/*
  * 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-x86asm

     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 tools/target_dec_fuzzer.c -o target_dec_fuzzer -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:

     ./target_dec_fuzzer -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 "config.h"

 #include "libavutil/avassert.h"

 #include "libavutil/imgutils.h"

 #include "libavutil/intreadwrite.h"

 
 #include "libavcodec/avcodec.h"

 #include "libavcodec/bytestream.h"

 #include "libavformat/avformat.h"
 

 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);

 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;

     res = avcodec_find_decoder(codec_id);
     if (!res)
         error("Failed to find decoder");
     return res;
 }
 
 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;
 }
 
 // Class to handle buffer allocation and resize for each frame
 typedef struct FuzzDataBuffer {
     size_t size_;
     uint8_t *data_;
 } FuzzDataBuffer;
 

 static void FDBCreate(FuzzDataBuffer *FDB) {

     FDB->size_ = 0x1000;
     FDB->data_ = av_malloc(FDB->size_);
     if (!FDB->data_)
         error("Failed memory allocation");
 }
 

 static void FDBDesroy(FuzzDataBuffer *FDB) { av_free(FDB->data_); }

 static void FDBRealloc(FuzzDataBuffer *FDB, size_t size) {

     size_t needed = size + AV_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");
     }
 }
 

 static 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 > AV_INPUT_BUFFER_PADDING_SIZE)
         padd = AV_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;

     int (*decode_handler)(AVCodecContext *avctx, AVFrame *picture,
                           int *got_picture_ptr,
                           const AVPacket *avpkt) = NULL;

     if (!c) {
 #ifdef FFMPEG_DECODER
 #define DECODER_SYMBOL0(CODEC) ff_##CODEC##_decoder
 #define DECODER_SYMBOL(CODEC) DECODER_SYMBOL0(CODEC)
         extern AVCodec DECODER_SYMBOL(FFMPEG_DECODER);
         avcodec_register(&DECODER_SYMBOL(FFMPEG_DECODER));
 

         c = &DECODER_SYMBOL(FFMPEG_DECODER);

 #else
         avcodec_register_all();

         c = AVCodecInitialize(FFMPEG_CODEC);  // Done once.

 #endif

         av_log_set_level(AV_LOG_PANIC);

     }

     switch (c->type) {
     case AVMEDIA_TYPE_AUDIO   : decode_handler = avcodec_decode_audio4; break;
     case AVMEDIA_TYPE_VIDEO   : decode_handler = avcodec_decode_video2; break;
     case AVMEDIA_TYPE_SUBTITLE: decode_handler = subtitle_handler     ; break;
     }
 

     AVCodecContext* ctx = avcodec_alloc_context3(NULL);
     if (!ctx)
         error("Failed memory allocation");

 
     ctx->max_pixels = 4096 * 4096; //To reduce false positive OOM and hangs
 

     if (size > 1024) {
         GetByteContext gbc;
         bytestream2_init(&gbc, data + size - 1024, 1024);
         ctx->width                              = bytestream2_get_le32(&gbc);
         ctx->height                             = bytestream2_get_le32(&gbc);
         ctx->bit_rate                           = bytestream2_get_le64(&gbc);
         ctx->bits_per_coded_sample              = bytestream2_get_le32(&gbc);
         if (av_image_check_size(ctx->width, ctx->height, 0, ctx))
             ctx->width = ctx->height = 0;
         size -= 1024;
     }
 

     int res = avcodec_open2(ctx, c, NULL);

     if (res < 0) {
         av_free(ctx);

         return 0; // Failure of avcodec_open2() does not imply that a issue was found

     }

 
     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) && AV_RN64(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 (it > 20)
                 ctx->error_concealment = 0;
 

             if (ret <= 0 || ret > avpkt.size)
                break;

             if (ctx->codec_type != AVMEDIA_TYPE_AUDIO)
                 ret = avpkt.size;

             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;
 }