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57 lines
1.8 KiB
57 lines
1.8 KiB
7 months ago
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# Fuzzer for libstagefright_mp3dec decoder
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## Plugin Design Considerations
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The fuzzer plugin for mp3 decoder is designed based on the understanding of the
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codec and tries to achieve the following:
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##### Maximize code coverage
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This fuzzer makes use of the following config parameters:
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1. Equalizer type (parameter name: `equalizerType`)
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| Parameter| Valid Values| Configured Value|
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|------------- |-------------| ----- |
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| `equalizerType` | 0. `flat ` 1. `bass_boost ` 2. `rock ` 3. `pop ` 4. `jazz ` 5. `classical ` 6. `talk ` 7. `flat_ ` | Bits 0, 1 and 2 of first byte of input stream |
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| `crcEnabled` | 0. `false ` 1. `true `| Bit 0 of second byte of input stream |
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##### Maximize utilization of input data
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The plugin feeds the entire input data to the codec using a loop.
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* If the decode operation was successful, the input is advanced by the number
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of bytes used by the decoder.
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* If the decode operation was un-successful, the input is advanced by 1 byte
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till it reaches a valid frame or end of stream.
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This ensures that the plugin tolerates any kind of input (empty, huge,
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malformed, etc) and doesnt `exit()` on any input and thereby increasing the
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chance of identifying vulnerabilities.
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## Build
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This describes steps to build mp3_dec_fuzzer binary.
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### Android
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#### Steps to build
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Build the fuzzer
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```
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$ mm -j$(nproc) mp3_dec_fuzzer
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```
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#### Steps to run
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Create a directory CORPUS_DIR and copy some mp3 files to that folder.
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Push this directory to device.
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To run on device
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```
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$ adb sync data
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$ adb shell /data/fuzz/arm64/mp3_dec_fuzzer/mp3_dec_fuzzer CORPUS_DIR
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```
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To run on host
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```
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$ $ANDROID_HOST_OUT/fuzz/x86_64/mp3_dec_fuzzer/mp3_dec_fuzzer CORPUS_DIR
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```
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## References:
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* http://llvm.org/docs/LibFuzzer.html
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* https://github.com/google/oss-fuzz
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