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* [PATCH 00/12] add integrity and security to TPM2 transactions
@ 2023-02-16 20:13 James Bottomley
  2023-02-16 20:13 ` [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode James Bottomley
                   ` (12 more replies)
  0 siblings, 13 replies; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:13 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.

James

---

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

James Bottomley (11):
  tpm: move buffer handling from static inlines to real functions
  tpm: add buffer handling for TPM2B types
  tpm: add cursor based buffer functions for response parsing
  tpm: add buffer function to point to returned parameters
  tpm: export the context save and load commands
  tpm: Add full HMAC and encrypt/decrypt session handling code
  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

 Documentation/security/tpm/tpm-security.rst |  216 ++++
 drivers/char/tpm/Kconfig                    |   13 +
 drivers/char/tpm/Makefile                   |    2 +
 drivers/char/tpm/tpm-buf.c                  |  196 ++++
 drivers/char/tpm/tpm-chip.c                 |    3 +
 drivers/char/tpm/tpm-sysfs.c                |   18 +
 drivers/char/tpm/tpm.h                      |   14 +
 drivers/char/tpm/tpm2-cmd.c                 |   52 +-
 drivers/char/tpm/tpm2-sessions.c            | 1160 +++++++++++++++++++
 drivers/char/tpm/tpm2-space.c               |    8 +-
 include/crypto/aes.h                        |    5 +
 include/linux/tpm.h                         |  257 ++--
 lib/crypto/Kconfig                          |    5 +
 lib/crypto/Makefile                         |    3 +
 lib/crypto/aescfb.c                         |   75 ++
 security/keys/trusted-keys/trusted_tpm2.c   |   82 +-
 16 files changed, 1984 insertions(+), 125 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] 28+ messages in thread

* [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
@ 2023-02-16 20:13 ` James Bottomley
  2023-02-27  7:47   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 02/12] tpm: move buffer handling from static inlines to real functions James Bottomley
                   ` (11 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:13 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.

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  | 75 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 88 insertions(+)
 create mode 100644 lib/crypto/aescfb.c

diff --git a/include/crypto/aes.h b/include/crypto/aes.h
index 2090729701ab..7b9e1df1ccb0 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);
+void aescfb_decrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 *iv);
+
 #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 6ec2d4543d9c..33213a01aab1 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..e9de1c6d874a
--- /dev/null
+++ b/lib/crypto/aescfb.c
@@ -0,0 +1,75 @@
+// 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);
+}
+
+void aescfb_encrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 *iv)
+{
+	while (len > 0) {
+		u8 ks[AES_BLOCK_SIZE];
+
+		aescfb_encrypt_block(ctx, ks, iv);
+		crypto_xor_cpy(dst, src, ks, min(len, AES_BLOCK_SIZE));
+		iv = dst;
+
+		dst += AES_BLOCK_SIZE;
+		src += AES_BLOCK_SIZE;
+		len -= AES_BLOCK_SIZE;
+	}
+}
+
+void aescfb_decrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
+		    int len, const u8 *iv)
+{
+	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;
+	}
+}
+
+MODULE_DESCRIPTION("Generic AES-CFB library");
+MODULE_AUTHOR("Ard Biesheuvel <ardb@kernel.org>");
+MODULE_LICENSE("GPL");
-- 
2.35.3


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

* [PATCH 02/12] tpm: move buffer handling from static inlines to real functions
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
  2023-02-16 20:13 ` [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-27  8:18   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 03/12] tpm: add buffer handling for TPM2B types James Bottomley
                   ` (10 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 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>

---
v3: make tpm_buf_tag static
---
 drivers/char/tpm/Makefile  |  1 +
 drivers/char/tpm/tpm-buf.c | 95 ++++++++++++++++++++++++++++++++++++++
 include/linux/tpm.h        | 86 ++++------------------------------
 3 files changed, 105 insertions(+), 77 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..ca59b92e0f95
--- /dev/null
+++ b/drivers/char/tpm/tpm-buf.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Handing for tpm_buf structures to facilitate the building of commands
+ */
+
+#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);
+
+static u16 tpm_buf_tag(struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	return be16_to_cpu(head->tag);
+}
+
+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 dfeb25a0362d..150b39b6190e 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -322,84 +322,16 @@ 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 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)
-{
-	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] 28+ messages in thread

* [PATCH 03/12] tpm: add buffer handling for TPM2B types
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
  2023-02-16 20:13 ` [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode James Bottomley
  2023-02-16 20:14 ` [PATCH 02/12] tpm: move buffer handling from static inlines to real functions James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-27  8:31   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 04/12] tpm: add cursor based buffer functions for response parsing James Bottomley
                   ` (9 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Most complex TPM commands require appending TPM2B buffers to the
command body.  Since TPM2B types are essentially variable size arrays,
it makes it impossible to represent these complex command arguments as
structures and we simply have to build them up using append primitives
like these.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c | 71 +++++++++++++++++++++++++++++++++++---
 include/linux/tpm.h        |  3 ++
 2 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index ca59b92e0f95..292c6f14f72c 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -7,17 +7,16 @@
 #include <linux/module.h>
 #include <linux/tpm.h>
 
-int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+static int __tpm_buf_init(struct tpm_buf *buf)
 {
 	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)
 {
@@ -29,17 +28,60 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 }
 EXPORT_SYMBOL_GPL(tpm_buf_reset);
 
+int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	int rc;
+
+	rc = __tpm_buf_init(buf);
+	if (rc)
+		return rc;
+
+	tpm_buf_reset(buf, tag, ordinal);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init);
+
+int tpm_buf_init_2b(struct tpm_buf *buf)
+{
+	struct tpm_header *head;
+	int rc;
+
+	rc = __tpm_buf_init(buf);
+	if (rc)
+		return rc;
+
+	head = (struct tpm_header *) buf->data;
+
+	head->length = cpu_to_be32(sizeof(*head));
+
+	buf->flags = TPM_BUF_2B;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init_2b);
+
 void tpm_buf_destroy(struct tpm_buf *buf)
 {
 	free_page((unsigned long)buf->data);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_destroy);
 
+static void *tpm_buf_data(struct tpm_buf *buf)
+{
+	if (buf->flags & TPM_BUF_2B)
+		return buf->data + TPM_HEADER_SIZE;
+	return buf->data;
+}
+
 u32 tpm_buf_length(struct tpm_buf *buf)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
+	u32 len;
 
-	return be32_to_cpu(head->length);
+	len = be32_to_cpu(head->length);
+	if (buf->flags & TPM_BUF_2B)
+		len -= sizeof(*head);
+	return len;
 }
 EXPORT_SYMBOL_GPL(tpm_buf_length);
 
@@ -55,7 +97,7 @@ void tpm_buf_append(struct tpm_buf *buf,
 		    unsigned int new_len)
 {
 	struct tpm_header *head = (struct tpm_header *) buf->data;
-	u32 len = tpm_buf_length(buf);
+	u32 len = be32_to_cpu(head->length);
 
 	/* Return silently if overflow has already happened. */
 	if (buf->flags & TPM_BUF_OVERFLOW)
@@ -93,3 +135,22 @@ 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);
+
+static void tpm_buf_reset_int(struct tpm_buf *buf)
+{
+	struct tpm_header *head;
+
+	head = (struct tpm_header *)buf->data;
+	head->length = cpu_to_be32(sizeof(*head));
+}
+
+void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
+{
+	u16 len = tpm_buf_length(tpm2b);
+
+	tpm_buf_append_u16(buf, len);
+	tpm_buf_append(buf, tpm_buf_data(tpm2b), len);
+	/* clear the buf for reuse */
+	tpm_buf_reset_int(tpm2b);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 150b39b6190e..f2d4dab6d832 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -300,6 +300,7 @@ struct tpm_header {
 
 enum tpm_buf_flags {
 	TPM_BUF_OVERFLOW	= BIT(0),
+	TPM_BUF_2B		= BIT(1),
 };
 
 struct tpm_buf {
@@ -324,6 +325,7 @@ struct tpm2_hash {
 
 
 int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
+int tpm_buf_init_2b(struct tpm_buf *buf);
 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);
@@ -332,6 +334,7 @@ void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
 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);
+void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.
-- 
2.35.3


