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* [PATCH v6 00/12] add integrity and security to TPM2 transactions
@ 2019-09-09 12:16 James Bottomley
  2019-09-09 12:17 ` [PATCH v6 01/12] tpm-buf: move from static inlines to real functions James Bottomley
                   ` (12 more replies)
  0 siblings, 13 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:16 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

Link to previous cover letter:

https://lore.kernel.org/linux-integrity/1540193596.3202.7.camel@HansenPartnership.com/

This is marked v6 instead of v5 because I did a v5 after feedback on v4
but didn't get around to posting it and then had to rework the whole of
the kernel space handling while I was on holiday.  I also added the
documentation of how the whole thing works and the rationale for doing
it in tpm-security.rst (patch 11).  The main reason for doing this now
is so we have something to discuss at Plumbers.

The new patch set implements the various splits requested, but the main
changes are that the kernel space is gone and is replaced by a context
save and restore of the generated null seed.  This is easier to handle
than a full kernel space given the new threading for TPM spaces, but
conceptually it is still very like a space.  I've also made whether
integrity and encryption is turned on a Kconfig option.

James

---

James Bottomley (12):
  tpm-buf: move from static inlines to real functions
  tpm-buf: add handling for TPM2B types
  tpm-buf: add cursor based functions for response parsing
  tpm2-space: export the context save and load commands
  tpm2-sessions: Add full HMAC and encrypt/decrypt session handling
  tpm-buf: add tpm_buf_parameters()
  tpm2: add hmac checks to tpm2_pcr_extend()
  tpm2: add session encryption protection to tpm2_get_random()
  trusted keys: Add session encryption protection to the seal/unseal
    path
  tpm: add the null key name as a tpm2 sysfs variable
  Documentation: add tpm-security.rst
  tpm2-sessions: NOT FOR COMMITTING add sessions testing

 Documentation/security/tpm/tpm-security.rst |  204 +++++
 drivers/char/tpm/Kconfig                    |   11 +
 drivers/char/tpm/Makefile                   |    4 +
 drivers/char/tpm/tpm-buf.c                  |  202 +++++
 drivers/char/tpm/tpm-chip.c                 |    1 +
 drivers/char/tpm/tpm-sysfs.c                |   27 +-
 drivers/char/tpm/tpm.h                      |  117 +--
 drivers/char/tpm/tpm2-cmd.c                 |  202 +++--
 drivers/char/tpm/tpm2-sessions-test.c       |  795 ++++++++++++++++++
 drivers/char/tpm/tpm2-sessions.c            | 1204 +++++++++++++++++++++++++++
 drivers/char/tpm/tpm2-sessions.h            |  138 +++
 drivers/char/tpm/tpm2-space.c               |    8 +-
 include/linux/tpm.h                         |   29 +
 13 files changed, 2787 insertions(+), 155 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-test.c
 create mode 100644 drivers/char/tpm/tpm2-sessions.c
 create mode 100644 drivers/char/tpm/tpm2-sessions.h

-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 01/12] tpm-buf: move from static inlines to real functions
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
@ 2019-09-09 12:17 ` James Bottomley
  2019-09-20 14:06   ` Jarkko Sakkinen
  2019-09-09 12:18 ` [PATCH v6 02/12] tpm-buf: add handling for TPM2B types James Bottomley
                   ` (11 subsequent siblings)
  12 siblings, 1 reply; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:17 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

This separates out the old tpm_buf_... handling functions from static
inlines in tpm.h and makes them their own tpm-buf.c file.  This is a
precursor so we can add new functions for other TPM type handling

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

---

v2: added this patch to separate out the API changes
v3: added tpm_buf_reset_cmd()
v6: extract first then add functions
---
 drivers/char/tpm/Makefile  |   1 +
 drivers/char/tpm/tpm-buf.c | 118 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm.h     |  90 ++++------------------------------
 3 files changed, 129 insertions(+), 80 deletions(-)
 create mode 100644 drivers/char/tpm/tpm-buf.c

diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index a01c4cab902a..78bd025b808a 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..9fa8a9cb0fdf
--- /dev/null
+++ b/drivers/char/tpm/tpm-buf.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Handing for tpm_buf structures to facilitate the building of commands
+ */
+
+#include "tpm.h"
+
+#include <linux/module.h>
+
+static int __tpm_buf_init(struct tpm_buf *buf)
+{
+	buf->data_page = alloc_page(GFP_HIGHUSER);
+	if (!buf->data_page)
+		return -ENOMEM;
+
+	buf->flags = 0;
+	buf->data = kmap(buf->data_page);
+
+	return 0;
+}
+
+void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	struct tpm_header *head;
+
+	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);
+
+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);
+
+void tpm_buf_destroy(struct tpm_buf *buf)
+{
+	kunmap(buf->data_page);
+	__free_page(buf->data_page);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_destroy);
+
+u32 tpm_buf_length(struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	u32 len;
+
+	len = be32_to_cpu(head->length);
+	if (buf->flags & TPM_BUF_2B)
+		len -= sizeof(*head);
+	return len;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_length);
+
+u16 tpm_buf_tag(struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	return be16_to_cpu(head->tag);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_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 = be32_to_cpu(head->length);
+
+	/* 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/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index a7fea3e0ca86..8c5b8bba60d2 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -281,6 +281,7 @@ enum tpm_sub_capabilities {
 
 enum tpm_buf_flags {
 	TPM_BUF_OVERFLOW	= BIT(0),
+	TPM_BUF_2B		= BIT(1),
 };
 
 struct tpm_buf {
@@ -289,86 +290,15 @@ struct tpm_buf {
 	u8 *data;
 };
 
-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_page = alloc_page(GFP_HIGHUSER);
-	if (!buf->data_page)
-		return -ENOMEM;
-
-	buf->flags = 0;
-	buf->data = kmap(buf->data_page);
-	tpm_buf_reset(buf, tag, ordinal);
-	return 0;
-}
-
-static inline void tpm_buf_destroy(struct tpm_buf *buf)
-{
-	kunmap(buf->data_page);
-	__free_page(buf->data_page);
-}
-
-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);
 
 extern struct class *tpm_class;
 extern struct class *tpmrm_class;
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 02/12] tpm-buf: add handling for TPM2B types
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
  2019-09-09 12:17 ` [PATCH v6 01/12] tpm-buf: move from static inlines to real functions James Bottomley
@ 2019-09-09 12:18 ` James Bottomley
  2019-09-20 14:18   ` Jarkko Sakkinen
  2019-09-09 12:19 ` [PATCH v6 03/12] tpm-buf: add cursor based functions for response parsing James Bottomley
                   ` (10 subsequent siblings)
  12 siblings, 1 reply; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:18 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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 | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm.h     |  2 ++
 2 files changed, 49 insertions(+)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 9fa8a9cb0fdf..8c1ed8a14e01 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -8,6 +8,8 @@
 
 #include <linux/module.h>
 
+#include <asm/unaligned.h>
+
 static int __tpm_buf_init(struct tpm_buf *buf)
 {
 	buf->data_page = alloc_page(GFP_HIGHUSER);
@@ -46,6 +48,24 @@ int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
 }
 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)
 {
 	kunmap(buf->data_page);
@@ -53,6 +73,13 @@ void tpm_buf_destroy(struct tpm_buf *buf)
 }
 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;
@@ -116,3 +143,23 @@ 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/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 8c5b8bba60d2..7627917db345 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -292,6 +292,7 @@ struct tpm_buf {
 
 int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
+int tpm_buf_init_2b(struct tpm_buf *buf);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
 void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
@@ -299,6 +300,7 @@ 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);
 
 extern struct class *tpm_class;
 extern struct class *tpmrm_class;
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 03/12] tpm-buf: add cursor based functions for response parsing
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
  2019-09-09 12:17 ` [PATCH v6 01/12] tpm-buf: move from static inlines to real functions James Bottomley
  2019-09-09 12:18 ` [PATCH v6 02/12] tpm-buf: add handling for TPM2B types James Bottomley
@ 2019-09-09 12:19 ` James Bottomley
  2019-09-09 12:19 ` [PATCH v6 04/12] tpm2-space: export the context save and load commands James Bottomley
                   ` (9 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:19 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

It's very convenient when parsing responses to have a cursor you
simply move over the response extracting the data.  Add such cursor
functions for the TPM unsigned integer types.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-buf.c | 26 ++++++++++++++++++++++++++
 drivers/char/tpm/tpm.h     |  4 ++++
 2 files changed, 30 insertions(+)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 8c1ed8a14e01..553adb84b0ac 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -163,3 +163,29 @@ void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *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/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 7627917db345..d942188debc9 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -302,6 +302,10 @@ 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);
+
 extern struct class *tpm_class;
 extern struct class *tpmrm_class;
 extern dev_t tpm_devt;
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 04/12] tpm2-space: export the context save and load commands
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (2 preceding siblings ...)
  2019-09-09 12:19 ` [PATCH v6 03/12] tpm-buf: add cursor based functions for response parsing James Bottomley
@ 2019-09-09 12:19 ` James Bottomley
  2019-09-09 12:20 ` [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling James Bottomley
                   ` (8 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:19 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

The TPM2 session 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 d942188debc9..85a7302ddfeb 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -399,6 +399,10 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
 		       size_t cmdsiz);
 int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
 		      size_t *bufsiz);
+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);
 
 int 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 982d341d8837..ca1cb56ccc51 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -65,8 +65,8 @@ 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;
@@ -116,8 +116,8 @@ 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;
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (3 preceding siblings ...)
  2019-09-09 12:19 ` [PATCH v6 04/12] tpm2-space: export the context save and load commands James Bottomley
@ 2019-09-09 12:20 ` James Bottomley
  2019-09-20 14:34   ` Jarkko Sakkinen
  2019-09-09 12:21 ` [PATCH v6 06/12] tpm-buf: add tpm_buf_parameters() James Bottomley
                   ` (7 subsequent siblings)
  12 siblings, 1 reply; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:20 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

This code adds true session based HMAC authentication plus parameter
decryption and response encryption using AES.

The basic design of this code 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 now needs a primary
key to encrypt the session salt to, so we derive an EC key from the
NULL seed and save its context 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: Added docbook and improved response check API
v3: Add readpublic, fix hmac length, add API for close on error
    allow for the hmac session not being first in the sessions
v4: Make NULL seed template exactly match the SRK ECC template.
    Also check the NULL primary key name is what getpublic returns
    to prevent spoofing.  Also parametrise the name size for reuse
v5: Move to sync_skcipher API
v6: eliminate kernel space and use context save for null seed and
    make feature conditional on CONFIG_TPM_BUS_SECURITY
---
 drivers/char/tpm/Kconfig         |   11 +
 drivers/char/tpm/Makefile        |    1 +
 drivers/char/tpm/tpm-buf.c       |    1 +
 drivers/char/tpm/tpm.h           |   20 +-
 drivers/char/tpm/tpm2-cmd.c      |   22 +-
 drivers/char/tpm/tpm2-sessions.c | 1203 ++++++++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm2-sessions.h |  137 +++++
 include/linux/tpm.h              |   29 +
 8 files changed, 1411 insertions(+), 13 deletions(-)
 create mode 100644 drivers/char/tpm/tpm2-sessions.c
 create mode 100644 drivers/char/tpm/tpm2-sessions.h

