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* [PATCH v4 00/11] Encrypted Hibernation
@ 2022-11-03 18:01 Evan Green
  2022-11-03 18:01 ` [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data Evan Green
                   ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Evan Green @ 2022-11-03 18:01 UTC (permalink / raw)
  To: linux-kernel
  Cc: corbet, linux-pm, rjw, gwendal, apronin, Pavel Machek, Kees Cook,
	Matthew Garrett, linux-integrity, jejb, zohar, dlunev,
	Eric Biggers, Ben Boeckel, jarkko, Evan Green, David Howells,
	James Morris, Jason Gunthorpe, Len Brown, Matthew Garrett,
	Paul Moore, Peter Huewe, Rafael J. Wysocki, Serge E. Hallyn,
	axelj, keyrings, linux-doc, linux-security-module

We are exploring enabling hibernation in some new scenarios. However,
our security team has a few requirements, listed below:
1. The hibernate image must be encrypted with protection derived from
   both the platform (eg TPM) and user authentication data (eg
   password).
2. Hibernation must not be a vector by which a malicious userspace can
   escalate to the kernel.

Requirement #1 can be achieved solely with uswsusp, however requirement
2 necessitates mechanisms in the kernel to guarantee integrity of the
hibernate image. The kernel needs a way to authenticate that it generated
the hibernate image being loaded, and that the image has not been tampered
with. Adding support for in-kernel AEAD encryption with a TPM-sealed key
allows us to achieve both requirements with a single computation pass.

Matthew Garrett published a series [1] that aligns closely with this
goal. His series utilized the fact that PCR23 is a resettable PCR that
can be blocked from access by usermode. The TPM can create a sealed key
tied to PCR23 in two ways. First, the TPM can attest to the value of
PCR23 when the key was created, which the kernel can use on resume to
verify that the kernel must have created the key (since it is the only
one capable of modifying PCR23). It can also create a policy that enforces
PCR23 be set to a specific value as a condition of unsealing the key,
preventing usermode from unsealing the key by talking directly to the
TPM.

This series adopts that primitive as a foundation, tweaking and building
on it a bit. Where Matthew's series used the TPM-backed key to encrypt a
hash of the image, this series uses the key directly as a gcm(aes)
encryption key, which the kernel uses to encrypt and decrypt the
hibernate image in chunks of 16 pages. This provides both encryption and
integrity, which turns out to be a noticeable performance improvement over
separate passes for encryption and hashing.

The series also introduces the concept of mixing user key material into
the encryption key. This allows usermode to introduce key material
based on unspecified external authentication data (in our case derived
from something like the user password or PIN), without requiring
usermode to do a separate encryption pass.

Matthew also documented issues his series had [2] related to generating
fake images by booting alternate kernels without the PCR23 limiting.
With access to PCR23 on the same machine, usermode can create fake
hibernate images that are indistinguishable to the new kernel from
genuine ones. His post outlines a solution that involves adding more
PCRs into the creation data and policy, with some gyrations to make this
work well on a standard PC.

Our approach would be similar: on our machines PCR 0 indicates whether
the system is booted in secure/verified mode or developer mode. By
adding PCR0 to the policy, we can reject hibernate images made in
developer mode while in verified mode (or vice versa).

Additionally, mixing in the user authentication data limits both
data exfiltration attacks (eg a stolen laptop) and forged hibernation
image attacks to attackers that already know the authentication data (eg
user's password). This, combined with our relatively sealed userspace
(dm-verity on the rootfs), and some judicious clearing of the hibernate
image (such as across an OS update) further reduce the risk of an online
attack. The remaining attack space of a forgery from someone with
physical access to the device and knowledge of the authentication data
is out of scope for us, given that flipping to developer mode or
reflashing RO firmware trivially achieves the same thing.

A couple of patches still need to be written on top of this series. The
generalized functionality to OR in additional PCRs via Kconfig (like PCR
0 or 5) still needs to be added. We'll also need a patch that disallows
unencrypted forms of resume from hibernation, to fully close the door
to malicious userspace. However, I wanted to get this series out first
and get reactions from upstream before continuing to add to it.

[1] https://patchwork.kernel.org/project/linux-pm/cover/20210220013255.1083202-1-matthewgarrett@google.com/
[2] https://mjg59.dreamwidth.org/58077.html

Changes in v4:
 - Open code tpm2_pcr_reset implementation in tpm-interface.c (Jarkko)
 - Rename interface symbol to tpm2_pcr_reset, fix kerneldocs (Jarkko)
 - Augment the commit message (Jarkko)
 - Local ordering and whitespace changes (Jarkko)
 - s/tpm_pcr_reset/tpm2_pcr_reset/ due to change in other patch
 - Variable ordering and whitespace fixes (Jarkko)
 - Add NULL check explanation in teardown (Jarkko)
 - Change strlen+1 to sizeof for static buffer (Jarkko)
 - Fix nr_allocated_banks loop overflow (found via KASAN)
 - Local variable reordering (Jarkko)
 - Local variable ordering (Jarkko)

