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/*
* Copyright (C) 2014 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.
*/
//#define LOG_NDEBUG 0
#define LOG_TAG "ClearKeyCryptoPlugin"
#include <utils/Log.h>
#include <openssl/aes.h>
#include "AesCtrDecryptor.h"
namespace clearkeydrm {
static const size_t kBlockBitCount = kBlockSize * 8;
android::status_t AesCtrDecryptor::decrypt(const android::Vector<uint8_t>& key,
const Iv iv, const uint8_t* source,
uint8_t* destination,
const SubSample* subSamples,
size_t numSubSamples,
size_t* bytesDecryptedOut) {
uint32_t blockOffset = 0;
uint8_t previousEncryptedCounter[kBlockSize];
memset(previousEncryptedCounter, 0, kBlockSize);
size_t offset = 0;
AES_KEY opensslKey;
AES_set_encrypt_key(key.array(), kBlockBitCount, &opensslKey);
Iv opensslIv;
memcpy(opensslIv, iv, sizeof(opensslIv));
for (size_t i = 0; i < numSubSamples; ++i) {
const SubSample& subSample = subSamples[i];
if (subSample.mNumBytesOfClearData > 0) {
memcpy(destination + offset, source + offset,
subSample.mNumBytesOfClearData);
offset += subSample.mNumBytesOfClearData;
}
if (subSample.mNumBytesOfEncryptedData > 0) {
AES_ctr128_encrypt(source + offset, destination + offset,
subSample.mNumBytesOfEncryptedData, &opensslKey,
opensslIv, previousEncryptedCounter,
&blockOffset);
offset += subSample.mNumBytesOfEncryptedData;
}
}
*bytesDecryptedOut = offset;
return android::OK;
}
} // namespace clearkeydrm
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