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 88a3c06fc153..96b09adfc163 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -9,6 +9,9 @@ menuconfig TCG_TPM
 	imply SECURITYFS
 	select CRYPTO
 	select CRYPTO_HASH_INFO
+	select CRYPTO_ECDH
+	select CRYPTO_AES
+	select CRYPTO_CFB
 	---help---
 	  If you have a TPM security chip in your system, which
 	  implements the Trusted Computing Group's specification,
@@ -27,6 +30,14 @@ menuconfig TCG_TPM
 
 if TCG_TPM
 
+config TPM_BUS_SECURITY
+       bool "Use secure transactions on the TPM bus"
+       default y
+       ---help---
+         Setting this causes us to deploy a tamper resistent scheme
+	 for communicating with the TPM to prevent or detect bus snooping
+	 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 78bd025b808a..8f9e58317048 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 553adb84b0ac..f56350123a08 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -31,6 +31,7 @@ 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.h b/drivers/char/tpm/tpm.h
index 85a7302ddfeb..ebead8e4c3fe 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -80,6 +80,7 @@ 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 */
@@ -116,6 +117,8 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_READ_PUBLIC		= 0x0173,
+	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
 	TPM2_CC_GET_CAPABILITY	        = 0x017A,
 	TPM2_CC_GET_RANDOM	        = 0x017B,
@@ -128,6 +131,7 @@ enum tpm2_command_codes {
 };
 
 enum tpm2_permanent_handles {
+	TPM2_RH_NULL		= 0x40000007,
 	TPM2_RS_PW		= 0x40000009,
 };
 
@@ -286,7 +290,8 @@ enum tpm_buf_flags {
 
 struct tpm_buf {
 	struct page *data_page;
-	unsigned int flags;
+	u8 flags;
+	u8 handles;
 	u8 *data;
 };
 
@@ -306,6 +311,9 @@ u8 tpm_get_inc_u8(const u8 **ptr);
 u16 tpm_get_inc_u16(const u8 **ptr);
 u32 tpm_get_inc_u32(const u8 **ptr);
 
+/* opaque structure, holds auth session parameters like the session key */
+struct tpm2_auth;
+
 extern struct class *tpm_class;
 extern struct class *tpmrm_class;
 extern dev_t tpm_devt;
@@ -408,4 +416,14 @@ int 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 ba9acae83bff..d120b0a260eb 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -12,17 +12,10 @@
  */
 
 #include "tpm.h"
+#include "tpm2-sessions.h"
 #include <crypto/hash_info.h>
 #include <keys/trusted-type.h>
 
-enum tpm2_object_attributes {
-	TPM2_OA_USER_WITH_AUTH		= BIT(6),
-};
-
-enum tpm2_session_attributes {
-	TPM2_SA_CONTINUE_SESSION	= BIT(0),
-};
-
 struct tpm2_hash {
 	unsigned int crypto_id;
 	unsigned int tpm_id;
@@ -388,10 +381,10 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
  * @hmac: the session HMAC or password, may be NULL if not used
  * @hmac_len: the session HMAC or password length, maybe 0 if not used
  */
-static void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
-				 const u8 *nonce, u16 nonce_len,
-				 u8 attributes,
-				 const u8 *hmac, u16 hmac_len)
+void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
+			  const u8 *nonce, u16 nonce_len,
+			  u8 attributes,
+			  const u8 *hmac, u16 hmac_len)
 {
 	tpm_buf_append_u32(buf, 9 + nonce_len + hmac_len);
 	tpm_buf_append_u32(buf, session_handle);
@@ -1042,6 +1035,11 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 
 	rc = tpm2_get_cc_attrs_tbl(chip);
 
+	if (rc)
+		goto out;
+
+	rc = tpm2_sessions_init(chip);
+
 out:
 	if (rc > 0)
 		rc = -ENODEV;
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
new file mode 100644
index 000000000000..7307f061e5df
--- /dev/null
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -0,0 +1,1203 @@
+// 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 "tpm2-sessions.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>
+#include <crypto/skcipher.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;
+	/* saved session attributes */
+	u8 attrs;
+	__be32 ordinal;
+	struct crypto_sync_skcipher *aes;
+	struct tpm_chip *chip;
+	/* 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 + SHA256_DIGEST_SIZE];
+};
+
+/*
+ * this is our static crypto shash.  This is possible because the hash
+ * is multi-threaded and all the state stored in the desc
+ */
+static struct crypto_shash *sha256_hash;
+
+/*
+ * 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 shash_desc *desc, u8 *key, int keylen)
+{
+	u8 pad[SHA256_BLOCK_SIZE];
+	int i;
+
+	desc->tfm = sha256_hash;
+	crypto_shash_init(desc);
+	for (i = 0; i < sizeof(pad); i++) {
+		if (i < keylen)
+			pad[i] = key[i];
+		else
+			pad[i] = 0;
+		pad[i] ^= HMAC_IPAD_VALUE;
+	}
+	crypto_shash_update(desc, pad, sizeof(pad));
+}
+
+static void hmac_final(struct shash_desc *desc, 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 */
+	crypto_shash_final(desc, out);
+
+	/* reuse the desc */
+	crypto_shash_init(desc);
+	crypto_shash_update(desc, pad, sizeof(pad));
+	crypto_shash_update(desc, out, SHA256_DIGEST_SIZE);
+	crypto_shash_final(desc, 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) {
+		SHASH_DESC_ON_STACK(desc, sha256_hash);
+		__be32 c = cpu_to_be32(counter);
+
+		hmac_init(desc, key, keylen);
+		crypto_shash_update(desc, (u8 *)&c, sizeof(c));
+		crypto_shash_update(desc, label, strlen(label)+1);
+		crypto_shash_update(desc, u, SHA256_DIGEST_SIZE);
+		crypto_shash_update(desc, v, SHA256_DIGEST_SIZE);
+		crypto_shash_update(desc, (u8 *)&bits, sizeof(bits));
+		hmac_final(desc, key, keylen, out);
+	}
+}
+
+/*
+ * 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)
+{
+	SHASH_DESC_ON_STACK(desc, sha256_hash);
+	/*
+	 * 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);
+
+	desc->tfm = sha256_hash;
+
+	crypto_shash_init(desc);
+	/* counter (BE) */
+	crypto_shash_update(desc, (u8 *)&c, sizeof(c));
+	/* secret value */
+	crypto_shash_update(desc, z, EC_PT_SZ);
+	/* string including trailing zero */
+	crypto_shash_update(desc, str, strlen(str)+1);
+	crypto_shash_update(desc, pt_u, EC_PT_SZ);
+	crypto_shash_update(desc, pt_v, EC_PT_SZ);
+	crypto_shash_final(desc, keyout);
+}
+
+static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
+				struct tpm2_auth *auth)
+{
+	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;
+	u8 *secret;
+
+	secret = kmalloc(EC_PT_SZ, GFP_KERNEL);
+	if (!secret)
+		return;
+
+	p.curve_id = ECC_CURVE_NIST_P256;
+
+	/* 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", 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, secret, 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 */
+	KDFe(secret, "SECRET", x, chip->ec_point_x, auth->salt);
+ out:
+	crypto_free_kpp(kpp);
+}
+
+/**
+ * tpm_buf_append_hmac_session() append a TPM session element
+ * @buf: The buffer to be appended
+ * @auth: the auth structure allocated by tpm2_start_auth_session()
+ * @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_buf *buf, struct tpm2_auth *auth,
+				 u8 attributes, u8 *passphrase,
+				 int passphraselen)
+{
+	u8 nonce[SHA256_DIGEST_SIZE];
+	u32 len;
+
+	/*
+	 * 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
+ * @buf: The buffer to be appended
+ * @auth: the auth structure allocated by tpm2_start_auth_session()
+ *
+ * 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_buf *buf, struct tpm2_auth *auth)
+{
+	u32 cc, handles, val;
+	struct tpm_chip *chip = auth->chip;
+	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];
+	SHASH_DESC_ON_STACK(desc, sha256_hash);
+
+	/* save the command code in BE format */
+	auth->ordinal = head->ordinal;
+
+	desc->tfm = sha256_hash;
+
+	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) {
+		struct scatterlist sg[1];
+		u16 len;
+		SYNC_SKCIPHER_REQUEST_ON_STACK(req, auth->aes);
+		DECLARE_CRYPTO_WAIT(wait);
+
+		skcipher_request_set_sync_tfm(req, auth->aes);
+		skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
+					      crypto_req_done, &wait);
+
+		/* 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);
+		crypto_sync_skcipher_setkey(auth->aes, auth->scratch, AES_KEYBYTES);
+		len = tpm_get_inc_u16(&p);
+		sg_init_one(sg, p, len);
+		skcipher_request_set_crypt(req, sg, sg, len,
+					   auth->scratch + AES_KEYBYTES);
+		crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+		/* reset p to beginning of parameters for HMAC */
+		p -= 2;
+	}
+
+	crypto_shash_init(desc);
+	/* ordinal is already BE */
+	crypto_shash_update(desc, (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) {
+			crypto_shash_update(desc, auth->name[i],
+					    SHA256_DIGEST_SIZE + 2);
+		} else {
+			__be32 h = cpu_to_be32(auth->name_h[i]);
+
+			crypto_shash_update(desc, (u8 *)&h, 4);
+		}
+	}
+	if (buf->data - s != tpm_buf_length(buf))
+		crypto_shash_update(desc, s, buf->data
+				    + tpm_buf_length(buf) - s);
+	crypto_shash_final(desc, cphash);
+
+	/* now calculate the hmac */
+	hmac_init(desc, auth->session_key, sizeof(auth->session_key)
+		  + auth->passphraselen);
+	crypto_shash_update(desc, cphash, sizeof(cphash));
+	crypto_shash_update(desc, auth->our_nonce, sizeof(auth->our_nonce));
+	crypto_shash_update(desc, auth->tpm_nonce, sizeof(auth->tpm_nonce));
+	crypto_shash_update(desc, &auth->attrs, 1);
+	hmac_final(desc, 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 != SHA256_DIGEST_SIZE + 2)
+		return -EINVAL;
+	memcpy(name, data, SHA256_DIGEST_SIZE + 2);
+	/* 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
+ * @buf: The buffer to be appended
+ * @auth: the auth structure allocated by tpm2_start_auth_session()
+ * @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_buf *buf, struct tpm2_auth *auth,
+			 u32 handle, u8 *name)
+{
+	int slot;
+	u8 mso = handle >> 24;
+
+	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE)/4;
+	if (slot >= AUTH_MAX_NAMES) {
+		dev_err(&auth->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(auth->chip, handle, auth->name[slot]);
+	} else {
+		if (name)
+			dev_err(&auth->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, SHA256_DIGEST_SIZE + 2);
+}
+EXPORT_SYMBOL(tpm_buf_append_name);
+
+/**
+ * tpm_buf_check_hmac_response() - check the TPM return HMAC for correctness
+ * @buf: the original command buffer (which now contains the response)
+ * @auth: the auth structure allocated by tpm2_start_auth_session()
+ * @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_buf *buf, struct tpm2_auth *auth,
+				int rc)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	struct tpm_chip *chip = auth->chip;
+	const u8 *s, *p;
+	u8 rphash[SHA256_DIGEST_SIZE];
+	u32 attrs;
+	SHASH_DESC_ON_STACK(desc, sha256_hash);
+	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
+	 */
+	desc->tfm = sha256_hash;
+	crypto_shash_init(desc);
+	/* yes, I know this is now zero, but it's what the standard says */
+	crypto_shash_update(desc, (u8 *)&head->return_code,
+			    sizeof(head->return_code));
+	/* ordinal is already BE */
+	crypto_shash_update(desc, (u8 *)&auth->ordinal, sizeof(auth->ordinal));
+	crypto_shash_update(desc, p, parm_len);
+	crypto_shash_final(desc, rphash);
+
+	/* now calculate the hmac */
+	hmac_init(desc, auth->session_key, sizeof(auth->session_key)
+		  + auth->passphraselen);
+	crypto_shash_update(desc, rphash, sizeof(rphash));
+	crypto_shash_update(desc, auth->tpm_nonce, sizeof(auth->tpm_nonce));
+	crypto_shash_update(desc, auth->our_nonce, sizeof(auth->our_nonce));
+	crypto_shash_update(desc, &auth->attrs, 1);
+	/* we're done with the rphash, so put our idea of the hmac there */
+	hmac_final(desc, auth->session_key, sizeof(auth->session_key)
+		   + auth->passphraselen, rphash);
+	if (memcmp(rphash, s, SHA256_DIGEST_SIZE) == 0) {
+		rc = 0;
+	} else {
+		dev_err(&auth->chip->dev, "TPM: HMAC check failed\n");
+		goto out;
+	}
+
+	/* now do response decryption */
+	if (auth->attrs & TPM2_SA_ENCRYPT) {
+		struct scatterlist sg[1];
+		SYNC_SKCIPHER_REQUEST_ON_STACK(req, auth->aes);
+		DECLARE_CRYPTO_WAIT(wait);
+
+		skcipher_request_set_sync_tfm(req, auth->aes);
+		skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
+					      crypto_req_done, &wait);
+
+		/* 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);
+		crypto_sync_skcipher_setkey(auth->aes, auth->scratch, AES_KEYBYTES);
+		len = tpm_get_inc_u16(&p);
+		sg_init_one(sg, p, len);
+		skcipher_request_set_crypt(req, sg, sg, len,
+					   auth->scratch + AES_KEYBYTES);
+		crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
+	}
+
+ out:
+	if ((auth->attrs & TPM2_SA_CONTINUE_SESSION) == 0) {
+		/* manually close the session if it wasn't consumed */
+		if (rc)
+			tpm2_flush_context(chip, auth->handle);
+		crypto_free_sync_skcipher(auth->aes);
+		kfree(auth);
+	} else {
+		/* reset for next use  */
+		auth->session = TPM_HEADER_SIZE;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL(tpm_buf_check_hmac_response);
+
+/**
+ * tpm2_end_auth_session - kill the allocated auth session
+ * @auth: the auth structure allocated by tpm2_start_auth_session()
+ *
+ * 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 tpm2_auth *auth)
+{
+	tpm2_flush_context(auth->chip, auth->handle);
+	crypto_free_sync_skcipher(auth->aes);
+	kfree(auth);
+}
+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 tpm2_auth **authp)
+{
+	struct tpm_buf buf;
+	struct tpm2_auth *auth;
+	int rc;
+	unsigned int offset = 0; /* dummy offset for null seed context */
+	u32 nullkey;
+
+	auth = kmalloc(sizeof(**authp), GFP_KERNEL);
+	if (!auth)
+		return -ENOMEM;
+
+	rc = tpm2_load_context(chip, chip->tpmkeycontext, &offset,
+			       &nullkey);
+	if (rc)
+		return rc;
+
+	auth->chip = chip;
+	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, auth);
+	/* 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;
+
+	auth->aes = crypto_alloc_sync_skcipher("cfb(aes)", 0, 0);
+	if (IS_ERR(auth->aes)) {
+		rc = PTR_ERR(auth->aes);
+		dev_err(&chip->dev, "TPM: error getting cfb(aes): %d\n", rc);
+	}
+ out:
+	if (rc)
+		kfree(auth);
+	else
+		*authp = auth;
+
+	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;
+	SHASH_DESC_ON_STACK(desc, sha256_hash);
+
+	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 */
+	desc->tfm = sha256_hash;
+	put_unaligned_be16(TPM_ALG_SHA256, chip->tpmkeyname);
+	crypto_shash_init(desc);
+	crypto_shash_update(desc, resp, len);
+	crypto_shash_final(desc, 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) {
+		printk("TPM 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);
+	/* simple authorization for empty auth */
+	tpm2_buf_append_auth(&buf, TPM2_RS_PW, NULL, 0, 0, NULL, 0);
+	/* 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;
+}
+
+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;
+
+	sha256_hash = crypto_alloc_shash("sha256", 0, 0);
+	if (!sha256_hash) {
+		dev_err(&chip->dev, "TPM: failed to allocate hash\n");
+		return -ENOMEM;
+	}
+
+	rc = tpm2_create_null_primary(chip);
+	if (rc)
+		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
+	return rc;
+}
+EXPORT_SYMBOL(tpm2_sessions_init);
diff --git a/drivers/char/tpm/tpm2-sessions.h b/drivers/char/tpm/tpm2-sessions.h
new file mode 100644
index 000000000000..ec245731edaf
--- /dev/null
+++ b/drivers/char/tpm/tpm2-sessions.h
@@ -0,0 +1,137 @@
+/*
+ * Defines for TPM2 authentications
+ */
+
+#ifndef _TPM2_SESSIONS_H
+#define _TPM2_SESSIONS_H
+
+#include "tpm.h"
+
+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),
+};
+
+enum tpm2_session_types {
+	TPM2_SE_HMAC	= 0x00,
+	TPM2_SE_POLICY	= 0x01,
+	TPM2_SE_TRIAL	= 0x02,
+};
+
+struct tpm2_auth;
+
+void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
+			  const u8 *nonce, u16 nonce_len,
+			  u8 attributes,
+			  const u8 *hmac, u16 hmac_len);
+
+#ifdef CONFIG_TPM_BUS_SECURITY
+
+int tpm2_start_auth_session(struct tpm_chip *chip, struct tpm2_auth **authp);
+void tpm_buf_append_name(struct tpm_buf *buf, struct tpm2_auth *auth,
+			 u32 handle, u8 *name);
+void tpm_buf_append_hmac_session(struct tpm_buf *buf, struct tpm2_auth *auth,
+				 u8 attributes, u8 *passphrase,
+				 int passphraselen);
+static inline void tpm_buf_append_hmac_session_opt(struct tpm_buf *buf,
+						   struct tpm2_auth *auth,
+						   u8 attributes,
+						   u8 *passphrase,
+						   int passphraselen)
+{
+	tpm_buf_append_hmac_session(buf, auth, attributes, passphrase,
+				    passphraselen);
+}
+void tpm_buf_fill_hmac_session(struct tpm_buf *buf, struct tpm2_auth *auth);
+int tpm_buf_check_hmac_response(struct tpm_buf *buf, struct tpm2_auth *auth,
+				int rc);
+void tpm2_end_auth_session(struct tpm2_auth *auth);
+#else
+#include <asm/unaligned.h>
+
+static inline int tpm2_start_auth_session(struct tpm_chip *chip,
+					  struct tpm2_auth **authp)
+{
+	return 0;
+}
+static inline void tpm2_end_auth_session(struct tpm2_auth *auth)
+{
+}
+static inline void tpm_buf_append_name(struct tpm_buf *buf,
+				       struct tpm2_auth *auth,
+				       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_buf *buf,
+					       struct tpm2_auth *auth,
+					       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_buf *buf,
+						   struct tpm2_auth *auth,
+						   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_buf *buf,
+					     struct tpm2_auth *auth)
+{
+}
+static inline int tpm_buf_check_hmac_response(struct tpm_buf *buf,
+					      struct tpm2_auth *auth,
+					      int rc)
+{
+	return rc;
+}
+#endif	/* CONFIG_TPM_BUS_SECURITY */
+
+#endif
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 53c0ea9ec9df..949e7fb725a8 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -33,14 +33,23 @@ struct trusted_key_options;
 enum tpm_algorithms {
 	TPM_ALG_ERROR		= 0x0000,
 	TPM_ALG_SHA1		= 0x0004,
+	TPM_ALG_AES		= 0x0006,
 	TPM_ALG_KEYEDHASH	= 0x0008,
 	TPM_ALG_SHA256		= 0x000B,
 	TPM_ALG_SHA384		= 0x000C,
 	TPM_ALG_SHA512		= 0x000D,
 	TPM_ALG_NULL		= 0x0010,
 	TPM_ALG_SM3_256		= 0x0012,
+	TPM_ALG_ECC		= 0x0023,
+	TPM_ALG_CFB		= 0x0043,
 };
 
