[v9,3/8] security: keys: trusted: fix TPM2 authorizations
diff mbox series

Message ID 20200507231147.27025-4-James.Bottomley@HansenPartnership.com
State New
Headers show
Series
  • TPM 2.0 trusted keys with attached policy
Related show

Commit Message

James Bottomley May 7, 2020, 11:11 p.m. UTC
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.

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.sakkinen@linux.intel.com>

---

v6: change comment, eliminate else clauses and add fixes tag
v7: fixes before signoff
---
 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

Jarkko Sakkinen May 14, 2020, 1:11 a.m. UTC | #1
On Thu, 2020-05-07 at 16:11 -0700, James Bottomley wrote:
> 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.
> 
> 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.sakkinen@linux.intel.com>

Have not checked yet the tail. Probably won't check before PR for v5.8
is out.

Just wondering would it hurt to merge everything up until this patch?


/Jarkko
Jarkko Sakkinen May 14, 2020, 1:12 a.m. UTC | #2
On Thu, 2020-05-14 at 04:11 +0300, Jarkko Sakkinen wrote:
> On Thu, 2020-05-07 at 16:11 -0700, James Bottomley wrote:
> > 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.
> > 
> > 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.sakkinen@linux.intel.com>
> 
> Have not checked yet the tail. Probably won't check before PR for v5.8
> is out.
> 
> Just wondering would it hurt to merge everything up until this patch?

I.e. could land it also to the release.

/Jarkko
James Bottomley May 14, 2020, 1:41 a.m. UTC | #3
On Thu, 2020-05-14 at 04:12 +0300, Jarkko Sakkinen wrote:
> On Thu, 2020-05-14 at 04:11 +0300, Jarkko Sakkinen wrote:
> > On Thu, 2020-05-07 at 16:11 -0700, James Bottomley wrote:
> > > 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.
> > > 
> > > 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.sakkinen@linux.intel.com>
> > 
> > Have not checked yet the tail. Probably won't check before PR for
> > v5.8 is out.
> > 
> > Just wondering would it hurt to merge everything up until this
> > patch?

Everything would be OK if you applied 1, 2 and 3.  Except we'd have an
ASN.1 API in the tree with no consumers, which excites some people.

> I.e. could land it also to the release.

That would likely be fine and should satisfy the API with no consumers
issue.

James
Jarkko Sakkinen May 14, 2020, 11:19 a.m. UTC | #4
On Wed, 2020-05-13 at 18:41 -0700, James Bottomley wrote:
> On Thu, 2020-05-14 at 04:12 +0300, Jarkko Sakkinen wrote:
> > On Thu, 2020-05-14 at 04:11 +0300, Jarkko Sakkinen wrote:
> > > On Thu, 2020-05-07 at 16:11 -0700, James Bottomley wrote:
> > > > 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.
> > > > 
> > > > 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.sakkinen@linux.intel.com>
> > > 
> > > Have not checked yet the tail. Probably won't check before PR for
> > > v5.8 is out.
> > > 
> > > Just wondering would it hurt to merge everything up until this
> > > patch?
> 
> Everything would be OK if you applied 1, 2 and 3.  Except we'd have an
> ASN.1 API in the tree with no consumers, which excites some people.
> 
> > I.e. could land it also to the release.
> 
> That would likely be fine and should satisfy the API with no consumers
> issue.

Hmm. Right, it does not sense to merge unused API.

I'd like to still pick this patch (3/8) but you need to fix these first:

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#17: 
keyctl add trusted kmk "new 32 blobauth=f572d396fae9206628714fb2ce00f72e94f2258f"

WARNING: line over 80 characters
#89: FILE: security/keys/trusted-keys/trusted_tpm1.c:801:
+			if (tpm2 && opt->blobauth_len <= sizeof(opt->blobauth)) {

WARNING: line over 80 characters
#111: FILE: security/keys/trusted-keys/trusted_tpm2.c:94:
+	tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len + 1);

The best way is probably to encapsulate into helper function. It is more or
less a sign that the code is too complicated to live inside a switch-case
statement.

Can you do that and send it as a separate patch?

/Jarkko

Patch
diff mbox series

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 8001ab07e63b..3b8fa7df0d27 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -781,13 +781,33 @@  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;
+				return 0;
+			}
+
+			if (tpm2 && opt->blobauth_len <= sizeof(opt->blobauth)) {
+				memcpy(opt->blobauth, args[0].from,
+				       opt->blobauth_len);
+				return 0;
+			}
+
+			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 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)