Cast: Adding helper crypto classes

media/cast/utility/cast_decryption_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/utility/cast_decryption_handler.h"
+
+#include "base/logging.h"
+#include "crypto/encryptor.h"
+#include "crypto/symmetric_key.h"
+#include "media/cast/cast_defines.h"
+#include "media/cast/transport/cast_transport_defines.h"
+
+namespace media {
+namespace cast {
+
+CastDecryptionHandler::CastDecryptionHandler()
+    : key_(), iv_mask_(), decryptor_(), initialized_(false) {}
+
+CastDecryptionHandler::~CastDecryptionHandler() {}
+
+bool CastDecryptionHandler::Initialize(std::string aes_key,
+                                       std::string aes_iv_mask) {

[hubbe, 2014/01/31 17:46:22]

It looks like the Encryptor and Decryptor have the same Initialize function.
If that's true, it might be better to just have one class with both Encrypt and
Decrypt methods on it.

[mikhal1, 2014/01/31 18:22:47]

Good point.Done.
On 2014/01/31 17:46:22, hubbe wrote:

+  initialized_ = false;
+  if (aes_iv_mask.size() == transport::kAesKeySize &&
+      aes_key.size() == transport::kAesKeySize) {
+    iv_mask_ = aes_iv_mask;
+    key_.reset(
+        crypto::SymmetricKey::Import(crypto::SymmetricKey::AES, aes_key));
+    decryptor_.reset(new crypto::Encryptor());
+    decryptor_->Init(key_.get(), crypto::Encryptor::CTR, std::string());
+    initialized_ = true;
+  } else if (aes_iv_mask.size() != 0 || aes_key.size() != 0) {
+    DCHECK(false) << "Invalid crypto configuration";
+    return false;
+  }
+  return true;
+}
+
+bool CastDecryptionHandler::Decrypt(uint32 frame_id,
+                                    const base::StringPiece& ciphertext,
+                                    std::string* plaintext) {
+  if (!initialized_) {
+    return false;
+  }
+  if (!decryptor_->SetCounter(transport::GetAesNonce(frame_id, iv_mask_))) {
+    NOTREACHED() << "Failed to set counter";
+    return false;
+  }
+  if (!decryptor_->Decrypt(ciphertext, plaintext)) {
+    VLOG(1) << "Decryption error";
+    return false;
+  }
+  return true;
+}
+
+}  // namespace cast
+}  // namespace media