sm: Fix issuer certificate look error due to legacy error code.

* sm/certchain.c (find_up): Get rid of the legacy return code -1 and
chnage var name rc to err.
(gpgsm_walk_cert_chain): Change var name rc to err.
(do_validate_chain): Get rid of the legacy return code -1.

* sm/keydb.c (keydb_search): Replace return code -1 by
GPG_ERR_NOT_FOUND.
(keydb_set_cert_flags): Replace return code -1 by GPG_ERR_NOT_FOUND.
* sm/certchain.c (find_up_search_by_keyid): Ditto.
(find_up_external, find_up, find_up_dirmngr): Ditto.
(gpgsm_walk_cert_chain): Ditto.
(get_regtp_ca_info): Ditto.
* sm/certlist.c (gpgsm_add_to_certlist): Ditto.
(gpgsm_find_cert): Ditto.
* sm/delete.c (delete_one): Ditto.
* sm/export.c (gpgsm_export): Ditto.
(gpgsm_p12_export): Ditto.
* sm/import.c (gpgsm_import_files): Ditto.
* sm/keylist.c (list_cert_colon): Ditto.
(list_internal_keys): Ditto.
* sm/sign.c (add_certificate_list): Ditto.

--

This bug was detected while fixing
GnuPG-bug-id: 4757
Backported-from-master: 473b83d1b9

Some extra code has been taken from
commit ed6ebb696e

sm/keylist.c

@@ -433,8 +433,9 @@ list_cert_colon (ctrl_t ctrl, ksba_cert_t cert, unsigned int validity,
         chain_id = chain_id_buffer;
         ksba_cert_release (next);
       }
-    else if (rc == -1)  /* We have reached the root certificate. */
+    else if (gpg_err_code (rc) == GPG_ERR_NOT_FOUND)
       {
+        /* We have reached the root certificate. */
         chain_id = fpr;
         is_root = 1;
       }
@@ -1587,7 +1588,7 @@ list_internal_keys (ctrl_t ctrl, strlist_t names, estream_t fp,
       lastcert = cert;
       cert = NULL;
     }
-  if (gpg_err_code (rc) == GPG_ERR_EOF || rc == -1 )
+  if (gpg_err_code (rc) == GPG_ERR_NOT_FOUND)
     rc = 0;
   if (rc)
     log_error ("keydb_search failed: %s\n", gpg_strerror (rc));