Merge changes Ia449e521,Iaa6cd313 am: 97730f6c

}

cc_library_shared {

cc_library {

    name: "libmediadrm",

    srcs: [

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

 *

 * 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: "mediadrm_fuzzer",

    srcs: [

        "mediadrm_fuzzer.cpp",

    ],

    static_libs: [

        "libmediadrm",

        "liblog",

        "resourcemanager_aidl_interface-ndk_platform",

    ],

    header_libs: [

        "libmedia_headers",

        "libmediadrm_headers",

    ],

    shared_libs: [

        "libbinder",

        "libutils",

        "libbinder_ndk",

        "libcutils",

        "libdl",

        "libmedia",

        "libmediadrmmetrics_lite",

        "libmediametrics#1",

        "libmediautils",

        "libstagefright_foundation",

        "android.hardware.drm@1.0",

        "android.hardware.drm@1.1",

        "android.hardware.drm@1.2",

        "android.hardware.drm@1.3",

        "libhidlallocatorutils",

        "libhidlbase",

    ],

    fuzz_config: {

        cc: [

            "android-media-fuzzing-reports@google.com",

        ],

        componentid: 155276,

    },

}

# Fuzzer for libmediadrm

## Plugin Design Considerations

The fuzzer plugin for libmediadrm is designed based on the understanding of the

library 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.

libmediadrm 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.`DrmPlugin::kSecurityLevelUnknown` 1.`DrmPlugin::kSecurityLevelMax` 2.`DrmPlugin::kSecurityLevelSwSecureCrypto` 3.`DrmPlugin::kSecurityLevelSwSecureDecode`  4.`DrmPlugin::kSecurityLevelHwSecureCrypto` 5.`DrmPlugin::kSecurityLevelHwSecureDecode` 6.`DrmPlugin::kSecurityLevelHwSecureAll`| Value obtained from FuzzedDataProvider in the range 0 to 6|

| `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.`video/unknown`| Value obtained from FuzzedDataProvider in the range 0 to 13|

| `keyType` | 0.`DrmPlugin::kKeyType_Offline` 1.`DrmPlugin::kKeyType_Streaming` 2.`DrmPlugin::kKeyType_Release` | Value obtained from FuzzedDataProvider in the range 0 to 2|

| `cryptoMode` | 0.`CryptoPlugin::kMode_Unencrypted` 1.`CryptoPlugin::kMode_AES_CTR` 2.`CryptoPlugin::kMode_AES_WV` 3.`CryptoPlugin::kMode_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 drm 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 mediadrm_fuzzer binary.