+enum tpm2_curves {
+	TPM2_ECC_NONE		= 0x0000,
+	TPM2_ECC_NIST_P256	= 0x0003,
+};
+
+
 struct tpm_digest {
 	u16 alg_id;
 	u8 digest[TPM_MAX_DIGEST_SIZE];
@@ -105,6 +114,20 @@ 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 2048
+
 struct tpm_chip {
 	struct device dev;
 	struct device devs;
@@ -159,6 +182,12 @@ struct tpm_chip {
 
 	/* active locality */
 	int locality;
+
+	/* 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];
 };
 
 #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 06/12] tpm-buf: add tpm_buf_parameters()
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (4 preceding siblings ...)
  2019-09-09 12:20 ` [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling James Bottomley
@ 2019-09-09 12:21 ` James Bottomley
  2019-09-09 12:22 ` [PATCH v6 07/12] tpm2: add hmac checks to tpm2_pcr_extend() James Bottomley
                   ` (6 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:21 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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 ++++++++++
 drivers/char/tpm/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 f56350123a08..a5d793d8180d 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -190,3 +190,13 @@ 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/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index ebead8e4c3fe..c88eee6376e4 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -311,6 +311,8 @@ 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);
+
 /* opaque structure, holds auth session parameters like the session key */
 struct tpm2_auth;
 
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 07/12] tpm2: add hmac checks to tpm2_pcr_extend()
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (5 preceding siblings ...)
  2019-09-09 12:21 ` [PATCH v6 06/12] tpm-buf: add tpm_buf_parameters() James Bottomley
@ 2019-09-09 12:22 ` James Bottomley
  2019-09-09 12:22 ` [PATCH v6 08/12] tpm2: add session encryption protection to tpm2_get_random() James Bottomley
                   ` (5 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:22 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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>

---

v3: add error handling to sessions
---
 drivers/char/tpm/tpm2-cmd.c | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index d120b0a260eb..0012657d3617 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -223,13 +223,6 @@ 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
  *
@@ -243,24 +236,23 @@ 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;
+	struct tpm2_auth *auth;
 	int rc;
 	int i;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
+	rc = tpm2_start_auth_session(chip, &auth);
 	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(auth);
+		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(&buf, auth, pcr_idx, NULL);
+	tpm_buf_append_hmac_session(&buf, auth, 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++) {
@@ -269,7 +261,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 			       chip->allocated_banks[i].digest_size);
 	}
 
+	tpm_buf_fill_hmac_session(&buf, auth);
 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
 
 	tpm_buf_destroy(&buf);
 
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 08/12] tpm2: add session encryption protection to tpm2_get_random()
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (6 preceding siblings ...)
  2019-09-09 12:22 ` [PATCH v6 07/12] tpm2: add hmac checks to tpm2_pcr_extend() James Bottomley
@ 2019-09-09 12:22 ` James Bottomley
  2019-09-09 12:23 ` [PATCH v6 09/12] trusted keys: Add session encryption protection to the seal/unseal path James Bottomley
                   ` (4 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:22 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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>

---

v3: add error handling to sessions and redo to be outside loop
---
 drivers/char/tpm/tpm2-cmd.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 0012657d3617..572d05966b77 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -296,29 +296,40 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	int total = 0;
 	int retries = 5;
 	u8 *dest_ptr = dest;
+	struct tpm2_auth *auth;
 
 	if (!num_bytes || max > TPM_MAX_RNG_DATA)
 		return -EINVAL;
 
-	err = tpm_buf_init(&buf, 0, 0);
+	err = tpm2_start_auth_session(chip, &auth);
 	if (err)
 		return err;
 