Changes in v3:
 - Unify tpm1/2_pcr_reset prototypes (Jarkko)
 - Wait no, remove the TPM1 stuff altogether (Jarkko)
 - Remove extra From tag and blank in commit msg (Jarkko).
 - Split find_and_validate_cc() export to its own patch (Jarkko)
 - Rename tpm_find_and_validate_cc() to tpm2_find_and_validate_cc().
 - Fix up commit message (Jarkko)
 - tpm2_find_and_validate_cc() was split (Jarkko)
 - Simply fully restrict TPM1 since v2 failed to account for tunnelled
   transport sessions (Stefan and Jarkko).
 - Fix SoB and -- note ordering (Kees)
 - Add comments describing the TPM2 spec type names for the new fields
   in tpm2key.asn1 (Kees)
 - Add len buffer checks in tpm2_key_encode() (Kees)
 - Clarified creationpcrs documentation (Ben)
 - Changed funky tag to suggested-by (Kees). Matthew, holler if you want
   something different.
 - ENCRYPTED_HIBERNATION needs TRUSTED_KEYS builtin for
   key_type_trusted.
 - Remove KEYS dependency since it's covered by TRUSTED_KEYS (Kees)
 - Changed funky tag to Co-developed-by (Kees). Matthew, holler if you
   want something different.
 - Changed funky tag to Co-developed-by (Kees)

Changes in v2:
 - Fixed sparse warnings
 - Adjust hash len by 2 due to new ASN.1 storage, and add underflow
   check.
 - Rework load/create_kernel_key() to eliminate a label (Andrey)
 - Call put_device() needed from calling tpm_default_chip().
 - Add missing static on snapshot_encrypted_byte_count()
 - Fold in only the used kernel key bytes to the user key.
 - Make the user key length 32 (Eric)
 - Use CRYPTO_LIB_SHA256 for less boilerplate (Eric)
 - Fixed some sparse warnings
 - Use CRYPTO_LIB_SHA256 to get rid of sha256_data() (Eric)
 - Adjusted offsets due to new ASN.1 format, and added a creation data
   length check.
 - Fix sparse warnings
 - Fix session type comment (Andrey)
 - Eliminate extra label in get/create_kernel_key() (Andrey)
 - Call tpm_try_get_ops() before calling tpm2_flush_context().

Evan Green (8):
  tpm: Export and rename tpm2_find_and_validate_cc()
  security: keys: trusted: Include TPM2 creation data
  security: keys: trusted: Verify creation data
  PM: hibernate: Add kernel-based encryption
  PM: hibernate: Use TPM-backed keys to encrypt image
  PM: hibernate: Mix user key in encrypted hibernate
  PM: hibernate: Verify the digest encryption key
  PM: hibernate: seal the encryption key with a PCR policy

Matthew Garrett (3):
  tpm: Add support for in-kernel resetting of PCRs
  tpm: Allow PCR 23 to be restricted to kernel-only use
  security: keys: trusted: Allow storage of PCR values in creation data

 Documentation/power/userland-swsusp.rst       |    8 +
 .../security/keys/trusted-encrypted.rst       |    6 +
 drivers/char/tpm/Kconfig                      |   12 +
 drivers/char/tpm/tpm-dev-common.c             |    8 +
 drivers/char/tpm/tpm-interface.c              |   47 +
 drivers/char/tpm/tpm.h                        |   22 +
 drivers/char/tpm/tpm1-cmd.c                   |   13 +
 drivers/char/tpm/tpm2-cmd.c                   |   29 +-
 drivers/char/tpm/tpm2-space.c                 |    8 +-
 include/keys/trusted-type.h                   |    9 +
 include/linux/tpm.h                           |   19 +
 include/uapi/linux/suspend_ioctls.h           |   28 +-
 kernel/power/Kconfig                          |   15 +
 kernel/power/Makefile                         |    1 +
 kernel/power/power.h                          |    1 +
 kernel/power/snapenc.c                        | 1043 +++++++++++++++++
 kernel/power/snapshot.c                       |    5 +
 kernel/power/user.c                           |   44 +-
 kernel/power/user.h                           |  116 ++
 security/keys/trusted-keys/tpm2key.asn1       |   15 +-
 security/keys/trusted-keys/trusted_tpm1.c     |    9 +
 security/keys/trusted-keys/trusted_tpm2.c     |  318 ++++-
 22 files changed, 1724 insertions(+), 52 deletions(-)
 create mode 100644 kernel/power/snapenc.c
 create mode 100644 kernel/power/user.h

-- 
2.38.1.431.g37b22c650d-goog


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data
  2022-11-03 18:01 [PATCH v4 00/11] Encrypted Hibernation Evan Green
@ 2022-11-03 18:01 ` Evan Green
  2022-11-04 18:33   ` Kees Cook
  2022-11-03 18:01 ` [PATCH v4 05/11] security: keys: trusted: Allow storage of PCR values in " Evan Green
  2022-11-03 18:01 ` [PATCH v4 06/11] security: keys: trusted: Verify " Evan Green
  2 siblings, 1 reply; 9+ messages in thread
From: Evan Green @ 2022-11-03 18:01 UTC (permalink / raw)
  To: linux-kernel
  Cc: corbet, linux-pm, rjw, gwendal, apronin, Pavel Machek, Kees Cook,
	Matthew Garrett, linux-integrity, jejb, zohar, dlunev,
	Eric Biggers, Ben Boeckel, jarkko, Evan Green, David Howells,
	James Morris, Paul Moore, Serge E. Hallyn, keyrings,
	linux-security-module

In addition to the private key and public key, the TPM2_Create
command may also return creation data, a creation hash, and a creation
ticket. These fields allow the TPM to attest to the contents of a
specified set of PCRs at the time the trusted key was created. Encrypted
hibernation will use this to ensure that PCRs settable only by the
kernel were set properly at the time of creation, indicating this is an
authentic hibernate key.

