diff options
Diffstat (limited to 'drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp')
-rw-r--r-- | drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp b/drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp new file mode 100644 index 0000000..01f8d65 --- /dev/null +++ b/drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp @@ -0,0 +1,67 @@ +/* + * 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 |