* getkey.c (get_pubkey_fast): This one is sort of obscure. get_pubkey_fast

returns the primary key when requesting a subkey, so if a user has a key
signed by a subkey (we don't do this, but used to), AND that key is not
self-signed, AND the algorithm of the subkey in question is not present in
GnuPG, AND the algorithm of the primary key that owns the subkey in
question is present in GnuPG, then we will try and verify the subkey
signature using the primary key algorithm and hit a BUG().  The fix is to
not return a hit if the keyid is not the primary.  All other users of
get_pubkey_fast already expect a primary only.

g10/getkey.c

@@ -375,13 +375,15 @@ get_pubkey( PKT_public_key *pk, u32 *keyid )
 
 /* Get a public key and store it into the allocated pk.  This function
    differs from get_pubkey() in that it does not do a check of the key
-   to avoid recursion.  It should be used only in very certain cases.  */
+   to avoid recursion.  It should be used only in very certain cases.
+   It will only retrieve primary keys. */
 int
 get_pubkey_fast (PKT_public_key *pk, u32 *keyid)
 {
   int rc = 0;
   KEYDB_HANDLE hd;
   KBNODE keyblock;
+  u32 pkid[2];
   
   assert (pk);
 #if MAX_PK_CACHE_ENTRIES
@@ -414,20 +416,25 @@ get_pubkey_fast (PKT_public_key *pk, u32 *keyid)
       log_error ("keydb_get_keyblock failed: %s\n", g10_errstr(rc));
       return G10ERR_NO_PUBKEY;
     }
-  
+
   assert ( keyblock->pkt->pkttype == PKT_PUBLIC_KEY
            ||  keyblock->pkt->pkttype == PKT_PUBLIC_SUBKEY );
-  copy_public_key (pk, keyblock->pkt->pkt.public_key );
+
+  keyid_from_pk(keyblock->pkt->pkt.public_key,pkid);
+  if(keyid[0]==pkid[0] && keyid[1]==pkid[1])
+    copy_public_key (pk, keyblock->pkt->pkt.public_key );
+  else
+    rc=G10ERR_NO_PUBKEY;
+
   release_kbnode (keyblock);
 
   /* Not caching key here since it won't have all of the fields
      properly set. */
 
-  return 0;
+  return rc;
 }
 
 
-
 KBNODE
 get_pubkeyblock( u32 *keyid )
 {