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avcodec/tiff: Enforce increasing offsets 

This may break some valid tiff files, it appears the specification does not require
the offsets to be increasing. They increase in the 2 test files i have though except
the last offset which is 0 (an end marker) and for which a special case is added to
avoid asking for a sample for that end marker.

See: [FFmpeg-devel] [PATCH 2/2] avcodec/tiff: Detect infinite retry loop
for an alternative implementation

Fixes: Timeout (Infinite -> Finite)
Fixes: 15706/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-5114674904825856

This variant was requested by paul on IRC
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2019-08-09 01:23:46 +02:00
parent 9cd1e939cf
commit 1fedba3c35
1 changed files with 10 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
libavcodec/tiff.c
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@ -1399,7 +1399,7 @@ static int decode_frame(AVCodecContext *avctx,
TiffContext *const s = avctx->priv_data;
AVFrame *const p = data;
ThreadFrame frame = { .f = data };
unsigned off;
unsigned off, last_off;
int le, ret, plane, planes;
int i, j, entries, stride;
unsigned soff, ssize;
@ -1454,6 +1454,7 @@ again:
/** whether we should process this multi-page IFD's next page */
retry_for_page = s->get_page && s->cur_page + 1 < s->get_page; // get_page is 1-indexed
last_off = off;
if (retry_for_page) {
// set offset to the next IFD
off = ff_tget_long(&s->gb, le);
@ -1463,6 +1464,14 @@ again:
}
if (retry_for_subifd || retry_for_page) {
if (!off) {
av_log(avctx, AV_LOG_ERROR, "Requested entry not found\n");
return AVERROR_INVALIDDATA;
}
if (off <= last_off) {
avpriv_request_sample(s->avctx, "non increasing IFD offset\n");
return AVERROR_INVALIDDATA;
}
if (off >= UINT_MAX - 14 || avpkt->size < off + 14) {
av_log(avctx, AV_LOG_ERROR, "IFD offset is greater than image size\n");
return AVERROR_INVALIDDATA;