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

* [PATCH 04/12] tpm: add cursor based buffer functions for response parsing
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (2 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 03/12] tpm: add buffer handling for TPM2B types James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-27  8:34   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 05/12] tpm: add buffer function to point to returned parameters James Bottomley
                   ` (8 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Once we have encryption and authentication, marshalling and
unmarshalling sessions becomes hugely complex.  Add cursor based
functions which update the current pointer to make response parsing
easier.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c | 29 +++++++++++++++++++++++++++++
 include/linux/tpm.h        |  3 +++
 2 files changed, 32 insertions(+)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 292c6f14f72c..b76158f9bcd0 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -7,6 +7,8 @@
 #include <linux/module.h>
 #include <linux/tpm.h>
 
+#include <asm/unaligned.h>
+
 static int __tpm_buf_init(struct tpm_buf *buf)
 {
 	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
@@ -154,3 +156,30 @@ void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
 	tpm_buf_reset_int(tpm2b);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
+
+/* functions for unmarshalling data and moving the cursor */
+u8 tpm_get_inc_u8(const u8 **ptr)
+{
+	return *((*ptr)++);
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u8);
+
+u16 tpm_get_inc_u16(const u8 **ptr)
+{
+	u16 val;
+
+	val = get_unaligned_be16(*ptr);
+	*ptr += sizeof(val);
+	return val;
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u16);
+
+u32 tpm_get_inc_u32(const u8 **ptr)
+{
+	u32 val;
+
+	val = get_unaligned_be32(*ptr);
+	*ptr += sizeof(val);
+	return val;
+}
+EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index f2d4dab6d832..f7cff1d114b0 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -335,6 +335,9 @@ 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);
 void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b);
+u8 tpm_get_inc_u8(const u8 **ptr);
+u16 tpm_get_inc_u16(const u8 **ptr);
+u32 tpm_get_inc_u32(const u8 **ptr);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.
-- 
2.35.3


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

* [PATCH 05/12] tpm: add buffer function to point to returned parameters
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (3 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 04/12] tpm: add cursor based buffer functions for response parsing James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-27  8:36   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 06/12] tpm: export the context save and load commands James Bottomley
                   ` (7 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Introducing encryption sessions changes where the return parameters
are located in the buffer because if a return session is present
they're 4 bytes beyond the header with those 4 bytes showing the
parameter length.  If there is no return session, then they're in the
usual place immediately after the header.  The tpm_buf_parameters()
encapsulates this calculation and should be used everywhere
&buf.data[TPM_HEADER_SIZE] is used now

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c | 10 ++++++++++
 include/linux/tpm.h        |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index b76158f9bcd0..2518b675e866 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -183,3 +183,13 @@ u32 tpm_get_inc_u32(const u8 **ptr)
 	return val;
 }
 EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
+
+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 f7cff1d114b0..fa8d1f932c0f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -339,6 +339,8 @@ u8 tpm_get_inc_u8(const u8 **ptr);
 u16 tpm_get_inc_u16(const u8 **ptr);
 u32 tpm_get_inc_u32(const u8 **ptr);
 
+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] 28+ messages in thread

* [PATCH 06/12] tpm: export the context save and load commands
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (4 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 05/12] tpm: add buffer function to point to returned parameters James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-27  8:37   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code James Bottomley
                   ` (6 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 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>
---
 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 24ee4e1cc452..a5fe37977103 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -237,6 +237,10 @@ 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 ffb35f0154c1..d77ee4af9d65 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] 28+ messages in thread

* [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (5 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 06/12] tpm: export the context save and load commands James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-16 23:37   ` kernel test robot
  2023-02-17 11:30   ` kernel test robot
  2023-02-16 20:14 ` [PATCH 08/12] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
                   ` (5 subsequent siblings)
  12 siblings, 2 replies; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

Add true 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.  Then the use is
simply:

* tpm_buf_append_name() in place of the tpm_buf_append_u32 for the
  handles

* tpm_buf_append_hmac_session() where tpm2_append_auth() would go

* tpm_buf_fill_hmac_session() called after the entire command buffer
  is finished but before tpm_transmit_cmd() is called which computes
  the correct HMAC and places it in the command at the correct
  location.

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 is 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.

To get all of this to work securely, the Kernel needs a primary key to
encrypt the session salt to, so an EC key from the NULL seed is
derived and its context saved in the tpm_chip structure.  The context
is loaded on demand into an available volatile handle when
tpm_start_auth_session() is called, but is flushed before that
function exits to conserve handles.

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

---

v2: fix memory leaks from smatch; adjust for name hash size
v3: make tpm2_make_null_primary static
v4: use crypto library functions
---
 drivers/char/tpm/Kconfig         |   13 +
 drivers/char/tpm/Makefile        |    1 +
 drivers/char/tpm/tpm-buf.c       |    1 +
 drivers/char/tpm/tpm-chip.c      |    3 +
 drivers/char/tpm/tpm.h           |   10 +
 drivers/char/tpm/tpm2-cmd.c      |    5 +
 drivers/char/tpm/tpm2-sessions.c | 1160 ++++++++++++++++++++++++++++++
 include/linux/tpm.h              |  165 +++++
 8 files changed, 1358 insertions(+)
 create mode 100644 drivers/char/tpm/tpm2-sessions.c

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 927088b2c3d3..8af3afc48511 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -27,6 +27,19 @@ menuconfig TCG_TPM
 
 if TCG_TPM
 
+config TPM_BUS_SECURITY
+	bool "Use secure 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 tamper resistent scheme
+	  for communicating with the TPM to prevent or detect bus
+	  snooping and iterposer attacks like TPM Genie.  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..10dc214aa093 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-$(CONFIG_TPM_BUS_SECURITY) += tpm2-sessions.o
 tpm-$(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-buf.c b/drivers/char/tpm/tpm-buf.c
index 2518b675e866..dbe4a8e8cef3 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -27,6 +27,7 @@ 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 741d8f3e8fb3..5577445cde53 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -271,6 +271,9 @@ 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_TPM_BUS_SECURITY
+	kfree(chip->auth);
+#endif
 	kfree(chip);
 }
 
