1 /*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 //#define LOG_NDEBUG 0
18 #define LOG_TAG "ClearKeyCryptoPlugin"
19 #include <utils/Log.h>
20
21 #include <openssl/aes.h>
22
23 #include "AesCtrDecryptor.h"
24
25 namespace clearkeydrm {
26
27 static const size_t kBlockBitCount = kBlockSize * 8;
28
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)29 android::status_t AesCtrDecryptor::decrypt(const android::Vector<uint8_t>& key,
30 const Iv iv, const uint8_t* source,
31 uint8_t* destination,
32 const SubSample* subSamples,
33 size_t numSubSamples,
34 size_t* bytesDecryptedOut) {
35 uint32_t blockOffset = 0;
36 uint8_t previousEncryptedCounter[kBlockSize];
37 memset(previousEncryptedCounter, 0, kBlockSize);
38
39 size_t offset = 0;
40 AES_KEY opensslKey;
41 AES_set_encrypt_key(key.array(), kBlockBitCount, &opensslKey);
42 Iv opensslIv;
43 memcpy(opensslIv, iv, sizeof(opensslIv));
44
45 for (size_t i = 0; i < numSubSamples; ++i) {
46 const SubSample& subSample = subSamples[i];
47
48 if (subSample.mNumBytesOfClearData > 0) {
49 memcpy(destination + offset, source + offset,
50 subSample.mNumBytesOfClearData);
51 offset += subSample.mNumBytesOfClearData;
52 }
53
54 if (subSample.mNumBytesOfEncryptedData > 0) {
55 AES_ctr128_encrypt(source + offset, destination + offset,
56 subSample.mNumBytesOfEncryptedData, &opensslKey,
57 opensslIv, previousEncryptedCounter,
58 &blockOffset);
59 offset += subSample.mNumBytesOfEncryptedData;
60 }
61 }
62
63 *bytesDecryptedOut = offset;
64 return android::OK;
65 }
66
67 } // namespace clearkeydrm
68