buf_init_sized() and tpm_buf_reset_sized() for creating TPM2B
formatted buffers. These buffers are also known as sized buffers in the
specifications and literature.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c | 38 +++++++++++++++++++++++++++++++++++---
 include/linux/tpm.h        |  4 ++++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 3f39893f3bb1..099b4a56c5d5 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -47,6 +47,36 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 }
 EXPORT_SYMBOL_GPL(tpm_buf_reset);
 
+/**
+ * tpm_buf_init_sized() - Allocate and initialize a sized (TPM2B) buffer
+ * @buf:	A @tpm_buf
+ *
+ * Return: 0 or -ENOMEM
+ */
+int tpm_buf_init_sized(struct tpm_buf *buf)
+{
+	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!buf->data)
+		return -ENOMEM;
+
+	tpm_buf_reset_sized(buf);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
+
+/**
+ * tpm_buf_reset_sized() - Initialize a sized buffer
+ * @buf:	A &tpm_buf
+ */
+void tpm_buf_reset_sized(struct tpm_buf *buf)
+{
+	buf->flags = TPM_BUF_TPM2B;
+	buf->length = 2;
+	buf->data[0] = 0;
+	buf->data[1] = 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
+
 void tpm_buf_destroy(struct tpm_buf *buf)
 {
 	free_page((unsigned long)buf->data);
@@ -72,8 +102,6 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
  */
 void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 {
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
 	/* Return silently if overflow has already happened. */
 	if (buf->flags & TPM_BUF_OVERFLOW)
 		return;
@@ -86,7 +114,11 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 
 	memcpy(&buf->data[buf->length], new_data, new_length);
 	buf->length += new_length;
-	head->length = cpu_to_be32(buf->length);
+
+	if (buf->flags & TPM_BUF_TPM2B)
+		((__be16 *)buf->data)[0] = cpu_to_be16(buf->length - 2);
+	else
+		((struct tpm_header *)buf->data)->length = cpu_to_be32(buf->length);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append);
 
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 1d7b39b5c383..715db4a91c1f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -300,6 +300,8 @@ struct tpm_header {
 enum tpm_buf_flags {
 	/* the capacity exceeded: */
 	TPM_BUF_OVERFLOW	= BIT(0),
+	/* TPM2B format: */
+	TPM_BUF_TPM2B		= BIT(1),
 };
 
 /*
@@ -328,6 +330,8 @@ struct tpm2_hash {
 
 int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
+int tpm_buf_init_sized(struct tpm_buf *buf);
+void tpm_buf_reset_sized(struct tpm_buf *buf);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
 void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 07/21] tpm: Add tpm_buf_read_{u8,u16,u32}
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (5 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 06/21] tpm: TPM2B formatted buffers James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 08/21] KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers James Bottomley
                   ` (14 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

Declare reader functions for the instances of struct tpm_buf. If the read
goes out of boundary, TPM_BUF_BOUNDARY_ERROR is set, and subsequent read
will do nothing.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c | 79 +++++++++++++++++++++++++++++++++++++-
 include/linux/tpm.h        |  5 +++
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 099b4a56c5d5..32619e9ab4fa 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -107,7 +107,7 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 		return;
 
 	if ((buf->length + new_length) > PAGE_SIZE) {
-		WARN(1, "tpm_buf: overflow\n");
+		WARN(1, "tpm_buf: write overflow\n");
 		buf->flags |= TPM_BUF_OVERFLOW;
 		return;
 	}
@@ -143,3 +143,80 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
 	tpm_buf_append(buf, (u8 *)&value2, 4);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
+
+/**
+ * tpm_buf_read() - Read from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ * @count:	the number of bytes to read
+ * @output:	the output buffer
+ */
+static void tpm_buf_read(struct tpm_buf *buf, off_t *offset, size_t count, void *output)
+{
+	off_t next_offset;
+
+	/* Return silently if overflow has already happened. */
+	if (buf->flags & TPM_BUF_BOUNDARY_ERROR)
+		return;
+
+	next_offset = *offset + count;
+	if (next_offset > buf->length) {
+		WARN(1, "tpm_buf: read out of boundary\n");
+		buf->flags |= TPM_BUF_BOUNDARY_ERROR;
+		return;
+	}
+
+	memcpy(output, &buf->data[*offset], count);
+	*offset = next_offset;
+}
+
+/**
+ * tpm_buf_read_u8() - Read 8-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 8-bit word
+ */
+u8 tpm_buf_read_u8(struct tpm_buf *buf, off_t *offset)
+{
+	u8 value;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return value;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u8);
+
+/**
+ * tpm_buf_read_u16() - Read 16-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 16-bit word
+ */
+u16 tpm_buf_read_u16(struct tpm_buf *buf, off_t *offset)
+{
+	u16 value;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return be16_to_cpu(value);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u16);
+
+/**
+ * tpm_buf_read_u32() - Read 32-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 32-bit word
+ */
+u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset)
+{
+	u32 value;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return be32_to_cpu(value);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u32);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 715db4a91c1f..e8172f81c562 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -302,6 +302,8 @@ enum tpm_buf_flags {
 	TPM_BUF_OVERFLOW	= BIT(0),
 	/* TPM2B format: */
 	TPM_BUF_TPM2B		= BIT(1),
+	/* read out of boundary: */
+	TPM_BUF_BOUNDARY_ERROR	= BIT(2),
 };
 
 /*
@@ -338,6 +340,9 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
 void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
 void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
 void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
+u8 tpm_buf_read_u8(struct tpm_buf *buf, off_t *offset);
+u16 tpm_buf_read_u16(struct tpm_buf *buf, off_t *offset);
+u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 08/21] KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (6 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 07/21] tpm: Add tpm_buf_read_{u8,u16,u32} James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 09/21] crypto: lib - implement library version of AES in CFB mode James Bottomley
                   ` (13 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Jarkko Sakkinen <jarkko@kernel.org>

Take advantage of the new sized buffer (TPM2B) mode of struct tpm_buf in
tpm2_seal_trusted(). This allows to add robustness to the command
construction without requiring to calculate buffer sizes manually.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 security/keys/trusted-keys/trusted_tpm2.c | 54 +++++++++++++----------
 1 file changed, 31 insertions(+), 23 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index bc700f85f80b..97b1dfca2dba 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -228,8 +228,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		      struct trusted_key_payload *payload,
 		      struct trusted_key_options *options)
 {
+	off_t offset = TPM_HEADER_SIZE;
+	struct tpm_buf buf, sized;
 	int blob_len = 0;
-	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
 	int i;
@@ -258,6 +259,14 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		return rc;
 	}
 
+	rc = tpm_buf_init_sized(&sized);
+	if (rc) {
+		tpm_buf_destroy(&buf);
+		tpm_put_ops(chip);
+		return rc;
+	}
+
+	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	tpm_buf_append_u32(&buf, options->keyhandle);
 	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
 			     NULL /* nonce */, 0,
@@ -266,36 +275,36 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 			     TPM_DIGEST_SIZE);
 
 	/* sensitive */
-	tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len);
+	tpm_buf_append_u16(&sized, options->blobauth_len);
 
-	tpm_buf_append_u16(&buf, options->blobauth_len);
 	if (options->blobauth_len)
-		tpm_buf_append(&buf, options->blobauth, options->blobauth_len);
+		tpm_buf_append(&sized, options->blobauth, options->blobauth_len);
 
-	tpm_buf_append_u16(&buf, payload->key_len);
-	tpm_buf_append(&buf, payload->key, payload->key_len);
+	tpm_buf_append_u16(&sized, payload->key_len);
+	tpm_buf_append(&sized, payload->key, payload->key_len);
+	tpm_buf_append(&buf, sized.data, sized.length);
 
 	/* public */
-	tpm_buf_append_u16(&buf, 14 + options->policydigest_len);
-	tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH);
-	tpm_buf_append_u16(&buf, hash);
+	tpm_buf_reset_sized(&sized);
+	tpm_buf_append_u16(&sized, TPM_ALG_KEYEDHASH);
+	tpm_buf_append_u16(&sized, hash);
 
 	/* key properties */
 	flags = 0;
 	flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
-	flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM |
-					    TPM2_OA_FIXED_PARENT);
-	tpm_buf_append_u32(&buf, flags);
+	flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT);
+	tpm_buf_append_u32(&sized, flags);
 
 	/* policy */
-	tpm_buf_append_u16(&buf, options->policydigest_len);
+	tpm_buf_append_u16(&sized, options->policydigest_len);
 	if (options->policydigest_len)
-		tpm_buf_append(&buf, options->policydigest,
-			       options->policydigest_len);
+		tpm_buf_append(&sized, options->policydigest, options->policydigest_len);
 
 	/* public parameters */
-	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
-	tpm_buf_append_u16(&buf, 0);
+	tpm_buf_append_u16(&sized, TPM_ALG_NULL);
+	tpm_buf_append_u16(&sized, 0);
+
+	tpm_buf_append(&buf, sized.data, sized.length);
 
 	/* outside info */
 	tpm_buf_append_u16(&buf, 0);
@@ -312,21 +321,20 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (rc)
 		goto out;
 
-	blob_len = be32_to_cpup((__be32 *) &buf.data[TPM_HEADER_SIZE]);
-	if (blob_len > MAX_BLOB_SIZE) {
+	blob_len = tpm_buf_read_u32(&buf, &offset);
+	if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_BOUNDARY_ERROR) {
 		rc = -E2BIG;
 		goto out;
 	}
-	if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
+	if (buf.length - offset < blob_len) {
 		rc = -EFAULT;
 		goto out;
 	}
 
-	blob_len = tpm2_key_encode(payload, options,
-				   &buf.data[TPM_HEADER_SIZE + 4],
-				   blob_len);
+	blob_len = tpm2_key_encode(payload, options, &buf.data[offset], blob_len);
 
 out:
+	tpm_buf_destroy(&sized);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0) {
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 09/21] crypto: lib - implement library version of AES in CFB mode
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (7 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 08/21] KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 10/21] tpm: add buffer function to point to returned parameters James Bottomley
                   ` (12 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

From: Ard Biesheuvel <ardb@kernel.org>

Implement AES in CFB mode using the existing, mostly constant-time
generic AES library implementation. This will be used by the TPM code
to encrypt communications with TPM hardware, which is often a discrete
component connected using sniffable wires or traces.

While a CFB template does exist, using a skcipher is a major pain for
non-performance critical synchronous crypto where the algorithm is known
at compile time and the data is in contiguous buffers with valid kernel
virtual addresses.

Tested-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/all/20230216201410.15010-1-James.Bottomley@HansenPartnership.com/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 include/crypto/aes.h |   5 +
 lib/crypto/Kconfig   |   5 +
 lib/crypto/Makefile  |   3 +
 lib/crypto/aescfb.c  | 257 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 270 insertions(+)
 create mode 100644 lib/crypto/aescfb.c

diff --git a/include/crypto/aes.h b/include/crypto/aes.h
index 2090729701ab..9339da7c20a8 100644
--- a/include/crypto/aes.h
+++ b/include/crypto/aes.h
@@ -87,4 +87,9 @@ void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in);
 extern const u8 crypto_aes_sbox[];
 extern const u8 crypto_aes_inv_sbox[];
 
+void aescfb_encrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 iv[AES_BLOCK_SIZE]);
+void aescfb_decrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 iv[AES_BLOCK_SIZE]);
+
 #endif
diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
index 45436bfc6dff..b01253cac70a 100644
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -8,6 +8,11 @@ config CRYPTO_LIB_UTILS
 config CRYPTO_LIB_AES
 	tristate
 
+config CRYPTO_LIB_AESCFB
+	tristate
+	select CRYPTO_LIB_AES
+	select CRYPTO_LIB_UTILS
+
 config CRYPTO_LIB_AESGCM
 	tristate
 	select CRYPTO_LIB_AES
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 8d1446c2be71..969baab8c805 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -10,6 +10,9 @@ obj-$(CONFIG_CRYPTO_LIB_CHACHA_GENERIC)		+= libchacha.o
 obj-$(CONFIG_CRYPTO_LIB_AES)			+= libaes.o
 libaes-y					:= aes.o
 
+obj-$(CONFIG_CRYPTO_LIB_AESCFB)			+= libaescfb.o
+libaescfb-y					:= aescfb.o
+
 obj-$(CONFIG_CRYPTO_LIB_AESGCM)			+= libaesgcm.o
 libaesgcm-y					:= aesgcm.o
 
diff --git a/lib/crypto/aescfb.c b/lib/crypto/aescfb.c
new file mode 100644
index 000000000000..749dc1258a44
--- /dev/null
+++ b/lib/crypto/aescfb.c
@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Minimal library implementation of AES in CFB mode
+ *
+ * Copyright 2023 Google LLC
+ */
+
+#include <linux/module.h>
+
+#include <crypto/algapi.h>
+#include <crypto/aes.h>
+
+#include <asm/irqflags.h>
+
+static void aescfb_encrypt_block(const struct crypto_aes_ctx *ctx, void *dst,
+				 const void *src)
+{
+	unsigned long flags;
+
+	/*
+	 * In AES-CFB, the AES encryption operates on known 'plaintext' (the IV
+	 * and ciphertext), making it susceptible to timing attacks on the
+	 * encryption key. The AES library already mitigates this risk to some
+	 * extent by pulling the entire S-box into the caches before doing any
+	 * substitutions, but this strategy is more effective when running with
+	 * interrupts disabled.
+	 */
+	local_irq_save(flags);
+	aes_encrypt(ctx, dst, src);
+	local_irq_restore(flags);
+}
+
+/**
+ * aescfb_encrypt - Perform AES-CFB encryption on a block of data
+ *
+ * @ctx:	The AES-CFB key schedule
+ * @dst:	Pointer to the ciphertext output buffer
+ * @src:	Pointer the plaintext (may equal @dst for encryption in place)
+ * @len:	The size in bytes of the plaintext and ciphertext.
+ * @iv:		The initialization vector (IV) to use for this block of data
+ */
+void aescfb_encrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 iv[AES_BLOCK_SIZE])
+{
+	u8 ks[AES_BLOCK_SIZE];
+	const u8 *v = iv;
+
+	while (len > 0) {
+		aescfb_encrypt_block(ctx, ks, v);
+		crypto_xor_cpy(dst, src, ks, min(len, AES_BLOCK_SIZE));
+		v = dst;
+
+		dst += AES_BLOCK_SIZE;
+		src += AES_BLOCK_SIZE;
+		len -= AES_BLOCK_SIZE;
+	}
+
+	memzero_explicit(ks, sizeof(ks));
+}
+EXPORT_SYMBOL(aescfb_encrypt);
+
+/**
+ * aescfb_decrypt - Perform AES-CFB decryption on a block of data
+ *
+ * @ctx:	The AES-CFB key schedule
+ * @dst:	Pointer to the plaintext output buffer
+ * @src:	Pointer the ciphertext (may equal @dst for decryption in place)
+ * @len:	The size in bytes of the plaintext and ciphertext.
+ * @iv:		The initialization vector (IV) to use for this block of data
+ */
+void aescfb_decrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 iv[AES_BLOCK_SIZE])
+{
+	u8 ks[2][AES_BLOCK_SIZE];
+
+	aescfb_encrypt_block(ctx, ks[0], iv);
+
+	for (int i = 0; len > 0; i ^= 1) {
+		if (len > AES_BLOCK_SIZE)
+			/*
+			 * Generate the keystream for the next block before
+			 * performing the XOR, as that may update in place and
+			 * overwrite the ciphertext.
+			 */
+			aescfb_encrypt_block(ctx, ks[!i], src);
+
+		crypto_xor_cpy(dst, src, ks[i], min(len, AES_BLOCK_SIZE));
+
+		dst += AES_BLOCK_SIZE;
+		src += AES_BLOCK_SIZE;
+		len -= AES_BLOCK_SIZE;
+	}
+
+	memzero_explicit(ks, sizeof(ks));
+}
+EXPORT_SYMBOL(aescfb_decrypt);
+
+MODULE_DESCRIPTION("Generic AES-CFB library");
+MODULE_AUTHOR("Ard Biesheuvel <ardb@kernel.org>");
+MODULE_LICENSE("GPL");
+
+#ifndef CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
+
+/*
+ * Test code below. Vectors taken from crypto/testmgr.h
+ */
+
+static struct {
+	u8	ptext[64];
+	u8	ctext[64];
+
+	u8	key[AES_MAX_KEY_SIZE];
+	u8	iv[AES_BLOCK_SIZE];
+
+	int	klen;
+	int	len;
+} const aescfb_tv[] __initconst = {
+	{ /* From NIST SP800-38A */
+		.key    = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"
+			  "\xab\xf7\x15\x88\x09\xcf\x4f\x3c",
+		.klen	= 16,
+		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"
+			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
+		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"
+			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"
+			  "\xae\x2d\x8a\x57\x1e\x03\xac\x9c"
+			  "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51"
+			  "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11"
+			  "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef"
+			  "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17"
+			  "\xad\x2b\x41\x7b\xe6\x6c\x37\x10",
+		.ctext	= "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20"
+			  "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a"
+			  "\xc8\xa6\x45\x37\xa0\xb3\xa9\x3f"
+			  "\xcd\xe3\xcd\xad\x9f\x1c\xe5\x8b"
+			  "\x26\x75\x1f\x67\xa3\xcb\xb1\x40"
+			  "\xb1\x80\x8c\xf1\x87\xa4\xf4\xdf"
+			  "\xc0\x4b\x05\x35\x7c\x5d\x1c\x0e"
+			  "\xea\xc4\xc6\x6f\x9f\xf7\xf2\xe6",
+		.len	= 64,
+	}, {
+		.key	= "\x8e\x73\xb0\xf7\xda\x0e\x64\x52"
+			  "\xc8\x10\xf3\x2b\x80\x90\x79\xe5"
+			  "\x62\xf8\xea\xd2\x52\x2c\x6b\x7b",
+		.klen	= 24,
+		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"
+			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
+		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"
+			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"
+			  "\xae\x2d\x8a\x57\x1e\x03\xac\x9c"
+			  "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51"
+			  "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11"
+			  "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef"
+			  "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17"
+			  "\xad\x2b\x41\x7b\xe6\x6c\x37\x10",
+		.ctext	= "\xcd\xc8\x0d\x6f\xdd\xf1\x8c\xab"
+			  "\x34\xc2\x59\x09\xc9\x9a\x41\x74"
+			  "\x67\xce\x7f\x7f\x81\x17\x36\x21"
+			  "\x96\x1a\x2b\x70\x17\x1d\x3d\x7a"
+			  "\x2e\x1e\x8a\x1d\xd5\x9b\x88\xb1"
+			  "\xc8\xe6\x0f\xed\x1e\xfa\xc4\xc9"
+			  "\xc0\x5f\x9f\x9c\xa9\x83\x4f\xa0"
+			  "\x42\xae\x8f\xba\x58\x4b\x09\xff",
+		.len	= 64,
+	}, {
+		.key	= "\x60\x3d\xeb\x10\x15\xca\x71\xbe"
+			  "\x2b\x73\xae\xf0\x85\x7d\x77\x81"
+			  "\x1f\x35\x2c\x07\x3b\x61\x08\xd7"
+			  "\x2d\x98\x10\xa3\x09\x14\xdf\xf4",
+		.klen	= 32,
+		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"
+			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
+		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"
+			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"
+			  "\xae\x2d\x8a\x57\x1e\x03\xac\x9c"
+			  "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51"
+			  "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11"
+			  "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef"
+			  "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17"
+			  "\xad\x2b\x41\x7b\xe6\x6c\x37\x10",
+		.ctext	= "\xdc\x7e\x84\xbf\xda\x79\x16\x4b"
+			  "\x7e\xcd\x84\x86\x98\x5d\x38\x60"
+			  "\x39\xff\xed\x14\x3b\x28\xb1\xc8"
+			  "\x32\x11\x3c\x63\x31\xe5\x40\x7b"
+			  "\xdf\x10\x13\x24\x15\xe5\x4b\x92"
+			  "\xa1\x3e\xd0\xa8\x26\x7a\xe2\xf9"
+			  "\x75\xa3\x85\x74\x1a\xb9\xce\xf8"
+			  "\x20\x31\x62\x3d\x55\xb1\xe4\x71",
+		.len	= 64,
+	}, { /* > 16 bytes, not a multiple of 16 bytes */
+		.key	= "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"
+			  "\xab\xf7\x15\x88\x09\xcf\x4f\x3c",
+		.klen	= 16,
+		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"
+			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
+		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"
+			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"
+			  "\xae",
+		.ctext	= "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20"
+			  "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a"
+			  "\xc8",
+		.len	= 17,
+	}, { /* < 16 bytes */
+		.key	= "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"
+			  "\xab\xf7\x15\x88\x09\xcf\x4f\x3c",
+		.klen	= 16,
+		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"
+			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
+		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f",
+		.ctext	= "\x3b\x3f\xd9\x2e\xb7\x2d\xad",
+		.len	= 7,
+	},
+};
+
+static int __init libaescfb_init(void)
+{
+	for (int i = 0; i < ARRAY_SIZE(aescfb_tv); i++) {
+		struct crypto_aes_ctx ctx;
+		u8 buf[64];
+
+		if (aes_expandkey(&ctx, aescfb_tv[i].key, aescfb_tv[i].klen)) {
+			pr_err("aes_expandkey() failed on vector %d\n", i);
+			return -ENODEV;
+		}
+
+		aescfb_encrypt(&ctx, buf, aescfb_tv[i].ptext, aescfb_tv[i].len,
+			       aescfb_tv[i].iv);
+		if (memcmp(buf, aescfb_tv[i].ctext, aescfb_tv[i].len)) {
+			pr_err("aescfb_encrypt() #1 failed on vector %d\n", i);
+			return -ENODEV;
+		}
+
+		/* decrypt in place */
+		aescfb_decrypt(&ctx, buf, buf, aescfb_tv[i].len, aescfb_tv[i].iv);
+		if (memcmp(buf, aescfb_tv[i].ptext, aescfb_tv[i].len)) {
+			pr_err("aescfb_decrypt() failed on vector %d\n", i);
+			return -ENODEV;
+		}
+
+		/* encrypt in place */
+		aescfb_encrypt(&ctx, buf, buf, aescfb_tv[i].len, aescfb_tv[i].iv);
+		if (memcmp(buf, aescfb_tv[i].ctext, aescfb_tv[i].len)) {
+			pr_err("aescfb_encrypt() #2 failed on vector %d\n", i);
+
+			return -ENODEV;
+		}
+
+	}
+	return 0;
+}
+module_init(libaescfb_init);
+
+static void __exit libaescfb_exit(void)
+{
+}
+module_exit(libaescfb_exit);
+#endif
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 10/21] tpm: add buffer function to point to returned parameters
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (8 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 09/21] crypto: lib - implement library version of AES in CFB mode James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 11/21] tpm: export the context save and load commands James Bottomley
                   ` (11 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Replace all instances of &buf.data[TPM_HEADER_SIZE] with a new
function tpm_buf_parameters() because encryption sessions change
where the return parameters are located in the buffer since if a
return session is present they're 4 bytes beyond the header with those
4 bytes giving the parameter length.  If there is no return session,
then they're in the usual place immediately after the header.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---
v4: add kdoc
v5: update kdoc add review
v7: add review
---
 drivers/char/tpm/tpm-buf.c | 28 ++++++++++++++++++++++++++++
 include/linux/tpm.h        |  2 ++
 2 files changed, 30 insertions(+)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 32619e9ab4fa..bb81180495d1 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -220,3 +220,31 @@ u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset)
 	return be32_to_cpu(value);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_read_u32);
+
+static u16 tpm_buf_tag(struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	return be16_to_cpu(head->tag);
+}
+
+/**
+ * tpm_buf_parameters - return the TPM response parameters area of the tpm_buf
+ * @buf: tpm_buf to use
+ *
+ * Where the parameters are located depends on the tag of a TPM
+ * command (it's immediately after the header for TPM_ST_NO_SESSIONS
+ * or 4 bytes after for TPM_ST_SESSIONS). Evaluate this and return a
+ * pointer to the first byte of the parameters area.
+ *
+ * @return: pointer to parameters area
+ */
+u8 *tpm_buf_parameters(struct tpm_buf *buf)
+{
+	int offset = TPM_HEADER_SIZE;
+
+	if (tpm_buf_tag(buf) == TPM2_ST_SESSIONS)
+		offset += 4;
+
+	return &buf->data[offset];
+}
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index e8172f81c562..6be263509e81 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -344,6 +344,8 @@ u8 tpm_buf_read_u8(struct tpm_buf *buf, off_t *offset);
 u16 tpm_buf_read_u16(struct tpm_buf *buf, off_t *offset);
 u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset);
 
+u8 *tpm_buf_parameters(struct tpm_buf *buf);
+
 /*
  * Check if TPM device is in the firmware upgrade mode.
  */
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 11/21] tpm: export the context save and load commands
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (9 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 10/21] tpm: add buffer function to point to returned parameters James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 12/21] tpm: Add NULL primary creation James Bottomley
                   ` (10 subsequent siblings)
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

The TPM2 session HMAC and encryption handling code needs to save and
restore a single volatile context for the elliptic curve version of
the NULL seed, so export the APIs which do this for internal use.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---

v5: add review
v7: add review
---
 drivers/char/tpm/tpm.h        | 4 ++++
 drivers/char/tpm/tpm2-space.c | 8 ++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 61445f1dc46d..cbc9d1e2974d 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -312,6 +312,10 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
 		      size_t *bufsiz);
 int tpm_devs_add(struct tpm_chip *chip);
 void tpm_devs_remove(struct tpm_chip *chip);
+int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
+		      unsigned int buf_size, unsigned int *offset);
+int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
+		      unsigned int *offset, u32 *handle);
 
 void tpm_bios_log_setup(struct tpm_chip *chip);
 void tpm_bios_log_teardown(struct tpm_chip *chip);
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 363afdd4d1d3..24479a81c23c 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -68,8 +68,8 @@ void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space)
 	kfree(space->session_buf);
 }
 
-static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
-			     unsigned int *offset, u32 *handle)
+int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
+		      unsigned int *offset, u32 *handle)
 {
 	struct tpm_buf tbuf;
 	struct tpm2_context *ctx;
@@ -119,8 +119,8 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
 	return 0;
 }
 
-static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
-			     unsigned int buf_size, unsigned int *offset)
+int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
+		      unsigned int buf_size, unsigned int *offset)
 {
 	struct tpm_buf tbuf;
 	unsigned int body_size;
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (10 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 11/21] tpm: export the context save and load commands James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 15:51   ` Jarkko Sakkinen
  2024-03-30 18:48   ` Gabríel Arthúr Pétursson
  2024-02-13 17:13 ` [PATCH v7 13/21] tpm: Add HMAC session start and end functions James Bottomley
                   ` (9 subsequent siblings)
  21 siblings, 2 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

The session handling code uses a "salted" session, meaning a session
whose salt is encrypted to the public part of another TPM key so an
observer cannot obtain it (and thus deduce the session keys).  This
patch creates and context saves in the tpm_chip area the primary key
of the NULL hierarchy for this purpose.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---
v6: split out of original HMAC patch update config name
v7: rename null seed parameters
---
 drivers/char/tpm/Kconfig         |  11 ++
 drivers/char/tpm/Makefile        |   1 +
 drivers/char/tpm/tpm.h           |  10 ++
 drivers/char/tpm/tpm2-cmd.c      |   5 +
 drivers/char/tpm/tpm2-sessions.c | 276 +++++++++++++++++++++++++++++++
 include/linux/tpm.h              |  49 ++++++
 6 files changed, 352 insertions(+)
 create mode 100644 drivers/char/tpm/tpm2-sessions.c

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 927088b2c3d3..e3c39a83171b 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -27,6 +27,17 @@ menuconfig TCG_TPM
 
 if TCG_TPM
 
+config TCG_TPM2_HMAC
+	bool "Use encrypted and HMACd transactions on the TPM bus"
+	default y
+	help
+          Setting this causes us to deploy a scheme which uses request
+	  and response HMACs in addition to encryption for
+	  communicating with the TPM to prevent or detect bus snooping
+	  and interposer attacks (see tpm-security.rst).  Saying Y
+	  here adds some encryption overhead to all kernel to TPM
+	  transactions.
+
 config HW_RANDOM_TPM
 	bool "TPM HW Random Number Generator support"
 	depends on TCG_TPM && HW_RANDOM && !(TCG_TPM=y && HW_RANDOM=m)
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index ad3594e383e1..4c695b0388f3 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -17,6 +17,7 @@ tpm-y += eventlog/tpm1.o
 tpm-y += eventlog/tpm2.o
 tpm-y += tpm-buf.o
 
+tpm-$(CONFIG_TCG_TPM2_HMAC) += tpm2-sessions.o
 tpm-$(CONFIG_ACPI) += tpm_ppi.o eventlog/acpi.o
 tpm-$(CONFIG_EFI) += eventlog/efi.o
 tpm-$(CONFIG_OF) += eventlog/of.o
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index cbc9d1e2974d..6b8b9956ba69 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -321,4 +321,14 @@ void tpm_bios_log_setup(struct tpm_chip *chip);
 void tpm_bios_log_teardown(struct tpm_chip *chip);
 int tpm_dev_common_init(void);
 void tpm_dev_common_exit(void);
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+int tpm2_sessions_init(struct tpm_chip *chip);
+#else
+static inline int tpm2_sessions_init(struct tpm_chip *chip)
+{
+	return 0;
+}
+#endif
+
 #endif
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 93545be190a5..b0e72fb563d9 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -759,6 +759,11 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 		rc = 0;
 	}
 