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index a5fe37977103..b3eb0f31bfd9 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -246,4 +246,14 @@ 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_TPM_BUS_SECURITY
+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 65d03867e114..056dad3dd5c9 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..920845b9434d
--- /dev/null
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -0,0 +1,1160 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * 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.
+ *
+ * Then there are six 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.
+ * 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.
+ * 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"
+
+#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];
+	};
+	/*
+	 * 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];
+};
+
+/*
+ * 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
+ * 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->ec_point_x, EC_PT_SZ);
+	sg_set_buf(&s[1], chip->ec_point_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->ec_point_x, chip->auth->salt);
+ out:
+	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;
+	const u8 *s, *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);
+
+	s = &buf->data[TPM_HEADER_SIZE];
+	/*
+	 * 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_get_inc_u32(&s);
+
+		if (auth->name_h[i] != handle) {
+			dev_err(&chip->dev, "TPM: handle %d wrong for name\n",
+				  i);
+			return;
+		}
+	}
+	/* point s to the start of the sessions */
+	val = tpm_get_inc_u32(&s);
+	/* point p to the start of the parameters */
+	p = s + val;
+	for (i = 1; s < p; i++) {
+		u32 handle = tpm_get_inc_u32(&s);
+		u16 len;
+		u8 a;
+
+		/* nonce (already in auth) */
+		len = tpm_get_inc_u16(&s);
+		s += len;
+
+		a = *s++;
+
+		len = tpm_get_inc_u16(&s);
+		if (handle == auth->handle && auth->attrs == a) {
+			hmac = (u8 *)s;
+			/*
+			 * save our session number so we know which
+			 * session in the response belongs to us
+			 */
+			auth->session = i;
+		}
+
+		s += len;
+	}
+	if (s != 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_get_inc_u16(&p);
+		aes_expandkey(&auth->aes_ctx, auth->scratch, AES_KEYBYTES);
+		aescfb_encrypt(&auth->aes_ctx, (u8 *)p, p, len,
+			       auth->scratch + AES_KEYBYTES);
+		/* reset p to beginning of parameters for HMAC */
+		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++) {
+		u8 mso = auth->name_h[i] >> 24;
+
+		if (mso == 0x81 || mso == 0x80 || mso == 0x01) {
+			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 (buf->data - s != tpm_buf_length(buf))
+		sha256_update(&sctx, s, buf->data + tpm_buf_length(buf) - 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 parse_read_public(char *name, const u8 *data)
+{
+	struct tpm_header *head = (struct tpm_header *)data;
+	u32 tot_len = be32_to_cpu(head->length);
+	u32 val;
+
+	data += TPM_HEADER_SIZE;
+	/* we're starting after the header so adjust the length */
+	tot_len -= TPM_HEADER_SIZE;
+
+	/* skip public */
+	val = tpm_get_inc_u16(&data);
+	if (val > tot_len)
+		return -EINVAL;
+	data += val;
+	/* name */
+	val = tpm_get_inc_u16(&data);
+	if (val != name_size(data))
+		return -EINVAL;
+	memcpy(name, data, name_size(data));
+	/* 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 = parse_read_public(name, buf.data);
+
+	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;
+	u8 mso = handle >> 24;
+	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 == 0x81 || mso == 0x80 || mso == 0x01) {
+		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);
+
+/**
+ * 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;
+	const u8 *s, *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 */
+	s = &buf->data[TPM_HEADER_SIZE + handles * 4];
+	parm_len = tpm_get_inc_u32(&s);
+	p = s;
+	s += parm_len;
+	/* skip over any sessions before ours */
+	for (i = 0; i < auth->session - 1; i++) {
+		len = tpm_get_inc_u16(&s);
+		s += len + 1;
+		len = tpm_get_inc_u16(&s);
+		s += len;
+	}
+	/* TPM nonce */
+	len = tpm_get_inc_u16(&s);
+	if (s - buf->data + len > tpm_buf_length(buf))
+		goto out;
+	if (len != SHA256_DIGEST_SIZE)
+		goto out;
+	memcpy(auth->tpm_nonce, s, len);
+	s += len;
+	attrs = *s++;
+	len = tpm_get_inc_u16(&s);
+	if (s - buf->data + len != tpm_buf_length(buf))
+		goto out;
+	if (len != SHA256_DIGEST_SIZE)
+		goto out;
+	/*
+	 * 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, 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, 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_get_inc_u16(&p);
+		aes_expandkey(&auth->aes_ctx, auth->scratch, AES_KEYBYTES);
+		aescfb_decrypt(&auth->aes_ctx, (u8 *)p, p, len,
+			       auth->scratch + AES_KEYBYTES);
+	}
+
+ out:
+	if ((auth->attrs & TPM2_SA_CONTINUE_SESSION) == 0
+	    && rc)
+		/* manually close the session if it wasn't consumed */
+		tpm2_flush_context(chip, auth->handle);
+
+	/* 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
+ *
+ * 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_respons().
+ */
+void tpm2_end_auth_session(struct tpm_chip *chip)
+{
+	tpm2_flush_context(chip, chip->auth->handle);
+	chip->auth->session = TPM_HEADER_SIZE;
+}
+EXPORT_SYMBOL(tpm2_end_auth_session);
+
+static int parse_start_auth_session(struct tpm2_auth *auth, const u8 *data)
+{
+	struct tpm_header *head = (struct tpm_header *)data;
+	u32 tot_len = be32_to_cpu(head->length);
+	u32 val;
+
+	data += TPM_HEADER_SIZE;
+	/* 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_get_inc_u32(&data);
+	val = tpm_get_inc_u16(&data);
+	if (val != sizeof(auth->tpm_nonce))
+		return -EINVAL;
+	memcpy(auth->tpm_nonce, data, 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
+ * @authp: A pointer to an opaque tpm2_auth structure to be allocated
+ *
+ * This function loads the NULL seed from its saved context and starts
+ * an authentication session on the null seed, allocates a tpm2_auth
+ * structure to contain all the session details necessary for
+ * performing the HMAC, encrypt and decrypt operations, fills it in
+ * and returns.  The NULL seed is flushed before this function returns.
+ *
+ * Return: zero on success or actual error encountered.  If return is
+ * zero, @authp will be allocated.
+ */
+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->tpmkeycontext, &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 = parse_start_auth_session(auth, buf.data);
+
+	tpm_buf_destroy(&buf);
+
+	if (rc)
+		goto out;
+
+ out:
+	return rc;
+}
+EXPORT_SYMBOL(tpm2_start_auth_session);
+
+static int parse_create_primary(struct tpm_chip *chip, u8 *data, u32 *nullkey)
+{
+	struct tpm_header *head = (struct tpm_header *)data;
+	u16 len;
+	u32 tot_len = be32_to_cpu(head->length);
+	u32 val, parm_len;
+	const u8 *resp, *tmp;
+
+	data += TPM_HEADER_SIZE;
+	/* we're starting after the header so adjust the length */
+	tot_len -= TPM_HEADER_SIZE;
+
+	resp = data;
+	*nullkey = tpm_get_inc_u32(&resp);
+	parm_len = tpm_get_inc_u32(&resp);
+	if (parm_len + 8 > tot_len)
+		return -EINVAL;
+	len = tpm_get_inc_u16(&resp);
+	tmp = resp;
+	/* now we have the public area, compute the name of the object */
+	put_unaligned_be16(TPM_ALG_SHA256, chip->tpmkeyname);
+	sha256(resp, len, chip->tpmkeyname + 2);
+
+	/* validate the public key */
+	val = tpm_get_inc_u16(&tmp);
+	/* key type (must be what we asked for) */
+	if (val != TPM_ALG_ECC)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* name algorithm */
+	if (val != TPM_ALG_SHA256)
+		return -EINVAL;
+	val = tpm_get_inc_u32(&tmp);
+	/* 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_get_inc_u16(&tmp);
+	if (val != 0)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* symmetric key parameters */
+	if (val != TPM_ALG_AES)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* symmetric key length */
+	if (val != AES_KEYBITS)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* symmetric encryption scheme */
+	if (val != TPM_ALG_CFB)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* signing scheme */
+	if (val != TPM_ALG_NULL)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* ECC Curve */
+	if (val != TPM2_ECC_NIST_P256)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* KDF Scheme */
+	if (val != TPM_ALG_NULL)
+		return -EINVAL;
+	val = tpm_get_inc_u16(&tmp);
+	/* x point */
+	if (val != 32)
+		return -EINVAL;
+	memcpy(chip->ec_point_x, tmp, val);
+	tmp += val;
+	val = tpm_get_inc_u16(&tmp);
+	if (val != 32)
+		return -EINVAL;
+	memcpy(chip->ec_point_y, tmp, val);
+	tmp += val;
+	resp += len;
+	/* should have exactly consumed the tpm2b public structure */
+	if (tmp != resp)
+		return -EINVAL;
+	if (resp - data > parm_len)
+		return -EINVAL;
+	/* creation data (skip) */
+	len = tpm_get_inc_u16(&resp);
+	resp += len;
+	if (resp - data > parm_len)
+		return -EINVAL;
+	/* creation digest (must be sha256) */
+	len = tpm_get_inc_u16(&resp);
+	resp += len;
+	if (len != SHA256_DIGEST_SIZE || resp - data > parm_len)
+		return -EINVAL;
+	/* TPMT_TK_CREATION follows */
+	/* tag, must be TPM_ST_CREATION (0x8021) */
+	val = tpm_get_inc_u16(&resp);
+	if (val != TPM2_ST_CREATION || resp - data > parm_len)
+		return -EINVAL;
+	/* hierarchy (must be NULL) */
+	val = tpm_get_inc_u32(&resp);
+	if (val != TPM2_RH_NULL || resp - data > parm_len)
+		return -EINVAL;
+	/* the ticket digest HMAC (might not be sha256) */
+	len = tpm_get_inc_u16(&resp);
+	resp += len;
+	if (resp - data > parm_len)
+		return -EINVAL;
+	/*
+	 * finally we have the name, which is a sha256 digest plus a 2
+	 * byte algorithm type
+	 */
+	len = tpm_get_inc_u16(&resp);
+	if (resp + len - data != parm_len + 8)
+		return -EINVAL;
+	if (len != SHA256_DIGEST_SIZE + 2)
+		return -EINVAL;
+
+	if (memcmp(chip->tpmkeyname, resp, 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_2b(&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_2b(&buf, &template);
+	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 = parse_create_primary(chip, buf.data, 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 tpmkeycontext */
+
+		rc = tpm2_save_context(chip, nullkey, chip->tpmkeycontext,
+				       sizeof(chip->tpmkeycontext), &offset);
+		tpm2_flush_context(chip, nullkey);
+	}
+
+	return rc;
+}
+
+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);
+
+	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 fa8d1f932c0f..e9ee276528de 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -30,17 +30,28 @@
 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 {
 	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 +60,11 @@ 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 +132,20 @@ 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 +200,15 @@ struct tpm_chip {
 
