Fuzzer for libavc decoder

This describes steps to build avc_dec_fuzzer binary.

Linux x86/x64

Requirements

• cmake (3.5 or above)
• make
• clang (6.0 or above) needs to support -fsanitize=fuzzer, -fsanitize=fuzzer-no-link

Steps to build

Clone libavc repository

$ git clone https://android.googlesource.com/platform/external/libavc

Create a directory inside libavc and change directory

 $ cd libavc
 $ mkdir build
 $ cd build

Build libavc using cmake

 $ CC=clang CXX=clang++ cmake ../ \
   -DSANITIZE=fuzzer-no-link,address,signed-integer-overflow
 $ make

Build the fuzzer

 $ clang++ -std=c++11 -fsanitize=fuzzer,address -I.  -I../  -I../common \
   -I../decoder -Wl,--start-group ../fuzzer/avc_dec_fuzzer.cpp \
   -o ./avc_dec_fuzzer ./libavcdec.a -Wl,--end-group

Steps to run

Create a directory CORPUS_DIR and copy some elementary h264 files to that folder To run the fuzzer

$ ./avc_dec_fuzzer CORPUS_DIR

Android

Steps to build

Build the fuzzer

  $ SANITIZE_TARGET=address SANITIZE_HOST=address mmma -j$(nproc) \
    external/libavc/fuzzer

Steps to run

Create a directory CORPUS_DIR and copy some elementary h264 files to that folder Push this directory to device.

To run on device

  $ adb sync data
  $ adb shell /data/fuzz/avc_dec_fuzzer CORPUS_DIR

To run on host

  $ $ANDROID_HOST_OUT/fuzz/avc_dec_fuzzer CORPUS_DIR

Fuzzer for libavc encoder

Plugin Design Considerations

The fuzzer plugin for AVC is designed based on the understanding of the codec and tries to achieve the following:

Maximize code coverage

The configuration parameters are not hardcoded, but instead selected based on incoming data. This ensures more code paths are reached by the fuzzer.

AVC supports the following parameters:

1. Frame Width (parameter name: u4_wd)
2. Frame Height (parameter name: u4_ht)
3. Input color format (parameter name: e_inp_color_fmt)
4. Architecture type (parameter name: e_arch)
5. Rate control mode (parameter name: e_rc_mode)
6. Number of cores (parameter name: u4_num_cores)
7. Maximum B frames (parameter name: u4_num_bframes)
8. Encoder speed preset (parameter name: u4_enc_speed_preset)
9. enable constrained intra prediction (parameter name: u4_constrained_intra_pred)
10. enable intra 4x4 (parameter name: u4_enable_intra_4x4)
11. Qp for I frames (parameter name: u4_i_qp)
12. Qp for P frames (parameter name: u4_p_qp)
13. Qp for B frames (parameter name: u4_b_qp)
14. Target Bitrate (parameter name: u4_target_bitrate)
15. Intra refresh period in frames (parameter name: u4_air_refresh_period)
16. Enable half pel ME (parameter name: u4_enable_hpel)
17. Enable quarter pel ME (parameter name: u4_enable_qpel)
18. ME speed preset (parameter name: u4_me_speed_preset)
19. Adaptive intra refresh mode (parameter name: e_air_mode)
20. Disable deblock level (parameter name: u4_disable_deblock_level)
21. Max search range in X direction (parameter name: u4_srch_rng_x)
22. Max search range in Y direction (parameter name: u4_srch_rng_y)
23. I frame interval (parameter name: u4_i_frm_interval)
24. IDR frame interval (parameter name: u4_idr_frm_interval)
25. Enable mastering display color volume info (parameter name: u1_sei_mdcv_params_present_flag)
26. Enable content light level info (parameter name: u1_sei_cll_params_present_flag)
27. Enable ambient viewing environment info (parameter name: u1_sei_ave_params_present_flag)
28. Enable content color volume info (parameter name: u1_sei_ccv_params_present_flag)
29. Profile (parameter name: e_profile)
30. Enable aspect_ratio info (parameter name: u1_aspect_ratio_info_present_flag)
31. Enable NAL HRD parameters presence (parameter name: u1_nal_hrd_parameters_present_flag)
32. Enable VCL HRD parameters presence (parameter name: u1_vcl_hrd_parameters_present_flag)
33. Enable force IDR frame (parameter name: mIsForceIdrEnabled)
34. Enable dynamic bitrate change (parameter name: mIsDynamicBitRateChangeEnabled)
35. Enable dynamic framerate change (parameter name: mIsDynamicFrameRateChangeEnabled)
36. Force IDR frame number (parameter name: mForceIdrInterval)
37. Frame number for dynamic bitrate (parameter name: mDynamicBitRateInterval)
38. Frame number for dynamic framerate (parameter name: mDynamicFrameRateInterval)

This also ensures that the plugin is always deterministic for any given input.

Maximize utilization of input data

The plugin feeds the entire input data to the codec using a loop. If the encode operation was successful, the input is advanced by the frame size. If the encode operation was un-successful, the input is still advanced by frame size so that the fuzzer can proceed to feed the next frame.

This ensures that the plugin tolerates any kind of input (empty, huge, malformed, etc) and doesnt exit() on any input and thereby increasing the chance of identifying vulnerabilities.

Build

This describes steps to build avc_enc_fuzzer binary.

Android

Steps to build

Build the fuzzer

  $ mm -j$(nproc) avc_enc_fuzzer

Steps to run

Create a directory CORPUS_DIR and copy some yuv files to that folder Push this directory to device.

To run on device

  $ adb sync data
  $ adb shell /data/fuzz/arm64/avc_enc_fuzzer/avc_enc_fuzzer CORPUS_DIR

To run on host

  $ $ANDROID_HOST_OUT/fuzz/x86_64/avc_enc_fuzzer/avc_enc_fuzzer CORPUS_DIR

References:

• http://llvm.org/docs/LibFuzzer.html
• https://github.com/google/oss-fuzz