* [PATCH v11 0/3] Trusted Key policy for TPM 2.0
@ 2020-09-12 17:31 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:31 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This is a lockstep patch with the prior trusted key rework patch. Now
the key format is ASN.1, the policy statements needed to unseal the
key can be coded into the key file itself meaning the kernel can now
construct and use the policy session necessary rather than the user
having to do it. This makes using TPM 2.0 keys with policy much easier.
The current implementation only has a limited subset of the full TPM
2.0 policy commands, but it is enough to implement keys locked to PCR
values and expiring keys. The main missing feature is support for the
TPM2_PolicyOR statement, which means all current policy has to be AND
chains (key doesn't unlock unless every policy statement succeeds).
James
---
James Bottomley (3):
security: keys: trusted: add PCR policy to TPM2 keys
security: keys: trusted: add ability to specify arbitrary policy
security: keys: trusted: implement counter/timer policy
.../security/keys/trusted-encrypted.rst | 83 +++-
include/keys/trusted-type.h | 5 +-
include/linux/tpm.h | 6 +
security/keys/Kconfig | 2 +
security/keys/trusted-keys/Makefile | 2 +-
security/keys/trusted-keys/tpm2-policy.c | 463 ++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 31 ++
security/keys/trusted-keys/tpm2key.asn1 | 13 +
security/keys/trusted-keys/trusted_tpm1.c | 23 +-
security/keys/trusted-keys/trusted_tpm2.c | 120 ++++-
10 files changed, 733 insertions(+), 15 deletions(-)
create mode 100644 security/keys/trusted-keys/tpm2-policy.c
create mode 100644 security/keys/trusted-keys/tpm2-policy.h
--
2.26.2
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v11 0/3] Trusted Key policy for TPM 2.0
@ 2020-09-12 17:31 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:31 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This is a lockstep patch with the prior trusted key rework patch. Now
the key format is ASN.1, the policy statements needed to unseal the
key can be coded into the key file itself meaning the kernel can now
construct and use the policy session necessary rather than the user
having to do it. This makes using TPM 2.0 keys with policy much easier.
The current implementation only has a limited subset of the full TPM
2.0 policy commands, but it is enough to implement keys locked to PCR
values and expiring keys. The main missing feature is support for the
TPM2_PolicyOR statement, which means all current policy has to be AND
chains (key doesn't unlock unless every policy statement succeeds).
James
---
James Bottomley (3):
security: keys: trusted: add PCR policy to TPM2 keys
security: keys: trusted: add ability to specify arbitrary policy
security: keys: trusted: implement counter/timer policy
.../security/keys/trusted-encrypted.rst | 83 +++-
include/keys/trusted-type.h | 5 +-
include/linux/tpm.h | 6 +
security/keys/Kconfig | 2 +
security/keys/trusted-keys/Makefile | 2 +-
security/keys/trusted-keys/tpm2-policy.c | 463 ++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 31 ++
security/keys/trusted-keys/tpm2key.asn1 | 13 +
security/keys/trusted-keys/trusted_tpm1.c | 23 +-
security/keys/trusted-keys/trusted_tpm2.c | 120 ++++-
10 files changed, 733 insertions(+), 15 deletions(-)
create mode 100644 security/keys/trusted-keys/tpm2-policy.c
create mode 100644 security/keys/trusted-keys/tpm2-policy.h
--
2.26.2
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v11 0/3] Trusted Key policy for TPM 2.0
@ 2020-09-12 17:39 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This is a lockstep patch with the prior trusted key rework patch. Now
the key format is ASN.1, the policy statements needed to unseal the
key can be coded into the key file itself meaning the kernel can now
construct and use the policy session necessary rather than the user
having to do it. This makes using TPM 2.0 keys with policy much easier.
The current implementation only has a limited subset of the full TPM
2.0 policy commands, but it is enough to implement keys locked to PCR
values and expiring keys. The main missing feature is support for the
TPM2_PolicyOR statement, which means all current policy has to be AND
chains (key doesn't unlock unless every policy statement succeeds).
James
---
James Bottomley (3):
security: keys: trusted: add PCR policy to TPM2 keys
security: keys: trusted: add ability to specify arbitrary policy
security: keys: trusted: implement counter/timer policy
.../security/keys/trusted-encrypted.rst | 83 +++-
include/keys/trusted-type.h | 5 +-
include/linux/tpm.h | 6 +
security/keys/Kconfig | 2 +
security/keys/trusted-keys/Makefile | 2 +-
security/keys/trusted-keys/tpm2-policy.c | 463 ++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 31 ++
security/keys/trusted-keys/tpm2key.asn1 | 13 +
security/keys/trusted-keys/trusted_tpm1.c | 23 +-
security/keys/trusted-keys/trusted_tpm2.c | 120 ++++-
10 files changed, 733 insertions(+), 15 deletions(-)
create mode 100644 security/keys/trusted-keys/tpm2-policy.c
create mode 100644 security/keys/trusted-keys/tpm2-policy.h
--
2.26.2
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v11 0/3] Trusted Key policy for TPM 2.0
@ 2020-09-12 17:39 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This is a lockstep patch with the prior trusted key rework patch. Now
the key format is ASN.1, the policy statements needed to unseal the
key can be coded into the key file itself meaning the kernel can now
construct and use the policy session necessary rather than the user
having to do it. This makes using TPM 2.0 keys with policy much easier.
The current implementation only has a limited subset of the full TPM
2.0 policy commands, but it is enough to implement keys locked to PCR
values and expiring keys. The main missing feature is support for the
TPM2_PolicyOR statement, which means all current policy has to be AND
chains (key doesn't unlock unless every policy statement succeeds).
James
---
James Bottomley (3):
security: keys: trusted: add PCR policy to TPM2 keys
security: keys: trusted: add ability to specify arbitrary policy
security: keys: trusted: implement counter/timer policy
.../security/keys/trusted-encrypted.rst | 83 +++-
include/keys/trusted-type.h | 5 +-
include/linux/tpm.h | 6 +
security/keys/Kconfig | 2 +
security/keys/trusted-keys/Makefile | 2 +-
security/keys/trusted-keys/tpm2-policy.c | 463 ++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 31 ++
security/keys/trusted-keys/tpm2key.asn1 | 13 +
security/keys/trusted-keys/trusted_tpm1.c | 23 +-
security/keys/trusted-keys/trusted_tpm2.c | 120 ++++-
10 files changed, 733 insertions(+), 15 deletions(-)
create mode 100644 security/keys/trusted-keys/tpm2-policy.c
create mode 100644 security/keys/trusted-keys/tpm2-policy.h
--
2.26.2
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys
2020-09-12 17:39 ` James Bottomley
@ 2020-09-12 17:39 ` James Bottomley
-1 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This commit adds the ability to specify a PCR lock policy to TPM2
keys. There is a complexity in that the creator of the key must chose
either to use a PCR lock policy or to use authentication. At the
current time they can't use both due to a complexity with the way
authentication works when policy registers are in use. The way to
construct a pcrinfo statement for a key is simply to use the
TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
hash of all their values in order of ascending PCR number.
For simplicity, we require the policy name hash and the hash used for
the PCRs to be the same. Thus to construct a policy around the value
of the resettable PCR 16 using the sha1 bank, first reset the pcr to
zero giving a hash of all zeros as:
6768033e216468247bd031a0a2d9876d79818f8f
Then the TPMS_PCR_SELECT value for PCR 16 is
03000001
So create a new 32 byte key with a policy policy locking the key to
this value of PCR 16 with a parent key of 81000001 would be:
keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
v2: fix for new ASN.1 API eliminating hack in place and check lengths
v8: recover patch and fix offsets for hash and size
v9: fix cut and paste error in commit log
v10: update for kfree_sensitive()
v11: add policy to ASN.1 key format description
---
.../security/keys/trusted-encrypted.rst | 36 +-
include/keys/trusted-type.h | 5 +-
include/linux/tpm.h | 5 +
security/keys/Kconfig | 2 +
security/keys/trusted-keys/Makefile | 2 +-
security/keys/trusted-keys/tpm2-policy.c | 372 ++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 30 ++
security/keys/trusted-keys/tpm2key.asn1 | 13 +
security/keys/trusted-keys/trusted_tpm1.c | 8 +-
security/keys/trusted-keys/trusted_tpm2.c | 86 +++-
10 files changed, 545 insertions(+), 14 deletions(-)
create mode 100644 security/keys/trusted-keys/tpm2-policy.c
create mode 100644 security/keys/trusted-keys/tpm2-policy.h
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index eb639bb24fcc..8b7853a277bc 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -60,7 +60,10 @@ Usage::
(40 ascii zeros)
blobauth= ascii hex auth for sealed data default 0x00...
(40 ascii zeros)
- pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
+ pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no
+ default) on TPM 1.2 and a TPMS_PCR_SELECTION
+ coupled with a hash of all the selected PCRs on
+ TPM 2.0 using the selected hash.
pcrlock= pcr number to be extended to "lock" blob
migratable= 0|1 indicating permission to reseal to new PCR values,
default 1 (resealing allowed)
@@ -151,6 +154,20 @@ Load a trusted key from the saved blob::
f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
e4a8aea2b607ec96931e6f4d4fe563ba
+Create a trusted key on TPM 2.0 using an all zero value of PCR16 and
+using the NV storage root 81000001 as the parent::
+
+ $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u
+
+Note the TPMS_PCR_SELECT value for PCR 16 is 03000001 because all
+current TPMs have 24 PCRs, so the initial 03 says there are three
+following bytes of selection and then because the bytes are big
+endian, 16 is bit zero of byte 2. the hash is the sha1 sum of all
+zeros (the value of PCR 16)::
+
+ $ dd if=/dev/zero bs=1 count 2>/dev/null|sha1sum
+ 6768033e216468247bd031a0a2d9876d79818f8f
+
Reseal a trusted key under new pcr values::
$ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
@@ -221,11 +238,17 @@ policy::
TPMKey ::= SEQUENCE {
type OBJECT IDENTIFIER
emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
+ policy [1] EXPLICIT SEQUENCE OF TPMPolicy OPTIONAL
parent INTEGER
pubkey OCTET STRING
privkey OCTET STRING
}
+ TPMPolicy ::= SEQUENCE {
+ CommandCode [0] EXPLICIT INTEGER
+ CommandPolicy [1] EXPLICIT OCTET STRING
+ }
+
type is what distinguishes the key even in binary form since the OID
is provided by the TCG to be unique and thus forms a recognizable
binary pattern at offset 3 in the key. The OIDs currently made
@@ -251,6 +274,17 @@ is false or not present, the key requires an explicit authorization
phrase. This is used by most user space consumers to decide whether
to prompt for a password.
+policy represents a sequence of one or more policy statements that
+must be executed successfully into a session policy register. If
+policy isn't present then no policy is required to unlock the key, but
+if it is, commandCode is the TPM 2.0 command code of the policy
+instruction that must be executed and CommandPolicy represents the
+binary parameter area of the policy command.
+
+Note that the current sequential execution requirement means that only
+AND based policy can be constructed at the moment, so TPM2_PolicyOR is
+not currently supported.
+
parent represents the parent key handle, either in the 0x81 MSO space,
like 0x81000001 for the RSA primary storage key. Userspace programmes
also support specifying the primary handle in the 0x40 MSO space. If
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index b2d87ad21714..c117bf598230 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -14,9 +14,11 @@
#define MIN_KEY_SIZE 32
#define MAX_KEY_SIZE 128
#define MAX_BLOB_SIZE 512
-#define MAX_PCRINFO_SIZE 64
+#define MAX_PCRINFO_SIZE 128
#define MAX_DIGEST_SIZE 64
+#define TPM2_MAX_POLICIES 16
+
struct trusted_key_payload {
struct rcu_head rcu;
unsigned int key_len;
@@ -25,6 +27,7 @@ struct trusted_key_payload {
unsigned char old_format;
unsigned char key[MAX_KEY_SIZE + 1];
unsigned char blob[MAX_BLOB_SIZE];
+ struct tpm2_policies *policies;
};
struct trusted_key_options {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 35224860fd0c..254c33086288 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -230,10 +230,14 @@ enum tpm2_command_codes {
TPM2_CC_CONTEXT_LOAD = 0x0161,
TPM2_CC_CONTEXT_SAVE = 0x0162,
TPM2_CC_FLUSH_CONTEXT = 0x0165,
+ TPM2_CC_POLICY_AUTHVALUE = 0x016B,
+ TPM2_CC_POLICY_COUNTER_TIMER = 0x016D,
+ TPM2_CC_START_AUTH_SESS = 0x0176,
TPM2_CC_VERIFY_SIGNATURE = 0x0177,
TPM2_CC_GET_CAPABILITY = 0x017A,
TPM2_CC_GET_RANDOM = 0x017B,
TPM2_CC_PCR_READ = 0x017E,
+ TPM2_CC_POLICY_PCR = 0x017F,
TPM2_CC_PCR_EXTEND = 0x0182,
TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
TPM2_CC_HASH_SEQUENCE_START = 0x0186,
@@ -242,6 +246,7 @@ enum tpm2_command_codes {
};
enum tpm2_permanent_handles {
+ TPM2_RH_NULL = 0x40000007,
TPM2_RS_PW = 0x40000009,
};
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index 8fbfedf6d1cc..d9977359b8a6 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -74,6 +74,8 @@ config TRUSTED_KEYS
select CRYPTO
select CRYPTO_HMAC
select CRYPTO_SHA1
+ select CRYPTO_SHA256
+ select CRYPTO_SHA512
select CRYPTO_HASH_INFO
select ASN1_ENCODER
help
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index e0198641eff2..194febacf362 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,4 @@
obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
trusted-y += trusted_tpm1.o
-trusted-y += trusted_tpm2.o tpm2key.asn1.o
+trusted-y += trusted_tpm2.o tpm2key.asn1.o tpm2-policy.o
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
new file mode 100644
index 000000000000..080a76e879fd
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/err.h>
+#include <linux/types.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+#include <linux/tpm.h>
+
+#include <asm/unaligned.h>
+
+#include <crypto/hash.h>
+
+#include <keys/trusted-type.h>
+#include <keys/trusted_tpm.h>
+
+#include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
+
+int tpm2_key_code(void *context, size_t hdrlen,
+ unsigned char tag,
+ const void *value, size_t vlen)
+{
+ struct tpm2_key_context *ctx = context;
+ u32 code = 0;
+ const u8 *v = value;
+ int i;
+
+ for (i = 0; i < vlen; i++) {
+ code <<= 8;
+ code |= v[i];
+ }
+
+ ctx->policy_code[ctx->policy_count] = code;
+
+ return 0;
+}
+
+int tpm2_key_policy(void *context, size_t hdrlen,
+ unsigned char tag,
+ const void *value, size_t vlen)
+{
+ struct tpm2_key_context *ctx = context;
+
+ ctx->policies[ctx->policy_count] = value;
+ ctx->policy_len[ctx->policy_count++] = vlen;
+
+ return 0;
+}
+
+/* we only support a limited number of policy statement so
+ * make sure we don't have anything we can't support
+ */
+static int tpm2_validate_policy(struct tpm2_policies *pols)
+{
+ int i;
+
+ if (pols->count = 0)
+ return 0;
+
+ for (i = 0; i < pols->count; i++) {
+ switch (pols->code[i]) {
+ case TPM2_CC_POLICY_COUNTER_TIMER:
+ case TPM2_CC_POLICY_PCR:
+ case TPM2_CC_POLICY_AUTHVALUE:
+ break;
+ default:
+ printk(KERN_INFO "tpm2 policy 0x%x is unsupported",
+ pols->code[i]);
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * tpm2_key_process_policy - collect the policty from the context
+ * @ctx: the context to collect from
+ * @payload: the payload structure to place it in
+ *
+ * THis function sizes the policy statements and allocates space
+ * within the payload to receive them before copying them over. It
+ * should be used after the ber decoder has completed successfully
+ */
+int tpm2_key_policy_process(struct tpm2_key_context *ctx,
+ struct trusted_key_payload *payload)
+{
+ int tot_len = 0;
+ u8 *buf;
+ int i, ret, len = 0;
+ struct tpm2_policies *pols;
+
