diff mbox series

[5.10,258/530] security: keys: trusted: fix TPM2 authorizations

Message ID 20210512144828.313826968@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH May 12, 2021, 2:46 p.m. UTC 
From: James Bottomley <James.Bottomley@HansenPartnership.com>

[ Upstream commit de66514d934d70ce73c302ce0644b54970fc7196 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/keys/trusted-type.h               |  1 +
 security/keys/trusted-keys/trusted_tpm1.c | 32 ++++++++++++++++++-----
 security/keys/trusted-keys/trusted_tpm2.c | 10 ++++---
 3 files changed, 33 insertions(+), 10 deletions(-)

Comments

Pavel Machek May 15, 2021, 8:21 a.m. UTC | #1 
Hi!

> [ Upstream commit de66514d934d70ce73c302ce0644b54970fc7196 ]

> 

> 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.


I guess break should now be deleted. If tools don't warn about this,
they should.

> +			if (tpm2 && opt->blobauth_len <= sizeof(opt->blobauth)) {

> +				memcpy(opt->blobauth, args[0].from,

> +				       opt->blobauth_len);

> +				break;

> +			}

> +

> +			return -EINVAL;

> +

>  			break;

> +


Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Pavel Machek May 15, 2021, 8:23 a.m. UTC | #2 
Hi!

Clean up unreachable code.

Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>


diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 230c0b27b77d..5bae4ed73c4d 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -813,11 +813,7 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				       opt->blobauth_len);
 				break;
 			}
-
 			return -EINVAL;
-
-			break;
-
 		case Opt_migratable:
 			if (*args[0].from == '0')
 				pay->migratable = 0;


-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
diff mbox series

Patch

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index a94c03a61d8f..b2ed3481c6a0 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -30,6 +30,7 @@  struct trusted_key_options {
 	uint16_t keytype;
 	uint32_t keyhandle;
 	unsigned char keyauth[TPM_DIGEST_SIZE];
+	uint32_t blobauth_len;
 	unsigned char blobauth[TPM_DIGEST_SIZE];
 	uint32_t pcrinfo_len;
 	unsigned char pcrinfo[MAX_PCRINFO_SIZE];
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 7a937c3c5283..230c0b27b77d 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 c87c4df8703d..4c19d3abddbe 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)