1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "media/cast/common/transport_encryption_handler.h"
6
7#include "base/logging.h"
8#include "crypto/encryptor.h"
9#include "crypto/symmetric_key.h"
10#include "media/cast/net/cast_transport_defines.h"
11
12namespace {
13
14// Crypto.
15const size_t kAesBlockSize = 16;
16const size_t kAesKeySize = 16;
17
18std::string GetAesNonce(uint32 frame_id, const std::string& iv_mask) {
19  std::string aes_nonce(kAesBlockSize, 0);
20
21  // Serializing frame_id in big-endian order (aes_nonce[8] is the most
22  // significant byte of frame_id).
23  aes_nonce[11] = frame_id & 0xff;
24  aes_nonce[10] = (frame_id >> 8) & 0xff;
25  aes_nonce[9] = (frame_id >> 16) & 0xff;
26  aes_nonce[8] = (frame_id >> 24) & 0xff;
27
28  for (size_t i = 0; i < kAesBlockSize; ++i) {
29    aes_nonce[i] ^= iv_mask[i];
30  }
31  return aes_nonce;
32}
33
34}  // namespace
35
36namespace media {
37namespace cast {
38
39TransportEncryptionHandler::TransportEncryptionHandler()
40    : key_(), encryptor_(), iv_mask_(), is_activated_(false) {}
41
42TransportEncryptionHandler::~TransportEncryptionHandler() {}
43
44bool TransportEncryptionHandler::Initialize(std::string aes_key,
45                                            std::string aes_iv_mask) {
46  is_activated_ = false;
47  if (aes_iv_mask.size() == kAesKeySize && aes_key.size() == kAesKeySize) {
48    iv_mask_ = aes_iv_mask;
49    key_.reset(
50        crypto::SymmetricKey::Import(crypto::SymmetricKey::AES, aes_key));
51    encryptor_.reset(new crypto::Encryptor());
52    encryptor_->Init(key_.get(), crypto::Encryptor::CTR, std::string());
53    is_activated_ = true;
54  } else if (aes_iv_mask.size() != 0 || aes_key.size() != 0) {
55    DCHECK_EQ(aes_iv_mask.size(), 0u)
56        << "Invalid Crypto configuration: aes_iv_mask.size";
57    DCHECK_EQ(aes_key.size(), 0u)
58        << "Invalid Crypto configuration: aes_key.size";
59    return false;
60  }
61  return true;
62}
63
64bool TransportEncryptionHandler::Encrypt(uint32 frame_id,
65                                         const base::StringPiece& data,
66                                         std::string* encrypted_data) {
67  if (!is_activated_)
68    return false;
69  if (!encryptor_->SetCounter(GetAesNonce(frame_id, iv_mask_))) {
70    NOTREACHED() << "Failed to set counter";
71    return false;
72  }
73  if (!encryptor_->Encrypt(data, encrypted_data)) {
74    NOTREACHED() << "Encrypt error";
75    return false;
76  }
77  return true;
78}
79
80bool TransportEncryptionHandler::Decrypt(uint32 frame_id,
81                                         const base::StringPiece& ciphertext,
82                                         std::string* plaintext) {
83  if (!is_activated_) {
84    return false;
85  }
86  if (!encryptor_->SetCounter(GetAesNonce(frame_id, iv_mask_))) {
87    NOTREACHED() << "Failed to set counter";
88    return false;
89  }
90  if (!encryptor_->Decrypt(ciphertext, plaintext)) {
91    VLOG(1) << "Decryption error";
92    return false;
93  }
94  return true;
95}
96
97}  // namespace cast
98}  // namespace media
99