+	err = tpm_buf_init(&buf, 0, 0);
+	if (err) {
+		tpm2_end_auth_session(auth);
+		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(&buf, auth, TPM2_SA_ENCRYPT
+						| TPM2_SA_CONTINUE_SESSION,
+						NULL, 0);
 		tpm_buf_append_u16(&buf, num_bytes);
+		tpm_buf_fill_hmac_session(&buf, auth);
 		err = tpm_transmit_cmd(chip, &buf,
 				       offsetof(struct tpm2_get_random_out,
 						buffer),
 				       "attempting get random");
+		err = tpm_buf_check_hmac_response(&buf, auth, 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 +
@@ -335,6 +346,8 @@ 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(auth);
+
 	return total ? total : -EIO;
 out:
 	tpm_buf_destroy(&buf);
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 09/12] trusted keys: Add session encryption protection to the seal/unseal path
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (7 preceding siblings ...)
  2019-09-09 12:22 ` [PATCH v6 08/12] tpm2: add session encryption protection to tpm2_get_random() James Bottomley
@ 2019-09-09 12:23 ` James Bottomley
  2019-09-09 12:24 ` [PATCH v6 10/12] tpm: add the null key name as a tpm2 sysfs variable James Bottomley
                   ` (3 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:23 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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>
---
 drivers/char/tpm/tpm2-cmd.c | 124 ++++++++++++++++++++++++++++++--------------
 1 file changed, 85 insertions(+), 39 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 572d05966b77..2c798f18282f 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -422,7 +422,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 {
 	unsigned int blob_len;
 	struct tpm_buf buf;
+	struct tpm_buf t2b;
 	u32 hash;
+	struct tpm2_auth *auth;
 	int i;
 	int rc;
 
@@ -436,45 +438,56 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (i == ARRAY_SIZE(tpm2_hash_map))
 		return -EINVAL;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
+	rc = tpm2_start_auth_session(chip, &auth);
 	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_CREATE);
+	if (rc) {
+		tpm2_end_auth_session(auth);
+		return rc;
+	}
+
+	rc = tpm_buf_init_2b(&t2b);
+	if (rc) {
+		tpm_buf_destroy(&buf);
+		tpm2_end_auth_session(auth);
+		return rc;
+	}
 
+	tpm_buf_append_name(&buf, auth, options->keyhandle, NULL);
+	tpm_buf_append_hmac_session(&buf, auth, TPM2_SA_DECRYPT,
+				    options->keyauth, TPM_DIGEST_SIZE);
 	/* sensitive */
-	tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len + 1);
+	tpm_buf_append_u16(&t2b, TPM_DIGEST_SIZE);
+	tpm_buf_append(&t2b, options->blobauth, TPM_DIGEST_SIZE);
+	tpm_buf_append_u16(&t2b, payload->key_len + 1);
+	tpm_buf_append(&t2b, payload->key, payload->key_len);
+	tpm_buf_append_u8(&t2b, payload->migratable);
 
-	tpm_buf_append_u16(&buf, TPM_DIGEST_SIZE);
-	tpm_buf_append(&buf, options->blobauth, TPM_DIGEST_SIZE);
-	tpm_buf_append_u16(&buf, payload->key_len + 1);
-	tpm_buf_append(&buf, payload->key, payload->key_len);
-	tpm_buf_append_u8(&buf, payload->migratable);
+	tpm_buf_append_2b(&buf, &t2b);
 
 	/* public */
-	tpm_buf_append_u16(&buf, 14 + options->policydigest_len);
-	tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH);
-	tpm_buf_append_u16(&buf, hash);
+	tpm_buf_append_u16(&t2b, TPM_ALG_KEYEDHASH);
+	tpm_buf_append_u16(&t2b, hash);
 
 	/* policy */
 	if (options->policydigest_len) {
-		tpm_buf_append_u32(&buf, 0);
-		tpm_buf_append_u16(&buf, options->policydigest_len);
-		tpm_buf_append(&buf, options->policydigest,
+		tpm_buf_append_u32(&t2b, 0);
+		tpm_buf_append_u16(&t2b, options->policydigest_len);
+		tpm_buf_append(&t2b, options->policydigest,
 			       options->policydigest_len);
 	} else {
-		tpm_buf_append_u32(&buf, TPM2_OA_USER_WITH_AUTH);
-		tpm_buf_append_u16(&buf, 0);
+		tpm_buf_append_u32(&t2b, TPM2_OA_USER_WITH_AUTH);
+		tpm_buf_append_u16(&t2b, 0);
 	}
 
 	/* public parameters */
-	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
-	tpm_buf_append_u16(&buf, 0);
+	tpm_buf_append_u16(&t2b, TPM_ALG_NULL);
+	/* unique (zero) */
+	tpm_buf_append_u16(&t2b, 0);
+
+	tpm_buf_append_2b(&buf, &t2b);
 
 	/* outside info */
 	tpm_buf_append_u16(&buf, 0);
@@ -487,7 +500,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		goto out;
 	}
 
+	tpm_buf_fill_hmac_session(&buf, auth);
 	rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
 	if (rc)
 		goto out;
 
@@ -505,6 +520,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	payload->blob_len = blob_len;
 
 out:
+	tpm_buf_destroy(&t2b);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0) {
@@ -536,6 +552,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			 u32 *blob_handle)
 {
 	struct tpm_buf buf;
+	struct tpm2_auth *auth;
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
@@ -550,17 +567,18 @@ 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, &auth);
 	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(auth);
+		return rc;
+	}
 
+	tpm_buf_append_name(&buf, auth, options->keyhandle, NULL);
+	tpm_buf_append_hmac_session(&buf, auth, 0, options->keyauth, TPM_DIGEST_SIZE);
 	tpm_buf_append(&buf, payload->blob, blob_len);
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
@@ -568,7 +586,9 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 		goto out;
 	}
 
+	tpm_buf_fill_hmac_session(&buf, auth);
 	rc = tpm_transmit_cmd(chip, &buf, 4, "loading blob");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
 	if (!rc)
 		*blob_handle = be32_to_cpup(
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
@@ -600,24 +620,50 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 			   u32 blob_handle)
 {
 	struct tpm_buf buf;
+	struct tpm2_auth *auth;
 	u16 data_len;
 	u8 *data;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	rc = tpm2_start_auth_session(chip, &auth);
 	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 */,
-			     TPM_DIGEST_SIZE);
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	if (rc) {
+		tpm2_end_auth_session(auth);
+		return rc;
+	}
+
+	tpm_buf_append_name(&buf, auth, blob_handle, NULL);
+
+	if (!options->policyhandle) {
+		tpm_buf_append_hmac_session(&buf, auth, TPM2_SA_ENCRYPT,
+					    options->blobauth, TPM_DIGEST_SIZE);
+	} else {
+		/*
+		 * FIXME: the policy can't be used for HMAC protection
+		 * of the authorization because it must be generated
+		 * with the initial nonces which isn't passed in, so
+		 * append a second encryption session to at least HMAC
+		 * protect the command and encrypt the sealed blob on
+		 * return.
+		 *
+		 * Note: this also means the caller either has to use
+		 * an empty password or compute the password HMAC
+		 * based on the policy nonces and place it in blobauth
+		 */
+		tpm2_buf_append_auth(&buf, options->policyhandle,
+				     NULL /* nonce */, 0, 0,
+				     options->blobauth /* hmac */,
+				     TPM_DIGEST_SIZE);
+		tpm_buf_append_hmac_session_opt(&buf, auth, TPM2_SA_ENCRYPT,
+						NULL, 0);
+	}
 
+	tpm_buf_fill_hmac_session(&buf, auth);
 	rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
 	if (rc > 0)
 		rc = -EPERM;
 
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 10/12] tpm: add the null key name as a tpm2 sysfs variable
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (8 preceding siblings ...)
  2019-09-09 12:23 ` [PATCH v6 09/12] trusted keys: Add session encryption protection to the seal/unseal path James Bottomley
@ 2019-09-09 12:24 ` James Bottomley
  2019-09-09 12:25 ` [PATCH v6 11/12] Documentation: add tpm-security.rst James Bottomley
                   ` (2 subsequent siblings)
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:24 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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 | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index d9caedda075b..07aa8f427b96 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -309,6 +309,19 @@ static ssize_t timeouts_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(timeouts);
 
+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);
+
 static struct attribute *tpm_dev_attrs[] = {
 	&dev_attr_pubek.attr,
 	&dev_attr_pcrs.attr,
@@ -323,17 +336,29 @@ static struct attribute *tpm_dev_attrs[] = {
 	NULL,
 };
 
+static struct attribute *tpm2_dev_attrs[] = {
+	&dev_attr_null_name.attr,
+	NULL,
+};
+
 static const struct attribute_group tpm_dev_group = {
 	.attrs = tpm_dev_attrs,
 };
 
+static const struct attribute_group tpm2_dev_group = {
+	.attrs = tpm2_dev_attrs,
+};
+
 void tpm_sysfs_add_device(struct tpm_chip *chip)
 {
 	/* XXX: If you wish to remove this restriction, you must first update
 	 * tpm_sysfs to explicitly lock chip->ops.
 	 */
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+		WARN_ON(chip->groups_cnt != 0);
+		chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
 		return;
+	}
 
 	/* The sysfs routines rely on an implicit tpm_try_get_ops, device_del
 	 * is called before ops is null'd and the sysfs core synchronizes this
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 11/12] Documentation: add tpm-security.rst
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (9 preceding siblings ...)
  2019-09-09 12:24 ` [PATCH v6 10/12] tpm: add the null key name as a tpm2 sysfs variable James Bottomley
@ 2019-09-09 12:25 ` James Bottomley
  2019-09-09 12:26 ` [PATCH v6 12/12] tpm2-sessions: NOT FOR COMMITTING add sessions testing James Bottomley
  2019-09-10 16:21 ` [PATCH v6 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:25 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

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>

---

v6: replace kernel space with null seed context save
---
 Documentation/security/tpm/tpm-security.rst | 204 ++++++++++++++++++++++++++++
 1 file changed, 204 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..3411030505a1
--- /dev/null
+++ b/Documentation/security/tpm/tpm-security.rst
@@ -0,0 +1,204 @@
+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.  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 https://www.nccgroup.trust/us/our-research/tpm-genie/ which
+is a simple external device that can be installed in a couple of
+seconds on any system or laptop.  However, 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, 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 certified 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, the generated EK primary key may now be used to run an
+attestation on the null seed.  The specific problem here is that the
+EK primary is not a signing key so cannot on its own be used to sign
+the key certification, hence the complex process below.
+
+Note: 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.
+
+.. _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/
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* [PATCH v6 12/12] tpm2-sessions: NOT FOR COMMITTING add sessions testing
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (10 preceding siblings ...)
  2019-09-09 12:25 ` [PATCH v6 11/12] Documentation: add tpm-security.rst James Bottomley
@ 2019-09-09 12:26 ` James Bottomley
  2019-09-10 16:21 ` [PATCH v6 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
  12 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-09 12:26 UTC (permalink / raw)
  To: linux-integrity; +Cc: linux-crypto, linux-security-module, Jarkko Sakkinen

This runs through a preset sequence using sessions to demonstrate that
the session handling code functions.  It does both HMAC, encryption
and decryption by testing an encrypted sealing operation with
authority and proving that the same sealed data comes back again via
an HMAC and response encryption.  It also does policy unsealing which
mimics the more complex of the trusted key scenarios.

