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 Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> --- libavcodec/tiff.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c index c520d7df83..1f1a1a3698 100644 --- a/libavcodec/tiff.c +++ b/libavcodec/tiff.c @@ -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; -- 2.22.0 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
