[mod_redirect,mod-rewrite] short-circuit if blank replacement (fixes #2085)

x-ref:
  "null redirects for mod_redirect"
  https://redmine.lighttpd.net/issues/2085

NEWS

@@ -76,6 +76,7 @@ NEWS
   * [core] setrlimit max-fds <= rlim_max for non-root (fixes #2723)
   * [mod_ssi] config ssi.conditional-requests
   * [mod_ssi] config ssi.exec (fixes #2051)
+  * [mod_redirect,mod_rewrite] short-circuit if blank replacement (fixes #2085)
 
 - 1.4.39 - 2016-01-02
   * [core] fix memset_s call (fixes #2698)

src/mod_redirect.c

@@ -209,6 +209,10 @@ static handler_t mod_redirect_uri_handler(server *srv, connection *con, void *p_
 						"execution error while matching: ", n);
 				return HANDLER_ERROR;
 			}
+		} else if (0 == pattern_len) {
+			/* short-circuit if blank replacement pattern
+			 * (do not attempt to match against remaining redirect rules) */
+			return HANDLER_GO_ON;
 		} else {
 			const char **list;
 			size_t start;

src/mod_rewrite.c

@@ -383,6 +383,10 @@ static handler_t process_rewrite_rules(server *srv, connection *con, plugin_data
 						"execution error while matching: ", n);
 				return HANDLER_ERROR;
 			}
+		} else if (0 == pattern_len) {
+			/* short-circuit if blank replacement pattern
+			 * (do not attempt to match against remaining rewrite rules) */
+			return HANDLER_GO_ON;
 		} else {
 			const char **list;
 			size_t start;