 	/* active locality */
 	int locality;
+
+#ifdef CONFIG_TPM_BUS_SECURITY
+	/* details for communication security via sessions */
+	u8 tpmkeycontext[TPM2_MAX_CONTEXT_SIZE]; /* context for NULL seed */
+	u8 tpmkeyname[TPM2_NAME_SIZE];		 /* name of NULL seed */
+	u8 ec_point_x[EC_PT_SZ];
+	u8 ec_point_y[EC_PT_SZ];
+	struct tpm2_auth *auth;
+#endif
 };
 
 #define TPM_HEADER_SIZE		10
@@ -194,6 +233,7 @@ 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 */
@@ -231,6 +271,10 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_POLICY_AUTHVALUE	= 0x016B,
+	TPM2_CC_POLICY_COUNTER_TIMER	= 0x016D,
+	TPM2_CC_READ_PUBLIC		= 0x0173,
+	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
 	TPM2_CC_GET_CAPABILITY	        = 0x017A,
 	TPM2_CC_GET_RANDOM	        = 0x017B,
@@ -243,6 +287,7 @@ enum tpm2_command_codes {
 };
 
 enum tpm2_permanent_handles {
+	TPM2_RH_NULL		= 0x40000007,
 	TPM2_RS_PW		= 0x40000009,
 };
 
@@ -306,16 +351,30 @@ enum tpm_buf_flags {
 struct tpm_buf {
 	unsigned int flags;
 	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 {
@@ -369,6 +428,15 @@ 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);
+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 +467,102 @@ 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
+#ifdef CONFIG_TPM_BUS_SECURITY
+
+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;
+}
+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++;
+}
+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_TPM_BUS_SECURITY */
+
 #endif
-- 
2.35.3


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

* [PATCH 08/12] tpm: add hmac checks to tpm2_pcr_extend()
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (6 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-27  9:16   ` Jarkko Sakkinen
  2023-02-16 20:14 ` [PATCH 09/12] tpm: add session encryption protection to tpm2_get_random() James Bottomley
                   ` (4 subsequent siblings)
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 UTC (permalink / raw)
  To: linux-integrity; +Cc: Jarkko Sakkinen, keyrings, Ard Biesheuvel

We use tpm2_pcr_extend() in 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.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 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 056dad3dd5c9..ef038cc71f9c 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] 28+ messages in thread

* [PATCH 09/12] tpm: add session encryption protection to tpm2_get_random()
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (7 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 08/12] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-16 20:14 ` [PATCH 10/12] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
                   ` (3 subsequent siblings)
  12 siblings, 0 replies; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 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>
---
 drivers/char/tpm/tpm2-cmd.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index ef038cc71f9c..dc0070922d38 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 +
@@ -327,6 +337,8 @@ 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);
-- 
2.35.3


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

* [PATCH 10/12] KEYS: trusted: Add session encryption protection to the seal/unseal path
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (8 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 09/12] tpm: add session encryption protection to tpm2_get_random() James Bottomley
@ 2023-02-16 20:14 ` James Bottomley
  2023-02-16 20:40 ` [PATCH 11/12] tpm: add the null key name as a sysfs export James Bottomley
                   ` (2 subsequent siblings)
  12 siblings, 0 replies; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:14 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>

---

v2: fix unseal with policy and password
v3: fix session memory leak
---
 security/keys/trusted-keys/trusted_tpm2.c | 82 ++++++++++++++++-------
 1 file changed, 58 insertions(+), 24 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 2b2c8eb258d5..4790aa7a1e0f 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -252,18 +252,19 @@ 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;
 	}
 
-	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(&buf, 4 + options->blobauth_len + payload->key_len);
@@ -305,10 +306,13 @@ 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;
 
@@ -340,6 +344,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	else
 		payload->blob_len = blob_len;
 
+out_put:
 	tpm_put_ops(chip);
 	return rc;
 }
@@ -409,25 +414,31 @@ 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]);
@@ -465,20 +476,43 @@ 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, TPM_DIGEST_SIZE);
+	} 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] 28+ messages in thread

* [PATCH 11/12] tpm: add the null key name as a sysfs export
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (9 preceding siblings ...)
  2023-02-16 20:14 ` [PATCH 10/12] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
@ 2023-02-16 20:40 ` James Bottomley
  2023-02-17 10:59   ` kernel test robot
  2023-02-16 20:41 ` [PATCH 12/12] Documentation: add tpm-security.rst James Bottomley
  2023-02-17 22:43 ` [PATCH 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
  12 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:40 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>
---
 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..6044a2765da2 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_TPM_BUS_SECURITY
+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->tpmkeyname, 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,
+#if CONFIG_TPM_BUS_SECURITY
+	&dev_attr_null_name.attr,
+#endif
 	NULL
 };
 
-- 
2.35.3



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

* [PATCH 12/12] Documentation: add tpm-security.rst
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (10 preceding siblings ...)
  2023-02-16 20:40 ` [PATCH 11/12] tpm: add the null key name as a sysfs export James Bottomley
@ 2023-02-16 20:41 ` James Bottomley
  2023-02-17 22:43 ` [PATCH 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
  12 siblings, 0 replies; 28+ messages in thread
From: James Bottomley @ 2023-02-16 20:41 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>
---
 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] 28+ messages in thread

* Re: [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
  2023-02-16 20:14 ` [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code James Bottomley
@ 2023-02-16 23:37   ` kernel test robot
  2023-02-17 11:30   ` kernel test robot
  1 sibling, 0 replies; 28+ messages in thread
From: kernel test robot @ 2023-02-16 23:37 UTC (permalink / raw)
  To: James Bottomley, linux-integrity
  Cc: oe-kbuild-all, Jarkko Sakkinen, keyrings, Ard Biesheuvel

Hi James,

I love your patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus herbert-cryptodev-2.6/master herbert-crypto-2.6/master linus/master v6.2-rc8 next-20230216]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/James-Bottomley/crypto-lib-implement-library-version-of-AES-in-CFB-mode/20230217-044329
patch link:    https://lore.kernel.org/r/20230216201410.15010-8-James.Bottomley%40HansenPartnership.com
patch subject: [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
config: m68k-randconfig-c44-20230212 (https://download.01.org/0day-ci/archive/20230217/202302170740.7jtAnH0N-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/1d4f519aa756ba5ed684fb2a2f9ad6e1fb91bdb5
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review James-Bottomley/crypto-lib-implement-library-version-of-AES-in-CFB-mode/20230217-044329
        git checkout 1d4f519aa756ba5ed684fb2a2f9ad6e1fb91bdb5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash drivers/char/tpm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302170740.7jtAnH0N-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/char/tpm/tpm2-sessions.c:337: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * tpm_buf_append_hmac_session() append a TPM session element
   drivers/char/tpm/tpm2-sessions.c:855: warning: Excess function parameter 'authp' description in 'tpm2_start_auth_session'