+	if (rc)
+		goto out;
+
+	rc = tpm2_sessions_init(chip);
+
 out:
 	/*
 	 * Infineon TPM in field upgrade mode will return no data for the number
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
new file mode 100644
index 000000000000..9fc263ee02c2
--- /dev/null
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -0,0 +1,276 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2018 James.Bottomley@HansenPartnership.com
+ *
+ */
+
+#include "tpm.h"
+
+#include <asm/unaligned.h>
+
+#include <crypto/aes.h>
+
+/* if you change to AES256, you only need change this */
+#define AES_KEYBYTES	AES_KEYSIZE_128
+
+#define AES_KEYBITS	(AES_KEYBYTES*8)
+
+static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
+				     u32 *nullkey)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	off_t offset_r = TPM_HEADER_SIZE, offset_t;
+	u16 len = TPM_HEADER_SIZE;
+	u32 tot_len = be32_to_cpu(head->length);
+	u32 val, parm_len;
+
+	*nullkey = tpm_buf_read_u32(buf, &offset_r);
+	parm_len = tpm_buf_read_u32(buf, &offset_r);
+	/*
+	 * parm_len doesn't include the header, but all the other
+	 * lengths and offsets do, so add it to parm len to make
+	 * the comparisons easier
+	 */
+	parm_len += TPM_HEADER_SIZE;
+
+	if (parm_len + 8 > tot_len)
+		return -EINVAL;
+	len = tpm_buf_read_u16(buf, &offset_r);
+	offset_t = offset_r;
+	/* now we have the public area, compute the name of the object */
+	put_unaligned_be16(TPM_ALG_SHA256, chip->null_key_name);
+	sha256(&buf->data[offset_r], len, chip->null_key_name + 2);
+
+	/* validate the public key */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	/* key type (must be what we asked for) */
+	if (val != TPM_ALG_ECC)
+		return -EINVAL;
+	val = tpm_buf_read_u16(buf, &offset_t);
+	/* name algorithm */
+	if (val != TPM_ALG_SHA256)
+		return -EINVAL;
+	val = tpm_buf_read_u32(buf, &offset_t);
+	/* object properties */
+	if (val != (TPM2_OA_NO_DA |
+		    TPM2_OA_FIXED_TPM |
+		    TPM2_OA_FIXED_PARENT |
+		    TPM2_OA_SENSITIVE_DATA_ORIGIN |
+		    TPM2_OA_USER_WITH_AUTH |
+		    TPM2_OA_DECRYPT |
+		    TPM2_OA_RESTRICTED))
+		return -EINVAL;
+	/* auth policy (empty) */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != 0)
+		return -EINVAL;
+	/* symmetric key parameters */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != TPM_ALG_AES)
+		return -EINVAL;
+	/* symmetric key length */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != AES_KEYBITS)
+		return -EINVAL;
+	/* symmetric encryption scheme */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != TPM_ALG_CFB)
+		return -EINVAL;
+	/* signing scheme */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != TPM_ALG_NULL)
+		return -EINVAL;
+	/* ECC Curve */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != TPM2_ECC_NIST_P256)
+		return -EINVAL;
+	/* KDF Scheme */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != TPM_ALG_NULL)
+		return -EINVAL;
+	/* x point */
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != EC_PT_SZ)
+		return -EINVAL;
+	memcpy(chip->null_ec_key_x, &buf->data[offset_t], val);
+	offset_t += val;
+	val = tpm_buf_read_u16(buf, &offset_t);
+	if (val != EC_PT_SZ)
+		return -EINVAL;
+	memcpy(chip->null_ec_key_y, &buf->data[offset_t], val);
+	offset_t += val;
+
+	/* original length of the whole TPM2B */
+	offset_r += len;
+
+	/* should have exactly consumed the TPM2B public structure */
+	if (offset_t != offset_r)
+		return -EINVAL;
+	if (offset_r > parm_len)
+		return -EINVAL;
+	/* creation data (skip) */
+	len = tpm_buf_read_u16(buf, &offset_r);
+	offset_r += len;
+	if (offset_r > parm_len)
+		return -EINVAL;
+	/* creation digest (must be sha256) */
+	len = tpm_buf_read_u16(buf, &offset_r);
+	offset_r += len;
+	if (len != SHA256_DIGEST_SIZE || offset_r > parm_len)
+		return -EINVAL;
+	/* TPMT_TK_CREATION follows */
+	/* tag, must be TPM_ST_CREATION (0x8021) */
+	val = tpm_buf_read_u16(buf, &offset_r);
+	if (val != TPM2_ST_CREATION || offset_r > parm_len)
+		return -EINVAL;
+	/* hierarchy (must be NULL) */
+	val = tpm_buf_read_u32(buf, &offset_r);
+	if (val != TPM2_RH_NULL || offset_r > parm_len)
+		return -EINVAL;
+	/* the ticket digest HMAC (might not be sha256) */
+	len = tpm_buf_read_u16(buf, &offset_r);
+	offset_r += len;
+	if (offset_r > parm_len)
+		return -EINVAL;
+	/*
+	 * finally we have the name, which is a sha256 digest plus a 2
+	 * byte algorithm type
+	 */
+	len = tpm_buf_read_u16(buf, &offset_r);
+	if (offset_r + len != parm_len + 8)
+		return -EINVAL;
+	if (len != SHA256_DIGEST_SIZE + 2)
+		return -EINVAL;
+
+	if (memcmp(chip->null_key_name, &buf->data[offset_r],
+		   SHA256_DIGEST_SIZE + 2) != 0) {
+		dev_err(&chip->dev, "NULL Seed name comparison failed\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle)
+{
+	int rc;
+	struct tpm_buf buf;
+	struct tpm_buf template;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE_PRIMARY);
+	if (rc)
+		return rc;
+
+	rc = tpm_buf_init_sized(&template);
+	if (rc) {
+		tpm_buf_destroy(&buf);
+		return rc;
+	}
+
+	/*
+	 * create the template.  Note: in order for userspace to
+	 * verify the security of the system, it will have to create
+	 * and certify this NULL primary, meaning all the template
+	 * parameters will have to be identical, so conform exactly to
+	 * the TCG TPM v2.0 Provisioning Guidance for the SRK ECC
+	 * key
+	 */
+
+	/* key type */
+	tpm_buf_append_u16(&template, TPM_ALG_ECC);
+	/* name algorithm */
+	tpm_buf_append_u16(&template, TPM_ALG_SHA256);
+	/* object properties */
+	tpm_buf_append_u32(&template, TPM2_OA_NO_DA |
+			   TPM2_OA_FIXED_TPM |
+			   TPM2_OA_FIXED_PARENT |
+			   TPM2_OA_SENSITIVE_DATA_ORIGIN |
+			   TPM2_OA_USER_WITH_AUTH |
+			   TPM2_OA_DECRYPT |
+			   TPM2_OA_RESTRICTED);
+	/* sauth policy (empty) */
+	tpm_buf_append_u16(&template, 0);
+
+	/* BEGIN parameters: key specific; for ECC*/
+	/* symmetric algorithm */
+	tpm_buf_append_u16(&template, TPM_ALG_AES);
+	/* bits for symmetric algorithm */
+	tpm_buf_append_u16(&template, 128);
+	/* algorithm mode (must be CFB) */
+	tpm_buf_append_u16(&template, TPM_ALG_CFB);
+	/* scheme (NULL means any scheme) */
+	tpm_buf_append_u16(&template, TPM_ALG_NULL);
+	/* ECC Curve ID */
+	tpm_buf_append_u16(&template, TPM2_ECC_NIST_P256);
+	/* KDF Scheme */
+	tpm_buf_append_u16(&template, TPM_ALG_NULL);
+	/* unique: key specific; for ECC it is two points */
+	tpm_buf_append_u16(&template, 0);
+	tpm_buf_append_u16(&template, 0);
+	/* END parameters */
+
+	/* primary handle */
+	tpm_buf_append_u32(&buf, hierarchy);
+	tpm_buf_append_empty_auth(&buf, TPM2_RS_PW);
+	/* sensitive create size is 4 for two empty buffers */
+	tpm_buf_append_u16(&buf, 4);
+	/* sensitive create auth data (empty) */
+	tpm_buf_append_u16(&buf, 0);
+	/* sensitive create sensitive data (empty) */
+	tpm_buf_append_u16(&buf, 0);
+	/* the public template */
+	tpm_buf_append(&buf, template.data, template.length);
+	tpm_buf_destroy(&template);
+	/* outside info (empty) */
+	tpm_buf_append_u16(&buf, 0);
+	/* creation PCR (none) */
+	tpm_buf_append_u32(&buf, 0);
+
+	rc = tpm_transmit_cmd(chip, &buf, 0,
+			      "attempting to create NULL primary");
+
+	if (rc == TPM2_RC_SUCCESS)
+		rc = tpm2_parse_create_primary(chip, &buf, handle);
+
+	tpm_buf_destroy(&buf);
+
+	return rc;
+}
+
+static int tpm2_create_null_primary(struct tpm_chip *chip)
+{
+	u32 nullkey;
+	int rc;
+
+	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey);
+
+	if (rc == TPM2_RC_SUCCESS) {
+		unsigned int offset = 0; /* dummy offset for null key context */
+
+		rc = tpm2_save_context(chip, nullkey, chip->null_key_context,
+				       sizeof(chip->null_key_context), &offset);
+		tpm2_flush_context(chip, nullkey);
+	}
+
+	return rc;
+}
+
+/**
+ * tpm2_sessions_init() - start of day initialization for the sessions code
+ * @chip: TPM chip
+ *
+ * Derive and context save the null primary and allocate memory in the
+ * struct tpm_chip for the authorizations.
+ */
+int tpm2_sessions_init(struct tpm_chip *chip)
+{
+	int rc;
+
+	rc = tpm2_create_null_primary(chip);
+	if (rc)
+		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
+
+	return rc;
+}
+EXPORT_SYMBOL(tpm2_sessions_init);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6be263509e81..3060ab794afb 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -35,12 +35,15 @@ struct trusted_key_options;
 enum tpm_algorithms {
 	TPM_ALG_ERROR		= 0x0000,
 	TPM_ALG_SHA1		= 0x0004,
+	TPM_ALG_AES		= 0x0006,
 	TPM_ALG_KEYEDHASH	= 0x0008,
 	TPM_ALG_SHA256		= 0x000B,
 	TPM_ALG_SHA384		= 0x000C,
 	TPM_ALG_SHA512		= 0x000D,
 	TPM_ALG_NULL		= 0x0010,
 	TPM_ALG_SM3_256		= 0x0012,
+	TPM_ALG_ECC		= 0x0023,
+	TPM_ALG_CFB		= 0x0043,
 };
 
 /*
@@ -49,6 +52,11 @@ enum tpm_algorithms {
  */
 #define TPM_MAX_HASHES	5
 
+enum tpm2_curves {
+	TPM2_ECC_NONE		= 0x0000,
+	TPM2_ECC_NIST_P256	= 0x0003,
+};
+
 struct tpm_digest {
 	u16 alg_id;
 	u8 digest[TPM_MAX_DIGEST_SIZE];
@@ -116,6 +124,20 @@ struct tpm_chip_seqops {
 	const struct seq_operations *seqops;
 };
 
+/* fixed define for the curve we use which is NIST_P256 */
+#define EC_PT_SZ	32
+
+/*
+ * fixed define for the size of a name.  This is actually HASHALG size
+ * plus 2, so 32 for SHA256
+ */
+#define TPM2_NAME_SIZE	34
+
+/*
+ * The maximum size for an object context
+ */
+#define TPM2_MAX_CONTEXT_SIZE 4096
+
 struct tpm_chip {
 	struct device dev;
 	struct device devs;
@@ -170,6 +192,14 @@ struct tpm_chip {
 
 	/* active locality */
 	int locality;
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+	/* details for communication security via sessions */
+	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE]; /* context for NULL seed */
+	u8 null_key_name[TPM2_NAME_SIZE];	 /* name of NULL seed */
+	u8 null_ec_key_x[EC_PT_SZ];
+	u8 null_ec_key_y[EC_PT_SZ];
+#endif
 };
 
 #define TPM_HEADER_SIZE		10
@@ -194,6 +224,7 @@ enum tpm2_timeouts {
 enum tpm2_structures {
 	TPM2_ST_NO_SESSIONS	= 0x8001,
 	TPM2_ST_SESSIONS	= 0x8002,
+	TPM2_ST_CREATION	= 0x8021,
 };
 
 /* Indicates from what layer of the software stack the error comes from */
@@ -243,6 +274,7 @@ enum tpm2_command_codes {
 };
 
 enum tpm2_permanent_handles {
+	TPM2_RH_NULL		= 0x40000007,
 	TPM2_RS_PW		= 0x40000009,
 };
 
@@ -318,7 +350,11 @@ struct tpm_buf {
 enum tpm2_object_attributes {
 	TPM2_OA_FIXED_TPM		= BIT(1),
 	TPM2_OA_FIXED_PARENT		= BIT(4),
+	TPM2_OA_SENSITIVE_DATA_ORIGIN	= BIT(5),
 	TPM2_OA_USER_WITH_AUTH		= BIT(6),
+	TPM2_OA_NO_DA			= BIT(10),
+	TPM2_OA_RESTRICTED		= BIT(16),
+	TPM2_OA_DECRYPT			= BIT(17),
 };
 
 enum tpm2_session_attributes {
@@ -373,6 +409,15 @@ extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
 extern struct tpm_chip *tpm_default_chip(void);
 void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
+static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
+{
+	/* simple authorization for empty auth */
+	tpm_buf_append_u32(buf, 9);		/* total length of auth */
+	tpm_buf_append_u32(buf, handle);
+	tpm_buf_append_u16(buf, 0);		/* nonce len */
+	tpm_buf_append_u8(buf, 0);		/* attributes */
+	tpm_buf_append_u16(buf, 0);		/* hmac len */
+}
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
@@ -399,5 +444,9 @@ static inline struct tpm_chip *tpm_default_chip(void)
 {
 	return NULL;
 }
+
+static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
+{
+}
 #endif
 #endif
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 13/21] tpm: Add HMAC session start and end functions
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (11 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 12/21] tpm: Add NULL primary creation James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:02   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 14/21] tpm: Add HMAC session name/handle append James Bottomley
                   ` (8 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Add session  based HMAC  authentication plus parameter  decryption and
response encryption  using AES. The  basic design is to  segregate all
the nasty crypto, hash and hmac code into tpm2-sessions.c and export a
usable API.  The API first of all starts off by gaining a session with
tpm2_start_auth_session() which  initiates a session with  the TPM and
allocates  an  opaque  tpm2_auth   structure  to  handle  the  session
parameters.  The  design is that  session use will be  single threaded
from start to finish under the ops lock, so the tpm2_auth structure is
stored in struct tpm2_chip to simpify the externally visible API.

The session can be ended with tpm2_end_auth_session() which is
designed only to be used in error legs.  Ordinarily the further
session API (future patches) will end or continue the session
appropriately without having to call this.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts

---

v6: split into new patch, update config variable
v7: add tpm2_ prefix and memzero_explicit
---
 drivers/char/tpm/Kconfig         |   3 +
 drivers/char/tpm/tpm-buf.c       |   1 +
 drivers/char/tpm/tpm-chip.c      |   3 +
 drivers/char/tpm/tpm2-sessions.c | 385 +++++++++++++++++++++++++++++++
 include/linux/tpm.h              |  34 +++
 5 files changed, 426 insertions(+)

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index e3c39a83171b..086cb8588493 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -30,6 +30,9 @@ if TCG_TPM
 config TCG_TPM2_HMAC
 	bool "Use encrypted and HMACd transactions on the TPM bus"
 	default y
+	select CRYPTO_ECDH
+	select CRYPTO_LIB_AESCFB
+	select CRYPTO_LIB_SHA256
 	help
           Setting this causes us to deploy a scheme which uses request
 	  and response HMACs in addition to encryption for
diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index bb81180495d1..274130398569 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -44,6 +44,7 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 	head->tag = cpu_to_be16(tag);
 	head->length = cpu_to_be32(sizeof(*head));
 	head->ordinal = cpu_to_be32(ordinal);
+	buf->handles = 0;
 }
 EXPORT_SYMBOL_GPL(tpm_buf_reset);
 
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 42b1062e33cd..d93937326b2e 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -275,6 +275,9 @@ static void tpm_dev_release(struct device *dev)
 	kfree(chip->work_space.context_buf);
 	kfree(chip->work_space.session_buf);
 	kfree(chip->allocated_banks);
+#ifdef CONFIG_TCG_TPM2_HMAC
+	kfree(chip->auth);
+#endif
 	kfree(chip);
 }
 
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 9fc263ee02c2..c8792a6b8bd4 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -3,18 +3,399 @@
 /*
  * Copyright (C) 2018 James.Bottomley@HansenPartnership.com
  *
+ * Cryptographic helper routines for handling TPM2 sessions for
+ * authorization HMAC and request response encryption.
+ *
+ * The idea is to ensure that every TPM command is HMAC protected by a
+ * session, meaning in-flight tampering would be detected and in
+ * addition all sensitive inputs and responses should be encrypted.
+ *
+ * The basic way this works is to use a TPM feature called salted
+ * sessions where a random secret used in session construction is
+ * encrypted to the public part of a known TPM key.  The problem is we
+ * have no known keys, so initially a primary Elliptic Curve key is
+ * derived from the NULL seed (we use EC because most TPMs generate
+ * these keys much faster than RSA ones).  The curve used is NIST_P256
+ * because that's now mandated to be present in 'TCG TPM v2.0
+ * Provisioning Guidance'
+ *
+ * Threat problems: the initial TPM2_CreatePrimary is not (and cannot
+ * be) session protected, so a clever Man in the Middle could return a
+ * public key they control to this command and from there intercept
+ * and decode all subsequent session based transactions.  The kernel
+ * cannot mitigate this threat but, after boot, userspace can get
+ * proof this has not happened by asking the TPM to certify the NULL
+ * key.  This certification would chain back to the TPM Endorsement
+ * Certificate and prove the NULL seed primary had not been tampered
+ * with and thus all sessions must have been cryptographically secure.
+ * To assist with this, the initial NULL seed public key name is made
+ * available in a sysfs file.
+ *
+ * Use of these functions:
+ *
+ * The design is all the crypto, hash and hmac gunk is confined in this
+ * file and never needs to be seen even by the kernel internal user.  To
+ * the user there's an init function tpm2_sessions_init() that needs to
+ * be called once per TPM which generates the NULL seed primary key.
+ *
+ * These are the usage functions:
+ *
+ * tpm2_start_auth_session() which allocates the opaque auth structure
+ *	and gets a session from the TPM.  This must be called before
+ *	any of the following functions.  The session is protected by a
+ *	session_key which is derived from a random salt value
+ *	encrypted to the NULL seed.
+ * tpm2_end_auth_session() kills the session and frees the resources.
+ *	Under normal operation this function is done by
+ *	tpm_buf_check_hmac_response(), so this is only to be used on
+ *	error legs where the latter is not executed.
  */
 
 #include "tpm.h"
 
+#include <linux/random.h>
+#include <linux/scatterlist.h>
+
 #include <asm/unaligned.h>
 
 #include <crypto/aes.h>
+#include <crypto/kpp.h>
+#include <crypto/ecdh.h>
+#include <crypto/hash.h>
+#include <crypto/hmac.h>
 
 /* if you change to AES256, you only need change this */
 #define AES_KEYBYTES	AES_KEYSIZE_128
 
 #define AES_KEYBITS	(AES_KEYBYTES*8)
+#define AUTH_MAX_NAMES	3
+
+/*
+ * This is the structure that carries all the auth information (like
+ * session handle, nonces, session key and auth) from use to use it is
+ * designed to be opaque to anything outside.
+ */
+struct tpm2_auth {
+	u32 handle;
+	/*
+	 * This has two meanings: before tpm_buf_fill_hmac_session()
+	 * it marks the offset in the buffer of the start of the
+	 * sessions (i.e. after all the handles).  Once the buffer has
+	 * been filled it markes the session number of our auth
+	 * session so we can find it again in the response buffer.
+	 *
+	 * The two cases are distinguished because the first offset
+	 * must always be greater than TPM_HEADER_SIZE and the second
+	 * must be less than or equal to 5.
+	 */
+	u32 session;
+	/*
+	 * the size here is variable and set by the size of our_nonce
+	 * which must be between 16 and the name hash length. we set
+	 * the maximum sha256 size for the greatest protection
+	 */
+	u8 our_nonce[SHA256_DIGEST_SIZE];
+	u8 tpm_nonce[SHA256_DIGEST_SIZE];
+	/*
+	 * the salt is only used across the session command/response
+	 * after that it can be used as a scratch area
+	 */
+	union {
+		u8 salt[EC_PT_SZ];
+		/* scratch for key + IV */
+		u8 scratch[AES_KEYBYTES + AES_BLOCK_SIZE];
+	};
+	u8 session_key[SHA256_DIGEST_SIZE];
+};
+
+/*
+ * It turns out the crypto hmac(sha256) is hard for us to consume
+ * because it assumes a fixed key and the TPM seems to change the key
+ * on every operation, so we weld the hmac init and final functions in
+ * here to give it the same usage characteristics as a regular hash
+ */
+static void hmac_init(struct sha256_state *sctx, u8 *key, int keylen)
+{
+	u8 pad[SHA256_BLOCK_SIZE];
+	int i;
+
+	sha256_init(sctx);
+	for (i = 0; i < sizeof(pad); i++) {
+		if (i < keylen)
+			pad[i] = key[i];
+		else
+			pad[i] = 0;
+		pad[i] ^= HMAC_IPAD_VALUE;
+	}
+	sha256_update(sctx, pad, sizeof(pad));
+}
+
+static void hmac_final(struct sha256_state *sctx, u8 *key, int keylen, u8 *out)
+{
+	u8 pad[SHA256_BLOCK_SIZE];
+	int i;
+
+	for (i = 0; i < sizeof(pad); i++) {
+		if (i < keylen)
+			pad[i] = key[i];
+		else
+			pad[i] = 0;
+		pad[i] ^= HMAC_OPAD_VALUE;
+	}
+
+	/* collect the final hash;  use out as temporary storage */
+	sha256_final(sctx, out);
+
+	sha256_init(sctx);
+	sha256_update(sctx, pad, sizeof(pad));
+	sha256_update(sctx, out, SHA256_DIGEST_SIZE);
+	sha256_final(sctx, out);
+}
+
+/*
+ * assume hash sha256 and nonces u, v of size SHA256_DIGEST_SIZE but
+ * otherwise standard KDFa.  Note output is in bytes not bits.
+ */
+static void KDFa(u8 *key, int keylen, const char *label, u8 *u,
+		 u8 *v, int bytes, u8 *out)
+{
+	u32 counter;
+	const __be32 bits = cpu_to_be32(bytes * 8);
+
+	for (counter = 1; bytes > 0; bytes -= SHA256_DIGEST_SIZE, counter++,
+		     out += SHA256_DIGEST_SIZE) {
+		struct sha256_state sctx;
+		__be32 c = cpu_to_be32(counter);
+
+		hmac_init(&sctx, key, keylen);
+		sha256_update(&sctx, (u8 *)&c, sizeof(c));
+		sha256_update(&sctx, label, strlen(label)+1);
+		sha256_update(&sctx, u, SHA256_DIGEST_SIZE);
+		sha256_update(&sctx, v, SHA256_DIGEST_SIZE);
+		sha256_update(&sctx, (u8 *)&bits, sizeof(bits));
+		hmac_final(&sctx, key, keylen, out);
+	}
+}
+
+/*
+ * Somewhat of a bastardization of the real KDFe.  We're assuming
+ * we're working with known point sizes for the input parameters and
+ * the hash algorithm is fixed at sha256.  Because we know that the
+ * point size is 32 bytes like the hash size, there's no need to loop
+ * in this KDF.
+ */
+static void KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
+		 u8 *keyout)
+{
+	struct sha256_state sctx;
+	/*
+	 * this should be an iterative counter, but because we know
+	 *  we're only taking 32 bytes for the point using a sha256
+	 *  hash which is also 32 bytes, there's only one loop
+	 */
+	__be32 c = cpu_to_be32(1);
+
+	sha256_init(&sctx);
+	/* counter (BE) */
+	sha256_update(&sctx, (u8 *)&c, sizeof(c));
+	/* secret value */
+	sha256_update(&sctx, z, EC_PT_SZ);
+	/* string including trailing zero */
+	sha256_update(&sctx, str, strlen(str)+1);
+	sha256_update(&sctx, pt_u, EC_PT_SZ);
+	sha256_update(&sctx, pt_v, EC_PT_SZ);
+	sha256_final(&sctx, keyout);
+}
+
+static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
+{
+	struct crypto_kpp *kpp;
+	struct kpp_request *req;
+	struct scatterlist s[2], d[1];
+	struct ecdh p = {0};
+	u8 encoded_key[EC_PT_SZ], *x, *y;
+	unsigned int buf_len;
+
+	/* secret is two sized points */
+	tpm_buf_append_u16(buf, (EC_PT_SZ + 2)*2);
+	/*
+	 * we cheat here and append uninitialized data to form
+	 * the points.  All we care about is getting the two
+	 * co-ordinate pointers, which will be used to overwrite
+	 * the uninitialized data
+	 */
+	tpm_buf_append_u16(buf, EC_PT_SZ);
+	x = &buf->data[tpm_buf_length(buf)];
+	tpm_buf_append(buf, encoded_key, EC_PT_SZ);
+	tpm_buf_append_u16(buf, EC_PT_SZ);
+	y = &buf->data[tpm_buf_length(buf)];
+	tpm_buf_append(buf, encoded_key, EC_PT_SZ);
+	sg_init_table(s, 2);
+	sg_set_buf(&s[0], x, EC_PT_SZ);
+	sg_set_buf(&s[1], y, EC_PT_SZ);
+
+	kpp = crypto_alloc_kpp("ecdh-nist-p256", CRYPTO_ALG_INTERNAL, 0);
+	if (IS_ERR(kpp)) {
+		dev_err(&chip->dev, "crypto ecdh allocation failed\n");
+		return;
+	}
+
+	buf_len = crypto_ecdh_key_len(&p);
+	if (sizeof(encoded_key) < buf_len) {
+		dev_err(&chip->dev, "salt buffer too small needs %d\n",
+			buf_len);
+		goto out;
+	}
+	crypto_ecdh_encode_key(encoded_key, buf_len, &p);
+	/* this generates a random private key */
+	crypto_kpp_set_secret(kpp, encoded_key, buf_len);
+
+	/* salt is now the public point of this private key */
+	req = kpp_request_alloc(kpp, GFP_KERNEL);
+	if (!req)
+		goto out;
+	kpp_request_set_input(req, NULL, 0);
+	kpp_request_set_output(req, s, EC_PT_SZ*2);
+	crypto_kpp_generate_public_key(req);
+	/*
+	 * we're not done: now we have to compute the shared secret
+	 * which is our private key multiplied by the tpm_key public
+	 * point, we actually only take the x point and discard the y
+	 * point and feed it through KDFe to get the final secret salt
+	 */
+	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
+	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
+	kpp_request_set_input(req, s, EC_PT_SZ*2);
+	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
+	kpp_request_set_output(req, d, EC_PT_SZ);
+	crypto_kpp_compute_shared_secret(req);
+	kpp_request_free(req);
+
+	/*
+	 * pass the shared secret through KDFe for salt. Note salt
+	 * area is used both for input shared secret and output salt.
+	 * This works because KDFe fully consumes the secret before it
+	 * writes the salt
+	 */
+	KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
+	     chip->auth->salt);
+ out:
+	crypto_free_kpp(kpp);
+}
+/**
+ * tpm2_end_auth_session() - kill the allocated auth session
+ * @chip: the TPM chip structure
+ *
+ * ends the session started by tpm2_start_auth_session and frees all
+ * the resources.  Under normal conditions,
+ * tpm_buf_check_hmac_response() will correctly end the session if
+ * required, so this function is only for use in error legs that will
+ * bypass the normal invocation of tpm_buf_check_hmac_response().
+ */
+void tpm2_end_auth_session(struct tpm_chip *chip)
+{
+	tpm2_flush_context(chip, chip->auth->handle);
+	memzero_explicit(chip->auth, sizeof(*chip->auth));
+}
+EXPORT_SYMBOL(tpm2_end_auth_session);
+
+static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
+					 struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	u32 tot_len = be32_to_cpu(head->length);
+	off_t offset = TPM_HEADER_SIZE;
+	u32 val;
+
+	/* we're starting after the header so adjust the length */
+	tot_len -= TPM_HEADER_SIZE;
+
+	/* should have handle plus nonce */
+	if (tot_len != 4 + 2 + sizeof(auth->tpm_nonce))
+		return -EINVAL;
+
+	auth->handle = tpm_buf_read_u32(buf, &offset);
+	val = tpm_buf_read_u16(buf, &offset);
+	if (val != sizeof(auth->tpm_nonce))
+		return -EINVAL;
+	memcpy(auth->tpm_nonce, &buf->data[offset], sizeof(auth->tpm_nonce));
+	/* now compute the session key from the nonces */
+	KDFa(auth->salt, sizeof(auth->salt), "ATH", auth->tpm_nonce,
+	     auth->our_nonce, sizeof(auth->session_key), auth->session_key);
+
+	return 0;
+}
+
+/**
+ * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
+ * @chip: the TPM chip structure to create the session with
+ *
+ * This function loads the NULL seed from its saved context and starts
+ * an authentication session on the null seed, fills in the
+ * @chip->auth structure to contain all the session details necessary
+ * for performing the HMAC, encrypt and decrypt operations and
+ * returns.  The NULL seed is flushed before this function returns.
+ *
+ * Return: zero on success or actual error encountered.
+ */
+int tpm2_start_auth_session(struct tpm_chip *chip)
+{
+	struct tpm_buf buf;
+	struct tpm2_auth *auth = chip->auth;
+	int rc;
+	unsigned int offset = 0; /* dummy offset for null seed context */
+	u32 nullkey;
+
+	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
+			       &nullkey);
+	if (rc)
+		goto out;
+
+	auth->session = TPM_HEADER_SIZE;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
+	if (rc)
+		goto out;
+
+	/* salt key handle */
+	tpm_buf_append_u32(&buf, nullkey);
+	/* bind key handle */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* nonce caller */
+	get_random_bytes(auth->our_nonce, sizeof(auth->our_nonce));
+	tpm_buf_append_u16(&buf, sizeof(auth->our_nonce));
+	tpm_buf_append(&buf, auth->our_nonce, sizeof(auth->our_nonce));
+
+	/* append encrypted salt and squirrel away unencrypted in auth */
+	tpm_buf_append_salt(&buf, chip);
+	/* session type (HMAC, audit or policy) */
+	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
+
+	/* symmetric encryption parameters */
+	/* symmetric algorithm */
+	tpm_buf_append_u16(&buf, TPM_ALG_AES);
+	/* bits for symmetric algorithm */
+	tpm_buf_append_u16(&buf, AES_KEYBITS);
+	/* symmetric algorithm mode (must be CFB) */
+	tpm_buf_append_u16(&buf, TPM_ALG_CFB);
+	/* hash algorithm for session */
+	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
+
+	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
+	tpm2_flush_context(chip, nullkey);
+
+	if (rc == TPM2_RC_SUCCESS)
+		rc = tpm2_parse_start_auth_session(auth, &buf);
+
+	tpm_buf_destroy(&buf);
+
+	if (rc)
+		goto out;
+
+ out:
+	return rc;
+}
+EXPORT_SYMBOL(tpm2_start_auth_session);
 
 static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
 				     u32 *nullkey)
@@ -271,6 +652,10 @@ int tpm2_sessions_init(struct tpm_chip *chip)
 	if (rc)
 		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
 
+	chip->auth = kmalloc(sizeof(*chip->auth), GFP_KERNEL);
+	if (!chip->auth)
+		return -ENOMEM;
+
 	return rc;
 }
 EXPORT_SYMBOL(tpm2_sessions_init);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 3060ab794afb..444f0a83682a 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -30,6 +30,14 @@
 struct tpm_chip;
 struct trusted_key_payload;
 struct trusted_key_options;
+/* opaque structure, holds auth session parameters like the session key */
+struct tpm2_auth;
+
+enum tpm2_session_types {
+	TPM2_SE_HMAC	= 0x00,
+	TPM2_SE_POLICY	= 0x01,
+	TPM2_SE_TRIAL	= 0x02,
+};
 
 /* if you add a new hash to this, increment TPM_MAX_HASHES below */
 enum tpm_algorithms {
@@ -199,6 +207,7 @@ struct tpm_chip {
 	u8 null_key_name[TPM2_NAME_SIZE];	 /* name of NULL seed */
 	u8 null_ec_key_x[EC_PT_SZ];
 	u8 null_ec_key_y[EC_PT_SZ];
+	struct tpm2_auth *auth;
 #endif
 };
 
@@ -262,6 +271,7 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
 	TPM2_CC_GET_CAPABILITY	        = 0x017A,
 	TPM2_CC_GET_RANDOM	        = 0x017B,
@@ -345,20 +355,30 @@ struct tpm_buf {
 	u32 flags;
 	u32 length;
 	u8 *data;
+	u8 handles;
 };
 
 enum tpm2_object_attributes {
 	TPM2_OA_FIXED_TPM		= BIT(1),
+	TPM2_OA_ST_CLEAR		= BIT(2),
 	TPM2_OA_FIXED_PARENT		= BIT(4),
 	TPM2_OA_SENSITIVE_DATA_ORIGIN	= BIT(5),
 	TPM2_OA_USER_WITH_AUTH		= BIT(6),
+	TPM2_OA_ADMIN_WITH_POLICY	= BIT(7),
 	TPM2_OA_NO_DA			= BIT(10),
+	TPM2_OA_ENCRYPTED_DUPLICATION	= BIT(11),
 	TPM2_OA_RESTRICTED		= BIT(16),
 	TPM2_OA_DECRYPT			= BIT(17),
+	TPM2_OA_SIGN			= BIT(18),
 };
 
 enum tpm2_session_attributes {
 	TPM2_SA_CONTINUE_SESSION	= BIT(0),
+	TPM2_SA_AUDIT_EXCLUSIVE		= BIT(1),
+	TPM2_SA_AUDIT_RESET		= BIT(3),
+	TPM2_SA_DECRYPT			= BIT(5),
+	TPM2_SA_ENCRYPT			= BIT(6),
+	TPM2_SA_AUDIT			= BIT(7),
 };
 
 struct tpm2_hash {
@@ -449,4 +469,18 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
 {
 }
 #endif
+#ifdef CONFIG_TCG_TPM2_HMAC
+
+int tpm2_start_auth_session(struct tpm_chip *chip);
+void tpm2_end_auth_session(struct tpm_chip *chip);
+#else
+static inline int tpm2_start_auth_session(struct tpm_chip *chip)
+{
+	return 0;
+}
+static inline void tpm2_end_auth_session(struct tpm_chip *chip)
+{
+}
+#endif	/* CONFIG_TCG_TPM2_HMAC */
+
 #endif
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 14/21] tpm: Add HMAC session name/handle append
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (12 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 13/21] tpm: Add HMAC session start and end functions James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:06   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 15/21] tpm: Add the rest of the session HMAC API James Bottomley
                   ` (7 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Add tpm2_append_name() for appending to the handle area of the TPM
command.  When TPM_BUS_SECURITY is enabled and HMAC sessions are in
use this adds the standard u32 handle to the buffer but additionally
records the name of the object which must be used as part of the HMAC
computation.  The name of certain object types (volatile and permanent
handles and NV indexes) is a hash of the public area of the object.
Since this hash is not known ahead of time, it must be requested from
the TPM using TPM2_ReadPublic() (which cannot be HMAC protected, but
if an interposer lies about it, the HMAC check will fail and the
problem will be detected).

