[PATCH v2 3/3] keys, trusted: seal with a TPM2 authorization policy
From: Jarkko Sakkinen
Date: Sun Dec 13 2015 - 10:43:04 EST
TPM2 supports authorization policies, which are essentially
combinational logic statements repsenting the conditions where the data
can be unsealed based on the TPM state. This patch enables to use
authorization policies to seal trusted keys.
Two following new options have been added for trusted keys:
* 'policydigest=': provide an auth policy digest for sealing.
* 'policyhandle=': provide a policy session handle for unsealing.
If 'hash=' option is supplied after 'policydigest=' option, this
will result an error because the state of the option would become
mixed.
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Tested-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
---
Documentation/security/keys-trusted-encrypted.txt | 34 +++++++++++++----------
drivers/char/tpm/tpm2-cmd.c | 24 +++++++++++++---
include/keys/trusted-type.h | 4 +++
security/keys/trusted.c | 26 +++++++++++++++++
4 files changed, 70 insertions(+), 18 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..42cf2d9 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -18,6 +18,7 @@
#define MAX_KEY_SIZE 128
#define MAX_BLOB_SIZE 512
#define MAX_PCRINFO_SIZE 64
+#define MAX_DIGEST_SIZE 64
struct trusted_key_payload {
struct rcu_head rcu;
@@ -37,6 +38,9 @@ struct trusted_key_options {
unsigned char pcrinfo[MAX_PCRINFO_SIZE];
int pcrlock;
uint32_t hash;
+ uint32_t digest_len;
+ unsigned char policydigest[MAX_DIGEST_SIZE];
+ uint32_t policyhandle;
};
extern struct key_type key_type_trusted;
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 8f1300c..e15baf7 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}
};
@@ -748,6 +752,7 @@ 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];
while ((p = strsep(&c, " \t"))) {
if (*p == '\0' || *p == ' ' || *p == '\t')
@@ -802,9 +807,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
opt->pcrlock = lock;
break;
case Opt_hash:
+ if (test_bit(Opt_policydigest, &token_mask))
+ return -EINVAL;
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;
}
}
@@ -815,6 +824,23 @@ 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;
+ res = hex2bin(opt->policydigest, args[0].from,
+ opt->digest_len);
+ if (res < 0)
+ return -EINVAL;
+ 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;
}
--
2.5.0
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