52 lines
1.6 KiB
C++
52 lines
1.6 KiB
C++
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <attestation/HmacKeyManager.h>
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#include <log/log.h>
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#include <openssl/hmac.h>
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#include <openssl/rand.h>
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namespace android {
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static std::array<uint8_t, 128> getRandomKey() {
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std::array<uint8_t, 128> key;
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if (RAND_bytes(key.data(), key.size()) != 1) {
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LOG_ALWAYS_FATAL("Can't generate HMAC key");
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}
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return key;
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}
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HmacKeyManager::HmacKeyManager() : mHmacKey(getRandomKey()) {}
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std::array<uint8_t, 32> HmacKeyManager::sign(const uint8_t* data, size_t size) const {
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// SHA256 always generates 32-bytes result
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std::array<uint8_t, 32> hash;
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unsigned int hashLen = 0;
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uint8_t* result =
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HMAC(EVP_sha256(), mHmacKey.data(), mHmacKey.size(), data, size, hash.data(), &hashLen);
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if (result == nullptr) {
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ALOGE("Could not sign the data using HMAC");
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return INVALID_HMAC;
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}
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if (hashLen != hash.size()) {
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ALOGE("HMAC-SHA256 has unexpected length");
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return INVALID_HMAC;
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}
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return hash;
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}
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} // namespace android
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