+ if (ctx->policy_count = 0)
+ return 0;
+
+ for (i = 0; i < ctx->policy_count; i++)
+ tot_len += ctx->policy_len[i];
+ tot_len += sizeof(*pols);
+
+ pols = kmalloc(tot_len, GFP_KERNEL);
+ if (!pols)
+ return -ENOMEM;
+
+ payload->policies = pols;
+ buf = (u8 *)(pols + 1);
+
+ for (i = 0; i < ctx->policy_count; i++) {
+ pols->policies[i] = &buf[len];
+ pols->len[i] = ctx->policy_len[i];
+ pols->code[i] = ctx->policy_code[i];
+ if (pols->len[i])
+ memcpy(pols->policies[i], ctx->policies[i],
+ ctx->policy_len[i]);
+ len += ctx->policy_len[i];
+ }
+ pols->count = ctx->policy_count;
+
+ ret = tpm2_validate_policy(pols);
+ if (ret) {
+ kfree(pols);
+ payload->policies = NULL;
+ }
+
+ /* capture the hash and size */
+
+ /* the hash is the second algorithm */
+ pols->hash = get_unaligned_be16(&ctx->pub[4]);
+ /* and the digest appears after the attributes */
+ pols->hash_size = get_unaligned_be16(&ctx->pub[10]);
+
+ return ret;
+}
+
+int tpm2_generate_policy_digest(struct tpm2_policies *pols,
+ u32 hash, u8 *policydigest, u32 *plen)
+{
+ int i;
+ struct crypto_shash *tfm;
+ int rc;
+
+ if (pols->count = 0)
+ return 0;
+
+ tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
+ if (IS_ERR(tfm))
+ return PTR_ERR(tfm);
+
+ rc = crypto_shash_digestsize(tfm);
+ if (WARN(rc > MAX_DIGEST_SIZE,
+ "BUG: trusted key code has alg %s with digest too large (%d)",
+ hash_algo_name[hash], rc)) {
+ rc = -EINVAL;
+ goto err;
+ }
+
+ pols->hash = hash;
+ pols->hash_size = rc;
+ *plen = rc;
+
+ /* policy digests always start out all zeros */
+ memset(policydigest, 0, rc);
+
+ for (i = 0; i < pols->count; i++) {
+ u8 *policy = pols->policies[i];
+ int len = pols->len[i];
+ u32 cmd = pols->code[i];
+ u8 digest[MAX_DIGEST_SIZE];
+ u8 code[4];
+ SHASH_DESC_ON_STACK(sdesc, tfm);
+
+ sdesc->tfm = tfm;
+ rc = crypto_shash_init(sdesc);
+ if (rc)
+ goto err;
+
+ /* first hash the previous digest */
+ crypto_shash_update(sdesc, policydigest, *plen);
+
+ /* then hash the command code */
+ put_unaligned_be32(cmd, code);
+ crypto_shash_update(sdesc, code, 4);
+
+ /* commands that need special handling */
+ if (cmd = TPM2_CC_POLICY_COUNTER_TIMER) {
+ SHASH_DESC_ON_STACK(sdesc1, tfm);
+
+ sdesc1->tfm = tfm;
+
+ /* counter timer policies are double hashed */
+ crypto_shash_digest(sdesc1, policy, len,
+ digest);
+ policy = digest;
+ len = *plen;
+ }
+
+ crypto_shash_update(sdesc, policy, len);
+
+ /* now output the intermediate to the policydigest */
+ crypto_shash_final(sdesc, policydigest);
+
+ }
+ rc = 0;
+
+ err:
+ crypto_free_shash(tfm);
+ return rc;
+}
+
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len)
+{
+ const int SCRATCH_SIZE = PAGE_SIZE;
+ u8 *buf = kmalloc(2 * SCRATCH_SIZE, GFP_KERNEL);
+ u8 *work = buf + SCRATCH_SIZE;
+ u8 *ptr;
+ u8 *end_work = work + SCRATCH_SIZE;
+ int i, ret;
+
+ if (!buf)
+ return -ENOMEM;
+
+ for (i = 0; i < pols->count; i++) {
+ u8 *seq, *tag;
+ u32 cmd = pols->code[i];
+
+ if (WARN(work - buf + 14 + pols->len[i] > 2 * SCRATCH_SIZE,
+ "BUG: scratch buffer is too small"))
+ return -EINVAL;
+
+ work = asn1_encode_sequence(work, end_work, NULL, -1);
+ seq = work;
+
+ work = asn1_encode_tag(work, end_work, 0, NULL, -1);
+ tag = work;
+
+ work = asn1_encode_integer(work, end_work, cmd);
+ asn1_encode_tag(tag, end_work, 0, NULL, work - tag);
+
+ work = asn1_encode_tag(work, end_work, 1, NULL, -1);
+ tag = work;
+
+ work = asn1_encode_octet_string(work, end_work,
+ pols->policies[i],
+ pols->len[i]);
+
+ asn1_encode_tag(tag, end_work, 1, NULL, work - tag);
+
+ seq = asn1_encode_sequence(seq, end_work, NULL, work - seq);
+ if (IS_ERR(seq)) {
+ ret = PTR_ERR(seq);
+ goto err;
+ }
+ }
+ ptr = asn1_encode_sequence(buf, buf + SCRATCH_SIZE, buf + PAGE_SIZE,
+ work - buf - PAGE_SIZE);
+ if (IS_ERR(ptr)) {
+ ret = PTR_ERR(ptr);
+ goto err;
+ }
+
+ *data = buf;
+ *len = ptr - buf;
+
+ return 0;
+
+ err:
+ kfree(buf);
+ return ret;
+}
+
+int tpm2_start_policy_session(struct tpm_chip *chip, u16 hash, u32 *handle)
+{
+ struct tpm_buf buf;
+ int rc;
+ int i;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
+ if (rc)
+ return rc;
+
+ /* NULL salt key handle */
+ tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+
+ /* NULL bind key handle */
+ tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+
+ /* empty nonce caller */
+ tpm_buf_append_u16(&buf, 20);
+ for (i = 0; i < 20; i++)
+ tpm_buf_append_u8(&buf, 0);
+
+ /* empty auth */
+ tpm_buf_append_u16(&buf, 0);
+
+ /* session type policy */
+ tpm_buf_append_u8(&buf, 0x01);
+
+ /* symmetric encryption parameters */
+
+ /* symmetric algorithm */
+ tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+
+ /* hash algorithm for session */
+ tpm_buf_append_u16(&buf, hash);
+
+ rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+ if (rc)
+ goto out;
+
+ *handle = get_unaligned_be32(buf.data + TPM_HEADER_SIZE);
+
+ out:
+ tpm_buf_destroy(&buf);
+
+ return rc <= 0 ? rc : -EPERM;
+}
+
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+ u32 *handle)
+{
+ int i, rc;
+ const char *failure;
+
+ rc = tpm2_start_policy_session(chip, pols->hash, handle);
+ if (rc)
+ return rc;
+
+ for (i = 0; i < pols->count; i++) {
+ u32 cmd = pols->code[i];
+ struct tpm_buf buf;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
+ if (rc)
+ return rc;
+
+ tpm_buf_append_u32(&buf, *handle);
+
+ switch (cmd) {
+ case TPM2_CC_POLICY_PCR:
+ failure = "PCR";
+ /*
+ * for reasons best known to the TCG we have
+ * to reverse the two arguments to send to the
+ * policy command
+ */
+ tpm_buf_append_u16(&buf, pols->hash_size);
+ tpm_buf_append(&buf, pols->policies[i] + pols->len[i] -
+ pols->hash_size, pols->hash_size);
+ tpm_buf_append(&buf, pols->policies[i],
+ pols->len[i] - pols->hash_size);
+ break;
+ default:
+ failure = "unknown policy";
+ break;
+ }
+
+ rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+ tpm_buf_destroy(&buf);
+ if (rc) {
+ printk(KERN_NOTICE "TPM policy %s failed, rc=%d\n",
+ failure, rc);
+ tpm2_flush_context(chip, *handle);
+ *handle = 0;
+ return -EPERM;
+ }
+ }
+
+ return 0;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
new file mode 100644
index 000000000000..46bf1f0a9325
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+struct tpm2_key_context {
+ u32 parent;
+ const u8 *pub;
+ u32 pub_len;
+ const u8 *priv;
+ u32 priv_len;
+ const u8 *policies[TPM2_MAX_POLICIES];
+ u32 policy_code[TPM2_MAX_POLICIES];
+ u16 policy_len[TPM2_MAX_POLICIES];
+ u8 policy_count;
+};
+
+struct tpm2_policies {
+ u32 code[TPM2_MAX_POLICIES];
+ u8 *policies[TPM2_MAX_POLICIES];
+ u16 len[TPM2_MAX_POLICIES];
+ u8 count;
+ u16 hash;
+ u16 hash_size;
+};
+
+int tpm2_key_policy_process(struct tpm2_key_context *ctx,
+ struct trusted_key_payload *payload);
+int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
+ u8 *policydigest, u32 *plen);
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+ u32 *handle);
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
index 3f6a9d01d1e5..0c241d000120 100644
--- a/security/keys/trusted-keys/tpm2key.asn1
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -1,11 +1,24 @@
---
--- ASN.1 for for TPM 2.0 keys
---
+--- Note: This isn't quite the definition in the standard
+--- However, the Linux asn.1 parser doesn't understand
+--- [2] EXPLICIT SEQUENCE OF OPTIONAL
+--- So there's an extra intermediate TPMPolicySequence
+--- definition to work around this
TPMKey ::= SEQUENCE {
type OBJECT IDENTIFIER ({tpm2_key_type}),
emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL,
+ policy [1] EXPLICIT TPMPolicySequence OPTIONAL,
parent INTEGER ({tpm2_key_parent}),
pubkey OCTET STRING ({tpm2_key_pub}),
privkey OCTET STRING ({tpm2_key_priv})
}
+
+TPMPolicySequence ::= SEQUENCE OF TPMPolicy
+
+TPMPolicy ::= SEQUENCE {
+ commandCode [0] EXPLICIT INTEGER ({tpm2_key_code}),
+ commandPolicy [1] EXPLICIT OCTET STRING ({tpm2_key_policy})
+ }
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 0f026656d635..2f62db74e771 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -1065,6 +1065,8 @@ static void trusted_rcu_free(struct rcu_head *rcu)
struct trusted_key_payload *p;
p = container_of(rcu, struct trusted_key_payload, rcu);
+
+ kfree_sensitive(p->policies);
kfree_sensitive(p);
}
@@ -1174,7 +1176,11 @@ static long trusted_read(const struct key *key, char *buffer,
*/
static void trusted_destroy(struct key *key)
{
- kfree_sensitive(key->payload.data[0]);
+ struct trusted_key_payload *p;
+
+ p = key->payload.data[0];
+ kfree_sensitive(p->policies);
+ kfree_sensitive(p);
}
struct key_type key_type_trusted = {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 905c5ca4d51c..98c65431ca75 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -17,6 +17,7 @@
#include <asm/unaligned.h>
#include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
static struct tpm2_hash tpm2_hash_map[] = {
{HASH_ALGO_SHA1, TPM_ALG_SHA1},
@@ -62,6 +63,21 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
}
+ if (payload->policies) {
+ u8 *encoded_pols;
+ u32 encoded_pol_len;
+ int ret;
+
+ ret = tpm2_encode_policy(payload->policies, &encoded_pols,
+ &encoded_pol_len);
+ if (ret)
+ return ret;
+
+ work = asn1_encode_tag(work, end_work, 1, encoded_pols,
+ encoded_pol_len);
+ kfree(encoded_pols);
+ }
+
/*
* Assume both octet strings will encode to a 2 byte definite length
*
@@ -85,14 +101,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
return work1 - payload->blob;
}
-struct tpm2_key_context {
- u32 parent;
- const u8 *pub;
- u32 pub_len;
- const u8 *priv;
- u32 priv_len;
-};
-
static int tpm2_key_decode(struct trusted_key_payload *payload,
struct trusted_key_options *options,
u8 **buf)
@@ -115,6 +123,12 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
if (!blob)
return -ENOMEM;
+ ret = tpm2_key_policy_process(&ctx, payload);
+ if (ret) {
+ kfree(blob);
+ return ret;
+ }
+
*buf = blob;
options->keyhandle = ctx.parent;
@@ -248,6 +262,42 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
if (!options->keyhandle)
return -EINVAL;
+ if (options->pcrinfo_len != 0) {
+ struct tpm2_policies *pols;
+ static u8 *scratch;
+ /* 4 array len, 2 hash alg */
+ const int len = 4 + 2 + options->pcrinfo_len;
+
+ pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
+ if (!pols)
+ return -ENOMEM;
+
+ pols->count = 1;
+ pols->len[0] = len;
+ scratch = (u8 *)(pols + 1);
+ pols->policies[0] = scratch;
+ pols->code[0] = TPM2_CC_POLICY_PCR;
+
+ put_unaligned_be32(1, &scratch[0]);
+ put_unaligned_be16(hash, &scratch[4]);
+ memcpy(&scratch[6], options->pcrinfo, options->pcrinfo_len);
+ payload->policies = pols;
+ }
+
+ if (options->policydigest_len != 0 && payload->policies) {
+ /* can't specify both a digest and a policy */
+ return -EINVAL;
+ }
+
+ if (payload->policies) {
+ rc = tpm2_generate_policy_digest(payload->policies,
+ options->hash,
+ options->policydigest,
+ &options->policydigest_len);
+ if (rc)
+ return rc;
+ }
+
rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
if (rc)
return rc;
@@ -456,21 +506,37 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
u16 data_len;
u8 *data;
int rc;
+ u32 policyhandle;
+
+ if (payload->policies && options->policyhandle)
+ /* can't have both a passed in policy and a key resident one */
+ return -EINVAL;
rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
if (rc)
return rc;
+ if (payload->policies) {
+ rc = tpm2_get_policy_session(chip, payload->policies,
+ &policyhandle);
+ if (rc)
+ return rc;
+ } else {
+ policyhandle = options->policyhandle;
+ }
+
tpm_buf_append_u32(&buf, blob_handle);
tpm2_buf_append_auth(&buf,
- options->policyhandle ?
- options->policyhandle : TPM2_RS_PW,
+ policyhandle ?
+ policyhandle : TPM2_RS_PW,
NULL /* nonce */, 0,
TPM2_SA_CONTINUE_SESSION,
options->blobauth /* hmac */,
options->blobauth_len);
rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+ if (payload->policies)
+ tpm2_flush_context(chip, policyhandle);
if (rc > 0)
rc = -EPERM;
--
2.26.2
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys
@ 2020-09-12 17:39 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This commit adds the ability to specify a PCR lock policy to TPM2
keys. There is a complexity in that the creator of the key must chose
either to use a PCR lock policy or to use authentication. At the
current time they can't use both due to a complexity with the way
authentication works when policy registers are in use. The way to
construct a pcrinfo statement for a key is simply to use the
TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
hash of all their values in order of ascending PCR number.
For simplicity, we require the policy name hash and the hash used for
the PCRs to be the same. Thus to construct a policy around the value
of the resettable PCR 16 using the sha1 bank, first reset the pcr to
zero giving a hash of all zeros as:
6768033e216468247bd031a0a2d9876d79818f8f
Then the TPMS_PCR_SELECT value for PCR 16 is
03000001
So create a new 32 byte key with a policy policy locking the key to
this value of PCR 16 with a parent key of 81000001 would be:
keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
v2: fix for new ASN.1 API eliminating hack in place and check lengths
v8: recover patch and fix offsets for hash and size
v9: fix cut and paste error in commit log
v10: update for kfree_sensitive()
v11: add policy to ASN.1 key format description
---
.../security/keys/trusted-encrypted.rst | 36 +-
include/keys/trusted-type.h | 5 +-
include/linux/tpm.h | 5 +
security/keys/Kconfig | 2 +
security/keys/trusted-keys/Makefile | 2 +-
security/keys/trusted-keys/tpm2-policy.c | 372 ++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 30 ++
security/keys/trusted-keys/tpm2key.asn1 | 13 +
security/keys/trusted-keys/trusted_tpm1.c | 8 +-
security/keys/trusted-keys/trusted_tpm2.c | 86 +++-
10 files changed, 545 insertions(+), 14 deletions(-)
create mode 100644 security/keys/trusted-keys/tpm2-policy.c
create mode 100644 security/keys/trusted-keys/tpm2-policy.h
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index eb639bb24fcc..8b7853a277bc 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -60,7 +60,10 @@ Usage::
(40 ascii zeros)
blobauth= ascii hex auth for sealed data default 0x00...
(40 ascii zeros)
- pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
+ pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no
+ default) on TPM 1.2 and a TPMS_PCR_SELECTION
+ coupled with a hash of all the selected PCRs on
+ TPM 2.0 using the selected hash.
pcrlock= pcr number to be extended to "lock" blob
migratable= 0|1 indicating permission to reseal to new PCR values,
default 1 (resealing allowed)
@@ -151,6 +154,20 @@ Load a trusted key from the saved blob::
f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
e4a8aea2b607ec96931e6f4d4fe563ba
+Create a trusted key on TPM 2.0 using an all zero value of PCR16 and
+using the NV storage root 81000001 as the parent::
+
+ $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u
+
+Note the TPMS_PCR_SELECT value for PCR 16 is 03000001 because all
+current TPMs have 24 PCRs, so the initial 03 says there are three
+following bytes of selection and then because the bytes are big
+endian, 16 is bit zero of byte 2. the hash is the sha1 sum of all
+zeros (the value of PCR 16)::
+
+ $ dd if=/dev/zero bs=1 count=20 2>/dev/null|sha1sum
+ 6768033e216468247bd031a0a2d9876d79818f8f
+
Reseal a trusted key under new pcr values::
$ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
@@ -221,11 +238,17 @@ policy::
TPMKey ::= SEQUENCE {
type OBJECT IDENTIFIER
emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
+ policy [1] EXPLICIT SEQUENCE OF TPMPolicy OPTIONAL
parent INTEGER
pubkey OCTET STRING
privkey OCTET STRING
}
+ TPMPolicy ::= SEQUENCE {
+ CommandCode [0] EXPLICIT INTEGER
+ CommandPolicy [1] EXPLICIT OCTET STRING
+ }
+
type is what distinguishes the key even in binary form since the OID
is provided by the TCG to be unique and thus forms a recognizable
binary pattern at offset 3 in the key. The OIDs currently made
@@ -251,6 +274,17 @@ is false or not present, the key requires an explicit authorization
phrase. This is used by most user space consumers to decide whether
to prompt for a password.
