[FFmpeg-devel] [PATCH] avformat/mov: validate chunk_count vs stsc_data

[chcunningham]

Bad content may contain stsc boxes with a first_chunk index that
exceeds stco.entries (chunk_count). This ammends the existing check to
include cases where chunk_count == 0.
---
 libavformat/mov.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 9b9739f788..2f3ad38ac3 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2694,8 +2694,11 @@ static inline int64_t mov_get_stsc_samples(MOVStreamContext *sc, unsigned int in
 
     if (mov_stsc_index_valid(index, sc->stsc_count))
         chunk_count = sc->stsc_data[index + 1].first - sc->stsc_data[index].first;
-    else
+    else {
+        // Validation for stsc / stco  happens earlier in mov_read_stsc + mov_read_trak.
+        av_assert0(sc->stsc_data[index].first <= sc->chunk_count);
         chunk_count = sc->chunk_count - (sc->stsc_data[index].first - 1);
+    }
 
     return sc->stsc_data[index].count * (int64_t)chunk_count;
 }
@@ -4175,7 +4178,7 @@ static int mov_read_trak(MOVContext *c, AVIOContext *pb, MOVAtom atom)
                st->index);
         return 0;
     }
-    if (sc->chunk_count && sc->stsc_count && sc->stsc_data[ sc->stsc_count - 1 ].first > sc->chunk_count) {
+    if (sc->stsc_count && sc->stsc_data[ sc->stsc_count - 1 ].first > sc->chunk_count) {
         av_log(c->fc, AV_LOG_ERROR, "stream %d, contradictionary STSC and STCO\n",
                st->index);
         return AVERROR_INVALIDDATA;
-- 
2.20.1.611.gfbb209baf1-goog