Fix fallback to external_creds interface

The code was incorrectly immediately erroring out if no credential file is
provided. Change the code to try to look for external credentials in
case of any error in the previous code block.

Signed-off-by: Simo Sorce <[email protected]>

Author: simo5

src/gss_creds.c

@@ -441,19 +441,22 @@ uint32_t gssntlm_acquire_cred_from(uint32_t *minor_status,
             char *filename;
 
             filename = get_user_file_envvar();
-            if (!filename) {
-                set_GSSERRS(ENOENT, GSS_S_CRED_UNAVAIL);
-                goto done;
+            if (filename) {
+                retmin = get_user_file_creds(filename, name, cred);
+                free(filename);
+            } else {
+                retmin = ENOENT;
             }
-            retmin = get_user_file_creds(filename, name, cred);
             if (retmin) {
-                retmin = external_get_creds(name, cred);
+                uint32_t ret;
+                ret = external_get_creds(name, cred);
+                if (ret != ERR_NOTAVAIL) {
+                    retmin = ret;
+                }
             }
-
-            free(filename);
         }
         if (retmin) {
-            set_GSSERR(retmin);
+            set_GSSERRS(retmin, GSS_S_CRED_UNAVAIL);
             goto done;
         }
     } else if (cred_usage == GSS_C_ACCEPT) {