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

---
v3: add policy unseal testing with two sessions
v6: move to new null seed framework
---
 drivers/char/tpm/Makefile             |   2 +
 drivers/char/tpm/tpm-chip.c           |   1 +
 drivers/char/tpm/tpm.h                |   1 +
 drivers/char/tpm/tpm2-cmd.c           |   7 +
 drivers/char/tpm/tpm2-sessions-test.c | 795 ++++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm2-sessions.c      |   1 +
 drivers/char/tpm/tpm2-sessions.h      |   3 +-
 7 files changed, 809 insertions(+), 1 deletion(-)
 create mode 100644 drivers/char/tpm/tpm2-sessions-test.c

diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 8f9e58317048..f6577c9e3138 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -35,3 +35,5 @@ obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
 obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
 obj-$(CONFIG_TCG_CRB) += tpm_crb.o
 obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
+
+obj-m +=  tpm2-sessions-test.o
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 4838c6a9f0f2..5dda37047a71 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -252,6 +252,7 @@ struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip)
 		return NULL;
 	return chip;
 }
+EXPORT_SYMBOL(tpm_find_get_ops);
 
 /**
  * tpm_dev_release() - free chip memory and the device number
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index c88eee6376e4..06f63874e833 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -117,6 +117,7 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_POLICY_COMMAND_CODE	= 0x16c,
 	TPM2_CC_READ_PUBLIC		= 0x0173,
 	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 2c798f18282f..d4bbe19170d1 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -222,6 +222,7 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 	tpm_buf_destroy(&buf);
 	return rc;
 }
+EXPORT_SYMBOL_GPL(tpm2_pcr_read);
 
 /**
  * tpm2_pcr_extend() - extend a PCR value
@@ -269,6 +270,7 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(tpm2_pcr_extend);
 
 struct tpm2_get_random_out {
 	__be16 size;
@@ -353,6 +355,7 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	tpm_buf_destroy(&buf);
 	return err;
 }
+EXPORT_SYMBOL_GPL(tpm2_get_random);
 
 /**
  * tpm2_flush_context() - execute a TPM2_FlushContext command
@@ -376,6 +379,7 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 	tpm_transmit_cmd(chip, &buf, 0, "flushing context");
 	tpm_buf_destroy(&buf);
 }
+EXPORT_SYMBOL_GPL(tpm2_flush_context);
 
 /**
  * tpm_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer.
@@ -406,6 +410,7 @@ void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
 	if (hmac && hmac_len)
 		tpm_buf_append(buf, hmac, hmac_len);
 }
+EXPORT_SYMBOL_GPL(tpm2_buf_append_auth);
 
 /**
  * tpm2_seal_trusted() - seal the payload of a trusted key
@@ -532,6 +537,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(tpm2_seal_trusted);
 
 /**
  * tpm2_load_cmd() - execute a TPM2_Load command
@@ -715,6 +721,7 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 	tpm2_flush_context(chip, blob_handle);
 	return rc;
 }
+EXPORT_SYMBOL_GPL(tpm2_unseal_trusted);
 
