rm: prevent infinite loops for index parsing.

Message ID 20120222200247.34CFA5E005@aruru.libav.org
State New
Headers show

Commit Message

Janne Grunau Feb. 22, 2012, 8:02 p.m.
Module: libav
Branch: master
Commit: aac07a7a4c2c7a4a29cf6dbc88c1b9fdd191b99d

Author:    Ronald S. Bultje <rsbultje@gmail.com>
Committer: Ronald S. Bultje <rsbultje@gmail.com>
Date:      Wed Feb 22 11:33:24 2012 -0800

rm: prevent infinite loops for index parsing.

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 |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

Patch

diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index ed16b07..6775294 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -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;