From 7ab551f9fd9a63586649a7df8790ddaeac55420f Mon Sep 17 00:00:00 2001 From: Vittorio Giovara Date: Wed, 30 Jul 2014 19:33:36 +0100 Subject: [PATCH] h264: prevent theoretical infinite loop in SEI parsing Properly address CVE-2011-3946 and parse bitstream as described in the spec. CC: libav-stable@libav.org Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind --- libavcodec/h264_sei.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/libavcodec/h264_sei.c b/libavcodec/h264_sei.c index 33230b7dfa..52ff2ff4bb 100644 --- a/libavcodec/h264_sei.c +++ b/libavcodec/h264_sei.c @@ -222,14 +222,20 @@ int ff_h264_decode_sei(H264Context *h) int size = 0; int type = 0; int ret = 0; + int last = 0; - do - type += show_bits(&h->gb, 8); - while (get_bits(&h->gb, 8) == 255); + while (get_bits_left(&h->gb) >= 8 && + (last = get_bits(&h->gb, 8)) == 255) { + type += 255; + } + type += last; - do - size += show_bits(&h->gb, 8); - while (get_bits(&h->gb, 8) == 255); + last = 0; + while (get_bits_left(&h->gb) >= 8 && + (last = get_bits(&h->gb, 8)) == 255) { + size += 255; + } + size += last; if (size > get_bits_left(&h->gb) / 8) { av_log(h->avctx, AV_LOG_ERROR, "SEI type %d truncated at %d\n",