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts

---

v6: split into new patch, update config variable
v7: add tpm2_ prefix
---
 drivers/char/tpm/tpm2-sessions.c | 121 +++++++++++++++++++++++++++++++
 include/linux/tpm.h              |  26 +++++++
 2 files changed, 147 insertions(+)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index c8792a6b8bd4..9eb420d8e530 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -49,6 +49,11 @@
  *	Under normal operation this function is done by
  *	tpm_buf_check_hmac_response(), so this is only to be used on
  *	error legs where the latter is not executed.
+ * tpm_buf_append_name() to add a handle to the buffer.  This must be
+ *	used in place of the usual tpm_buf_append_u32() for adding
+ *	handles because handles have to be processed specially when
+ *	calculating the HMAC.  In particular, for NV, volatile and
+ *	permanent objects you now need to provide the name.
  */
 
 #include "tpm.h"
@@ -106,8 +111,26 @@ struct tpm2_auth {
 		u8 scratch[AES_KEYBYTES + AES_BLOCK_SIZE];
 	};
 	u8 session_key[SHA256_DIGEST_SIZE];
+	/* 3 names of handles: name_h is handle, name is name of handle */
+	u32 name_h[AUTH_MAX_NAMES];
+	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
 };
 
+/*
+ * Name Size based on TPM algorithm (assumes no hash bigger than 255)
+ */
+static u8 name_size(const u8 *name)
+{
+	static u8 size_map[] = {
+		[TPM_ALG_SHA1] = SHA1_DIGEST_SIZE,
+		[TPM_ALG_SHA256] = SHA256_DIGEST_SIZE,
+		[TPM_ALG_SHA384] = SHA384_DIGEST_SIZE,
+		[TPM_ALG_SHA512] = SHA512_DIGEST_SIZE,
+	};
+	u16 alg = get_unaligned_be16(name);
+	return size_map[alg] + 2;
+}
+
 /*
  * It turns out the crypto hmac(sha256) is hard for us to consume
  * because it assumes a fixed key and the TPM seems to change the key
@@ -282,6 +305,104 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
  out:
 	crypto_free_kpp(kpp);
 }
+
+static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	off_t offset = TPM_HEADER_SIZE;
+	u32 tot_len = be32_to_cpu(head->length);
+	u32 val;
+
+	/* we're starting after the header so adjust the length */
+	tot_len -= TPM_HEADER_SIZE;
+
+	/* skip public */
+	val = tpm_buf_read_u16(buf, &offset);
+	if (val > tot_len)
+		return -EINVAL;
+	offset += val;
+	/* name */
+	val = tpm_buf_read_u16(buf, &offset);
+	if (val != name_size(&buf->data[offset]))
+		return -EINVAL;
+	memcpy(name, &buf->data[offset], val);
+	/* forget the rest */
+	return 0;
+}
+
+static int tpm2_readpublic(struct tpm_chip *chip, u32 handle, char *name)
+{
+	struct tpm_buf buf;
+	int rc;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
+	if (rc)
+		return rc;
+
+	tpm_buf_append_u32(&buf, handle);
+	rc = tpm_transmit_cmd(chip, &buf, 0, "read public");
+	if (rc == TPM2_RC_SUCCESS)
+		rc = tpm2_parse_read_public(name, &buf);
+
+	tpm_buf_destroy(&buf);
+
+	return rc;
+}
+
+/**
+ * tpm_buf_append_name() - add a handle area to the buffer
+ * @chip: the TPM chip structure
+ * @buf: The buffer to be appended
+ * @handle: The handle to be appended
+ * @name: The name of the handle (may be NULL)
+ *
+ * In order to compute session HMACs, we need to know the names of the
+ * objects pointed to by the handles.  For most objects, this is simly
+ * the actual 4 byte handle or an empty buf (in these cases @name
+ * should be NULL) but for volatile objects, permanent objects and NV
+ * areas, the name is defined as the hash (according to the name
+ * algorithm which should be set to sha256) of the public area to
+ * which the two byte algorithm id has been appended.  For these
+ * objects, the @name pointer should point to this.  If a name is
+ * required but @name is NULL, then TPM2_ReadPublic() will be called
+ * on the handle to obtain the name.
+ *
+ * As with most tpm_buf operations, success is assumed because failure
+ * will be caused by an incorrect programming model and indicated by a
+ * kernel message.
+ */
+void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
+			 u32 handle, u8 *name)
+{
+	int slot;
+	enum tpm2_mso_type mso = tpm2_handle_mso(handle);
+	struct tpm2_auth *auth = chip->auth;
+
+	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE)/4;
+	if (slot >= AUTH_MAX_NAMES) {
+		dev_err(&chip->dev, "TPM: too many handles\n");
+		return;
+	}
+	WARN(auth->session != tpm_buf_length(buf),
+	     "name added in wrong place\n");
+	tpm_buf_append_u32(buf, handle);
+	auth->session += 4;
+
+	if (mso == TPM2_MSO_PERSISTENT ||
+	    mso == TPM2_MSO_VOLATILE ||
+	    mso == TPM2_MSO_NVRAM) {
+		if (!name)
+			tpm2_readpublic(chip, handle, auth->name[slot]);
+	} else {
+		if (name)
+			dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
+	}
+
+	auth->name_h[slot] = handle;
+	if (name)
+		memcpy(auth->name[slot], name, name_size(name));
+}
+EXPORT_SYMBOL(tpm_buf_append_name);
 /**
  * tpm2_end_auth_session() - kill the allocated auth session
  * @chip: the TPM chip structure
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 444f0a83682a..9b0b0d3c0d62 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -271,6 +271,7 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_READ_PUBLIC		= 0x0173,
 	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
 	TPM2_CC_GET_CAPABILITY	        = 0x017A,
@@ -288,6 +289,21 @@ enum tpm2_permanent_handles {
 	TPM2_RS_PW		= 0x40000009,
 };
 
+/* Most Significant Octet for key types  */
+enum tpm2_mso_type {
+	TPM2_MSO_NVRAM		= 0x01,
+	TPM2_MSO_SESSION	= 0x02,
+	TPM2_MSO_POLICY		= 0x03,
+	TPM2_MSO_PERMANENT	= 0x40,
+	TPM2_MSO_VOLATILE	= 0x80,
+	TPM2_MSO_PERSISTENT	= 0x81,
+};
+
+static inline enum tpm2_mso_type tpm2_handle_mso(u32 handle)
+{
+	return handle >> 24;
+}
+
 enum tpm2_capabilities {
 	TPM2_CAP_HANDLES	= 1,
 	TPM2_CAP_COMMANDS	= 2,
@@ -472,6 +488,8 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
 #ifdef CONFIG_TCG_TPM2_HMAC
 
 int tpm2_start_auth_session(struct tpm_chip *chip);
+void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
+			 u32 handle, u8 *name);
 void tpm2_end_auth_session(struct tpm_chip *chip);
 #else
 static inline int tpm2_start_auth_session(struct tpm_chip *chip)
@@ -481,6 +499,14 @@ static inline int tpm2_start_auth_session(struct tpm_chip *chip)
 static inline void tpm2_end_auth_session(struct tpm_chip *chip)
 {
 }
+static inline void tpm_buf_append_name(struct tpm_chip *chip,
+				       struct tpm_buf *buf,
+				       u32 handle, u8 *name)
+{
+	tpm_buf_append_u32(buf, handle);
+	/* count the number of handles in the upper bits of flags */
+	buf->handles++;
+}
 #endif	/* CONFIG_TCG_TPM2_HMAC */
 
 #endif
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 15/21] tpm: Add the rest of the session HMAC API
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (13 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 14/21] tpm: Add HMAC session name/handle append James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:10   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 16/21] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
                   ` (6 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

The final pieces of the HMAC API are for manipulating the session area
of the command.  To add an authentication HMAC session
tpm_buf_append_hmac_session() is called where tpm2_append_auth() would
go. If a non empty password is passed in, this is correctly added to
the HMAC to prove knowledge of it without revealing it.  Note that if
the session is only used to encrypt or decrypt parameters (no
authentication) then tpm_buf_append_hmac_session_opt() must be used
instead.  This functions identically to tpm_buf_append_hmac_session()
when TPM_BUS_SECURITY is enabled, but differently when it isn't,
because effectively nothing is appended to the session area.

Next the parameters should be filled in for the command and finally
tpm_buf_fill_hmac_session() is called immediatly prior to transmitting
the command which computes the correct HMAC and places it in the
command at the session location in the tpm buffer

Finally, after tpm_transmit_cmd() is called,
tpm_buf_check_hmac_response() is called to check that the returned
HMAC matched and collect the new state for the next use of the
session, if any.

The features of the session are controlled by the session attributes
set in tpm_buf_append_hmac_session().  If TPM2_SA_CONTINUE_SESSION is
not specified, the session will be flushed and the tpm2_auth structure
freed in tpm_buf_check_hmac_response(); otherwise the session may be
used again.  Parameter encryption is specified by or'ing the flag
TPM2_SA_DECRYPT and response encryption by or'ing the flag
TPM2_SA_ENCRYPT.  the various encryptions will be taken care of by
tpm_buf_fill_hmac_session() and tpm_buf_check_hmac_response()
respectively.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts

---

v6: split into new patch, update config variable
v7: add memzero_explicit
---
 drivers/char/tpm/tpm2-sessions.c | 400 +++++++++++++++++++++++++++++++
 include/linux/tpm.h              |  69 ++++++
 2 files changed, 469 insertions(+)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 9eb420d8e530..9d6da0c9652f 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -54,6 +54,18 @@
  *	handles because handles have to be processed specially when
  *	calculating the HMAC.  In particular, for NV, volatile and
  *	permanent objects you now need to provide the name.
+ * tpm_buf_append_hmac_session() which appends the hmac session to the
+ *	buf in the same way tpm_buf_append_auth does().
+ * tpm_buf_fill_hmac_session() This calculates the correct hash and
+ *	places it in the buffer.  It must be called after the complete
+ *	command buffer is finalized so it can fill in the correct HMAC
+ *	based on the parameters.
+ * tpm_buf_check_hmac_response() which checks the session response in
+ *	the buffer and calculates what it should be.  If there's a
+ *	mismatch it will log a warning and return an error.  If
+ *	tpm_buf_append_hmac_session() did not specify
+ *	TPM_SA_CONTINUE_SESSION then the session will be closed (if it
+ *	hasn't been consumed) and the auth structure freed.
  */
 
 #include "tpm.h"
@@ -110,7 +122,23 @@ struct tpm2_auth {
 		/* scratch for key + IV */
 		u8 scratch[AES_KEYBYTES + AES_BLOCK_SIZE];
 	};
+	/*
+	 * the session key and passphrase are the same size as the
+	 * name digest (sha256 again).  The session key is constant
+	 * for the use of the session and the passphrase can change
+	 * with every invocation.
+	 *
+	 * Note: these fields must be adjacent and in this order
+	 * because several HMAC/KDF schemes use the combination of the
+	 * session_key and passphrase.
+	 */
 	u8 session_key[SHA256_DIGEST_SIZE];
+	u8 passphrase[SHA256_DIGEST_SIZE];
+	int passphraselen;
+	struct crypto_aes_ctx aes_ctx;
+	/* saved session attributes */
+	u8 attrs;
+	__be32 ordinal;
 	/* 3 names of handles: name_h is handle, name is name of handle */
 	u32 name_h[AUTH_MAX_NAMES];
 	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
@@ -306,6 +334,230 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
 	crypto_free_kpp(kpp);
 }
 
+/**
+ * tpm_buf_append_hmac_session() - append a TPM session element
+ * @chip: the TPM chip structure
+ * @buf: The buffer to be appended
+ * @attributes: The session attributes
+ * @passphrase: The session authority (NULL if none)
+ * @passphraselen: The length of the session authority (0 if none)
+ *
+ * This fills in a session structure in the TPM command buffer, except
+ * for the HMAC which cannot be computed until the command buffer is
+ * complete.  The type of session is controlled by the @attributes,
+ * the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
+ * session won't terminate after tpm_buf_check_hmac_response(),
+ * TPM2_SA_DECRYPT which means this buffers first parameter should be
+ * encrypted with a session key and TPM2_SA_ENCRYPT, which means the
+ * response buffer's first parameter needs to be decrypted (confusing,
+ * but the defines are written from the point of view of the TPM).
+ *
+ * Any session appended by this command must be finalized by calling
+ * tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
+ * and the TPM will reject the command.
+ *
+ * As with most tpm_buf operations, success is assumed because failure
+ * will be caused by an incorrect programming model and indicated by a
+ * kernel message.
+ */
+void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
+				 u8 attributes, u8 *passphrase,
+				 int passphraselen)
+{
+	u8 nonce[SHA256_DIGEST_SIZE];
+	u32 len;
+	struct tpm2_auth *auth = chip->auth;
+
+	/*
+	 * The Architecture Guide requires us to strip trailing zeros
+	 * before computing the HMAC
+	 */
+	while (passphrase && passphraselen > 0
+	       && passphrase[passphraselen - 1] == '\0')
+		passphraselen--;
+
+	auth->attrs = attributes;
+	auth->passphraselen = passphraselen;
+	if (passphraselen)
+		memcpy(auth->passphrase, passphrase, passphraselen);
+
+	if (auth->session != tpm_buf_length(buf)) {
+		/* we're not the first session */
+		len = get_unaligned_be32(&buf->data[auth->session]);
+		if (4 + len + auth->session != tpm_buf_length(buf)) {
+			WARN(1, "session length mismatch, cannot append");
+			return;
+		}
+
+		/* add our new session */
+		len += 9 + 2 * SHA256_DIGEST_SIZE;
+		put_unaligned_be32(len, &buf->data[auth->session]);
+	} else {
+		tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
+	}
+
+	/* random number for our nonce */
+	get_random_bytes(nonce, sizeof(nonce));
+	memcpy(auth->our_nonce, nonce, sizeof(nonce));
+	tpm_buf_append_u32(buf, auth->handle);
+	/* our new nonce */
+	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
+	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
+	tpm_buf_append_u8(buf, auth->attrs);
+	/* and put a placeholder for the hmac */
+	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
+	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
+}
+EXPORT_SYMBOL(tpm_buf_append_hmac_session);
+
+/**
+ * tpm_buf_fill_hmac_session() - finalize the session HMAC
+ * @chip: the TPM chip structure
+ * @buf: The buffer to be appended
+ *
+ * This command must not be called until all of the parameters have
+ * been appended to @buf otherwise the computed HMAC will be
+ * incorrect.
+ *
+ * This function computes and fills in the session HMAC using the
+ * session key and, if TPM2_SA_DECRYPT was specified, computes the
+ * encryption key and encrypts the first parameter of the command
+ * buffer with it.
+ *
+ * As with most tpm_buf operations, success is assumed because failure
+ * will be caused by an incorrect programming model and indicated by a
+ * kernel message.
+ */
+void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
+{
+	u32 cc, handles, val;
+	struct tpm2_auth *auth = chip->auth;
+	int i;
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	off_t offset_s = TPM_HEADER_SIZE, offset_p;
+	u8 *hmac = NULL;
+	u32 attrs;
+	u8 cphash[SHA256_DIGEST_SIZE];
+	struct sha256_state sctx;
+
+	/* save the command code in BE format */
+	auth->ordinal = head->ordinal;
+
+	cc = be32_to_cpu(head->ordinal);
+
+	i = tpm2_find_cc(chip, cc);
+	if (i < 0) {
+		dev_err(&chip->dev, "Command 0x%x not found in TPM\n", cc);
+		return;
+	}
+	attrs = chip->cc_attrs_tbl[i];
+
+	handles = (attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0);
+
+	/*
+	 * just check the names, it's easy to make mistakes.  This
+	 * would happen if someone added a handle via
+	 * tpm_buf_append_u32() instead of tpm_buf_append_name()
+	 */
+	for (i = 0; i < handles; i++) {
+		u32 handle = tpm_buf_read_u32(buf, &offset_s);
+
+		if (auth->name_h[i] != handle) {
+			dev_err(&chip->dev, "TPM: handle %d wrong for name\n",
+				  i);
+			return;
+		}
+	}
+	/* point offset_s to the start of the sessions */
+	val = tpm_buf_read_u32(buf, &offset_s);
+	/* point offset_p to the start of the parameters */
+	offset_p = offset_s + val;
+	for (i = 1; offset_s < offset_p; i++) {
+		u32 handle = tpm_buf_read_u32(buf, &offset_s);
+		u16 len;
+		u8 a;
+
+		/* nonce (already in auth) */
+		len = tpm_buf_read_u16(buf, &offset_s);
+		offset_s += len;
+
+		a = tpm_buf_read_u8(buf, &offset_s);
+
+		len = tpm_buf_read_u16(buf, &offset_s);
+		if (handle == auth->handle && auth->attrs == a) {
+			hmac = &buf->data[offset_s];
+			/*
+			 * save our session number so we know which
+			 * session in the response belongs to us
+			 */
+			auth->session = i;
+		}
+
+		offset_s += len;
+	}
+	if (offset_s != offset_p) {
+		dev_err(&chip->dev, "TPM session length is incorrect\n");
+		return;
+	}
+	if (!hmac) {
+		dev_err(&chip->dev, "TPM could not find HMAC session\n");
+		return;
+	}
+
+	/* encrypt before HMAC */
+	if (auth->attrs & TPM2_SA_DECRYPT) {
+		u16 len;
+
+		/* need key and IV */
+		KDFa(auth->session_key, SHA256_DIGEST_SIZE
+		     + auth->passphraselen, "CFB", auth->our_nonce,
+		     auth->tpm_nonce, AES_KEYBYTES + AES_BLOCK_SIZE,
+		     auth->scratch);
+
+		len = tpm_buf_read_u16(buf, &offset_p);
+		aes_expandkey(&auth->aes_ctx, auth->scratch, AES_KEYBYTES);
+		aescfb_encrypt(&auth->aes_ctx, &buf->data[offset_p],
+			       &buf->data[offset_p], len,
+			       auth->scratch + AES_KEYBYTES);
+		/* reset p to beginning of parameters for HMAC */
+		offset_p -= 2;
+	}
+
+	sha256_init(&sctx);
+	/* ordinal is already BE */
+	sha256_update(&sctx, (u8 *)&head->ordinal, sizeof(head->ordinal));
+	/* add the handle names */
+	for (i = 0; i < handles; i++) {
+		enum tpm2_mso_type mso = tpm2_handle_mso(auth->name_h[i]);
+
+		if (mso == TPM2_MSO_PERSISTENT ||
+		    mso == TPM2_MSO_VOLATILE ||
+		    mso == TPM2_MSO_NVRAM) {
+			sha256_update(&sctx, auth->name[i],
+				      name_size(auth->name[i]));
+		} else {
+			__be32 h = cpu_to_be32(auth->name_h[i]);
+
+			sha256_update(&sctx, (u8 *)&h, 4);
+		}
+	}
+	if (offset_s != tpm_buf_length(buf))
+		sha256_update(&sctx, &buf->data[offset_s],
+			      tpm_buf_length(buf) - offset_s);
+	sha256_final(&sctx, cphash);
+
+	/* now calculate the hmac */
+	hmac_init(&sctx, auth->session_key, sizeof(auth->session_key)
+		  + auth->passphraselen);
+	sha256_update(&sctx, cphash, sizeof(cphash));
+	sha256_update(&sctx, auth->our_nonce, sizeof(auth->our_nonce));
+	sha256_update(&sctx, auth->tpm_nonce, sizeof(auth->tpm_nonce));
+	sha256_update(&sctx, &auth->attrs, 1);
+	hmac_final(&sctx, auth->session_key, sizeof(auth->session_key)
+		   + auth->passphraselen, hmac);
+}
+EXPORT_SYMBOL(tpm_buf_fill_hmac_session);
+
 static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
@@ -403,6 +655,154 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 		memcpy(auth->name[slot], name, name_size(name));
 }
 EXPORT_SYMBOL(tpm_buf_append_name);
+
+/**
+ * tpm_buf_check_hmac_response() - check the TPM return HMAC for correctness
+ * @chip: the TPM chip structure
+ * @buf: the original command buffer (which now contains the response)
+ * @rc: the return code from tpm_transmit_cmd
+ *
+ * If @rc is non zero, @buf may not contain an actual return, so @rc
+ * is passed through as the return and the session cleaned up and
+ * de-allocated if required (this is required if
+ * TPM2_SA_CONTINUE_SESSION was not specified as a session flag).
+ *
+ * If @rc is zero, the response HMAC is computed against the returned
+ * @buf and matched to the TPM one in the session area.  If there is a
+ * mismatch, an error is logged and -EINVAL returned.
+ *
+ * The reason for this is that the command issue and HMAC check
+ * sequence should look like:
+ *
+ *	rc = tpm_transmit_cmd(...);
+ *	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
+ *	if (rc)
+ *		...
+ *
+ * Which is easily layered into the current contrl flow.
+ *
+ * Returns: 0 on success or an error.
+ */
+int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
+				int rc)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	struct tpm2_auth *auth = chip->auth;
+	off_t offset_s, offset_p;
+	u8 rphash[SHA256_DIGEST_SIZE];
+	u32 attrs;
+	struct sha256_state sctx;
+	u16 tag = be16_to_cpu(head->tag);
+	u32 cc = be32_to_cpu(auth->ordinal);
+	int parm_len, len, i, handles;
+
+	if (auth->session >= TPM_HEADER_SIZE) {
+		WARN(1, "tpm session not filled correctly\n");
+		goto out;
+	}
+
+	if (rc != 0)
+		/* pass non success rc through and close the session */
+		goto out;
+
+	rc = -EINVAL;
+	if (tag != TPM2_ST_SESSIONS) {
+		dev_err(&chip->dev, "TPM: HMAC response check has no sessions tag\n");
+		goto out;
+	}
+
+	i = tpm2_find_cc(chip, cc);
+	if (i < 0)
+		goto out;
+	attrs = chip->cc_attrs_tbl[i];
+	handles = (attrs >> TPM2_CC_ATTR_RHANDLE) & 1;
+
+	/* point to area beyond handles */
+	offset_s = TPM_HEADER_SIZE + handles * 4;
+	parm_len = tpm_buf_read_u32(buf, &offset_s);
+	offset_p = offset_s;
+	offset_s += parm_len;
+	/* skip over any sessions before ours */
+	for (i = 0; i < auth->session - 1; i++) {
+		len = tpm_buf_read_u16(buf, &offset_s);
+		offset_s += len + 1;
+		len = tpm_buf_read_u16(buf, &offset_s);
+		offset_s += len;
+	}
+	/* TPM nonce */
+	len = tpm_buf_read_u16(buf, &offset_s);
+	if (offset_s + len > tpm_buf_length(buf))
+		goto out;
+	if (len != SHA256_DIGEST_SIZE)
+		goto out;
+	memcpy(auth->tpm_nonce, &buf->data[offset_s], len);
+	offset_s += len;
+	attrs = tpm_buf_read_u8(buf, &offset_s);
+	len = tpm_buf_read_u16(buf, &offset_s);
+	if (offset_s + len != tpm_buf_length(buf))
+		goto out;
+	if (len != SHA256_DIGEST_SIZE)
+		goto out;
+	/*
+	 * offset_s points to the HMAC. now calculate comparison, beginning
+	 * with rphash
+	 */
+	sha256_init(&sctx);
+	/* yes, I know this is now zero, but it's what the standard says */
+	sha256_update(&sctx, (u8 *)&head->return_code,
+		      sizeof(head->return_code));
+	/* ordinal is already BE */
+	sha256_update(&sctx, (u8 *)&auth->ordinal, sizeof(auth->ordinal));
+	sha256_update(&sctx, &buf->data[offset_p], parm_len);
+	sha256_final(&sctx, rphash);
+
+	/* now calculate the hmac */
+	hmac_init(&sctx, auth->session_key, sizeof(auth->session_key)
+		  + auth->passphraselen);
+	sha256_update(&sctx, rphash, sizeof(rphash));
+	sha256_update(&sctx, auth->tpm_nonce, sizeof(auth->tpm_nonce));
+	sha256_update(&sctx, auth->our_nonce, sizeof(auth->our_nonce));
+	sha256_update(&sctx, &auth->attrs, 1);
+	/* we're done with the rphash, so put our idea of the hmac there */
+	hmac_final(&sctx, auth->session_key, sizeof(auth->session_key)
+		   + auth->passphraselen, rphash);
+	if (memcmp(rphash, &buf->data[offset_s], SHA256_DIGEST_SIZE) == 0) {
+		rc = 0;
+	} else {
+		dev_err(&chip->dev, "TPM: HMAC check failed\n");
+		goto out;
+	}
+
+	/* now do response decryption */
+	if (auth->attrs & TPM2_SA_ENCRYPT) {
+		/* need key and IV */
+		KDFa(auth->session_key, SHA256_DIGEST_SIZE
+		     + auth->passphraselen, "CFB", auth->tpm_nonce,
+		     auth->our_nonce, AES_KEYBYTES + AES_BLOCK_SIZE,
+		     auth->scratch);
+
+		len = tpm_buf_read_u16(buf, &offset_p);
+		aes_expandkey(&auth->aes_ctx, auth->scratch, AES_KEYBYTES);
+		aescfb_decrypt(&auth->aes_ctx, &buf->data[offset_p],
+			       &buf->data[offset_p], len,
+			       auth->scratch + AES_KEYBYTES);
+	}
+
+ out:
+	if ((auth->attrs & TPM2_SA_CONTINUE_SESSION) == 0) {
+		if (rc)
+			/* manually close the session if it wasn't consumed */
+			tpm2_flush_context(chip, auth->handle);
+		memzero_explicit(auth, sizeof(*auth));
+	} else {
+		/* reset for next use  */
+		auth->session = TPM_HEADER_SIZE;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL(tpm_buf_check_hmac_response);
+
 /**
  * tpm2_end_auth_session() - kill the allocated auth session
  * @chip: the TPM chip structure
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 9b0b0d3c0d62..9c608fac8935 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -490,8 +490,25 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
 int tpm2_start_auth_session(struct tpm_chip *chip);
 void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 			 u32 handle, u8 *name);
+void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
+				 u8 attributes, u8 *passphrase,
+				 int passphraselen);
+static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
+						   struct tpm_buf *buf,
+						   u8 attributes,
+						   u8 *passphrase,
+						   int passphraselen)
+{
+	tpm_buf_append_hmac_session(chip, buf, attributes, passphrase,
+				    passphraselen);
+}
+void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf);
+int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
+				int rc);
 void tpm2_end_auth_session(struct tpm_chip *chip);
 #else
+#include <asm/unaligned.h>
+
 static inline int tpm2_start_auth_session(struct tpm_chip *chip)
 {
 	return 0;
@@ -507,6 +524,58 @@ static inline void tpm_buf_append_name(struct tpm_chip *chip,
 	/* count the number of handles in the upper bits of flags */
 	buf->handles++;
 }
+static inline void tpm_buf_append_hmac_session(struct tpm_chip *chip,
+					       struct tpm_buf *buf,
+					       u8 attributes, u8 *passphrase,
+					       int passphraselen)
+{
+	/* offset tells us where the sessions area begins */
+	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
+	u32 len = 9 + passphraselen;
+
+	if (tpm_buf_length(buf) != offset) {
+		/* not the first session so update the existing length */
+		len += get_unaligned_be32(&buf->data[offset]);
+		put_unaligned_be32(len, &buf->data[offset]);
+	} else {
+		tpm_buf_append_u32(buf, len);
+	}
+	/* auth handle */
+	tpm_buf_append_u32(buf, TPM2_RS_PW);
+	/* nonce */
+	tpm_buf_append_u16(buf, 0);
+	/* attributes */
+	tpm_buf_append_u8(buf, 0);
+	/* passphrase */
+	tpm_buf_append_u16(buf, passphraselen);
+	tpm_buf_append(buf, passphrase, passphraselen);
+}
+static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
+						   struct tpm_buf *buf,
+						   u8 attributes,
+						   u8 *passphrase,
+						   int passphraselen)
+{
+	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
+	struct tpm_header *head = (struct tpm_header *) buf->data;
+
+	/*
+	 * if the only sessions are optional, the command tag
+	 * must change to TPM2_ST_NO_SESSIONS
+	 */
+	if (tpm_buf_length(buf) == offset)
+		head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
+}
+static inline void tpm_buf_fill_hmac_session(struct tpm_chip *chip,
+					     struct tpm_buf *buf)
+{
+}
+static inline int tpm_buf_check_hmac_response(struct tpm_chip *chip,
+					      struct tpm_buf *buf,
+					      int rc)
+{
+	return rc;
+}
 #endif	/* CONFIG_TCG_TPM2_HMAC */
 
 #endif
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 16/21] tpm: add hmac checks to tpm2_pcr_extend()
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (14 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 15/21] tpm: Add the rest of the session HMAC API James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:10   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 17/21] tpm: add session encryption protection to tpm2_get_random() James Bottomley
                   ` (5 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

tpm2_pcr_extend() is used by trusted keys to extend a PCR to prevent a
key from being re-loaded until the next reboot.  To use this
functionality securely, that extend must be protected by a session
hmac.  This patch adds HMAC protection so tampering with the
tpm2_pcr_extend() command in flight is detected.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---
v7: add review
---
 drivers/char/tpm/tpm2-cmd.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index b0e72fb563d9..a53a843294ed 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -216,13 +216,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 	return rc;
 }
 
-struct tpm2_null_auth_area {
-	__be32  handle;
-	__be16  nonce_size;
-	u8  attributes;
-	__be16  auth_size;
-} __packed;
-
 /**
  * tpm2_pcr_extend() - extend a PCR value
  *
@@ -236,24 +229,22 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 		    struct tpm_digest *digests)
 {
 	struct tpm_buf buf;
-	struct tpm2_null_auth_area auth_area;
 	int rc;
 	int i;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
+	rc = tpm2_start_auth_session(chip);
 	if (rc)
 		return rc;
 
-	tpm_buf_append_u32(&buf, pcr_idx);
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
+	if (rc) {
+		tpm2_end_auth_session(chip);
+		return rc;
+	}
 
-	auth_area.handle = cpu_to_be32(TPM2_RS_PW);
-	auth_area.nonce_size = 0;
-	auth_area.attributes = 0;
-	auth_area.auth_size = 0;
+	tpm_buf_append_name(chip, &buf, pcr_idx, NULL);
+	tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0);
 
-	tpm_buf_append_u32(&buf, sizeof(struct tpm2_null_auth_area));
-	tpm_buf_append(&buf, (const unsigned char *)&auth_area,
-		       sizeof(auth_area));
 	tpm_buf_append_u32(&buf, chip->nr_allocated_banks);
 
 	for (i = 0; i < chip->nr_allocated_banks; i++) {
@@ -262,7 +253,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 			       chip->allocated_banks[i].digest_size);
 	}
 
+	tpm_buf_fill_hmac_session(chip, &buf);
 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value");
+	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
 
 	tpm_buf_destroy(&buf);
 
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 17/21] tpm: add session encryption protection to tpm2_get_random()
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (15 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 16/21] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:10   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 18/21] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
                   ` (4 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

If some entity is snooping the TPM bus, they can see the random
numbers we're extracting from the TPM and do prediction attacks
against their consumers.  Foil this attack by using response
encryption to prevent the attacker from seeing the random sequence.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---
v7: add review
---
 drivers/char/tpm/tpm2-cmd.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index a53a843294ed..0cdf892ec2a7 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -292,25 +292,35 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	if (!num_bytes || max > TPM_MAX_RNG_DATA)
 		return -EINVAL;
 
-	err = tpm_buf_init(&buf, 0, 0);
+	err = tpm2_start_auth_session(chip);
 	if (err)
 		return err;
 
+	err = tpm_buf_init(&buf, 0, 0);
+	if (err) {
+		tpm2_end_auth_session(chip);
+		return err;
+	}
+
 	do {
-		tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
+		tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
+		tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT
+						| TPM2_SA_CONTINUE_SESSION,
+						NULL, 0);
 		tpm_buf_append_u16(&buf, num_bytes);
+		tpm_buf_fill_hmac_session(chip, &buf);
 		err = tpm_transmit_cmd(chip, &buf,
 				       offsetof(struct tpm2_get_random_out,
 						buffer),
 				       "attempting get random");
+		err = tpm_buf_check_hmac_response(chip, &buf, err);
 		if (err) {
 			if (err > 0)
 				err = -EIO;
 			goto out;
 		}
 
-		out = (struct tpm2_get_random_out *)
-			&buf.data[TPM_HEADER_SIZE];
+		out = (struct tpm2_get_random_out *)tpm_buf_parameters(&buf);
 		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
 		if (tpm_buf_length(&buf) <
 		    TPM_HEADER_SIZE +
@@ -327,9 +337,12 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	} while (retries-- && total < max);
 
 	tpm_buf_destroy(&buf);
+	tpm2_end_auth_session(chip);
+
 	return total ? total : -EIO;
 out:
 	tpm_buf_destroy(&buf);
+	tpm2_end_auth_session(chip);
 	return err;
 }
 
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 18/21] KEYS: trusted: Add session encryption protection to the seal/unseal path
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (16 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 17/21] tpm: add session encryption protection to tpm2_get_random() James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:11   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 19/21] tpm: add the null key name as a sysfs export James Bottomley
                   ` (3 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

If some entity is snooping the TPM bus, the can see the data going in
to be sealed and the data coming out as it is unsealed.  Add parameter
and response encryption to these cases to ensure that no secrets are
leaked even if the bus is snooped.