Encode these additional parameters into the ASN.1 created to represent
the key blob. The new fields are made optional so that they don't bloat
key blobs which don't need them, and to ensure interoperability with
old blobs.

Signed-off-by: Evan Green <evgreen@chromium.org>
---

(no changes since v3)

Changes in v3:
 - Fix SoB and -- note ordering (Kees)
 - Add comments describing the TPM2 spec type names for the new fields
   in tpm2key.asn1 (Kees)
 - Add len buffer checks in tpm2_key_encode() (Kees)

This is a replacement for Matthew's original patch here:
https://patchwork.kernel.org/patch/12096489/

That patch was written before the exported key format was switched to
ASN.1. This patch accomplishes the same thing (saving, loading, and
getting pointers to the creation data) while utilizing the new ASN.1
format.

---
 include/keys/trusted-type.h               |   8 +
 security/keys/trusted-keys/tpm2key.asn1   |  15 +-
 security/keys/trusted-keys/trusted_tpm2.c | 216 +++++++++++++++++++---
 3 files changed, 213 insertions(+), 26 deletions(-)

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index 4eb64548a74f1a..209086fed240a5 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -22,15 +22,23 @@
 #define MAX_BLOB_SIZE			512
 #define MAX_PCRINFO_SIZE		64
 #define MAX_DIGEST_SIZE			64
+#define MAX_CREATION_DATA		412
+#define MAX_TK				76
 
 struct trusted_key_payload {
 	struct rcu_head rcu;
 	unsigned int key_len;
 	unsigned int blob_len;
+	unsigned int creation_len;
+	unsigned int creation_hash_len;
+	unsigned int tk_len;
 	unsigned char migratable;
 	unsigned char old_format;
 	unsigned char key[MAX_KEY_SIZE + 1];
 	unsigned char blob[MAX_BLOB_SIZE];
+	unsigned char *creation;
+	unsigned char *creation_hash;
+	unsigned char *tk;
 };
 
 struct trusted_key_options {
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
index f57f869ad60068..608f8d9ca95fa8 100644
--- a/security/keys/trusted-keys/tpm2key.asn1
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -7,5 +7,18 @@ TPMKey ::= SEQUENCE {
 	emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL,
 	parent		INTEGER ({tpm2_key_parent}),
 	pubkey		OCTET STRING ({tpm2_key_pub}),
-	privkey		OCTET STRING ({tpm2_key_priv})
+	privkey		OCTET STRING ({tpm2_key_priv}),
+	---
+	--- A TPM2B_CREATION_DATA struct as returned from the TPM2_Create command.
+	---
+	creationData	[1] EXPLICIT OCTET STRING OPTIONAL ({tpm2_key_creation_data}),
+	---
+	--- A TPM2B_DIGEST of the creationHash as returned from the TPM2_Create
+	--- command.
+	---
+	creationHash	[2] EXPLICIT OCTET STRING OPTIONAL ({tpm2_key_creation_hash}),
+	---
+	--- A TPMT_TK_CREATION ticket as returned from the TPM2_Create command.
+	---
+	creationTk	[3] EXPLICIT OCTET STRING OPTIONAL ({tpm2_key_creation_tk})
 	}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 2b2c8eb258d5bd..e1388d7d799a36 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -33,19 +33,54 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 			   u8 *src, u32 len)
 {
 	const int SCRATCH_SIZE = PAGE_SIZE;
+	u8 *end = src + len;
 	u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
 	u8 *work = scratch, *work1;
 	u8 *end_work = scratch + SCRATCH_SIZE;
 	u8 *priv, *pub;
+	u8 *creation_data = NULL, *creation_hash = NULL, *creation_tk = NULL;
+	u16 creation_data_len, creation_hash_len = 0, creation_tk_len = 0;
 	u16 priv_len, pub_len;
+	int rc;
+
+	if (src + 2 > end)
+		return -EINVAL;
 
 	priv_len = get_unaligned_be16(src) + 2;
 	priv = src;
 
 	src += priv_len;
-
+	if (src + 2 > end)
+		return -EINVAL;
 	pub_len = get_unaligned_be16(src) + 2;
 	pub = src;
+	src += pub_len;
+	if (src + 2 > end)
+		return -EINVAL;
+	creation_data_len = get_unaligned_be16(src);
+	if (creation_data_len) {
+		creation_data_len += 2;
+		creation_data = src;
+		src += creation_data_len;
+		if (src + 2 > end)
+			return -EINVAL;
+
+		creation_hash_len = get_unaligned_be16(src) + 2;
+		creation_hash = src;
+		src += creation_hash_len;
+		if (src + 2 > end)
+			return -EINVAL;
+
+		/*
+		 * The creation ticket (TPMT_TK_CREATION) consists of a 2 byte
+		 * tag, 4 byte handle, and then a TPM2B_DIGEST, which is a 2
+		 * byte length followed by data.
+		 */
+		creation_tk_len = get_unaligned_be16(src + 6) + 8;
+		creation_tk = src;
+		if (creation_tk + creation_tk_len > end)
+			return -EINVAL;
+	}
 
 	if (!scratch)
 		return -ENOMEM;
@@ -63,26 +98,81 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	}
 