+policy represents a sequence of one or more policy statements that
+must be executed successfully into a session policy register. If
+policy isn't present then no policy is required to unlock the key, but
+if it is, commandCode is the TPM 2.0 command code of the policy
+instruction that must be executed and CommandPolicy represents the
+binary parameter area of the policy command.
+
+Note that the current sequential execution requirement means that only
+AND based policy can be constructed at the moment, so TPM2_PolicyOR is
+not currently supported.
+
parent represents the parent key handle, either in the 0x81 MSO space,
like 0x81000001 for the RSA primary storage key. Userspace programmes
also support specifying the primary handle in the 0x40 MSO space. If
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index b2d87ad21714..c117bf598230 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -14,9 +14,11 @@
#define MIN_KEY_SIZE 32
#define MAX_KEY_SIZE 128
#define MAX_BLOB_SIZE 512
-#define MAX_PCRINFO_SIZE 64
+#define MAX_PCRINFO_SIZE 128
#define MAX_DIGEST_SIZE 64
+#define TPM2_MAX_POLICIES 16
+
struct trusted_key_payload {
struct rcu_head rcu;
unsigned int key_len;
@@ -25,6 +27,7 @@ struct trusted_key_payload {
unsigned char old_format;
unsigned char key[MAX_KEY_SIZE + 1];
unsigned char blob[MAX_BLOB_SIZE];
+ struct tpm2_policies *policies;
};
struct trusted_key_options {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 35224860fd0c..254c33086288 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -230,10 +230,14 @@ enum tpm2_command_codes {
TPM2_CC_CONTEXT_LOAD = 0x0161,
TPM2_CC_CONTEXT_SAVE = 0x0162,
TPM2_CC_FLUSH_CONTEXT = 0x0165,
+ TPM2_CC_POLICY_AUTHVALUE = 0x016B,
+ TPM2_CC_POLICY_COUNTER_TIMER = 0x016D,
+ TPM2_CC_START_AUTH_SESS = 0x0176,
TPM2_CC_VERIFY_SIGNATURE = 0x0177,
TPM2_CC_GET_CAPABILITY = 0x017A,
TPM2_CC_GET_RANDOM = 0x017B,
TPM2_CC_PCR_READ = 0x017E,
+ TPM2_CC_POLICY_PCR = 0x017F,
TPM2_CC_PCR_EXTEND = 0x0182,
TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
TPM2_CC_HASH_SEQUENCE_START = 0x0186,
@@ -242,6 +246,7 @@ enum tpm2_command_codes {
};
enum tpm2_permanent_handles {
+ TPM2_RH_NULL = 0x40000007,
TPM2_RS_PW = 0x40000009,
};
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index 8fbfedf6d1cc..d9977359b8a6 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -74,6 +74,8 @@ config TRUSTED_KEYS
select CRYPTO
select CRYPTO_HMAC
select CRYPTO_SHA1
+ select CRYPTO_SHA256
+ select CRYPTO_SHA512
select CRYPTO_HASH_INFO
select ASN1_ENCODER
help
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index e0198641eff2..194febacf362 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,4 @@
obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
trusted-y += trusted_tpm1.o
-trusted-y += trusted_tpm2.o tpm2key.asn1.o
+trusted-y += trusted_tpm2.o tpm2key.asn1.o tpm2-policy.o
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
new file mode 100644
index 000000000000..080a76e879fd
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/err.h>
+#include <linux/types.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+#include <linux/tpm.h>
+
+#include <asm/unaligned.h>
+
+#include <crypto/hash.h>
+
+#include <keys/trusted-type.h>
+#include <keys/trusted_tpm.h>
+
+#include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
+
+int tpm2_key_code(void *context, size_t hdrlen,
+ unsigned char tag,
+ const void *value, size_t vlen)
+{
+ struct tpm2_key_context *ctx = context;
+ u32 code = 0;
+ const u8 *v = value;
+ int i;
+
+ for (i = 0; i < vlen; i++) {
+ code <<= 8;
+ code |= v[i];
+ }
+
+ ctx->policy_code[ctx->policy_count] = code;
+
+ return 0;
+}
+
+int tpm2_key_policy(void *context, size_t hdrlen,
+ unsigned char tag,
+ const void *value, size_t vlen)
+{
+ struct tpm2_key_context *ctx = context;
+
+ ctx->policies[ctx->policy_count] = value;
+ ctx->policy_len[ctx->policy_count++] = vlen;
+
+ return 0;
+}
+
+/* we only support a limited number of policy statement so
+ * make sure we don't have anything we can't support
+ */
+static int tpm2_validate_policy(struct tpm2_policies *pols)
+{
+ int i;
+
+ if (pols->count == 0)
+ return 0;
+
+ for (i = 0; i < pols->count; i++) {
+ switch (pols->code[i]) {
+ case TPM2_CC_POLICY_COUNTER_TIMER:
+ case TPM2_CC_POLICY_PCR:
+ case TPM2_CC_POLICY_AUTHVALUE:
+ break;
+ default:
+ printk(KERN_INFO "tpm2 policy 0x%x is unsupported",
+ pols->code[i]);
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * tpm2_key_process_policy - collect the policty from the context
+ * @ctx: the context to collect from
+ * @payload: the payload structure to place it in
+ *
+ * THis function sizes the policy statements and allocates space
+ * within the payload to receive them before copying them over. It
+ * should be used after the ber decoder has completed successfully
+ */
+int tpm2_key_policy_process(struct tpm2_key_context *ctx,
+ struct trusted_key_payload *payload)
+{
+ int tot_len = 0;
+ u8 *buf;
+ int i, ret, len = 0;
+ struct tpm2_policies *pols;
+
+ if (ctx->policy_count == 0)
+ return 0;
+
+ for (i = 0; i < ctx->policy_count; i++)
+ tot_len += ctx->policy_len[i];
+ tot_len += sizeof(*pols);
+
+ pols = kmalloc(tot_len, GFP_KERNEL);
+ if (!pols)
+ return -ENOMEM;
+
+ payload->policies = pols;
+ buf = (u8 *)(pols + 1);
+
+ for (i = 0; i < ctx->policy_count; i++) {
+ pols->policies[i] = &buf[len];
+ pols->len[i] = ctx->policy_len[i];
+ pols->code[i] = ctx->policy_code[i];
+ if (pols->len[i])
+ memcpy(pols->policies[i], ctx->policies[i],
+ ctx->policy_len[i]);
+ len += ctx->policy_len[i];
+ }
+ pols->count = ctx->policy_count;
+
+ ret = tpm2_validate_policy(pols);
+ if (ret) {
+ kfree(pols);
+ payload->policies = NULL;
+ }
+
+ /* capture the hash and size */
+
+ /* the hash is the second algorithm */
+ pols->hash = get_unaligned_be16(&ctx->pub[4]);
+ /* and the digest appears after the attributes */
+ pols->hash_size = get_unaligned_be16(&ctx->pub[10]);
+
+ return ret;
+}
+
+int tpm2_generate_policy_digest(struct tpm2_policies *pols,
+ u32 hash, u8 *policydigest, u32 *plen)
+{
+ int i;
+ struct crypto_shash *tfm;
+ int rc;
+
+ if (pols->count == 0)
+ return 0;
+
+ tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
+ if (IS_ERR(tfm))
+ return PTR_ERR(tfm);
+
+ rc = crypto_shash_digestsize(tfm);
+ if (WARN(rc > MAX_DIGEST_SIZE,
+ "BUG: trusted key code has alg %s with digest too large (%d)",
+ hash_algo_name[hash], rc)) {
+ rc = -EINVAL;
+ goto err;
+ }
+
+ pols->hash = hash;
+ pols->hash_size = rc;
+ *plen = rc;
+
+ /* policy digests always start out all zeros */
+ memset(policydigest, 0, rc);
+
+ for (i = 0; i < pols->count; i++) {
+ u8 *policy = pols->policies[i];
+ int len = pols->len[i];
+ u32 cmd = pols->code[i];
+ u8 digest[MAX_DIGEST_SIZE];
+ u8 code[4];
+ SHASH_DESC_ON_STACK(sdesc, tfm);
+
+ sdesc->tfm = tfm;
+ rc = crypto_shash_init(sdesc);
+ if (rc)
+ goto err;
+
+ /* first hash the previous digest */
+ crypto_shash_update(sdesc, policydigest, *plen);
+
+ /* then hash the command code */
+ put_unaligned_be32(cmd, code);
+ crypto_shash_update(sdesc, code, 4);
+
+ /* commands that need special handling */
+ if (cmd == TPM2_CC_POLICY_COUNTER_TIMER) {
+ SHASH_DESC_ON_STACK(sdesc1, tfm);
+
+ sdesc1->tfm = tfm;
+
+ /* counter timer policies are double hashed */
+ crypto_shash_digest(sdesc1, policy, len,
+ digest);
+ policy = digest;
+ len = *plen;
+ }
+
+ crypto_shash_update(sdesc, policy, len);
+
+ /* now output the intermediate to the policydigest */
+ crypto_shash_final(sdesc, policydigest);
+
+ }
+ rc = 0;
+
+ err:
+ crypto_free_shash(tfm);
+ return rc;
+}
+
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len)
+{
+ const int SCRATCH_SIZE = PAGE_SIZE;
+ u8 *buf = kmalloc(2 * SCRATCH_SIZE, GFP_KERNEL);
+ u8 *work = buf + SCRATCH_SIZE;
+ u8 *ptr;
+ u8 *end_work = work + SCRATCH_SIZE;
+ int i, ret;
+
+ if (!buf)
+ return -ENOMEM;
+
+ for (i = 0; i < pols->count; i++) {
+ u8 *seq, *tag;
+ u32 cmd = pols->code[i];
+
+ if (WARN(work - buf + 14 + pols->len[i] > 2 * SCRATCH_SIZE,
+ "BUG: scratch buffer is too small"))
+ return -EINVAL;
+
+ work = asn1_encode_sequence(work, end_work, NULL, -1);
+ seq = work;
+
+ work = asn1_encode_tag(work, end_work, 0, NULL, -1);
+ tag = work;
+
+ work = asn1_encode_integer(work, end_work, cmd);
+ asn1_encode_tag(tag, end_work, 0, NULL, work - tag);
+
+ work = asn1_encode_tag(work, end_work, 1, NULL, -1);
+ tag = work;
+
+ work = asn1_encode_octet_string(work, end_work,
+ pols->policies[i],
+ pols->len[i]);
+
+ asn1_encode_tag(tag, end_work, 1, NULL, work - tag);
+
+ seq = asn1_encode_sequence(seq, end_work, NULL, work - seq);
+ if (IS_ERR(seq)) {
+ ret = PTR_ERR(seq);
+ goto err;
+ }
+ }
+ ptr = asn1_encode_sequence(buf, buf + SCRATCH_SIZE, buf + PAGE_SIZE,
+ work - buf - PAGE_SIZE);
+ if (IS_ERR(ptr)) {
+ ret = PTR_ERR(ptr);
+ goto err;
+ }
+
+ *data = buf;
+ *len = ptr - buf;
+
+ return 0;
+
+ err:
+ kfree(buf);
+ return ret;
+}
+
+int tpm2_start_policy_session(struct tpm_chip *chip, u16 hash, u32 *handle)
+{
+ struct tpm_buf buf;
+ int rc;
+ int i;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
+ if (rc)
+ return rc;
+
+ /* NULL salt key handle */
+ tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+
+ /* NULL bind key handle */
+ tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+
+ /* empty nonce caller */
+ tpm_buf_append_u16(&buf, 20);
+ for (i = 0; i < 20; i++)
+ tpm_buf_append_u8(&buf, 0);
+
+ /* empty auth */
+ tpm_buf_append_u16(&buf, 0);
+
+ /* session type policy */
+ tpm_buf_append_u8(&buf, 0x01);
+
+ /* symmetric encryption parameters */
+
+ /* symmetric algorithm */
+ tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+
+ /* hash algorithm for session */
+ tpm_buf_append_u16(&buf, hash);
+
+ rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+ if (rc)
+ goto out;
+
+ *handle = get_unaligned_be32(buf.data + TPM_HEADER_SIZE);
+
+ out:
+ tpm_buf_destroy(&buf);
+
+ return rc <= 0 ? rc : -EPERM;
+}
+
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+ u32 *handle)
+{
+ int i, rc;
+ const char *failure;
+
+ rc = tpm2_start_policy_session(chip, pols->hash, handle);
+ if (rc)
+ return rc;
+
+ for (i = 0; i < pols->count; i++) {
+ u32 cmd = pols->code[i];
+ struct tpm_buf buf;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
+ if (rc)
+ return rc;
+
+ tpm_buf_append_u32(&buf, *handle);
+
+ switch (cmd) {
+ case TPM2_CC_POLICY_PCR:
+ failure = "PCR";
+ /*
+ * for reasons best known to the TCG we have
+ * to reverse the two arguments to send to the
+ * policy command
+ */
+ tpm_buf_append_u16(&buf, pols->hash_size);
+ tpm_buf_append(&buf, pols->policies[i] + pols->len[i] -
+ pols->hash_size, pols->hash_size);
+ tpm_buf_append(&buf, pols->policies[i],
+ pols->len[i] - pols->hash_size);
+ break;
+ default:
+ failure = "unknown policy";
+ break;
+ }
+
+ rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+ tpm_buf_destroy(&buf);
+ if (rc) {
+ printk(KERN_NOTICE "TPM policy %s failed, rc=%d\n",
+ failure, rc);
+ tpm2_flush_context(chip, *handle);
+ *handle = 0;
+ return -EPERM;
+ }
+ }
+
+ return 0;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
new file mode 100644
index 000000000000..46bf1f0a9325
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+struct tpm2_key_context {
+ u32 parent;
+ const u8 *pub;
+ u32 pub_len;
+ const u8 *priv;
+ u32 priv_len;
+ const u8 *policies[TPM2_MAX_POLICIES];
+ u32 policy_code[TPM2_MAX_POLICIES];
+ u16 policy_len[TPM2_MAX_POLICIES];
+ u8 policy_count;
+};
+
+struct tpm2_policies {
+ u32 code[TPM2_MAX_POLICIES];
+ u8 *policies[TPM2_MAX_POLICIES];
+ u16 len[TPM2_MAX_POLICIES];
+ u8 count;
+ u16 hash;
+ u16 hash_size;
+};
+
+int tpm2_key_policy_process(struct tpm2_key_context *ctx,
+ struct trusted_key_payload *payload);
+int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
+ u8 *policydigest, u32 *plen);
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+ u32 *handle);
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
index 3f6a9d01d1e5..0c241d000120 100644
--- a/security/keys/trusted-keys/tpm2key.asn1
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -1,11 +1,24 @@
---
--- ASN.1 for for TPM 2.0 keys
---
+--- Note: This isn't quite the definition in the standard
+--- However, the Linux asn.1 parser doesn't understand
+--- [2] EXPLICIT SEQUENCE OF OPTIONAL
+--- So there's an extra intermediate TPMPolicySequence
+--- definition to work around this
TPMKey ::= SEQUENCE {
type OBJECT IDENTIFIER ({tpm2_key_type}),
emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL,
+ policy [1] EXPLICIT TPMPolicySequence OPTIONAL,
parent INTEGER ({tpm2_key_parent}),
pubkey OCTET STRING ({tpm2_key_pub}),
privkey OCTET STRING ({tpm2_key_priv})
}
+
+TPMPolicySequence ::= SEQUENCE OF TPMPolicy
+
+TPMPolicy ::= SEQUENCE {
+ commandCode [0] EXPLICIT INTEGER ({tpm2_key_code}),
+ commandPolicy [1] EXPLICIT OCTET STRING ({tpm2_key_policy})
+ }
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 0f026656d635..2f62db74e771 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -1065,6 +1065,8 @@ static void trusted_rcu_free(struct rcu_head *rcu)
struct trusted_key_payload *p;
p = container_of(rcu, struct trusted_key_payload, rcu);
+
+ kfree_sensitive(p->policies);
kfree_sensitive(p);
}
@@ -1174,7 +1176,11 @@ static long trusted_read(const struct key *key, char *buffer,
*/
static void trusted_destroy(struct key *key)
{
- kfree_sensitive(key->payload.data[0]);
+ struct trusted_key_payload *p;
+
+ p = key->payload.data[0];
+ kfree_sensitive(p->policies);
+ kfree_sensitive(p);
}
struct key_type key_type_trusted = {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 905c5ca4d51c..98c65431ca75 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -17,6 +17,7 @@
#include <asm/unaligned.h>
#include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
static struct tpm2_hash tpm2_hash_map[] = {
{HASH_ALGO_SHA1, TPM_ALG_SHA1},
@@ -62,6 +63,21 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
}
+ if (payload->policies) {
+ u8 *encoded_pols;
+ u32 encoded_pol_len;
+ int ret;
+
+ ret = tpm2_encode_policy(payload->policies, &encoded_pols,
+ &encoded_pol_len);
+ if (ret)
+ return ret;
+
+ work = asn1_encode_tag(work, end_work, 1, encoded_pols,
+ encoded_pol_len);
+ kfree(encoded_pols);
+ }
+
/*
* Assume both octet strings will encode to a 2 byte definite length
*
@@ -85,14 +101,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
return work1 - payload->blob;
}
-struct tpm2_key_context {
- u32 parent;
- const u8 *pub;
- u32 pub_len;
- const u8 *priv;
- u32 priv_len;
-};
-
static int tpm2_key_decode(struct trusted_key_payload *payload,
struct trusted_key_options *options,
u8 **buf)
@@ -115,6 +123,12 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
if (!blob)
return -ENOMEM;
+ ret = tpm2_key_policy_process(&ctx, payload);
+ if (ret) {
+ kfree(blob);
+ return ret;
+ }
+
*buf = blob;
options->keyhandle = ctx.parent;
@@ -248,6 +262,42 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
if (!options->keyhandle)
return -EINVAL;
+ if (options->pcrinfo_len != 0) {
+ struct tpm2_policies *pols;
+ static u8 *scratch;
+ /* 4 array len, 2 hash alg */
+ const int len = 4 + 2 + options->pcrinfo_len;
+
+ pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
+ if (!pols)
+ return -ENOMEM;
+
+ pols->count = 1;
+ pols->len[0] = len;
+ scratch = (u8 *)(pols + 1);
+ pols->policies[0] = scratch;
+ pols->code[0] = TPM2_CC_POLICY_PCR;
+
+ put_unaligned_be32(1, &scratch[0]);
+ put_unaligned_be16(hash, &scratch[4]);
+ memcpy(&scratch[6], options->pcrinfo, options->pcrinfo_len);
+ payload->policies = pols;
+ }
+
+ if (options->policydigest_len != 0 && payload->policies) {
+ /* can't specify both a digest and a policy */
+ return -EINVAL;
+ }
+
+ if (payload->policies) {
+ rc = tpm2_generate_policy_digest(payload->policies,
+ options->hash,
+ options->policydigest,
+ &options->policydigest_len);
+ if (rc)
+ return rc;
+ }
+
rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
if (rc)
return rc;
@@ -456,21 +506,37 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
u16 data_len;
u8 *data;
int rc;
+ u32 policyhandle;
+
+ if (payload->policies && options->policyhandle)
+ /* can't have both a passed in policy and a key resident one */
+ return -EINVAL;
rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
if (rc)
return rc;
+ if (payload->policies) {
+ rc = tpm2_get_policy_session(chip, payload->policies,
+ &policyhandle);
+ if (rc)
+ return rc;
+ } else {
+ policyhandle = options->policyhandle;
+ }
+
tpm_buf_append_u32(&buf, blob_handle);
tpm2_buf_append_auth(&buf,
- options->policyhandle ?