### Android

#### Steps to build

Build the fuzzer

```

  $ mm -j$(nproc) mediadrm_fuzzer

```

#### Steps to run

Create a directory CORPUS_DIR

```

  $ adb shell mkdir CORPUS_DIR

```

To run on device

```

  $ adb sync data

  $ adb shell /data/fuzz/${TARGET_ARCH}/mediadrm_fuzzer/mediadrm_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 <binder/MemoryDealer.h>

#include <hidlmemory/FrameworkUtils.h>

#include <mediadrm/CryptoHal.h>

#include <mediadrm/DrmHal.h>

#include <utils/String8.h>

#include "fuzzer/FuzzedDataProvider.h"

#define AES_BLOCK_SIZE 16

#define UNUSED_PARAM __attribute__((unused))

using namespace std;

using namespace android;

using android::hardware::fromHeap;

using ::android::os::PersistableBundle;

using drm::V1_0::BufferType;

enum {

    INVALID_UUID = 0,

    PSSH_BOX_UUID,

    CLEARKEY_UUID,

};

static const uint8_t kInvalidUUID[16] = {0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70, 0x80,

                                         0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70, 0x80};

static const uint8_t kCommonPsshBoxUUID[16] = {0x10, 0x77, 0xEF, 0xEC, 0xC0, 0xB2, 0x4D, 0x02,

                                               0xAC, 0xE3, 0x3C, 0x1E, 0x52, 0xE2, 0xFB, 0x4B};

static const uint8_t kClearKeyUUID[16] = {0xE2, 0x71, 0x9D, 0x58, 0xA9, 0x85, 0xB3, 0xC9,

                                          0x78, 0x1A, 0xB0, 0x30, 0xAF, 0x78, 0xD3, 0x0E};

static const uint32_t kUUID[] = {INVALID_UUID, PSSH_BOX_UUID, CLEARKEY_UUID};

const DrmPlugin::SecurityLevel kSecurityLevel[] = {

    DrmPlugin::kSecurityLevelUnknown,        DrmPlugin::kSecurityLevelMax,

    DrmPlugin::kSecurityLevelSwSecureCrypto, DrmPlugin::kSecurityLevelSwSecureDecode,

    DrmPlugin::kSecurityLevelHwSecureCrypto, DrmPlugin::kSecurityLevelHwSecureDecode,

    DrmPlugin::kSecurityLevelHwSecureAll};

const char *kMimeType[] = {"video/mp4",   "video/mpeg",    "video/x-flv",  "video/mj2",

                           "video/3gp2",  "video/3gpp",    "video/3gpp2",  "audio/mp4",

                           "audio/mpeg",  "audio/aac",     "audio/3gp2",   "audio/3gpp",

                           "audio/3gpp2", "video/unknown", "audio/unknown"};

const DrmPlugin::KeyType kKeyType[] = {DrmPlugin::kKeyType_Offline, DrmPlugin::kKeyType_Streaming,

                                       DrmPlugin::kKeyType_Release};

const CryptoPlugin::Mode kCryptoMode[] = {CryptoPlugin::kMode_Unencrypted,

                                          CryptoPlugin::kMode_AES_CTR, CryptoPlugin::kMode_AES_WV,

                                          CryptoPlugin::kMode_AES_CBC};

const char *kCipherAlgorithm[] = {"AES/CBC/NoPadding", ""};

const char *kMacAlgorithm[] = {"HmacSHA256", ""};

const char *kRSAAlgorithm[] = {"RSASSA-PSS-SHA1", ""};

const size_t kNumSecurityLevel = size(kSecurityLevel);

const size_t kNumMimeType = size(kMimeType);

const size_t kNumKeyType = size(kKeyType);

const size_t kNumCryptoMode = size(kCryptoMode);

const size_t kNumUUID = size(kUUID);

const size_t kMaxStringLength = 100;

const size_t kMaxSubSamples = 10;

const size_t kMaxNumBytes = 1000;

struct DrmListener : virtual public IDrmClient {

   public:

    void sendEvent(DrmPlugin::EventType eventType UNUSED_PARAM,

                   const hardware::hidl_vec<uint8_t> &sessionId UNUSED_PARAM,

                   const hardware::hidl_vec<uint8_t> &data UNUSED_PARAM) override {}

    void sendExpirationUpdate(const hardware::hidl_vec<uint8_t> &sessionId UNUSED_PARAM,

                              int64_t expiryTimeInMS UNUSED_PARAM) override {}

    void sendKeysChange(const hardware::hidl_vec<uint8_t> &sessionId UNUSED_PARAM,

                        const std::vector<DrmKeyStatus> &keyStatusList UNUSED_PARAM,

                        bool hasNewUsableKey UNUSED_PARAM) override {}

    void sendSessionLostState(const hardware::hidl_vec<uint8_t> &) override {}

    DrmListener() {}

   private:

    DISALLOW_EVIL_CONSTRUCTORS(DrmListener);

};

class DrmFuzzer {

   public:

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

