Merge "Added amrnb_dec_fuzzer"

/******************************************************************************

 *

 * Copyright (C) 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at:

 *

 * http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 *

 *****************************************************************************

 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore

 */

cc_fuzz {

    name: "amrnb_dec_fuzzer",

    host_supported: true,

    srcs: [

        "amrnb_dec_fuzzer.cpp",

    ],

    static_libs: [

        "libstagefright_amrnbdec",

        "libstagefright_amrnb_common",

        "liblog",

    ],

    target: {

        darwin: {

            enabled: false,

        },

    },

}

# Fuzzer for libstagefright_amrnbdec decoder

## 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-NB supports the following parameters:

1. Stream format (parameter name: `input_format`)

2. 3GPP frame type (parameter name: `frame_type`)

| Parameter| Valid Values| Configured Value|

|------------- |-------------| ----- |

| `input_format` | 0. `MIME_IETF` 1. `IF2` | Bit 0 (LSB) of 1st byte of data. |

| `frame_type`   | 0. `AMR_475` 1. `AMR_515` 2. `AMR_59` 3. `AMR_67`  4. `AMR_74` 5. `AMR_795` 6. `AMR_102` 7. `AMR_122`  | Bits 3, 4 and 5 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 decode operation was successful, the input is advanced by the frame size

which is based on `input_format` and `frame_type` selected.

If the decode 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_dec_fuzzer binary.

### Android

#### Steps to build

Build the fuzzer

```

  $ mm -j$(nproc) amrnb_dec_fuzzer

```

#### Steps to run

Create a directory CORPUS_DIR and copy some amrnb files to that folder

Push this directory to device.

To run on device

```

  $ adb sync data

  $ adb shell /data/fuzz/arm64/amrnb_dec_fuzzer/amrnb_dec_fuzzer CORPUS_DIR

```

To run on host

```

  $ $ANDROID_HOST_OUT/fuzz/x86_64/amrnb_dec_fuzzer/amrnb_dec_fuzzer CORPUS_DIR

```

## References:

 * http://llvm.org/docs/LibFuzzer.html

 * https://github.com/google/oss-fuzz

/******************************************************************************

 *

 * Copyright (C) 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at:

 *

 * http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 *

 *****************************************************************************

 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore

 */

#include <string.h>

#include <algorithm>

#include "gsmamr_dec.h"

// Constants for AMR-NB

constexpr int32_t kSamplesPerFrame = L_FRAME;

constexpr int32_t kBitsPerSample = 16;

constexpr int32_t kOutputBufferSize = kSamplesPerFrame * kBitsPerSample / 8;

const bitstream_format kBitStreamFormats[2] = {MIME_IETF, IF2};

const int32_t kLocalWmfDecBytesPerFrame[8] = {12, 13, 15, 17, 19, 20, 26, 31};

const int32_t kLocalIf2DecBytesPerFrame[8] = {13, 14, 16, 18, 19, 21, 26, 31};

class Codec {

 public:

  Codec() = default;

  ~Codec() { deInitDecoder(); }

  int16_t initDecoder();

  void deInitDecoder();

  void decodeFrames(const uint8_t *data, size_t size);

 private:

  void *mAmrHandle = nullptr;

};

int16_t Codec::initDecoder() { return GSMInitDecode(&mAmrHandle, (Word8 *)"AMRNBDecoder"); }

void Codec::deInitDecoder() { GSMDecodeFrameExit(&mAmrHandle); }

void Codec::decodeFrames(const uint8_t *data, size_t size) {

  while (size > 0) {

    uint8_t mode = *data;

    bool bit = mode & 0x01;

    bitstream_format bitsreamFormat = kBitStreamFormats[bit];

    int32_t frameSize = 0;

    /* Find frame type */

    Frame_Type_3GPP frameType = static_cast<Frame_Type_3GPP>((mode >> 3) & 0x07);

    ++data;

    --size;

    if (bit) {

      frameSize = kLocalIf2DecBytesPerFrame[frameType];

    } else {

      frameSize = kLocalWmfDecBytesPerFrame[frameType];

    }

    int16_t outputBuf[kOutputBufferSize];

    uint8_t *inputBuf = new uint8_t[frameSize];

    if (!inputBuf) {

      return;

    }

    int32_t minSize = std::min((int32_t)size, frameSize);

    memcpy(inputBuf, data, minSize);

    AMRDecode(mAmrHandle, frameType, inputBuf, outputBuf, bitsreamFormat);

    /* AMRDecode() decodes minSize number of bytes if decode is successful.

     * AMRDecode() returns -1 if decode fails.

     * Even if no bytes are decoded, increment by minSize to ensure fuzzer proceeds

     * to feed next data */

    data += minSize;

    size -= minSize;

    delete[] inputBuf;

  }

}

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

  if (size < 2) {

    return 0;

  }

  Codec *codec = new Codec();

  if (!codec) {

    return 0;

  }

  if (codec->initDecoder() == 0) {

    codec->decodeFrames(data, size);

  }

  delete codec;

  return 0;

}