Created libattestation

/*

 * 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.

 */

#include <array>

namespace android {

/**

 * Invalid value of HMAC - SHA256. Any events with this HMAC value will be marked as not verified.

 */

constexpr std::array<uint8_t, 32> INVALID_HMAC = {0};

class HmacKeyManager {

public:

    HmacKeyManager();

    std::array<uint8_t, 32> sign(const uint8_t* data, size_t size) const;

private:

    const std::array<uint8_t, 128> mHmacKey;

};

} // namespace android

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 */

constexpr float AMOTION_EVENT_INVALID_CURSOR_POSITION = std::numeric_limits<float>::quiet_NaN();

/**

 * Invalid value of HMAC - SHA256. Any events with this HMAC value will be marked as not verified.

 */

constexpr std::array<uint8_t, 32> INVALID_HMAC = {0};

/*

 * Pointer coordinate data.

 */

// 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.

cc_library_static {

    name: "libattestation",

    cflags: [

        "-Wall",

        "-Wextra",

        "-Werror",

    ],

    srcs: [

        "HmacKeyManager.cpp"

    ],

    clang: true,

    shared_libs: [

        "liblog",

        "libcrypto",

    ],

}

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/*

 * 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.

 */

#include <attestation/HmacKeyManager.h>

#include <log/log.h>

#include <openssl/hmac.h>

#include <openssl/rand.h>

namespace android {

static std::array<uint8_t, 128> getRandomKey() {

    std::array<uint8_t, 128> key;

    if (RAND_bytes(key.data(), key.size()) != 1) {

        LOG_ALWAYS_FATAL("Can't generate HMAC key");

    }

    return key;

}

HmacKeyManager::HmacKeyManager() : mHmacKey(getRandomKey()) {}

std::array<uint8_t, 32> HmacKeyManager::sign(const uint8_t* data, size_t size) const {

    // SHA256 always generates 32-bytes result

    std::array<uint8_t, 32> hash;

    unsigned int hashLen = 0;

    uint8_t* result =

            HMAC(EVP_sha256(), mHmacKey.data(), mHmacKey.size(), data, size, hash.data(), &hashLen);

    if (result == nullptr) {

        ALOGE("Could not sign the data using HMAC");

        return INVALID_HMAC;

    }

    if (hashLen != hash.size()) {

        ALOGE("HMAC-SHA256 has unexpected length");

        return INVALID_HMAC;

    }

    return hash;

}

} // namespace android

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chaviw@google.com

svv@google.com

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