 struct tpm2_get_cap_out {
 	u8 more_data;
diff --git a/drivers/char/tpm/tpm2-sessions-test.c b/drivers/char/tpm/tpm2-sessions-test.c
new file mode 100644
index 000000000000..834811ab3466
--- /dev/null
+++ b/drivers/char/tpm/tpm2-sessions-test.c
@@ -0,0 +1,795 @@
+/* run a set of tests of the sessions code */
+#include "tpm.h"
+#include "tpm2-sessions.h"
+
+#include <linux/random.h>
+
+#include <asm/unaligned.h>
+
+#include <crypto/aes.h>
+#include <crypto/hash.h>
+
+#include <keys/trusted-type.h>
+
+/* simple policy: command code must be TPM2_CC_UNSEAL */
+static u8 policy[] = {
+	0xe6, 0x13, 0x13, 0x70, 0x76, 0x52, 0x4b, 0xde,
+	0x48, 0x75, 0x33, 0x86, 0x58, 0x84, 0xe9, 0x73,
+	0x2e, 0xbe, 0xe3, 0xaa, 0xcb, 0x09, 0x5d, 0x94,
+	0xa6, 0xde, 0x49, 0x2e, 0xc0, 0x6c, 0x46, 0xfa,
+};
+
+static struct crypto_shash *sha256_hash;
+
+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;
+	SHASH_DESC_ON_STACK(desc, sha256_hash);
+
+	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 */
+	desc->tfm = sha256_hash;
+	put_unaligned_be16(TPM_ALG_SHA256, chip->tpmkeyname);
+	crypto_shash_init(desc);
+	crypto_shash_update(desc, resp, len);
+	crypto_shash_final(desc, 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_KEYSIZE_128 * 8)
+		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) {
+		printk("TPM 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);
+	/* simple authorization for empty auth */
+	tpm2_buf_append_auth(&buf, TPM2_RS_PW, NULL, 0, 0, NULL, 0);
+	/* 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 u32 get_policy(struct tpm_chip *chip)
+{
+	struct tpm_buf buf;
+	u8 nonce[SHA256_DIGEST_SIZE];
+	u32 h;
+	int rc;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
+	if (rc)
+		return 0;
+
+	/* salt key */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* bind key */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* zero nonce */
+	memset(nonce, 0, sizeof(nonce));
+	tpm_buf_append_u16(&buf, sizeof(nonce));
+	tpm_buf_append(&buf, nonce, sizeof(nonce));
+	/* encrypted salt (empty) */
+	tpm_buf_append_u16(&buf, 0);
+	/* session type (HMAC, audit or policy) */
+	tpm_buf_append_u8(&buf, TPM2_SE_POLICY);
+	/* symmetric encryption parameters */
+	/* symmetric algorithm */
+	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+
+	/* hash algorithm for session */
+	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
+
+	rc = tpm_transmit_cmd(chip, &buf, 0, "start policy session");
+
+	h = get_unaligned_be32(&buf.data[TPM_HEADER_SIZE]);
+
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS,
+		      TPM2_CC_POLICY_COMMAND_CODE);
+	tpm_buf_append_u32(&buf, h);
+	tpm_buf_append_u32(&buf, TPM2_CC_UNSEAL);
+
+	rc = tpm_transmit_cmd(chip, &buf, 0, "start policy session");
+
+	tpm_buf_destroy(&buf);
+
+	dev_info(&chip->dev, "got policy session %08x\n", h);
+
+	return h;
+}
+
+int tpm2_sessions_test(void)
+{
+	struct tpm2_auth *auth;
+	struct tpm_buf buf, b1;
+	struct tpm_buf t2b;
+	struct tpm_chip *chip;
+	int rc;
+	char payload[MIN_KEY_SIZE+3];
+	char *password = "Passw0Rd";
+	const u8 *p;
+	u32 h, ps;
+	u8 name[34];
+	u16 len;
+	int ret = -EINVAL;
+	u32 nullkey = 0;
+	struct trusted_key_payload tkp;
+	struct trusted_key_options tko;
+	struct tpm_digest digest, extend[3];
+	u16 digest_len;
+	int i;
+	SHASH_DESC_ON_STACK(desc, sha256_hash);
+
+	chip = tpm_find_get_ops(NULL);
+	if (!chip)
+		return -ENODEV;
+
+	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
+		return -ENODEV;
+
+	sha256_hash = crypto_alloc_shash("sha256", 0, 0);
+
+	/* precursor: get a session */
+	rc = tpm2_start_auth_session(chip, &auth);
+
+	dev_info(&chip->dev, "TPM: start auth session returned %d\n", rc);
+
+	if (rc)
+		return -ENODEV;
+
+	/* first test: get random bytes from TPM */
+	dev_info(&chip->dev, "test 1: TPM random number generator\n");
+	rc = tpm2_get_random(chip, payload, sizeof(payload));
+	if (rc != sizeof(payload)) {
+		dev_err(&chip->dev, "tpm2_get_random failed: %d\n", rc);
+		goto out;
+	}
+	dev_info(&chip->dev, "test 1: PASS\n");
+
+	/*
+	 * second test, seal random data protecting sensitive by
+	 * encryption and also doing response encryption (not
+	 * necessary) The encrypted payload has two components: an
+	 * authorization password which must be presented on useal and
+	 * the actual data (the random payload)
+	 */
+	dev_info(&chip->dev, "test2: seal data and check tpm unsealing functions\n");
+	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &nullkey);
+
+	if (rc != TPM2_RC_SUCCESS) {
+		dev_err(&chip->dev, "tpm2_create_primary failed: %d\n", rc);
+		goto out;
+	}
+
+	dev_info(&chip->dev, "NULL KEY at %08x\n", nullkey);
+
+	tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
+	tpm_buf_append_name(&buf, auth, nullkey, chip->tpmkeyname);
+	/* close the session here, get a new one for next seal op */
+	tpm_buf_append_hmac_session(&buf, auth, TPM2_SA_DECRYPT
+				    | TPM2_SA_ENCRYPT, NULL, 0);
+	/* sensitive */
+	tpm_buf_init_2b(&t2b);
+	/* the authorization */
+	tpm_buf_append_u16(&t2b, strlen(password));
+	tpm_buf_append(&t2b, password, strlen(password));
+	/* the payload */
+	tpm_buf_append_u16(&t2b, sizeof(payload) + 1);
+	tpm_buf_append(&t2b, payload, sizeof(payload));
+	/* the migrateable flag used by the TPM sealing functions */
+	tpm_buf_append_u8(&t2b, 0);
+	tpm_buf_append_2b(&buf, &t2b);
+	/* the public */
+	/* type */
+	tpm_buf_append_u16(&t2b, TPM_ALG_KEYEDHASH);
+	/* name hash */
+	tpm_buf_append_u16(&t2b, TPM_ALG_SHA256);
+	/* object properties */
+	tpm_buf_append_u32(&t2b, TPM2_OA_USER_WITH_AUTH | TPM2_OA_NO_DA);
+	/* auth policy (empty) */
+	tpm_buf_append_u16(&t2b, 0);
+	/* keyed hash parameters (we're null for a non-HMAC data blob) */
+	tpm_buf_append_u16(&t2b, TPM_ALG_NULL);
+	/* unique */
+	tpm_buf_append_u16(&t2b, 0);
+	tpm_buf_append_2b(&buf, &t2b);
+	/* outside info (also empty) */
+	tpm_buf_append_u16(&buf, 0);
+	/* creation PCR (empty) */
+	tpm_buf_append_u32(&buf, 0);
+	tpm_buf_fill_hmac_session(&buf, auth);
+	rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
+	dev_info(&chip->dev, "TPM: sealing response returned %d\n", rc);
+	if (rc)
+		goto out;
+
+	/*
+	 * now load the sealed object (we need the pub and priv parts
+	 * returned from prior command
+	 */
+	memset(&tkp, 0, sizeof(tkp));
+	memset(&tko, 0, sizeof(tko));
+
+	p = &buf.data[TPM_HEADER_SIZE];
+
+	tkp.blob_len = tpm_get_inc_u32(&p);
+	memcpy(tkp.blob, p, tkp.blob_len);
+	tko.keyhandle = nullkey;
+	strcpy(tko.blobauth, password);
+
+	rc = tpm2_unseal_trusted(chip, &tkp, &tko);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_unseal_trusted[password] returned %d\n", rc);
+		goto out;
+	}
+
+	if (tkp.key_len != sizeof(payload)) {
+		dev_err(&chip->dev, "tpm2_unseal_trusted[password] wrong unseal payload size %d != %ld",
+			tkp.key_len, sizeof(payload));
+		goto out;
+	}
+	if (memcmp(payload, tkp.key, tkp.key_len) != 0) {
+		dev_err(&chip->dev, "tpm2_unseal_trusted[password] Payload DID NOT compare correctly\n");
+		goto out;
+	}
+	dev_info(&chip->dev, "tpm2_unseal_trusted[password] returned correct data\n"
+		 "test2: PASS\n");
+
+	/*
+	 * third test, seal random data protecting sensitive by
+	 * encryption and also doing response encryption (not
+	 * necessary) The encrypted payload has two components: an
+	 * authorization password which must be presented on useal and
+	 * the actual data (the random payload)
+	 *
+	 * For this test use a policy to release the data testing that
+	 * we can have two sessions
+	 */
+
+	dev_info(&chip->dev, "test 3: seal to policy and test unseal\n");
+	rc = tpm2_get_random(chip, payload, sizeof(payload));
+	if (rc != sizeof(payload)) {
+		dev_err(&chip->dev, "tpm2_get_random failed: %d\n", rc);
+		goto out;
+	}
+
+	/* auth session should be closed, so get a new one */
+	rc = tpm2_start_auth_session(chip, &auth);
+	if (rc) {
+		dev_err(&chip->dev, "new auth session failed: %d\n", rc);
+		goto out;
+	}
+
+	tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
+	tpm_buf_append_name(&buf, auth, nullkey, chip->tpmkeyname);
+	tpm_buf_append_hmac_session(&buf, auth, TPM2_SA_DECRYPT
+				    | TPM2_SA_ENCRYPT
+				    | TPM2_SA_CONTINUE_SESSION, NULL, 0);
+	/* sensitive */
+	tpm_buf_init_2b(&t2b);
+	/* the authorization */
+	tpm_buf_append_u16(&t2b, 0);
+	/* the payload */
+	tpm_buf_append_u16(&t2b, sizeof(payload) + 1);
+	tpm_buf_append(&t2b, payload, sizeof(payload));
+	/* extra byte for migratability flag */
+	tpm_buf_append_u8(&t2b, 0);
+	tpm_buf_append_2b(&buf, &t2b);
+	/* the public */
+	/* type */
+	tpm_buf_append_u16(&t2b, TPM_ALG_KEYEDHASH);
+	/* name hash */
+	tpm_buf_append_u16(&t2b, TPM_ALG_SHA256);
+	/* object properties */
+	tpm_buf_append_u32(&t2b, TPM2_OA_NO_DA);
+	/* auth policy (specific to command code) */
+	tpm_buf_append_u16(&t2b, sizeof(policy));
+	tpm_buf_append(&t2b, policy, sizeof(policy));
+	/* keyed hash parameters (we're null for a non-HMAC data blob) */
+	tpm_buf_append_u16(&t2b, TPM_ALG_NULL);
+	/* unique */
+	tpm_buf_append_u16(&t2b, 0);
+	tpm_buf_append_2b(&buf, &t2b);
+	/* outside info (also empty) */
+	tpm_buf_append_u16(&buf, 0);
+	/* creation PCR (empty) */
+	tpm_buf_append_u32(&buf, 0);
+	tpm_buf_fill_hmac_session(&buf, auth);
+	rc = tpm_transmit_cmd(chip, &buf, 4, "policy sealing data");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
+	dev_info(&chip->dev, "policy sealing response returned %d\n", rc);
+	if (rc)
+		goto out;
+
+	/*
+	 * now load the sealed object (we need the pub and priv parts
+	 * returned from prior command
+	 */
+	memset(&tkp, 0, sizeof(tkp));
+	memset(&tko, 0, sizeof(tko));
+
+	p = &buf.data[TPM_HEADER_SIZE];
+
+	/* now get a policy session */
+	ps = get_policy(chip);
+
+	tkp.blob_len = tpm_get_inc_u32(&p);
+	memcpy(tkp.blob, p, tkp.blob_len);
+	tko.keyhandle = nullkey;
+	tko.policyhandle = ps;
+
+	rc = tpm2_unseal_trusted(chip, &tkp, &tko);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_unseal_trusted[policy] returned %d\n", rc);
+		tpm2_flush_context(chip, ps);
+		goto out;
+	}
+
+	if (tkp.key_len != sizeof(payload)) {
+		dev_err(&chip->dev, "tpm2_unseal_trusted[policy] wrong unseal payload size %d != %ld",
+			tkp.key_len, sizeof(payload));
+		goto out;
+	}
+	if (memcmp(payload, tkp.key, tkp.key_len) != 0) {
+		dev_err(&chip->dev, "tpm2_unseal_trusted[policy] Payload DID NOT compare correctly\n");
+		goto out;
+	}
+	dev_info(&chip->dev, "tpm2_unseal_trusted[policy] returned correct data\n"
+		 "test3: PASS\n");
+
+	/*
+	 * test4: get the TPM routines to seal to a password and then
+	 * do a manual unseal
+	 */
+
+	dev_info(&chip->dev, "test4: seal using tpm2-cmd[password] and unseal manually\n");
+
+	memset(&tkp, 0, sizeof(tkp));
+	memset(&tko, 0, sizeof(tko));
+
+	tko.keyhandle = nullkey;
+	tko.hash = HASH_ALGO_SHA256;
+	tkp.key_len = sizeof(payload);
+	memcpy(tkp.key, payload, tkp.key_len);
+	strcpy(tko.blobauth, password);
+
+	rc = tpm2_seal_trusted(chip, &tkp, &tko);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_seal_trusted returned error: %d\n ", rc);
+		goto out;
+	}
+
+	/*
+	 * now load the sealed object (we need the pub and priv parts
+	 * returned from prior command.  The blob from
+	 * tpm2_seal_trusted is the entire return from the create, so
+	 * only append the private and public parts
+	 */
+	p = tkp.blob;
+	/* private len */
+	len = tpm_get_inc_u16(&p);
+	p += len;
+	/* add public len */
+	len += tpm_get_inc_u16(&p);
+	/* add 4 for the two length values */
+	len += 4;
+
+	tpm_buf_init(&b1, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
+	/* parent */
+	tpm_buf_append_name(&b1, auth, nullkey, chip->tpmkeyname);
+	tpm_buf_append_hmac_session(&b1, auth, TPM2_SA_CONTINUE_SESSION,
+				    NULL, 0);
+
+	tpm_buf_append(&b1, tkp.blob, len);
+
+	tpm_buf_fill_hmac_session(&b1, auth);
+	rc = tpm_transmit_cmd(chip, &b1, 4, "loading seal");
+	rc = tpm_buf_check_hmac_response(&b1, auth, rc);
+	dev_info(&chip->dev, "TPM: load response returned %d\n", rc);
+	if (rc)
+		goto out;
+	p = &b1.data[TPM_HEADER_SIZE];
+	h = tpm_get_inc_u32(&p);
+	dev_info(&chip->dev, "sealed data loaded at %08x\n", h);
+	/* skip over parameter size */
+	p += 4;
+	len = tpm_get_inc_u16(&p);
+	if (len != sizeof(name)) {
+		dev_err(&chip->dev, "Wrong name size %d\n", len);
+		goto out;
+	}
+	memcpy(name, p, len);
+	tpm_buf_destroy(&b1);
+	tpm_buf_destroy(&buf);
+
+	/*
+	 * now unseal the data using the authority in a HMAC and
+	 * protecting the returned unseal by encryption
+	 */
+	tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	tpm_buf_append_name(&buf, auth, h, name);
+	tpm_buf_append_hmac_session(&buf, auth,
+				    TPM2_SA_ENCRYPT | TPM2_SA_CONTINUE_SESSION,
+				    password, strlen(password));
+	tpm_buf_fill_hmac_session(&buf, auth);
+	rc = tpm_transmit_cmd(chip, &buf, 4, "unseal");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
+	tpm2_flush_context(chip, h);
+	dev_info(&chip->dev, "unseal returns %d\n", rc);
+	if (rc)
+		goto out;
+	p = &buf.data[TPM_HEADER_SIZE + 4];
+	len = tpm_get_inc_u16(&p);
+	if (len != sizeof(payload) + 1) {
+		dev_err(&chip->dev, "wrong unseal payload size %d != %ld",
+			len, sizeof(payload) + 1);
+		goto out;
+	}
+	if (memcmp(payload, p, sizeof(payload)) != 0) {
+		dev_err(&chip->dev, "Payload DID NOT compare correctly\n");
+		goto out;
+	}
+
+	dev_info(&chip->dev, "test4: PASS\n");
+
+	/*
+	 * test5: get the TPM routines to seal to a policy and then
+	 * do a manual unseal
+	 */
+
+	dev_info(&chip->dev, "test5: seal using tpm2-cmd[policy] and unseal manually\n");
+
+	memset(&tkp, 0, sizeof(tkp));
+	memset(&tko, 0, sizeof(tko));
+
+	tko.keyhandle = nullkey;
+	tko.hash = HASH_ALGO_SHA256;
+	tkp.key_len = sizeof(payload);
+	memcpy(tkp.key, payload, tkp.key_len);
+	tko.policydigest_len = sizeof(policy);
+	memcpy(tko.policydigest, policy, tko.policydigest_len);
+
+	rc = tpm2_seal_trusted(chip, &tkp, &tko);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_seal_trusted returned error: %d\n ", rc);
+		goto out;
+	}
+
+	ps = get_policy(chip);
+	/*
+	 * now load the sealed object (we need the pub and priv parts
+	 * returned from prior command.  The blob from
+	 * tpm2_seal_trusted is the entire return from the create, so
+	 * only append the private and public parts
+	 */
+	p = tkp.blob;
+	/* private len */
+	len = tpm_get_inc_u16(&p);
+	p += len;
+	/* add public len */
+	len += tpm_get_inc_u16(&p);
+	/* add 4 for the two length values */
+	len += 4;
+
+	tpm_buf_init(&b1, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
+	/* parent */
+	tpm_buf_append_name(&b1, auth, nullkey, chip->tpmkeyname);
+	tpm_buf_append_hmac_session(&b1, auth, TPM2_SA_CONTINUE_SESSION,
+				    NULL, 0);
+
+	tpm_buf_append(&b1, tkp.blob, len);
+
+	tpm_buf_fill_hmac_session(&b1, auth);
+	rc = tpm_transmit_cmd(chip, &b1, 4, "loading seal");
+	rc = tpm_buf_check_hmac_response(&b1, auth, rc);
+	dev_info(&chip->dev, "TPM: load response returned %d\n", rc);
+	if (rc) {
+		tpm2_flush_context(chip, ps);
+		goto out;
+	}
+	p = &b1.data[TPM_HEADER_SIZE];
+	h = tpm_get_inc_u32(&p);
+	dev_info(&chip->dev, "sealed data loaded at %08x\n", h);
+	/* skip over parameter size */
+	p += 4;
+	len = tpm_get_inc_u16(&p);
+	if (len != sizeof(name)) {
+		dev_err(&chip->dev, "Wrong name size %d\n", len);
+		goto out;
+	}
+	memcpy(name, p, len);
+	tpm_buf_destroy(&b1);
+	tpm_buf_destroy(&buf);
+
+	/*
+	 * now unseal the data using the authority in a HMAC and
+	 * protecting the returned unseal by encryption
+	 */
+	tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	tpm_buf_append_name(&buf, auth, h, name);
+	tpm2_buf_append_auth(&buf, ps, NULL, 0, 0, NULL, 0);
+	tpm_buf_append_hmac_session(&buf, auth, TPM2_SA_ENCRYPT,
+				    NULL, 0);
+	tpm_buf_fill_hmac_session(&buf, auth);
+	rc = tpm_transmit_cmd(chip, &buf, 4, "unseal");
+	rc = tpm_buf_check_hmac_response(&buf, auth, rc);
+	tpm2_flush_context(chip, h);
+	dev_info(&chip->dev, "unseal returns %d\n", rc);
+	if (rc)
+		goto out;
+	p = &buf.data[TPM_HEADER_SIZE + 4];
+	len = tpm_get_inc_u16(&p);
+	if (len != sizeof(payload) + 1) {
+		dev_err(&chip->dev, "wrong unseal payload size %d != %ld",
+			len, sizeof(payload) + 1);
+		goto out;
+	}
+	if (memcmp(payload, p, sizeof(payload)) != 0) {
+		dev_err(&chip->dev, "Payload DID NOT compare correctly\n");
+		goto out;
+	}
+
+	dev_info(&chip->dev, "test5: PASS");
+
+	/*
+	 * test6: extend PCR 16 with a random value and verify it
+	 * comes back correctly
+	 */
+
+	dev_info(&chip->dev, "test6: extend PCR 16");
+
+	digest.alg_id = TPM_ALG_SHA256;
+
+	rc = tpm2_pcr_read(chip, 16, &digest, &digest_len);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_pcr_read returns error: %d\n", rc);
+		goto out;
+	}
+	if (digest_len != SHA256_DIGEST_SIZE) {
+		dev_err(&chip->dev, "wrong digest size %d!=%d\n", digest_len,
+			SHA256_DIGEST_SIZE);
+		goto out;
+	}
+
+	for (i = 0; i < chip->nr_allocated_banks; i++) {
+		rc = tpm2_get_random(chip, extend[i].digest, SHA256_DIGEST_SIZE);
+		if (rc != SHA256_DIGEST_SIZE) {
+			dev_err(&chip->dev, "tpm2_get_random failed: %d\n", rc);
+			goto out;
+		}
+		extend[i].alg_id = chip->allocated_banks[i].alg_id;
+	}
+	rc = tpm2_pcr_extend(chip, 16, extend);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_pcr_extend failed: %d\n", rc);
+		goto out;
+	}
+
+	desc->tfm = sha256_hash;
+	crypto_shash_init(desc);
+	crypto_shash_update(desc, digest.digest, SHA256_DIGEST_SIZE);
+	crypto_shash_update(desc, extend[0].digest, SHA256_DIGEST_SIZE);
+	crypto_shash_final(desc, digest.digest);
+
+	extend[0].alg_id = TPM_ALG_SHA256;
+	rc = tpm2_pcr_read(chip, 16, &extend[0], &digest_len);
+	if (rc) {
+		dev_err(&chip->dev, "tpm2_pcr_read returns error: %d\n", rc);
+		goto out;
+	}
+	if (digest_len != SHA256_DIGEST_SIZE) {
+		dev_err(&chip->dev, "wrong digest size %d!=%d\n", digest_len,
+			SHA256_DIGEST_SIZE);
+		goto out;
+	}
+
+	if (memcmp(digest.digest, extend[0].digest, SHA256_DIGEST_SIZE) != 0) {
+		dev_err(&chip->dev, "Extend digest comparison failed\n");
+		goto out;
+	}
+
+	dev_info(&chip->dev, "All tests passed\n");
+	ret = 0;
+
+ out:
+	tpm2_flush_context(chip, nullkey);
+
+	tpm_put_ops(chip);
+
+	return ret;
+}
+
+module_init(tpm2_sessions_test);
+
+MODULE_LICENSE("GPL");
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 7307f061e5df..8f50ad88c5ab 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -865,6 +865,7 @@ static int parse_start_auth_session(struct tpm2_auth *auth, const u8 *data)
  * 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
+ * @key: A pointer to return the NULL key or NULL if key should be flushed
  *
  * This function loads the NULL seed from its saved context and starts
  * an authentication session on the null seed, allocates a tpm2_auth
diff --git a/drivers/char/tpm/tpm2-sessions.h b/drivers/char/tpm/tpm2-sessions.h
index ec245731edaf..23d62446dd71 100644
--- a/drivers/char/tpm/tpm2-sessions.h
+++ b/drivers/char/tpm/tpm2-sessions.h
@@ -45,7 +45,8 @@ void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
 
