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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: linux-integrity@vger.kernel.org
Cc: Mimi Zohar <zohar@linux.ibm.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	David Woodhouse <dwmw2@infradead.org>,
	keyrings@vger.kernel.org
Subject: [PATCH v5 3/6] security: keys: trusted fix tpm2 authorizations
Date: Thu, 30 Jan 2020 11:18:09 +0100
Message-ID: <20200130101812.6271-4-James.Bottomley@HansenPartnership.com> (raw)
In-Reply-To: <20200130101812.6271-1-James.Bottomley@HansenPartnership.com>

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=f572d396fae9206628714fb2ce00f72e94f2258f"

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"

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.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 include/keys/trusted-type.h               |  1 +
 security/keys/trusted-keys/trusted_tpm1.c | 26 +++++++++++++++++++++-----
 security/keys/trusted-keys/trusted_tpm2.c | 10 ++++++----
 3 files changed, 28 insertions(+), 9 deletions(-)

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 d2c5ec1e040b..3f33d3f74d3c 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -781,12 +781,28 @@ 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)
+			/*
+			 * 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;
+			} else if (tpm2 &&
+				   opt->blobauth_len <= sizeof(opt->blobauth)) {
+				memcpy(opt->blobauth, args[0].from,
+				       opt->blobauth_len);
+			} else {
 				return -EINVAL;
+			}
+
 			break;
 		case Opt_migratable:
 			if (*args[0].from == '0')
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 08ec7f48f01d..b4a5058107c2 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -91,10 +91,12 @@ 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);
@@ -258,7 +260,7 @@ 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_send(chip, buf.data, tpm_buf_length(&buf));
 	if (rc > 0)
-- 
2.16.4


  parent reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-30 10:18 [PATCH v5 0/6] TPM 2.0 trusted keys with attached policy James Bottomley
2020-01-30 10:18 ` [PATCH v5 1/6] lib: add ASN.1 encoder James Bottomley
2020-01-30 10:18 ` [PATCH v5 2/6] oid_registry: Add TCG defined OIDS for TPM keys James Bottomley
2020-01-30 10:18 ` James Bottomley [this message]
2020-02-25 16:48   ` [PATCH v5 3/6] security: keys: trusted fix tpm2 authorizations Jarkko Sakkinen
2020-02-26 15:15     ` Jarkko Sakkinen
2020-02-27  0:58     ` James Bottomley
2020-02-27 16:19       ` Jarkko Sakkinen
2020-02-27 16:21         ` James Bottomley
2020-02-27 17:49           ` James Bottomley
2020-03-02 11:08             ` Jarkko Sakkinen
2020-01-30 10:18 ` [PATCH v5 4/6] security: keys: trusted: use ASN.1 TPM2 key format for the blobs James Bottomley
2020-02-03 16:54   ` James Prestwood
2020-02-27  0:02     ` James Bottomley
2020-02-27  0:20       ` James Prestwood
2020-02-27  0:54         ` James Bottomley
2020-02-27 17:19           ` James Prestwood
2020-02-27 20:19             ` James Bottomley
2020-02-27 20:26               ` James Bottomley
2020-02-27 20:44                 ` James Prestwood
2020-02-27 20:57               ` James Prestwood
2020-03-02 19:00               ` James Prestwood
2020-01-30 10:18 ` [PATCH v5 5/6] security: keys: trusted: add ability to specify arbitrary policy James Bottomley
2020-01-30 10:18 ` [PATCH v5 6/6] security: keys: trusted: implement counter/timer policy James Bottomley
2020-02-20 20:17 ` [PATCH v5 0/6] TPM 2.0 trusted keys with attached policy Jarkko Sakkinen

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