As part of doing this conversion it was discovered that policy
sessions can't work with HMAC protected authority because of missing
pieces (the tpm Nonce).  I've added code to work the same way as
before, which will result in potential authority exposure (while still
adding security for the command and the returned blob), and a fixme to
redo the API to get rid of this security hole.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---
v2: fix unseal with policy and password
v3: fix session memory leak
v7: add review
---
 security/keys/trusted-keys/trusted_tpm2.c | 88 ++++++++++++++++-------
 1 file changed, 61 insertions(+), 27 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 97b1dfca2dba..dfeec06301ce 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -253,26 +253,26 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (rc)
 		return rc;
 
+	rc = tpm2_start_auth_session(chip);
+	if (rc)
+		goto out_put;
+
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	if (rc) {
-		tpm_put_ops(chip);
-		return rc;
+		tpm2_end_auth_session(chip);
+		goto out_put;
 	}
 
 	rc = tpm_buf_init_sized(&sized);
 	if (rc) {
 		tpm_buf_destroy(&buf);
-		tpm_put_ops(chip);
-		return rc;
+		tpm2_end_auth_session(chip);
+		goto out_put;
 	}
 
-	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
-	tpm_buf_append_u32(&buf, options->keyhandle);
-	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
-			     NULL /* nonce */, 0,
-			     0 /* session_attributes */,
-			     options->keyauth /* hmac */,
-			     TPM_DIGEST_SIZE);
+	tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
+	tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT,
+				    options->keyauth, TPM_DIGEST_SIZE);
 
 	/* sensitive */
 	tpm_buf_append_u16(&sized, options->blobauth_len);
@@ -314,10 +314,13 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;
+		tpm2_end_auth_session(chip);
 		goto out;
 	}
 
+	tpm_buf_fill_hmac_session(chip, &buf);
 	rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data");
+	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
 	if (rc)
 		goto out;
 
@@ -348,6 +351,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	else
 		payload->blob_len = blob_len;
 
+out_put:
 	tpm_put_ops(chip);
 	return rc;
 }
@@ -417,25 +421,31 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
+	rc = tpm2_start_auth_session(chip);
 	if (rc)
 		return rc;
 
-	tpm_buf_append_u32(&buf, options->keyhandle);
-	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
-			     NULL /* nonce */, 0,
-			     0 /* session_attributes */,
-			     options->keyauth /* hmac */,
-			     TPM_DIGEST_SIZE);
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
+	if (rc) {
+		tpm2_end_auth_session(chip);
+		return rc;
+	}
+
+	tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
+	tpm_buf_append_hmac_session(chip, &buf, 0, options->keyauth,
+				    TPM_DIGEST_SIZE);
 
 	tpm_buf_append(&buf, blob, blob_len);
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;
+		tpm2_end_auth_session(chip);
 		goto out;
 	}
 
+	tpm_buf_fill_hmac_session(chip, &buf);
 	rc = tpm_transmit_cmd(chip, &buf, 4, "loading blob");
+	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
 	if (!rc)
 		*blob_handle = be32_to_cpup(
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
@@ -473,20 +483,44 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	u8 *data;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	rc = tpm2_start_auth_session(chip);
 	if (rc)
 		return rc;
 
-	tpm_buf_append_u32(&buf, blob_handle);
-	tpm2_buf_append_auth(&buf,
-			     options->policyhandle ?
-			     options->policyhandle : TPM2_RS_PW,
-			     NULL /* nonce */, 0,
-			     TPM2_SA_CONTINUE_SESSION,
-			     options->blobauth /* hmac */,
-			     options->blobauth_len);
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	if (rc) {
+		tpm2_end_auth_session(chip);
+		return rc;
+	}
+
+	tpm_buf_append_name(chip, &buf, blob_handle, NULL);
+
+	if (!options->policyhandle) {
+		tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT,
+					    options->blobauth,
+					    options->blobauth_len);
+	} else {
+		/*
+		 * FIXME: The policy session was generated outside the
+		 * kernel so we don't known the nonce and thus can't
+		 * calculate a HMAC on it.  Therefore, the user can
+		 * only really use TPM2_PolicyPassword and we must
+		 * send down the plain text password, which could be
+		 * intercepted.  We can still encrypt the returned
+		 * key, but that's small comfort since the interposer
+		 * could repeat our actions with the exfiltrated
+		 * password.
+		 */
+		tpm2_buf_append_auth(&buf, options->policyhandle,
+				     NULL /* nonce */, 0, 0,
+				     options->blobauth, options->blobauth_len);
+		tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT,
+						NULL, 0);
+	}
 
+	tpm_buf_fill_hmac_session(chip, &buf);
 	rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
+	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
 	if (rc > 0)
 		rc = -EPERM;
 
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 19/21] tpm: add the null key name as a sysfs export
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (17 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 18/21] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 17:15   ` Jarkko Sakkinen
  2024-02-13 17:13 ` [PATCH v7 20/21] Documentation: add tpm-security.rst James Bottomley
                   ` (2 subsequent siblings)
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

This is the last component of encrypted tpm2 session handling that
allows us to verify from userspace that the key derived from the NULL
seed genuinely belongs to the TPM and has not been spoofed.

The procedure for doing this involves creating an attestation identity
key (which requires verification of the TPM EK certificate) and then
using that AIK to sign a certification of the Elliptic Curve key over
the NULL seed.  Userspace must create this EC Key using the parameters
prescribed in TCG TPM v2.0 Provisioning Guidance for the SRK ECC; if
this is done correctly the names will match and the TPM can then run a
TPM2_Certify operation on this derived primary key using the newly
created AIK.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---
v6: change config name
v7: add review
---
 drivers/char/tpm/tpm-sysfs.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index 54c71473aa29..94231f052ea7 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -309,6 +309,21 @@ static ssize_t tpm_version_major_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(tpm_version_major);
 
+#ifdef CONFIG_TCG_TPM2_HMAC
+static ssize_t null_name_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct tpm_chip *chip = to_tpm_chip(dev);
+	int size = TPM2_NAME_SIZE;
+
+	bin2hex(buf, chip->null_key_name, size);
+	size *= 2;
+	buf[size++] = '\n';
+	return size;
+}
+static DEVICE_ATTR_RO(null_name);
+#endif
+
 static struct attribute *tpm1_dev_attrs[] = {
 	&dev_attr_pubek.attr,
 	&dev_attr_pcrs.attr,
@@ -326,6 +341,9 @@ static struct attribute *tpm1_dev_attrs[] = {
 
 static struct attribute *tpm2_dev_attrs[] = {
 	&dev_attr_tpm_version_major.attr,
+#ifdef CONFIG_TCG_TPM2_HMAC
+	&dev_attr_null_name.attr,
+#endif
 	NULL
 };
 
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 20/21] Documentation: add tpm-security.rst
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (18 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 19/21] tpm: add the null key name as a sysfs export James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-13 17:13 ` [PATCH v7 21/21] tpm: disable the TPM if NULL name changes James Bottomley
  2024-02-14  0:13 ` [PATCH v7 00/21] add integrity and security to TPM2 transactions Jarkko Sakkinen
  21 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Document how the new encrypted secure interface for TPM2 works and how
security can be assured after boot by certifying the NULL seed.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

---
v7: add review
---
 Documentation/security/tpm/tpm-security.rst | 216 ++++++++++++++++++++
 1 file changed, 216 insertions(+)
 create mode 100644 Documentation/security/tpm/tpm-security.rst

diff --git a/Documentation/security/tpm/tpm-security.rst b/Documentation/security/tpm/tpm-security.rst
new file mode 100644
index 000000000000..4f633f251033
--- /dev/null
+++ b/Documentation/security/tpm/tpm-security.rst
@@ -0,0 +1,216 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+TPM Security
+============
+
+The object of this document is to describe how we make the kernel's
+use of the TPM reasonably robust in the face of external snooping and
+packet alteration attacks (called passive and active interposer attack
+in the literature).  The current security document is for TPM 2.0.
+
+Introduction
+------------
+
+The TPM is usually a discrete chip attached to a PC via some type of
+low bandwidth bus.  There are exceptions to this such as the Intel
+PTT, which is a software TPM running inside a software environment
+close to the CPU, which are subject to different attacks, but right at
+the moment, most hardened security environments require a discrete
+hardware TPM, which is the use case discussed here.
+
+Snooping and Alteration Attacks against the bus
+-----------------------------------------------
+
+The current state of the art for snooping the `TPM Genie`_ hardware
+interposer which is a simple external device that can be installed in
+a couple of seconds on any system or laptop.  Recently attacks were
+successfully demonstrated against the `Windows Bitlocker TPM`_ system.
+Most recently the same `attack against TPM based Linux disk
+encryption`_ schemes.  The next phase of research seems to be hacking
+existing devices on the bus to act as interposers, so the fact that
+the attacker requires physical access for a few seconds might
+evaporate.  However, the goal of this document is to protect TPM
+secrets and integrity as far as we are able in this environment and to
+try to insure that if we can't prevent the attack then at least we can
+detect it.
+
+Unfortunately, most of the TPM functionality, including the hardware
+reset capability can be controlled by an attacker who has access to
+the bus, so we'll discuss some of the disruption possibilities below.
+
+Measurement (PCR) Integrity
+---------------------------
+
+Since the attacker can send their own commands to the TPM, they can
+send arbitrary PCR extends and thus disrupt the measurement system,
+which would be an annoying denial of service attack.  However, there
+are two, more serious, classes of attack aimed at entities sealed to
+trust measurements.
+
+1. The attacker could intercept all PCR extends coming from the system
+   and completely substitute their own values, producing a replay of
+   an untampered state that would cause PCR measurements to attest to
+   a trusted state and release secrets
+
+2. At some point in time the attacker could reset the TPM, clearing
+   the PCRs and then send down their own measurements which would
+   effectively overwrite the boot time measurements the TPM has
+   already done.
+
+The first can be thwarted by always doing HMAC protection of the PCR
+extend and read command meaning measurement values cannot be
+substituted without producing a detectable HMAC failure in the
+response.  However, the second can only really be detected by relying
+on some sort of mechanism for protection which would change over TPM
+reset.
+
+Secrets Guarding
+----------------
+
+Certain information passing in and out of the TPM, such as key sealing
+and private key import and random number generation, is vulnerable to
+interception which HMAC protection alone cannot protect against, so
+for these types of command we must also employ request and response
+encryption to prevent the loss of secret information.
+
+Establishing Initial Trust with the TPM
+---------------------------------------
+
+In order to provide security from the beginning, an initial shared or
+asymmetric secret must be established which must also be unknown to
+the attacker.  The most obvious avenues for this are the endorsement
+and storage seeds, which can be used to derive asymmetric keys.
+However, using these keys is difficult because the only way to pass
+them into the kernel would be on the command line, which requires
+extensive support in the boot system, and there's no guarantee that
+either hierarchy would not have some type of authorization.
+
+The mechanism chosen for the Linux Kernel is to derive the primary
+elliptic curve key from the null seed using the standard storage seed
+parameters.  The null seed has two advantages: firstly the hierarchy
+physically cannot have an authorization, so we are always able to use
+it and secondly, the null seed changes across TPM resets, meaning if
+we establish trust on the null seed at start of day, all sessions
+salted with the derived key will fail if the TPM is reset and the seed
+changes.
+
+Obviously using the null seed without any other prior shared secrets,
+we have to create and read the initial public key which could, of
+course, be intercepted and substituted by the bus interposer.
+However, the TPM has a key certification mechanism (using the EK
+endorsement certificate, creating an attestation identity key and
+certifying the null seed primary with that key) which is too complex
+to run within the kernel, so we keep a copy of the null primary key
+name, which is what is exported via sysfs so user-space can run the
+full certification when it boots.  The definitive guarantee here is
+that if the null primary key certifies correctly, you know all your
+TPM transactions since start of day were secure and if it doesn't, you
+know there's an interposer on your system (and that any secret used
+during boot may have been leaked).
+
+Stacking Trust
+--------------
+
+In the current null primary scenario, the TPM must be completely
+cleared before handing it on to the next consumer.  However the kernel
+hands to user-space the name of the derived null seed key which can
+then be verified by certification in user-space.  Therefore, this chain
+of name handoff can be used between the various boot components as
+well (via an unspecified mechanism).  For instance, grub could use the
+null seed scheme for security and hand the name off to the kernel in
+the boot area.  The kernel could make its own derivation of the key
+and the name and know definitively that if they differ from the handed
+off version that tampering has occurred.  Thus it becomes possible to
+chain arbitrary boot components together (UEFI to grub to kernel) via
+the name handoff provided each successive component knows how to
+collect the name and verifies it against its derived key.
+
+Session Properties
+------------------
+
+All TPM commands the kernel uses allow sessions.  HMAC sessions may be
+used to check the integrity of requests and responses and decrypt and
+encrypt flags may be used to shield parameters and responses.  The
+HMAC and encryption keys are usually derived from the shared
+authorization secret, but for a lot of kernel operations that is well
+known (and usually empty).  Thus, every HMAC session used by the
+kernel must be created using the null primary key as the salt key
+which thus provides a cryptographic input into the session key
+derivation.  Thus, the kernel creates the null primary key once (as a
+volatile TPM handle) and keeps it around in a saved context stored in
+tpm_chip for every in-kernel use of the TPM.  Currently, because of a
+lack of de-gapping in the in-kernel resource manager, the session must
+be created and destroyed for each operation, but, in future, a single
+session may also be reused for the in-kernel HMAC, encryption and
+decryption sessions.
+
+Protection Types
+----------------
+
+For every in-kernel operation we use null primary salted HMAC to
+protect the integrity.  Additionally, we use parameter encryption to
+protect key sealing and parameter decryption to protect key unsealing
+and random number generation.
+
+Null Primary Key Certification in Userspace
+===========================================
+
+Every TPM comes shipped with a couple of X.509 certificates for the
+primary endorsement key.  This document assumes that the Elliptic
+Curve version of the certificate exists at 01C00002, but will work
+equally well with the RSA certificate (at 01C00001).
+
+The first step in the certification is primary creation using the
+template from the `TCG EK Credential Profile`_ which allows comparison
+of the generated primary key against the one in the certificate (the
+public key must match).  Note that generation of the EK primary
+requires the EK hierarchy password, but a pre-generated version of the
+EC primary should exist at 81010002 and a TPM2_ReadPublic() may be
+performed on this without needing the key authority.  Next, the
+certificate itself must be verified to chain back to the manufacturer
+root (which should be published on the manufacturer website).  Once
+this is done, an attestation key (AK) is generated within the TPM and
+it's name and the EK public key can be used to encrypt a secret using
+TPM2_MakeCredential.  The TPM then runs TPM2_ActivateCredential which
+will only recover the secret if the binding between the TPM, the EK
+and the AK is true. the generated AK may now be used to run a
+certification of the null primary key whose name the kernel has
+exported.  Since TPM2_MakeCredential/ActivateCredential are somewhat
+complicated, a more simplified process involving an externally
+generated private key is described below.
+
+This process is a simplified abbreviation of the usual privacy CA
+based attestation process.  The assumption here is that the
+attestation is done by the TPM owner who thus has access to only the
+owner hierarchy.  The owner creates an external public/private key
+pair (assume elliptic curve in this case) and wraps the private key
+for import using an inner wrapping process and parented to the EC
+derived storage primary.  The TPM2_Import() is done using a parameter
+decryption HMAC session salted to the EK primary (which also does not
+require the EK key authority) meaning that the inner wrapping key is
+the encrypted parameter and thus the TPM will not be able to perform
+the import unless is possesses the certified EK so if the command
+succeeds and the HMAC verifies on return we know we have a loadable
+copy of the private key only for the certified TPM.  This key is now
+loaded into the TPM and the Storage primary flushed (to free up space
+for the null key generation).
+
+The null EC primary is now generated using the Storage profile
+outlined in the `TCG TPM v2.0 Provisioning Guidance`_; the name of
+this key (the hash of the public area) is computed and compared to the
+null seed name presented by the kernel in
+/sys/class/tpm/tpm0/null_name.  If the names do not match, the TPM is
+compromised.  If the names match, the user performs a TPM2_Certify()
+using the null primary as the object handle and the loaded private key
+as the sign handle and providing randomized qualifying data.  The
+signature of the returned certifyInfo is verified against the public
+part of the loaded private key and the qualifying data checked to
+prevent replay.  If all of these tests pass, the user is now assured
+that TPM integrity and privacy was preserved across the entire boot
+sequence of this kernel.
+
+.. _TPM Genie: https://www.nccgroup.trust/globalassets/about-us/us/documents/tpm-genie.pdf
+.. _Windows Bitlocker TPM: https://dolosgroup.io/blog/2021/7/9/from-stolen-laptop-to-inside-the-company-network
+.. _attack against TPM based Linux disk encryption: https://www.secura.com/blog/tpm-sniffing-attacks-against-non-bitlocker-targets
+.. _TCG EK Credential Profile: https://trustedcomputinggroup.org/resource/tcg-ek-credential-profile-for-tpm-family-2-0/
+.. _TCG TPM v2.0 Provisioning Guidance: https://trustedcomputinggroup.org/resource/tcg-tpm-v2-0-provisioning-guidance/
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* [PATCH v7 21/21] tpm: disable the TPM if NULL name changes
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (19 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 20/21] Documentation: add tpm-security.rst James Bottomley
@ 2024-02-13 17:13 ` James Bottomley
  2024-02-23 18:43   ` Jarkko Sakkinen
  2024-02-14  0:13 ` [PATCH v7 00/21] add integrity and security to TPM2 transactions Jarkko Sakkinen
  21 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-02-13 17:13 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Update tpm2_load_context() to return -EINVAL on integrity failures and
use this as a signal when loading the NULL context that something
might be wrong.  If the signal fails, check the name of the NULL
primary against the one stored in the chip data and if there is a
mismatch disable the TPM because it is likely to have suffered a reset
attack.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-chip.c      |  3 ++
 drivers/char/tpm/tpm2-sessions.c | 65 ++++++++++++++++++++++++++------
 drivers/char/tpm/tpm2-space.c    |  3 ++
 include/linux/tpm.h              |  4 +-
 4 files changed, 62 insertions(+), 13 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index d93937326b2e..854546000c92 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -158,6 +158,9 @@ int tpm_try_get_ops(struct tpm_chip *chip)
 {
 	int rc = -EIO;
 
+	if (chip->flags & TPM_CHIP_FLAG_DISABLE)
+		return rc;
+
 	get_device(&chip->dev);
 
 	down_read(&chip->ops_sem);
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 9d6da0c9652f..60a1a8746563 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -87,6 +87,9 @@
 #define AES_KEYBITS	(AES_KEYBYTES*8)
 #define AUTH_MAX_NAMES	3
 
+static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
+			       u32 *handle, u8 *name);
+
 /*
  * This is the structure that carries all the auth information (like
  * session handle, nonces, session key and auth) from use to use it is
@@ -847,6 +850,37 @@ static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
 	return 0;
 }
 
+static int tpm2_load_null(struct tpm_chip *chip, u32 *nullkey)
+{
+	int rc;
+	unsigned int offset = 0; /* dummy offset for null seed context */
+	u8 name[SHA256_DIGEST_SIZE + 2];
+
+	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
+			       nullkey);
+	if (rc != -EINVAL)
+		return rc;
+
+	/* an integrity failure may mean the TPM has been reset */
+	dev_err(&chip->dev, "NULL key integrity failure!\n");
+	/* check the null name against what we know */
+	tpm2_create_primary(chip, TPM2_RH_NULL, NULL, name);
+	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0)
+		/* name unchanged, assume transient integrity failure */
+		return rc;
+	/*
+	 * Fatal TPM failure: the NULL seed has actually changed, so
+	 * the TPM must have been illegally reset.  All in-kernel TPM
+	 * operations will fail because the NULL primary can't be
+	 * loaded to salt the sessions, but disable the TPM anyway so
+	 * userspace programms can't be compromised by it.
+	 */
+	dev_err(&chip->dev, "NULL name has changed, disabling TPM due to interference\n");
+	chip->flags |= TPM_CHIP_FLAG_DISABLE;
+
+	return rc;
+}
+
 /**
  * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
  * @chip: the TPM chip structure to create the session with
@@ -864,11 +898,9 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	struct tpm_buf buf;
 	struct tpm2_auth *auth = chip->auth;
 	int rc;
-	unsigned int offset = 0; /* dummy offset for null seed context */
 	u32 nullkey;
 
-	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
-			       &nullkey);
+	rc = tpm2_load_null(chip, &nullkey);
 	if (rc)
 		goto out;
 
@@ -919,15 +951,19 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 EXPORT_SYMBOL(tpm2_start_auth_session);
 
 static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
-				     u32 *nullkey)
+				     u32 *handle, u8 *name)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
 	off_t offset_r = TPM_HEADER_SIZE, offset_t;
 	u16 len = TPM_HEADER_SIZE;
 	u32 tot_len = be32_to_cpu(head->length);
-	u32 val, parm_len;
+	u32 val, parm_len, keyhandle;
+	keyhandle = tpm_buf_read_u32(buf, &offset_r);
+	if (handle)
+		*handle = keyhandle;
+	else
+		tpm2_flush_context(chip, keyhandle);
 
-	*nullkey = tpm_buf_read_u32(buf, &offset_r);
 	parm_len = tpm_buf_read_u32(buf, &offset_r);
 	/*
 	 * parm_len doesn't include the header, but all the other
@@ -940,9 +976,12 @@ static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
 		return -EINVAL;
 	len = tpm_buf_read_u16(buf, &offset_r);
 	offset_t = offset_r;
-	/* now we have the public area, compute the name of the object */
-	put_unaligned_be16(TPM_ALG_SHA256, chip->null_key_name);
-	sha256(&buf->data[offset_r], len, chip->null_key_name + 2);
+	if (name) {
+		/* now we have the public area, compute the name of
+		 * the object */
+		put_unaligned_be16(TPM_ALG_SHA256, name);
+		sha256(&buf->data[offset_r], len, name + 2);
+	}
 
 	/* validate the public key */
 	val = tpm_buf_read_u16(buf, &offset_t);
@@ -1054,7 +1093,8 @@ static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
 	return 0;
 }
 
-static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle)
+static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
+			       u32 *handle, u8 *name)
 {
 	int rc;
 	struct tpm_buf buf;
@@ -1133,7 +1173,7 @@ static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle
 			      "attempting to create NULL primary");
 
 	if (rc == TPM2_RC_SUCCESS)
-		rc = tpm2_parse_create_primary(chip, &buf, handle);
+		rc = tpm2_parse_create_primary(chip, &buf, handle, name);
 
 	tpm_buf_destroy(&buf);
 
@@ -1145,7 +1185,8 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
 	u32 nullkey;
 	int rc;
 
-	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey);
+	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey,
+				 chip->null_key_name);
 
 	if (rc == TPM2_RC_SUCCESS) {
 		unsigned int offset = 0; /* dummy offset for null key context */
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 24479a81c23c..4892d491da8d 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -105,6 +105,9 @@ int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
 		*handle = 0;
 		tpm_buf_destroy(&tbuf);
 		return -ENOENT;
+	} else if (tpm2_rc_value(rc) == TPM2_RC_INTEGRITY) {
+		tpm_buf_destroy(&tbuf);
+		return -EINVAL;
 	} else if (rc > 0) {
 		dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
 			 __func__, rc);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 9c608fac8935..4474dabfb69d 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -244,6 +244,7 @@ enum tpm2_return_codes {
 	TPM2_RC_SUCCESS		= 0x0000,
 	TPM2_RC_HASH		= 0x0083, /* RC_FMT1 */
 	TPM2_RC_HANDLE		= 0x008B,
+	TPM2_RC_INTEGRITY	= 0x009F,
 	TPM2_RC_INITIALIZE	= 0x0100, /* RC_VER1 */
 	TPM2_RC_FAILURE		= 0x0101,
 	TPM2_RC_DISABLED	= 0x0120,
@@ -342,6 +343,7 @@ enum tpm_chip_flags {
 	TPM_CHIP_FLAG_FIRMWARE_UPGRADE		= BIT(7),
 	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
 	TPM_CHIP_FLAG_HWRNG_DISABLED		= BIT(9),
+	TPM_CHIP_FLAG_DISABLE			= BIT(10),
 };
 
 #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
@@ -428,7 +430,7 @@ static inline bool tpm_is_firmware_upgrade(struct tpm_chip *chip)
 
 static inline u32 tpm2_rc_value(u32 rc)
 {
-	return (rc & BIT(7)) ? rc & 0xff : rc;
+	return (rc & BIT(7)) ? rc & 0xbf : rc;
 }
 
 #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 00/21] add integrity and security to TPM2 transactions
  2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
                   ` (20 preceding siblings ...)
  2024-02-13 17:13 ` [PATCH v7 21/21] tpm: disable the TPM if NULL name changes James Bottomley
@ 2024-02-14  0:13 ` Jarkko Sakkinen
  21 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-14  0:13 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> The interest in securing the TPM against interposers, both active and
> passive has risen to fever pitch with the demonstration of key
> recovery against windows bitlocker:
>
> https://dolosgroup.io/blog/2021/7/9/from-stolen-laptop-to-inside-the-company-network
>
> And subsequently the same attack being successful against all the
> Linux TPM based security solutions:
>
> https://www.secura.com/blog/tpm-sniffing-attacks-against-non-bitlocker-targets
>
> The attacks fall into two categories:
>
> 1. Passive Interposers, which sit on the bus and merely observe
> 2. Active Interposers, which try to manipulate TPM transactions on the
>    bus using man in the middle and packet stealing to create TPM state
>    the interposer owner desires.
>
> Our broadest interposer target is the use of TPM_RS_PW for password
> authorization which sends the actual password to the TPM without any
> obfuscation and effectively hands it to any interposer. The way to fix
> this is to use real sessions for HMAC capabilities to ensure integrity
> and to use parameter and response encryption to ensure confidentiality
> of the data flowing over the TPM bus.  HMAC sessions by agreeing a
> challenge with the TPM and then giving a response which is a HMAC of
> the password and the challenge, so the application proves knowledge of
> the password to the TPM without ever transmitting the password itself.
> Using HMAC sessions when sending commands to the TPM also provides
> some measure of protection against active interposers, since the
> interposer can't interfere with or delete a HMAC'd command (because
> they can't manufacture a response with the correct HMAC).
>
> To protect TPM transactions where there isn't a shared secret
> (i.e. the command is something like a PCR extension which doesn't
> involve a TPM object with a password) we have to do a bit more work to
> set up sessions with a passed in encrypted secret (called a salt) to
> act in place of the shared secret in the HMAC.  This secret salt is
> effectively a random number encrypted to a public key of the TPM.  The
> final piece of the puzzle is using parameter input and response return
> encryption, so any interposer can't see the data passing from the
> application to the TPM and vice versa.
>
> The most insidious interposer attack of all is a reset attack: since
> the interposer has access to the TPM bus, it can assert the TPM reset
> line any time it wants.  When a TPM resets it mostly comes back in the
> same state except that all the PCRs are reset to their initial values.
> Controlling the reset line allows the interposer to change the PCR
> state after the fact by resetting the TPM and then replaying PCR
> extends to get the PCRs into a valid state to release secrets, so even
> if an attack event was recorded, the record is erased.  This reset
> attack violates the fundamental princible of non-repudiability of TPM
> logs.  Defeating the reset attack involves tying all TPM operations
> within the kernel to a property which will change detectably if the
> TPM is reset.  For that reason, we tie all TPM sessions to the null
> hierarchy we obtain at start of day and whose seed changes on every
> reset.  If an active interposer asserts a TPM reset, the new null
> primary won't match the kernel's stored one and all TPM operations
> will start failing because of HMAC mismatches in the sessions.  So if
> the kernel TPM code keeps operating, it guarantees that a reset hasn't
> occurred.
>
> The final part of the puzzle is that the machine owner must have a
> fixed idea of the EK of their TPM and should have certified this with
> the TPM manufacturer.  On every boot, the certified EK public key
> should be used to do a make credential/activate credential attestation
> key insertion and then the null key certified with the attestation
> key.  We can follow a trust on first use model where an OS
> installation will extract and verify a public EK and save it to a read
> only file.
>
> This patch series adds a simple API which can ensure the above
> properties as a layered addition to the existing TPM handling code.
> This series now includes protections for PCR extend, getting random
> numbers from the TPM and data sealing and unsealing.  It therefore
> eliminates all uses of TPM2_RS_PW in the kernel and adds encryption
> protection to sensitive data flowing into and out of the TPM.  The
> first four patches add more sophisticated buffer handling to the TPM
> which is needed to build the more complex encryption and
> authentication based commands.  Patch 6 adds all the generic
> cryptography primitives and patches 7-9 use them in critical TPM
> operations where we want to avoid or detect interposers.  Patch 10
> exports the name of the null key we used for boot/run time
> verification and patch 11 documents the security guarantees and
> expectations.
>
> This was originally sent over four years ago, with the last iteration
> being:
>
> https://lore.kernel.org/linux-integrity/1568031515.6613.31.camel@HansenPartnership.com/
>
> I'm dusting it off now because various forces at Microsoft and Google
> via the Open Compute Platform are making a lot of noise about
> interposers and we in the linux kernel look critically lacking in that
> regard, particularly for TPM trusted keys.
>
> ---
> v2 fixes the problems smatch reported and adds more explanation about
> the code motion in the first few patches
> v3 rebases the encryption to be against Ard's new library function, the
> aescfb addition of which appears as patch 1.
> v4 refreshes Ard's patch, adds kernel doc (including a new patch to
> add it to the moved tpm-buf functions) updates and rewords some commit
> logs
> v5: update to proposed tpm-buf implementation (for ease of use all
> precursor patches are part of this series, so the actual session HMAC
> and encryption begins at patch 10) and add review feedback
> v6: split the original sessions patch into three and change the config
> variable name
> v7: Collect reviews and add extra patch to check for and disable the TPM on
> detecting a reset attack.
>
> James
>
> ---
>
> Ard Biesheuvel (1):
>   crypto: lib - implement library version of AES in CFB mode
>
> James Bottomley (13):
>   tpm: Move buffer handling from static inlines to real functions
>   tpm: add buffer function to point to returned parameters
>   tpm: export the context save and load commands
>   tpm: Add NULL primary creation
>   tpm: Add HMAC session start and end functions
>   tpm: Add HMAC session name/handle append
>   tpm: Add the rest of the session HMAC API
>   tpm: add hmac checks to tpm2_pcr_extend()
>   tpm: add session encryption protection to tpm2_get_random()
>   KEYS: trusted: Add session encryption protection to the seal/unseal
>     path
>   tpm: add the null key name as a sysfs export
>   Documentation: add tpm-security.rst
>   tpm: disable the TPM if NULL name changes
>
> Jarkko Sakkinen (7):
>   tpm: Remove unused tpm_buf_tag()
>   tpm: Remove tpm_send()
>   tpm: Update struct tpm_buf documentation comments
>   tpm: Store the length of the tpm_buf data separately.
>   tpm: TPM2B formatted buffers
>   tpm: Add tpm_buf_read_{u8,u16,u32}
>   KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers
>
>  Documentation/security/tpm/tpm-security.rst |  216 ++++
>  drivers/char/tpm/Kconfig                    |   14 +
>  drivers/char/tpm/Makefile                   |    2 +
>  drivers/char/tpm/tpm-buf.c                  |  251 ++++
>  drivers/char/tpm/tpm-chip.c                 |    6 +
>  drivers/char/tpm/tpm-interface.c            |   26 +-
>  drivers/char/tpm/tpm-sysfs.c                |   18 +
>  drivers/char/tpm/tpm.h                      |   14 +
>  drivers/char/tpm/tpm2-cmd.c                 |   53 +-
>  drivers/char/tpm/tpm2-sessions.c            | 1223 +++++++++++++++++++
>  drivers/char/tpm/tpm2-space.c               |   11 +-
>  include/crypto/aes.h                        |    5 +
>  include/keys/trusted_tpm.h                  |    2 -
>  include/linux/tpm.h                         |  296 +++--
>  lib/crypto/Kconfig                          |    5 +
>  lib/crypto/Makefile                         |    3 +
>  lib/crypto/aescfb.c                         |  257 ++++
>  security/keys/trusted-keys/trusted_tpm1.c   |   23 +-
>  security/keys/trusted-keys/trusted_tpm2.c   |  136 ++-
>  19 files changed, 2366 insertions(+), 195 deletions(-)
>  create mode 100644 Documentation/security/tpm/tpm-security.rst
>  create mode 100644 drivers/char/tpm/tpm-buf.c
>  create mode 100644 drivers/char/tpm/tpm2-sessions.c
>  create mode 100644 lib/crypto/aescfb.c

Thank you. I'll test this with QEMU and at least x86 before
giving any feedback. Just denoting that I've not missed this.
I should hopefully have bandwidth next week to achieve this.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-02-13 17:13 ` [PATCH v7 12/21] tpm: Add NULL primary creation James Bottomley
@ 2024-02-23 15:51   ` Jarkko Sakkinen
  2024-04-29 20:10     ` James Bottomley
  2024-03-30 18:48   ` Gabríel Arthúr Pétursson
  1 sibling, 1 reply; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 15:51 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> The session handling code uses a "salted" session, meaning a session
> whose salt is encrypted to the public part of another TPM key so an
> observer cannot obtain it (and thus deduce the session keys).  This
> patch creates and context saves in the tpm_chip area the primary key
> of the NULL hierarchy for this purpose.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
>
> ---
> v6: split out of original HMAC patch update config name
> v7: rename null seed parameters
> ---
>  drivers/char/tpm/Kconfig         |  11 ++
>  drivers/char/tpm/Makefile        |   1 +
>  drivers/char/tpm/tpm.h           |  10 ++
>  drivers/char/tpm/tpm2-cmd.c      |   5 +
>  drivers/char/tpm/tpm2-sessions.c | 276 +++++++++++++++++++++++++++++++
>  include/linux/tpm.h              |  49 ++++++
>  6 files changed, 352 insertions(+)
>  create mode 100644 drivers/char/tpm/tpm2-sessions.c
>
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 927088b2c3d3..e3c39a83171b 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -27,6 +27,17 @@ menuconfig TCG_TPM
>  
>  if TCG_TPM
>  
> +config TCG_TPM2_HMAC
> +	bool "Use encrypted and HMACd transactions on the TPM bus"

How about simply "Use HMAC-encrypted transactions"

The details are anyway in the description.

