Reduces the risk of finding false frames that happens to have valid values and CRC.
Fixes ticket #9185 ffmpeg flac decoder incorrectly finds junk frame https://trac.ffmpeg.org/ticket/9185 --- libavcodec/flac_parser.c | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/libavcodec/flac_parser.c b/libavcodec/flac_parser.c index d3d9c889a1..2c550507fc 100644 --- a/libavcodec/flac_parser.c +++ b/libavcodec/flac_parser.c @@ -96,8 +96,34 @@ static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf, FLACFrameInfo *fi) { GetBitContext gb; - init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8); - return !ff_flac_decode_frame_header(avctx, &gb, fi, 127); + uint8_t subframe_type; + + // header plus one byte from first subframe + init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8 + 8); + if (ff_flac_decode_frame_header(avctx, &gb, fi, 127)) { + return 0; + } + // subframe zero bit + if (get_bits1(&gb) != 0) { + return 0; + } + // subframe type + // 000000 : SUBFRAME_CONSTANT + // 000001 : SUBFRAME_VERBATIM + // 00001x : reserved + // 0001xx : reserved + // 001xxx : if(xxx <= 4) SUBFRAME_FIXED, xxx=order ; else reserved + // 01xxxx : reserved + // 1xxxxx : SUBFRAME_LPC, xxxxx=order-1 + subframe_type = get_bits(&gb, 6); + if (!(subframe_type == 0 || + subframe_type == 1 || + ((subframe_type >= 8) && (subframe_type <= 12)) || + (subframe_type >= 32))) { + return 0; + } + + return 1; } /** -- 2.29.2 _______________________________________________ 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".