 #ifdef CONFIG_TPM_BUS_SECURITY
 
-int tpm2_start_auth_session(struct tpm_chip *chip, struct tpm2_auth **authp);
+int tpm2_start_auth_session(struct tpm_chip *chip,
+			    struct tpm2_auth **authp);
 void tpm_buf_append_name(struct tpm_buf *buf, struct tpm2_auth *auth,
 			 u32 handle, u8 *name);
 void tpm_buf_append_hmac_session(struct tpm_buf *buf, struct tpm2_auth *auth,
-- 
2.16.4


^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 00/12] add integrity and security to TPM2 transactions
  2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
                   ` (11 preceding siblings ...)
  2019-09-09 12:26 ` [PATCH v6 12/12] tpm2-sessions: NOT FOR COMMITTING add sessions testing James Bottomley
@ 2019-09-10 16:21 ` Jarkko Sakkinen
  2019-09-10 16:29   ` James Bottomley
  2019-09-11  8:42   ` Jarkko Sakkinen
  12 siblings, 2 replies; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-10 16:21 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Mon, Sep 09, 2019 at 01:16:48PM +0100, James Bottomley wrote:
> Link to previous cover letter:
> 
> https://lore.kernel.org/linux-integrity/1540193596.3202.7.camel@HansenPartnership.com/
> 
> This is marked v6 instead of v5 because I did a v5 after feedback on v4
> but didn't get around to posting it and then had to rework the whole of
> the kernel space handling while I was on holiday.  I also added the
> documentation of how the whole thing works and the rationale for doing
> it in tpm-security.rst (patch 11).  The main reason for doing this now
> is so we have something to discuss at Plumbers.
> 
> The new patch set implements the various splits requested, but the main
> changes are that the kernel space is gone and is replaced by a context
> save and restore of the generated null seed.  This is easier to handle
> than a full kernel space given the new threading for TPM spaces, but
> conceptually it is still very like a space.  I've also made whether
> integrity and encryption is turned on a Kconfig option.
> 
> James

So... is there a changelog for the revisions?

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 00/12] add integrity and security to TPM2 transactions
  2019-09-10 16:21 ` [PATCH v6 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
@ 2019-09-10 16:29   ` James Bottomley
  2019-09-11  8:42   ` Jarkko Sakkinen
  1 sibling, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-10 16:29 UTC (permalink / raw)
  To: Jarkko Sakkinen; +Cc: linux-integrity, linux-crypto, linux-security-module

On Tue, 2019-09-10 at 17:21 +0100, Jarkko Sakkinen wrote:
> On Mon, Sep 09, 2019 at 01:16:48PM +0100, James Bottomley wrote:
> > Link to previous cover letter:
> > 
> > https://lore.kernel.org/linux-integrity/1540193596.3202.7.camel@Han
> > senPartnership.com/
> > 
> > This is marked v6 instead of v5 because I did a v5 after feedback
> > on v4
> > but didn't get around to posting it and then had to rework the
> > whole of
> > the kernel space handling while I was on holiday.  I also added the
> > documentation of how the whole thing works and the rationale for
> > doing
> > it in tpm-security.rst (patch 11).  The main reason for doing this
> > now
> > is so we have something to discuss at Plumbers.
> > 
> > The new patch set implements the various splits requested, but the
> > main
> > changes are that the kernel space is gone and is replaced by a
> > context
> > save and restore of the generated null seed.  This is easier to
> > handle
> > than a full kernel space given the new threading for TPM spaces,
> > but
> > conceptually it is still very like a space.  I've also made whether
> > integrity and encryption is turned on a Kconfig option.
> > 
> > James
> 
> So... is there a changelog for the revisions?

Well, yes, standard way: they're in the individual patches under the '-
--' prefixed with v6:

James


^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 00/12] add integrity and security to TPM2 transactions
  2019-09-10 16:21 ` [PATCH v6 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
  2019-09-10 16:29   ` James Bottomley
@ 2019-09-11  8:42   ` Jarkko Sakkinen
  2019-09-11  9:40     ` Jarkko Sakkinen
  1 sibling, 1 reply; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-11  8:42 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Tue, Sep 10, 2019 at 05:21:32PM +0100, Jarkko Sakkinen wrote:
> On Mon, Sep 09, 2019 at 01:16:48PM +0100, James Bottomley wrote:
> > Link to previous cover letter:
> > 
> > https://lore.kernel.org/linux-integrity/1540193596.3202.7.camel@HansenPartnership.com/
> > 
> > This is marked v6 instead of v5 because I did a v5 after feedback on v4
> > but didn't get around to posting it and then had to rework the whole of
> > the kernel space handling while I was on holiday.  I also added the
> > documentation of how the whole thing works and the rationale for doing
> > it in tpm-security.rst (patch 11).  The main reason for doing this now
> > is so we have something to discuss at Plumbers.
> > 
> > The new patch set implements the various splits requested, but the main
> > changes are that the kernel space is gone and is replaced by a context
> > save and restore of the generated null seed.  This is easier to handle
> > than a full kernel space given the new threading for TPM spaces, but
> > conceptually it is still very like a space.  I've also made whether
> > integrity and encryption is turned on a Kconfig option.
> > 
> > James
> 
> So... is there a changelog for the revisions?

This also desperately needs a cover letter with the full rationale and
not just a link to an aged cover letter. I have bigger problems with the
form than the function ATM.

TPM's threat model does not cover hardware attacks. It is hardware
designed to give some protection against software attacks. If I were
sending these patches I would start to look for an angle from that
perspective.

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 00/12] add integrity and security to TPM2 transactions
  2019-09-11  8:42   ` Jarkko Sakkinen
@ 2019-09-11  9:40     ` Jarkko Sakkinen
  0 siblings, 0 replies; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-11  9:40 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Wed, Sep 11, 2019 at 09:42:49AM +0100, Jarkko Sakkinen wrote:
> On Tue, Sep 10, 2019 at 05:21:32PM +0100, Jarkko Sakkinen wrote:
> > On Mon, Sep 09, 2019 at 01:16:48PM +0100, James Bottomley wrote:
> > > Link to previous cover letter:
> > > 
> > > https://lore.kernel.org/linux-integrity/1540193596.3202.7.camel@HansenPartnership.com/
> > > 
> > > This is marked v6 instead of v5 because I did a v5 after feedback on v4
> > > but didn't get around to posting it and then had to rework the whole of
> > > the kernel space handling while I was on holiday.  I also added the
> > > documentation of how the whole thing works and the rationale for doing
> > > it in tpm-security.rst (patch 11).  The main reason for doing this now
> > > is so we have something to discuss at Plumbers.
> > > 
> > > The new patch set implements the various splits requested, but the main
> > > changes are that the kernel space is gone and is replaced by a context
> > > save and restore of the generated null seed.  This is easier to handle
> > > than a full kernel space given the new threading for TPM spaces, but
> > > conceptually it is still very like a space.  I've also made whether
> > > integrity and encryption is turned on a Kconfig option.
> > > 
> > > James
> > 
> > So... is there a changelog for the revisions?
> 
> This also desperately needs a cover letter with the full rationale and
> not just a link to an aged cover letter. I have bigger problems with the
> form than the function ATM.
> 
> TPM's threat model does not cover hardware attacks. It is hardware
> designed to give some protection against software attacks. If I were
> sending these patches I would start to look for an angle from that
> perspective.

The rationale can be essentially just that since there is often lots of
*software* running outside the CPU on different cores all around the HW
platform, this will add to defense in depth. I'm not looking for
anything more rockety sciency than that.

I think that was the key lesson from TPM Genie.

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 01/12] tpm-buf: move from static inlines to real functions
  2019-09-09 12:17 ` [PATCH v6 01/12] tpm-buf: move from static inlines to real functions James Bottomley
@ 2019-09-20 14:06   ` Jarkko Sakkinen
  2019-09-20 14:06     ` Jarkko Sakkinen
  0 siblings, 1 reply; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-20 14:06 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Mon, Sep 09, 2019 at 01:17:56PM +0100, James Bottomley wrote:
> This separates out the old tpm_buf_... handling functions from static
> inlines in tpm.h and makes them their own tpm-buf.c file.  This is a
> precursor so we can add new functions for other TPM type handling
> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

What about TPM_BUF_2B that gets added in this commit?

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 01/12] tpm-buf: move from static inlines to real functions
  2019-09-20 14:06   ` Jarkko Sakkinen
@ 2019-09-20 14:06     ` Jarkko Sakkinen
  2019-09-20 15:53       ` James Bottomley
  0 siblings, 1 reply; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-20 14:06 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Fri, Sep 20, 2019 at 05:06:15PM +0300, Jarkko Sakkinen wrote:
> On Mon, Sep 09, 2019 at 01:17:56PM +0100, James Bottomley wrote:
> > This separates out the old tpm_buf_... handling functions from static
> > inlines in tpm.h and makes them their own tpm-buf.c file.  This is a
> > precursor so we can add new functions for other TPM type handling
> > 
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> 
> What about TPM_BUF_2B that gets added in this commit?

Probably just a glitch in rebasing/squashing?

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 02/12] tpm-buf: add handling for TPM2B types
  2019-09-09 12:18 ` [PATCH v6 02/12] tpm-buf: add handling for TPM2B types James Bottomley
@ 2019-09-20 14:18   ` Jarkko Sakkinen
  0 siblings, 0 replies; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-20 14:18 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Mon, Sep 09, 2019 at 01:18:35PM +0100, 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>

I think a better idea would be to have headerless TPM buffers and also
it makes sense to have a separate length field in the struct to keep the
code sane given that sometimes the buffer does not store the length.