> +	default y
> +	help
> +          Setting this causes us to deploy a scheme which uses request
          ~~~

extra spaces

> +	  and response HMACs in addition to encryption for
> +	  communicating with the TPM to prevent or detect bus snooping
> +	  and interposer attacks (see tpm-security.rst).  Saying Y
> +	  here adds some encryption overhead to all kernel to TPM
> +	  transactions.
> +
>  config HW_RANDOM_TPM
>  	bool "TPM HW Random Number Generator support"
>  	depends on TCG_TPM && HW_RANDOM && !(TCG_TPM=y && HW_RANDOM=m)
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index ad3594e383e1..4c695b0388f3 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -17,6 +17,7 @@ tpm-y += eventlog/tpm1.o
>  tpm-y += eventlog/tpm2.o
>  tpm-y += tpm-buf.o
>  
> +tpm-$(CONFIG_TCG_TPM2_HMAC) += tpm2-sessions.o
>  tpm-$(CONFIG_ACPI) += tpm_ppi.o eventlog/acpi.o
>  tpm-$(CONFIG_EFI) += eventlog/efi.o
>  tpm-$(CONFIG_OF) += eventlog/of.o
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index cbc9d1e2974d..6b8b9956ba69 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -321,4 +321,14 @@ void tpm_bios_log_setup(struct tpm_chip *chip);
>  void tpm_bios_log_teardown(struct tpm_chip *chip);
>  int tpm_dev_common_init(void);
>  void tpm_dev_common_exit(void);
> +
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +int tpm2_sessions_init(struct tpm_chip *chip);

I'm sorry but "sessions" and "init" are the worst possible terminology I
could every pick when trying to make a function that self-documents
itself :-)

I'd like to see here well-scoped name so that it is easy to connect
this to its purpose when reviewing some other patches.


> +#else
> +static inline int tpm2_sessions_init(struct tpm_chip *chip)
> +{
> +	return 0;
> +}
> +#endif
> +
>  #endif
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 93545be190a5..b0e72fb563d9 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -759,6 +759,11 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>  		rc = 0;
>  	}
>  
> +	if (rc)
> +		goto out;
> +
> +	rc = tpm2_sessions_init(chip);
> +
>  out:
>  	/*
>  	 * Infineon TPM in field upgrade mode will return no data for the number
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> new file mode 100644
> index 000000000000..9fc263ee02c2
> --- /dev/null
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -0,0 +1,276 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright (C) 2018 James.Bottomley@HansenPartnership.com
> + *

useless extra line in the commment

> + */
> +
> +#include "tpm.h"
> +

spurious newline

> +#include <asm/unaligned.h>

spurious newline
> +
> +#include <crypto/aes.h>

spurious newline
> +
> +/* if you change to AES256, you only need change this */
> +#define AES_KEYBYTES	AES_KEYSIZE_128

AES_KEY_BYTES. Also the comment is talking about changing something
without documenting what it is. Even not having the comment at all
would be less confusing.

> +
spurious newline

> +#define AES_KEYBITS	(AES_KEYBYTES*8)

AES_KEY_BITS

Also, documentation missing.

> +

Documentation missing for "tpm2_parse_create_primary". It is a complex
function despite being not exported so definitely needs documentation.


> +static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
> +				     u32 *nullkey)
                                          ~~~~~~~
					  null_key

> +{
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +	off_t offset_r = TPM_HEADER_SIZE, offset_t;
> +	u16 len = TPM_HEADER_SIZE;
> +	u32 tot_len = be32_to_cpu(head->length);

no good reason to use more confusing namme "tot_len", instead of more
readable "total_len".

> +	u32 val, parm_len;
> +
> +	*nullkey = tpm_buf_read_u32(buf, &offset_r);
> +	parm_len = tpm_buf_read_u32(buf, &offset_r);
        ~~~~~~~~
	param_len

> +	/*
> +	 * parm_len doesn't include the header, but all the other
> +	 * lengths and offsets do, so add it to parm len to make
> +	 * the comparisons easier
> +	 */
> +	parm_len += TPM_HEADER_SIZE;
> +
> +	if (parm_len + 8 > tot_len)
> +		return -EINVAL;
> +	len = tpm_buf_read_u16(buf, &offset_r);
> +	offset_t = offset_r;
> +	/* now we have the public area, compute the name of the object */
> +	put_unaligned_be16(TPM_ALG_SHA256, chip->null_key_name);
> +	sha256(&buf->data[offset_r], len, chip->null_key_name + 2);
> +
> +	/* validate the public key */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	/* key type (must be what we asked for) */
> +	if (val != TPM_ALG_ECC)
> +		return -EINVAL;
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	/* name algorithm */
> +	if (val != TPM_ALG_SHA256)
> +		return -EINVAL;
> +	val = tpm_buf_read_u32(buf, &offset_t);
> +	/* object properties */
> +	if (val != (TPM2_OA_NO_DA |
> +		    TPM2_OA_FIXED_TPM |
> +		    TPM2_OA_FIXED_PARENT |
> +		    TPM2_OA_SENSITIVE_DATA_ORIGIN |
> +		    TPM2_OA_USER_WITH_AUTH |
> +		    TPM2_OA_DECRYPT |
> +		    TPM2_OA_RESTRICTED))

Please make define a mask constant for these bits and use it here
instead. There's just too many and make the code really unredable.
I'd even suggesting documenting that constant with some rationale
for the mask.

Here the logic is obviously to fix the primary key to the exact
chip and make unmovable (cannot be migrated), isn't it? That would
perfectly sufficient documentation for the constant, or along the
lines.


> +		return -EINVAL;
> +	/* auth policy (empty) */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != 0)
> +		return -EINVAL;

I'd add empty line betwen each of these checks to make it more
readable.

> +	/* symmetric key parameters */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != TPM_ALG_AES)
> +		return -EINVAL;
> +	/* symmetric key length */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != AES_KEYBITS)
> +		return -EINVAL;
> +	/* symmetric encryption scheme */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != TPM_ALG_CFB)
> +		return -EINVAL;
> +	/* signing scheme */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != TPM_ALG_NULL)
> +		return -EINVAL;
> +	/* ECC Curve */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != TPM2_ECC_NIST_P256)
> +		return -EINVAL;
> +	/* KDF Scheme */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != TPM_ALG_NULL)
> +		return -EINVAL;
> +	/* x point */
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != EC_PT_SZ)
> +		return -EINVAL;
> +	memcpy(chip->null_ec_key_x, &buf->data[offset_t], val);
> +	offset_t += val;
> +	val = tpm_buf_read_u16(buf, &offset_t);
> +	if (val != EC_PT_SZ)
> +		return -EINVAL;
> +	memcpy(chip->null_ec_key_y, &buf->data[offset_t], val);
> +	offset_t += val;
> +
> +	/* original length of the whole TPM2B */
> +	offset_r += len;
> +
> +	/* should have exactly consumed the TPM2B public structure */
> +	if (offset_t != offset_r)
> +		return -EINVAL;
> +	if (offset_r > parm_len)
> +		return -EINVAL;
> +	/* creation data (skip) */
> +	len = tpm_buf_read_u16(buf, &offset_r);
> +	offset_r += len;
> +	if (offset_r > parm_len)
> +		return -EINVAL;
> +	/* creation digest (must be sha256) */
> +	len = tpm_buf_read_u16(buf, &offset_r);
> +	offset_r += len;
> +	if (len != SHA256_DIGEST_SIZE || offset_r > parm_len)
> +		return -EINVAL;
> +	/* TPMT_TK_CREATION follows */
> +	/* tag, must be TPM_ST_CREATION (0x8021) */
> +	val = tpm_buf_read_u16(buf, &offset_r);
> +	if (val != TPM2_ST_CREATION || offset_r > parm_len)
> +		return -EINVAL;
> +	/* hierarchy (must be NULL) */
> +	val = tpm_buf_read_u32(buf, &offset_r);
> +	if (val != TPM2_RH_NULL || offset_r > parm_len)
> +		return -EINVAL;
> +	/* the ticket digest HMAC (might not be sha256) */
> +	len = tpm_buf_read_u16(buf, &offset_r);
> +	offset_r += len;
> +	if (offset_r > parm_len)
> +		return -EINVAL;
> +	/*
> +	 * finally we have the name, which is a sha256 digest plus a 2
> +	 * byte algorithm type
> +	 */
> +	len = tpm_buf_read_u16(buf, &offset_r);
> +	if (offset_r + len != parm_len + 8)
> +		return -EINVAL;
> +	if (len != SHA256_DIGEST_SIZE + 2)
> +		return -EINVAL;
> +
> +	if (memcmp(chip->null_key_name, &buf->data[offset_r],
> +		   SHA256_DIGEST_SIZE + 2) != 0) {
> +		dev_err(&chip->dev, "NULL Seed name comparison failed\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
>

documentation missing:

> +static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle)
> +{
> +	int rc;
> +	struct tpm_buf buf;
> +	struct tpm_buf template;
> +
> +	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE_PRIMARY);
> +	if (rc)
> +		return rc;
> +
> +	rc = tpm_buf_init_sized(&template);
> +	if (rc) {
> +		tpm_buf_destroy(&buf);
> +		return rc;
> +	}
> +
> +	/*
> +	 * create the template.  Note: in order for userspace to
> +	 * verify the security of the system, it will have to create
> +	 * and certify this NULL primary, meaning all the template
> +	 * parameters will have to be identical, so conform exactly to
> +	 * the TCG TPM v2.0 Provisioning Guidance for the SRK ECC
> +	 * key
> +	 */
> +
> +	/* key type */
> +	tpm_buf_append_u16(&template, TPM_ALG_ECC);
> +	/* name algorithm */
> +	tpm_buf_append_u16(&template, TPM_ALG_SHA256);
> +	/* object properties */
> +	tpm_buf_append_u32(&template, TPM2_OA_NO_DA |
> +			   TPM2_OA_FIXED_TPM |
> +			   TPM2_OA_FIXED_PARENT |
> +			   TPM2_OA_SENSITIVE_DATA_ORIGIN |
> +			   TPM2_OA_USER_WITH_AUTH |
> +			   TPM2_OA_DECRYPT |
> +			   TPM2_OA_RESTRICTED);
> +	/* sauth policy (empty) */
> +	tpm_buf_append_u16(&template, 0);
> +
> +	/* BEGIN parameters: key specific; for ECC*/
> +	/* symmetric algorithm */
> +	tpm_buf_append_u16(&template, TPM_ALG_AES);
> +	/* bits for symmetric algorithm */
> +	tpm_buf_append_u16(&template, 128);
> +	/* algorithm mode (must be CFB) */
> +	tpm_buf_append_u16(&template, TPM_ALG_CFB);
> +	/* scheme (NULL means any scheme) */
> +	tpm_buf_append_u16(&template, TPM_ALG_NULL);
> +	/* ECC Curve ID */
> +	tpm_buf_append_u16(&template, TPM2_ECC_NIST_P256);
> +	/* KDF Scheme */
> +	tpm_buf_append_u16(&template, TPM_ALG_NULL);
> +	/* unique: key specific; for ECC it is two points */
> +	tpm_buf_append_u16(&template, 0);
> +	tpm_buf_append_u16(&template, 0);
> +	/* END parameters */
> +
> +	/* primary handle */
> +	tpm_buf_append_u32(&buf, hierarchy);
> +	tpm_buf_append_empty_auth(&buf, TPM2_RS_PW);
> +	/* sensitive create size is 4 for two empty buffers */
> +	tpm_buf_append_u16(&buf, 4);
> +	/* sensitive create auth data (empty) */
> +	tpm_buf_append_u16(&buf, 0);
> +	/* sensitive create sensitive data (empty) */
> +	tpm_buf_append_u16(&buf, 0);
> +	/* the public template */
> +	tpm_buf_append(&buf, template.data, template.length);
> +	tpm_buf_destroy(&template);
> +	/* outside info (empty) */
> +	tpm_buf_append_u16(&buf, 0);
> +	/* creation PCR (none) */
> +	tpm_buf_append_u32(&buf, 0);
> +
> +	rc = tpm_transmit_cmd(chip, &buf, 0,
> +			      "attempting to create NULL primary");
> +
> +	if (rc == TPM2_RC_SUCCESS)
> +		rc = tpm2_parse_create_primary(chip, &buf, handle);
> +
> +	tpm_buf_destroy(&buf);
> +
> +	return rc;
> +}
> +
> +static int tpm2_create_null_primary(struct tpm_chip *chip)
> +{
> +	u32 nullkey;
            ~~~~~~~
	    null_key
   

> +	int rc;
> +
> +	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey);
> +
> +	if (rc == TPM2_RC_SUCCESS) {
> +		unsigned int offset = 0; /* dummy offset for null key context */
> +
> +		rc = tpm2_save_context(chip, nullkey, chip->null_key_context,
> +				       sizeof(chip->null_key_context), &offset);
> +		tpm2_flush_context(chip, nullkey);
> +	}
> +
> +	return rc;
> +}
> +
> +/**
> + * tpm2_sessions_init() - start of day initialization for the sessions code
> + * @chip: TPM chip
> + *
> + * Derive and context save the null primary and allocate memory in the
> + * struct tpm_chip for the authorizations.

isn't this exactly for HMAC authorization at least in the patch set
scope? plural confuses me here.

> + */
> +int tpm2_sessions_init(struct tpm_chip *chip)
> +{
> +	int rc;
> +
> +	rc = tpm2_create_null_primary(chip);
> +	if (rc)
> +		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL(tpm2_sessions_init);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 6be263509e81..3060ab794afb 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -35,12 +35,15 @@ struct trusted_key_options;
>  enum tpm_algorithms {
>  	TPM_ALG_ERROR		= 0x0000,
>  	TPM_ALG_SHA1		= 0x0004,
> +	TPM_ALG_AES		= 0x0006,
>  	TPM_ALG_KEYEDHASH	= 0x0008,
>  	TPM_ALG_SHA256		= 0x000B,
>  	TPM_ALG_SHA384		= 0x000C,
>  	TPM_ALG_SHA512		= 0x000D,
>  	TPM_ALG_NULL		= 0x0010,
>  	TPM_ALG_SM3_256		= 0x0012,
> +	TPM_ALG_ECC		= 0x0023,
> +	TPM_ALG_CFB		= 0x0043,
>  };
>  
>  /*
> @@ -49,6 +52,11 @@ enum tpm_algorithms {
>   */
>  #define TPM_MAX_HASHES	5
>  
> +enum tpm2_curves {
> +	TPM2_ECC_NONE		= 0x0000,
> +	TPM2_ECC_NIST_P256	= 0x0003,
> +};
> +
>  struct tpm_digest {
>  	u16 alg_id;
>  	u8 digest[TPM_MAX_DIGEST_SIZE];
> @@ -116,6 +124,20 @@ struct tpm_chip_seqops {
>  	const struct seq_operations *seqops;
>  };
>  
> +/* fixed define for the curve we use which is NIST_P256 */
> +#define EC_PT_SZ	32
> +
> +/*
> + * fixed define for the size of a name.  This is actually HASHALG size
> + * plus 2, so 32 for SHA256
> + */
> +#define TPM2_NAME_SIZE	34
> +
> +/*
> + * The maximum size for an object context
> + */
> +#define TPM2_MAX_CONTEXT_SIZE 4096
> +
>  struct tpm_chip {
>  	struct device dev;
>  	struct device devs;
> @@ -170,6 +192,14 @@ struct tpm_chip {
>  
>  	/* active locality */
>  	int locality;
> +
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +	/* details for communication security via sessions */
> +	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE]; /* context for NULL seed */

	/* Saved context of the null seed: */

I like the description on top because they suffer less alignment
issues and can have more verbose explanation. "context for NULL
seed" is good as no comment at all./

> +	u8 null_key_name[TPM2_NAME_SIZE];	 /* name of NULL seed */

	/* Digest of the public area: */

This is not totally accurate but way more documenting than the
current description, which is tautology, i.e. you are saying that
"name is name" in the comment leaving the reader questioning what
the heck is name.

Not totally accurate i.e. missing concatenated alg identifier but
good enough...


> +	u8 null_ec_key_x[EC_PT_SZ];
> +	u8 null_ec_key_y[EC_PT_SZ];
> +#endif

this is now very nice clean and udnerstandable:

I'd prefer tho this formatting:

	/* Name of the NULL seed: */
	u8 null_key_name[TPM2_NAME_SIZE];


>  };
>  
>  #define TPM_HEADER_SIZE		10
> @@ -194,6 +224,7 @@ enum tpm2_timeouts {
>  enum tpm2_structures {
>  	TPM2_ST_NO_SESSIONS	= 0x8001,
>  	TPM2_ST_SESSIONS	= 0x8002,
> +	TPM2_ST_CREATION	= 0x8021,
>  };
>  
>  /* Indicates from what layer of the software stack the error comes from */
> @@ -243,6 +274,7 @@ enum tpm2_command_codes {
>  };
>  
>  enum tpm2_permanent_handles {
> +	TPM2_RH_NULL		= 0x40000007,
>  	TPM2_RS_PW		= 0x40000009,
>  };
>  
> @@ -318,7 +350,11 @@ struct tpm_buf {
>  enum tpm2_object_attributes {
>  	TPM2_OA_FIXED_TPM		= BIT(1),
>  	TPM2_OA_FIXED_PARENT		= BIT(4),
> +	TPM2_OA_SENSITIVE_DATA_ORIGIN	= BIT(5),
>  	TPM2_OA_USER_WITH_AUTH		= BIT(6),
> +	TPM2_OA_NO_DA			= BIT(10),
> +	TPM2_OA_RESTRICTED		= BIT(16),
> +	TPM2_OA_DECRYPT			= BIT(17),
>  };
>  

Here would be a great place to declarate aforementioned mask.

>  enum tpm2_session_attributes {
> @@ -373,6 +409,15 @@ extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
>  extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
>  extern struct tpm_chip *tpm_default_chip(void);
>  void tpm2_flush_context(struct tpm_chip *chip, u32 handle);

please add empty line here.

> +static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
> +{
> +	/* simple authorization for empty auth */
> +	tpm_buf_append_u32(buf, 9);		/* total length of auth */
> +	tpm_buf_append_u32(buf, handle);
> +	tpm_buf_append_u16(buf, 0);		/* nonce len */
> +	tpm_buf_append_u8(buf, 0);		/* attributes */
> +	tpm_buf_append_u16(buf, 0);		/* hmac len */
> +}
>  #else
>  static inline int tpm_is_tpm2(struct tpm_chip *chip)
>  {
> @@ -399,5 +444,9 @@ static inline struct tpm_chip *tpm_default_chip(void)
>  {
>  	return NULL;
>  }
> +
> +static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
> +{
> +}
>  #endif
>  #endif

I skipped first eleven patches because they are completed. This patch
will be finished once all the numerous style issues have been fixed.
Approach is totally correct...

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 13/21] tpm: Add HMAC session start and end functions
  2024-02-13 17:13 ` [PATCH v7 13/21] tpm: Add HMAC session start and end functions James Bottomley
@ 2024-02-23 17:02   ` Jarkko Sakkinen
  2024-04-29 20:11     ` James Bottomley
  0 siblings, 1 reply; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:02 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> Add session  based HMAC  authentication plus parameter  decryption and
> response encryption  using AES. The  basic design is to  segregate all
> the nasty crypto, hash and hmac code into tpm2-sessions.c and export a
> usable API.  The API first of all starts off by gaining a session with
> tpm2_start_auth_session() which  initiates a session with  the TPM and
> allocates  an  opaque  tpm2_auth   structure  to  handle  the  session
> parameters.  The  design is that  session use will be  single threaded
> from start to finish under the ops lock, so the tpm2_auth structure is
> stored in struct tpm2_chip to simpify the externally visible API.
>
> The session can be ended with tpm2_end_auth_session() which is
> designed only to be used in error legs.  Ordinarily the further
> session API (future patches) will end or continue the session
> appropriately without having to call this.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts
>
> ---
>
> v6: split into new patch, update config variable
> v7: add tpm2_ prefix and memzero_explicit
> ---
>  drivers/char/tpm/Kconfig         |   3 +
>  drivers/char/tpm/tpm-buf.c       |   1 +
>  drivers/char/tpm/tpm-chip.c      |   3 +
>  drivers/char/tpm/tpm2-sessions.c | 385 +++++++++++++++++++++++++++++++
>  include/linux/tpm.h              |  34 +++
>  5 files changed, 426 insertions(+)
>
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index e3c39a83171b..086cb8588493 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -30,6 +30,9 @@ if TCG_TPM
>  config TCG_TPM2_HMAC
>  	bool "Use encrypted and HMACd transactions on the TPM bus"
>  	default y
> +	select CRYPTO_ECDH
> +	select CRYPTO_LIB_AESCFB
> +	select CRYPTO_LIB_SHA256
>  	help
>            Setting this causes us to deploy a scheme which uses request
>  	  and response HMACs in addition to encryption for
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index bb81180495d1..274130398569 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -44,6 +44,7 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>  	head->tag = cpu_to_be16(tag);
>  	head->length = cpu_to_be32(sizeof(*head));
>  	head->ordinal = cpu_to_be32(ordinal);
> +	buf->handles = 0;
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_reset);
>  
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 42b1062e33cd..d93937326b2e 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -275,6 +275,9 @@ static void tpm_dev_release(struct device *dev)
>  	kfree(chip->work_space.context_buf);
>  	kfree(chip->work_space.session_buf);
>  	kfree(chip->allocated_banks);
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +	kfree(chip->auth);
> +#endif
>  	kfree(chip);
>  }
>  
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 9fc263ee02c2..c8792a6b8bd4 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -3,18 +3,399 @@
>  /*
>   * Copyright (C) 2018 James.Bottomley@HansenPartnership.com
>   *
> + * Cryptographic helper routines for handling TPM2 sessions for
> + * authorization HMAC and request response encryption.
> + *
> + * The idea is to ensure that every TPM command is HMAC protected by a
> + * session, meaning in-flight tampering would be detected and in
> + * addition all sensitive inputs and responses should be encrypted.
> + *
> + * The basic way this works is to use a TPM feature called salted
> + * sessions where a random secret used in session construction is
> + * encrypted to the public part of a known TPM key.  The problem is we
> + * have no known keys, so initially a primary Elliptic Curve key is
> + * derived from the NULL seed (we use EC because most TPMs generate
> + * these keys much faster than RSA ones).  The curve used is NIST_P256
> + * because that's now mandated to be present in 'TCG TPM v2.0
> + * Provisioning Guidance'
> + *
> + * Threat problems: the initial TPM2_CreatePrimary is not (and cannot
> + * be) session protected, so a clever Man in the Middle could return a
> + * public key they control to this command and from there intercept
> + * and decode all subsequent session based transactions.  The kernel
> + * cannot mitigate this threat but, after boot, userspace can get
> + * proof this has not happened by asking the TPM to certify the NULL
> + * key.  This certification would chain back to the TPM Endorsement
> + * Certificate and prove the NULL seed primary had not been tampered
> + * with and thus all sessions must have been cryptographically secure.
> + * To assist with this, the initial NULL seed public key name is made
> + * available in a sysfs file.
> + *
> + * Use of these functions:
> + *
> + * The design is all the crypto, hash and hmac gunk is confined in this
> + * file and never needs to be seen even by the kernel internal user.  To
> + * the user there's an init function tpm2_sessions_init() that needs to
> + * be called once per TPM which generates the NULL seed primary key.
> + *
> + * These are the usage functions:
> + *
> + * tpm2_start_auth_session() which allocates the opaque auth structure
> + *	and gets a session from the TPM.  This must be called before
> + *	any of the following functions.  The session is protected by a
> + *	session_key which is derived from a random salt value
> + *	encrypted to the NULL seed.
> + * tpm2_end_auth_session() kills the session and frees the resources.
> + *	Under normal operation this function is done by
> + *	tpm_buf_check_hmac_response(), so this is only to be used on
> + *	error legs where the latter is not executed.
>   */
>  
>  #include "tpm.h"
>  
> +#include <linux/random.h>
> +#include <linux/scatterlist.h>
> +
>  #include <asm/unaligned.h>
>  
>  #include <crypto/aes.h>
> +#include <crypto/kpp.h>
> +#include <crypto/ecdh.h>
> +#include <crypto/hash.h>
> +#include <crypto/hmac.h>
>  
>  /* if you change to AES256, you only need change this */
>  #define AES_KEYBYTES	AES_KEYSIZE_128
>  
>  #define AES_KEYBITS	(AES_KEYBYTES*8)
> +#define AUTH_MAX_NAMES	3
> +
> +/*
> + * This is the structure that carries all the auth information (like
> + * session handle, nonces, session key and auth) from use to use it is
> + * designed to be opaque to anything outside.
> + */
> +struct tpm2_auth {
> +	u32 handle;
> +	/*
> +	 * This has two meanings: before tpm_buf_fill_hmac_session()
> +	 * it marks the offset in the buffer of the start of the
> +	 * sessions (i.e. after all the handles).  Once the buffer has
> +	 * been filled it markes the session number of our auth
> +	 * session so we can find it again in the response buffer.
> +	 *
> +	 * The two cases are distinguished because the first offset
> +	 * must always be greater than TPM_HEADER_SIZE and the second
> +	 * must be less than or equal to 5.
> +	 */
> +	u32 session;
> +	/*
> +	 * the size here is variable and set by the size of our_nonce
> +	 * which must be between 16 and the name hash length. we set
> +	 * the maximum sha256 size for the greatest protection
> +	 */
> +	u8 our_nonce[SHA256_DIGEST_SIZE];
> +	u8 tpm_nonce[SHA256_DIGEST_SIZE];
> +	/*
> +	 * the salt is only used across the session command/response
           ~
	   T
 

> +	 * after that it can be used as a scratch area
                                                     ~
						     a.

> +	 */
> +	union {
> +		u8 salt[EC_PT_SZ];
> +		/* scratch for key + IV */
> +		u8 scratch[AES_KEYBYTES + AES_BLOCK_SIkkkZE];
> +	};
> +	u8 session_key[SHA256_DIGEST_SIZE];
> +};
> +
> +/*
> + * It turns out the crypto hmac(sha256) is hard for us to consume
> + * because it assumes a fixed key and the TPM seems to change the key
> + * on every operation, so we weld the hmac init and final functions in
> + * here to give it the same usage characteristics as a regular hash
> + */
> +static void hmac_init(struct sha256_state *sctx, u8 *key, int keylen)

tpm_*

there's too many hmac sites in the kernel so it would be nice to git
grep these easily in the future.

> +{
> +	u8 pad[SHA256_BLOCK_SIZE];
> +	int i;
> +
> +	sha256_init(sctx);
> +	for (i = 0; i < sizeof(pad); i++) {
> +		if (i < keylen)
> +			pad[i] = key[i];
> +		else
> +			pad[i] = 0;
> +		pad[i] ^= HMAC_IPAD_VALUE;
> +	}
> +	sha256_update(sctx, pad, sizeof(pad));
> +}
> +
> +static void hmac_final(struct sha256_state *sctx, u8 *key, int keylen, u8 *out)

tpm_*

> +{
> +	u8 pad[SHA256_BLOCK_SIZE];
> +	int i;
> +
> +	for (i = 0; i < sizeof(pad); i++) {
> +		if (i < keylen)
> +			pad[i] = key[i];
> +		else
> +			pad[i] = 0;
> +		pad[i] ^= HMAC_OPAD_VALUE;
> +	}
> +
> +	/* collect the final hash;  use out as temporary storage */
> +	sha256_final(sctx, out);
> +
> +	sha256_init(sctx);
> +	sha256_update(sctx, pad, sizeof(pad));
> +	sha256_update(sctx, out, SHA256_DIGEST_SIZE);
> +	sha256_final(sctx, out);
> +}
> +
> +/*
> + * assume hash sha256 and nonces u, v of size SHA256_DIGEST_SIZE but
      ~
      A

> + * otherwise standard KDFa.  Note output is in bytes not bits.
> + */
> +static void KDFa(u8 *key, int keylen, const char *label, u8 *u,
                                 ~~~~~~
				 key_len


tpm_* prefix

> +		 u8 *v, int bytes, u8 *out)

Why bytes is a signed type? Does it need to be multiple of
something?

> +{
> +	u32 counter;
> +	const __be32 bits = cpu_to_be32(bytes * 8);
> +
> +	for (counter = 1; bytes > 0; bytes -= SHA256_DIGEST_SIZE, counter++,
> +		     out += SHA256_DIGEST_SIZE) {

Let's open code this:

	counter = 1;
	while (bytes > 0) {
		/* ... */

		bytes -= SHA256_DIGEST_SIZE;
		out += SHA256_DIGEST_SIZE;
		counter++;
	}

I'd figure that this requires one index, not three. Others
have linear relation? The for-loop construc is too cryptic.

> +		struct sha256_state sctx;
> +		__be32 c = cpu_to_be32(counter);
> +
> +		hmac_init(&sctx, key, keylen);
> +		sha256_update(&sctx, (u8 *)&c, sizeof(c));
> +		sha256_update(&sctx, label, strlen(label)+1);
> +		sha256_update(&sctx, u, SHA256_DIGEST_SIZE);
> +		sha256_update(&sctx, v, SHA256_DIGEST_SIZE);
> +		sha256_update(&sctx, (u8 *)&bits, sizeof(bits));
> +		hmac_final(&sctx, key, keylen, out);
> +	}
> +}
> +
> +/*
> + * Somewhat of a bastardization of the real KDFe.  We're assuming
> + * we're working with known point sizes for the input parameters and
> + * the hash algorithm is fixed at sha256.  Because we know that the
> + * point size is 32 bytes like the hash size, there's no need to loop
> + * in this KDF.
> + */
> +static void KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
> +		 u8 *keyout)
 		     ~~~~~~~
		     the previous function had 'out'. why the name
		     change?

tpm_*

> +{
> +	struct sha256_state sctx;
> +	/*
> +	 * this should be an iterative counter, but because we know
> +	 *  we're only taking 32 bytes for the point using a sha256
> +	 *  hash which is also 32 bytes, there's only one loop
> +	 */
> +	__be32 c = cpu_to_be32(1);
> +
> +	sha256_init(&sctx);
> +	/* counter (BE) */
> +	sha256_update(&sctx, (u8 *)&c, sizeof(c));
> +	/* secret value */
> +	sha256_update(&sctx, z, EC_PT_SZ);
> +	/* string including trailing zero */
> +	sha256_update(&sctx, str, strlen(str)+1);
> +	sha256_update(&sctx, pt_u, EC_PT_SZ);
> +	sha256_update(&sctx, pt_v, EC_PT_SZ);
> +	sha256_final(&sctx, keyout);
> +}
> +
> +static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> +{
> +	struct crypto_kpp *kpp;
> +	struct kpp_request *req;
> +	struct scatterlist s[2], d[1];
> +	struct ecdh p = {0};
> +	u8 encoded_key[EC_PT_SZ], *x, *y;
> +	unsigned int buf_len;

i'd prefer the reverse christmas tree order

> +
> +	/* secret is two sized points */
> +	tpm_buf_append_u16(buf, (EC_PT_SZ + 2)*2);
> +	/*
> +	 * we cheat here and append uninitialized data to form
> +	 * the points.  All we care about is getting the two
> +	 * co-ordinate pointers, which will be used to overwrite
> +	 * the uninitialized data
> +	 */
> +	tpm_buf_append_u16(buf, EC_PT_SZ);
> +	x = &buf->data[tpm_buf_length(buf)];
> +	tpm_buf_append(buf, encoded_key, EC_PT_SZ);
> +	tpm_buf_append_u16(buf, EC_PT_SZ);
> +	y = &buf->data[tpm_buf_length(buf)];
> +	tpm_buf_append(buf, encoded_key, EC_PT_SZ);
> +	sg_init_table(s, 2);
> +	sg_set_buf(&s[0], x, EC_PT_SZ);
> +	sg_set_buf(&s[1], y, EC_PT_SZ);
> +
> +	kpp = crypto_alloc_kpp("ecdh-nist-p256", CRYPTO_ALG_INTERNAL, 0);
> +	if (IS_ERR(kpp)) {
> +		dev_err(&chip->dev, "crypto ecdh allocation failed\n");
> +		return;
> +	}
> +
> +	buf_len = crypto_ecdh_key_len(&p);
> +	if (sizeof(encoded_key) < buf_len) {
> +		dev_err(&chip->dev, "salt buffer too small needs %d\n",
> +			buf_len);
> +		goto out;
> +	}
> +	crypto_ecdh_encode_key(encoded_key, buf_len, &p);
> +	/* this generates a random private key */
> +	crypto_kpp_set_secret(kpp, encoded_key, buf_len);
> +
> +	/* salt is now the public point of this private key */
> +	req = kpp_request_alloc(kpp, GFP_KERNEL);
> +	if (!req)
> +		goto out;
> +	kpp_request_set_input(req, NULL, 0);
> +	kpp_request_set_output(req, s, EC_PT_SZ*2);
> +	crypto_kpp_generate_public_key(req);
> +	/*
> +	 * we're not done: now we have to compute the shared secret
> +	 * which is our private key multiplied by the tpm_key public
> +	 * point, we actually only take the x point and discard the y
> +	 * point and feed it through KDFe to get the final secret salt
> +	 */
> +	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
> +	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
> +	kpp_request_set_input(req, s, EC_PT_SZ*2);
> +	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
> +	kpp_request_set_output(req, d, EC_PT_SZ);
> +	crypto_kpp_compute_shared_secret(req);
> +	kpp_request_free(req);
> +
> +	/*
> +	 * pass the shared secret through KDFe for salt. Note salt
> +	 * area is used both for input shared secret and output salt.
> +	 * This works because KDFe fully consumes the secret before it
> +	 * writes the salt
> +	 */
> +	KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
> +	     chip->auth->salt);

empty line missing before the label

> + out:
> +	crypto_free_kpp(kpp);
> +}
> +/**
> + * tpm2_end_auth_session() - kill the allocated auth session
> + * @chip: the TPM chip structure
> + *
> + * ends the session started by tpm2_start_auth_session and frees all
> + * the resources.  Under normal conditions,
> + * tpm_buf_check_hmac_response() will correctly end the session if
> + * required, so this function is only for use in error legs that will
> + * bypass the normal invocation of tpm_buf_check_hmac_response().
> + */
> +void tpm2_end_auth_session(struct tpm_chip *chip)
> +{
> +	tpm2_flush_context(chip, chip->auth->handle);
> +	memzero_explicit(chip->auth, sizeof(*chip->auth));
> +}
> +EXPORT_SYMBOL(tpm2_end_auth_session);
> +
> +static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
> +					 struct tpm_buf *buf)
> +{
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +	u32 tot_len = be32_to_cpu(head->length);
> +	off_t offset = TPM_HEADER_SIZE;
> +	u32 val;
> +
> +	/* we're starting after the header so adjust the length */
> +	tot_len -= TPM_HEADER_SIZE;
> +
> +	/* should have handle plus nonce */
> +	if (tot_len != 4 + 2 + sizeof(auth->tpm_nonce))
> +		return -EINVAL;
> +
> +	auth->handle = tpm_buf_read_u32(buf, &offset);
> +	val = tpm_buf_read_u16(buf, &offset);
> +	if (val != sizeof(auth->tpm_nonce))
> +		return -EINVAL;
> +	memcpy(auth->tpm_nonce, &buf->data[offset], sizeof(auth->tpm_nonce));
> +	/* now compute the session key from the nonces */
> +	KDFa(auth->salt, sizeof(auth->salt), "ATH", auth->tpm_nonce,
> +	     auth->our_nonce, sizeof(auth->session_key), auth->session_key);
> +
> +	return 0;
> +}
> +
> +/**
> + * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> + * @chip: the TPM chip structure to create the session with
> + *
> + * This function loads the NULL seed from its saved context and starts
> + * an authentication session on the null seed, fills in the
> + * @chip->auth structure to contain all the session details necessary
> + * for performing the HMAC, encrypt and decrypt operations and
> + * returns.  The NULL seed is flushed before this function returns.
> + *
> + * Return: zero on success or actual error encountered.
> + */
> +int tpm2_start_auth_session(struct tpm_chip *chip)
> +{
> +	struct tpm_buf buf;
> +	struct tpm2_auth *auth = chip->auth;
> +	int rc;
> +	unsigned int offset = 0; /* dummy offset for null seed context */

What does the comment is trying to say to me? Should be
in its own line.

