Fuzzer for libFraunhoferAAC decoder

Plugin Design Considerations

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

Maximize code coverage

This fuzzer makes use of the following config parameters:

1. Transport type (parameter name: TRANSPORT_TYPE)

Note: Value of TRANSPORT_TYPE could be set to any of these values. It is set to TT_MP4_ADIF in the fuzzer plugin.

Maximize utilization of input data

The plugin feeds the entire input data to the codec using a loop.

• If the decode operation was successful, the input is advanced by an offset calculated using valid bytes.
• If the decode operation was un-successful, the input is advanced by 1 byte till it reaches a valid frame or end of stream.

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 aac_dec_fuzzer binary.

Android

Steps to build

Build the fuzzer

  $ mm -j$(nproc) aac_dec_fuzzer

Steps to run

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

To run on device

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

To run on host

  $ $ANDROID_HOST_OUT/fuzz/x86_64/aac_dec_fuzzer/aac_dec_fuzzer CORPUS_DIR

Fuzzer for libFraunhoferAAC encoder

Plugin Design Considerations

The fuzzer plugin for aac encoder 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.

Following arguments are passed to aacEncoder_SetParam to set the respective AACENC_PARAM parameter:

Following values are configured to set up the meta data represented by the class variable mMetaData : | Variable name| Possible Values| Configured Value| |------------- | ----- |----- | | drc_profile | AACENC_METADATA_DRC_NONE AACENC_METADATA_DRC_FILMSTANDARD AACENC_METADATA_DRC_FILMLIGHT AACENC_METADATA_DRC_MUSICSTANDARD AACENC_METADATA_DRC_MUSICLIGHT AACENC_METADATA_DRC_SPEECH AACENC_METADATA_DRC_NOT_PRESENT | Calculated using tenth byte of data | | comp_profile | AACENC_METADATA_DRC_NONE AACENC_METADATA_DRC_FILMSTANDARD AACENC_METADATA_DRC_FILMLIGHT AACENC_METADATA_DRC_MUSICSTANDARD AACENC_METADATA_DRC_MUSICLIGHT AACENC_METADATA_DRC_SPEECH AACENC_METADATA_DRC_NOT_PRESENT | Calculated using eleventh byte of data | | drc_TargetRefLevel | In range 0 to 255 | Calculated using twelfth byte of data | | comp_TargetRefLevel | In range 0 to 255 | Calculated using thirteenth byte of data | | prog_ref_level_present | 0 1 | Calculated using fourteenth byte of data | | prog_ref_level | In range 0 to 255 | Calculated using fifteenth byte of data | | PCE_mixdown_idx_present | 0 1 | Calculated using sixteenth byte of data | | ETSI_DmxLvl_present | 0 1 | Calculated using seventeenth byte of data | | centerMixLevel | In range 0 to 7 | Calculated using eighteenth byte of data | | surroundMixLevel | In range 0 to 7 | Calculated using nineteenth byte of data | | dolbySurroundMode | In range 0 to 2 | Calculated using twentieth byte of data | | drcPresentationMode | In range 0 to 2 | Calculated using twenty-first byte of data | | extAncDataEnable | 0 1 | Calculated using twenty-second byte of data | | extDownmixLevelEnable | 0 1 | Calculated using twenty-third byte of data | | extDownmixLevel_A | In range 0 to 7 | Calculated using twenty-fourth byte of data | | extDownmixLevel_B | In range 0 to 7 | Calculated using twenty-fifth byte of data | | dmxGainEnable | 0 1 | Calculated using twenty-sixth byte of data | | dmxGain5 | In range 0 to 255 | Calculated using twenty-seventh byte of data | | dmxGain2 | In range 0 to 255 | Calculated using twenty-eighth byte of data | | lfeDmxEnable | 0 1 | Calculated using twenty-ninth byte of data | | lfeDmxLevel | In range 0 to 15 | Calculated using thirtieth byte of data |

Indexes mInBufferIdx_1, mInBufferIdx_2 and mInBufferIdx_3(in range 0 to 2) are calculated using the thirty-first, thirty-second and thirty-third byte respectively.

Maximize utilization of input data

The plugin feeds the entire input data to the codec and continues with the encoding even on a failure. 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 aac_enc_fuzzer binary.

Android

Steps to build

Build the fuzzer

  $ mm -j$(nproc) aac_enc_fuzzer

Steps to run

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

To run on device

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

To run on host

  $ $ANDROID_HOST_OUT/fuzz/x86_64/aac_enc_fuzzer/aac_enc_fuzzer CORPUS_DIR

References:

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