[PATCH 2/2] keys, trusted: seal with a policy

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

Support for sealing with a authorization policy.

Two new options for trusted keys:

* 'policydigest=': provide an auth policy digest for sealing.
* 'policyhandle=': provide a policy session handle for unsealing.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 Documentation/security/keys-trusted-encrypted.txt | 34 ++++++++++-------
 drivers/char/tpm/tpm2-cmd.c                       | 24 ++++++++++--
 include/keys/trusted-type.h                       |  3 ++
 security/keys/trusted.c                           | 46 ++++++++++++++++++++++-
 4 files changed, 87 insertions(+), 20 deletions(-)

diff --git a/Documentation/security/keys-trusted-encrypted.txt b/Documentation/security/keys-trusted-encrypted.txt
index fd2565b..324ddf5 100644
--- a/Documentation/security/keys-trusted-encrypted.txt
+++ b/Documentation/security/keys-trusted-encrypted.txt
@@ -27,20 +27,26 @@ Usage:
     keyctl print keyid
 
     options:
-       keyhandle= ascii hex value of sealing key default 0x40000000 (SRK)
-       keyauth=	  ascii hex auth for sealing key default 0x00...i
-		  (40 ascii zeros)
-       blobauth=  ascii hex auth for sealed data default 0x00...
-		  (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)
-       pcrlock=	  pcr number to be extended to "lock" blob
-       migratable= 0|1 indicating permission to reseal to new PCR values,
-                   default 1 (resealing allowed)
-       hash=      hash algorithm name as a string. For TPM 1.x the only
-                  allowed value is sha1. For TPM 2.x the allowed values
-		  are sha1, sha256, sha384, sha512 and sm3-256.
+       keyhandle=    ascii hex value of sealing key default 0x40000000 (SRK)
+       keyauth=	     ascii hex auth for sealing key default 0x00...i
+                     (40 ascii zeros)
+       blobauth=     ascii hex auth for sealed data default 0x00...
+                     (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)
+       pcrlock=	     pcr number to be extended to "lock" blob
+       migratable=   0|1 indicating permission to reseal to new PCR values,
+                     default 1 (resealing allowed)
+       hash=         hash algorithm name as a string. For TPM 1.x the only
+                     allowed value is sha1. For TPM 2.x the allowed values
+                     are sha1, sha256, sha384, sha512 and sm3-256.
+       policydigest= digest for the authorization policy. must be calculated
+                     with the same hash algorithm as specified by the 'hash='
+                     option.
+       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.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index d9d0822..45a6340 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -478,12 +478,26 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	tpm_buf_append_u8(&buf, payload->migratable);
 
 	/* public */
-	tpm_buf_append_u16(&buf, 14);
+	if (options->policydigest)
+		tpm_buf_append_u16(&buf, 14 + options->digest_len);
+	else
+		tpm_buf_append_u16(&buf, 14);
 
 	tpm_buf_append_u16(&buf, TPM2_ALG_KEYEDHASH);
 	tpm_buf_append_u16(&buf, hash);
-	tpm_buf_append_u32(&buf, TPM2_ATTR_USER_WITH_AUTH);
-	tpm_buf_append_u16(&buf, 0); /* policy digest size */
+
+	/* policy */
+	if (options->policydigest) {
+		tpm_buf_append_u32(&buf, 0);
+		tpm_buf_append_u16(&buf, options->digest_len);
+		tpm_buf_append(&buf, options->policydigest,
+			       options->digest_len);
+	} else {
+		tpm_buf_append_u32(&buf, TPM2_ATTR_USER_WITH_AUTH);
+		tpm_buf_append_u16(&buf, 0);
+	}
+
+	/* public parameters */
 	tpm_buf_append_u16(&buf, TPM2_ALG_NULL);
 	tpm_buf_append_u16(&buf, 0);
 