 	/*
-	 * Assume both octet strings will encode to a 2 byte definite length
+	 * Assume each octet string will encode to a 2 byte definite length.
+	 * Each optional octet string consumes one extra byte.
 	 *
-	 * Note: For a well behaved TPM, this warning should never
-	 * trigger, so if it does there's something nefarious going on
+	 * Note: For a well behaved TPM, this warning should never trigger, so
+	 * if it does there's something nefarious going on
 	 */
-	if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
-		 "BUG: scratch buffer is too small"))
-		return -EINVAL;
+	if (WARN(work - scratch + pub_len + priv_len + creation_data_len +
+		 creation_hash_len + creation_tk_len + (7 * 5) + 3 >
+		 SCRATCH_SIZE,
+		 "BUG: scratch buffer is too small")) {
+		rc = -EINVAL;
+		goto err;
+	}
 
 	work = asn1_encode_integer(work, end_work, options->keyhandle);
 	work = asn1_encode_octet_string(work, end_work, pub, pub_len);
 	work = asn1_encode_octet_string(work, end_work, priv, priv_len);
+	if (creation_data_len) {
+		u8 *scratch2 = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
+		u8 *work2;
+		u8 *end_work2 = scratch2 + SCRATCH_SIZE;
+
+		if (!scratch2) {
+			rc = -ENOMEM;
+			goto err;
+		}
+
+		work2 = asn1_encode_octet_string(scratch2,
+						 end_work2,
+						 creation_data,
+						 creation_data_len);
+
+		work = asn1_encode_tag(work,
+				       end_work,
+				       1,
+				       scratch2,
+				       work2 - scratch2);
+
+		work2 = asn1_encode_octet_string(scratch2,
+						 end_work2,
+						 creation_hash,
+						 creation_hash_len);
+
+		work = asn1_encode_tag(work,
+				       end_work,
+				       2,
+				       scratch2,
+				       work2 - scratch2);
+
+		work2 = asn1_encode_octet_string(scratch2,
+						 end_work2,
+						 creation_tk,
+						 creation_tk_len);
+
+		work = asn1_encode_tag(work,
+				       end_work,
+				       3,
+				       scratch2,
+				       work2 - scratch2);
+
+		kfree(scratch2);
+	}
 
 	work1 = payload->blob;
 	work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob),
 				     scratch, work - scratch);
-	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed"))
-		return PTR_ERR(work1);
+	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed")) {
+		rc = PTR_ERR(work1);
+		goto err;
+	}
 
 	return work1 - payload->blob;
+err:
+	kfree(scratch);
+	return rc;
 }
 
 struct tpm2_key_context {
@@ -91,15 +181,21 @@ struct tpm2_key_context {
 	u32 pub_len;
 	const u8 *priv;
 	u32 priv_len;
+	const u8 *creation_data;
+	u32 creation_data_len;
+	const u8 *creation_hash;
+	u32 creation_hash_len;
+	const u8 *creation_tk;
+	u32 creation_tk_len;
 };
 
 static int tpm2_key_decode(struct trusted_key_payload *payload,
-			   struct trusted_key_options *options,
-			   u8 **buf)
+			   struct trusted_key_options *options)
 {
+	u64 data_len;
 	int ret;
 	struct tpm2_key_context ctx;
-	u8 *blob;
+	u8 *blob, *buf;
 
 	memset(&ctx, 0, sizeof(ctx));
 
@@ -108,21 +204,57 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
 	if (ret < 0)
 		return ret;
 
-	if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE)
+	data_len = ctx.priv_len + ctx.pub_len + ctx.creation_data_len +
+		   ctx.creation_hash_len + ctx.creation_tk_len;
+
+	if (data_len > MAX_BLOB_SIZE)
 		return -EINVAL;
 
-	blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL);
-	if (!blob)
+	buf = kmalloc(data_len + 4, GFP_KERNEL);
+	if (!buf)
 		return -ENOMEM;
 
-	*buf = blob;
+	blob = buf;
 	options->keyhandle = ctx.parent;
 
 	memcpy(blob, ctx.priv, ctx.priv_len);
 	blob += ctx.priv_len;
 
 	memcpy(blob, ctx.pub, ctx.pub_len);
+	blob += ctx.pub_len;
+	if (ctx.creation_data_len) {
+		memcpy(blob, ctx.creation_data, ctx.creation_data_len);
+		blob += ctx.creation_data_len;
+	}
+
+	if (ctx.creation_hash_len) {
+		memcpy(blob, ctx.creation_hash, ctx.creation_hash_len);
+		blob += ctx.creation_hash_len;
+	}
+
+	if (ctx.creation_tk_len) {
+		memcpy(blob, ctx.creation_tk, ctx.creation_tk_len);
+		blob += ctx.creation_tk_len;
+	}
+
+	/*
+	 * Copy the buffer back into the payload blob since the creation
+	 * info will be used after loading.
+	 */
+	payload->blob_len = blob - buf;
+	memcpy(payload->blob, buf, payload->blob_len);
+	if (ctx.creation_data_len) {
+		payload->creation = payload->blob + ctx.priv_len + ctx.pub_len;
+		payload->creation_len = ctx.creation_data_len;
+		payload->creation_hash = payload->creation + ctx.creation_data_len;
+		payload->creation_hash_len = ctx.creation_hash_len;
+		payload->tk = payload->creation_hash +
+			      payload->creation_hash_len;
+
+		payload->tk_len = ctx.creation_tk_len;
+	}
 
+	kfree(buf);
 	return 0;
 }
 
@@ -185,6 +317,42 @@ int tpm2_key_priv(void *context, size_t hdrlen,
 	return 0;
 }
 