- options->policyhandle : TPM2_RS_PW,
+ policyhandle ?
+ policyhandle : TPM2_RS_PW,
NULL /* nonce */, 0,
TPM2_SA_CONTINUE_SESSION,
options->blobauth /* hmac */,
options->blobauth_len);
rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+ if (payload->policies)
+ tpm2_flush_context(chip, policyhandle);
if (rc > 0)
rc = -EPERM;
--
2.26.2
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v11 2/3] security: keys: trusted: add ability to specify arbitrary policy
2020-09-12 17:39 ` James Bottomley
@ 2020-09-12 17:39 ` James Bottomley
-1 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This patch adds a policy= argument to key creation. The policy is the
standard tss policymaker format and each separate policy line must
have a newline after it.
Thus to construct a policy requiring authorized value and pcr 16
locking using a sha256 hash, the policy (policy.txt) file would be two
lines:
0000017F00000001000B03000001303095B49BE85E381E5B20E557E46363EF55B0F43B132C2D8E3DE9AC436656F2
0000016b
This can be inserted into the key with
keyctl add trusted kmk "new 32 policy=`cat policy.txt` keyhandle=0x81000001 hash=sha256" @u
Note that although a few policies work like this, most require special
handling which must be added to the kernel policy construction
routine.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
.../security/keys/trusted-encrypted.rst | 16 ++++++
security/keys/trusted-keys/tpm2-policy.c | 53 +++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 1 +
security/keys/trusted-keys/trusted_tpm1.c | 15 ++++++
4 files changed, 85 insertions(+)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 8b7853a277bc..f001752adaa1 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -76,6 +76,9 @@ 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.
+ policy= specify an arbitrary set of policies. These must
+ be in policymaker format with each separate
+ policy line newline terminated.
"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.
@@ -168,6 +171,19 @@ zeros (the value of PCR 16)::
$ dd if=/dev/zero bs=1 count 2>/dev/null|sha1sum
6768033e216468247bd031a0a2d9876d79818f8f
+You can also specify arbitrary policy in policymaker format, so a two
+value policy (the pcr example above and authvalue) would look like
+this in policymaker format::
+
+ 0000017F000000010004030000016768033e216468247bd031a0a2d9876d79818f8f
+ 0000016b
+
+This can be placed in a file (say policy.txt) and then added to the key as::
+
+ $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 policy=`cat policy.txt`" @u
+
+The newlines in the file policy.txt will be automatically processed.
+
Reseal a trusted key under new pcr values::
$ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 080a76e879fd..87a13e607eca 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -370,3 +370,56 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
return 0;
}
+
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str)
+{
+ struct tpm2_policies *pols;
+ char *p;
+ u8 *ptr;
+ int i = 0, left = PAGE_SIZE, res;
+
+ pols = kmalloc(left, GFP_KERNEL);
+ if (!pols)
+ return -ENOMEM;
+
+ ptr = (u8 *)(pols + 1);
+ left -= ptr - (u8 *)pols;
+
+ while ((p = strsep(&str, "\n"))) {
+ if (*p = '\0' || *p = '\n')
+ continue;
+
+ pols->len[i] = strlen(p)/2;
+ if (pols->len[i] > left) {
+ res = -E2BIG;
+ goto err;
+ }
+
+ res = hex2bin(ptr, p, pols->len[i]);
+ if (res)
+ goto err;
+
+ /* get command code and skip past */
+ pols->code[i] = get_unaligned_be32(ptr);
+ pols->policies[i] = ptr + 4;
+ ptr += pols->len[i];
+ left -= pols->len[i];
+ pols->len[i] -= 4;
+
+ /*
+ * FIXME: this does leave the code embedded in dead
+ * regions of the memory, but it's easier than
+ * hexdumping to a temporary or copying over
+ */
+ i++;
+ }
+
+ pols->count = i;
+ *ppols = pols;
+
+ return 0;
+
+ err:
+ kfree(pols);
+ return res;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
index 46bf1f0a9325..0da013116c1c 100644
--- a/security/keys/trusted-keys/tpm2-policy.h
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -28,3 +28,4 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
u32 *handle);
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 2f62db74e771..8b428daba738 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -29,6 +29,8 @@
#include <keys/trusted_tpm.h>
+#include "tpm2-policy.h"
+
static const char hmac_alg[] = "hmac(sha1)";
static const char hash_alg[] = "sha1";
static struct tpm_chip *chip;
@@ -709,6 +711,7 @@ enum {
Opt_hash,
Opt_policydigest,
Opt_policyhandle,
+ Opt_policy,
};
static const match_table_t key_tokens = {
@@ -724,6 +727,7 @@ static const match_table_t key_tokens = {
{Opt_hash, "hash=%s"},
{Opt_policydigest, "policydigest=%s"},
{Opt_policyhandle, "policyhandle=%s"},
+ {Opt_policy, "policy=%s"},
{Opt_err, NULL}
};
@@ -854,6 +858,17 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
return -EINVAL;
opt->policyhandle = handle;
break;
+
+ case Opt_policy:
+ if (pay->policies)
+ return -EINVAL;
+ if (!tpm2)
+ return -EINVAL;
+ res = tpm2_parse_policies(&pay->policies, args[0].from);
+ if (res)
+ return res;
+ break;
+
default:
return -EINVAL;
}
--
2.26.2
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v11 2/3] security: keys: trusted: add ability to specify arbitrary policy
@ 2020-09-12 17:39 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This patch adds a policy= argument to key creation. The policy is the
standard tss policymaker format and each separate policy line must
have a newline after it.
Thus to construct a policy requiring authorized value and pcr 16
locking using a sha256 hash, the policy (policy.txt) file would be two
lines:
0000017F00000001000B03000001303095B49BE85E381E5B20E557E46363EF55B0F43B132C2D8E3DE9AC436656F2
0000016b
This can be inserted into the key with
keyctl add trusted kmk "new 32 policy=`cat policy.txt` keyhandle=0x81000001 hash=sha256" @u
Note that although a few policies work like this, most require special
handling which must be added to the kernel policy construction
routine.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
.../security/keys/trusted-encrypted.rst | 16 ++++++
security/keys/trusted-keys/tpm2-policy.c | 53 +++++++++++++++++++
security/keys/trusted-keys/tpm2-policy.h | 1 +
security/keys/trusted-keys/trusted_tpm1.c | 15 ++++++
4 files changed, 85 insertions(+)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 8b7853a277bc..f001752adaa1 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -76,6 +76,9 @@ 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.
+ policy= specify an arbitrary set of policies. These must
+ be in policymaker format with each separate
+ policy line newline terminated.
"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.
@@ -168,6 +171,19 @@ zeros (the value of PCR 16)::
$ dd if=/dev/zero bs=1 count=20 2>/dev/null|sha1sum
6768033e216468247bd031a0a2d9876d79818f8f
+You can also specify arbitrary policy in policymaker format, so a two
+value policy (the pcr example above and authvalue) would look like
+this in policymaker format::
+
+ 0000017F000000010004030000016768033e216468247bd031a0a2d9876d79818f8f
+ 0000016b
+
+This can be placed in a file (say policy.txt) and then added to the key as::
+
+ $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 policy=`cat policy.txt`" @u
+
+The newlines in the file policy.txt will be automatically processed.
+
Reseal a trusted key under new pcr values::
$ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 080a76e879fd..87a13e607eca 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -370,3 +370,56 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
return 0;
}
+
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str)
+{
+ struct tpm2_policies *pols;
+ char *p;
+ u8 *ptr;
+ int i = 0, left = PAGE_SIZE, res;
+
+ pols = kmalloc(left, GFP_KERNEL);
+ if (!pols)
+ return -ENOMEM;
+
+ ptr = (u8 *)(pols + 1);
+ left -= ptr - (u8 *)pols;
+
+ while ((p = strsep(&str, "\n"))) {
+ if (*p == '\0' || *p == '\n')
+ continue;
+
+ pols->len[i] = strlen(p)/2;
+ if (pols->len[i] > left) {
+ res = -E2BIG;
+ goto err;
+ }
+
+ res = hex2bin(ptr, p, pols->len[i]);
+ if (res)
+ goto err;
+
+ /* get command code and skip past */
+ pols->code[i] = get_unaligned_be32(ptr);
+ pols->policies[i] = ptr + 4;
+ ptr += pols->len[i];
+ left -= pols->len[i];
+ pols->len[i] -= 4;
+
+ /*
+ * FIXME: this does leave the code embedded in dead
+ * regions of the memory, but it's easier than
+ * hexdumping to a temporary or copying over
+ */
+ i++;
+ }
+
+ pols->count = i;
+ *ppols = pols;
+
+ return 0;
+
+ err:
+ kfree(pols);
+ return res;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
index 46bf1f0a9325..0da013116c1c 100644
--- a/security/keys/trusted-keys/tpm2-policy.h
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -28,3 +28,4 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
u32 *handle);
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 2f62db74e771..8b428daba738 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -29,6 +29,8 @@
#include <keys/trusted_tpm.h>
+#include "tpm2-policy.h"
+
static const char hmac_alg[] = "hmac(sha1)";
static const char hash_alg[] = "sha1";
static struct tpm_chip *chip;
@@ -709,6 +711,7 @@ enum {
Opt_hash,
Opt_policydigest,
Opt_policyhandle,
+ Opt_policy,
};
static const match_table_t key_tokens = {
@@ -724,6 +727,7 @@ static const match_table_t key_tokens = {
{Opt_hash, "hash=%s"},
{Opt_policydigest, "policydigest=%s"},
{Opt_policyhandle, "policyhandle=%s"},
+ {Opt_policy, "policy=%s"},
{Opt_err, NULL}
};
@@ -854,6 +858,17 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
return -EINVAL;
opt->policyhandle = handle;
break;
+
+ case Opt_policy:
+ if (pay->policies)
+ return -EINVAL;
+ if (!tpm2)
+ return -EINVAL;
+ res = tpm2_parse_policies(&pay->policies, args[0].from);
+ if (res)
+ return res;
+ break;
+
default:
return -EINVAL;
}
--
2.26.2
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v11 3/3] security: keys: trusted: implement counter/timer policy
2020-09-12 17:39 ` James Bottomley
@ 2020-09-12 17:39 ` James Bottomley
-1 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This is actually a generic policy allowing a range of comparisons
against any value set in the TPM Clock, which includes things like the
reset count, a monotonic millisecond count and the restart count. The
most useful comparison is against the millisecond count for expiring
keys. However, you have to remember that currently Linux doesn't try
to sync the epoch timer with the TPM, so the expiration is actually
measured in how long the TPM itself has been powered on ... the TPM
timer doesn't count while the system is powered down. The millisecond
counter is a u64 quantity found at offset 8 in the timer structure,
and the <= comparision operand is 9, so a policy set to expire after the
TPM has been up for 100 seconds would look like
0000016d00000000000f424000080009
Where 0x16d is the counter timer policy code and 0xf4240 is 100 000 in
hex.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
.../security/keys/trusted-encrypted.rst | 31 +++++++++++++-
include/linux/tpm.h | 1 +
security/keys/trusted-keys/tpm2-policy.c | 40 ++++++++++++++++++-
security/keys/trusted-keys/trusted_tpm2.c | 36 ++++++++++++++++-
4 files changed, 105 insertions(+), 3 deletions(-)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index f001752adaa1..e5414ed996bf 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -242,7 +242,6 @@ Another new format 'enc32' has been defined in order to support encrypted keys
with payload size of 32 bytes. This will initially be used for nvdimm security
but may expand to other usages that require 32 bytes payload.
-
TPM 2.0 ASN.1 Key Format
------------------------
@@ -316,3 +315,33 @@ string length.
privkey is the binary representation of TPM2B_PUBLIC excluding the
initial TPM2B header which can be reconstructed from the ASN.1 octed
string length.
+
+
+Appendix
+--------
+
+TPM 2.0 Policies
+----------------
+
+The current TPM supports PCR lock policies as documented above and
+CounterTimer policies which can be used to create expiring keys. One
+caveat with expiring keys is that the TPM millisecond counter does not
+update while a system is powered off and Linux does not sync the TPM
+millisecond count with its internal clock, so the best you can expire
+in is in terms of how long any given TPM has been powered on. (FIXME:
+Linux should simply update the millisecond clock to the current number
+of seconds past the epoch on boot).
+
+A CounterTimer policy is expressed in terms of length and offset
+against the TPM clock structure (TPMS_TIME_INFO), which looks like the
+packed structure::
+
+ struct tpms_time_info {
+ u64 uptime; /* time in ms since last start or reset */
+ u64 clock; /* cumulative uptime in ms */
+ u32 resetcount; /* numer of times the TPM has been reset */
+ u32 restartcount; /* number of times the TPM has been restarted */
+ u8 safe /* time was safely loaded from NVRam */
+ };
+
+The usual comparison for expiring keys is against clock, at offset 8.
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 254c33086288..cc0b94dcf21e 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -241,6 +241,7 @@ enum tpm2_command_codes {
TPM2_CC_PCR_EXTEND = 0x0182,
TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
TPM2_CC_HASH_SEQUENCE_START = 0x0186,
+ TPM2_CC_POLICY_PASSWORD = 0x018c,
TPM2_CC_CREATE_LOADED = 0x0191,
TPM2_CC_LAST = 0x0193, /* Spec 1.36 */
};
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 87a13e607eca..bd8eb02e1094 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -197,7 +197,8 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols,
len = *plen;
}
- crypto_shash_update(sdesc, policy, len);
+ if (len)
+ crypto_shash_update(sdesc, policy, len);
/* now output the intermediate to the policydigest */
crypto_shash_final(sdesc, policydigest);
@@ -332,6 +333,16 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
u32 cmd = pols->code[i];
struct tpm_buf buf;
+ if (cmd = TPM2_CC_POLICY_AUTHVALUE)
+ /*
+ * both PolicyAuthValue and PolicyPassword
+ * hash to the same thing, but one triggers
+ * HMAC authentication and the other simple
+ * authentication. Since we have no HMAC
+ * code, we're choosing the simple
+ */
+ cmd = TPM2_CC_POLICY_PASSWORD;
+
rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
if (rc)
return rc;
@@ -352,8 +363,35 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
tpm_buf_append(&buf, pols->policies[i],
pols->len[i] - pols->hash_size);
break;
+
+ case TPM2_CC_POLICY_COUNTER_TIMER: {
+ /*
+ * the format of this is the last two u16
+ * quantities are the offset and operation
+ * respectively. The rest is operandB which
+ * must be zero padded in a hash digest
+ */
+ u16 opb_len = pols->len[i] - 4;
+
+ if (opb_len > pols->hash_size)
+ return -EINVAL;
+
+ tpm_buf_append_u16(&buf, opb_len);
+ tpm_buf_append(&buf, pols->policies[i], opb_len);
+
+ /* offset and operand*/
+ tpm_buf_append(&buf, pols->policies[i] + opb_len, 4);
+ failure = "Counter Timer";
+
+ break;
+ }
+
default:
failure = "unknown policy";
+ if (pols->len[i])
+ tpm_buf_append(&buf, pols->policies[i],
+ pols->len[i]);
+
break;
}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 98c65431ca75..3ec01ed874d9 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -248,6 +248,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
u32 flags;
int i;
int rc;
+ static const int POLICY_SIZE = 2 * PAGE_SIZE;
for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
if (options->hash = tpm2_hash_map[i].crypto_id) {
@@ -268,7 +269,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
/* 4 array len, 2 hash alg */
const int len = 4 + 2 + options->pcrinfo_len;
- pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
+ pols = kmalloc(POLICY_SIZE, GFP_KERNEL);
if (!pols)
return -ENOMEM;
@@ -289,6 +290,39 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
return -EINVAL;
}
+ /*
+ * if we already have a policy, we have to add authorization
+ * to it. If we don't, we can simply follow the usual
+ * non-policy route.