   private:

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

    bool initDrm();

    void invokeDrmCreatePlugin();

    void invokeDrmOpenSession();

    void invokeDrmSetListener();

    void invokeDrmSetAlgorithmAPI();

    void invokeDrmPropertyAPI();

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

    void invokeDrmSecureStopAPI();

    void invokeDrmOfflineLicenseAPI();

    void invokeDrmCloseSession();

    void invokeDrmDestroyPlugin();

    void invokeCrypto(const uint8_t *data);

    bool initCrypto();

    void invokeCryptoCreatePlugin();

    void invokeCryptoDecrypt(const uint8_t *data);

    void invokeCryptoDestroyPlugin();

    sp<DrmHal> mDrm = nullptr;

    sp<CryptoHal> mCrypto = nullptr;

    Vector<uint8_t> mSessionId = {};

    FuzzedDataProvider *mFuzzedDataProvider = nullptr;

};

bool DrmFuzzer::initDrm() {

    mDrm = new DrmHal();

    if (!mDrm) {

        return false;

    }

    return true;

}

void DrmFuzzer::invokeDrmCreatePlugin() {

    mDrm->initCheck();

    String8 packageName(mFuzzedDataProvider->ConsumeRandomLengthString(kMaxStringLength).c_str());

    uint32_t uuidEnum = kUUID[mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(0, kNumUUID - 1)];

    switch (uuidEnum) {

        case INVALID_UUID:

            mDrm->createPlugin(kInvalidUUID, packageName);

            break;

        case PSSH_BOX_UUID:

            mDrm->createPlugin(kCommonPsshBoxUUID, packageName);

            break;

        case CLEARKEY_UUID:

            mDrm->createPlugin(kClearKeyUUID, packageName);

            break;

        default:

            break;

    }

}

void DrmFuzzer::invokeDrmDestroyPlugin() { mDrm->destroyPlugin(); }

void DrmFuzzer::invokeDrmOpenSession() {

    DrmPlugin::SecurityLevel securityLevel;

    bool shouldPassRandomSecurityLevel = mFuzzedDataProvider->ConsumeBool();

    if (shouldPassRandomSecurityLevel) {

        securityLevel =

            static_cast<DrmPlugin::SecurityLevel>(mFuzzedDataProvider->ConsumeIntegral<size_t>());

    } else {

        securityLevel = kSecurityLevel[mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(

            0, kNumSecurityLevel - 1)];

    }

    mDrm->openSession(securityLevel, mSessionId);

}

void DrmFuzzer::invokeDrmCloseSession() { mDrm->closeSession(mSessionId); }

void DrmFuzzer::invokeDrmSetListener() {

    sp<DrmListener> listener = new DrmListener();

    mDrm->setListener(listener);

}

void DrmFuzzer::invokeDrmSetAlgorithmAPI() {

    mDrm->setCipherAlgorithm(mSessionId,

                             String8(kCipherAlgorithm[mFuzzedDataProvider->ConsumeBool()]));

    mDrm->setMacAlgorithm(mSessionId, String8(kMacAlgorithm[mFuzzedDataProvider->ConsumeBool()]));

}

void DrmFuzzer::invokeDrmPropertyAPI() {

    mDrm->setPropertyString(String8("property"), String8("value"));

    String8 stringValue;

    mDrm->getPropertyString(String8("property"), stringValue);

    Vector<uint8_t> value = {};

    mDrm->setPropertyByteArray(String8("property"), value);

    Vector<uint8_t> byteValue;

    mDrm->getPropertyByteArray(String8("property"), byteValue);

}

void DrmFuzzer::invokeDrmDecryptEncryptAPI(const uint8_t *data, size_t size) {

    uint32_t openSessions = 0;

    uint32_t maxSessions = 0;

    mDrm->getNumberOfSessions(&openSessions, &maxSessions);

    DrmPlugin::HdcpLevel connected;

    DrmPlugin::HdcpLevel max;

    mDrm->getHdcpLevels(&connected, &max);

    DrmPlugin::SecurityLevel securityLevel;

    mDrm->getSecurityLevel(mSessionId, &securityLevel);

    // isCryptoSchemeSupported() shall fill isSupported

    bool isSupported;

    String8 mimeType(

        kMimeType[mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(0, kNumMimeType - 1)]);

    mDrm->isCryptoSchemeSupported(kClearKeyUUID, mimeType, securityLevel, &isSupported);

    // getProvisionRequest() shall fill legacyRequest and legacyDefaultUrl

    String8 certificateType(

        mFuzzedDataProvider->ConsumeRandomLengthString(kMaxStringLength).c_str());

