[FFmpeg-cvslog] doc/examples: add fuzz target for individual ffmpeg APIs for in-process fuzzing with libFuzzer , AFL, and similar fuzzing engines.
Thomas Garnier
git at videolan.org
Fri Nov 4 23:43:01 EET 2016
ffmpeg | branch: master | Thomas Garnier <thgarnie at google.com> | Fri Oct 28 23:02:21 2016 +0200| [c06d9234101646d4bf3d239e4fba629a3e4e981f] | committer: Michael Niedermayer
doc/examples: add fuzz target for individual ffmpeg APIs for in-process fuzzing with libFuzzer, AFL, and similar fuzzing engines.
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c06d9234101646d4bf3d239e4fba629a3e4e981f
---
doc/examples/decoder_targeted.c | 201 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 201 insertions(+)
diff --git a/doc/examples/decoder_targeted.c b/doc/examples/decoder_targeted.c
new file mode 100644
index 0000000..f254f60
--- /dev/null
+++ b/doc/examples/decoder_targeted.c
@@ -0,0 +1,201 @@
+/*
+ * 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");
+ 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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