> +	u32 nullkey;
> +
> +	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
> +			       &nullkey);
> +	if (rc)
> +		goto out;
> +
> +	auth->session = TPM_HEADER_SIZE;
> +
> +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
> +	if (rc)
> +		goto out;
> +
> +	/* salt key handle */
> +	tpm_buf_append_u32(&buf, nullkey);
> +	/* bind key handle */
> +	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
> +	/* nonce caller */
> +	get_random_bytes(auth->our_nonce, sizeof(auth->our_nonce));
> +	tpm_buf_append_u16(&buf, sizeof(auth->our_nonce));
> +	tpm_buf_append(&buf, auth->our_nonce, sizeof(auth->our_nonce));
> +
> +	/* append encrypted salt and squirrel away unencrypted in auth */
> +	tpm_buf_append_salt(&buf, chip);
> +	/* session type (HMAC, audit or policy) */
> +	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
> +
> +	/* symmetric encryption parameters */
> +	/* symmetric algorithm */
> +	tpm_buf_append_u16(&buf, TPM_ALG_AES);
> +	/* bits for symmetric algorithm */
> +	tpm_buf_append_u16(&buf, AES_KEYBITS);
> +	/* symmetric algorithm mode (must be CFB) */
> +	tpm_buf_append_u16(&buf, TPM_ALG_CFB);
> +	/* hash algorithm for session */
> +	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> +
> +	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> +	tpm2_flush_context(chip, nullkey);
> +
> +	if (rc == TPM2_RC_SUCCESS)
> +		rc = tpm2_parse_start_auth_session(auth, &buf);
> +
> +	tpm_buf_destroy(&buf);
> +
> +	if (rc)
> +		goto out;
> +
> + out:
> +	return rc;
> +}
> +EXPORT_SYMBOL(tpm2_start_auth_session);
>  
>  static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
>  				     u32 *nullkey)
		

What if this was simply tpm2_create_primary?


> @@ -271,6 +652,10 @@ int tpm2_sessions_init(struct tpm_chip *chip)
>  	if (rc)
>  		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
>  
> +	chip->auth = kmalloc(sizeof(*chip->auth), GFP_KERNEL);
> +	if (!chip->auth)
> +		return -ENOMEM;
> +
>  	return rc;
>  }
>  EXPORT_SYMBOL(tpm2_sessions_init);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 3060ab794afb..444f0a83682a 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -30,6 +30,14 @@
>  struct tpm_chip;
>  struct trusted_key_payload;
>  struct trusted_key_options;
> +/* opaque structure, holds auth session parameters like the session key */
> +struct tpm2_auth;
> +
> +enum tpm2_session_types {
> +	TPM2_SE_HMAC	= 0x00,
> +	TPM2_SE_POLICY	= 0x01,
> +	TPM2_SE_TRIAL	= 0x02,
> +};
>  
>  /* if you add a new hash to this, increment TPM_MAX_HASHES below */
>  enum tpm_algorithms {
> @@ -199,6 +207,7 @@ struct tpm_chip {
>  	u8 null_key_name[TPM2_NAME_SIZE];	 /* name of NULL seed */
>  	u8 null_ec_key_x[EC_PT_SZ];
>  	u8 null_ec_key_y[EC_PT_SZ];
> +	struct tpm2_auth *auth;
>  #endif
>  };
>  
> @@ -262,6 +271,7 @@ enum tpm2_command_codes {
>  	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
>  	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
>  	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
> +	TPM2_CC_START_AUTH_SESS		= 0x0176,
>  	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
>  	TPM2_CC_GET_CAPABILITY	        = 0x017A,
>  	TPM2_CC_GET_RANDOM	        = 0x017B,
> @@ -345,20 +355,30 @@ struct tpm_buf {
>  	u32 flags;
>  	u32 length;
>  	u8 *data;
> +	u8 handles;
>  };
>  
>  enum tpm2_object_attributes {
>  	TPM2_OA_FIXED_TPM		= BIT(1),
> +	TPM2_OA_ST_CLEAR		= BIT(2),
>  	TPM2_OA_FIXED_PARENT		= BIT(4),
>  	TPM2_OA_SENSITIVE_DATA_ORIGIN	= BIT(5),
>  	TPM2_OA_USER_WITH_AUTH		= BIT(6),
> +	TPM2_OA_ADMIN_WITH_POLICY	= BIT(7),
>  	TPM2_OA_NO_DA			= BIT(10),
> +	TPM2_OA_ENCRYPTED_DUPLICATION	= BIT(11),
>  	TPM2_OA_RESTRICTED		= BIT(16),
>  	TPM2_OA_DECRYPT			= BIT(17),
> +	TPM2_OA_SIGN			= BIT(18),
>  };
>  
>  enum tpm2_session_attributes {
>  	TPM2_SA_CONTINUE_SESSION	= BIT(0),
> +	TPM2_SA_AUDIT_EXCLUSIVE		= BIT(1),
> +	TPM2_SA_AUDIT_RESET		= BIT(3),
> +	TPM2_SA_DECRYPT			= BIT(5),
> +	TPM2_SA_ENCRYPT			= BIT(6),
> +	TPM2_SA_AUDIT			= BIT(7),
>  };
>  
>  struct tpm2_hash {
> @@ -449,4 +469,18 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
>  {
>  }
>  #endif
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +
> +int tpm2_start_auth_session(struct tpm_chip *chip);
> +void tpm2_end_auth_session(struct tpm_chip *chip);
> +#else
> +static inline int tpm2_start_auth_session(struct tpm_chip *chip)
> +{
> +	return 0;
> +}
> +static inline void tpm2_end_auth_session(struct tpm_chip *chip)
> +{
> +}
> +#endif	/* CONFIG_TCG_TPM2_HMAC */
> +
>  #endif


BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 14/21] tpm: Add HMAC session name/handle append
  2024-02-13 17:13 ` [PATCH v7 14/21] tpm: Add HMAC session name/handle append James Bottomley
@ 2024-02-23 17:06   ` Jarkko Sakkinen
  2024-04-29 20:11     ` James Bottomley
  0 siblings, 1 reply; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:06 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> Add tpm2_append_name() for appending to the handle area of the TPM
> command.  When TPM_BUS_SECURITY is enabled and HMAC sessions are in
> use this adds the standard u32 handle to the buffer but additionally
> records the name of the object which must be used as part of the HMAC
> computation.  The name of certain object types (volatile and permanent
> handles and NV indexes) is a hash of the public area of the object.
> Since this hash is not known ahead of time, it must be requested from
> the TPM using TPM2_ReadPublic() (which cannot be HMAC protected, but
> if an interposer lies about it, the HMAC check will fail and the
> problem will be detected).
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts
>
> ---
>
> v6: split into new patch, update config variable
> v7: add tpm2_ prefix
> ---
>  drivers/char/tpm/tpm2-sessions.c | 121 +++++++++++++++++++++++++++++++
>  include/linux/tpm.h              |  26 +++++++
>  2 files changed, 147 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index c8792a6b8bd4..9eb420d8e530 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -49,6 +49,11 @@
>   *	Under normal operation this function is done by
>   *	tpm_buf_check_hmac_response(), so this is only to be used on
>   *	error legs where the latter is not executed.
> + * tpm_buf_append_name() to add a handle to the buffer.  This must be
> + *	used in place of the usual tpm_buf_append_u32() for adding
> + *	handles because handles have to be processed specially when
> + *	calculating the HMAC.  In particular, for NV, volatile and
> + *	permanent objects you now need to provide the name.
>   */
>  
>  #include "tpm.h"
> @@ -106,8 +111,26 @@ struct tpm2_auth {
>  		u8 scratch[AES_KEYBYTES + AES_BLOCK_SIZE];
>  	};
>  	u8 session_key[SHA256_DIGEST_SIZE];
> +	/* 3 names of handles: name_h is handle, name is name of handle */
                                                 ~~~~~~~~~~~~
						 tautology, aka meaningless
						 expression, would work
						 better as name for
						 let's say
						 depeche mode song than
						 a comment :-)


> +	u32 name_h[AUTH_MAX_NAMES];
> +	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
>  };
>  
> +/*
> + * Name Size based on TPM algorithm (assumes no hash bigger than 255)
> + */
> +static u8 name_size(const u8 *name)
> +{
> +	static u8 size_map[] = {
> +		[TPM_ALG_SHA1] = SHA1_DIGEST_SIZE,
> +		[TPM_ALG_SHA256] = SHA256_DIGEST_SIZE,
> +		[TPM_ALG_SHA384] = SHA384_DIGEST_SIZE,
> +		[TPM_ALG_SHA512] = SHA512_DIGEST_SIZE,
> +	};
> +	u16 alg = get_unaligned_be16(name);
> +	return size_map[alg] + 2;
> +}
> +
>  /*
>   * It turns out the crypto hmac(sha256) is hard for us to consume
>   * because it assumes a fixed key and the TPM seems to change the key
> @@ -282,6 +305,104 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>   out:
>  	crypto_free_kpp(kpp);
>  }
> +
> +static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
> +{
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +	off_t offset = TPM_HEADER_SIZE;
> +	u32 tot_len = be32_to_cpu(head->length);
> +	u32 val;
> +
> +	/* we're starting after the header so adjust the length */
> +	tot_len -= TPM_HEADER_SIZE;
> +
> +	/* skip public */
> +	val = tpm_buf_read_u16(buf, &offset);
> +	if (val > tot_len)
> +		return -EINVAL;
> +	offset += val;
> +	/* name */
> +	val = tpm_buf_read_u16(buf, &offset);
> +	if (val != name_size(&buf->data[offset]))
> +		return -EINVAL;
> +	memcpy(name, &buf->data[offset], val);
> +	/* forget the rest */
> +	return 0;
> +}
> +
> +static int tpm2_readpublic(struct tpm_chip *chip, u32 handle, char *name)
		   read_public

> +{
> +	struct tpm_buf buf;
> +	int rc;
> +
> +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
> +	if (rc)
> +		return rc;
> +
> +	tpm_buf_append_u32(&buf, handle);
> +	rc = tpm_transmit_cmd(chip, &buf, 0, "read public");
> +	if (rc == TPM2_RC_SUCCESS)
> +		rc = tpm2_parse_read_public(name, &buf);
> +
> +	tpm_buf_destroy(&buf);
> +
> +	return rc;
> +}
> +
> +/**
> + * tpm_buf_append_name() - add a handle area to the buffer
> + * @chip: the TPM chip structure
> + * @buf: The buffer to be appended
> + * @handle: The handle to be appended
> + * @name: The name of the handle (may be NULL)
> + *
> + * In order to compute session HMACs, we need to know the names of the
> + * objects pointed to by the handles.  For most objects, this is simly
> + * the actual 4 byte handle or an empty buf (in these cases @name
> + * should be NULL) but for volatile objects, permanent objects and NV
> + * areas, the name is defined as the hash (according to the name
> + * algorithm which should be set to sha256) of the public area to
> + * which the two byte algorithm id has been appended.  For these
> + * objects, the @name pointer should point to this.  If a name is
> + * required but @name is NULL, then TPM2_ReadPublic() will be called
> + * on the handle to obtain the name.
> + *
> + * As with most tpm_buf operations, success is assumed because failure
> + * will be caused by an incorrect programming model and indicated by a
> + * kernel message.
> + */
> +void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
> +			 u32 handle, u8 *name)
> +{
> +	int slot;
> +	enum tpm2_mso_type mso = tpm2_handle_mso(handle);
> +	struct tpm2_auth *auth = chip->auth;

I'd consider re-order here too... I.e. put "int slot" as last.

> +
> +	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE)/4;
> +	if (slot >= AUTH_MAX_NAMES) {
> +		dev_err(&chip->dev, "TPM: too many handles\n");
> +		return;
> +	}
> +	WARN(auth->session != tpm_buf_length(buf),
> +	     "name added in wrong place\n");
> +	tpm_buf_append_u32(buf, handle);
> +	auth->session += 4;
> +
> +	if (mso == TPM2_MSO_PERSISTENT ||
> +	    mso == TPM2_MSO_VOLATILE ||
> +	    mso == TPM2_MSO_NVRAM) {
> +		if (!name)
> +			tpm2_readpublic(chip, handle, auth->name[slot]);
> +	} else {
> +		if (name)
> +			dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
> +	}
> +
> +	auth->name_h[slot] = handle;
> +	if (name)
> +		memcpy(auth->name[slot], name, name_size(name));
> +}
> +EXPORT_SYMBOL(tpm_buf_append_name);
>  /**
>   * tpm2_end_auth_session() - kill the allocated auth session
>   * @chip: the TPM chip structure
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 444f0a83682a..9b0b0d3c0d62 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -271,6 +271,7 @@ enum tpm2_command_codes {
>  	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
>  	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
>  	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
> +	TPM2_CC_READ_PUBLIC		= 0x0173,
>  	TPM2_CC_START_AUTH_SESS		= 0x0176,
>  	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
>  	TPM2_CC_GET_CAPABILITY	        = 0x017A,
> @@ -288,6 +289,21 @@ enum tpm2_permanent_handles {
>  	TPM2_RS_PW		= 0x40000009,
>  };
>  
> +/* Most Significant Octet for key types  */
> +enum tpm2_mso_type {
> +	TPM2_MSO_NVRAM		= 0x01,
> +	TPM2_MSO_SESSION	= 0x02,
> +	TPM2_MSO_POLICY		= 0x03,
> +	TPM2_MSO_PERMANENT	= 0x40,
> +	TPM2_MSO_VOLATILE	= 0x80,
> +	TPM2_MSO_PERSISTENT	= 0x81,
> +};
> +
> +static inline enum tpm2_mso_type tpm2_handle_mso(u32 handle)
> +{
> +	return handle >> 24;

did we have macro for this (cannot recall)? like oppposite
of BIT().

> +}
> +
>  enum tpm2_capabilities {
>  	TPM2_CAP_HANDLES	= 1,
>  	TPM2_CAP_COMMANDS	= 2,
> @@ -472,6 +488,8 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
>  #ifdef CONFIG_TCG_TPM2_HMAC
>  
>  int tpm2_start_auth_session(struct tpm_chip *chip);
> +void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
> +			 u32 handle, u8 *name);
>  void tpm2_end_auth_session(struct tpm_chip *chip);
>  #else
>  static inline int tpm2_start_auth_session(struct tpm_chip *chip)
> @@ -481,6 +499,14 @@ static inline int tpm2_start_auth_session(struct tpm_chip *chip)
>  static inline void tpm2_end_auth_session(struct tpm_chip *chip)
>  {
>  }
> +static inline void tpm_buf_append_name(struct tpm_chip *chip,
> +				       struct tpm_buf *buf,
> +				       u32 handle, u8 *name)
> +{
> +	tpm_buf_append_u32(buf, handle);
> +	/* count the number of handles in the upper bits of flags */
> +	buf->handles++;
> +}
>  #endif	/* CONFIG_TCG_TPM2_HMAC */
>  
>  #endif

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 15/21] tpm: Add the rest of the session HMAC API
  2024-02-13 17:13 ` [PATCH v7 15/21] tpm: Add the rest of the session HMAC API James Bottomley
@ 2024-02-23 17:10   ` Jarkko Sakkinen
  2024-04-29 20:11     ` James Bottomley
  0 siblings, 1 reply; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:10 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> The final pieces of the HMAC API are for manipulating the session area
> of the command.  To add an authentication HMAC session
> tpm_buf_append_hmac_session() is called where tpm2_append_auth() would
> go. If a non empty password is passed in, this is correctly added to
> the HMAC to prove knowledge of it without revealing it.  Note that if
> the session is only used to encrypt or decrypt parameters (no
> authentication) then tpm_buf_append_hmac_session_opt() must be used
> instead.  This functions identically to tpm_buf_append_hmac_session()
> when TPM_BUS_SECURITY is enabled, but differently when it isn't,
> because effectively nothing is appended to the session area.
>
> Next the parameters should be filled in for the command and finally
> tpm_buf_fill_hmac_session() is called immediatly prior to transmitting
> the command which computes the correct HMAC and places it in the
> command at the session location in the tpm buffer
>
> Finally, after tpm_transmit_cmd() is called,
> tpm_buf_check_hmac_response() is called to check that the returned
> HMAC matched and collect the new state for the next use of the
> session, if any.
>
> The features of the session are controlled by the session attributes
> set in tpm_buf_append_hmac_session().  If TPM2_SA_CONTINUE_SESSION is
> not specified, the session will be flushed and the tpm2_auth structure
> freed in tpm_buf_check_hmac_response(); otherwise the session may be
> used again.  Parameter encryption is specified by or'ing the flag
> TPM2_SA_DECRYPT and response encryption by or'ing the flag
> TPM2_SA_ENCRYPT.  the various encryptions will be taken care of by
> tpm_buf_fill_hmac_session() and tpm_buf_check_hmac_response()
> respectively.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> # crypto API parts
>
> ---
>
> v6: split into new patch, update config variable
> v7: add memzero_explicit
> ---
>  drivers/char/tpm/tpm2-sessions.c | 400 +++++++++++++++++++++++++++++++
>  include/linux/tpm.h              |  69 ++++++
>  2 files changed, 469 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 9eb420d8e530..9d6da0c9652f 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -54,6 +54,18 @@
>   *	handles because handles have to be processed specially when
>   *	calculating the HMAC.  In particular, for NV, volatile and
>   *	permanent objects you now need to provide the name.
> + * tpm_buf_append_hmac_session() which appends the hmac session to the
> + *	buf in the same way tpm_buf_append_auth does().
> + * tpm_buf_fill_hmac_session() This calculates the correct hash and
> + *	places it in the buffer.  It must be called after the complete
> + *	command buffer is finalized so it can fill in the correct HMAC
> + *	based on the parameters.
> + * tpm_buf_check_hmac_response() which checks the session response in
> + *	the buffer and calculates what it should be.  If there's a
> + *	mismatch it will log a warning and return an error.  If
> + *	tpm_buf_append_hmac_session() did not specify
> + *	TPM_SA_CONTINUE_SESSION then the session will be closed (if it
> + *	hasn't been consumed) and the auth structure freed.
>   */
>  
>  #include "tpm.h"
> @@ -110,7 +122,23 @@ struct tpm2_auth {
>  		/* scratch for key + IV */
>  		u8 scratch[AES_KEYBYTES + AES_BLOCK_SIZE];
>  	};
> +	/*
> +	 * the session key and passphrase are the same size as the
> +	 * name digest (sha256 again).  The session key is constant
> +	 * for the use of the session and the passphrase can change
> +	 * with every invocation.
> +	 *
> +	 * Note: these fields must be adjacent and in this order
> +	 * because several HMAC/KDF schemes use the combination of the
> +	 * session_key and passphrase.
> +	 */
>  	u8 session_key[SHA256_DIGEST_SIZE];
> +	u8 passphrase[SHA256_DIGEST_SIZE];
> +	int passphraselen;
> +	struct crypto_aes_ctx aes_ctx;
> +	/* saved session attributes */

nit: "Saved session attributes:"

This makes just dead obvious that what  follows are what we are
referring to.

> +	u8 attrs;
> +	__be32 ordinal;
>  	/* 3 names of handles: name_h is handle, name is name of handle */
>  	u32 name_h[AUTH_MAX_NAMES];
>  	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
> @@ -306,6 +334,230 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>  	crypto_free_kpp(kpp);
>  }
>  
> +/**
> + * tpm_buf_append_hmac_session() - append a TPM session element
                                      ~
				      A

At least in the documentation these start with capital letter.


> + * @chip: the TPM chip structure
> + * @buf: The buffer to be appended
> + * @attributes: The session attributes
> + * @passphrase: The session authority (NULL if none)
> + * @passphraselen: The length of the session authority (0 if none)

passphrase_len

> + *
> + * This fills in a session structure in the TPM command buffer, except
> + * for the HMAC which cannot be computed until the command buffer is
> + * complete.  The type of session is controlled by the @attributes,
> + * the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
> + * session won't terminate after tpm_buf_check_hmac_response(),
> + * TPM2_SA_DECRYPT which means this buffers first parameter should be
> + * encrypted with a session key and TPM2_SA_ENCRYPT, which means the
> + * response buffer's first parameter needs to be decrypted (confusing,
> + * but the defines are written from the point of view of the TPM).
> + *
> + * Any session appended by this command must be finalized by calling
> + * tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
> + * and the TPM will reject the command.
> + *
> + * As with most tpm_buf operations, success is assumed because failure
> + * will be caused by an incorrect programming model and indicated by a
> + * kernel message.
> + */
> +void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
> +				 u8 attributes, u8 *passphrase,
> +				 int passphraselen)
> +{
> +	u8 nonce[SHA256_DIGEST_SIZE];
> +	u32 len;
> +	struct tpm2_auth *auth = chip->auth;

re-order

> +
> +	/*
> +	 * The Architecture Guide requires us to strip trailing zeros
> +	 * before computing the HMAC
> +	 */
> +	while (passphrase && passphraselen > 0
> +	       && passphrase[passphraselen - 1] == '\0')
> +		passphraselen--;
> +
> +	auth->attrs = attributes;
> +	auth->passphraselen = passphraselen;
> +	if (passphraselen)
> +		memcpy(auth->passphrase, passphrase, passphraselen);
> +
> +	if (auth->session != tpm_buf_length(buf)) {
> +		/* we're not the first session */
> +		len = get_unaligned_be32(&buf->data[auth->session]);
> +		if (4 + len + auth->session != tpm_buf_length(buf)) {
> +			WARN(1, "session length mismatch, cannot append");
> +			return;
> +		}
> +
> +		/* add our new session */
> +		len += 9 + 2 * SHA256_DIGEST_SIZE;
> +		put_unaligned_be32(len, &buf->data[auth->session]);
> +	} else {
> +		tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
> +	}
> +
> +	/* random number for our nonce */
> +	get_random_bytes(nonce, sizeof(nonce));
> +	memcpy(auth->our_nonce, nonce, sizeof(nonce));
> +	tpm_buf_append_u32(buf, auth->handle);
> +	/* our new nonce */
> +	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
> +	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
> +	tpm_buf_append_u8(buf, auth->attrs);
> +	/* and put a placeholder for the hmac */
> +	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
> +	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
> +}
> +EXPORT_SYMBOL(tpm_buf_append_hmac_session);
> +
> +/**
> + * tpm_buf_fill_hmac_session() - finalize the session HMAC
> + * @chip: the TPM chip structure
> + * @buf: The buffer to be appended
> + *
> + * This command must not be called until all of the parameters have
> + * been appended to @buf otherwise the computed HMAC will be
> + * incorrect.
> + *
> + * This function computes and fills in the session HMAC using the
> + * session key and, if TPM2_SA_DECRYPT was specified, computes the
> + * encryption key and encrypts the first parameter of the command
> + * buffer with it.
> + *
> + * As with most tpm_buf operations, success is assumed because failure
> + * will be caused by an incorrect programming model and indicated by a
> + * kernel message.
> + */
> +void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
> +{
> +	u32 cc, handles, val;
> +	struct tpm2_auth *auth = chip->auth;
> +	int i;
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +	off_t offset_s = TPM_HEADER_SIZE, offset_p;
> +	u8 *hmac = NULL;
> +	u32 attrs;
> +	u8 cphash[SHA256_DIGEST_SIZE];
> +	struct sha256_state sctx;


definitely re-order

> +
> +	/* save the command code in BE format */
> +	auth->ordinal = head->ordinal;
> +
> +	cc = be32_to_cpu(head->ordinal);
> +
> +	i = tpm2_find_cc(chip, cc);
> +	if (i < 0) {
> +		dev_err(&chip->dev, "Command 0x%x not found in TPM\n", cc);
> +		return;
> +	}
> +	attrs = chip->cc_attrs_tbl[i];
> +
> +	handles = (attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0);
> +
> +	/*
> +	 * just check the names, it's easy to make mistakes.  This
> +	 * would happen if someone added a handle via
> +	 * tpm_buf_append_u32() instead of tpm_buf_append_name()
> +	 */
> +	for (i = 0; i < handles; i++) {
> +		u32 handle = tpm_buf_read_u32(buf, &offset_s);
> +
> +		if (auth->name_h[i] != handle) {
> +			dev_err(&chip->dev, "TPM: handle %d wrong for name\n",
> +				  i);
> +			return;
> +		}
> +	}
> +	/* point offset_s to the start of the sessions */
> +	val = tpm_buf_read_u32(buf, &offset_s);
> +	/* point offset_p to the start of the parameters */
> +	offset_p = offset_s + val;
> +	for (i = 1; offset_s < offset_p; i++) {
> +		u32 handle = tpm_buf_read_u32(buf, &offset_s);
> +		u16 len;
> +		u8 a;
> +
> +		/* nonce (already in auth) */
> +		len = tpm_buf_read_u16(buf, &offset_s);
> +		offset_s += len;
> +
> +		a = tpm_buf_read_u8(buf, &offset_s);
> +
> +		len = tpm_buf_read_u16(buf, &offset_s);
> +		if (handle == auth->handle && auth->attrs == a) {
> +			hmac = &buf->data[offset_s];
> +			/*
> +			 * save our session number so we know which
> +			 * session in the response belongs to us
> +			 */
> +			auth->session = i;
> +		}
> +
> +		offset_s += len;
> +	}
> +	if (offset_s != offset_p) {
> +		dev_err(&chip->dev, "TPM session length is incorrect\n");
> +		return;
> +	}
> +	if (!hmac) {
> +		dev_err(&chip->dev, "TPM could not find HMAC session\n");
> +		return;
> +	}
> +
> +	/* encrypt before HMAC */
> +	if (auth->attrs & TPM2_SA_DECRYPT) {
> +		u16 len;
> +
> +		/* need key and IV */
> +		KDFa(auth->session_key, SHA256_DIGEST_SIZE
> +		     + auth->passphraselen, "CFB", auth->our_nonce,
> +		     auth->tpm_nonce, AES_KEYBYTES + AES_BLOCK_SIZE,
> +		     auth->scratch);
> +
> +		len = tpm_buf_read_u16(buf, &offset_p);
> +		aes_expandkey(&auth->aes_ctx, auth->scratch, AES_KEYBYTES);
> +		aescfb_encrypt(&auth->aes_ctx, &buf->data[offset_p],
> +			       &buf->data[offset_p], len,
> +			       auth->scratch + AES_KEYBYTES);
> +		/* reset p to beginning of parameters for HMAC */
> +		offset_p -= 2;
> +	}
> +
> +	sha256_init(&sctx);
> +	/* ordinal is already BE */
> +	sha256_update(&sctx, (u8 *)&head->ordinal, sizeof(head->ordinal));
> +	/* add the handle names */
> +	for (i = 0; i < handles; i++) {
> +		enum tpm2_mso_type mso = tpm2_handle_mso(auth->name_h[i]);
> +
> +		if (mso == TPM2_MSO_PERSISTENT ||
> +		    mso == TPM2_MSO_VOLATILE ||
> +		    mso == TPM2_MSO_NVRAM) {
> +			sha256_update(&sctx, auth->name[i],
> +				      name_size(auth->name[i]));
> +		} else {
> +			__be32 h = cpu_to_be32(auth->name_h[i]);
> +
> +			sha256_update(&sctx, (u8 *)&h, 4);
> +		}
> +	}
> +	if (offset_s != tpm_buf_length(buf))
> +		sha256_update(&sctx, &buf->data[offset_s],
> +			      tpm_buf_length(buf) - offset_s);
> +	sha256_final(&sctx, cphash);
> +
> +	/* now calculate the hmac */
> +	hmac_init(&sctx, auth->session_key, sizeof(auth->session_key)
> +		  + auth->passphraselen);
> +	sha256_update(&sctx, cphash, sizeof(cphash));
> +	sha256_update(&sctx, auth->our_nonce, sizeof(auth->our_nonce));
> +	sha256_update(&sctx, auth->tpm_nonce, sizeof(auth->tpm_nonce));
> +	sha256_update(&sctx, &auth->attrs, 1);
> +	hmac_final(&sctx, auth->session_key, sizeof(auth->session_key)
> +		   + auth->passphraselen, hmac);
> +}
> +EXPORT_SYMBOL(tpm_buf_fill_hmac_session);
> +
>  static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
>  {
>  	struct tpm_header *head = (struct tpm_header *)buf->data;
> @@ -403,6 +655,154 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
>  		memcpy(auth->name[slot], name, name_size(name));
>  }
>  EXPORT_SYMBOL(tpm_buf_append_name);
> +
> +/**
> + * tpm_buf_check_hmac_response() - check the TPM return HMAC for correctness
> + * @chip: the TPM chip structure
> + * @buf: the original command buffer (which now contains the response)
> + * @rc: the return code from tpm_transmit_cmd
> + *
> + * If @rc is non zero, @buf may not contain an actual return, so @rc
> + * is passed through as the return and the session cleaned up and
> + * de-allocated if required (this is required if
> + * TPM2_SA_CONTINUE_SESSION was not specified as a session flag).
> + *
> + * If @rc is zero, the response HMAC is computed against the returned
> + * @buf and matched to the TPM one in the session area.  If there is a
> + * mismatch, an error is logged and -EINVAL returned.
> + *
> + * The reason for this is that the command issue and HMAC check
> + * sequence should look like:
> + *
> + *	rc = tpm_transmit_cmd(...);
> + *	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
> + *	if (rc)
> + *		...
> + *
> + * Which is easily layered into the current contrl flow.
> + *
> + * Returns: 0 on success or an error.
> + */
> +int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
> +				int rc)
> +{
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +	struct tpm2_auth *auth = chip->auth;
> +	off_t offset_s, offset_p;
> +	u8 rphash[SHA256_DIGEST_SIZE];
> +	u32 attrs;
> +	struct sha256_state sctx;
> +	u16 tag = be16_to_cpu(head->tag);
> +	u32 cc = be32_to_cpu(auth->ordinal);
> +	int parm_len, len, i, handles;

ditto

> +
> +	if (auth->session >= TPM_HEADER_SIZE) {
> +		WARN(1, "tpm session not filled correctly\n");
> +		goto out;
> +	}
> +
> +	if (rc != 0)
> +		/* pass non success rc through and close the session */
> +		goto out;
> +
> +	rc = -EINVAL;
> +	if (tag != TPM2_ST_SESSIONS) {
> +		dev_err(&chip->dev, "TPM: HMAC response check has no sessions tag\n");
> +		goto out;
> +	}
> +
> +	i = tpm2_find_cc(chip, cc);
> +	if (i < 0)
> +		goto out;
> +	attrs = chip->cc_attrs_tbl[i];
> +	handles = (attrs >> TPM2_CC_ATTR_RHANDLE) & 1;
> +
> +	/* point to area beyond handles */
> +	offset_s = TPM_HEADER_SIZE + handles * 4;
> +	parm_len = tpm_buf_read_u32(buf, &offset_s);
> +	offset_p = offset_s;
> +	offset_s += parm_len;
> +	/* skip over any sessions before ours */
> +	for (i = 0; i < auth->session - 1; i++) {
> +		len = tpm_buf_read_u16(buf, &offset_s);
> +		offset_s += len + 1;
> +		len = tpm_buf_read_u16(buf, &offset_s);
> +		offset_s += len;
> +	}
> +	/* TPM nonce */
> +	len = tpm_buf_read_u16(buf, &offset_s);
> +	if (offset_s + len > tpm_buf_length(buf))
> +		goto out;
> +	if (len != SHA256_DIGEST_SIZE)
> +		goto out;
> +	memcpy(auth->tpm_nonce, &buf->data[offset_s], len);
> +	offset_s += len;
> +	attrs = tpm_buf_read_u8(buf, &offset_s);
> +	len = tpm_buf_read_u16(buf, &offset_s);
> +	if (offset_s + len != tpm_buf_length(buf))
> +		goto out;
> +	if (len != SHA256_DIGEST_SIZE)
> +		goto out;
> +	/*
> +	 * offset_s points to the HMAC. now calculate comparison, beginning
> +	 * with rphash
> +	 */
> +	sha256_init(&sctx);
> +	/* yes, I know this is now zero, but it's what the standard says */
> +	sha256_update(&sctx, (u8 *)&head->return_code,
> +		      sizeof(head->return_code));
> +	/* ordinal is already BE */
> +	sha256_update(&sctx, (u8 *)&auth->ordinal, sizeof(auth->ordinal));
> +	sha256_update(&sctx, &buf->data[offset_p], parm_len);
> +	sha256_final(&sctx, rphash);
> +
> +	/* now calculate the hmac */
> +	hmac_init(&sctx, auth->session_key, sizeof(auth->session_key)
> +		  + auth->passphraselen);
> +	sha256_update(&sctx, rphash, sizeof(rphash));
> +	sha256_update(&sctx, auth->tpm_nonce, sizeof(auth->tpm_nonce));
> +	sha256_update(&sctx, auth->our_nonce, sizeof(auth->our_nonce));
> +	sha256_update(&sctx, &auth->attrs, 1);
> +	/* we're done with the rphash, so put our idea of the hmac there */
> +	hmac_final(&sctx, auth->session_key, sizeof(auth->session_key)
> +		   + auth->passphraselen, rphash);
> +	if (memcmp(rphash, &buf->data[offset_s], SHA256_DIGEST_SIZE) == 0) {
> +		rc = 0;
> +	} else {
> +		dev_err(&chip->dev, "TPM: HMAC check failed\n");
> +		goto out;
> +	}
> +
> +	/* now do response decryption */
> +	if (auth->attrs & TPM2_SA_ENCRYPT) {
> +		/* need key and IV */
> +		KDFa(auth->session_key, SHA256_DIGEST_SIZE
> +		     + auth->passphraselen, "CFB", auth->tpm_nonce,
> +		     auth->our_nonce, AES_KEYBYTES + AES_BLOCK_SIZE,
> +		     auth->scratch);

OK, since there is multiple patches with KDF* dep the KDF functions
should be their own separate patch not glued into any patch that uses
them.