    String8 certAuthority(mFuzzedDataProvider->ConsumeRandomLengthString(kMaxStringLength).c_str());

    Vector<uint8_t> legacyRequest = {};

    String8 legacyDefaultUrl;

    mDrm->getProvisionRequest(certificateType, certAuthority, legacyRequest, legacyDefaultUrl);

    // provideProvisionResponse() shall fill certificate and wrappedKey

    Vector<uint8_t> provisionResponse = {};

    Vector<uint8_t> certificate = {};

    Vector<uint8_t> wrappedKey = {};

    mDrm->provideProvisionResponse(provisionResponse, certificate, wrappedKey);

    // getKeyRequest() shall fill keyRequest, defaultUrl and keyRequestType

    Vector<uint8_t> initData = {};

    initData.appendArray(data, size);

    DrmPlugin::KeyType keyType;

    bool shouldPassRandomKeyType = mFuzzedDataProvider->ConsumeBool();

    if (shouldPassRandomKeyType) {

        keyType = static_cast<DrmPlugin::KeyType>(mFuzzedDataProvider->ConsumeIntegral<size_t>());

    } else {

        keyType = kKeyType[mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(0, kNumKeyType - 1)];

    }

    KeyedVector<String8, String8> mdOptionalParameters = {};

    Vector<uint8_t> keyRequest = {};

    String8 defaultUrl;

    DrmPlugin::KeyRequestType keyRequestType;

    mDrm->getKeyRequest(mSessionId, initData, mimeType, keyType, mdOptionalParameters, keyRequest,

                        defaultUrl, &keyRequestType);

    // provideKeyResponse() shall fill keySetId

    Vector<uint8_t> keyResponse = {};

    keyResponse.appendArray(data, size);

    Vector<uint8_t> keySetId = {};

    mDrm->provideKeyResponse(mSessionId, keyResponse, keySetId);

    // restoreKeys

    mDrm->restoreKeys(mSessionId, keySetId);

    // queryKeyStatus() shall fill infoMap

    KeyedVector<String8, String8> infoMap = {};

    mDrm->queryKeyStatus(mSessionId, infoMap);

    // decrypt() shall fill outputVec

    Vector<uint8_t> keyIdVec = {};

    keyIdVec.appendArray(data, size);

    Vector<uint8_t> inputVec = {};

    inputVec.appendArray(data, size);

    Vector<uint8_t> ivVec = {};

    ivVec.appendArray(data, size);

    Vector<uint8_t> outputVec = {};

    mDrm->decrypt(mSessionId, keyIdVec, inputVec, ivVec, outputVec);

    // encrypt() shall fill outputVec

    mDrm->encrypt(mSessionId, keyIdVec, inputVec, ivVec, outputVec);

    // sign() shall fill signature

    Vector<uint8_t> message = {};

    message.appendArray(data, size);

    Vector<uint8_t> signature = {};

    mDrm->sign(mSessionId, keyIdVec, message, signature);

    // verify() shall fill match

    bool match;

    mDrm->verify(mSessionId, keyIdVec, message, signature, match);

    // signRSA() shall fill signature

    mDrm->signRSA(mSessionId, String8(kRSAAlgorithm[mFuzzedDataProvider->ConsumeBool()]), message,

                  wrappedKey, signature);

    mDrm->removeKeys(mSessionId);

}

void DrmFuzzer::invokeDrmSecureStopAPI() {

    // getSecureStops() shall fill secureStops

    List<Vector<uint8_t>> secureStops = {};

    mDrm->getSecureStops(secureStops);

    // getSecureStopIds() shall fill secureStopIds

    List<Vector<uint8_t>> secureStopIds = {};

    mDrm->getSecureStopIds(secureStopIds);

    // getSecureStop() shall fill secureStop

    Vector<uint8_t> ssid = {};

    Vector<uint8_t> secureStop = {};

    mDrm->getSecureStop(ssid, secureStop);

    mDrm->removeSecureStop(ssid);

    mDrm->releaseSecureStops(ssid);

    mDrm->removeAllSecureStops();

}

void DrmFuzzer::invokeDrmOfflineLicenseAPI() {

    // getOfflineLicenseKeySetIds() shall keySetIds

    List<Vector<uint8_t>> keySetIds = {};

    mDrm->getOfflineLicenseKeySetIds(keySetIds);

    // getOfflineLicenseState() shall fill state

    Vector<uint8_t> const keySetIdOfflineLicense = {};

    DrmPlugin::OfflineLicenseState state;

    mDrm->getOfflineLicenseState(keySetIdOfflineLicense, &state);

    mDrm->removeOfflineLicense(keySetIdOfflineLicense);

}

bool DrmFuzzer::initCrypto() {

    mCrypto = new CryptoHal();

    if (!mCrypto) {

        return false;

    }

    return true;

}

void DrmFuzzer::invokeCryptoCreatePlugin() {

