Don't call AuthenticodeVerify if vendor_cert_size is 0.

Actually check the size of our vendor cert quite early, so that there's
no confusion as to what's going on.

This isn't strictly necessary, in that in all cases if vendor_cert_size
is 0, then AuthenticodeVerify -> Pkcs7Verify() -> d2i_X509() will result
in a NULL "Cert", and it will return FALSE, and we'll reject the
signature, but better to avoid all that code in the first place.  Belt
and suspenders and whatnot.

Based on a patch from https://github.com/TBOpen .

Signed-off-by: Peter Jones <pjones@redhat.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/shim.c b/shim.c
index cfa90d10..caa05d89 100644
--- a/shim.c
+++ b/shim.c
@@ -923,14 +923,13 @@ static EFI_STATUS verify_buffer (char *data, int datasize,
 			return status;
 		}
 
-
 		/*
 		 * And finally, check against shim's built-in key
 		 */
-		if (AuthenticodeVerify(cert->CertData,
-			       context->SecDir->Size - sizeof(cert->Hdr),
-			       vendor_cert, vendor_cert_size, sha256hash,
-			       SHA256_DIGEST_SIZE)) {
+		if (vendor_cert_size && AuthenticodeVerify(cert->CertData,
+							context->SecDir->Size - sizeof(cert->Hdr),
+							vendor_cert, vendor_cert_size, sha256hash,
+							SHA256_DIGEST_SIZE)) {
 			status = EFI_SUCCESS;
 			return status;
 		}