rm: prevent infinite loops for index parsing.
authorRonald S. Bultje <rsbultje@gmail.com>
Wed, 22 Feb 2012 19:33:24 +0000 (11:33 -0800)
committerRonald S. Bultje <rsbultje@gmail.com>
Wed, 22 Feb 2012 20:00:23 +0000 (12:00 -0800)
Specifically, prevent jumping back in the file for the next index, since
this can lead to infinite loops where we jump between indexes referring
to each other, and don't read indexes that don't fit in the file.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
libavformat/rmdec.c

index ed16b07..6775294 100644 (file)
@@ -370,8 +370,19 @@ static int rm_read_index(AVFormatContext *s)
                 st = s->streams[n];
                 break;
             }
-        if (n == s->nb_streams)
+        if (n == s->nb_streams) {
+            av_log(s, AV_LOG_ERROR,
+                   "Invalid stream index %d for index at pos %"PRId64"\n",
+                   str_id, avio_tell(pb));
             goto skip;
+        } else if ((avio_size(pb) - avio_tell(pb)) / 14 < n_pkts) {
+            av_log(s, AV_LOG_ERROR,
+                   "Nr. of packets in packet index for stream index %d "
+                   "exceeds filesize (%"PRId64" at %"PRId64" = %d)\n",
+                   str_id, avio_size(pb), avio_tell(pb),
+                   (avio_size(pb) - avio_tell(pb)) / 14);
+            goto skip;
+        }
 
         for (n = 0; n < n_pkts; n++) {
             avio_skip(pb, 2);
@@ -383,9 +394,12 @@ static int rm_read_index(AVFormatContext *s)
         }
 
 skip:
-        if (next_off && avio_tell(pb) != next_off &&
-            avio_seek(pb, next_off, SEEK_SET) < 0)
+        if (next_off && avio_tell(pb) < next_off &&
+            avio_seek(pb, next_off, SEEK_SET) < 0) {
+            av_log(s, AV_LOG_ERROR,
+                   "Non-linear index detected, not supported\n");
             return -1;
+        }
     } while (next_off);
 
     return 0;