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authorJames Bottomley <James.Bottomley@HansenPartnership.com>2021-01-27 11:06:15 -0800
committerJarkko Sakkinen <jarkko@kernel.org>2021-04-14 16:30:30 +0300
commitde66514d934d70ce73c302ce0644b54970fc7196 (patch)
treecf8eea210cf9b91cd35eea6e91907be37f21e0ad /security/keys
parent1c6476e9741e30be57e0b370d4405214f055607c (diff)
security: keys: trusted: fix TPM2 authorizations
In TPM 1.2 an authorization was a 20 byte number. The spec actually recommended you to hash variable length passwords and use the sha1 hash as the authorization. Because the spec doesn't require this hashing, the current authorization for trusted keys is a 40 digit hex number. For TPM 2.0 the spec allows the passing in of variable length passwords and passphrases directly, so we should allow that in trusted keys for ease of use. Update the 'blobauth' parameter to take this into account, so we can now use plain text passwords for the keys. so before keyctl add trusted kmk "new 32 blobauth=f572d396fae9206628714fb2ce00f72e94f2258fkeyhandle=81000001" @u after we will accept both the old hex sha1 form as well as a new directly supplied password: keyctl add trusted kmk "new 32 blobauth=hello keyhandle=81000001" @u Since a sha1 hex code must be exactly 40 bytes long and a direct password must be 20 or less, we use the length as the discriminator for which form is input. Note this is both and enhancement and a potential bug fix. The TPM 2.0 spec requires us to strip leading zeros, meaning empyty authorization is a zero length HMAC whereas we're currently passing in 20 bytes of zeros. A lot of TPMs simply accept this as OK, but the Microsoft TPM emulator rejects it with TPM_RC_BAD_AUTH, so this patch makes the Microsoft TPM emulator work with trusted keys. Fixes: 0fe5480303a1 ("keys, trusted: seal/unseal with TPM 2.0 chips") Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Diffstat (limited to 'security/keys')
-rw-r--r--security/keys/trusted-keys/trusted_tpm1.c32
-rw-r--r--security/keys/trusted-keys/trusted_tpm2.c10
2 files changed, 32 insertions, 10 deletions
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 493eb91ed017..1e13c9f7ea8c 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -791,13 +791,33 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
return -EINVAL;
break;
case Opt_blobauth:
- if (strlen(args[0].from) != 2 * SHA1_DIGEST_SIZE)
- return -EINVAL;
- res = hex2bin(opt->blobauth, args[0].from,
- SHA1_DIGEST_SIZE);
- if (res < 0)
- return -EINVAL;
+ /*
+ * TPM 1.2 authorizations are sha1 hashes passed in as
+ * hex strings. TPM 2.0 authorizations are simple
+ * passwords (although it can take a hash as well)
+ */
+ opt->blobauth_len = strlen(args[0].from);
+
+ if (opt->blobauth_len == 2 * TPM_DIGEST_SIZE) {
+ res = hex2bin(opt->blobauth, args[0].from,
+ TPM_DIGEST_SIZE);
+ if (res < 0)
+ return -EINVAL;
+
+ opt->blobauth_len = TPM_DIGEST_SIZE;
+ break;
+ }
+
+ if (tpm2 && opt->blobauth_len <= sizeof(opt->blobauth)) {
+ memcpy(opt->blobauth, args[0].from,
+ opt->blobauth_len);
+ break;
+ }
+
+ return -EINVAL;
+
break;
+
case Opt_migratable:
if (*args[0].from == '0')
pay->migratable = 0;
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index e2a0ed5d02f0..ac361aa7f3f1 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -97,10 +97,12 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
TPM_DIGEST_SIZE);
/* sensitive */
- tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len + 1);
+ tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len + 1);
+
+ tpm_buf_append_u16(&buf, options->blobauth_len);
+ if (options->blobauth_len)
+ tpm_buf_append(&buf, options->blobauth, options->blobauth_len);
- tpm_buf_append_u16(&buf, TPM_DIGEST_SIZE);
- tpm_buf_append(&buf, options->blobauth, TPM_DIGEST_SIZE);
tpm_buf_append_u16(&buf, payload->key_len + 1);
tpm_buf_append(&buf, payload->key, payload->key_len);
tpm_buf_append_u8(&buf, payload->migratable);
@@ -265,7 +267,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
NULL /* nonce */, 0,
TPM2_SA_CONTINUE_SESSION,
options->blobauth /* hmac */,
- TPM_DIGEST_SIZE);
+ options->blobauth_len);
rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
if (rc > 0)