X.509: Handle certificates that lack an authorityKeyIdentifier field

Handle certificates that lack an authorityKeyIdentifier field by assuming
they're self-signed and checking their signatures against themselves.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Josh Boyer <jwboyer@redhat.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index eb368d4c632c..0f55e3b027a0 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -143,8 +143,8 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
                  pkey_algo_name[cert->sig.pkey_algo],
                  pkey_hash_algo_name[cert->sig.pkey_hash_algo]);
 
-        if (!cert->fingerprint || !cert->authority) {
-                pr_warn("Cert for '%s' must have SubjKeyId and AuthKeyId extensions\n",
+        if (!cert->fingerprint) {
+                pr_warn("Cert for '%s' must have a SubjKeyId extension\n",
                         cert->subject);
                 ret = -EKEYREJECTED;
                 goto error_free_cert;
@@ -190,8 +190,9 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
         cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
         cert->pub->id_type = PKEY_ID_X509;
 
-        /* Check the signature on the key */
-        if (strcmp(cert->fingerprint, cert->authority) == 0) {
+        /* Check the signature on the key if it appears to be self-signed */
+        if (!cert->authority ||
+            strcmp(cert->fingerprint, cert->authority) == 0) {
                 ret = x509_check_signature(cert->pub, cert);
                 if (ret < 0)
                         goto error_free_cert;