+ */
+ if (options->blobauth_len != 0 && payload->policies) {
+ struct tpm2_policies *pols;
+ static u8 *scratch;
+ int i;
+ bool found = false;
+
+ pols = payload->policies;
+
+ /* make sure it's not already in policy */
+ for (i = 0; i < pols->count; i++) {
+ if (pols->code[i] = TPM2_CC_POLICY_AUTHVALUE) {
+ found = true;
+
+ break;
+ }
+ }
+
+ if (!found) {
+ i = pols->count++;
+ scratch = pols->policies[i - 1] + pols->len[i - 1];
+
+ /* the TPM2_PolicyPassword command has no payload */
+ pols->policies[i] = scratch;
+ pols->len[i] = 0;
+ pols->code[i] = TPM2_CC_POLICY_AUTHVALUE;
+ }
+ }
+
if (payload->policies) {
rc = tpm2_generate_policy_digest(payload->policies,
options->hash,
--
2.26.2
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v11 3/3] security: keys: trusted: implement counter/timer policy
@ 2020-09-12 17:39 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-12 17:39 UTC (permalink / raw)
To: linux-integrity
Cc: Mimi Zohar, Jarkko Sakkinen, David Woodhouse, keyrings, David Howells
This is actually a generic policy allowing a range of comparisons
against any value set in the TPM Clock, which includes things like the
reset count, a monotonic millisecond count and the restart count. The
most useful comparison is against the millisecond count for expiring
keys. However, you have to remember that currently Linux doesn't try
to sync the epoch timer with the TPM, so the expiration is actually
measured in how long the TPM itself has been powered on ... the TPM
timer doesn't count while the system is powered down. The millisecond
counter is a u64 quantity found at offset 8 in the timer structure,
and the <= comparision operand is 9, so a policy set to expire after the
TPM has been up for 100 seconds would look like
0000016d00000000000f424000080009
Where 0x16d is the counter timer policy code and 0xf4240 is 100 000 in
hex.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
.../security/keys/trusted-encrypted.rst | 31 +++++++++++++-
include/linux/tpm.h | 1 +
security/keys/trusted-keys/tpm2-policy.c | 40 ++++++++++++++++++-
security/keys/trusted-keys/trusted_tpm2.c | 36 ++++++++++++++++-
4 files changed, 105 insertions(+), 3 deletions(-)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index f001752adaa1..e5414ed996bf 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -242,7 +242,6 @@ Another new format 'enc32' has been defined in order to support encrypted keys
with payload size of 32 bytes. This will initially be used for nvdimm security
but may expand to other usages that require 32 bytes payload.
-
TPM 2.0 ASN.1 Key Format
------------------------
@@ -316,3 +315,33 @@ string length.
privkey is the binary representation of TPM2B_PUBLIC excluding the
initial TPM2B header which can be reconstructed from the ASN.1 octed
string length.
+
+
+Appendix
+--------
+
+TPM 2.0 Policies
+----------------
+
+The current TPM supports PCR lock policies as documented above and
+CounterTimer policies which can be used to create expiring keys. One
+caveat with expiring keys is that the TPM millisecond counter does not
+update while a system is powered off and Linux does not sync the TPM
+millisecond count with its internal clock, so the best you can expire
+in is in terms of how long any given TPM has been powered on. (FIXME:
+Linux should simply update the millisecond clock to the current number
+of seconds past the epoch on boot).
+
+A CounterTimer policy is expressed in terms of length and offset
+against the TPM clock structure (TPMS_TIME_INFO), which looks like the
+packed structure::
+
+ struct tpms_time_info {
+ u64 uptime; /* time in ms since last start or reset */
+ u64 clock; /* cumulative uptime in ms */
+ u32 resetcount; /* numer of times the TPM has been reset */
+ u32 restartcount; /* number of times the TPM has been restarted */
+ u8 safe /* time was safely loaded from NVRam */
+ };
+
+The usual comparison for expiring keys is against clock, at offset 8.
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 254c33086288..cc0b94dcf21e 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -241,6 +241,7 @@ enum tpm2_command_codes {
TPM2_CC_PCR_EXTEND = 0x0182,
TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
TPM2_CC_HASH_SEQUENCE_START = 0x0186,
+ TPM2_CC_POLICY_PASSWORD = 0x018c,
TPM2_CC_CREATE_LOADED = 0x0191,
TPM2_CC_LAST = 0x0193, /* Spec 1.36 */
};
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 87a13e607eca..bd8eb02e1094 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -197,7 +197,8 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols,
len = *plen;
}
- crypto_shash_update(sdesc, policy, len);
+ if (len)
+ crypto_shash_update(sdesc, policy, len);
/* now output the intermediate to the policydigest */
crypto_shash_final(sdesc, policydigest);
@@ -332,6 +333,16 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
u32 cmd = pols->code[i];
struct tpm_buf buf;
+ if (cmd == TPM2_CC_POLICY_AUTHVALUE)
+ /*
+ * both PolicyAuthValue and PolicyPassword
+ * hash to the same thing, but one triggers
+ * HMAC authentication and the other simple
+ * authentication. Since we have no HMAC
+ * code, we're choosing the simple
+ */
+ cmd = TPM2_CC_POLICY_PASSWORD;
+
rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
if (rc)
return rc;
@@ -352,8 +363,35 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
tpm_buf_append(&buf, pols->policies[i],
pols->len[i] - pols->hash_size);
break;
+
+ case TPM2_CC_POLICY_COUNTER_TIMER: {
+ /*
+ * the format of this is the last two u16
+ * quantities are the offset and operation
+ * respectively. The rest is operandB which
+ * must be zero padded in a hash digest
+ */
+ u16 opb_len = pols->len[i] - 4;
+
+ if (opb_len > pols->hash_size)
+ return -EINVAL;
+
+ tpm_buf_append_u16(&buf, opb_len);
+ tpm_buf_append(&buf, pols->policies[i], opb_len);
+
+ /* offset and operand*/
+ tpm_buf_append(&buf, pols->policies[i] + opb_len, 4);
+ failure = "Counter Timer";
+
+ break;
+ }
+
default:
failure = "unknown policy";
+ if (pols->len[i])
+ tpm_buf_append(&buf, pols->policies[i],
+ pols->len[i]);
+
break;
}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 98c65431ca75..3ec01ed874d9 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -248,6 +248,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
u32 flags;
int i;
int rc;
+ static const int POLICY_SIZE = 2 * PAGE_SIZE;
for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
if (options->hash == tpm2_hash_map[i].crypto_id) {
@@ -268,7 +269,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
/* 4 array len, 2 hash alg */
const int len = 4 + 2 + options->pcrinfo_len;
- pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
+ pols = kmalloc(POLICY_SIZE, GFP_KERNEL);
if (!pols)
return -ENOMEM;
@@ -289,6 +290,39 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
return -EINVAL;
}
+ /*
+ * if we already have a policy, we have to add authorization
+ * to it. If we don't, we can simply follow the usual
+ * non-policy route.
+ */
+ if (options->blobauth_len != 0 && payload->policies) {
+ struct tpm2_policies *pols;
+ static u8 *scratch;
+ int i;
+ bool found = false;
+
+ pols = payload->policies;
+
+ /* make sure it's not already in policy */
+ for (i = 0; i < pols->count; i++) {
+ if (pols->code[i] == TPM2_CC_POLICY_AUTHVALUE) {
+ found = true;
+
+ break;
+ }
+ }
+
+ if (!found) {
+ i = pols->count++;
+ scratch = pols->policies[i - 1] + pols->len[i - 1];
+
+ /* the TPM2_PolicyPassword command has no payload */
+ pols->policies[i] = scratch;
+ pols->len[i] = 0;
+ pols->code[i] = TPM2_CC_POLICY_AUTHVALUE;
+ }
+ }
+
if (payload->policies) {
rc = tpm2_generate_policy_digest(payload->policies,
options->hash,
--
2.26.2
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys
2020-09-12 17:39 ` James Bottomley
@ 2020-09-14 19:37 ` Jarkko Sakkinen
-1 siblings, 0 replies; 14+ messages in thread
From: Jarkko Sakkinen @ 2020-09-14 19:37 UTC (permalink / raw)
To: James Bottomley
Cc: linux-integrity, Mimi Zohar, David Woodhouse, keyrings, David Howells
No sure why this is v11. I don't think we have reviewed this series that
many times.
On Sat, Sep 12, 2020 at 10:39:36AM -0700, James Bottomley wrote:
> This commit adds the ability to specify a PCR lock policy to TPM2
> keys. There is a complexity in that the creator of the key must chose
> either to use a PCR lock policy or to use authentication. At the
> current time they can't use both due to a complexity with the way
> authentication works when policy registers are in use. The way to
> construct a pcrinfo statement for a key is simply to use the
> TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
> hash of all their values in order of ascending PCR number.
>
> For simplicity, we require the policy name hash and the hash used for
> the PCRs to be the same. Thus to construct a policy around the value
It would be better to write "name hash algorithm" and "policy hash
algorithm".
> of the resettable PCR 16 using the sha1 bank, first reset the pcr to
~~~
PCR
> zero giving a hash of all zeros as:
>
> 6768033e216468247bd031a0a2d9876d79818f8f
>
> Then the TPMS_PCR_SELECT value for PCR 16 is
>
> 03000001
>
> So create a new 32 byte key with a policy policy locking the key to
> this value of PCR 16 with a parent key of 81000001 would be:
>
> keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
>
Extra newline.
> ---
>
> v2: fix for new ASN.1 API eliminating hack in place and check lengths
> v8: recover patch and fix offsets for hash and size
> v9: fix cut and paste error in commit log
> v10: update for kfree_sensitive()
> v11: add policy to ASN.1 key format description
> ---
> .../security/keys/trusted-encrypted.rst | 36 +-
> include/keys/trusted-type.h | 5 +-
> include/linux/tpm.h | 5 +
> security/keys/Kconfig | 2 +
> security/keys/trusted-keys/Makefile | 2 +-
> security/keys/trusted-keys/tpm2-policy.c | 372 ++++++++++++++++++
> security/keys/trusted-keys/tpm2-policy.h | 30 ++
> security/keys/trusted-keys/tpm2key.asn1 | 13 +
> security/keys/trusted-keys/trusted_tpm1.c | 8 +-
> security/keys/trusted-keys/trusted_tpm2.c | 86 +++-
> 10 files changed, 545 insertions(+), 14 deletions(-)
> create mode 100644 security/keys/trusted-keys/tpm2-policy.c
> create mode 100644 security/keys/trusted-keys/tpm2-policy.h
>
> diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
> index eb639bb24fcc..8b7853a277bc 100644
> --- a/Documentation/security/keys/trusted-encrypted.rst
> +++ b/Documentation/security/keys/trusted-encrypted.rst
> @@ -60,7 +60,10 @@ Usage::
> (40 ascii zeros)
> blobauth= ascii hex auth for sealed data default 0x00...
> (40 ascii zeros)
> - pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
> + pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no
> + default) on TPM 1.2 and a TPMS_PCR_SELECTION
> + coupled with a hash of all the selected PCRs on
> + TPM 2.0 using the selected hash.
> pcrlock= pcr number to be extended to "lock" blob
> migratable= 0|1 indicating permission to reseal to new PCR values,
> default 1 (resealing allowed)
> @@ -151,6 +154,20 @@ Load a trusted key from the saved blob::
> f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
> e4a8aea2b607ec96931e6f4d4fe563ba
>
> +Create a trusted key on TPM 2.0 using an all zero value of PCR16 and
> +using the NV storage root 81000001 as the parent::
> +
> + $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u
> +
> +Note the TPMS_PCR_SELECT value for PCR 16 is 03000001 because all
> +current TPMs have 24 PCRs, so the initial 03 says there are three
> +following bytes of selection and then because the bytes are big
> +endian, 16 is bit zero of byte 2. the hash is the sha1 sum of all
> +zeros (the value of PCR 16)::
> +
> + $ dd if=/dev/zero bs=1 count 2>/dev/null|sha1sum
> + 6768033e216468247bd031a0a2d9876d79818f8f
> +
> Reseal a trusted key under new pcr values::
>
> $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
> @@ -221,11 +238,17 @@ policy::
> TPMKey ::= SEQUENCE {
> type OBJECT IDENTIFIER
> emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
> + policy [1] EXPLICIT SEQUENCE OF TPMPolicy OPTIONAL
> parent INTEGER
> pubkey OCTET STRING
> privkey OCTET STRING
> }
>
> + TPMPolicy ::= SEQUENCE {
> + CommandCode [0] EXPLICIT INTEGER
> + CommandPolicy [1] EXPLICIT OCTET STRING
> + }
> +
> type is what distinguishes the key even in binary form since the OID
> is provided by the TCG to be unique and thus forms a recognizable
> binary pattern at offset 3 in the key. The OIDs currently made
> @@ -251,6 +274,17 @@ is false or not present, the key requires an explicit authorization
> phrase. This is used by most user space consumers to decide whether
> to prompt for a password.
>
> +policy represents a sequence of one or more policy statements that
> +must be executed successfully into a session policy register. If
> +policy isn't present then no policy is required to unlock the key, but
> +if it is, commandCode is the TPM 2.0 command code of the policy
> +instruction that must be executed and CommandPolicy represents the
> +binary parameter area of the policy command.
> +
> +Note that the current sequential execution requirement means that only
> +AND based policy can be constructed at the moment, so TPM2_PolicyOR is
> +not currently supported.
> +
> parent represents the parent key handle, either in the 0x81 MSO space,
> like 0x81000001 for the RSA primary storage key. Userspace programmes
> also support specifying the primary handle in the 0x40 MSO space. If
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index b2d87ad21714..c117bf598230 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -14,9 +14,11 @@
> #define MIN_KEY_SIZE 32
> #define MAX_KEY_SIZE 128
> #define MAX_BLOB_SIZE 512
> -#define MAX_PCRINFO_SIZE 64
> +#define MAX_PCRINFO_SIZE 128
> #define MAX_DIGEST_SIZE 64
>
> +#define TPM2_MAX_POLICIES 16
> +
> struct trusted_key_payload {
> struct rcu_head rcu;
> unsigned int key_len;
> @@ -25,6 +27,7 @@ struct trusted_key_payload {
> unsigned char old_format;
> unsigned char key[MAX_KEY_SIZE + 1];
> unsigned char blob[MAX_BLOB_SIZE];
> + struct tpm2_policies *policies;
> };
>
> struct trusted_key_options {
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 35224860fd0c..254c33086288 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -230,10 +230,14 @@ enum tpm2_command_codes {
> TPM2_CC_CONTEXT_LOAD = 0x0161,
> TPM2_CC_CONTEXT_SAVE = 0x0162,
> TPM2_CC_FLUSH_CONTEXT = 0x0165,
> + TPM2_CC_POLICY_AUTHVALUE = 0x016B,
> + TPM2_CC_POLICY_COUNTER_TIMER = 0x016D,
> + TPM2_CC_START_AUTH_SESS = 0x0176,
> TPM2_CC_VERIFY_SIGNATURE = 0x0177,
> TPM2_CC_GET_CAPABILITY = 0x017A,
> TPM2_CC_GET_RANDOM = 0x017B,
> TPM2_CC_PCR_READ = 0x017E,
> + TPM2_CC_POLICY_PCR = 0x017F,
> TPM2_CC_PCR_EXTEND = 0x0182,
> TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
> TPM2_CC_HASH_SEQUENCE_START = 0x0186,
> @@ -242,6 +246,7 @@ enum tpm2_command_codes {
> };
>
> enum tpm2_permanent_handles {
> + TPM2_RH_NULL = 0x40000007,
> TPM2_RS_PW = 0x40000009,
> };
>
> diff --git a/security/keys/Kconfig b/security/keys/Kconfig
> index 8fbfedf6d1cc..d9977359b8a6 100644
> --- a/security/keys/Kconfig
> +++ b/security/keys/Kconfig
> @@ -74,6 +74,8 @@ config TRUSTED_KEYS
> select CRYPTO
> select CRYPTO_HMAC
> select CRYPTO_SHA1
> + select CRYPTO_SHA256
> + select CRYPTO_SHA512
> select CRYPTO_HASH_INFO
> select ASN1_ENCODER
> help
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
> index e0198641eff2..194febacf362 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -5,4 +5,4 @@
>
> obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
> trusted-y += trusted_tpm1.o
> -trusted-y += trusted_tpm2.o tpm2key.asn1.o
> +trusted-y += trusted_tpm2.o tpm2key.asn1.o tpm2-policy.o
> diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
> new file mode 100644
> index 000000000000..080a76e879fd
> --- /dev/null
> +++ b/security/keys/trusted-keys/tpm2-policy.c
> @@ -0,0 +1,372 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
> + */
> +
> +#include <linux/asn1_encoder.h>
> +#include <linux/err.h>
> +#include <linux/types.h>
> +#include <linux/printk.h>
> +#include <linux/string.h>
> +#include <linux/tpm.h>
> +
> +#include <asm/unaligned.h>
> +
> +#include <crypto/hash.h>
> +
> +#include <keys/trusted-type.h>
> +#include <keys/trusted_tpm.h>
> +
> +#include "tpm2key.asn1.h"
> +#include "tpm2-policy.h"
> +
> +int tpm2_key_code(void *context, size_t hdrlen,
> + unsigned char tag,
> + const void *value, size_t vlen)
> +{
> + struct tpm2_key_context *ctx = context;
> + u32 code = 0;
> + const u8 *v = value;
> + int i;
> +
> + for (i = 0; i < vlen; i++) {
> + code <<= 8;
> + code |= v[i];
> + }
> +
> + ctx->policy_code[ctx->policy_count] = code;
> +
> + return 0;
> +}
> +
> +int tpm2_key_policy(void *context, size_t hdrlen,
> + unsigned char tag,
> + const void *value, size_t vlen)
> +{
> + struct tpm2_key_context *ctx = context;
> +
> + ctx->policies[ctx->policy_count] = value;
> + ctx->policy_len[ctx->policy_count++] = vlen;
> +
> + return 0;
> +}
As non-static symbols, and in general to make the code more
understandable, must be documeted.