> +
> +		len = tpm_buf_read_u16(buf, &offset_p);
> +		aes_expandkey(&auth->aes_ctx, auth->scratch, AES_KEYBYTES);
> +		aescfb_decrypt(&auth->aes_ctx, &buf->data[offset_p],
> +			       &buf->data[offset_p], len,
> +			       auth->scratch + AES_KEYBYTES);
> +	}
> +
> + out:
> +	if ((auth->attrs & TPM2_SA_CONTINUE_SESSION) == 0) {
> +		if (rc)
> +			/* manually close the session if it wasn't consumed */
> +			tpm2_flush_context(chip, auth->handle);
> +		memzero_explicit(auth, sizeof(*auth));
> +	} else {
> +		/* reset for next use  */
> +		auth->session = TPM_HEADER_SIZE;
> +	}
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL(tpm_buf_check_hmac_response);
> +
>  /**
>   * tpm2_end_auth_session() - kill the allocated auth session
>   * @chip: the TPM chip structure
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 9b0b0d3c0d62..9c608fac8935 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -490,8 +490,25 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
>  int tpm2_start_auth_session(struct tpm_chip *chip);
>  void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
>  			 u32 handle, u8 *name);
> +void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
> +				 u8 attributes, u8 *passphrase,
> +				 int passphraselen);
> +static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
> +						   struct tpm_buf *buf,
> +						   u8 attributes,
> +						   u8 *passphrase,
> +						   int passphraselen)
> +{
> +	tpm_buf_append_hmac_session(chip, buf, attributes, passphrase,
> +				    passphraselen);
> +}
> +void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf);
> +int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
> +				int rc);
>  void tpm2_end_auth_session(struct tpm_chip *chip);
>  #else
> +#include <asm/unaligned.h>
> +
>  static inline int tpm2_start_auth_session(struct tpm_chip *chip)
>  {
>  	return 0;
> @@ -507,6 +524,58 @@ static inline void tpm_buf_append_name(struct tpm_chip *chip,
>  	/* count the number of handles in the upper bits of flags */
>  	buf->handles++;
>  }
> +static inline void tpm_buf_append_hmac_session(struct tpm_chip *chip,
> +					       struct tpm_buf *buf,
> +					       u8 attributes, u8 *passphrase,
> +					       int passphraselen)
> +{
> +	/* offset tells us where the sessions area begins */
> +	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
> +	u32 len = 9 + passphraselen;
> +
> +	if (tpm_buf_length(buf) != offset) {
> +		/* not the first session so update the existing length */
> +		len += get_unaligned_be32(&buf->data[offset]);
> +		put_unaligned_be32(len, &buf->data[offset]);
> +	} else {
> +		tpm_buf_append_u32(buf, len);
> +	}
> +	/* auth handle */
> +	tpm_buf_append_u32(buf, TPM2_RS_PW);
> +	/* nonce */
> +	tpm_buf_append_u16(buf, 0);
> +	/* attributes */
> +	tpm_buf_append_u8(buf, 0);
> +	/* passphrase */
> +	tpm_buf_append_u16(buf, passphraselen);
> +	tpm_buf_append(buf, passphrase, passphraselen);
> +}
> +static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
> +						   struct tpm_buf *buf,
> +						   u8 attributes,
> +						   u8 *passphrase,
> +						   int passphraselen)
> +{
> +	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
> +	struct tpm_header *head = (struct tpm_header *) buf->data;
> +
> +	/*
> +	 * if the only sessions are optional, the command tag
> +	 * must change to TPM2_ST_NO_SESSIONS
> +	 */
> +	if (tpm_buf_length(buf) == offset)
> +		head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
> +}
> +static inline void tpm_buf_fill_hmac_session(struct tpm_chip *chip,
> +					     struct tpm_buf *buf)
> +{
> +}
> +static inline int tpm_buf_check_hmac_response(struct tpm_chip *chip,
> +					      struct tpm_buf *buf,
> +					      int rc)
> +{
> +	return rc;
> +}
>  #endif	/* CONFIG_TCG_TPM2_HMAC */
>  
>  #endif


BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 16/21] tpm: add hmac checks to tpm2_pcr_extend()
  2024-02-13 17:13 ` [PATCH v7 16/21] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
@ 2024-02-23 17:10   ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:10 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> tpm2_pcr_extend() is used by trusted keys to extend a PCR to prevent a
> key from being re-loaded until the next reboot.  To use this
> functionality securely, that extend must be protected by a session
> hmac.  This patch adds HMAC protection so tampering with the
> tpm2_pcr_extend() command in flight is detected.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
>
> ---
> v7: add review
> ---
>  drivers/char/tpm/tpm2-cmd.c | 27 ++++++++++-----------------
>  1 file changed, 10 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index b0e72fb563d9..a53a843294ed 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -216,13 +216,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
>  	return rc;
>  }
>  
> -struct tpm2_null_auth_area {
> -	__be32  handle;
> -	__be16  nonce_size;
> -	u8  attributes;
> -	__be16  auth_size;
> -} __packed;
> -
>  /**
>   * tpm2_pcr_extend() - extend a PCR value
>   *
> @@ -236,24 +229,22 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
>  		    struct tpm_digest *digests)
>  {
>  	struct tpm_buf buf;
> -	struct tpm2_null_auth_area auth_area;
>  	int rc;
>  	int i;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
> +	rc = tpm2_start_auth_session(chip);
>  	if (rc)
>  		return rc;
>  
> -	tpm_buf_append_u32(&buf, pcr_idx);
> +	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
> +	if (rc) {
> +		tpm2_end_auth_session(chip);
> +		return rc;
> +	}
>  
> -	auth_area.handle = cpu_to_be32(TPM2_RS_PW);
> -	auth_area.nonce_size = 0;
> -	auth_area.attributes = 0;
> -	auth_area.auth_size = 0;
> +	tpm_buf_append_name(chip, &buf, pcr_idx, NULL);
> +	tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0);
>  
> -	tpm_buf_append_u32(&buf, sizeof(struct tpm2_null_auth_area));
> -	tpm_buf_append(&buf, (const unsigned char *)&auth_area,
> -		       sizeof(auth_area));
>  	tpm_buf_append_u32(&buf, chip->nr_allocated_banks);
>  
>  	for (i = 0; i < chip->nr_allocated_banks; i++) {
> @@ -262,7 +253,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
>  			       chip->allocated_banks[i].digest_size);
>  	}
>  
> +	tpm_buf_fill_hmac_session(chip, &buf);
>  	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value");
> +	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
>  
>  	tpm_buf_destroy(&buf);
>  


reviewed-by still applies

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 17/21] tpm: add session encryption protection to tpm2_get_random()
  2024-02-13 17:13 ` [PATCH v7 17/21] tpm: add session encryption protection to tpm2_get_random() James Bottomley
@ 2024-02-23 17:10   ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:10 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> If some entity is snooping the TPM bus, they can see the random
> numbers we're extracting from the TPM and do prediction attacks
> against their consumers.  Foil this attack by using response
> encryption to prevent the attacker from seeing the random sequence.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
>
> ---
> v7: add review
> ---
>  drivers/char/tpm/tpm2-cmd.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index a53a843294ed..0cdf892ec2a7 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -292,25 +292,35 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  	if (!num_bytes || max > TPM_MAX_RNG_DATA)
>  		return -EINVAL;
>  
> -	err = tpm_buf_init(&buf, 0, 0);
> +	err = tpm2_start_auth_session(chip);
>  	if (err)
>  		return err;
>  
> +	err = tpm_buf_init(&buf, 0, 0);
> +	if (err) {
> +		tpm2_end_auth_session(chip);
> +		return err;
> +	}
> +
>  	do {
> -		tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
> +		tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
> +		tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT
> +						| TPM2_SA_CONTINUE_SESSION,
> +						NULL, 0);
>  		tpm_buf_append_u16(&buf, num_bytes);
> +		tpm_buf_fill_hmac_session(chip, &buf);
>  		err = tpm_transmit_cmd(chip, &buf,
>  				       offsetof(struct tpm2_get_random_out,
>  						buffer),
>  				       "attempting get random");
> +		err = tpm_buf_check_hmac_response(chip, &buf, err);
>  		if (err) {
>  			if (err > 0)
>  				err = -EIO;
>  			goto out;
>  		}
>  
> -		out = (struct tpm2_get_random_out *)
> -			&buf.data[TPM_HEADER_SIZE];
> +		out = (struct tpm2_get_random_out *)tpm_buf_parameters(&buf);
>  		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
>  		if (tpm_buf_length(&buf) <
>  		    TPM_HEADER_SIZE +
> @@ -327,9 +337,12 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  	} while (retries-- && total < max);
>  
>  	tpm_buf_destroy(&buf);
> +	tpm2_end_auth_session(chip);
> +
>  	return total ? total : -EIO;
>  out:
>  	tpm_buf_destroy(&buf);
> +	tpm2_end_auth_session(chip);
>  	return err;
>  }
>  

ditto

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 18/21] KEYS: trusted: Add session encryption protection to the seal/unseal path
  2024-02-13 17:13 ` [PATCH v7 18/21] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
@ 2024-02-23 17:11   ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:11 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> If some entity is snooping the TPM bus, the can see the data going in
> to be sealed and the data coming out as it is unsealed.  Add parameter
> and response encryption to these cases to ensure that no secrets are
> leaked even if the bus is snooped.
>
> As part of doing this conversion it was discovered that policy
> sessions can't work with HMAC protected authority because of missing
> pieces (the tpm Nonce).  I've added code to work the same way as
> before, which will result in potential authority exposure (while still
> adding security for the command and the returned blob), and a fixme to
> redo the API to get rid of this security hole.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
>
> ---
> v2: fix unseal with policy and password
> v3: fix session memory leak
> v7: add review
> ---
>  security/keys/trusted-keys/trusted_tpm2.c | 88 ++++++++++++++++-------
>  1 file changed, 61 insertions(+), 27 deletions(-)
>
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 97b1dfca2dba..dfeec06301ce 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -253,26 +253,26 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  	if (rc)
>  		return rc;
>  
> +	rc = tpm2_start_auth_session(chip);
> +	if (rc)
> +		goto out_put;
> +
>  	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
>  	if (rc) {
> -		tpm_put_ops(chip);
> -		return rc;
> +		tpm2_end_auth_session(chip);
> +		goto out_put;
>  	}
>  
>  	rc = tpm_buf_init_sized(&sized);
>  	if (rc) {
>  		tpm_buf_destroy(&buf);
> -		tpm_put_ops(chip);
> -		return rc;
> +		tpm2_end_auth_session(chip);
> +		goto out_put;
>  	}
>  
> -	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
> -	tpm_buf_append_u32(&buf, options->keyhandle);
> -	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
> -			     NULL /* nonce */, 0,
> -			     0 /* session_attributes */,
> -			     options->keyauth /* hmac */,
> -			     TPM_DIGEST_SIZE);
> +	tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
> +	tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT,
> +				    options->keyauth, TPM_DIGEST_SIZE);
>  
>  	/* sensitive */
>  	tpm_buf_append_u16(&sized, options->blobauth_len);
> @@ -314,10 +314,13 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  
>  	if (buf.flags & TPM_BUF_OVERFLOW) {
>  		rc = -E2BIG;
> +		tpm2_end_auth_session(chip);
>  		goto out;
>  	}
>  
> +	tpm_buf_fill_hmac_session(chip, &buf);
>  	rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data");
> +	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
>  	if (rc)
>  		goto out;
>  
> @@ -348,6 +351,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  	else
>  		payload->blob_len = blob_len;
>  
> +out_put:
>  	tpm_put_ops(chip);
>  	return rc;
>  }
> @@ -417,25 +421,31 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  	if (blob_len > payload->blob_len)
>  		return -E2BIG;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
> +	rc = tpm2_start_auth_session(chip);
>  	if (rc)
>  		return rc;
>  
> -	tpm_buf_append_u32(&buf, options->keyhandle);
> -	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
> -			     NULL /* nonce */, 0,
> -			     0 /* session_attributes */,
> -			     options->keyauth /* hmac */,
> -			     TPM_DIGEST_SIZE);
> +	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
> +	if (rc) {
> +		tpm2_end_auth_session(chip);
> +		return rc;
> +	}
> +
> +	tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
> +	tpm_buf_append_hmac_session(chip, &buf, 0, options->keyauth,
> +				    TPM_DIGEST_SIZE);
>  
>  	tpm_buf_append(&buf, blob, blob_len);
>  
>  	if (buf.flags & TPM_BUF_OVERFLOW) {
>  		rc = -E2BIG;
> +		tpm2_end_auth_session(chip);
>  		goto out;
>  	}
>  
> +	tpm_buf_fill_hmac_session(chip, &buf);
>  	rc = tpm_transmit_cmd(chip, &buf, 4, "loading blob");
> +	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
>  	if (!rc)
>  		*blob_handle = be32_to_cpup(
>  			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
> @@ -473,20 +483,44 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>  	u8 *data;
>  	int rc;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> +	rc = tpm2_start_auth_session(chip);
>  	if (rc)
>  		return rc;
>  
> -	tpm_buf_append_u32(&buf, blob_handle);
> -	tpm2_buf_append_auth(&buf,
> -			     options->policyhandle ?
> -			     options->policyhandle : TPM2_RS_PW,
> -			     NULL /* nonce */, 0,
> -			     TPM2_SA_CONTINUE_SESSION,
> -			     options->blobauth /* hmac */,
> -			     options->blobauth_len);
> +	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> +	if (rc) {
> +		tpm2_end_auth_session(chip);
> +		return rc;
> +	}
> +
> +	tpm_buf_append_name(chip, &buf, blob_handle, NULL);
> +
> +	if (!options->policyhandle) {
> +		tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT,
> +					    options->blobauth,
> +					    options->blobauth_len);
> +	} else {
> +		/*
> +		 * FIXME: The policy session was generated outside the
> +		 * kernel so we don't known the nonce and thus can't
> +		 * calculate a HMAC on it.  Therefore, the user can
> +		 * only really use TPM2_PolicyPassword and we must
> +		 * send down the plain text password, which could be
> +		 * intercepted.  We can still encrypt the returned
> +		 * key, but that's small comfort since the interposer
> +		 * could repeat our actions with the exfiltrated
> +		 * password.
> +		 */
> +		tpm2_buf_append_auth(&buf, options->policyhandle,
> +				     NULL /* nonce */, 0, 0,
> +				     options->blobauth, options->blobauth_len);
> +		tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT,
> +						NULL, 0);
> +	}
>  
> +	tpm_buf_fill_hmac_session(chip, &buf);
>  	rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
> +	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
>  	if (rc > 0)
>  		rc = -EPERM;
>  


ditto

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 19/21] tpm: add the null key name as a sysfs export
  2024-02-13 17:13 ` [PATCH v7 19/21] tpm: add the null key name as a sysfs export James Bottomley
@ 2024-02-23 17:15   ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 17:15 UTC (permalink / raw)
  To: James Bottomley, linux-integrity, David Howells; +Cc: keyrings, Ard Biesheuvel


[-- Attachment #1.1: Type: text/plain, Size: 2731 bytes --]

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> This is the last component of encrypted tpm2 session handling that
> allows us to verify from userspace that the key derived from the NULL
> seed genuinely belongs to the TPM and has not been spoofed.
>
> The procedure for doing this involves creating an attestation identity
> key (which requires verification of the TPM EK certificate) and then
> using that AIK to sign a certification of the Elliptic Curve key over
> the NULL seed.  Userspace must create this EC Key using the parameters
> prescribed in TCG TPM v2.0 Provisioning Guidance for the SRK ECC; if
> this is done correctly the names will match and the TPM can then run a
> TPM2_Certify operation on this derived primary key using the newly
> created AIK.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
>
> ---
> v6: change config name
> v7: add review
> ---
>  drivers/char/tpm/tpm-sysfs.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 54c71473aa29..94231f052ea7 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -309,6 +309,21 @@ static ssize_t tpm_version_major_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(tpm_version_major);
>  
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +static ssize_t null_name_show(struct device *dev, struct device_attribute *attr,
> +			      char *buf)
> +{
> +	struct tpm_chip *chip = to_tpm_chip(dev);
> +	int size = TPM2_NAME_SIZE;
> +
> +	bin2hex(buf, chip->null_key_name, size);
> +	size *= 2;
> +	buf[size++] = '\n';
> +	return size;
> +}
> +static DEVICE_ATTR_RO(null_name);
> +#endif
> +
>  static struct attribute *tpm1_dev_attrs[] = {
>  	&dev_attr_pubek.attr,
>  	&dev_attr_pcrs.attr,
> @@ -326,6 +341,9 @@ static struct attribute *tpm1_dev_attrs[] = {
>  
>  static struct attribute *tpm2_dev_attrs[] = {
>  	&dev_attr_tpm_version_major.attr,
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +	&dev_attr_null_name.attr,
> +#endif
>  	NULL
>  };
>  

Ditto.

Could also have my tested-by. I removed my test suite from Github.
Soon relocating it to gitlab. The reason being that I'm also
enabling full keyutils test suite in it and in more distant
future might refactor it into a CI test (ATM do not have
bandwidth to accomplish the last step).

David, I've been carrying couple of minor fixes to keyutils test.
When you have time, could you check if they make sense (attached).

Came to mind while reviewing this and they are pretty small so
maybe they could be picked like this.

BR, Jarkko

[-- Attachment #2: 0001-test-lsb_release-fix.patch --]
[-- Type: text/x-patch, Size: 1232 bytes --]

From d3472a81decc0a982b8154be7b873436a91873d8 Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko@kernel.org>
Date: Tue, 19 Dec 2023 12:27:09 +0200
Subject: [PATCH 1/4] test: check for lsb_release command existence before
 applying it

Requiring `lsb_release` makes keyutils test suite very unrobust towards
CI. Therefore, check its existence before applying the command.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 tests/prepare.inc.sh | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tests/prepare.inc.sh b/tests/prepare.inc.sh
index 4033d69..1a1acc9 100644
--- a/tests/prepare.inc.sh
+++ b/tests/prepare.inc.sh
@@ -66,13 +66,16 @@ then
     echo -n >$OUTPUTFILE
 fi
 
-case `lsb_release -i -s` in
-    Fedora*)		OSDIST=Fedora;;
-    RedHatEnterprise*)	OSDIST=RHEL;;
-    *)			OSDIST=Unknown;;
-esac
+if command -v lsb_release &> /dev/null
+then
+    case `lsb_release -i -s` in
+        Fedora*)            OSDIST=Fedora;;
+        RedHatEnterprise*)  OSDIST=RHEL;;
+        *)                  OSDIST=Unknown;;
+    esac
 
-OSRELEASE=`lsb_release -r -s`
+    OSRELEASE=`lsb_release -r -s`
+fi
 
 KEYUTILSVER=`keyctl --version 2>/dev/null`
 if [ -n "$KEYUTILSVER" ]
-- 
2.40.1


[-- Attachment #3: 0002-test-fix-typo.patch --]
[-- Type: text/x-patch, Size: 976 bytes --]

From 19d54acb57e8960e386119088d57e2385c71862c Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko@kernel.org>
Date: Fri, 22 Dec 2023 21:42:11 +0200
Subject: [PATCH 2/4] test: fix typo in builtin_trusted/runtest.sh

s/fail/failed/

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 tests/features/builtin_trusted/runtest.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/features/builtin_trusted/runtest.sh b/tests/features/builtin_trusted/runtest.sh
index 6bd073b..c0736d6 100644
--- a/tests/features/builtin_trusted/runtest.sh
+++ b/tests/features/builtin_trusted/runtest.sh
@@ -24,7 +24,7 @@ id_key --to=blk %:.blacklist
 # There should be at least one built-in trusted key for module signing.
 list_keyring $btk
 expect_keyring_rlist bkeys
-if [ `echo $bkeys | wc -w` = 0 ]; then fail; fi
+if [ `echo $bkeys | wc -w` = 0 ]; then failed; fi
 
 # Check we can't add random keys to those keyrings
 marker "TRY ADDING USER KEYS"
-- 
2.40.1


^ permalink raw reply related	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 21/21] tpm: disable the TPM if NULL name changes
  2024-02-13 17:13 ` [PATCH v7 21/21] tpm: disable the TPM if NULL name changes James Bottomley
@ 2024-02-23 18:43   ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-02-23 18:43 UTC (permalink / raw)
  To: James Bottomley, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
> Update tpm2_load_context() to return -EINVAL on integrity failures and
> use this as a signal when loading the NULL context that something
> might be wrong.  If the signal fails, check the name of the NULL
> primary against the one stored in the chip data and if there is a
> mismatch disable the TPM because it is likely to have suffered a reset
> attack.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  drivers/char/tpm/tpm-chip.c      |  3 ++
>  drivers/char/tpm/tpm2-sessions.c | 65 ++++++++++++++++++++++++++------
>  drivers/char/tpm/tpm2-space.c    |  3 ++
>  include/linux/tpm.h              |  4 +-
>  4 files changed, 62 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index d93937326b2e..854546000c92 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -158,6 +158,9 @@ int tpm_try_get_ops(struct tpm_chip *chip)
>  {
>  	int rc = -EIO;
>  

Inline comment here as a reminder of the purpose of the check:

> +	if (chip->flags & TPM_CHIP_FLAG_DISABLE)
> +		return rc;
> +
>  	get_device(&chip->dev);
>  
>  	down_read(&chip->ops_sem);
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 9d6da0c9652f..60a1a8746563 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -87,6 +87,9 @@
>  #define AES_KEYBITS	(AES_KEYBYTES*8)
>  #define AUTH_MAX_NAMES	3
>  
> +static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
> +			       u32 *handle, u8 *name);

Should be ordered in the way that this declaration is not required.

> +
>  /*
>   * This is the structure that carries all the auth information (like
>   * session handle, nonces, session key and auth) from use to use it is
> @@ -847,6 +850,37 @@ static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
>  	return 0;
>  }
>  
> +static int tpm2_load_null(struct tpm_chip *chip, u32 *nullkey)
> +{
> +	int rc;
> +	unsigned int offset = 0; /* dummy offset for null seed context */
> +	u8 name[SHA256_DIGEST_SIZE + 2];
> +
> +	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
> +			       nullkey);
> +	if (rc != -EINVAL)
> +		return rc;
> +
> +	/* an integrity failure may mean the TPM has been reset */
> +	dev_err(&chip->dev, "NULL key integrity failure!\n");
> +	/* check the null name against what we know */
> +	tpm2_create_primary(chip, TPM2_RH_NULL, NULL, name);
> +	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0)
> +		/* name unchanged, assume transient integrity failure */
> +		return rc;
> +	/*
> +	 * Fatal TPM failure: the NULL seed has actually changed, so
> +	 * the TPM must have been illegally reset.  All in-kernel TPM
> +	 * operations will fail because the NULL primary can't be
> +	 * loaded to salt the sessions, but disable the TPM anyway so
> +	 * userspace programms can't be compromised by it.
> +	 */
> +	dev_err(&chip->dev, "NULL name has changed, disabling TPM due to interference\n");
> +	chip->flags |= TPM_CHIP_FLAG_DISABLE;
> +
> +	return rc;
> +}
> +
>  /**
>   * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
>   * @chip: the TPM chip structure to create the session with
> @@ -864,11 +898,9 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>  	struct tpm_buf buf;
>  	struct tpm2_auth *auth = chip->auth;
>  	int rc;
> -	unsigned int offset = 0; /* dummy offset for null seed context */
>  	u32 nullkey;
>  
> -	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
> -			       &nullkey);
> +	rc = tpm2_load_null(chip, &nullkey);
>  	if (rc)
>  		goto out;
>  
> @@ -919,15 +951,19 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>  EXPORT_SYMBOL(tpm2_start_auth_session);
>  
>  static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
> -				     u32 *nullkey)
> +				     u32 *handle, u8 *name)

Right sorry for my earlier comment this obviously cannot
tpm2_create_primary :-)

So tpm2_read_primary is probably in the ballpark given
that other more primitive functions are also "read".

>  {
>  	struct tpm_header *head = (struct tpm_header *)buf->data;
>  	off_t offset_r = TPM_HEADER_SIZE, offset_t;
>  	u16 len = TPM_HEADER_SIZE;
>  	u32 tot_len = be32_to_cpu(head->length);
> -	u32 val, parm_len;
> +	u32 val, parm_len, keyhandle;
> +	keyhandle = tpm_buf_read_u32(buf, &offset_r);
> +	if (handle)
> +		*handle = keyhandle;
> +	else
> +		tpm2_flush_context(chip, keyhandle);
>  
> -	*nullkey = tpm_buf_read_u32(buf, &offset_r);
>  	parm_len = tpm_buf_read_u32(buf, &offset_r);
>  	/*
>  	 * parm_len doesn't include the header, but all the other
> @@ -940,9 +976,12 @@ static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
>  		return -EINVAL;
>  	len = tpm_buf_read_u16(buf, &offset_r);
>  	offset_t = offset_r;
> -	/* now we have the public area, compute the name of the object */
> -	put_unaligned_be16(TPM_ALG_SHA256, chip->null_key_name);
> -	sha256(&buf->data[offset_r], len, chip->null_key_name + 2);
> +	if (name) {
> +		/* now we have the public area, compute the name of
> +		 * the object */
> +		put_unaligned_be16(TPM_ALG_SHA256, name);
> +		sha256(&buf->data[offset_r], len, name + 2);
> +	}
>  
>  	/* validate the public key */
>  	val = tpm_buf_read_u16(buf, &offset_t);
> @@ -1054,7 +1093,8 @@ static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
>  	return 0;
>  }
>  
> -static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle)
> +static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
> +			       u32 *handle, u8 *name)
>  {
>  	int rc;
>  	struct tpm_buf buf;
> @@ -1133,7 +1173,7 @@ static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle
>  			      "attempting to create NULL primary");
>  
>  	if (rc == TPM2_RC_SUCCESS)
> -		rc = tpm2_parse_create_primary(chip, &buf, handle);
> +		rc = tpm2_parse_create_primary(chip, &buf, handle, name);
>  
>  	tpm_buf_destroy(&buf);
>  
> @@ -1145,7 +1185,8 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
>  	u32 nullkey;
>  	int rc;
>  
> -	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey);
> +	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey,
> +				 chip->null_key_name);
>  
>  	if (rc == TPM2_RC_SUCCESS) {
>  		unsigned int offset = 0; /* dummy offset for null key context */
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index 24479a81c23c..4892d491da8d 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -105,6 +105,9 @@ int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
>  		*handle = 0;
>  		tpm_buf_destroy(&tbuf);
>  		return -ENOENT;
> +	} else if (tpm2_rc_value(rc) == TPM2_RC_INTEGRITY) {
> +		tpm_buf_destroy(&tbuf);
> +		return -EINVAL;
>  	} else if (rc > 0) {
>  		dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
>  			 __func__, rc);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 9c608fac8935..4474dabfb69d 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -244,6 +244,7 @@ enum tpm2_return_codes {
>  	TPM2_RC_SUCCESS		= 0x0000,
>  	TPM2_RC_HASH		= 0x0083, /* RC_FMT1 */
>  	TPM2_RC_HANDLE		= 0x008B,
> +	TPM2_RC_INTEGRITY	= 0x009F,
>  	TPM2_RC_INITIALIZE	= 0x0100, /* RC_VER1 */
>  	TPM2_RC_FAILURE		= 0x0101,
>  	TPM2_RC_DISABLED	= 0x0120,
> @@ -342,6 +343,7 @@ enum tpm_chip_flags {
>  	TPM_CHIP_FLAG_FIRMWARE_UPGRADE		= BIT(7),
>  	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
>  	TPM_CHIP_FLAG_HWRNG_DISABLED		= BIT(9),
> +	TPM_CHIP_FLAG_DISABLE			= BIT(10),
>  };
>  
>  #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
> @@ -428,7 +430,7 @@ static inline bool tpm_is_firmware_upgrade(struct tpm_chip *chip)
>  
>  static inline u32 tpm2_rc_value(u32 rc)
>  {
> -	return (rc & BIT(7)) ? rc & 0xff : rc;
> +	return (rc & BIT(7)) ? rc & 0xbf : rc;

What is this change?

>  }
>  
>  #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-02-13 17:13 ` [PATCH v7 12/21] tpm: Add NULL primary creation James Bottomley
  2024-02-23 15:51   ` Jarkko Sakkinen
@ 2024-03-30 18:48   ` Gabríel Arthúr Pétursson
  2024-03-31 16:00     ` Jarkko Sakkinen
  2024-04-01 14:19     ` James Bottomley
  1 sibling, 2 replies; 48+ messages in thread
From: Gabríel Arthúr Pétursson @ 2024-03-30 18:48 UTC (permalink / raw)
  To: James Bottomley, linux-integrity
  Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

On Tue, 2024-02-13 at 12:13 -0500, James Bottomley wrote:
> +	/* unique: key specific; for ECC it is two points */
> +	tpm_buf_append_u16(&template, 0);
> +	tpm_buf_append_u16(&template, 0);

Shouldn't the points be 32 bytes each in size, filled with zeros?

The TCP TPM 2.0 Provisioning Guidance defines the SRK Template as a
diff on top of Template L-2 (for ECC keys) as defined in the EK
Credential Profile 2.0 document.

Template L-2 calls for the X and Y points to be of 32 bytes each,
filled with zeros. The Provisioning Guidance does not call for zero-
sized points.