@@ -613,7 +627,9 @@ static int tpm2_unseal(struct tpm_chip *chip,
 		return rc;
 
 	tpm_buf_append_u32(&buf, blob_handle);
-	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
+	tpm2_buf_append_auth(&buf,
+			     options->policyhandle ?
+			     options->policyhandle : TPM2_RS_PW,
 			     NULL /* nonce */, 0,
 			     0 /* session_attributes */,
 			     options->blobauth /* hmac */,
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index a6a1008..2c3f9f7 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -37,6 +37,9 @@ struct trusted_key_options {
 	unsigned char pcrinfo[MAX_PCRINFO_SIZE];
 	int pcrlock;
 	uint32_t hash;
+	uint32_t digest_len;
+	unsigned char *policydigest;
+	uint32_t policyhandle;
 };
 
 extern struct key_type key_type_trusted;
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index b5b0a55..b726a83 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -713,6 +713,8 @@ enum {
 	Opt_keyhandle, Opt_keyauth, Opt_blobauth,
 	Opt_pcrinfo, Opt_pcrlock, Opt_migratable,
 	Opt_hash,
+	Opt_policydigest,
+	Opt_policyhandle,
 };
 
 static const match_table_t key_tokens = {
@@ -726,6 +728,8 @@ static const match_table_t key_tokens = {
 	{Opt_pcrlock, "pcrlock=%s"},
 	{Opt_migratable, "migratable=%s"},
 	{Opt_hash, "hash=%s"},
+	{Opt_policydigest, "policydigest=%s"},
+	{Opt_policyhandle, "policyhandle=%s"},
 	{Opt_err, NULL}
 };
 
@@ -739,6 +743,7 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 	int res;
 	unsigned long handle;
 	unsigned long lock;
+	unsigned int policydigest_len;
 	int i;
 	int tpm2;
 
@@ -747,6 +752,8 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 		return tpm2;
 
 	opt->hash = tpm2 ? HASH_ALGO_SHA256 : HASH_ALGO_SHA1;
+	opt->digest_len = hash_digest_size[opt->hash];
+	policydigest_len = opt->digest_len;
 
 	while ((p = strsep(&c, " \t"))) {
 		if (*p == '\0' || *p == ' ' || *p == '\t')
@@ -802,6 +809,8 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 			for (i = 0; i < HASH_ALGO__LAST; i++) {
 				if (!strcmp(args[0].from, hash_algo_name[i])) {
 					opt->hash = i;
+					opt->digest_len =
+						hash_digest_size[opt->hash];
 					break;
 				}
 			}
@@ -812,10 +821,37 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			}
 			break;
+		case Opt_policydigest:
+			if (!tpm2 ||
+			    strlen(args[0].from) != (2 * opt->digest_len))
+				return -EINVAL;
+			kfree(opt->policydigest);
+			opt->policydigest = kzalloc(opt->digest_len,
+						    GFP_KERNEL);
+			if (!opt->policydigest)
+				return -ENOMEM;
+			res = hex2bin(opt->policydigest, args[0].from,
+				      opt->digest_len);
+			if (res < 0)
+				return -EINVAL;
+			policydigest_len = opt->digest_len;
+			break;
+		case Opt_policyhandle:
+			if (!tpm2)
+				return -EINVAL;
+			res = kstrtoul(args[0].from, 16, &handle);
+			if (res < 0)
+				return -EINVAL;
+			opt->policyhandle = handle;
+			break;
 		default:
 			return -EINVAL;
 		}
 	}
+
+	if (opt->policydigest && policydigest_len != opt->digest_len)
+		return -EINVAL;
+
 	return 0;
 }
 
@@ -904,6 +940,12 @@ static struct trusted_key_options *trusted_options_alloc(void)
 	return options;
 }
 
+static void trusted_options_free(struct trusted_key_options *options)
+{
+	kfree(options->policydigest);
+	kfree(options);
+}
+
 static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
 {
 	struct trusted_key_payload *p = NULL;
@@ -1010,7 +1052,7 @@ static int trusted_instantiate(struct key *key,
 		ret = pcrlock(options->pcrlock);
 out:
 	kfree(datablob);
-	kfree(options);
+	trusted_options_free(options);
 	if (!ret)
 		rcu_assign_keypointer(key, payload);
 	else
@@ -1098,7 +1140,7 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
 	call_rcu(&p->rcu, trusted_rcu_free);
 out:
 	kfree(datablob);
-	kfree(new_o);
+	trusted_options_free(new_o);
 	return ret;
 }
 
-- 
2.5.0