Bug#895228: mutt: "ambiguous specification of secret key" when trying to sign a message

[Julian Gilbey]

On Sun, Apr 08, 2018 at 03:56:19PM +0100, Julian Gilbey wrote:
> [...]
> 
> Since my GPG key is in the Debian keyring, I observe the following:
> 
> erdos:~ $ gpg --list-options show-keyring --list-secret-keys 
> 0x59D03CC92BA0FEAE
> Keyring: /home/jdg/.gnupg/pubring.gpg
> -------------------------------------
> sec#  rsa4096/0x59D03CC92BA0FEAE 2014-10-29 [SC] [expires: 2018-08-23]
>       Key fingerprint = 725E 9D6E E56F CAD6 C339  A7F2 59D0 3CC9 2BA0 FEAE
> [...]
> 
> Keyring: /usr/share/keyrings/debian-keyring.gpg
> -----------------------------------------------
> sec#  rsa4096/0x59D03CC92BA0FEAE 2014-10-29 [SC] [expires: 2018-08-23]
>       Key fingerprint = 725E 9D6E E56F CAD6 C339  A7F2 59D0 3CC9 2BA0 FEAE
> [...]
> 
> and the same key is reported twice, as the public key is found on two
> separate keyrings.
> 
> In the past, mutt had no problem with this, but now, mutt is
> complaining with the message:
> 
> ambiguous specification of secret key 
> `0x725E9D6EE56FCAD6C339A7F259D03CC92BA0FEAE'?
> [...]

Hello!

I've located and fixed the source of this bug; a patch is attached.
I've also submitted it upstream as
https://gitlab.com/muttmua/mutt/merge_requests/43

Best wishes,

   Julian

--- a/crypt-gpgme.c
+++ b/crypt-gpgme.c
@@ -707,6 +707,7 @@
   gpgme_error_t err;
   gpgme_ctx_t listctx;
   gpgme_key_t key, key2;
+  char *fpr, *fpr2;
 
   if (for_smime)
     signid = (SmimeSignAs && *SmimeSignAs) ? SmimeSignAs : SmimeDefaultKey;
@@ -727,15 +728,21 @@
                   signid, gpgme_strerror (err));
       return -1;
     }
-  err = gpgme_op_keylist_next (listctx, &key2);
-  if (!err)
+  fpr = key->subkeys->fpr;
+  while (! gpgme_op_keylist_next (listctx, &key2))
     {
-      gpgme_key_unref (key);
-      gpgme_key_unref (key2);
-      gpgme_release (listctx);
-      mutt_error (_("ambiguous specification of secret key `%s'\n"),
-                  signid);
-      return -1;
+      fpr2 = key2->subkeys->fpr;
+      if (strcmp(fpr, fpr2))
+        {
+          gpgme_key_unref (key);
+          gpgme_key_unref (key2);
+          gpgme_release (listctx);
+          mutt_error (_("ambiguous specification of secret key `%s'\n"),
+                      signid);
+          return -1;
+        } else {
+          gpgme_key_unref (key2);
+        }
     }
   gpgme_op_keylist_end (listctx);
   gpgme_release (listctx);