vim +337 drivers/char/tpm/tpm2-sessions.c

   335	
   336	/**
 > 337	 * tpm_buf_append_hmac_session() append a TPM session element
   338	 * @chip: the TPM chip structure
   339	 * @buf: The buffer to be appended
   340	 * @attributes: The session attributes
   341	 * @passphrase: The session authority (NULL if none)
   342	 * @passphraselen: The length of the session authority (0 if none)
   343	 *
   344	 * This fills in a session structure in the TPM command buffer, except
   345	 * for the HMAC which cannot be computed until the command buffer is
   346	 * complete.  The type of session is controlled by the @attributes,
   347	 * the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
   348	 * session won't terminate after tpm_buf_check_hmac_response(),
   349	 * TPM2_SA_DECRYPT which means this buffers first parameter should be
   350	 * encrypted with a session key and TPM2_SA_ENCRYPT, which means the
   351	 * response buffer's first parameter needs to be decrypted (confusing,
   352	 * but the defines are written from the point of view of the TPM).
   353	 *
   354	 * Any session appended by this command must be finalized by calling
   355	 * tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
   356	 * and the TPM will reject the command.
   357	 *
   358	 * As with most tpm_buf operations, success is assumed because failure
   359	 * will be caused by an incorrect programming model and indicated by a
   360	 * kernel message.
   361	 */
   362	void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
   363					 u8 attributes, u8 *passphrase,
   364					 int passphraselen)
   365	{
   366		u8 nonce[SHA256_DIGEST_SIZE];
   367		u32 len;
   368		struct tpm2_auth *auth = chip->auth;
   369	
   370		/*
   371		 * The Architecture Guide requires us to strip trailing zeros
   372		 * before computing the HMAC
   373		 */
   374		while (passphrase && passphraselen > 0
   375		       && passphrase[passphraselen - 1] == '\0')
   376			passphraselen--;
   377	
   378		auth->attrs = attributes;
   379		auth->passphraselen = passphraselen;
   380		if (passphraselen)
   381			memcpy(auth->passphrase, passphrase, passphraselen);
   382	
   383		if (auth->session != tpm_buf_length(buf)) {
   384			/* we're not the first session */
   385			len = get_unaligned_be32(&buf->data[auth->session]);
   386			if (4 + len + auth->session != tpm_buf_length(buf)) {
   387				WARN(1, "session length mismatch, cannot append");
   388				return;
   389			}
   390	
   391			/* add our new session */
   392			len += 9 + 2 * SHA256_DIGEST_SIZE;
   393			put_unaligned_be32(len, &buf->data[auth->session]);
   394		} else {
   395			tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
   396		}
   397	
   398		/* random number for our nonce */
   399		get_random_bytes(nonce, sizeof(nonce));
   400		memcpy(auth->our_nonce, nonce, sizeof(nonce));
   401		tpm_buf_append_u32(buf, auth->handle);
   402		/* our new nonce */
   403		tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
   404		tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
   405		tpm_buf_append_u8(buf, auth->attrs);
   406		/* and put a placeholder for the hmac */
   407		tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
   408		tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
   409	}
   410	EXPORT_SYMBOL(tpm_buf_append_hmac_session);
   411	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

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

* Re: [PATCH 11/12] tpm: add the null key name as a sysfs export
  2023-02-16 20:40 ` [PATCH 11/12] tpm: add the null key name as a sysfs export James Bottomley
@ 2023-02-17 10:59   ` kernel test robot
  0 siblings, 0 replies; 28+ messages in thread
From: kernel test robot @ 2023-02-17 10:59 UTC (permalink / raw)
  To: James Bottomley, linux-integrity
  Cc: oe-kbuild-all, Jarkko Sakkinen, keyrings, Ard Biesheuvel

Hi James,

I love your patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus herbert-cryptodev-2.6/master linus/master v6.2-rc8 next-20230217]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/James-Bottomley/crypto-lib-implement-library-version-of-AES-in-CFB-mode/20230217-044329
patch link:    https://lore.kernel.org/r/93740b6b42e67caa2a1854520b7e68f0966e5024.camel%40HansenPartnership.com
patch subject: [PATCH 11/12] tpm: add the null key name as a sysfs export
config: nios2-randconfig-m041-20230217 (https://download.01.org/0day-ci/archive/20230217/202302171852.zpg5jNaj-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/4c35ecc57dfd3fd82341cd20dfc30c5f665ba952
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review James-Bottomley/crypto-lib-implement-library-version-of-AES-in-CFB-mode/20230217-044329
        git checkout 4c35ecc57dfd3fd82341cd20dfc30c5f665ba952
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=nios2 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=nios2 SHELL=/bin/bash drivers/char/tpm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302171852.zpg5jNaj-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/char/tpm/tpm-sysfs.c:344:5: warning: "CONFIG_TPM_BUS_SECURITY" is not defined, evaluates to 0 [-Wundef]
     344 | #if CONFIG_TPM_BUS_SECURITY
         |     ^~~~~~~~~~~~~~~~~~~~~~~


vim +/CONFIG_TPM_BUS_SECURITY +344 drivers/char/tpm/tpm-sysfs.c

   341	
   342	static struct attribute *tpm2_dev_attrs[] = {
   343		&dev_attr_tpm_version_major.attr,
 > 344	#if CONFIG_TPM_BUS_SECURITY
   345		&dev_attr_null_name.attr,
   346	#endif
   347		NULL
   348	};
   349	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

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

* Re: [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
  2023-02-16 20:14 ` [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code James Bottomley
  2023-02-16 23:37   ` kernel test robot
@ 2023-02-17 11:30   ` kernel test robot
  2023-02-17 14:22     ` James Bottomley
  1 sibling, 1 reply; 28+ messages in thread
From: kernel test robot @ 2023-02-17 11:30 UTC (permalink / raw)
  To: James Bottomley, linux-integrity
  Cc: oe-kbuild-all, Jarkko Sakkinen, keyrings, Ard Biesheuvel

Hi James,

I love your patch! Yet something to improve:

[auto build test ERROR on char-misc/char-misc-testing]
[also build test ERROR on char-misc/char-misc-next char-misc/char-misc-linus herbert-cryptodev-2.6/master herbert-crypto-2.6/master linus/master v6.2-rc8 next-20230217]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/James-Bottomley/crypto-lib-implement-library-version-of-AES-in-CFB-mode/20230217-044329
patch link:    https://lore.kernel.org/r/20230216201410.15010-8-James.Bottomley%40HansenPartnership.com
patch subject: [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
config: parisc64-defconfig (https://download.01.org/0day-ci/archive/20230217/202302171905.Ornmq8g3-lkp@intel.com/config)
compiler: hppa64-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/1d4f519aa756ba5ed684fb2a2f9ad6e1fb91bdb5
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review James-Bottomley/crypto-lib-implement-library-version-of-AES-in-CFB-mode/20230217-044329
        git checkout 1d4f519aa756ba5ed684fb2a2f9ad6e1fb91bdb5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=parisc64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=parisc64 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302171905.Ornmq8g3-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "aescfb_encrypt" [drivers/char/tpm/tpm.ko] undefined!
>> ERROR: modpost: "aescfb_decrypt" [drivers/char/tpm/tpm.ko] undefined!

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

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

* Re: [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
  2023-02-17 11:30   ` kernel test robot
@ 2023-02-17 14:22     ` James Bottomley
  2023-02-17 14:23       ` Ard Biesheuvel
  0 siblings, 1 reply; 28+ messages in thread
From: James Bottomley @ 2023-02-17 14:22 UTC (permalink / raw)
  To: kernel test robot, linux-integrity
  Cc: oe-kbuild-all, Jarkko Sakkinen, keyrings, Ard Biesheuvel

On Fri, 2023-02-17 at 19:30 +0800, kernel test robot wrote:
[...]
> > > ERROR: modpost: "aescfb_encrypt" [drivers/char/tpm/tpm.ko]
> > > undefined!
> > > ERROR: modpost: "aescfb_decrypt" [drivers/char/tpm/tpm.ko]
> > > undefined!

Ard,

This happens because your aescfb_encrypt/decrypt() routines are missing
EXPORT_SYMBOL statements.

Regards,

James



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

* Re: [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code
  2023-02-17 14:22     ` James Bottomley
@ 2023-02-17 14:23       ` Ard Biesheuvel
  0 siblings, 0 replies; 28+ messages in thread
From: Ard Biesheuvel @ 2023-02-17 14:23 UTC (permalink / raw)
  To: James Bottomley
  Cc: kernel test robot, linux-integrity, oe-kbuild-all,
	Jarkko Sakkinen, keyrings

On Fri, 17 Feb 2023 at 15:22, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
>
> On Fri, 2023-02-17 at 19:30 +0800, kernel test robot wrote:
> [...]
> > > > ERROR: modpost: "aescfb_encrypt" [drivers/char/tpm/tpm.ko]
> > > > undefined!
> > > > ERROR: modpost: "aescfb_decrypt" [drivers/char/tpm/tpm.ko]
> > > > undefined!
>
> Ard,
>
> This happens because your aescfb_encrypt/decrypt() routines are missing
> EXPORT_SYMBOL statements.
>

OK, i'll add those.

