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https://github.com/nyanmisaka/ffmpeg-rockchip.git
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a4405cc0cc
The DVD subtitle parser handles two types of packets: "normal" packets with a 16-bit length, and HD-DVD packets that set the 16-bit length to 0 and encode a 32-bit length in the next four bytes. This implies that HD-DVD packets are at least six bytes long, but the code didn't actually verify this. The faulty length check results in an out of bounds read for zero-length "normal" packets that occur in the input, which are only 2 bytes long, but get misinterpreted as an HD-DVD packet. When this happens the parser reads packet_len from beyond the end of the input buffer. The subtitle stream is not correctly decoded after this point due to the garbage packet_len. Fixing this is pretty simple: fix the length check so packets less than 6 bytes long will not be mistakenly parsed as HD-DVD packets. Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com> Signed-off-by: Anton Khirnov <anton@khirnov.net>
93 lines
3.0 KiB
C
93 lines
3.0 KiB
C
/*
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* DVD subtitle decoding
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* Copyright (c) 2005 Fabrice Bellard
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <string.h>
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#include "libavutil/intreadwrite.h"
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#include "libavutil/mem.h"
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#include "avcodec.h"
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/* parser definition */
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typedef struct DVDSubParseContext {
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uint8_t *packet;
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int packet_len;
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int packet_index;
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} DVDSubParseContext;
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static int dvdsub_parse(AVCodecParserContext *s,
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AVCodecContext *avctx,
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const uint8_t **poutbuf, int *poutbuf_size,
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const uint8_t *buf, int buf_size)
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{
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DVDSubParseContext *pc = s->priv_data;
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*poutbuf = buf;
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*poutbuf_size = buf_size;
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if (pc->packet_index == 0) {
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if (buf_size < 2 || (AV_RB16(buf) == 0 && buf_size < 6)) {
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if (buf_size)
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av_log(avctx, AV_LOG_DEBUG, "Parser input %d too small\n", buf_size);
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return buf_size;
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}
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pc->packet_len = AV_RB16(buf);
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if (pc->packet_len == 0) /* HD-DVD subpicture packet */
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pc->packet_len = AV_RB32(buf+2);
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av_freep(&pc->packet);
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if ((unsigned)pc->packet_len > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE) {
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av_log(avctx, AV_LOG_ERROR, "packet length %d is invalid\n", pc->packet_len);
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return buf_size;
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}
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pc->packet = av_malloc(pc->packet_len + AV_INPUT_BUFFER_PADDING_SIZE);
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}
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if (pc->packet) {
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if (pc->packet_index + buf_size <= pc->packet_len) {
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memcpy(pc->packet + pc->packet_index, buf, buf_size);
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pc->packet_index += buf_size;
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if (pc->packet_index >= pc->packet_len) {
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*poutbuf = pc->packet;
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*poutbuf_size = pc->packet_len;
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pc->packet_index = 0;
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return buf_size;
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}
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} else {
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/* erroneous size */
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pc->packet_index = 0;
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}
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}
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*poutbuf = NULL;
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*poutbuf_size = 0;
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return buf_size;
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}
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static av_cold void dvdsub_parse_close(AVCodecParserContext *s)
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{
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DVDSubParseContext *pc = s->priv_data;
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av_freep(&pc->packet);
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}
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const AVCodecParser ff_dvdsub_parser = {
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.codec_ids = { AV_CODEC_ID_DVD_SUBTITLE },
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.priv_data_size = sizeof(DVDSubParseContext),
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.parser_parse = dvdsub_parse,
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.parser_close = dvdsub_parse_close,
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};
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