[PATCH 2/6] PKCS#7: fix certificate blacklisting

[David Howells]

From: Eric Biggers <ebigg...@google.com>

If there is a blacklisted certificate in a SignerInfo's certificate
chain, then pkcs7_verify_sig_chain() sets sinfo->blacklisted and returns
0.  But, pkcs7_verify() fails to handle this case appropriately, as it
actually continues on to the line 'actual_ret = 0;', indicating that the
SignerInfo has passed verification.  Consequently, PKCS#7 signature
verification ignores the certificate blacklist.

Fix this by not considering blacklisted SignerInfos to have passed
verification.

Also fix the function comment with regards to when 0 is returned.

Fixes: 03bb79315ddc ("PKCS#7: Handle blacklisted certificates")
Cc: <sta...@vger.kernel.org> # v4.12+
Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: David Howells <dhowe...@redhat.com>
---

 crypto/asymmetric_keys/pkcs7_verify.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/crypto/asymmetric_keys/pkcs7_verify.c 
b/crypto/asymmetric_keys/pkcs7_verify.c
index 2f6a768b91d7..97c77f66b20d 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -366,8 +366,7 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
  *
  *  (*) -EBADMSG if some part of the message was invalid, or:
  *
- *  (*) 0 if no signature chains were found to be blacklisted or to contain
- *     unsupported crypto, or:
+ *  (*) 0 if a signature chain passed verification, or:
  *
  *  (*) -EKEYREJECTED if a blacklisted key was encountered, or:
  *
@@ -423,8 +422,11 @@ int pkcs7_verify(struct pkcs7_message *pkcs7,
 
        for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
                ret = pkcs7_verify_one(pkcs7, sinfo);
-               if (sinfo->blacklisted && actual_ret == -ENOPKG)
-                       actual_ret = -EKEYREJECTED;
+               if (sinfo->blacklisted) {
+                       if (actual_ret == -ENOPKG)
+                               actual_ret = -EKEYREJECTED;
+                       continue;
+               }
                if (ret < 0) {
                        if (ret == -ENOPKG) {
                                sinfo->unsupported_crypto = true;