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

* Re: [PATCH 00/12] add integrity and security to TPM2 transactions
  2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (11 preceding siblings ...)
  2023-02-16 20:41 ` [PATCH 12/12] Documentation: add tpm-security.rst James Bottomley
@ 2023-02-17 22:43 ` Jarkko Sakkinen
  12 siblings, 0 replies; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-17 22:43 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:13:58PM -0500, 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.
> 
> James
> 
> ---
> 
> Ard Biesheuvel (1):
>   crypto: lib - implement library version of AES in CFB mode
> 
> James Bottomley (11):
>   tpm: move buffer handling from static inlines to real functions
>   tpm: add buffer handling for TPM2B types
>   tpm: add cursor based buffer functions for response parsing
>   tpm: add buffer function to point to returned parameters
>   tpm: export the context save and load commands
>   tpm: Add full HMAC and encrypt/decrypt session handling code
>   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
> 
>  Documentation/security/tpm/tpm-security.rst |  216 ++++
>  drivers/char/tpm/Kconfig                    |   13 +
>  drivers/char/tpm/Makefile                   |    2 +
>  drivers/char/tpm/tpm-buf.c                  |  196 ++++
>  drivers/char/tpm/tpm-chip.c                 |    3 +
>  drivers/char/tpm/tpm-sysfs.c                |   18 +
>  drivers/char/tpm/tpm.h                      |   14 +
>  drivers/char/tpm/tpm2-cmd.c                 |   52 +-
>  drivers/char/tpm/tpm2-sessions.c            | 1160 +++++++++++++++++++
>  drivers/char/tpm/tpm2-space.c               |    8 +-
>  include/crypto/aes.h                        |    5 +
>  include/linux/tpm.h                         |  257 ++--
>  lib/crypto/Kconfig                          |    5 +
>  lib/crypto/Makefile                         |    3 +
>  lib/crypto/aescfb.c                         |   75 ++
>  security/keys/trusted-keys/trusted_tpm2.c   |   82 +-
>  16 files changed, 1984 insertions(+), 125 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
> 

Overally looks much better than earlier version! I'll aim to 
test this next week [*].

[*] The startup I was in went out of business, meaning that I'm
ATM independent contributor doing this on my free time until I
find a new job. That said, I spend 4 hours a day with kernel every
working day so should not affect much as far reviewing and
testing goes.

BR, Jarkko

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

* Re: [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode
  2023-02-16 20:13 ` [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode James Bottomley
@ 2023-02-27  7:47   ` Jarkko Sakkinen
  0 siblings, 0 replies; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  7:47 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:13:59PM -0500, James Bottomley wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> Implement AES in CFB mode using the existing, mostly constant-time
> generic AES library implementation.
> 
> 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  | 75 ++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 88 insertions(+)
>  create mode 100644 lib/crypto/aescfb.c
> 
> diff --git a/include/crypto/aes.h b/include/crypto/aes.h
> index 2090729701ab..7b9e1df1ccb0 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);
> +void aescfb_decrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
> +		    int len, const u8 *iv);
> +
>  #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 6ec2d4543d9c..33213a01aab1 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..e9de1c6d874a
> --- /dev/null
> +++ b/lib/crypto/aescfb.c
> @@ -0,0 +1,75 @@
> +// 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>

I'd remove the newlines in-between.

> +
> +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);
> +}
> +
> +void aescfb_encrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
> +		    int len, const u8 *iv)
> +{
> +	while (len > 0) {
> +		u8 ks[AES_BLOCK_SIZE];
> +
> +		aescfb_encrypt_block(ctx, ks, iv);
> +		crypto_xor_cpy(dst, src, ks, min(len, AES_BLOCK_SIZE));
> +		iv = dst;
> +
> +		dst += AES_BLOCK_SIZE;
> +		src += AES_BLOCK_SIZE;
> +		len -= AES_BLOCK_SIZE;
> +	}
> +}
> +
> +void aescfb_decrypt(const struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src,
> +		    int len, const u8 *iv)
> +{
> +	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;
> +	}
> +}
> +
> +MODULE_DESCRIPTION("Generic AES-CFB library");
> +MODULE_AUTHOR("Ard Biesheuvel <ardb@kernel.org>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.35.3
> 

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko

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

* Re: [PATCH 02/12] tpm: move buffer handling from static inlines to real functions
  2023-02-16 20:14 ` [PATCH 02/12] tpm: move buffer handling from static inlines to real functions James Bottomley
@ 2023-02-27  8:18   ` Jarkko Sakkinen
  0 siblings, 0 replies; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  8:18 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:14:00PM -0500, James Bottomley wrote:
> 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>
> 
> ---
> v3: make tpm_buf_tag static
> ---
>  drivers/char/tpm/Makefile  |  1 +
>  drivers/char/tpm/tpm-buf.c | 95 ++++++++++++++++++++++++++++++++++++++
>  include/linux/tpm.h        | 86 ++++------------------------------
>  3 files changed, 105 insertions(+), 77 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..ca59b92e0f95
> --- /dev/null
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0
> +

This empty line should be removed.

> +/*
> + * Handing for tpm_buf structures to facilitate the building of commands
> + */
> +
> +#include <linux/module.h>
> +#include <linux/tpm.h>
> +

Now that symbols are compiled and also exported, it would be good to add
also kdoc's while at it, e.g.

/*
 * tpm_buf_init - Init a buffer for a TPM command
 * @buf:        uninitialized buffer
 * @tag:        tag of a TPM command
 * @ordinal:    number of a TPM command
 *
 * Allocate a page sized buffer from heap for a TPM command, and initialize
 * the command header.
 */

It is probably better to have an additional patch for this, as this one
should just move code around.

> +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)

Ditto.

I guess you can fill these out. I just put an example to give a rough
idea what to put.

> +{
> +	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)

Ditto.

> +{
> +	free_page((unsigned long)buf->data);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_destroy);
> +
> +u32 tpm_buf_length(struct tpm_buf *buf)

Ditto.

> +{
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +
> +	return be32_to_cpu(head->length);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_length);
> +
> +static u16 tpm_buf_tag(struct tpm_buf *buf)

Ditto.

> +{
> +	struct tpm_header *head = (struct tpm_header *)buf->data;
> +
> +	return be16_to_cpu(head->tag);
> +}
> +
> +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)

Ditto.

> +{
> +	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)

Ditto.

> +{
> +	__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)

Ditto.

> +{
> +	__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 dfeb25a0362d..150b39b6190e 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -322,84 +322,16 @@ 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 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)
> -{
> -	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
> 

Since you are now moving things around, I think we should make best of it.

I'd consider a subsequent patch after this to further clean up the flow:

struct tpm_buf *tpm_buf_init(u16 tag, u32 ordinal)
{
        struct tpm_buf *buf;

        buf = kzalloc(sizeof(*buf), GFP_KERNEL);
        if (!buf)
                goto err_alloc_buf;

	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
	if (!buf->data)
                goto err_alloc_page;

	buf->flags = 0;
	tpm_buf_reset(buf, tag, ordinal);

	return 0;
        
err_alloc_page:
        kfree(buf);

err_alloc_buf:
        return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL_GPL(tpm_buf_init);

void tpm_buf_destroy(struct tpm_buf *buf)
{
	free_page((unsigned long)buf->data);
        kfree(buf);
}

There is 28 call sites for tpm_buf_init() buf the change is
fairly trival as tpm_buf_destroy() calls can stay as they are.

BR, Jarkko

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

* Re: [PATCH 03/12] tpm: add buffer handling for TPM2B types
  2023-02-16 20:14 ` [PATCH 03/12] tpm: add buffer handling for TPM2B types James Bottomley
@ 2023-02-27  8:31   ` Jarkko Sakkinen
  2023-03-28 19:42     ` James Bottomley
  0 siblings, 1 reply; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  8:31 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:14:01PM -0500, James Bottomley wrote:
> Most complex TPM commands require appending TPM2B buffers to the
> command body.  Since TPM2B types are essentially variable size arrays,
> it makes it impossible to represent these complex command arguments as
> structures and we simply have to build them up using append primitives
> like these.
> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  drivers/char/tpm/tpm-buf.c | 71 +++++++++++++++++++++++++++++++++++---
>  include/linux/tpm.h        |  3 ++
>  2 files changed, 69 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index ca59b92e0f95..292c6f14f72c 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,17 +7,16 @@
>  #include <linux/module.h>
>  #include <linux/tpm.h>
>  
> -int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +static int __tpm_buf_init(struct tpm_buf *buf)
>  {
>  	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)
>  {
> @@ -29,17 +28,60 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_reset);
>  
> +int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +{
> +	int rc;
> +
> +	rc = __tpm_buf_init(buf);
> +	if (rc)
> +		return rc;
> +
> +	tpm_buf_reset(buf, tag, ordinal);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_init);
> +
> +int tpm_buf_init_2b(struct tpm_buf *buf)

kdoc

> +{
> +	struct tpm_header *head;
> +	int rc;
> +
> +	rc = __tpm_buf_init(buf);
> +	if (rc)
> +		return rc;
> +
> +	head = (struct tpm_header *) buf->data;
> +
> +	head->length = cpu_to_be32(sizeof(*head));
> +
> +	buf->flags = TPM_BUF_2B;

Please make tpm_buf_init() and tpm_buf_reset() to work for both cases.