+int tpm2_key_creation_data(void *context, size_t hdrlen,
+			   unsigned char tag,
+			   const void *value, size_t vlen)
+{
+	struct tpm2_key_context *ctx = context;
+
+	ctx->creation_data = value;
+	ctx->creation_data_len = vlen;
+
+	return 0;
+}
+
+int tpm2_key_creation_hash(void *context, size_t hdrlen,
+			   unsigned char tag,
+			   const void *value, size_t vlen)
+{
+	struct tpm2_key_context *ctx = context;
+
+	ctx->creation_hash = value;
+	ctx->creation_hash_len = vlen;
+
+	return 0;
+}
+
+int tpm2_key_creation_tk(void *context, size_t hdrlen,
+			 unsigned char tag,
+			 const void *value, size_t vlen)
+{
+	struct tpm2_key_context *ctx = context;
+
+	ctx->creation_tk = value;
+	ctx->creation_tk_len = vlen;
+
+	return 0;
+}
+
 /**
  * tpm_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer.
  *
@@ -229,6 +397,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		      struct trusted_key_options *options)
 {
 	int blob_len = 0;
+	unsigned int offset;
 	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
@@ -317,13 +486,14 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		rc = -E2BIG;
 		goto out;
 	}
-	if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
+	offset = TPM_HEADER_SIZE + 4;
+	if (tpm_buf_length(&buf) < offset + blob_len) {
 		rc = -EFAULT;
 		goto out;
 	}
 
 	blob_len = tpm2_key_encode(payload, options,
-				   &buf.data[TPM_HEADER_SIZE + 4],
+				   &buf.data[offset],
 				   blob_len);
 
 out:
@@ -370,13 +540,11 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	int rc;
 	u32 attrs;
 
-	rc = tpm2_key_decode(payload, options, &blob);
-	if (rc) {
-		/* old form */
-		blob = payload->blob;
+	rc = tpm2_key_decode(payload, options);
+	if (rc)
 		payload->old_format = 1;
-	}
 
+	blob = payload->blob;
 	/* new format carries keyhandle but old format doesn't */
 	if (!options->keyhandle)
 		return -EINVAL;
@@ -433,8 +601,6 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
 
 out:
-	if (blob != payload->blob)
-		kfree(blob);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0)
-- 
2.38.1.431.g37b22c650d-goog


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* [PATCH v4 05/11] security: keys: trusted: Allow storage of PCR values in creation data
  2022-11-03 18:01 [PATCH v4 00/11] Encrypted Hibernation Evan Green
  2022-11-03 18:01 ` [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data Evan Green
@ 2022-11-03 18:01 ` Evan Green
  2022-11-04 18:34   ` Kees Cook
  2022-11-03 18:01 ` [PATCH v4 06/11] security: keys: trusted: Verify " Evan Green
  2 siblings, 1 reply; 9+ messages in thread
From: Evan Green @ 2022-11-03 18:01 UTC (permalink / raw)
  To: linux-kernel
  Cc: corbet, linux-pm, rjw, gwendal, apronin, Pavel Machek, Kees Cook,
	Matthew Garrett, linux-integrity, jejb, zohar, dlunev,
	Eric Biggers, Ben Boeckel, jarkko, Matthew Garrett,
	Matthew Garrett, Evan Green, Ben Boeckel, David Howells,
	James Morris, Paul Moore, Serge E. Hallyn, keyrings, linux-doc,
	linux-security-module

From: Matthew Garrett <matthewgarrett@google.com>

When TPMs generate keys, they can also generate some information
describing the state of the PCRs at creation time. This data can then
later be certified by the TPM, allowing verification of the PCR values.
This allows us to determine the state of the system at the time a key
was generated. Add an additional argument to the trusted key creation
options, allowing the user to provide the set of PCRs that should have
their values incorporated into the creation data.

Link: https://lore.kernel.org/lkml/20210220013255.1083202-6-matthewgarrett@google.com/
Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Evan Green <evgreen@chromium.org>
Reviewed-by: Ben Boeckel <linux@me.benboeckel.net>
---

(no changes since v3)

Changes in v3:
 - Clarified creationpcrs documentation (Ben)

 .../security/keys/trusted-encrypted.rst       |  6 +++++
 include/keys/trusted-type.h                   |  1 +
 security/keys/trusted-keys/trusted_tpm1.c     |  9 +++++++
 security/keys/trusted-keys/trusted_tpm2.c     | 25 +++++++++++++++++--
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 9bc9db8ec6517c..a1872964fe862f 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -199,6 +199,12 @@ Usage::
        policyhandle= handle to an authorization policy session that defines the
                      same policy and with the same hash algorithm as was used to
                      seal the key.
+       creationpcrs= hex integer representing the set of PCRs to be
+                     included in the creation data. For each bit set, the
+                     corresponding PCR will be included in the key creation
+                     data. Bit 0 corresponds to PCR0. Currently only the first
+                     PC standard 24 PCRs are supported on the currently active
+                     bank. Leading zeroes are optional. TPM2 only.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index 209086fed240a5..8523d41507b2a4 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -54,6 +54,7 @@ struct trusted_key_options {
 	uint32_t policydigest_len;
 	unsigned char policydigest[MAX_DIGEST_SIZE];
 	uint32_t policyhandle;
+	uint32_t creation_pcrs;
 };
 
 struct trusted_key_ops {
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index aa108bea6739b3..2975827c01bec0 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -713,6 +713,7 @@ enum {
 	Opt_hash,
 	Opt_policydigest,
 	Opt_policyhandle,
+	Opt_creationpcrs,
 };
 
 static const match_table_t key_tokens = {
@@ -725,6 +726,7 @@ static const match_table_t key_tokens = {
 	{Opt_hash, "hash=%s"},
 	{Opt_policydigest, "policydigest=%s"},
 	{Opt_policyhandle, "policyhandle=%s"},
+	{Opt_creationpcrs, "creationpcrs=%s"},
 	{Opt_err, NULL}
 };
 