> +
> +/* we only support a limited number of policy statement so
> + * make sure we don't have anything we can't support
> + */
> +static int tpm2_validate_policy(struct tpm2_policies *pols)
> +{
> + int i;
> +
> + if (pols->count = 0)
> + return 0;
> +
> + for (i = 0; i < pols->count; i++) {
> + switch (pols->code[i]) {
> + case TPM2_CC_POLICY_COUNTER_TIMER:
> + case TPM2_CC_POLICY_PCR:
> + case TPM2_CC_POLICY_AUTHVALUE:
> + break;
> + default:
> + printk(KERN_INFO "tpm2 policy 0x%x is unsupported",
> + pols->code[i]);
> + return -EINVAL;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * tpm2_key_process_policy - collect the policty from the context
> + * @ctx: the context to collect from
> + * @payload: the payload structure to place it in
> + *
> + * THis function sizes the policy statements and allocates space
> + * within the payload to receive them before copying them over. It
> + * should be used after the ber decoder has completed successfully
> + */
> +int tpm2_key_policy_process(struct tpm2_key_context *ctx,
> + struct trusted_key_payload *payload)
> +{
> + int tot_len = 0;
> + u8 *buf;
> + int i, ret, len = 0;
> + struct tpm2_policies *pols;
> +
> + if (ctx->policy_count = 0)
> + return 0;
> +
> + for (i = 0; i < ctx->policy_count; i++)
> + tot_len += ctx->policy_len[i];
> + tot_len += sizeof(*pols);
> +
> + pols = kmalloc(tot_len, GFP_KERNEL);
> + if (!pols)
> + return -ENOMEM;
> +
> + payload->policies = pols;
> + buf = (u8 *)(pols + 1);
> +
> + for (i = 0; i < ctx->policy_count; i++) {
> + pols->policies[i] = &buf[len];
> + pols->len[i] = ctx->policy_len[i];
> + pols->code[i] = ctx->policy_code[i];
> + if (pols->len[i])
> + memcpy(pols->policies[i], ctx->policies[i],
> + ctx->policy_len[i]);
> + len += ctx->policy_len[i];
> + }
> + pols->count = ctx->policy_count;
> +
> + ret = tpm2_validate_policy(pols);
> + if (ret) {
> + kfree(pols);
> + payload->policies = NULL;
> + }
> +
> + /* capture the hash and size */
> +
> + /* the hash is the second algorithm */
> + pols->hash = get_unaligned_be16(&ctx->pub[4]);
> + /* and the digest appears after the attributes */
> + pols->hash_size = get_unaligned_be16(&ctx->pub[10]);
> +
> + return ret;
> +}
> +
> +int tpm2_generate_policy_digest(struct tpm2_policies *pols,
> + u32 hash, u8 *policydigest, u32 *plen)
> +{
> + int i;
> + struct crypto_shash *tfm;
> + int rc;
> +
> + if (pols->count = 0)
> + return 0;
> +
> + tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
> + if (IS_ERR(tfm))
> + return PTR_ERR(tfm);
> +
> + rc = crypto_shash_digestsize(tfm);
> + if (WARN(rc > MAX_DIGEST_SIZE,
> + "BUG: trusted key code has alg %s with digest too large (%d)",
> + hash_algo_name[hash], rc)) {
> + rc = -EINVAL;
> + goto err;
> + }
> +
> + pols->hash = hash;
> + pols->hash_size = rc;
> + *plen = rc;
> +
> + /* policy digests always start out all zeros */
> + memset(policydigest, 0, rc);
> +
> + for (i = 0; i < pols->count; i++) {
> + u8 *policy = pols->policies[i];
> + int len = pols->len[i];
> + u32 cmd = pols->code[i];
> + u8 digest[MAX_DIGEST_SIZE];
> + u8 code[4];
> + SHASH_DESC_ON_STACK(sdesc, tfm);
> +
> + sdesc->tfm = tfm;
> + rc = crypto_shash_init(sdesc);
> + if (rc)
> + goto err;
> +
> + /* first hash the previous digest */
> + crypto_shash_update(sdesc, policydigest, *plen);
> +
> + /* then hash the command code */
> + put_unaligned_be32(cmd, code);
> + crypto_shash_update(sdesc, code, 4);
> +
> + /* commands that need special handling */
> + if (cmd = TPM2_CC_POLICY_COUNTER_TIMER) {
> + SHASH_DESC_ON_STACK(sdesc1, tfm);
> +
> + sdesc1->tfm = tfm;
> +
> + /* counter timer policies are double hashed */
> + crypto_shash_digest(sdesc1, policy, len,
> + digest);
> + policy = digest;
> + len = *plen;
> + }
> +
> + crypto_shash_update(sdesc, policy, len);
> +
> + /* now output the intermediate to the policydigest */
> + crypto_shash_final(sdesc, policydigest);
> +
> + }
> + rc = 0;
> +
> + err:
> + crypto_free_shash(tfm);
> + return rc;
> +}
> +
> +int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len)
> +{
> + const int SCRATCH_SIZE = PAGE_SIZE;
> + u8 *buf = kmalloc(2 * SCRATCH_SIZE, GFP_KERNEL);
> + u8 *work = buf + SCRATCH_SIZE;
> + u8 *ptr;
> + u8 *end_work = work + SCRATCH_SIZE;
> + int i, ret;
> +
> + if (!buf)
> + return -ENOMEM;
> +
> + for (i = 0; i < pols->count; i++) {
> + u8 *seq, *tag;
> + u32 cmd = pols->code[i];
> +
> + if (WARN(work - buf + 14 + pols->len[i] > 2 * SCRATCH_SIZE,
> + "BUG: scratch buffer is too small"))
> + return -EINVAL;
> +
> + work = asn1_encode_sequence(work, end_work, NULL, -1);
> + seq = work;
> +
> + work = asn1_encode_tag(work, end_work, 0, NULL, -1);
> + tag = work;
> +
> + work = asn1_encode_integer(work, end_work, cmd);
> + asn1_encode_tag(tag, end_work, 0, NULL, work - tag);
> +
> + work = asn1_encode_tag(work, end_work, 1, NULL, -1);
> + tag = work;
> +
> + work = asn1_encode_octet_string(work, end_work,
> + pols->policies[i],
> + pols->len[i]);
> +
> + asn1_encode_tag(tag, end_work, 1, NULL, work - tag);
> +
> + seq = asn1_encode_sequence(seq, end_work, NULL, work - seq);
> + if (IS_ERR(seq)) {
> + ret = PTR_ERR(seq);
> + goto err;
> + }
> + }
> + ptr = asn1_encode_sequence(buf, buf + SCRATCH_SIZE, buf + PAGE_SIZE,
> + work - buf - PAGE_SIZE);
> + if (IS_ERR(ptr)) {
> + ret = PTR_ERR(ptr);
> + goto err;
> + }
> +
> + *data = buf;
> + *len = ptr - buf;
> +
> + return 0;
> +
> + err:
> + kfree(buf);
> + return ret;
> +}
> +
> +int tpm2_start_policy_session(struct tpm_chip *chip, u16 hash, u32 *handle)
> +{
> + struct tpm_buf buf;
> + int rc;
> + int i;
> +
> + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
> + if (rc)
> + return rc;
> +
> + /* NULL salt key handle */
> + tpm_buf_append_u32(&buf, TPM2_RH_NULL);
> +
> + /* NULL bind key handle */
> + tpm_buf_append_u32(&buf, TPM2_RH_NULL);
> +
> + /* empty nonce caller */
> + tpm_buf_append_u16(&buf, 20);
> + for (i = 0; i < 20; i++)
> + tpm_buf_append_u8(&buf, 0);
> +
> + /* empty auth */
> + tpm_buf_append_u16(&buf, 0);
> +
> + /* session type policy */
> + tpm_buf_append_u8(&buf, 0x01);
> +
> + /* symmetric encryption parameters */
> +
> + /* symmetric algorithm */
> + tpm_buf_append_u16(&buf, TPM_ALG_NULL);
> +
> + /* hash algorithm for session */
> + tpm_buf_append_u16(&buf, hash);
> +
> + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> + if (rc)
> + goto out;
> +
> + *handle = get_unaligned_be32(buf.data + TPM_HEADER_SIZE);
> +
> + out:
> + tpm_buf_destroy(&buf);
> +
> + return rc <= 0 ? rc : -EPERM;
> +}
> +
> +int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
> + u32 *handle)
> +{
> + int i, rc;
> + const char *failure;
> +
> + rc = tpm2_start_policy_session(chip, pols->hash, handle);
> + if (rc)
> + return rc;
> +
> + for (i = 0; i < pols->count; i++) {
> + u32 cmd = pols->code[i];
> + struct tpm_buf buf;
> +
> + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
> + if (rc)
> + return rc;
> +
> + tpm_buf_append_u32(&buf, *handle);
> +
> + switch (cmd) {
> + case TPM2_CC_POLICY_PCR:
> + failure = "PCR";
> + /*
> + * for reasons best known to the TCG we have
> + * to reverse the two arguments to send to the
> + * policy command
> + */
> + tpm_buf_append_u16(&buf, pols->hash_size);
> + tpm_buf_append(&buf, pols->policies[i] + pols->len[i] -
> + pols->hash_size, pols->hash_size);
> + tpm_buf_append(&buf, pols->policies[i],
> + pols->len[i] - pols->hash_size);
> + break;
> + default:
> + failure = "unknown policy";
> + break;
> + }
> +
> + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> + tpm_buf_destroy(&buf);
> + if (rc) {
> + printk(KERN_NOTICE "TPM policy %s failed, rc=%d\n",
> + failure, rc);
> + tpm2_flush_context(chip, *handle);
> + *handle = 0;
> + return -EPERM;
> + }
> + }
> +
> + return 0;
> +}
> diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
> new file mode 100644
> index 000000000000..46bf1f0a9325
> --- /dev/null
> +++ b/security/keys/trusted-keys/tpm2-policy.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +struct tpm2_key_context {
> + u32 parent;
> + const u8 *pub;
> + u32 pub_len;
> + const u8 *priv;
> + u32 priv_len;
> + const u8 *policies[TPM2_MAX_POLICIES];
> + u32 policy_code[TPM2_MAX_POLICIES];
> + u16 policy_len[TPM2_MAX_POLICIES];
> + u8 policy_count;
> +};
> +
> +struct tpm2_policies {
> + u32 code[TPM2_MAX_POLICIES];
> + u8 *policies[TPM2_MAX_POLICIES];
> + u16 len[TPM2_MAX_POLICIES];
> + u8 count;
> + u16 hash;
> + u16 hash_size;
> +};
> +
> +int tpm2_key_policy_process(struct tpm2_key_context *ctx,
> + struct trusted_key_payload *payload);
> +int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
> + u8 *policydigest, u32 *plen);
> +int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
> +int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
> + u32 *handle);
> diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
> index 3f6a9d01d1e5..0c241d000120 100644
> --- a/security/keys/trusted-keys/tpm2key.asn1
> +++ b/security/keys/trusted-keys/tpm2key.asn1
> @@ -1,11 +1,24 @@
> ---
> --- ASN.1 for for TPM 2.0 keys
> ---
> +--- Note: This isn't quite the definition in the standard
> +--- However, the Linux asn.1 parser doesn't understand
> +--- [2] EXPLICIT SEQUENCE OF OPTIONAL
> +--- So there's an extra intermediate TPMPolicySequence
> +--- definition to work around this
>
> TPMKey ::= SEQUENCE {
> type OBJECT IDENTIFIER ({tpm2_key_type}),
> emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL,
> + policy [1] EXPLICIT TPMPolicySequence OPTIONAL,
> parent INTEGER ({tpm2_key_parent}),
> pubkey OCTET STRING ({tpm2_key_pub}),
> privkey OCTET STRING ({tpm2_key_priv})
> }
> +
> +TPMPolicySequence ::= SEQUENCE OF TPMPolicy
> +
> +TPMPolicy ::= SEQUENCE {
> + commandCode [0] EXPLICIT INTEGER ({tpm2_key_code}),
> + commandPolicy [1] EXPLICIT OCTET STRING ({tpm2_key_policy})
> + }
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index 0f026656d635..2f62db74e771 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -1065,6 +1065,8 @@ static void trusted_rcu_free(struct rcu_head *rcu)
> struct trusted_key_payload *p;
>
> p = container_of(rcu, struct trusted_key_payload, rcu);
> +
> + kfree_sensitive(p->policies);
> kfree_sensitive(p);
> }
>
> @@ -1174,7 +1176,11 @@ static long trusted_read(const struct key *key, char *buffer,
> */
> static void trusted_destroy(struct key *key)
> {
> - kfree_sensitive(key->payload.data[0]);
> + struct trusted_key_payload *p;
> +
> + p = key->payload.data[0];
> + kfree_sensitive(p->policies);
> + kfree_sensitive(p);
> }
>
> struct key_type key_type_trusted = {
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 905c5ca4d51c..98c65431ca75 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -17,6 +17,7 @@
> #include <asm/unaligned.h>
>
> #include "tpm2key.asn1.h"
> +#include "tpm2-policy.h"
>
> static struct tpm2_hash tpm2_hash_map[] = {
> {HASH_ALGO_SHA1, TPM_ALG_SHA1},
> @@ -62,6 +63,21 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
> work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
> }
>
> + if (payload->policies) {
> + u8 *encoded_pols;
> + u32 encoded_pol_len;
> + int ret;
> +
> + ret = tpm2_encode_policy(payload->policies, &encoded_pols,
> + &encoded_pol_len);
> + if (ret)
> + return ret;
> +
> + work = asn1_encode_tag(work, end_work, 1, encoded_pols,
> + encoded_pol_len);
> + kfree(encoded_pols);
> + }
> +
> /*
> * Assume both octet strings will encode to a 2 byte definite length
> *
> @@ -85,14 +101,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
> return work1 - payload->blob;
> }
>
> -struct tpm2_key_context {
> - u32 parent;
> - const u8 *pub;
> - u32 pub_len;
> - const u8 *priv;
> - u32 priv_len;
> -};
> -
> static int tpm2_key_decode(struct trusted_key_payload *payload,
> struct trusted_key_options *options,
> u8 **buf)
> @@ -115,6 +123,12 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
> if (!blob)
> return -ENOMEM;
>
> + ret = tpm2_key_policy_process(&ctx, payload);
> + if (ret) {
> + kfree(blob);
> + return ret;
> + }
> +
> *buf = blob;
> options->keyhandle = ctx.parent;
>
> @@ -248,6 +262,42 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
> if (!options->keyhandle)
> return -EINVAL;
>
> + if (options->pcrinfo_len != 0) {
> + struct tpm2_policies *pols;
> + static u8 *scratch;
> + /* 4 array len, 2 hash alg */
> + const int len = 4 + 2 + options->pcrinfo_len;
> +
> + pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
> + if (!pols)
> + return -ENOMEM;
> +
> + pols->count = 1;
> + pols->len[0] = len;
> + scratch = (u8 *)(pols + 1);
> + pols->policies[0] = scratch;
> + pols->code[0] = TPM2_CC_POLICY_PCR;
> +
> + put_unaligned_be32(1, &scratch[0]);
> + put_unaligned_be16(hash, &scratch[4]);
> + memcpy(&scratch[6], options->pcrinfo, options->pcrinfo_len);
> + payload->policies = pols;
> + }
> +
> + if (options->policydigest_len != 0 && payload->policies) {
> + /* can't specify both a digest and a policy */
> + return -EINVAL;
> + }
> +
> + if (payload->policies) {
> + rc = tpm2_generate_policy_digest(payload->policies,
> + options->hash,
> + options->policydigest,
> + &options->policydigest_len);
> + if (rc)
> + return rc;
> + }
> +
> rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
> if (rc)
> return rc;
> @@ -456,21 +506,37 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
> u16 data_len;
> u8 *data;
> int rc;
> + u32 policyhandle;
> +
> + if (payload->policies && options->policyhandle)
> + /* can't have both a passed in policy and a key resident one */
> + return -EINVAL;
>
> rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> if (rc)
> return rc;
>
> + if (payload->policies) {
> + rc = tpm2_get_policy_session(chip, payload->policies,
> + &policyhandle);
> + if (rc)
> + return rc;
> + } else {
> + policyhandle = options->policyhandle;
> + }
> +
> tpm_buf_append_u32(&buf, blob_handle);
> tpm2_buf_append_auth(&buf,
> - options->policyhandle ?
