Cast: Adding helper crypto classes

media/cast/transport/utility/transport_encryption_handler.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/cast/transport/utility/transport_encryption_handler.h"
+
+#include "base/logging.h"
+#include "crypto/encryptor.h"
+#include "crypto/symmetric_key.h"
+#include "media/cast/transport/cast_transport_defines.h"
+
+namespace media {
+namespace cast {
+namespace transport {
+
+TransportEncryptionHandler::TransportEncryptionHandler()
+    : key_(), encryptor_(), iv_mask_(), initialized_(false) {}
+
+TransportEncryptionHandler::~TransportEncryptionHandler() {}
+
+bool TransportEncryptionHandler::Initialize(std::string aes_key,
+                                            std::string aes_iv_mask) {
+  initialized_ = false;
+  if (aes_iv_mask.size() == kAesKeySize && aes_key.size() == kAesKeySize) {
+    iv_mask_ = aes_iv_mask;
+    key_.reset(
+        crypto::SymmetricKey::Import(crypto::SymmetricKey::AES, aes_key));
+    encryptor_.reset(new crypto::Encryptor());
+    encryptor_->Init(key_.get(), crypto::Encryptor::CTR, std::string());
+    initialized_ = true;
+  } else if (aes_iv_mask.size() != 0 || aes_key.size() != 0) {
+    DCHECK_EQ(aes_iv_mask.size(), 0u)
+        << "Invalid Crypto configuration: aes_iv_mask.size";
+    DCHECK_EQ(aes_key.size(), 0u)
+        << "Invalid Crypto configuration: aes_key.size";
+    return false;
+  }
+  return true;
+}
+
+bool TransportEncryptionHandler::Encrypt(uint32 frame_id,
+                                         std::string data,
+                                         std::string* encrypted_data) {
+  if (!initialized_)
+    return false;
+  if (!encryptor_->SetCounter(GetAesNonce(frame_id, iv_mask_))) {
+    NOTREACHED() << "Failed to set counter";
+    return false;
+  }
+  if (!encryptor_->Encrypt(data, encrypted_data)) {
+    NOTREACHED() << "Encrypt error";
+    return false;
+  }
+  return true;
+}
+
+bool TransportEncryptionHandler::Decrypt(uint32 frame_id,
+                                         const base::StringPiece& ciphertext,
+                                         std::string* plaintext) {
+  if (!initialized_) {
+    return false;
+  }
+  if (!encryptor_->SetCounter(transport::GetAesNonce(frame_id, iv_mask_))) {
+    NOTREACHED() << "Failed to set counter";
+    return false;
+  }
+  if (!encryptor_->Decrypt(ciphertext, plaintext)) {
+    VLOG(1) << "Decryption error";
+    return false;
+  }
+  return true;
+}
+
+}  // namespace transport
+}  // namespace cast
+}  // namespace media