71 lines
2.5 KiB
C++
71 lines
2.5 KiB
C++
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/*
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* Copyright (C) 2021 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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#define LOG_TAG "clearkey-AesDecryptor"
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#include <utils/Log.h>
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#include <openssl/aes.h>
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#include "AesCtrDecryptor.h"
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#include "ClearKeyTypes.h"
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namespace clearkeydrm {
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static const size_t kBlockBitCount = kBlockSize * 8;
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CdmResponseType AesCtrDecryptor::decrypt(const std::vector<uint8_t>& key, const Iv iv,
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const uint8_t* source, uint8_t* destination,
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const std::vector<int32_t>& clearDataLengths,
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const std::vector<int32_t>& encryptedDataLengths,
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size_t* bytesDecryptedOut) {
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if (key.size() != kBlockSize || clearDataLengths.size() != encryptedDataLengths.size()) {
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android_errorWriteLog(0x534e4554, "63982768");
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return clearkeydrm::ERROR_DECRYPT;
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}
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uint32_t blockOffset = 0;
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uint8_t previousEncryptedCounter[kBlockSize];
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memset(previousEncryptedCounter, 0, kBlockSize);
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size_t offset = 0;
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AES_KEY opensslKey;
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AES_set_encrypt_key(key.data(), kBlockBitCount, &opensslKey);
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Iv opensslIv;
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memcpy(opensslIv, iv, sizeof(opensslIv));
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for (size_t i = 0; i < clearDataLengths.size(); ++i) {
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int32_t numBytesOfClearData = clearDataLengths[i];
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if (numBytesOfClearData > 0) {
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memcpy(destination + offset, source + offset, numBytesOfClearData);
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offset += numBytesOfClearData;
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}
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int32_t numBytesOfEncryptedData = encryptedDataLengths[i];
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if (numBytesOfEncryptedData > 0) {
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AES_ctr128_encrypt(source + offset, destination + offset,
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numBytesOfEncryptedData, &opensslKey, opensslIv,
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previousEncryptedCounter, &blockOffset);
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offset += numBytesOfEncryptedData;
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}
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}
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*bytesDecryptedOut = offset;
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return clearkeydrm::OK;
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}
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} // namespace clearkeydrm
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