v811_spc009/frameworks/av/media/codecs/amrnb/enc/fuzzer

Fuzzer for libstagefright_amrnbenc encoder

Plugin Design Considerations

The fuzzer plugin for AMR-NB 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.

AMR-WB supports the following parameters:

1. Output Format (parameter name: outputFormat)
2. Mode (parameter name: mode)

Parameter	Valid Values	Configured Value
outputFormat	0. AMR_TX_WMF 1. AMR_TX_IF2 2. AMR_TX_ETS	Bits 0, 1 and 2 of 1st byte of data.
mode	0. MR475 1. MR515 2. MR59 3. MR67 4. MR74 5. MR795 6. MR102 7. MR122 8. MRDTX	Bits 3, 4, 5 and 6 of 1st byte of data.

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 amrnb_enc_fuzzer binary.

Android

Steps to build

Build the fuzzer

  $ mm -j$(nproc) amrnb_enc_fuzzer

Steps to run

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

To run on device

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

To run on host

  $ $ANDROID_HOST_OUT/fuzz/x86_64/amrnb_enc_fuzzer/amrnb_enc_fuzzer CORPUS_DIR

References:

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