From 996071489699923f85bb8dc0db9da726b4a16044 Mon Sep 17 00:00:00 2001
From: Mikael Nordfeldth <mmn@hethane.se>
Date: Wed, 3 Feb 2016 15:26:19 +0100
Subject: [PATCH] Disallow zero-length magnet URIs

magnet: would match, but now we have a zero-length lookahead which
requires the following character to be a question mark: magnet:?
---
 lib/util.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/util.php b/lib/util.php
index 6026105cb1..54296e1a4c 100644
--- a/lib/util.php
+++ b/lib/util.php
@@ -972,7 +972,7 @@ function common_replace_urls_callback($text, $callback, $arg = null) {
                 ')'.
             ')'.
             // URLs without domain name, like magnet:?xt=...
-            '|(?:(?:' . implode('|', common_url_schemes(_URL_SCHEME_NO_DOMAIN)) . '):)'.
+            '|(?:(?:' . implode('|', common_url_schemes(_URL_SCHEME_NO_DOMAIN)) . '):(?=\?))'.  // zero-length lookahead requires ? after :
             (common_config('linkify', 'bare_ipv4')   // Convert IPv4 addresses to hyperlinks
                 ? '|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'
                 : '').