@@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			opt->policyhandle = handle;
 			break;
+		case Opt_creationpcrs:
+			if (!tpm2)
+				return -EINVAL;
+			res = kstrtoint(args[0].from, 16, &opt->creation_pcrs);
+			if (res < 0)
+				return -EINVAL;
+			break;
 		default:
 			return -EINVAL;
 		}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index e1388d7d799a36..a7ad83bc0e5396 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -401,7 +401,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
-	int i;
+	int i, j;
 	int rc;
 
 	for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
@@ -470,7 +470,28 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	tpm_buf_append_u16(&buf, 0);
 
 	/* creation PCR */
-	tpm_buf_append_u32(&buf, 0);
+	if (options->creation_pcrs) {
+		/* One bank */
+		tpm_buf_append_u32(&buf, 1);
+		/* Which bank to use */
+		tpm_buf_append_u16(&buf, hash);
+		/* Length of the PCR bitmask */
+		tpm_buf_append_u8(&buf, 3);
+		/* PCR bitmask */
+		for (i = 0; i < 3; i++) {
+			char tmp = 0;
+
+			for (j = 0; j < 8; j++) {
+				char bit = (i * 8) + j;
+
+				if (options->creation_pcrs & (1 << bit))
+					tmp |= (1 << j);
+			}
+			tpm_buf_append_u8(&buf, tmp);
+		}
+	} else {
+		tpm_buf_append_u32(&buf, 0);
+	}
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;
-- 
2.38.1.431.g37b22c650d-goog


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* [PATCH v4 06/11] security: keys: trusted: Verify creation data
  2022-11-03 18:01 [PATCH v4 00/11] Encrypted Hibernation Evan Green
  2022-11-03 18:01 ` [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data Evan Green
  2022-11-03 18:01 ` [PATCH v4 05/11] security: keys: trusted: Allow storage of PCR values in " Evan Green
@ 2022-11-03 18:01 ` Evan Green
  2022-11-04 18:35   ` Kees Cook
  2 siblings, 1 reply; 9+ messages in thread
From: Evan Green @ 2022-11-03 18:01 UTC (permalink / raw)
  To: linux-kernel
  Cc: corbet, linux-pm, rjw, gwendal, apronin, Pavel Machek, Kees Cook,
	Matthew Garrett, linux-integrity, jejb, zohar, dlunev,
	Eric Biggers, Ben Boeckel, jarkko, Evan Green, Matthew Garrett,
	David Howells, James Morris, Matthew Garrett, Paul Moore,
	Serge E. Hallyn, axelj, keyrings, linux-security-module

If a loaded key contains creation data, ask the TPM to verify that
creation data. This allows users like encrypted hibernate to know that
the loaded and parsed creation data has not been tampered with.

Suggested-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Evan Green <evgreen@chromium.org>

---
Source material for this change is at:
https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/

(no changes since v3)

Changes in v3:
 - Changed funky tag to suggested-by (Kees). Matthew, holler if you want
   something different.

Changes in v2:
 - Adjust hash len by 2 due to new ASN.1 storage, and add underflow
   check.

 include/linux/tpm.h                       |  1 +
 security/keys/trusted-keys/trusted_tpm2.c | 77 ++++++++++++++++++++++-
 2 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 70134e6551745f..9c2ee3e30ffa5d 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -224,6 +224,7 @@ enum tpm2_command_codes {
 	TPM2_CC_SELF_TEST	        = 0x0143,
 	TPM2_CC_STARTUP		        = 0x0144,
 	TPM2_CC_SHUTDOWN	        = 0x0145,
+	TPM2_CC_CERTIFYCREATION	        = 0x014A,
 	TPM2_CC_NV_READ                 = 0x014E,
 	TPM2_CC_CREATE		        = 0x0153,
 	TPM2_CC_LOAD		        = 0x0157,
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index a7ad83bc0e5396..c76a1b5a2e8471 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -703,6 +703,74 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	return rc;
 }
 
+/**
+ * tpm2_certify_creation() - execute a TPM2_CertifyCreation command
+ *
+ * @chip: TPM chip to use
+ * @payload: the key data in clear and encrypted form
+ * @blob_handle: the loaded TPM handle of the key
+ *
+ * Return: 0 on success
+ *         -EINVAL on tpm error status
+ *         < 0 error from tpm_send or tpm_buf_init
+ */
+static int tpm2_certify_creation(struct tpm_chip *chip,
+				 struct trusted_key_payload *payload,
+				 u32 blob_handle)
+{
+	struct tpm_header *head;
+	struct tpm_buf buf;
+	int rc;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CERTIFYCREATION);
+	if (rc)
+		return rc;
+
+	/* Use TPM_RH_NULL for signHandle */
+	tpm_buf_append_u32(&buf, 0x40000007);
+
+	/* Object handle */
+	tpm_buf_append_u32(&buf, blob_handle);
+
+	/* Auth */
+	tpm_buf_append_u32(&buf, 9);
+	tpm_buf_append_u32(&buf, TPM2_RS_PW);
+	tpm_buf_append_u16(&buf, 0);
+	tpm_buf_append_u8(&buf, 0);
+	tpm_buf_append_u16(&buf, 0);
+
+	/* Qualifying data */
+	tpm_buf_append_u16(&buf, 0);
+
+	/* Creation data hash */
+	if (payload->creation_hash_len < 2) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	tpm_buf_append_u16(&buf, payload->creation_hash_len - 2);
+	tpm_buf_append(&buf, payload->creation_hash + 2,
+		       payload->creation_hash_len - 2);
+
+	/* signature scheme */
+	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+
+	/* creation ticket */
+	tpm_buf_append(&buf, payload->tk, payload->tk_len);
+
+	rc = tpm_transmit_cmd(chip, &buf, 6, "certifying creation data");
+	if (rc)
+		goto out;
+
+	head = (struct tpm_header *)buf.data;
+
+	if (be32_to_cpu(head->return_code) != TPM2_RC_SUCCESS)
+		rc = -EINVAL;
+out:
+	tpm_buf_destroy(&buf);
+	return rc;
+}
+
 /**
  * tpm2_unseal_trusted() - unseal the payload of a trusted key
  *
@@ -728,8 +796,15 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 		goto out;
 