> - options->policyhandle : TPM2_RS_PW,
> + policyhandle ?
> + policyhandle : TPM2_RS_PW,
> NULL /* nonce */, 0,
> TPM2_SA_CONTINUE_SESSION,
> options->blobauth /* hmac */,
> options->blobauth_len);
>
> rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> + if (payload->policies)
> + tpm2_flush_context(chip, policyhandle);
> if (rc > 0)
> rc = -EPERM;
>
> --
> 2.26.2
>
That is all I want to say right now as this does not apply to the
existing mainline.
/Jarkko
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys
@ 2020-09-14 19:37 ` Jarkko Sakkinen
0 siblings, 0 replies; 14+ messages in thread
From: Jarkko Sakkinen @ 2020-09-14 19:37 UTC (permalink / raw)
To: James Bottomley
Cc: linux-integrity, Mimi Zohar, David Woodhouse, keyrings, David Howells
No sure why this is v11. I don't think we have reviewed this series that
many times.
On Sat, Sep 12, 2020 at 10:39:36AM -0700, James Bottomley wrote:
> This commit adds the ability to specify a PCR lock policy to TPM2
> keys. There is a complexity in that the creator of the key must chose
> either to use a PCR lock policy or to use authentication. At the
> current time they can't use both due to a complexity with the way
> authentication works when policy registers are in use. The way to
> construct a pcrinfo statement for a key is simply to use the
> TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
> hash of all their values in order of ascending PCR number.
>
> For simplicity, we require the policy name hash and the hash used for
> the PCRs to be the same. Thus to construct a policy around the value
It would be better to write "name hash algorithm" and "policy hash
algorithm".
> of the resettable PCR 16 using the sha1 bank, first reset the pcr to
~~~
PCR
> zero giving a hash of all zeros as:
>
> 6768033e216468247bd031a0a2d9876d79818f8f
>
> Then the TPMS_PCR_SELECT value for PCR 16 is
>
> 03000001
>
> So create a new 32 byte key with a policy policy locking the key to
> this value of PCR 16 with a parent key of 81000001 would be:
>
> keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
>
Extra newline.
> ---
>
> v2: fix for new ASN.1 API eliminating hack in place and check lengths
> v8: recover patch and fix offsets for hash and size
> v9: fix cut and paste error in commit log
> v10: update for kfree_sensitive()
> v11: add policy to ASN.1 key format description
> ---
> .../security/keys/trusted-encrypted.rst | 36 +-
> include/keys/trusted-type.h | 5 +-
> include/linux/tpm.h | 5 +
> security/keys/Kconfig | 2 +
> security/keys/trusted-keys/Makefile | 2 +-
> security/keys/trusted-keys/tpm2-policy.c | 372 ++++++++++++++++++
> security/keys/trusted-keys/tpm2-policy.h | 30 ++
> security/keys/trusted-keys/tpm2key.asn1 | 13 +
> security/keys/trusted-keys/trusted_tpm1.c | 8 +-
> security/keys/trusted-keys/trusted_tpm2.c | 86 +++-
> 10 files changed, 545 insertions(+), 14 deletions(-)
> create mode 100644 security/keys/trusted-keys/tpm2-policy.c
> create mode 100644 security/keys/trusted-keys/tpm2-policy.h
>
> diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
> index eb639bb24fcc..8b7853a277bc 100644
> --- a/Documentation/security/keys/trusted-encrypted.rst
> +++ b/Documentation/security/keys/trusted-encrypted.rst
> @@ -60,7 +60,10 @@ Usage::
> (40 ascii zeros)
> blobauth= ascii hex auth for sealed data default 0x00...
> (40 ascii zeros)
> - pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
> + pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no
> + default) on TPM 1.2 and a TPMS_PCR_SELECTION
> + coupled with a hash of all the selected PCRs on
> + TPM 2.0 using the selected hash.
> pcrlock= pcr number to be extended to "lock" blob
> migratable= 0|1 indicating permission to reseal to new PCR values,
> default 1 (resealing allowed)
> @@ -151,6 +154,20 @@ Load a trusted key from the saved blob::
> f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
> e4a8aea2b607ec96931e6f4d4fe563ba
>
> +Create a trusted key on TPM 2.0 using an all zero value of PCR16 and
> +using the NV storage root 81000001 as the parent::
> +
> + $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u
> +
> +Note the TPMS_PCR_SELECT value for PCR 16 is 03000001 because all
> +current TPMs have 24 PCRs, so the initial 03 says there are three
> +following bytes of selection and then because the bytes are big
> +endian, 16 is bit zero of byte 2. the hash is the sha1 sum of all
> +zeros (the value of PCR 16)::
> +
> + $ dd if=/dev/zero bs=1 count=20 2>/dev/null|sha1sum
> + 6768033e216468247bd031a0a2d9876d79818f8f
> +
> Reseal a trusted key under new pcr values::
>
> $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
> @@ -221,11 +238,17 @@ policy::
> TPMKey ::= SEQUENCE {
> type OBJECT IDENTIFIER
> emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
> + policy [1] EXPLICIT SEQUENCE OF TPMPolicy OPTIONAL
> parent INTEGER
> pubkey OCTET STRING
> privkey OCTET STRING
> }
>
> + TPMPolicy ::= SEQUENCE {
> + CommandCode [0] EXPLICIT INTEGER
> + CommandPolicy [1] EXPLICIT OCTET STRING
> + }
> +
> type is what distinguishes the key even in binary form since the OID
> is provided by the TCG to be unique and thus forms a recognizable
> binary pattern at offset 3 in the key. The OIDs currently made
> @@ -251,6 +274,17 @@ is false or not present, the key requires an explicit authorization
> phrase. This is used by most user space consumers to decide whether
> to prompt for a password.
>
> +policy represents a sequence of one or more policy statements that
> +must be executed successfully into a session policy register. If
> +policy isn't present then no policy is required to unlock the key, but
> +if it is, commandCode is the TPM 2.0 command code of the policy
> +instruction that must be executed and CommandPolicy represents the
> +binary parameter area of the policy command.
> +
> +Note that the current sequential execution requirement means that only
> +AND based policy can be constructed at the moment, so TPM2_PolicyOR is
> +not currently supported.
> +
> parent represents the parent key handle, either in the 0x81 MSO space,
> like 0x81000001 for the RSA primary storage key. Userspace programmes
> also support specifying the primary handle in the 0x40 MSO space. If
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index b2d87ad21714..c117bf598230 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -14,9 +14,11 @@
> #define MIN_KEY_SIZE 32
> #define MAX_KEY_SIZE 128
> #define MAX_BLOB_SIZE 512
> -#define MAX_PCRINFO_SIZE 64
> +#define MAX_PCRINFO_SIZE 128
> #define MAX_DIGEST_SIZE 64
>
> +#define TPM2_MAX_POLICIES 16
> +
> struct trusted_key_payload {
> struct rcu_head rcu;
> unsigned int key_len;
> @@ -25,6 +27,7 @@ struct trusted_key_payload {
> unsigned char old_format;
> unsigned char key[MAX_KEY_SIZE + 1];
> unsigned char blob[MAX_BLOB_SIZE];
> + struct tpm2_policies *policies;
> };
>
> struct trusted_key_options {
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 35224860fd0c..254c33086288 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -230,10 +230,14 @@ enum tpm2_command_codes {
> TPM2_CC_CONTEXT_LOAD = 0x0161,
> TPM2_CC_CONTEXT_SAVE = 0x0162,
> TPM2_CC_FLUSH_CONTEXT = 0x0165,
> + TPM2_CC_POLICY_AUTHVALUE = 0x016B,
> + TPM2_CC_POLICY_COUNTER_TIMER = 0x016D,
> + TPM2_CC_START_AUTH_SESS = 0x0176,
> TPM2_CC_VERIFY_SIGNATURE = 0x0177,
> TPM2_CC_GET_CAPABILITY = 0x017A,
> TPM2_CC_GET_RANDOM = 0x017B,
> TPM2_CC_PCR_READ = 0x017E,
> + TPM2_CC_POLICY_PCR = 0x017F,
> TPM2_CC_PCR_EXTEND = 0x0182,
> TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
> TPM2_CC_HASH_SEQUENCE_START = 0x0186,
> @@ -242,6 +246,7 @@ enum tpm2_command_codes {
> };
>
> enum tpm2_permanent_handles {
> + TPM2_RH_NULL = 0x40000007,
> TPM2_RS_PW = 0x40000009,
> };
>
> diff --git a/security/keys/Kconfig b/security/keys/Kconfig
> index 8fbfedf6d1cc..d9977359b8a6 100644
> --- a/security/keys/Kconfig
> +++ b/security/keys/Kconfig
> @@ -74,6 +74,8 @@ config TRUSTED_KEYS
> select CRYPTO
> select CRYPTO_HMAC
> select CRYPTO_SHA1
> + select CRYPTO_SHA256
> + select CRYPTO_SHA512
> select CRYPTO_HASH_INFO
> select ASN1_ENCODER
> help
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
> index e0198641eff2..194febacf362 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -5,4 +5,4 @@
>
> obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
> trusted-y += trusted_tpm1.o
> -trusted-y += trusted_tpm2.o tpm2key.asn1.o
> +trusted-y += trusted_tpm2.o tpm2key.asn1.o tpm2-policy.o
> diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
> new file mode 100644
> index 000000000000..080a76e879fd
> --- /dev/null
> +++ b/security/keys/trusted-keys/tpm2-policy.c
> @@ -0,0 +1,372 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
> + */
> +
> +#include <linux/asn1_encoder.h>
> +#include <linux/err.h>
> +#include <linux/types.h>
> +#include <linux/printk.h>
> +#include <linux/string.h>
> +#include <linux/tpm.h>
> +
> +#include <asm/unaligned.h>
> +
> +#include <crypto/hash.h>
> +
> +#include <keys/trusted-type.h>
> +#include <keys/trusted_tpm.h>
> +
> +#include "tpm2key.asn1.h"
> +#include "tpm2-policy.h"
> +
> +int tpm2_key_code(void *context, size_t hdrlen,
> + unsigned char tag,
> + const void *value, size_t vlen)
> +{
> + struct tpm2_key_context *ctx = context;
> + u32 code = 0;
> + const u8 *v = value;
> + int i;
> +
> + for (i = 0; i < vlen; i++) {
> + code <<= 8;
> + code |= v[i];
> + }
> +
> + ctx->policy_code[ctx->policy_count] = code;
> +
> + return 0;
> +}
> +
> +int tpm2_key_policy(void *context, size_t hdrlen,
> + unsigned char tag,
> + const void *value, size_t vlen)
> +{
> + struct tpm2_key_context *ctx = context;
> +
> + ctx->policies[ctx->policy_count] = value;
> + ctx->policy_len[ctx->policy_count++] = vlen;
> +
> + return 0;
> +}
As non-static symbols, and in general to make the code more
understandable, must be documeted.
> +
> +/* we only support a limited number of policy statement so
> + * make sure we don't have anything we can't support
> + */
> +static int tpm2_validate_policy(struct tpm2_policies *pols)
> +{
> + int i;
> +
> + if (pols->count == 0)
> + return 0;
> +
> + for (i = 0; i < pols->count; i++) {
> + switch (pols->code[i]) {
> + case TPM2_CC_POLICY_COUNTER_TIMER:
> + case TPM2_CC_POLICY_PCR:
> + case TPM2_CC_POLICY_AUTHVALUE:
> + break;
> + default:
> + printk(KERN_INFO "tpm2 policy 0x%x is unsupported",
> + pols->code[i]);
> + return -EINVAL;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * tpm2_key_process_policy - collect the policty from the context
> + * @ctx: the context to collect from
> + * @payload: the payload structure to place it in
> + *
> + * THis function sizes the policy statements and allocates space
> + * within the payload to receive them before copying them over. It
> + * should be used after the ber decoder has completed successfully
> + */
> +int tpm2_key_policy_process(struct tpm2_key_context *ctx,
> + struct trusted_key_payload *payload)
> +{
> + int tot_len = 0;
> + u8 *buf;
> + int i, ret, len = 0;
> + struct tpm2_policies *pols;
> +
> + if (ctx->policy_count == 0)
> + return 0;
> +
> + for (i = 0; i < ctx->policy_count; i++)
> + tot_len += ctx->policy_len[i];
> + tot_len += sizeof(*pols);
> +
> + pols = kmalloc(tot_len, GFP_KERNEL);
> + if (!pols)
> + return -ENOMEM;
> +
> + payload->policies = pols;
> + buf = (u8 *)(pols + 1);
> +
> + for (i = 0; i < ctx->policy_count; i++) {
> + pols->policies[i] = &buf[len];
> + pols->len[i] = ctx->policy_len[i];
> + pols->code[i] = ctx->policy_code[i];
> + if (pols->len[i])
> + memcpy(pols->policies[i], ctx->policies[i],
> + ctx->policy_len[i]);
> + len += ctx->policy_len[i];
> + }
> + pols->count = ctx->policy_count;
> +
> + ret = tpm2_validate_policy(pols);
> + if (ret) {
> + kfree(pols);
> + payload->policies = NULL;
> + }
> +
> + /* capture the hash and size */
> +
> + /* the hash is the second algorithm */
> + pols->hash = get_unaligned_be16(&ctx->pub[4]);
> + /* and the digest appears after the attributes */
> + pols->hash_size = get_unaligned_be16(&ctx->pub[10]);
> +
> + return ret;
> +}
> +
> +int tpm2_generate_policy_digest(struct tpm2_policies *pols,
> + u32 hash, u8 *policydigest, u32 *plen)
> +{
> + int i;
> + struct crypto_shash *tfm;
> + int rc;
> +
> + if (pols->count == 0)
> + return 0;
> +
> + tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
> + if (IS_ERR(tfm))
> + return PTR_ERR(tfm);
> +
> + rc = crypto_shash_digestsize(tfm);
> + if (WARN(rc > MAX_DIGEST_SIZE,
> + "BUG: trusted key code has alg %s with digest too large (%d)",
> + hash_algo_name[hash], rc)) {
> + rc = -EINVAL;
> + goto err;
> + }
> +
> + pols->hash = hash;
> + pols->hash_size = rc;
> + *plen = rc;
> +
> + /* policy digests always start out all zeros */
> + memset(policydigest, 0, rc);
> +
> + for (i = 0; i < pols->count; i++) {
> + u8 *policy = pols->policies[i];
> + int len = pols->len[i];
> + u32 cmd = pols->code[i];
> + u8 digest[MAX_DIGEST_SIZE];
> + u8 code[4];
> + SHASH_DESC_ON_STACK(sdesc, tfm);
> +
> + sdesc->tfm = tfm;
> + rc = crypto_shash_init(sdesc);
> + if (rc)
> + goto err;
> +
> + /* first hash the previous digest */
> + crypto_shash_update(sdesc, policydigest, *plen);
> +
> + /* then hash the command code */
> + put_unaligned_be32(cmd, code);
> + crypto_shash_update(sdesc, code, 4);
> +
> + /* commands that need special handling */
> + if (cmd == TPM2_CC_POLICY_COUNTER_TIMER) {
> + SHASH_DESC_ON_STACK(sdesc1, tfm);
> +
> + sdesc1->tfm = tfm;
> +
> + /* counter timer policies are double hashed */
> + crypto_shash_digest(sdesc1, policy, len,
> + digest);
> + policy = digest;
> + len = *plen;
> + }
> +
> + crypto_shash_update(sdesc, policy, len);
> +
> + /* now output the intermediate to the policydigest */
> + crypto_shash_final(sdesc, policydigest);
> +
> + }
> + rc = 0;
> +
> + err:
> + crypto_free_shash(tfm);
> + return rc;
> +}
> +
> +int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len)
> +{
> + const int SCRATCH_SIZE = PAGE_SIZE;
> + u8 *buf = kmalloc(2 * SCRATCH_SIZE, GFP_KERNEL);
> + u8 *work = buf + SCRATCH_SIZE;
> + u8 *ptr;
> + u8 *end_work = work + SCRATCH_SIZE;
> + int i, ret;
> +
> + if (!buf)
> + return -ENOMEM;
> +
> + for (i = 0; i < pols->count; i++) {
> + u8 *seq, *tag;
> + u32 cmd = pols->code[i];
> +
> + if (WARN(work - buf + 14 + pols->len[i] > 2 * SCRATCH_SIZE,
> + "BUG: scratch buffer is too small"))
> + return -EINVAL;
> +
> + work = asn1_encode_sequence(work, end_work, NULL, -1);
> + seq = work;
> +
> + work = asn1_encode_tag(work, end_work, 0, NULL, -1);
> + tag = work;
> +
> + work = asn1_encode_integer(work, end_work, cmd);
> + asn1_encode_tag(tag, end_work, 0, NULL, work - tag);
> +
> + work = asn1_encode_tag(work, end_work, 1, NULL, -1);
> + tag = work;
> +
> + work = asn1_encode_octet_string(work, end_work,
> + pols->policies[i],
> + pols->len[i]);
> +
> + asn1_encode_tag(tag, end_work, 1, NULL, work - tag);
> +
> + seq = asn1_encode_sequence(seq, end_work, NULL, work - seq);
> + if (IS_ERR(seq)) {
> + ret = PTR_ERR(seq);
> + goto err;
> + }
> + }
> + ptr = asn1_encode_sequence(buf, buf + SCRATCH_SIZE, buf + PAGE_SIZE,
> + work - buf - PAGE_SIZE);
> + if (IS_ERR(ptr)) {
> + ret = PTR_ERR(ptr);
> + goto err;
> + }
> +