    mCrypto->initCheck();

    mCrypto->isCryptoSchemeSupported(kClearKeyUUID);

    mCrypto->createPlugin(kClearKeyUUID, NULL, 0);

}

void DrmFuzzer::invokeCryptoDestroyPlugin() { mCrypto->destroyPlugin(); }

void DrmFuzzer::invokeCryptoDecrypt(const uint8_t *data) {

    mCrypto->requiresSecureDecoderComponent(

        kMimeType[mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(0, kNumMimeType - 1)]);

    uint32_t width = mFuzzedDataProvider->ConsumeIntegral<uint32_t>();

    uint32_t height = mFuzzedDataProvider->ConsumeIntegral<uint32_t>();

    mCrypto->notifyResolution(width, height);

    mCrypto->setMediaDrmSession(mSessionId);

    const CryptoPlugin::Pattern pattern = {0, 0};

    size_t totalSize = 0;

    size_t numSubSamples = mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(1, kMaxSubSamples);

    CryptoPlugin::SubSample subSamples[numSubSamples];

    for (size_t i = 0; i < numSubSamples; ++i) {

        uint32_t clearBytes =

            mFuzzedDataProvider->ConsumeIntegralInRange<uint32_t>(1, kMaxNumBytes);

        uint32_t encryptedBytes =

            mFuzzedDataProvider->ConsumeIntegralInRange<uint32_t>(1, kMaxNumBytes);

        subSamples[i].mNumBytesOfClearData = clearBytes;

        subSamples[i].mNumBytesOfEncryptedData = encryptedBytes;

        totalSize += subSamples[i].mNumBytesOfClearData;

        totalSize += subSamples[i].mNumBytesOfEncryptedData;

    }

    size_t heapSize = totalSize * 2;

    sp<MemoryDealer> dealer = new MemoryDealer(heapSize, "DrmFuzzerMemory");

    if (!dealer) {

        return;

    }

    sp<HidlMemory> heap = fromHeap(dealer->getMemoryHeap());

    if (!heap) {

        return;

    }

    int heapSeqNum = mCrypto->setHeap(heap);

    if (heapSeqNum < 0) {

        return;

    }

    const size_t segmentIndex = 0;

    const uint8_t keyId[AES_BLOCK_SIZE] = {};

    memcpy((void *)keyId, data, AES_BLOCK_SIZE);

    const uint8_t iv[AES_BLOCK_SIZE] = {};

    memset((void *)iv, 0, AES_BLOCK_SIZE);

    const SharedBuffer sourceBuffer = {.bufferId = segmentIndex, .offset = 0, .size = totalSize};

    const DestinationBuffer destBuffer = {

        .type = BufferType::SHARED_MEMORY,

        {.bufferId = segmentIndex, .offset = totalSize, .size = totalSize},

        .secureMemory = nullptr};

    const uint64_t offset = 0;

    AString *errorDetailMsg = nullptr;

    CryptoPlugin::Mode mode;

    bool shouldPassRandomCryptoMode = mFuzzedDataProvider->ConsumeBool();

    if (shouldPassRandomCryptoMode) {

        mode = static_cast<CryptoPlugin::Mode>(mFuzzedDataProvider->ConsumeIntegral<size_t>());

    } else {

        mode =

            kCryptoMode[mFuzzedDataProvider->ConsumeIntegralInRange<size_t>(0, kNumCryptoMode - 1)];

    }

    mCrypto->decrypt(keyId, iv, mode, pattern, sourceBuffer, offset, subSamples, numSubSamples,

                     destBuffer, errorDetailMsg);

    if (heapSeqNum >= 0) {

        mCrypto->unsetHeap(heapSeqNum);

    }

    heap.clear();

}

void DrmFuzzer::invokeDrm(const uint8_t *data, size_t size) {

    if (!initDrm()) {

        return;

    }

    invokeDrmCreatePlugin();

    invokeDrmOpenSession();

    invokeDrmSetAlgorithmAPI();

    invokeDrmSetListener();

    invokeDrmPropertyAPI();

    invokeDrmDecryptEncryptAPI(data, size);

    invokeDrmSecureStopAPI();

    invokeDrmOfflineLicenseAPI();

    invokeDrmCloseSession();

    invokeDrmDestroyPlugin();

}

void DrmFuzzer::invokeCrypto(const uint8_t *data) {

    if (!initCrypto()) {

        return;

    }

    invokeCryptoCreatePlugin();

    invokeCryptoDecrypt(data);

    invokeCryptoDestroyPlugin();

}

void DrmFuzzer::process(const uint8_t *data, size_t size) {

    mFuzzedDataProvider = new FuzzedDataProvider(data, size);

    invokeDrm(data, size);

    invokeCrypto(data);

    delete mFuzzedDataProvider;

}

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

    if (size < AES_BLOCK_SIZE) {

        return 0;

    }

    DrmFuzzer drmFuzzer;

    drmFuzzer.process(data, size);

    return 0;

}