 	rc = tpm2_unseal_cmd(chip, payload, options, blob_handle);
-	tpm2_flush_context(chip, blob_handle);
+	if (rc)
+		goto flush;
+
+	if (payload->creation_len)
+		rc = tpm2_certify_creation(chip, payload, blob_handle);
 
+
+flush:
+	tpm2_flush_context(chip, blob_handle);
 out:
 	tpm_put_ops(chip);
 
-- 
2.38.1.431.g37b22c650d-goog


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data
  2022-11-03 18:01 ` [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data Evan Green
@ 2022-11-04 18:33   ` Kees Cook
  2022-11-07 20:11     ` Evan Green
  0 siblings, 1 reply; 9+ messages in thread
From: Kees Cook @ 2022-11-04 18:33 UTC (permalink / raw)
  To: Evan Green
  Cc: linux-kernel, corbet, linux-pm, rjw, gwendal, apronin,
	Pavel Machek, Matthew Garrett, linux-integrity, jejb, zohar,
	dlunev, Eric Biggers, Ben Boeckel, jarkko, David Howells,
	James Morris, Paul Moore, Serge E. Hallyn, keyrings,
	linux-security-module

On Thu, Nov 03, 2022 at 11:01:12AM -0700, Evan Green wrote:
> In addition to the private key and public key, the TPM2_Create
> command may also return creation data, a creation hash, and a creation
> ticket. These fields allow the TPM to attest to the contents of a
> specified set of PCRs at the time the trusted key was created. Encrypted
> hibernation will use this to ensure that PCRs settable only by the
> kernel were set properly at the time of creation, indicating this is an
> authentic hibernate key.
> 
> Encode these additional parameters into the ASN.1 created to represent
> the key blob. The new fields are made optional so that they don't bloat
> key blobs which don't need them, and to ensure interoperability with
> old blobs.
> 
> Signed-off-by: Evan Green <evgreen@chromium.org>

There's a lot of open-coded math for the bounds checking. I didn't
immediately see any problems, but it'd be nice if there was a way to
hook a fuzzer up to this, or at least write some KUnit tests to check
boundary conditions explicitly.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 05/11] security: keys: trusted: Allow storage of PCR values in creation data
  2022-11-03 18:01 ` [PATCH v4 05/11] security: keys: trusted: Allow storage of PCR values in " Evan Green
@ 2022-11-04 18:34   ` Kees Cook
  0 siblings, 0 replies; 9+ messages in thread
From: Kees Cook @ 2022-11-04 18:34 UTC (permalink / raw)
  To: Evan Green
  Cc: linux-kernel, corbet, linux-pm, rjw, gwendal, apronin,
	Pavel Machek, Matthew Garrett, linux-integrity, jejb, zohar,
	dlunev, Eric Biggers, Ben Boeckel, jarkko, Matthew Garrett,
	Matthew Garrett, Ben Boeckel, David Howells, James Morris,
	Paul Moore, Serge E. Hallyn, keyrings, linux-doc,
	linux-security-module

On Thu, Nov 03, 2022 at 11:01:13AM -0700, Evan Green wrote:
> From: Matthew Garrett <matthewgarrett@google.com>
> 
> When TPMs generate keys, they can also generate some information
> describing the state of the PCRs at creation time. This data can then
> later be certified by the TPM, allowing verification of the PCR values.
> This allows us to determine the state of the system at the time a key
> was generated. Add an additional argument to the trusted key creation
> options, allowing the user to provide the set of PCRs that should have
> their values incorporated into the creation data.
> 
> Link: https://lore.kernel.org/lkml/20210220013255.1083202-6-matthewgarrett@google.com/
> Signed-off-by: Matthew Garrett <mjg59@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 06/11] security: keys: trusted: Verify creation data
  2022-11-03 18:01 ` [PATCH v4 06/11] security: keys: trusted: Verify " Evan Green
@ 2022-11-04 18:35   ` Kees Cook
  0 siblings, 0 replies; 9+ messages in thread
From: Kees Cook @ 2022-11-04 18:35 UTC (permalink / raw)
  To: Evan Green
  Cc: linux-kernel, corbet, linux-pm, rjw, gwendal, apronin,
	Pavel Machek, Matthew Garrett, linux-integrity, jejb, zohar,
	dlunev, Eric Biggers, Ben Boeckel, jarkko, Matthew Garrett,
	David Howells, James Morris, Matthew Garrett, Paul Moore,
	Serge E. Hallyn, axelj, keyrings, linux-security-module

