android13/packages/modules/Bluetooth/system/audio_hal_interface/fuzzer

Fuzzers for libbt-audio-hal-interface

Plugin Design Considerations

The fuzzer plugins for libbt-audio-hal-interface are designed based on the understanding of the source code and tries to achieve the following:

Maximize code coverage

The configuration parameters are not hard-coded, but instead selected based on incoming data. This ensures more code paths are reached by the fuzzers.

Fuzzers assigns values to the following parameters to pass on to libbt-audio-hal-interface:

1. A2DP Control Ack Status (parameter name: status)
2. A2DP supported codecs (parameter name: index)
3. Session Type (parameter name: sessionType)
4. Session Type V2_1 (parameter name: sessionType_2_1)
5. Sample Rates (parameter name: param.sampleRate)
6. Sample Rates V2_1 (parameter name: param.sampleRate)
7. BTAV Sample Rates (parameter name: a2dpCodecConfig.sample_rate)
8. Bits per Sample (parameter name: param.bitsPerSample)
9. BTAV A2DP Codec Bits per Sample (parameter name: a2dpCodecConfig.bits_per_sample)
10. Channel Mode (parameter name: param.channelMode)
11. A2DP Codec Channel Mode (parameter name: a2dpCodecConfig.channel_mode)
12. Sbc Subbands (parameter name: sbc.numSubbands)
13. Sbc alloc methods (parameter name: sbc.allocMethod )
14. Sbc Channel mode (parameter name: sbc.channelMode )
15. Sbc Block Length (parameter name: sbc.blockLength )
16. Aac Object Type (parameter name: aac.objectType)
17. Aac Variable Bit Rate (parameter name: aac.variableBitRateEnabled)
18. Ldac Quality Index (parameter name: ldac.qualityIndex)
19. Ldac Channel Mode (parameter name: ldac.channelMode)
20. Codec Type (parameter name: codecConfig.codecType)

