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/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/* Targeted fuzzer that targets specific codecs depending on two
compile-time flags.
INSTRUCTIONS:
* Get the very fresh clang, e.g. see http://libfuzzer.info#versions
* Get and build libFuzzer:
svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer
./Fuzzer/build.sh
* build ffmpeg for fuzzing:
FLAGS="-fsanitize=address -fsanitize-coverage=trace-pc-guard,trace-cmp -g" CC="clang $FLAGS" CXX="clang++ $FLAGS" ./configure --disable-yasm
make clean && make -j
* build the fuzz target.
Choose the value of FFMPEG_CODEC (e.g. AV_CODEC_ID_DVD_SUBTITLE) and
choose one of FUZZ_FFMPEG_VIDEO, FUZZ_FFMPEG_AUDIO, FUZZ_FFMPEG_SUBTITLE.
clang -fsanitize=address -fsanitize-coverage=trace-pc-guard,trace-cmp doc/examples/decoder_targeted.c -o decoder_targeted -I. -DFFMPEG_CODEC=AV_CODEC_ID_MPEG1VIDEO -DFUZZ_FFMPEG_VIDEO ../../libfuzzer/libFuzzer.a -Llibavcodec -Llibavdevice -Llibavfilter -Llibavformat -Llibavresample -Llibavutil -Llibpostproc -Llibswscale -Llibswresample -Wl,--as-needed -Wl,-z,noexecstack -Wl,--warn-common -Wl,-rpath-link=libpostproc:libswresample:libswscale:libavfilter:libavdevice:libavformat:libavcodec:libavutil:libavresample -lavdevice -lavfilter -lavformat -lavcodec -lswresample -lswscale -lavutil -ldl -lxcb -lxcb-shm -lxcb -lxcb-xfixes -lxcb -lxcb-shape -lxcb -lX11 -lasound -lm -lbz2 -lz -pthread
* create a corpus directory and put some samples there (empty dir is ok too):
mkdir CORPUS && cp some-files CORPUS
* Run fuzzing:
./decoder_targeted -max_len=100000 CORPUS
More info:
http://libfuzzer.info
http://tutorial.libfuzzer.info
https://github.com/google/oss-fuzz
http://lcamtuf.coredump.cx/afl/
https://security.googleblog.com/2016/08/guided-in-process-fuzzing-of-chrome.html
*/
#include "libavutil/avassert.h"
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
static void error(const char *err)
{
fprintf(stderr, "%s", err);
exit(1);
}
static AVCodec *c = NULL;
static AVCodec *AVCodecInitialize(enum AVCodecID codec_id)
{
AVCodec *res;
av_register_all();
av_log_set_level(AV_LOG_PANIC);
res = avcodec_find_decoder(codec_id);
if (!res)
error("Failed to find decoder");
return res;
}
#if defined(FUZZ_FFMPEG_VIDEO)
#define decode_handler avcodec_decode_video2
#elif defined(FUZZ_FFMPEG_AUDIO)
#define decode_handler avcodec_decode_audio4
#elif defined(FUZZ_FFMPEG_SUBTITLE)
static int subtitle_handler(AVCodecContext *avctx, void *frame,
int *got_sub_ptr, AVPacket *avpkt)
{
AVSubtitle sub;
int ret = avcodec_decode_subtitle2(avctx, &sub, got_sub_ptr, avpkt);
if (ret >= 0 && *got_sub_ptr)
avsubtitle_free(&sub);
return ret;
}
#define decode_handler subtitle_handler
#else
#error "Specify encoder type" // To catch mistakes
#endif
// Class to handle buffer allocation and resize for each frame
typedef struct FuzzDataBuffer {
size_t size_;
uint8_t *data_;
} FuzzDataBuffer;
void FDBCreate(FuzzDataBuffer *FDB) {
FDB->size_ = 0x1000;
FDB->data_ = av_malloc(FDB->size_);
if (!FDB->data_)
error("Failed memory allocation");
}
void FDBDesroy(FuzzDataBuffer *FDB) { av_free(FDB->data_); }
void FDBRealloc(FuzzDataBuffer *FDB, size_t size) {
size_t needed = size + FF_INPUT_BUFFER_PADDING_SIZE;
av_assert0(needed > size);
if (needed > FDB->size_) {
av_free(FDB->data_);
FDB->size_ = needed;
FDB->data_ = av_malloc(FDB->size_);
if (!FDB->data_)
error("Failed memory allocation");
}
}
void FDBPrepare(FuzzDataBuffer *FDB, AVPacket *dst, const uint8_t *data,
size_t size)
{
FDBRealloc(FDB, size);
memcpy(FDB->data_, data, size);
size_t padd = FDB->size_ - size;
if (padd > FF_INPUT_BUFFER_PADDING_SIZE)
padd = FF_INPUT_BUFFER_PADDING_SIZE;
memset(FDB->data_ + size, 0, padd);
av_init_packet(dst);
dst->data = FDB->data_;
dst->size = size;
}
// Ensure we don't loop forever
const uint32_t maxiteration = 8096;
static const uint64_t FUZZ_TAG = 0x4741542D5A5A5546ULL;
int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
const uint64_t fuzz_tag = FUZZ_TAG;
FuzzDataBuffer buffer;
const uint8_t *last = data;
const uint8_t *end = data + size;
uint32_t it = 0;
if (!c)
c = AVCodecInitialize(FFMPEG_CODEC); // Done once.
AVCodecContext* ctx = avcodec_alloc_context3(NULL);
if (!ctx)
error("Failed memory allocation");
ctx->max_pixels = 4096 * 4096; //To reduce false positive OOM and hangs
int res = avcodec_open2(ctx, c, NULL);
if (res < 0)
return res;
FDBCreate(&buffer);
int got_frame;
AVFrame *frame = av_frame_alloc();
if (!frame)
error("Failed memory allocation");
// Read very simple container
AVPacket avpkt;
while (data < end && it < maxiteration) {
// Search for the TAG
while (data + sizeof(fuzz_tag) < end) {
if (data[0] == (fuzz_tag & 0xFF) && *(const uint64_t *)(data) == fuzz_tag)
break;
data++;
}
if (data + sizeof(fuzz_tag) > end)
data = end;
FDBPrepare(&buffer, &avpkt, last, data - last);
data += sizeof(fuzz_tag);
last = data;
// Iterate through all data
while (avpkt.size > 0 && it++ < maxiteration) {
av_frame_unref(frame);
int ret = decode_handler(ctx, frame, &got_frame, &avpkt);
if (ret <= 0 || ret > avpkt.size)
break;
avpkt.data += ret;
avpkt.size -= ret;
}
}
av_init_packet(&avpkt);
avpkt.data = NULL;
avpkt.size = 0;
do {
got_frame = 0;
decode_handler(ctx, frame, &got_frame, &avpkt);
} while (got_frame == 1 && it++ < maxiteration);
av_frame_free(&frame);
avcodec_free_context(&ctx);
av_freep(&ctx);
FDBDesroy(&buffer);
return 0;
}
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