Do not attempt to open references through absolute pathes.

This would allow an attacker to test remotely if a local file exists.

Originally committed as revision 21925 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mov.c

@@ -1556,11 +1556,8 @@ static void mov_build_index(MOVContext *mov, AVStream *st)
 
 static int mov_open_dref(ByteIOContext **pb, char *src, MOVDref *ref)
 {
-    /* try absolute path */
-    if (!url_fopen(pb, ref->path, URL_RDONLY))
-        return 0;
-
-    /* try relative path */
+    /* try relative path, we do not try the absolute because it can leak information about our
+       system to an attacker */
     if (ref->nlvl_to > 0 && ref->nlvl_from > 0) {
         char filename[1024];
         char *src_path;