This explodes the whole thing into an unmaintainable mess. It is better
to have a type as a parameter for tpm_buf_init() and have only single
flow instead of open coded and patched variation.

I'd simply just put it as:

struct tpm_buf *tpm_buf_init(u16 tag, u32 ordinal, bool tpm2b)

> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_init_2b);
> +
>  void tpm_buf_destroy(struct tpm_buf *buf)
>  {
>  	free_page((unsigned long)buf->data);
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_destroy);
>  
> +static void *tpm_buf_data(struct tpm_buf *buf)
> +{
> +	if (buf->flags & TPM_BUF_2B)
> +		return buf->data + TPM_HEADER_SIZE;
> +	return buf->data;
> +}
> +
>  u32 tpm_buf_length(struct tpm_buf *buf)
>  {
>  	struct tpm_header *head = (struct tpm_header *)buf->data;
> +	u32 len;
>  
> -	return be32_to_cpu(head->length);
> +	len = be32_to_cpu(head->length);
> +	if (buf->flags & TPM_BUF_2B)
> +		len -= sizeof(*head);
> +	return len;
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_length);
>  
> @@ -55,7 +97,7 @@ void tpm_buf_append(struct tpm_buf *buf,
>  		    unsigned int new_len)
>  {
>  	struct tpm_header *head = (struct tpm_header *) buf->data;
> -	u32 len = tpm_buf_length(buf);
> +	u32 len = be32_to_cpu(head->length);
>  
>  	/* Return silently if overflow has already happened. */
>  	if (buf->flags & TPM_BUF_OVERFLOW)
> @@ -93,3 +135,22 @@ 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);
> +
> +static void tpm_buf_reset_int(struct tpm_buf *buf)
> +{
> +	struct tpm_header *head;
> +
> +	head = (struct tpm_header *)buf->data;
> +	head->length = cpu_to_be32(sizeof(*head));
> +}
> +
> +void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
> +{
> +	u16 len = tpm_buf_length(tpm2b);
> +
> +	tpm_buf_append_u16(buf, len);
> +	tpm_buf_append(buf, tpm_buf_data(tpm2b), len);
> +	/* clear the buf for reuse */
> +	tpm_buf_reset_int(tpm2b);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 150b39b6190e..f2d4dab6d832 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -300,6 +300,7 @@ struct tpm_header {
>  
>  enum tpm_buf_flags {
>  	TPM_BUF_OVERFLOW	= BIT(0),
> +	TPM_BUF_2B		= BIT(1),
>  };


This is IMHO unnecessary complex.

I think we could just have two bools:

        bool overflow;
        bool tpm2b;

>  
>  struct tpm_buf {
> @@ -324,6 +325,7 @@ struct tpm2_hash {
>  
>  
>  int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
> +int tpm_buf_init_2b(struct tpm_buf *buf);
>  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);
> @@ -332,6 +334,7 @@ void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
>  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);
> +void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b);
>  
>  /*
>   * Check if TPM device is in the firmware upgrade mode.
> -- 
> 2.35.3
> 

BR, Jarkko

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

* Re: [PATCH 04/12] tpm: add cursor based buffer functions for response parsing
  2023-02-16 20:14 ` [PATCH 04/12] tpm: add cursor based buffer functions for response parsing James Bottomley
@ 2023-02-27  8:34   ` Jarkko Sakkinen
  0 siblings, 0 replies; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  8:34 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:14:02PM -0500, James Bottomley wrote:
> Once we have encryption and authentication, marshalling and
> unmarshalling sessions becomes hugely complex.  Add cursor based
> functions which update the current pointer to make response parsing
> easier.

You need to properly introduce the concept of cursor based function,
and how that maps into implementation.

I understand absolutely nothing of the change just by reading the
commit message, it is pretty much useless peace of text.

> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  drivers/char/tpm/tpm-buf.c | 29 +++++++++++++++++++++++++++++
>  include/linux/tpm.h        |  3 +++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index 292c6f14f72c..b76158f9bcd0 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,6 +7,8 @@
>  #include <linux/module.h>
>  #include <linux/tpm.h>
>  
> +#include <asm/unaligned.h>
> +
>  static int __tpm_buf_init(struct tpm_buf *buf)
>  {
>  	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
> @@ -154,3 +156,30 @@ void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
>  	tpm_buf_reset_int(tpm2b);
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
> +
> +/* functions for unmarshalling data and moving the cursor */
> +u8 tpm_get_inc_u8(const u8 **ptr)
> +{
> +	return *((*ptr)++);
> +}
> +EXPORT_SYMBOL_GPL(tpm_get_inc_u8);
> +
> +u16 tpm_get_inc_u16(const u8 **ptr)
> +{
> +	u16 val;
> +
> +	val = get_unaligned_be16(*ptr);
> +	*ptr += sizeof(val);
> +	return val;
> +}
> +EXPORT_SYMBOL_GPL(tpm_get_inc_u16);
> +
> +u32 tpm_get_inc_u32(const u8 **ptr)
> +{
> +	u32 val;
> +
> +	val = get_unaligned_be32(*ptr);
> +	*ptr += sizeof(val);
> +	return val;
> +}
> +EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index f2d4dab6d832..f7cff1d114b0 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -335,6 +335,9 @@ 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);
>  void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b);
> +u8 tpm_get_inc_u8(const u8 **ptr);
> +u16 tpm_get_inc_u16(const u8 **ptr);
> +u32 tpm_get_inc_u32(const u8 **ptr);
>  
>  /*
>   * Check if TPM device is in the firmware upgrade mode.
> -- 
> 2.35.3
> 

BR, Jarkko

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

* Re: [PATCH 05/12] tpm: add buffer function to point to returned parameters
  2023-02-16 20:14 ` [PATCH 05/12] tpm: add buffer function to point to returned parameters James Bottomley
@ 2023-02-27  8:36   ` Jarkko Sakkinen
  0 siblings, 0 replies; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  8:36 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:14:03PM -0500, James Bottomley wrote:
> Introducing encryption sessions changes where the return parameters
> are located in the buffer because if a return session is present
> they're 4 bytes beyond the header with those 4 bytes showing the
> parameter length.  If there is no return session, then they're in the
> usual place immediately after the header.  The tpm_buf_parameters()
> encapsulates this calculation and should be used everywhere
> &buf.data[TPM_HEADER_SIZE] is used now
> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  drivers/char/tpm/tpm-buf.c | 10 ++++++++++
>  include/linux/tpm.h        |  2 ++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index b76158f9bcd0..2518b675e866 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -183,3 +183,13 @@ u32 tpm_get_inc_u32(const u8 **ptr)
>  	return val;
>  }
>  EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
> +
> +u8 *tpm_buf_parameters(struct tpm_buf *buf)

kdoc

> +{
> +	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 f7cff1d114b0..fa8d1f932c0f 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -339,6 +339,8 @@ u8 tpm_get_inc_u8(const u8 **ptr);
>  u16 tpm_get_inc_u16(const u8 **ptr);
>  u32 tpm_get_inc_u32(const u8 **ptr);
>  
> +u8 *tpm_buf_parameters(struct tpm_buf *buf);
> +
>  /*
>   * Check if TPM device is in the firmware upgrade mode.
>   */
> -- 
> 2.35.3
> 

BR, Jarkko

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

* Re: [PATCH 06/12] tpm: export the context save and load commands
  2023-02-16 20:14 ` [PATCH 06/12] tpm: export the context save and load commands James Bottomley
@ 2023-02-27  8:37   ` Jarkko Sakkinen
  2023-04-03 16:54     ` James Bottomley
  0 siblings, 1 reply; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  8:37 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:14:04PM -0500, James Bottomley wrote:
> 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>

These did not need EXPORT_SYMBOL_GPL()?

> ---
>  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 24ee4e1cc452..a5fe37977103 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -237,6 +237,10 @@ 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 ffb35f0154c1..d77ee4af9d65 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
> 

BR, Jarkko

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

* Re: [PATCH 08/12] tpm: add hmac checks to tpm2_pcr_extend()
  2023-02-16 20:14 ` [PATCH 08/12] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
@ 2023-02-27  9:16   ` Jarkko Sakkinen
  0 siblings, 0 replies; 28+ messages in thread
From: Jarkko Sakkinen @ 2023-02-27  9:16 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Thu, Feb 16, 2023 at 03:14:06PM -0500, James Bottomley wrote:
> We use tpm2_pcr_extend() in trusted keys to extend a PCR to prevent a

"Use tpm2_pcr_extend()"

> key from being re-loaded until the next reboot.  To use this
> functionality securely, that extend must be protected by a session
> hmac.

