gpg: Fix extra check for sign usage of a data signature.

* g10/sig-check.c (check_signature_end_simple):
--

Obviously we should not ignore a back signature here.

Fixes-commit: 214b0077264e35c079e854a8b6374704aea45cd5
GnuPG-bug-id: 4014
Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit b6275f3bda8edff34274c5b921508567f491ab9c)

Gbp-Pq: Name gpg-Fix-extra-check-for-sign-usage-of-a-data-signature.patch

diff --git a/g10/sig-check.c b/g10/sig-check.c
index e59e0c90068190c0119e51686920cfe73dedd7b7..a93b496a8855045a62f48b39224d6a4b57370da1 100644 (file)
--- a/g10/sig-check.c
+++ b/g10/sig-check.c
@@ -481,7 +481,8 @@ check_signature_end_simple (PKT_public_key *pk, PKT_signature *sig,
     }
 
   /* For data signatures check that the key has sign usage.  */
-  if (IS_SIG (sig) && !(pk->pubkey_usage & PUBKEY_USAGE_SIG))
+  if (!IS_BACK_SIG (sig) && IS_SIG (sig)
+      && !(pk->pubkey_usage & PUBKEY_USAGE_SIG))
     {
       rc = gpg_error (GPG_ERR_WRONG_KEY_USAGE);
       if (!opt.quiet)