E.g.

enum tpm_buf_flags {
	TPM_BUF_OVERFLOW	= BIT(0),
	TPM_BUF_HEADERLESS	= BIT(1),
};

struct tpm_buf {
	unsigned int length;
	struct page *data_page;
	unsigned int flags;
	u8 *data;
};

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling
  2019-09-09 12:20 ` [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling James Bottomley
@ 2019-09-20 14:34   ` Jarkko Sakkinen
  2019-09-20 14:35     ` Jarkko Sakkinen
  0 siblings, 1 reply; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-20 14:34 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Mon, Sep 09, 2019 at 01:20:57PM +0100, James Bottomley wrote:
> This code adds true session based HMAC authentication plus parameter
> decryption and response encryption using AES.
> 
> The basic design of this code 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 now needs a primary
> key to encrypt the session salt to, so we derive an EC key from the
> NULL seed and save its context 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: Added docbook and improved response check API
> v3: Add readpublic, fix hmac length, add API for close on error
>     allow for the hmac session not being first in the sessions
> v4: Make NULL seed template exactly match the SRK ECC template.
>     Also check the NULL primary key name is what getpublic returns
>     to prevent spoofing.  Also parametrise the name size for reuse
> v5: Move to sync_skcipher API
> v6: eliminate kernel space and use context save for null seed and
>     make feature conditional on CONFIG_TPM_BUS_SECURITY
> ---
>  drivers/char/tpm/Kconfig         |   11 +
>  drivers/char/tpm/Makefile        |    1 +
>  drivers/char/tpm/tpm-buf.c       |    1 +
>  drivers/char/tpm/tpm.h           |   20 +-
>  drivers/char/tpm/tpm2-cmd.c      |   22 +-
>  drivers/char/tpm/tpm2-sessions.c | 1203 ++++++++++++++++++++++++++++++++++++++
>  drivers/char/tpm/tpm2-sessions.h |  137 +++++
>  include/linux/tpm.h              |   29 +
>  8 files changed, 1411 insertions(+), 13 deletions(-)
>  create mode 100644 drivers/char/tpm/tpm2-sessions.c
>  create mode 100644 drivers/char/tpm/tpm2-sessions.h
> 
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 88a3c06fc153..96b09adfc163 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -9,6 +9,9 @@ menuconfig TCG_TPM
>  	imply SECURITYFS
>  	select CRYPTO
>  	select CRYPTO_HASH_INFO
> +	select CRYPTO_ECDH
> +	select CRYPTO_AES
> +	select CRYPTO_CFB
>  	---help---
>  	  If you have a TPM security chip in your system, which
>  	  implements the Trusted Computing Group's specification,
> @@ -27,6 +30,14 @@ menuconfig TCG_TPM
>  
>  if TCG_TPM
>  
> +config TPM_BUS_SECURITY
> +       bool "Use secure transactions on the TPM bus"
> +       default y
> +       ---help---
> +         Setting this causes us to deploy a tamper resistent scheme
> +	 for communicating with the TPM to prevent or detect bus snooping
> +	 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 78bd025b808a..8f9e58317048 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 553adb84b0ac..f56350123a08 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -31,6 +31,7 @@ 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.h b/drivers/char/tpm/tpm.h
> index 85a7302ddfeb..ebead8e4c3fe 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -80,6 +80,7 @@ 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 */
> @@ -116,6 +117,8 @@ enum tpm2_command_codes {
>  	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
>  	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
>  	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
> +	TPM2_CC_READ_PUBLIC		= 0x0173,
> +	TPM2_CC_START_AUTH_SESS		= 0x0176,
>  	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
>  	TPM2_CC_GET_CAPABILITY	        = 0x017A,
>  	TPM2_CC_GET_RANDOM	        = 0x017B,
> @@ -128,6 +131,7 @@ enum tpm2_command_codes {
>  };
>  
>  enum tpm2_permanent_handles {
> +	TPM2_RH_NULL		= 0x40000007,
>  	TPM2_RS_PW		= 0x40000009,
>  };
>  
> @@ -286,7 +290,8 @@ enum tpm_buf_flags {
>  
>  struct tpm_buf {
>  	struct page *data_page;
> -	unsigned int flags;
> +	u8 flags;
> +	u8 handles;
>  	u8 *data;
>  };
>  
> @@ -306,6 +311,9 @@ u8 tpm_get_inc_u8(const u8 **ptr);
>  u16 tpm_get_inc_u16(const u8 **ptr);
>  u32 tpm_get_inc_u32(const u8 **ptr);
>  
> +/* opaque structure, holds auth session parameters like the session key */
> +struct tpm2_auth;
> +
>  extern struct class *tpm_class;
>  extern struct class *tpmrm_class;
>  extern dev_t tpm_devt;
> @@ -408,4 +416,14 @@ int 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 ba9acae83bff..d120b0a260eb 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -12,17 +12,10 @@
>   */
>  
>  #include "tpm.h"
> +#include "tpm2-sessions.h"
>  #include <crypto/hash_info.h>
>  #include <keys/trusted-type.h>
>  
> -enum tpm2_object_attributes {
> -	TPM2_OA_USER_WITH_AUTH		= BIT(6),
> -};
> -
> -enum tpm2_session_attributes {
> -	TPM2_SA_CONTINUE_SESSION	= BIT(0),
> -};
> -
>  struct tpm2_hash {
>  	unsigned int crypto_id;
>  	unsigned int tpm_id;
> @@ -388,10 +381,10 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
>   * @hmac: the session HMAC or password, may be NULL if not used
>   * @hmac_len: the session HMAC or password length, maybe 0 if not used
>   */
> -static void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
> -				 const u8 *nonce, u16 nonce_len,
> -				 u8 attributes,
> -				 const u8 *hmac, u16 hmac_len)
> +void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle,
> +			  const u8 *nonce, u16 nonce_len,
> +			  u8 attributes,
> +			  const u8 *hmac, u16 hmac_len)
>  {
>  	tpm_buf_append_u32(buf, 9 + nonce_len + hmac_len);
>  	tpm_buf_append_u32(buf, session_handle);
> @@ -1042,6 +1035,11 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>  
>  	rc = tpm2_get_cc_attrs_tbl(chip);
>  
> +	if (rc)
> +		goto out;
> +
> +	rc = tpm2_sessions_init(chip);
> +
>  out:
>  	if (rc > 0)
>  		rc = -ENODEV;
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> new file mode 100644
> index 000000000000..7307f061e5df
> --- /dev/null
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -0,0 +1,1203 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright (C) 2018 James.Bottomley@HansenPartnership.com

*/

/**
 * DOC: TPM2 Sessions

> + *
> + * 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.

Should be reformatted to use kdoc e.g.

1. Documentation block in the file header (the last section in [1]).
2. Proper kdoc's for the functions.

This will allow generation of the documentation from this if done right
(e.g. like DRM people do).

> + */
> +
> +#include "tpm.h"
> +#include "tpm2-sessions.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>
> +#include <crypto/skcipher.h>
> +
> +/* if you change to AES256, you only need change this */
> +#define AES_KEYBYTES	AES_KEYSIZE_128

Ugh, this just masks things, please remove.

> +
> +#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;
> +	/* saved session attributes */
> +	u8 attrs;
> +	__be32 ordinal;
> +	struct crypto_sync_skcipher *aes;
> +	struct tpm_chip *chip;
> +	/* 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 + SHA256_DIGEST_SIZE];
> +};

Check "kernel-doc for structs, unions, enums, and typedefs" in [1].

Look at iit this way: you've done a lot of work to explain why you
are doing what you are doing and that is great. If we can generate
documentation from it, it will be more accessible to everyone and does
not get buried inside the source tree :-)

[1] https://www.kernel.org/doc/Documentation/kernel-doc-nano-HOWTO.txt

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling
  2019-09-20 14:34   ` Jarkko Sakkinen
@ 2019-09-20 14:35     ` Jarkko Sakkinen
  0 siblings, 0 replies; 23+ messages in thread
From: Jarkko Sakkinen @ 2019-09-20 14:35 UTC (permalink / raw)
  To: James Bottomley; +Cc: linux-integrity, linux-crypto, linux-security-module

On Fri, Sep 20, 2019 at 05:34:00PM +0300, Jarkko Sakkinen wrote:
> On Mon, Sep 09, 2019 at 01:20:57PM +0100, James Bottomley wrote:

Forgot to ask: what is the new field handles?

/Jarkko

^ permalink raw reply	[flat|nested] 23+ messages in thread

* Re: [PATCH v6 01/12] tpm-buf: move from static inlines to real functions
  2019-09-20 14:06     ` Jarkko Sakkinen
@ 2019-09-20 15:53       ` James Bottomley
  0 siblings, 0 replies; 23+ messages in thread
From: James Bottomley @ 2019-09-20 15:53 UTC (permalink / raw)
  To: Jarkko Sakkinen; +Cc: linux-integrity, linux-crypto, linux-security-module

On Fri, 2019-09-20 at 17:06 +0300, Jarkko Sakkinen wrote:
> On Fri, Sep 20, 2019 at 05:06:15PM +0300, Jarkko Sakkinen wrote:
> > On Mon, Sep 09, 2019 at 01:17:56PM +0100, James Bottomley wrote:
> > > This separates out the old tpm_buf_... handling functions from
> > > static
> > > inlines in tpm.h and makes them their own tpm-buf.c file.  This
> > > is a
> > > precursor so we can add new functions for other TPM type handling
> > > 
> > > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership
> > > .com>
> > 
> > What about TPM_BUF_2B that gets added in this commit?
> 
> Probably just a glitch in rebasing/squashing?

Well a glitch in splitting one patch into three, yes.  I'll fix it up.

James


^ permalink raw reply	[flat|nested] 23+ messages in thread

end of thread, back to index

Thread overview: 23+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
2019-09-09 12:17 ` [PATCH v6 01/12] tpm-buf: move from static inlines to real functions James Bottomley
2019-09-20 14:06   ` Jarkko Sakkinen
2019-09-20 14:06     ` Jarkko Sakkinen
2019-09-20 15:53       ` James Bottomley
2019-09-09 12:18 ` [PATCH v6 02/12] tpm-buf: add handling for TPM2B types James Bottomley
2019-09-20 14:18   ` Jarkko Sakkinen
2019-09-09 12:19 ` [PATCH v6 03/12] tpm-buf: add cursor based functions for response parsing James Bottomley
2019-09-09 12:19 ` [PATCH v6 04/12] tpm2-space: export the context save and load commands James Bottomley
2019-09-09 12:20 ` [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling James Bottomley
2019-09-20 14:34   ` Jarkko Sakkinen
2019-09-20 14:35     ` Jarkko Sakkinen
2019-09-09 12:21 ` [PATCH v6 06/12] tpm-buf: add tpm_buf_parameters() James Bottomley
2019-09-09 12:22 ` [PATCH v6 07/12] tpm2: add hmac checks to tpm2_pcr_extend() James Bottomley
2019-09-09 12:22 ` [PATCH v6 08/12] tpm2: add session encryption protection to tpm2_get_random() James Bottomley
2019-09-09 12:23 ` [PATCH v6 09/12] trusted keys: Add session encryption protection to the seal/unseal path James Bottomley
2019-09-09 12:24 ` [PATCH v6 10/12] tpm: add the null key name as a tpm2 sysfs variable James Bottomley
2019-09-09 12:25 ` [PATCH v6 11/12] Documentation: add tpm-security.rst James Bottomley
2019-09-09 12:26 ` [PATCH v6 12/12] tpm2-sessions: NOT FOR COMMITTING add sessions testing James Bottomley
2019-09-10 16:21 ` [PATCH v6 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
2019-09-10 16:29   ` James Bottomley
2019-09-11  8:42   ` Jarkko Sakkinen
2019-09-11  9:40     ` Jarkko Sakkinen

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