Patch "X.509: fix NULL dereference when restricting key with unsupported_sig" has been added to the 4.15-stable tree

Patch "X.509: fix NULL dereference when restricting key with unsupported_sig" has been added to the 4.15-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    X.509: fix NULL dereference when restricting key with unsupported_sig

to the 4.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x.509-fix-null-dereference-when-restricting-key-with-unsupported_sig.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 4b34968e77ad09628cfb3c4a7daf2adc2cefc6e8 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Thu, 22 Feb 2018 14:38:34 +0000
Subject: X.509: fix NULL dereference when restricting key with unsupported_sig

From: Eric Biggers <ebiggers@google.com>

commit 4b34968e77ad09628cfb3c4a7daf2adc2cefc6e8 upstream.

The asymmetric key type allows an X.509 certificate to be added even if
its signature's hash algorithm is not available in the crypto API.  In
that case 'payload.data[asym_auth]' will be NULL.  But the key
restriction code failed to check for this case before trying to use the
signature, resulting in a NULL pointer dereference in
key_or_keyring_common() or in restrict_link_by_signature().

Fix this by returning -ENOPKG when the signature is unsupported.

Reproducer when all the CONFIG_CRYPTO_SHA512* options are disabled and
keyctl has support for the 'restrict_keyring' command:

    keyctl new_session
    keyctl restrict_keyring @s asymmetric builtin_trusted
    openssl req -new -sha512 -x509 -batch -nodes -outform der \
        | keyctl padd asymmetric desc @s

Fixes: a511e1af8b12 ("KEYS: Move the point of trust determination to __key_link()")
Cc: <stable@vger.kernel.org> # v4.7+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 crypto/asymmetric_keys/restrict.c |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

--- a/crypto/asymmetric_keys/restrict.c
+++ b/crypto/asymmetric_keys/restrict.c
@@ -67,8 +67,9 @@ __setup("ca_keys=", ca_keys_setup);
  *
  * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
  * matching parent certificate in the trusted list, -EKEYREJECTED if the
- * signature check fails or the key is blacklisted and some other error if
- * there is a matching certificate but the signature check cannot be performed.
+ * signature check fails or the key is blacklisted, -ENOPKG if the signature
+ * uses unsupported crypto, or some other error if there is a matching
+ * certificate but the signature check cannot be performed.
  */
 int restrict_link_by_signature(struct key *dest_keyring,
 			       const struct key_type *type,
@@ -88,6 +89,8 @@ int restrict_link_by_signature(struct ke
 		return -EOPNOTSUPP;
 
 	sig = payload->data[asym_auth];
+	if (!sig)
+		return -ENOPKG;
 	if (!sig->auth_ids[0] && !sig->auth_ids[1])
 		return -ENOKEY;
 
@@ -139,6 +142,8 @@ static int key_or_keyring_common(struct
 		return -EOPNOTSUPP;
 
 	sig = payload->data[asym_auth];
+	if (!sig)
+		return -ENOPKG;
 	if (!sig->auth_ids[0] && !sig->auth_ids[1])
 		return -ENOKEY;
 
@@ -222,9 +227,9 @@ static int key_or_keyring_common(struct
  *
  * Returns 0 if the new certificate was accepted, -ENOKEY if we
  * couldn't find a matching parent certificate in the trusted list,
- * -EKEYREJECTED if the signature check fails, and some other error if
- * there is a matching certificate but the signature check cannot be
- * performed.
+ * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
+ * unsupported crypto, or some other error if there is a matching certificate
+ * but the signature check cannot be performed.
  */
 int restrict_link_by_key_or_keyring(struct key *dest_keyring,
 				    const struct key_type *type,
@@ -249,9 +254,9 @@ int restrict_link_by_key_or_keyring(stru
  *
  * Returns 0 if the new certificate was accepted, -ENOKEY if we
  * couldn't find a matching parent certificate in the trusted list,
- * -EKEYREJECTED if the signature check fails, and some other error if
- * there is a matching certificate but the signature check cannot be
- * performed.
+ * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
+ * unsupported crypto, or some other error if there is a matching certificate
+ * but the signature check cannot be performed.
  */
 int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
 					  const struct key_type *type,


Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.15/pkcs-7-fix-certificate-blacklisting.patch
queue-4.15/x.509-fix-null-dereference-when-restricting-key-with-unsupported_sig.patch
queue-4.15/x.509-fix-bug_on-when-hash-algorithm-is-unsupported.patch
queue-4.15/pkcs-7-fix-certificate-chain-verification.patch