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

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commit 4b34968e77 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: a511e1af8b ("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>
This commit is contained in:
Eric Biggers
2018-02-26 10:17:15 -08:00
committed by Greg Kroah-Hartman
parent febf108e6c
commit f2915986f8
1 changed files with 5 additions and 2 deletions
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7
crypto/asymmetric_keys/restrict.c
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@@ -66,8 +66,9 @@ __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 *trust_keyring,
const struct key_type *type,
@@ -86,6 +87,8 @@ int restrict_link_by_signature(struct key *trust_keyring,
return -EOPNOTSUPP;
sig = payload->data[asym_auth];
if (!sig)
return -ENOPKG;
if (!sig->auth_ids[0] && !sig->auth_ids[1])
return -ENOKEY;