On Thu, Nov 03, 2022 at 11:01:14AM -0700, Evan Green wrote:
> If a loaded key contains creation data, ask the TPM to verify that
> creation data. This allows users like encrypted hibernate to know that
> the loaded and parsed creation data has not been tampered with.
> 
> Suggested-by: Matthew Garrett <mjg59@google.com>
> Signed-off-by: Evan Green <evgreen@chromium.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data
  2022-11-04 18:33   ` Kees Cook
@ 2022-11-07 20:11     ` Evan Green
  2022-11-10  0:29       ` Evan Green
  0 siblings, 1 reply; 9+ messages in thread
From: Evan Green @ 2022-11-07 20:11 UTC (permalink / raw)
  To: Kees Cook
  Cc: linux-kernel, corbet, linux-pm, rjw, gwendal, apronin,
	Pavel Machek, Matthew Garrett, linux-integrity, jejb, zohar,
	dlunev, Eric Biggers, Ben Boeckel, jarkko, David Howells,
	James Morris, Paul Moore, Serge E. Hallyn, keyrings,
	linux-security-module

On Fri, Nov 4, 2022 at 11:33 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Nov 03, 2022 at 11:01:12AM -0700, Evan Green wrote:
> > In addition to the private key and public key, the TPM2_Create
> > command may also return creation data, a creation hash, and a creation
> > ticket. These fields allow the TPM to attest to the contents of a
> > specified set of PCRs at the time the trusted key was created. Encrypted
> > hibernation will use this to ensure that PCRs settable only by the
> > kernel were set properly at the time of creation, indicating this is an
> > authentic hibernate key.
> >
> > Encode these additional parameters into the ASN.1 created to represent
> > the key blob. The new fields are made optional so that they don't bloat
> > key blobs which don't need them, and to ensure interoperability with
> > old blobs.
> >
> > Signed-off-by: Evan Green <evgreen@chromium.org>
>
> There's a lot of open-coded math for the bounds checking. I didn't
> immediately see any problems, but it'd be nice if there was a way to
> hook a fuzzer up to this, or at least write some KUnit tests to check
> boundary conditions explicitly.
>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Thank you! Yes, agreed about all the bounds checking. I could probably
pull out the "check for src + 2 > end, then get_unaligned_be16()" into
a helper function. Let me see if that makes things look better or ends
up looking the same.
-Evan

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data
  2022-11-07 20:11     ` Evan Green
@ 2022-11-10  0:29       ` Evan Green
  0 siblings, 0 replies; 9+ messages in thread
From: Evan Green @ 2022-11-10  0:29 UTC (permalink / raw)
  To: Kees Cook
  Cc: linux-kernel, corbet, linux-pm, rjw, gwendal, apronin,
	Pavel Machek, Matthew Garrett, linux-integrity, jejb, zohar,
	dlunev, Eric Biggers, Ben Boeckel, jarkko, David Howells,
	James Morris, Paul Moore, Serge E. Hallyn, keyrings,
	linux-security-module

On Mon, Nov 7, 2022 at 12:11 PM Evan Green <evgreen@chromium.org> wrote:
>
> On Fri, Nov 4, 2022 at 11:33 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Thu, Nov 03, 2022 at 11:01:12AM -0700, Evan Green wrote:
> > > In addition to the private key and public key, the TPM2_Create
> > > command may also return creation data, a creation hash, and a creation
> > > ticket. These fields allow the TPM to attest to the contents of a
> > > specified set of PCRs at the time the trusted key was created. Encrypted
> > > hibernation will use this to ensure that PCRs settable only by the
> > > kernel were set properly at the time of creation, indicating this is an
> > > authentic hibernate key.
> > >
> > > Encode these additional parameters into the ASN.1 created to represent
> > > the key blob. The new fields are made optional so that they don't bloat
> > > key blobs which don't need them, and to ensure interoperability with
> > > old blobs.
> > >
> > > Signed-off-by: Evan Green <evgreen@chromium.org>
> >
> > There's a lot of open-coded math for the bounds checking. I didn't
> > immediately see any problems, but it'd be nice if there was a way to
> > hook a fuzzer up to this, or at least write some KUnit tests to check
> > boundary conditions explicitly.
> >
> > Reviewed-by: Kees Cook <keescook@chromium.org>
>
> Thank you! Yes, agreed about all the bounds checking. I could probably
> pull out the "check for src + 2 > end, then get_unaligned_be16()" into
> a helper function. Let me see if that makes things look better or ends
> up looking the same.

A helper function cleaned this up nicely, so I'll send that in the
next spin but not yet pick up your reviewed tag.

^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2022-11-10  0:30 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-11-03 18:01 [PATCH v4 00/11] Encrypted Hibernation Evan Green
2022-11-03 18:01 ` [PATCH v4 04/11] security: keys: trusted: Include TPM2 creation data Evan Green
2022-11-04 18:33   ` Kees Cook
2022-11-07 20:11     ` Evan Green
2022-11-10  0:29       ` Evan Green
2022-11-03 18:01 ` [PATCH v4 05/11] security: keys: trusted: Allow storage of PCR values in " Evan Green
2022-11-04 18:34   ` Kees Cook
2022-11-03 18:01 ` [PATCH v4 06/11] security: keys: trusted: Verify " Evan Green
2022-11-04 18:35   ` Kees Cook

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