For example, let's create an ECC Endorsement Key using the standard
template then print its name:

   tpm2_createek -G ecc -c /dev/null -u ./ek.pub
   tpm2_loadexternal -c n -u ./ek.pub

Equivalently using tpm2_createprimary:

   perl -e 'print "\0"x64' | tpm2_createprimary -C e -o ./ek.pub -G ecc -a 'fixedtpm|fixedparent|sensitivedataorigin|adminwithpolicy|restricted|decrypt' -L 837197674484b3f81a90cc8d46a5d724fd52d76e06520b64f2a1da1b331469aa -u -
   tpm2_loadexternal -c n -u ./ek.pub

You'll find that the key's public modulus matches that of the EK
Certificate imprinted by the manufacturer, indicating we got the
template correct.

To generate a standard SRK key, the TCG TPM2 Provisioning Guidance
states we should:

	1. set userWithAuth,
	2. clear adminWithPolicy
	3. set noDA, and
	4. clear the authorization policy.

There's no mention of alterations to the unique field.

Let's also create the key in the null hierarchy:

   perl -e 'print "\0"x64' | tpm2_createprimary -C n -o ./null.pub -G ecc -a 'fixedtpm|fixedparent|sensitivedataorigin|userwithauth|noda|restricted|decrypt' -u -
   tpm2_loadexternal -c n -u ./null.pub

The name does not match the kernel's name for the null key.

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-03-30 18:48   ` Gabríel Arthúr Pétursson
@ 2024-03-31 16:00     ` Jarkko Sakkinen
  2024-03-31 16:09       ` Jarkko Sakkinen
  2024-03-31 16:52       ` Gabríel Arthúr Pétursson
  2024-04-01 14:19     ` James Bottomley
  1 sibling, 2 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-03-31 16:00 UTC (permalink / raw)
  To: Gabríel Arthúr Pétursson, James Bottomley,
	linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Sat Mar 30, 2024 at 8:48 PM EET, Gabríel Arthúr Pétursson wrote:
> On Tue, 2024-02-13 at 12:13 -0500, James Bottomley wrote:
> > +	/* unique: key specific; for ECC it is two points */
> > +	tpm_buf_append_u16(&template, 0);
> > +	tpm_buf_append_u16(&template, 0);
>
> Shouldn't the points be 32 bytes each in size, filled with zeros?
>
> The TCP TPM 2.0 Provisioning Guidance defines the SRK Template as a
> diff on top of Template L-2 (for ECC keys) as defined in the EK
> Credential Profile 2.0 document.
>
> Template L-2 calls for the X and Y points to be of 32 bytes each,
> filled with zeros. The Provisioning Guidance does not call for zero-
> sized points.
>
> For example, let's create an ECC Endorsement Key using the standard
> template then print its name:
>
>    tpm2_createek -G ecc -c /dev/null -u ./ek.pub
>    tpm2_loadexternal -c n -u ./ek.pub
>
> Equivalently using tpm2_createprimary:
>
>    perl -e 'print "\0"x64' | tpm2_createprimary -C e -o ./ek.pub -G ecc -a 'fixedtpm|fixedparent|sensitivedataorigin|adminwithpolicy|restricted|decrypt' -L 837197674484b3f81a90cc8d46a5d724fd52d76e06520b64f2a1da1b331469aa -u -
>    tpm2_loadexternal -c n -u ./ek.pub
>
> You'll find that the key's public modulus matches that of the EK
> Certificate imprinted by the manufacturer, indicating we got the
> template correct.
>
> To generate a standard SRK key, the TCG TPM2 Provisioning Guidance
> states we should:
>
> 	1. set userWithAuth,
> 	2. clear adminWithPolicy
> 	3. set noDA, and
> 	4. clear the authorization policy.
>
> There's no mention of alterations to the unique field.
>
> Let's also create the key in the null hierarchy:
>
>    perl -e 'print "\0"x64' | tpm2_createprimary -C n -o ./null.pub -G ecc -a 'fixedtpm|fixedparent|sensitivedataorigin|userwithauth|noda|restricted|decrypt' -u -
>    tpm2_loadexternal -c n -u ./null.pub
>
> The name does not match the kernel's name for the null key.

Null key is not provisioned, what is the motivation here?

Not saying no, just asking for details...

There's couple of things that lack in this patch set ATM:

1. Neither kselftest additions nor not even proper testing
   instructions. Why 21 patches and zero tests? How one should
   decide when the work is "complete"?
2. I still don't know what version of QEMU I should patch to
   test corner cases from an URL, which I cannot recall :-)
   Highlights the first issue.

So for the time being the patch set is NAK just because we lack
clear definition of done here. I revisit it only when I know how
to test it.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-03-31 16:00     ` Jarkko Sakkinen
@ 2024-03-31 16:09       ` Jarkko Sakkinen
  2024-03-31 16:52       ` Gabríel Arthúr Pétursson
  1 sibling, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-03-31 16:09 UTC (permalink / raw)
  To: Jarkko Sakkinen, Gabríel Arthúr Pétursson,
	James Bottomley, linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Sun Mar 31, 2024 at 7:00 PM EEST, Jarkko Sakkinen wrote:
> On Sat Mar 30, 2024 at 8:48 PM EET, Gabríel Arthúr Pétursson wrote:
> > On Tue, 2024-02-13 at 12:13 -0500, James Bottomley wrote:
> > > +	/* unique: key specific; for ECC it is two points */
> > > +	tpm_buf_append_u16(&template, 0);
> > > +	tpm_buf_append_u16(&template, 0);
> >
> > Shouldn't the points be 32 bytes each in size, filled with zeros?
> >
> > The TCP TPM 2.0 Provisioning Guidance defines the SRK Template as a
> > diff on top of Template L-2 (for ECC keys) as defined in the EK
> > Credential Profile 2.0 document.
> >
> > Template L-2 calls for the X and Y points to be of 32 bytes each,
> > filled with zeros. The Provisioning Guidance does not call for zero-
> > sized points.
> >
> > For example, let's create an ECC Endorsement Key using the standard
> > template then print its name:
> >
> >    tpm2_createek -G ecc -c /dev/null -u ./ek.pub
> >    tpm2_loadexternal -c n -u ./ek.pub
> >
> > Equivalently using tpm2_createprimary:
> >
> >    perl -e 'print "\0"x64' | tpm2_createprimary -C e -o ./ek.pub -G ecc -a 'fixedtpm|fixedparent|sensitivedataorigin|adminwithpolicy|restricted|decrypt' -L 837197674484b3f81a90cc8d46a5d724fd52d76e06520b64f2a1da1b331469aa -u -
> >    tpm2_loadexternal -c n -u ./ek.pub
> >
> > You'll find that the key's public modulus matches that of the EK
> > Certificate imprinted by the manufacturer, indicating we got the
> > template correct.
> >
> > To generate a standard SRK key, the TCG TPM2 Provisioning Guidance
> > states we should:
> >
> > 	1. set userWithAuth,
> > 	2. clear adminWithPolicy
> > 	3. set noDA, and
> > 	4. clear the authorization policy.
> >
> > There's no mention of alterations to the unique field.
> >
> > Let's also create the key in the null hierarchy:
> >
> >    perl -e 'print "\0"x64' | tpm2_createprimary -C n -o ./null.pub -G ecc -a 'fixedtpm|fixedparent|sensitivedataorigin|userwithauth|noda|restricted|decrypt' -u -
> >    tpm2_loadexternal -c n -u ./null.pub
> >
> > The name does not match the kernel's name for the null key.
>
> Null key is not provisioned, what is the motivation here?
>
> Not saying no, just asking for details...
>
> There's couple of things that lack in this patch set ATM:
>
> 1. Neither kselftest additions nor not even proper testing
>    instructions. Why 21 patches and zero tests? How one should
>    decide when the work is "complete"?
> 2. I still don't know what version of QEMU I should patch to
>    test corner cases from an URL, which I cannot recall :-)
>    Highlights the first issue.
>
> So for the time being the patch set is NAK just because we lack
> clear definition of done here. I revisit it only when I know how
> to test it.

Your feedback was great because it highlights the issue that the
excepted behaviour is non-existent at this point.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-03-31 16:00     ` Jarkko Sakkinen
  2024-03-31 16:09       ` Jarkko Sakkinen
@ 2024-03-31 16:52       ` Gabríel Arthúr Pétursson
  2024-04-01 12:57         ` Jarkko Sakkinen
  2024-04-02 19:30         ` Ken Goldman
  1 sibling, 2 replies; 48+ messages in thread
From: Gabríel Arthúr Pétursson @ 2024-03-31 16:52 UTC (permalink / raw)
  To: Jarkko Sakkinen, James Bottomley, linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Sun, 2024-03-31 at 19:00 +0300, Jarkko Sakkinen wrote:
> Null key is not provisioned, what is the motivation here?

The terms here, to create a key and to provision a key, are almost
interchangeable. The latter merely implies the additional step of
saving the key to NVRAM and making it available through a persistent
handle.

The template, aside from defining what kind of key we want to create,
is fed into the TPM's KDF used to generate the key. Different template,
different key.

Userspace will want to recreate the same key the kernel has, thus must
use the same template. Which template shall be used then?

+	/*
+	 * create the template.  Note: in order for userspace to
+	 * verify the security of the system, it will have to create
+	 * and certify this NULL primary, meaning all the template
+	 * parameters will have to be identical, so conform exactly to
+	 * the TCG TPM v2.0 Provisioning Guidance for the SRK ECC
+	 * key
+	 */

The TPM specifications have a standardized set of templates for the
Endorsement Keys, and a recommendation on a template to
create/provision the shared SRK.

Why not use that one then, above something else? We are required to use
a template for key generation after all, might as well pick the one
most fitting from the standards.

That's at least my understanding of the author's motivation.

> So for the time being the patch set is NAK just because we lack
> clear definition of done here. I revisit it only when I know how
> to test it.

I want to note that I'm not affiliated with the patches' author. I'm
merely an outside observer who has taken interest in the proposed
changes. Wanted to share my thoughts.

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-03-31 16:52       ` Gabríel Arthúr Pétursson
@ 2024-04-01 12:57         ` Jarkko Sakkinen
  2024-04-01 13:04           ` Jarkko Sakkinen
  2024-04-02 19:30         ` Ken Goldman
  1 sibling, 1 reply; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-04-01 12:57 UTC (permalink / raw)
  To: Gabríel Arthúr Pétursson, James Bottomley,
	linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Sun Mar 31, 2024 at 7:52 PM EEST, Gabríel Arthúr Pétursson wrote:
> On Sun, 2024-03-31 at 19:00 +0300, Jarkko Sakkinen wrote:
> > Null key is not provisioned, what is the motivation here?
>
> The terms here, to create a key and to provision a key, are almost
> interchangeable. The latter merely implies the additional step of
> saving the key to NVRAM and making it available through a persistent
> handle.
>
> The template, aside from defining what kind of key we want to create,
> is fed into the TPM's KDF used to generate the key. Different template,
> different key.
>
> Userspace will want to recreate the same key the kernel has, thus must
> use the same template. Which template shall be used then?

I don't disagree with you, nor did when sending the first response :-)

Downstream seems to break that guide tho. E.g. Ubuntu uses 0x80100001
NV index for storage key unsealing the key slot with PCR values. I did
some time ago a quick VM install of Ubuntu just to see how it uses TPM2.

I got:

$ sudo tpm2_getcap handles-persistent
- 0x81000001
- 0x81010001

0x81010001 is according to provisioning guide EK handle but Ubuntu uses
it for completely different purpose.

What I would like to understand when it comes to the provisioning guide
is how important it is in reality? I have no information at this point
is e.g. systemd-boot going to follow it but would like to know.


>
> +	/*
> +	 * create the template.  Note: in order for userspace to
> +	 * verify the security of the system, it will have to create
> +	 * and certify this NULL primary, meaning all the template
> +	 * parameters will have to be identical, so conform exactly to
> +	 * the TCG TPM v2.0 Provisioning Guidance for the SRK ECC
> +	 * key
> +	 */
>
> The TPM specifications have a standardized set of templates for the
> Endorsement Keys, and a recommendation on a template to
> create/provision the shared SRK.
>
> Why not use that one then, above something else? We are required to use
> a template for key generation after all, might as well pick the one
> most fitting from the standards.
>
> That's at least my understanding of the author's motivation.

Yeah, not necessarily disagree with this or I'm somewhat aligned to this
view. Ubuntu's architecture confuses me so would like to understand the
magnitude of the provisioning guide.

>
> > So for the time being the patch set is NAK just because we lack
> > clear definition of done here. I revisit it only when I know how
> > to test it.
>
> I want to note that I'm not affiliated with the patches' author. I'm
> merely an outside observer who has taken interest in the proposed
> changes. Wanted to share my thoughts.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-04-01 12:57         ` Jarkko Sakkinen
@ 2024-04-01 13:04           ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-04-01 13:04 UTC (permalink / raw)
  To: Jarkko Sakkinen, Gabríel Arthúr Pétursson,
	James Bottomley, linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Mon Apr 1, 2024 at 3:57 PM EEST, Jarkko Sakkinen wrote:
> > > So for the time being the patch set is NAK just because we lack
> > > clear definition of done here. I revisit it only when I know how
> > > to test it.
> >
> > I want to note that I'm not affiliated with the patches' author. I'm
> > merely an outside observer who has taken interest in the proposed
> > changes. Wanted to share my thoughts.

I.e. thanks a lot for the feedback. It makes sense to I'm just confused
overally of the provisioning topic as one big player (Canonical) in the
cloud seems to break that guide, unless I missed something.

It would interesting to get some feedback on this from Ubuntu developers
but I don't know who has worked on TPM2 boot feature on that side.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-03-30 18:48   ` Gabríel Arthúr Pétursson
  2024-03-31 16:00     ` Jarkko Sakkinen
@ 2024-04-01 14:19     ` James Bottomley
  2024-04-01 16:55       ` James Bottomley
  1 sibling, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-04-01 14:19 UTC (permalink / raw)
  To: Gabríel Arthúr Pétursson, linux-integrity
  Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

On Sat, 2024-03-30 at 18:48 +0000, Gabríel Arthúr Pétursson wrote:
> On Tue, 2024-02-13 at 12:13 -0500, James Bottomley wrote:
> > +       /* unique: key specific; for ECC it is two points */
> > +       tpm_buf_append_u16(&template, 0);
> > +       tpm_buf_append_u16(&template, 0);
> 
> Shouldn't the points be 32 bytes each in size, filled with zeros?
> 
> The TCP TPM 2.0 Provisioning Guidance defines the SRK Template as a
> diff on top of Template L-2 (for ECC keys) as defined in the EK
> Credential Profile 2.0 document.
> 
> Template L-2 calls for the X and Y points to be of 32 bytes each,
> filled with zeros. The Provisioning Guidance does not call for zero-
> sized points.
> 
> For example, let's create an ECC Endorsement Key using the standard
> template then print its name:
> 
>    tpm2_createek -G ecc -c /dev/null -u ./ek.pub
>    tpm2_loadexternal -c n -u ./ek.pub
> 
> Equivalently using tpm2_createprimary:
> 
>    perl -e 'print "\0"x64' | tpm2_createprimary -C e -o ./ek.pub -G
> ecc -a
> 'fixedtpm|fixedparent|sensitivedataorigin|adminwithpolicy|restricted|
> decrypt' -L
> 837197674484b3f81a90cc8d46a5d724fd52d76e06520b64f2a1da1b331469aa -u -
>    tpm2_loadexternal -c n -u ./ek.pub
> 
> You'll find that the key's public modulus matches that of the EK
> Certificate imprinted by the manufacturer, indicating we got the
> template correct.
> 
> To generate a standard SRK key, the TCG TPM2 Provisioning Guidance
> states we should:
> 
>         1. set userWithAuth,
>         2. clear adminWithPolicy
>         3. set noDA, and
>         4. clear the authorization policy.
> 
> There's no mention of alterations to the unique field.
> 
> Let's also create the key in the null hierarchy:
> 
>    perl -e 'print "\0"x64' | tpm2_createprimary -C n -o ./null.pub -G
> ecc -a
> 'fixedtpm|fixedparent|sensitivedataorigin|userwithauth|noda|restricte
> d|decrypt' -u -
>    tpm2_loadexternal -c n -u ./null.pub
> 
> The name does not match the kernel's name for the null key.

So this seems to be a fairly global problem.  If you look at
openssl_tpm2_engine, openconnect and gnutls, they all formulate the ECC
primary template this way (zero size points).  They all look to have
inherited it from the IBM TSS:

https://github.com/kgoldman/ibmtss/blob/master/utils/objecttemplates.c#L272-L275

Ironically, even the Intel TSS based openssl engine and the provider
seem to define it this way as well, and they definitely didn't get it
from the IBM TSS:

https://github.com/tpm2-software/tpm2-tss-engine/blob/master/src/tpm2-tss-engine-common.h#L149-L152

The problem is if we change it now, it would break all the current keys
with primary handles (which is pretty much all of them thanks to almost
no-one following the provisioning guidance about persistent handles).

So I'm not really sure how to solve this.  At the moment the kernel
doesn't use permanent handles for keys, but it should and it should
follow what all of the industry is doing for interoperability (i.e.
zero size points), which means the NULL primary should also follow it.

James


^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-04-01 14:19     ` James Bottomley
@ 2024-04-01 16:55       ` James Bottomley
  2024-04-01 20:54         ` Jarkko Sakkinen
  0 siblings, 1 reply; 48+ messages in thread
From: James Bottomley @ 2024-04-01 16:55 UTC (permalink / raw)
  To: Gabríel Arthúr Pétursson, linux-integrity
  Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

On Mon, 2024-04-01 at 10:19 -0400, James Bottomley wrote:
> So I'm not really sure how to solve this.  At the moment the kernel
> doesn't use permanent handles for keys, but it should and it should
> follow what all of the industry is doing for interoperability (i.e.
> zero size points), which means the NULL primary should also follow
> it.

Actually, it turns out this is already solved by the TCG.  The template
we're using is the correct one (zero size points).  Apparently they
regretted their earlier decision to zero fill and issued this guidance:

   2.2.1.2.2 EK Template
   
   An EK Template is stored in an NV Index as a TPMT_PUBLIC structure
   marshaled as described in the TPM 2.0 Library Specification [1]. The
   default EK Templates are defined in annex B. The EK Template NV Index
   MUST be Populated if non-default values are used. It SHOULD be Absent
   if default values are used.
   
   The EK Template unique field buffer size(s) SHOULD be zero.
   
But since they can't revoke the previous guidance, we now have two
templates defined: the L one which has the old n bytes of zeros and the
new (and recommended) H one which has zero size unique field.

https://trustedcomputinggroup.org/resource/http-trustedcomputinggroup-org-wp-content-uploads-tcg-ek-credential-profile-v-2-5-r2_published-pdf/

So in other words, we're doing the later correct thing and there's no
problem.  I'll update the ASN.1 draft

https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html

to state that we MUST use the H template to remove any ambiguity

James


^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-04-01 16:55       ` James Bottomley
@ 2024-04-01 20:54         ` Jarkko Sakkinen
  2024-04-01 20:59           ` Jarkko Sakkinen
  0 siblings, 1 reply; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-04-01 20:54 UTC (permalink / raw)
  To: James Bottomley, Gabríel Arthúr Pétursson,
	linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Mon Apr 1, 2024 at 7:55 PM EEST, James Bottomley wrote:
> On Mon, 2024-04-01 at 10:19 -0400, James Bottomley wrote:
> > So I'm not really sure how to solve this.  At the moment the kernel
> > doesn't use permanent handles for keys, but it should and it should
> > follow what all of the industry is doing for interoperability (i.e.
> > zero size points), which means the NULL primary should also follow
> > it.
>
> Actually, it turns out this is already solved by the TCG.  The template
> we're using is the correct one (zero size points).  Apparently they
> regretted their earlier decision to zero fill and issued this guidance:
>
>    2.2.1.2.2 EK Template
>    
>    An EK Template is stored in an NV Index as a TPMT_PUBLIC structure
>    marshaled as described in the TPM 2.0 Library Specification [1]. The
>    default EK Templates are defined in annex B. The EK Template NV Index
>    MUST be Populated if non-default values are used. It SHOULD be Absent
>    if default values are used.
>    
>    The EK Template unique field buffer size(s) SHOULD be zero.
>    
> But since they can't revoke the previous guidance, we now have two
> templates defined: the L one which has the old n bytes of zeros and the
> new (and recommended) H one which has zero size unique field.
>
> https://trustedcomputinggroup.org/resource/http-trustedcomputinggroup-org-wp-content-uploads-tcg-ek-credential-profile-v-2-5-r2_published-pdf/
>
> So in other words, we're doing the later correct thing and there's no
> problem.  I'll update the ASN.1 draft
>
> https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html

First time I'm seeing this document or URL.

>
> to state that we MUST use the H template to remove any ambiguity
>
> James

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-04-01 20:54         ` Jarkko Sakkinen
@ 2024-04-01 20:59           ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-04-01 20:59 UTC (permalink / raw)
  To: Jarkko Sakkinen, James Bottomley,
	Gabríel Arthúr Pétursson, linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Mon Apr 1, 2024 at 11:54 PM EEST, Jarkko Sakkinen wrote:
> On Mon Apr 1, 2024 at 7:55 PM EEST, James Bottomley wrote:
> > On Mon, 2024-04-01 at 10:19 -0400, James Bottomley wrote:
> > > So I'm not really sure how to solve this.  At the moment the kernel
> > > doesn't use permanent handles for keys, but it should and it should
> > > follow what all of the industry is doing for interoperability (i.e.
> > > zero size points), which means the NULL primary should also follow
> > > it.
> >
> > Actually, it turns out this is already solved by the TCG.  The template
> > we're using is the correct one (zero size points).  Apparently they
> > regretted their earlier decision to zero fill and issued this guidance:
> >
> >    2.2.1.2.2 EK Template
> >    
> >    An EK Template is stored in an NV Index as a TPMT_PUBLIC structure
> >    marshaled as described in the TPM 2.0 Library Specification [1]. The
> >    default EK Templates are defined in annex B. The EK Template NV Index
> >    MUST be Populated if non-default values are used. It SHOULD be Absent
> >    if default values are used.
> >    
> >    The EK Template unique field buffer size(s) SHOULD be zero.
> >    
> > But since they can't revoke the previous guidance, we now have two
> > templates defined: the L one which has the old n bytes of zeros and the
> > new (and recommended) H one which has zero size unique field.
> >
> > https://trustedcomputinggroup.org/resource/http-trustedcomputinggroup-org-wp-content-uploads-tcg-ek-credential-profile-v-2-5-r2_published-pdf/
> >
> > So in other words, we're doing the later correct thing and there's no
> > problem.  I'll update the ASN.1 draft
> >
> > https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html
>
> First time I'm seeing this document or URL.

Anyway, only thing that we align with is the latest in kernel
documentation, outside URL's are ignored. I.e. the legit ref
is trusted-encrypted.rst.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-03-31 16:52       ` Gabríel Arthúr Pétursson
  2024-04-01 12:57         ` Jarkko Sakkinen
@ 2024-04-02 19:30         ` Ken Goldman
  2024-04-03 15:43           ` Jarkko Sakkinen
  1 sibling, 1 reply; 48+ messages in thread
From: Ken Goldman @ 2024-04-02 19:30 UTC (permalink / raw)
  To: Gabríel Arthúr Pétursson, Jarkko Sakkinen,
	James Bottomley, linux-integrity
  Cc: keyrings, Ard Biesheuvel

On 3/31/2024 12:52 PM, Gabríel Arthúr Pétursson wrote:
> The TPM specifications have a standardized set of templates for the
> Endorsement Keys, and a recommendation on a template to
> create/provision the shared SRK.

The original TCG guidance document for an SRK used arrays of zeros for 
the unique field.

This was either a holdover from TPM 1.2, where arrays were 20 bytes,
or a misinterpretation of text that said: NULL.

The reality is that it's a TPM2B, and the size(s) can be zero.

The answer for the EK is different. It has to use the TCG
standard.  The EK is not a 'guidance document'.

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-04-02 19:30         ` Ken Goldman
@ 2024-04-03 15:43           ` Jarkko Sakkinen
  0 siblings, 0 replies; 48+ messages in thread
From: Jarkko Sakkinen @ 2024-04-03 15:43 UTC (permalink / raw)
  To: Ken Goldman, Gabríel Arthúr Pétursson,
	James Bottomley, linux-integrity
  Cc: keyrings, Ard Biesheuvel

On Tue Apr 2, 2024 at 10:30 PM EEST, Ken Goldman wrote:
> On 3/31/2024 12:52 PM, Gabríel Arthúr Pétursson wrote:
> > The TPM specifications have a standardized set of templates for the
> > Endorsement Keys, and a recommendation on a template to
> > create/provision the shared SRK.
>
> The original TCG guidance document for an SRK used arrays of zeros for 
> the unique field.
>
> This was either a holdover from TPM 1.2, where arrays were 20 bytes,
> or a misinterpretation of text that said: NULL.
>
> The reality is that it's a TPM2B, and the size(s) can be zero.
>
> The answer for the EK is different. It has to use the TCG
> standard.  The EK is not a 'guidance document'.

Does anyone follow TCG's provisioning guide? I.e. is it implemented
"in the industry"? I'm just trying to understand the real value of
this document.

BR, Jarkko

^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 12/21] tpm: Add NULL primary creation
  2024-02-23 15:51   ` Jarkko Sakkinen
@ 2024-04-29 20:10     ` James Bottomley
  0 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-04-29 20:10 UTC (permalink / raw)
  To: Jarkko Sakkinen, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Fri, 2024-02-23 at 17:51 +0200, Jarkko Sakkinen wrote:
> On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
[...]
> > --- a/drivers/char/tpm/tpm.h
> > +++ b/drivers/char/tpm/tpm.h
> > @@ -321,4 +321,14 @@ void tpm_bios_log_setup(struct tpm_chip
> > *chip);
> >  void tpm_bios_log_teardown(struct tpm_chip *chip);
> >  int tpm_dev_common_init(void);
> >  void tpm_dev_common_exit(void);
> > +
> > +#ifdef CONFIG_TCG_TPM2_HMAC
> > +int tpm2_sessions_init(struct tpm_chip *chip);
> 
> I'm sorry but "sessions" and "init" are the worst possible
> terminology I could every pick when trying to make a function that
> self-documents itself :-)

About 95% of the kernel that run initialization routines are suffixed
_init. The TCG documents that describe how to effect HMAC and
encryption of commands call the entities used to do this "sessions".
You can argue they should have chosen a better name, but given it's the
name they chose, we have to use it to avoid confusion.

> I'd like to see here well-scoped name so that it is easy to connect
> this to its purpose when reviewing some other patches.

It's purpose is to initialize the sessions handling code in the tpm2-
sessions.c file; I'm not sure I could come up with anything as concise
for self description.


James


^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 13/21] tpm: Add HMAC session start and end functions
  2024-02-23 17:02   ` Jarkko Sakkinen
@ 2024-04-29 20:11     ` James Bottomley
  0 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-04-29 20:11 UTC (permalink / raw)
  To: Jarkko Sakkinen, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Fri, 2024-02-23 at 19:02 +0200, Jarkko Sakkinen wrote:
> On Tue Feb 13, 2024 at 7:13 PM EET, James Bottomley wrote:
[...]
> >  static int tpm2_parse_create_primary(struct tpm_chip *chip, struct
> > tpm_buf *buf,
> >                                      u32 *nullkey)
>                 
> 
> What if this was simply tpm2_create_primary?

It would cause a massive code block surrounded by an if, which would
make the function somewhat less readable.

James


^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 14/21] tpm: Add HMAC session name/handle append
  2024-02-23 17:06   ` Jarkko Sakkinen
@ 2024-04-29 20:11     ` James Bottomley
  0 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-04-29 20:11 UTC (permalink / raw)
  To: Jarkko Sakkinen, linux-integrity; +Cc: keyrings, Ard Biesheuvel

On Fri, 2024-02-23 at 19:06 +0200, Jarkko Sakkinen wrote:
> > +static inline enum tpm2_mso_type tpm2_handle_mso(u32 handle)
> > +{
> > +       return handle >> 24;
> 
> did we have macro for this (cannot recall)? like oppposite
> of BIT().

No, that's why I added this. inline functions are easier to type check
than macros.

James


^ permalink raw reply	[flat|nested] 48+ messages in thread

* Re: [PATCH v7 15/21] tpm: Add the rest of the session HMAC API
  2024-02-23 17:10   ` Jarkko Sakkinen
@ 2024-04-29 20:11     ` James Bottomley
  0 siblings, 0 replies; 48+ messages in thread
From: James Bottomley @ 2024-04-29 20:11 UTC (permalink / raw)
  To: jarkko; +Cc: James.Bottomley, ardb, keyrings, linux-integrity

> OK, since there is multiple patches with KDF* dep the KDF functions
> should be their own separate patch not glued into any patch that uses
> them.

Well, I can do that if you insist, but it can't go into the kernel like
that because we'll then have a static function with no consumers which
will generate an unused function warning and break the build on -
Werror.

James



^ permalink raw reply	[flat|nested] 48+ messages in thread

end of thread, other threads:[~2024-04-29 20:11 UTC | newest]

Thread overview: 48+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-02-13 17:13 [PATCH v7 00/21] add integrity and security to TPM2 transactions James Bottomley
2024-02-13 17:13 ` [PATCH v7 01/21] tpm: Remove unused tpm_buf_tag() James Bottomley
2024-02-13 17:13 ` [PATCH v7 02/21] tpm: Remove tpm_send() James Bottomley
2024-02-13 17:13 ` [PATCH v7 03/21] tpm: Move buffer handling from static inlines to real functions James Bottomley
2024-02-13 17:13 ` [PATCH v7 04/21] tpm: Update struct tpm_buf documentation comments James Bottomley
2024-02-13 17:13 ` [PATCH v7 05/21] tpm: Store the length of the tpm_buf data separately James Bottomley
2024-02-13 17:13 ` [PATCH v7 06/21] tpm: TPM2B formatted buffers James Bottomley
2024-02-13 17:13 ` [PATCH v7 07/21] tpm: Add tpm_buf_read_{u8,u16,u32} James Bottomley
2024-02-13 17:13 ` [PATCH v7 08/21] KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers James Bottomley
2024-02-13 17:13 ` [PATCH v7 09/21] crypto: lib - implement library version of AES in CFB mode James Bottomley
2024-02-13 17:13 ` [PATCH v7 10/21] tpm: add buffer function to point to returned parameters James Bottomley
2024-02-13 17:13 ` [PATCH v7 11/21] tpm: export the context save and load commands James Bottomley
2024-02-13 17:13 ` [PATCH v7 12/21] tpm: Add NULL primary creation James Bottomley
2024-02-23 15:51   ` Jarkko Sakkinen
2024-04-29 20:10     ` James Bottomley
2024-03-30 18:48   ` Gabríel Arthúr Pétursson
2024-03-31 16:00     ` Jarkko Sakkinen
2024-03-31 16:09       ` Jarkko Sakkinen
2024-03-31 16:52       ` Gabríel Arthúr Pétursson
2024-04-01 12:57         ` Jarkko Sakkinen
2024-04-01 13:04           ` Jarkko Sakkinen
2024-04-02 19:30         ` Ken Goldman
2024-04-03 15:43           ` Jarkko Sakkinen
2024-04-01 14:19     ` James Bottomley
2024-04-01 16:55       ` James Bottomley
2024-04-01 20:54         ` Jarkko Sakkinen
2024-04-01 20:59           ` Jarkko Sakkinen
2024-02-13 17:13 ` [PATCH v7 13/21] tpm: Add HMAC session start and end functions James Bottomley
2024-02-23 17:02   ` Jarkko Sakkinen
2024-04-29 20:11     ` James Bottomley
2024-02-13 17:13 ` [PATCH v7 14/21] tpm: Add HMAC session name/handle append James Bottomley
2024-02-23 17:06   ` Jarkko Sakkinen
2024-04-29 20:11     ` James Bottomley
2024-02-13 17:13 ` [PATCH v7 15/21] tpm: Add the rest of the session HMAC API James Bottomley
2024-02-23 17:10   ` Jarkko Sakkinen
2024-04-29 20:11     ` James Bottomley
2024-02-13 17:13 ` [PATCH v7 16/21] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
2024-02-23 17:10   ` Jarkko Sakkinen
2024-02-13 17:13 ` [PATCH v7 17/21] tpm: add session encryption protection to tpm2_get_random() James Bottomley
2024-02-23 17:10   ` Jarkko Sakkinen
2024-02-13 17:13 ` [PATCH v7 18/21] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
2024-02-23 17:11   ` Jarkko Sakkinen
2024-02-13 17:13 ` [PATCH v7 19/21] tpm: add the null key name as a sysfs export James Bottomley
2024-02-23 17:15   ` Jarkko Sakkinen
2024-02-13 17:13 ` [PATCH v7 20/21] Documentation: add tpm-security.rst James Bottomley
2024-02-13 17:13 ` [PATCH v7 21/21] tpm: disable the TPM if NULL name changes James Bottomley
2024-02-23 18:43   ` Jarkko Sakkinen
2024-02-14  0:13 ` [PATCH v7 00/21] add integrity and security to TPM2 transactions Jarkko Sakkinen

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