> + *data = buf;
> + *len = ptr - buf;
> +
> + return 0;
> +
> + err:
> + kfree(buf);
> + return ret;
> +}
> +
> +int tpm2_start_policy_session(struct tpm_chip *chip, u16 hash, u32 *handle)
> +{
> + struct tpm_buf buf;
> + int rc;
> + int i;
> +
> + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
> + if (rc)
> + return rc;
> +
> + /* NULL salt key handle */
> + tpm_buf_append_u32(&buf, TPM2_RH_NULL);
> +
> + /* NULL bind key handle */
> + tpm_buf_append_u32(&buf, TPM2_RH_NULL);
> +
> + /* empty nonce caller */
> + tpm_buf_append_u16(&buf, 20);
> + for (i = 0; i < 20; i++)
> + tpm_buf_append_u8(&buf, 0);
> +
> + /* empty auth */
> + tpm_buf_append_u16(&buf, 0);
> +
> + /* session type policy */
> + tpm_buf_append_u8(&buf, 0x01);
> +
> + /* symmetric encryption parameters */
> +
> + /* symmetric algorithm */
> + tpm_buf_append_u16(&buf, TPM_ALG_NULL);
> +
> + /* hash algorithm for session */
> + tpm_buf_append_u16(&buf, hash);
> +
> + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> + if (rc)
> + goto out;
> +
> + *handle = get_unaligned_be32(buf.data + TPM_HEADER_SIZE);
> +
> + out:
> + tpm_buf_destroy(&buf);
> +
> + return rc <= 0 ? rc : -EPERM;
> +}
> +
> +int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
> + u32 *handle)
> +{
> + int i, rc;
> + const char *failure;
> +
> + rc = tpm2_start_policy_session(chip, pols->hash, handle);
> + if (rc)
> + return rc;
> +
> + for (i = 0; i < pols->count; i++) {
> + u32 cmd = pols->code[i];
> + struct tpm_buf buf;
> +
> + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
> + if (rc)
> + return rc;
> +
> + tpm_buf_append_u32(&buf, *handle);
> +
> + switch (cmd) {
> + case TPM2_CC_POLICY_PCR:
> + failure = "PCR";
> + /*
> + * for reasons best known to the TCG we have
> + * to reverse the two arguments to send to the
> + * policy command
> + */
> + tpm_buf_append_u16(&buf, pols->hash_size);
> + tpm_buf_append(&buf, pols->policies[i] + pols->len[i] -
> + pols->hash_size, pols->hash_size);
> + tpm_buf_append(&buf, pols->policies[i],
> + pols->len[i] - pols->hash_size);
> + break;
> + default:
> + failure = "unknown policy";
> + break;
> + }
> +
> + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> + tpm_buf_destroy(&buf);
> + if (rc) {
> + printk(KERN_NOTICE "TPM policy %s failed, rc=%d\n",
> + failure, rc);
> + tpm2_flush_context(chip, *handle);
> + *handle = 0;
> + return -EPERM;
> + }
> + }
> +
> + return 0;
> +}
> diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
> new file mode 100644
> index 000000000000..46bf1f0a9325
> --- /dev/null
> +++ b/security/keys/trusted-keys/tpm2-policy.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +struct tpm2_key_context {
> + u32 parent;
> + const u8 *pub;
> + u32 pub_len;
> + const u8 *priv;
> + u32 priv_len;
> + const u8 *policies[TPM2_MAX_POLICIES];
> + u32 policy_code[TPM2_MAX_POLICIES];
> + u16 policy_len[TPM2_MAX_POLICIES];
> + u8 policy_count;
> +};
> +
> +struct tpm2_policies {
> + u32 code[TPM2_MAX_POLICIES];
> + u8 *policies[TPM2_MAX_POLICIES];
> + u16 len[TPM2_MAX_POLICIES];
> + u8 count;
> + u16 hash;
> + u16 hash_size;
> +};
> +
> +int tpm2_key_policy_process(struct tpm2_key_context *ctx,
> + struct trusted_key_payload *payload);
> +int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
> + u8 *policydigest, u32 *plen);
> +int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
> +int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
> + u32 *handle);
> diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
> index 3f6a9d01d1e5..0c241d000120 100644
> --- a/security/keys/trusted-keys/tpm2key.asn1
> +++ b/security/keys/trusted-keys/tpm2key.asn1
> @@ -1,11 +1,24 @@
> ---
> --- ASN.1 for for TPM 2.0 keys
> ---
> +--- Note: This isn't quite the definition in the standard
> +--- However, the Linux asn.1 parser doesn't understand
> +--- [2] EXPLICIT SEQUENCE OF OPTIONAL
> +--- So there's an extra intermediate TPMPolicySequence
> +--- definition to work around this
>
> TPMKey ::= SEQUENCE {
> type OBJECT IDENTIFIER ({tpm2_key_type}),
> emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL,
> + policy [1] EXPLICIT TPMPolicySequence OPTIONAL,
> parent INTEGER ({tpm2_key_parent}),
> pubkey OCTET STRING ({tpm2_key_pub}),
> privkey OCTET STRING ({tpm2_key_priv})
> }
> +
> +TPMPolicySequence ::= SEQUENCE OF TPMPolicy
> +
> +TPMPolicy ::= SEQUENCE {
> + commandCode [0] EXPLICIT INTEGER ({tpm2_key_code}),
> + commandPolicy [1] EXPLICIT OCTET STRING ({tpm2_key_policy})
> + }
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index 0f026656d635..2f62db74e771 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -1065,6 +1065,8 @@ static void trusted_rcu_free(struct rcu_head *rcu)
> struct trusted_key_payload *p;
>
> p = container_of(rcu, struct trusted_key_payload, rcu);
> +
> + kfree_sensitive(p->policies);
> kfree_sensitive(p);
> }
>
> @@ -1174,7 +1176,11 @@ static long trusted_read(const struct key *key, char *buffer,
> */
> static void trusted_destroy(struct key *key)
> {
> - kfree_sensitive(key->payload.data[0]);
> + struct trusted_key_payload *p;
> +
> + p = key->payload.data[0];
> + kfree_sensitive(p->policies);
> + kfree_sensitive(p);
> }
>
> struct key_type key_type_trusted = {
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 905c5ca4d51c..98c65431ca75 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -17,6 +17,7 @@
> #include <asm/unaligned.h>
>
> #include "tpm2key.asn1.h"
> +#include "tpm2-policy.h"
>
> static struct tpm2_hash tpm2_hash_map[] = {
> {HASH_ALGO_SHA1, TPM_ALG_SHA1},
> @@ -62,6 +63,21 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
> work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
> }
>
> + if (payload->policies) {
> + u8 *encoded_pols;
> + u32 encoded_pol_len;
> + int ret;
> +
> + ret = tpm2_encode_policy(payload->policies, &encoded_pols,
> + &encoded_pol_len);
> + if (ret)
> + return ret;
> +
> + work = asn1_encode_tag(work, end_work, 1, encoded_pols,
> + encoded_pol_len);
> + kfree(encoded_pols);
> + }
> +
> /*
> * Assume both octet strings will encode to a 2 byte definite length
> *
> @@ -85,14 +101,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
> return work1 - payload->blob;
> }
>
> -struct tpm2_key_context {
> - u32 parent;
> - const u8 *pub;
> - u32 pub_len;
> - const u8 *priv;
> - u32 priv_len;
> -};
> -
> static int tpm2_key_decode(struct trusted_key_payload *payload,
> struct trusted_key_options *options,
> u8 **buf)
> @@ -115,6 +123,12 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
> if (!blob)
> return -ENOMEM;
>
> + ret = tpm2_key_policy_process(&ctx, payload);
> + if (ret) {
> + kfree(blob);
> + return ret;
> + }
> +
> *buf = blob;
> options->keyhandle = ctx.parent;
>
> @@ -248,6 +262,42 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
> if (!options->keyhandle)
> return -EINVAL;
>
> + if (options->pcrinfo_len != 0) {
> + struct tpm2_policies *pols;
> + static u8 *scratch;
> + /* 4 array len, 2 hash alg */
> + const int len = 4 + 2 + options->pcrinfo_len;
> +
> + pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
> + if (!pols)
> + return -ENOMEM;
> +
> + pols->count = 1;
> + pols->len[0] = len;
> + scratch = (u8 *)(pols + 1);
> + pols->policies[0] = scratch;
> + pols->code[0] = TPM2_CC_POLICY_PCR;
> +
> + put_unaligned_be32(1, &scratch[0]);
> + put_unaligned_be16(hash, &scratch[4]);
> + memcpy(&scratch[6], options->pcrinfo, options->pcrinfo_len);
> + payload->policies = pols;
> + }
> +
> + if (options->policydigest_len != 0 && payload->policies) {
> + /* can't specify both a digest and a policy */
> + return -EINVAL;
> + }
> +
> + if (payload->policies) {
> + rc = tpm2_generate_policy_digest(payload->policies,
> + options->hash,
> + options->policydigest,
> + &options->policydigest_len);
> + if (rc)
> + return rc;
> + }
> +
> rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
> if (rc)
> return rc;
> @@ -456,21 +506,37 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
> u16 data_len;
> u8 *data;
> int rc;
> + u32 policyhandle;
> +
> + if (payload->policies && options->policyhandle)
> + /* can't have both a passed in policy and a key resident one */
> + return -EINVAL;
>
> rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> if (rc)
> return rc;
>
> + if (payload->policies) {
> + rc = tpm2_get_policy_session(chip, payload->policies,
> + &policyhandle);
> + if (rc)
> + return rc;
> + } else {
> + policyhandle = options->policyhandle;
> + }
> +
> tpm_buf_append_u32(&buf, blob_handle);
> tpm2_buf_append_auth(&buf,
> - options->policyhandle ?
> - options->policyhandle : TPM2_RS_PW,
> + policyhandle ?
> + policyhandle : TPM2_RS_PW,
> NULL /* nonce */, 0,
> TPM2_SA_CONTINUE_SESSION,
> options->blobauth /* hmac */,
> options->blobauth_len);
>
> rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> + if (payload->policies)
> + tpm2_flush_context(chip, policyhandle);
> if (rc > 0)
> rc = -EPERM;
>
> --
> 2.26.2
>
That is all I want to say right now as this does not apply to the
existing mainline.
/Jarkko
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys
2020-09-14 19:37 ` Jarkko Sakkinen
@ 2020-09-18 23:40 ` James Bottomley
-1 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-18 23:40 UTC (permalink / raw)
To: Jarkko Sakkinen
Cc: linux-integrity, Mimi Zohar, David Woodhouse, keyrings, David Howells
On Mon, 2020-09-14 at 22:37 +0300, Jarkko Sakkinen wrote:
> No sure why this is v11. I don't think we have reviewed this series
> that many times.
It was originally with the other patch set from the very beginning, so
it's definitely been sent 11 times.
> On Sat, Sep 12, 2020 at 10:39:36AM -0700, James Bottomley wrote:
> > This commit adds the ability to specify a PCR lock policy to TPM2
> > keys. There is a complexity in that the creator of the key must
> > chose either to use a PCR lock policy or to use authentication. At
> > the current time they can't use both due to a complexity with the
> > way authentication works when policy registers are in use. The way
> > to construct a pcrinfo statement for a key is simply to use the
> > TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
> > hash of all their values in order of ascending PCR number.
> >
> > For simplicity, we require the policy name hash and the hash used
> > for the PCRs to be the same. Thus to construct a policy around the
> > value
>
> It would be better to write "name hash algorithm" and "policy hash
> algorithm".
For simplicity we require the hash of the PCRs to use the same
algorithm as the policy hash
> > of the resettable PCR 16 using the sha1 bank, first reset the pcr
> > to
>
> ~~~
> PCR
>
> > zero giving a hash of all zeros as:
> >
> > 6768033e216468247bd031a0a2d9876d79818f8f
> >
> > Then the TPMS_PCR_SELECT value for PCR 16 is
> >
> > 03000001
> >
> > So create a new 32 byte key with a policy policy locking the key to
> > this value of PCR 16 with a parent key of 81000001 would be:
> >
> > keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1
> > pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u
> >
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.c
> > om>
> >
>
> Extra newline.
git am just elides this, but I can fix it and the other phrases up.]
[...]
> >
> > +int tpm2_key_policy(void *context, size_t hdrlen,
> > + unsigned char tag,
> > + const void *value, size_t vlen)
> > +{
> > + struct tpm2_key_context *ctx = context;
> > +
> > + ctx->policies[ctx->policy_count] = value;
> > + ctx->policy_len[ctx->policy_count++] = vlen;
> > +
> > + return 0;
> > +}
>
> As non-static symbols, and in general to make the code more
> understandable, must be documeted.
Will add docbook comment.
James
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys
@ 2020-09-18 23:40 ` James Bottomley
0 siblings, 0 replies; 14+ messages in thread
From: James Bottomley @ 2020-09-18 23:40 UTC (permalink / raw)
To: Jarkko Sakkinen
Cc: linux-integrity, Mimi Zohar, David Woodhouse, keyrings, David Howells
On Mon, 2020-09-14 at 22:37 +0300, Jarkko Sakkinen wrote:
> No sure why this is v11. I don't think we have reviewed this series
> that many times.
It was originally with the other patch set from the very beginning, so
it's definitely been sent 11 times.
> On Sat, Sep 12, 2020 at 10:39:36AM -0700, James Bottomley wrote:
> > This commit adds the ability to specify a PCR lock policy to TPM2
> > keys. There is a complexity in that the creator of the key must
> > chose either to use a PCR lock policy or to use authentication. At
> > the current time they can't use both due to a complexity with the
> > way authentication works when policy registers are in use. The way
> > to construct a pcrinfo statement for a key is simply to use the
> > TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
> > hash of all their values in order of ascending PCR number.
> >
> > For simplicity, we require the policy name hash and the hash used
> > for the PCRs to be the same. Thus to construct a policy around the
> > value
>
> It would be better to write "name hash algorithm" and "policy hash
> algorithm".
For simplicity we require the hash of the PCRs to use the same
algorithm as the policy hash
> > of the resettable PCR 16 using the sha1 bank, first reset the pcr
> > to
>
> ~~~
> PCR
>
> > zero giving a hash of all zeros as:
> >
> > 6768033e216468247bd031a0a2d9876d79818f8f
> >
> > Then the TPMS_PCR_SELECT value for PCR 16 is
> >
> > 03000001
> >
> > So create a new 32 byte key with a policy policy locking the key to
> > this value of PCR 16 with a parent key of 81000001 would be:
> >
> > keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1
> > pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u
> >
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.c
> > om>
> >
>
> Extra newline.
git am just elides this, but I can fix it and the other phrases up.]
[...]
> >
> > +int tpm2_key_policy(void *context, size_t hdrlen,
> > + unsigned char tag,
> > + const void *value, size_t vlen)
> > +{
> > + struct tpm2_key_context *ctx = context;
> > +
> > + ctx->policies[ctx->policy_count] = value;
> > + ctx->policy_len[ctx->policy_count++] = vlen;
> > +
> > + return 0;
> > +}
>
> As non-static symbols, and in general to make the code more
> understandable, must be documeted.
Will add docbook comment.
James
^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2020-09-18 23:47 UTC | newest]
Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-12 17:31 [PATCH v11 0/3] Trusted Key policy for TPM 2.0 James Bottomley
2020-09-12 17:31 ` James Bottomley
2020-09-12 17:39 ` James Bottomley
2020-09-12 17:39 ` James Bottomley
2020-09-12 17:39 ` [PATCH v11 1/3] security: keys: trusted: add PCR policy to TPM2 keys James Bottomley
2020-09-12 17:39 ` James Bottomley
2020-09-14 19:37 ` Jarkko Sakkinen
2020-09-14 19:37 ` Jarkko Sakkinen
2020-09-18 23:40 ` James Bottomley
2020-09-18 23:40 ` James Bottomley
2020-09-12 17:39 ` [PATCH v11 2/3] security: keys: trusted: add ability to specify arbitrary policy James Bottomley
2020-09-12 17:39 ` James Bottomley
2020-09-12 17:39 ` [PATCH v11 3/3] security: keys: trusted: implement counter/timer policy James Bottomley
2020-09-12 17:39 ` James Bottomley
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