Propagate null gstring through string_catn()

[exim.git] / src / src / arc.c

diff --git a/src/src/arc.c b/src/src/arc.c
index c1407af60258d8cf971f0f187c355786230e3599..e0ee19950cf451ee2882654843c3adb14965a8dc 100644 (file)
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -3,6 +3,7 @@
 *************************************************/
 /* Experimental ARC support for Exim
    Copyright (c) Jeremy Harris 2018 - 2020
+   Copyright (c) The Exim Maintainers 2021
    License: GPL
 */
 
@@ -1607,20 +1608,18 @@ expire = now = 0;
 
 /* Parse the signing specification */
 
-if (  !(identity = string_nextinlist(&signspec, &sep, NULL, 0)) || !*identity
-   || !(selector = string_nextinlist(&signspec, &sep, NULL, 0)) || !*selector
-   || !(privkey = string_nextinlist(&signspec, &sep, NULL, 0))  || !*privkey
-   )
-  {
-  s = !*identity ? US"identity" : !*selector ? US"selector" : US"private-key";
-  goto bad_arg_ret;
-  }
+if (!(identity = string_nextinlist(&signspec, &sep, NULL, 0)) || !*identity)
+  { s = US"identity"; goto bad_arg_ret; }
+if (!(selector = string_nextinlist(&signspec, &sep, NULL, 0)) || !*selector)
+  { s = US"selector"; goto bad_arg_ret; }
+if (!(privkey = string_nextinlist(&signspec, &sep, NULL, 0))  || !*privkey)
+  { s = US"privkey"; goto bad_arg_ret; }
 if (!arc_valid_id(identity))
   { s = US"identity"; goto bad_arg_ret; }
 if (!arc_valid_id(selector))
   { s = US"selector"; goto bad_arg_ret; }
 if (*privkey == '/' && !(privkey = expand_file_big_buffer(privkey)))
-  return sigheaders ? sigheaders : string_get(0);
+  goto ret_sigheaders;
 
 if ((opts = string_nextinlist(&signspec, &sep, NULL, 0)))
   {
@@ -1679,7 +1678,7 @@ if ((rheaders = arc_sign_scan_headers(&arc_sign_ctx, sigheaders)))
 if (!(arc_sign_find_ar(headers, identity, &ar)))
   {
   log_write(0, LOG_MAIN, "ARC: no Authentication-Results header for signing");
-  return sigheaders ? sigheaders : string_get(0);
+  goto ret_sigheaders;
   }
 
 /* We previously built the data-struct for the existing ARC chain, if any, using a headers
@@ -1735,14 +1734,19 @@ if (g)
 /* Finally, append the dkim headers and return the lot. */
 
 if (sigheaders) g = string_catn(g, sigheaders->s, sigheaders->ptr);
-(void) string_from_gstring(g);
-gstring_release_unused(g);
-return g;
+
+out:
+  if (!g) return string_get(1);
+  (void) string_from_gstring(g);
+  gstring_release_unused(g);
+  return g;
 
 
 bad_arg_ret:
   log_write(0, LOG_MAIN, "ARC: bad signing-specification (%s)", s);
-  return sigheaders ? sigheaders : string_get(0);
+ret_sigheaders:
+  g = sigheaders;
+  goto out;
 }