There's no description of action taken. This is only motivation part.

> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  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 056dad3dd5c9..ef038cc71f9c 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
> 

BR, Jarkko

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

* Re: [PATCH 03/12] tpm: add buffer handling for TPM2B types
  2023-02-27  8:31   ` Jarkko Sakkinen
@ 2023-03-28 19:42     ` James Bottomley
  0 siblings, 0 replies; 28+ messages in thread
From: James Bottomley @ 2023-03-28 19:42 UTC (permalink / raw)
  To: Jarkko Sakkinen; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Mon, 2023-02-27 at 10:31 +0200, Jarkko Sakkinen wrote:
> On Thu, Feb 16, 2023 at 03:14:01PM -0500, James Bottomley wrote:
> > Most complex TPM commands require appending TPM2B buffers to the
> > command body.  Since TPM2B types are essentially variable size
> > arrays, it makes it impossible to represent these complex command
> > arguments as structures and we simply have to build them up using
> > append primitives like these.
> > 
> > Signed-off-by: James Bottomley
> > <James.Bottomley@HansenPartnership.com>
> > ---
> >  drivers/char/tpm/tpm-buf.c | 71
> > +++++++++++++++++++++++++++++++++++---
> >  include/linux/tpm.h        |  3 ++
> >  2 files changed, 69 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-
> > buf.c
> > index ca59b92e0f95..292c6f14f72c 100644
> > --- a/drivers/char/tpm/tpm-buf.c
> > +++ b/drivers/char/tpm/tpm-buf.c
> > @@ -7,17 +7,16 @@
> >  #include <linux/module.h>
> >  #include <linux/tpm.h>
> >  
> > -int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> > +static int __tpm_buf_init(struct tpm_buf *buf)
> >  {
> >         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)
> >  {
> > @@ -29,17 +28,60 @@ void tpm_buf_reset(struct tpm_buf *buf, u16
> > tag, u32 ordinal)
> >  }
> >  EXPORT_SYMBOL_GPL(tpm_buf_reset);
> >  
> > +int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> > +{
> > +       int rc;
> > +
> > +       rc = __tpm_buf_init(buf);
> > +       if (rc)
> > +               return rc;
> > +
> > +       tpm_buf_reset(buf, tag, ordinal);
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(tpm_buf_init);
> > +
> > +int tpm_buf_init_2b(struct tpm_buf *buf)
> 
> kdoc

I'm currently working on adding kdoc to everything.  However:

> > +{
> > +       struct tpm_header *head;
> > +       int rc;
> > +
> > +       rc = __tpm_buf_init(buf);
> > +       if (rc)
> > +               return rc;
> > +
> > +       head = (struct tpm_header *) buf->data;
> > +
> > +       head->length = cpu_to_be32(sizeof(*head));
> > +
> > +       buf->flags = TPM_BUF_2B;
> 
> Please make tpm_buf_init() and tpm_buf_reset() to work for both
> cases.

That's not a good idea: tpm_buf_init() and tpm_buf_reset() are used to
initialize *command* buffers.  tpm_buf_init_2b() is used for parameters
within commands and can't encompass whole commands, so the arguments
are different (that's why tpm_buf_init_2b() has no tag or ordinal).

> This explodes the whole thing into an unmaintainable mess. It is
> better to have a type as a parameter for tpm_buf_init() and have only
> single flow instead of open coded and patched variation.
> 
> I'd simply just put it as:
> 
> struct tpm_buf *tpm_buf_init(u16 tag, u32 ordinal, bool tpm2b)

The convention in Linux is that it's better to have named initializers
if we can rather than use less obvious booleans or flags ... think the
conversion from printk(KERN_ERR, ...) to pr_err(...)

Additionally tag and ordinal have no meaning for a tpm2b, so you're
really gluing two incompatible initializations into one which is bound
to cause confusion.

I've no objection in principle to doing a reset of a tpm2b (except,
again, it has no use for tag or ordinal) but I've just not got any code
that would use it, so I was leaving it out until someone had an actual
use case.

[...]
> > index 150b39b6190e..f2d4dab6d832 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -300,6 +300,7 @@ struct tpm_header {
> >  
> >  enum tpm_buf_flags {
> >         TPM_BUF_OVERFLOW        = BIT(0),
> > +       TPM_BUF_2B              = BIT(1),
> >  };
> 
> 
> This is IMHO unnecessary complex.
> 
> I think we could just have two bools:
> 
>         bool overflow;
>         bool tpm2b;

The advice (in the coding-style.rst bool section) is not to do this but
go the other way (so use flags instead of a string of bools).  The
reason is that even though bool represents a true/false value, it
usually takes one machine word (32 bits or sometimes more) to do it, so
bools tend to bloat structures over single bit fields.

James


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

* Re: [PATCH 06/12] tpm: export the context save and load commands
  2023-02-27  8:37   ` Jarkko Sakkinen
@ 2023-04-03 16:54     ` James Bottomley
  0 siblings, 0 replies; 28+ messages in thread
From: James Bottomley @ 2023-04-03 16:54 UTC (permalink / raw)
  To: Jarkko Sakkinen; +Cc: linux-integrity, keyrings, Ard Biesheuvel

On Mon, 2023-02-27 at 10:37 +0200, Jarkko Sakkinen wrote:
> On Thu, Feb 16, 2023 at 03:14:04PM -0500, James Bottomley wrote:
> > 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>
> 
> These did not need EXPORT_SYMBOL_GPL()?

No, because they're still internal to the overall tpm.ko even if it is
compiled as a module.  I don't think there's a huge reason to keep them
as an internal only to the tpm core API, but equally without a consumer
outside the core module, there's no reason to export them.

James


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

end of thread, other threads:[~2023-04-03 16:54 UTC | newest]

Thread overview: 28+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-02-16 20:13 [PATCH 00/12] add integrity and security to TPM2 transactions James Bottomley
2023-02-16 20:13 ` [PATCH 01/12] crypto: lib - implement library version of AES in CFB mode James Bottomley
2023-02-27  7:47   ` Jarkko Sakkinen
2023-02-16 20:14 ` [PATCH 02/12] tpm: move buffer handling from static inlines to real functions James Bottomley
2023-02-27  8:18   ` Jarkko Sakkinen
2023-02-16 20:14 ` [PATCH 03/12] tpm: add buffer handling for TPM2B types James Bottomley
2023-02-27  8:31   ` Jarkko Sakkinen
2023-03-28 19:42     ` James Bottomley
2023-02-16 20:14 ` [PATCH 04/12] tpm: add cursor based buffer functions for response parsing James Bottomley
2023-02-27  8:34   ` Jarkko Sakkinen
2023-02-16 20:14 ` [PATCH 05/12] tpm: add buffer function to point to returned parameters James Bottomley
2023-02-27  8:36   ` Jarkko Sakkinen
2023-02-16 20:14 ` [PATCH 06/12] tpm: export the context save and load commands James Bottomley
2023-02-27  8:37   ` Jarkko Sakkinen
2023-04-03 16:54     ` James Bottomley
2023-02-16 20:14 ` [PATCH 07/12] tpm: Add full HMAC and encrypt/decrypt session handling code James Bottomley
2023-02-16 23:37   ` kernel test robot
2023-02-17 11:30   ` kernel test robot
2023-02-17 14:22     ` James Bottomley
2023-02-17 14:23       ` Ard Biesheuvel
2023-02-16 20:14 ` [PATCH 08/12] tpm: add hmac checks to tpm2_pcr_extend() James Bottomley
2023-02-27  9:16   ` Jarkko Sakkinen
2023-02-16 20:14 ` [PATCH 09/12] tpm: add session encryption protection to tpm2_get_random() James Bottomley
2023-02-16 20:14 ` [PATCH 10/12] KEYS: trusted: Add session encryption protection to the seal/unseal path James Bottomley
2023-02-16 20:40 ` [PATCH 11/12] tpm: add the null key name as a sysfs export James Bottomley
2023-02-17 10:59   ` kernel test robot
2023-02-16 20:41 ` [PATCH 12/12] Documentation: add tpm-security.rst James Bottomley
2023-02-17 22:43 ` [PATCH 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen

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