android13/frameworks/av/drm/mediadrm/plugins/clearkey/hidl/fuzzer

Fuzzer for android.hardware.drm@1.4-service.clearkey

Plugin Design Considerations

The fuzzer plugin for android.hardware.drm@1.4-service.clearkey is designed based on the understanding of the source code 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.

android.hardware.drm@1.4-service.clearkey supports the following parameters:

1. Security Level (parameter name: securityLevel)
2. Mime Type (parameter name: mimeType)
3. Key Type (parameter name: keyType)
4. Crypto Mode (parameter name: cryptoMode)

Parameter	Valid Values	Configured Value
securityLevel	0.SecurityLevel::UNKNOWN 1.SecurityLevel::SW_SECURE_CRYPTO 2.SecurityLevel::SW_SECURE_DECODE 3.SecurityLevel::HW_SECURE_CRYPTO 4.SecurityLevel::HW_SECURE_DECODE 5.SecurityLevel::HW_SECURE_ALL	Value obtained from FuzzedDataProvider in the range 0 to 5
mimeType	0.video/mp4 1.video/mpeg 2.video/x-flv 3.video/mj2 4.video/3gp2 5.video/3gpp 6.video/3gpp2 7.audio/mp4 8.audio/mpeg 9.audio/aac 10.audio/3gp2 11.audio/3gpp 12.audio/3gpp2 13.audio/webm 14.video/webm 15.webm 16.cenc 17.video/unknown 18.audio/unknown	Value obtained from FuzzedDataProvider in the range 0 to 18
keyType	0.KeyType::OFFLINE 1.KeyType::STREAMING 2.KeyType::RELEASE	Value obtained from FuzzedDataProvider in the range 0 to 2
cryptoMode	0.Mode::UNENCRYPTED 1.Mode::AES_CTR 2.Mode::AES_CBC_CTS 3.Mode::AES_CBC	Value obtained from FuzzedDataProvider in the range 0 to 3

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 module. 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 clearkeyV1.4_fuzzer binary.

Android

Steps to build

Build the fuzzer

  $ mm -j$(nproc) clearkeyV1.4_fuzzer

Steps to run

To run on device

  $ adb sync data
  $ adb shell /data/fuzz/${TARGET_ARCH}/clearkeyV1.4_fuzzer/vendor/hw/clearkeyV1.4_fuzzer

References:

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