Parameter	Valid Values	Configured Value
status	0.A2DP_CTRL_ACK_SUCCESS 1.A2DP_CTRL_ACK_FAILURE 2.A2DP_CTRL_ACK_INCALL_FAILURE 3.A2DP_CTRL_ACK_UNSUPPORTED 4.A2DP_CTRL_ACK_PENDING 5.A2DP_CTRL_ACK_DISCONNECT_IN_PROGRESS	Value obtained from FuzzedDataProvider
index	0.BTAV_A2DP_CODEC_INDEX_SOURCE_SBC 1.BTAV_A2DP_CODEC_INDEX_SOURCE_AAC 2.BTAV_A2DP_CODEC_INDEX_SOURCE_APTX 3.BTAV_A2DP_CODEC_INDEX_SOURCE_APTX_HD 4.BTAV_A2DP_CODEC_INDEX_SOURCE_LDAC 5.BTAV_A2DP_CODEC_INDEX_SINK_SBC 6.BTAV_A2DP_CODEC_INDEX_SINK_AAC 7.BTAV_A2DP_CODEC_INDEX_SINK_LDAC	Value obtained from FuzzedDataProvider
sessionType	0.SessionType::UNKNOWN 1.SessionType::A2DP_SOFTWARE_ENCODING_DATAPATH 2.SessionType::A2DP_HARDWARE_OFFLOAD_DATAPATH 3.SessionType::HEARING_AID_SOFTWARE_ENCODING_DATAPATH	Value obtained from FuzzedDataProvider
sessionType_2_1	0.SessionType_2_1::UNKNOWN 1.SessionType_2_1::A2DP_SOFTWARE_ENCODING_DATAPATH 2.SessionType_2_1::A2DP_HARDWARE_OFFLOAD_DATAPATH 3.SessionType_2_1::HEARING_AID_SOFTWARE_ENCODING_DATAPATH 4.SessionType_2_1::LE_AUDIO_SOFTWARE_ENCODING_DATAPATH 5.SessionType_2_1::LE_AUDIO_SOFTWARE_DECODED_DATAPATH 6.SessionType_2_1::LE_AUDIO_HARDWARE_OFFLOAD_ENCODING_DATAPATH 7.SessionType_2_1::LE_AUDIO_HARDWARE_OFFLOAD_DECODING_DATAPATH	Value obtained from FuzzedDataProvider
param.sampleRate	0.SampleRate::RATE_UNKNOWN 1.SampleRate::RATE_8000 2.SampleRate::RATE_16000 3.SampleRate::RATE_24000 4.SampleRate::RATE_32000 5.SampleRate::RATE_44100 6.SampleRate::RATE_48000	Value obtained from FuzzedDataProvider
param.sampleRate (V2_1)	0.SampleRate_2_1::RATE_UNKNOWN 1.SampleRate_2_1::RATE_8000 2.SampleRate_2_1::RATE_16000 3.SampleRate_2_1::RATE_24000 4.SampleRate_2_1::RATE_32000 5.SampleRate_2_1::RATE_44100 6.SampleRate_2_1::RATE_48000	Value obtained from FuzzedDataProvider
a2dpCodecConfig.sample_rate	0.BTAV_A2DP_CODEC_SAMPLE_RATE_NONE 1.BTAV_A2DP_CODEC_SAMPLE_RATE_44100 2.BTAV_A2DP_CODEC_SAMPLE_RATE_48000 3.BTAV_A2DP_CODEC_SAMPLE_RATE_88200 4.BTAV_A2DP_CODEC_SAMPLE_RATE_96000 5.BTAV_A2DP_CODEC_SAMPLE_RATE_176400 6.BTAV_A2DP_CODEC_SAMPLE_RATE_192000 7.BTAV_A2DP_CODEC_SAMPLE_RATE_16000 8.BTAV_A2DP_CODEC_SAMPLE_RATE_24000	Value obtained from FuzzedDataProvider
param.bitsPerSample	0.BitsPerSample::BITS_UNKNOWN 1.BitsPerSample::BITS_16 2.BitsPerSample::BITS_24 3.BitsPerSample::BITS_32	Value obtained from FuzzedDataProvider
a2dpCodecConfig.bits_per_sample	0.BTAV_A2DP_CODEC_BITS_PER_SAMPLE_NONE 1.BTAV_A2DP_CODEC_BITS_PER_SAMPLE_16 2.BTAV_A2DP_CODEC_BITS_PER_SAMPLE_24 3.BTAV_A2DP_CODEC_BITS_PER_SAMPLE_32	Value obtained from FuzzedDataProvider
param.channelMode	0.ChannelMode::UNKNOWN 1.ChannelMode::MONO 2.ChannelMode::STEREO	Value obtained from FuzzedDataProvider
a2dpCodecConfig.channel_mode	0.BTAV_A2DP_CODEC_CHANNEL_MODE_NONE 1.BTAV_A2DP_CODEC_CHANNEL_MODE_MONO 2.BTAV_A2DP_CODEC_CHANNEL_MODE_STEREO	Value obtained from FuzzedDataProvider
param.peerMtu	0.660 1.663 2.883 3.1005 4.1500	Value obtained from FuzzedDataProvider
sbc.numSubbands	0.SbcNumSubbands::SUBBAND_4 1.SbcNumSubbands::SUBBAND_8	Value obtained from FuzzedDataProvider
sbc.allocMethod	0.SbcAllocMethod::ALLOC_MD_S 1.SbcAllocMethod::ALLOC_MD_L	Value obtained from FuzzedDataProvider
sbc.channelMode	0.SbcChannelMode::UNKNOWN 1.SbcChannelMode::JOINT_STEREO 2.SbcChannelMode::STEREO 3.SbcChannelMode::DUAL 4.SbcChannelMode::MONO	Value obtained from FuzzedDataProvider
sbc.blockLength	0.SbcBlockLength::BLOCKS_4 1.SbcBlockLength::BLOCKS_8 2.SbcBlockLength::BLOCKS_12 3.SbcBlockLength::BLOCKS_16	Value obtained from FuzzedDataProvider
aac.objectType	0.AacObjectType::MPEG2_LC 1.AacObjectType::MPEG4_LC 2.AacObjectType::MPEG4_LTP 3.AacObjectType::MPEG4_SCALABLE	Value obtained from FuzzedDataProvider
aac.variableBitRateEnabled	0.AacVariableBitRate::DISABLED 1.AacVariableBitRate::ENABLED	Value obtained from FuzzedDataProvider
ldac.qualityIndex	0.LdacQualityIndex::QUALITY_HIGH 1.LdacQualityIndex::QUALITY_MID 2.LdacQualityIndex::QUALITY_LOW 3.LdacQualityIndex::QUALITY_ABR	Value obtained from FuzzedDataProvider
ldac.channelMode	0.LdacChannelMode::UNKNOWN 1.LdacChannelMode::STEREO 2.LdacChannelMode::DUAL 3.LdacChannelMode::MONO	Value obtained from FuzzedDataProvider
codecConfig.codecType	0.CodecType::APTX 1.CodecType::APTX_HD	Value obtained from FuzzedDataProvider

This also ensures that the plugins are always deterministic for any given input.

Maximize utilization of input data

The plugins feed the entire input data to the module. This ensures that the plugins tolerates any kind of input (empty, huge, malformed, etc) and doesn't exit() on any input and thereby increasing the chance of identifying vulnerabilities.

Build

This describes steps to build libbt_audio_hal_a2dp_encoding_fuzzer, libbt_audio_hal_le_audio_software_fuzzer, libbt_audio_hal_hearing_aid_software_encoding_fuzzer and libbt_audio_hal_client_interface_fuzzer binaries.

Android

Steps to build

Build the fuzzer

  $ mm -j$(nproc) libbt_audio_hal_a2dp_encoding_fuzzer
  $ mm -j$(nproc) libbt_audio_hal_le_audio_software_fuzzer
  $ mm -j$(nproc) libbt_audio_hal_hearing_aid_software_encoding_fuzzer
  $ mm -j$(nproc) libbt_audio_hal_client_interface_fuzzer

Steps to run

To run on device

  $ adb sync data
  $ adb shell /data/fuzz/arm64/libbt_audio_hal_a2dp_encoding_fuzzer/libbt_audio_hal_a2dp_encoding_fuzzer
  $ adb shell /data/fuzz/arm64/libbt_audio_hal_le_audio_software_fuzzer/libbt_audio_hal_le_audio_software_fuzzer
  $ adb shell /data/fuzz/arm64/libbt_audio_hal_hearing_aid_software_encoding_fuzzer/libbt_audio_hal_hearing_aid_software_encoding_fuzzer
  $ adb shell /data/fuzz/arm64/libbt_audio_hal_client_interface_fuzzer/libbt_audio_hal_client_interface_fuzzer

References:

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