Cast: Added support for AES-CTR crypto.

media/cast/video_receiver/video_receiver.cc

Index: media/cast/video_receiver/video_receiver.cc
diff --git a/media/cast/video_receiver/video_receiver.cc b/media/cast/video_receiver/video_receiver.cc
index 03ec0ea9565519fb4fbce52c552fa6b33246537e..d398331339f7a936f51e1cde0676639a5ee758e7 100644
--- a/media/cast/video_receiver/video_receiver.cc
+++ b/media/cast/video_receiver/video_receiver.cc
@@ -5,9 +5,11 @@
 #include "media/cast/video_receiver/video_receiver.h"
 
 #include <algorithm>
+
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
+#include "crypto/symmetric_key.h"
 #include "media/cast/cast_defines.h"
 #include "media/cast/framer/framer.h"
 #include "media/cast/video_receiver/video_decoder.h"
@@ -125,6 +127,18 @@ VideoReceiver::VideoReceiver(scoped_refptr<CastEnvironment> cast_environment,
       video_config.max_frame_rate / 1000;
   DCHECK(max_unacked_frames) << "Invalid argument";
 
+  if (video_config.aes_iv_mask.size() == kAesKeySize &&
+      video_config.aes_key.size() == kAesKeySize) {
+    iv_mask_ = video_config.aes_iv_mask;
+    crypto::SymmetricKey* key = crypto::SymmetricKey::Import(
+        crypto::SymmetricKey::AES, video_config.aes_key);
+    decryptor_.reset(new crypto::Encryptor());
+    decryptor_->Init(key, crypto::Encryptor::CTR, std::string());
+  } else if (video_config.aes_iv_mask.size() != 0 ||
+             video_config.aes_key.size() != 0) {
+    DCHECK(false) << "Invalid crypto configuration";
+  }
+
   framer_.reset(new Framer(cast_environment->Clock(),
                            incoming_payload_feedback_.get(),
                            video_config.incoming_ssrc,
@@ -200,6 +214,30 @@ void VideoReceiver::DecodeVideoFrameThread(
   }
 }
 
+bool VideoReceiver::DecryptVideoFrame(
+    scoped_ptr<EncodedVideoFrame>* video_frame) {
+  DCHECK(decryptor_) << "Invalid state";
+
+  scoped_ptr<EncodedVideoFrame> decrypted_video_frame(
+      new EncodedVideoFrame());
+
+  // TODO(pwestin): the frame id must be a 32 bit number.
+  decryptor_->SetCounter(GetAesNounce((*video_frame)->frame_id, iv_mask_));
+
+  if (!decryptor_->Decrypt((*video_frame)->data,
+                           &decrypted_video_frame->data)) {
+    return false;
+  }
+  decrypted_video_frame->codec = (*video_frame)->codec;
+  decrypted_video_frame->key_frame = (*video_frame)->key_frame;
+  decrypted_video_frame->frame_id = (*video_frame)->frame_id;
+  decrypted_video_frame->last_referenced_frame_id =
+      (*video_frame)->last_referenced_frame_id;
+
+  video_frame->swap(decrypted_video_frame);
+  return true;
+}
+
 // Called from the main cast thread.
 void VideoReceiver::GetEncodedVideoFrame(
     const VideoFrameEncodedCallback& callback) {
@@ -213,6 +251,14 @@ void VideoReceiver::GetEncodedVideoFrame(
     queued_encoded_callbacks_.push_back(callback);
     return;
   }
+
+  if (decryptor_) {
+    if (!DecryptVideoFrame(&encoded_frame)) {
+      DCHECK(false) << "Decryption error";
+      return;
+    }
+  }
+
   base::TimeTicks render_time;
   if (PullEncodedVideoFrame(rtp_timestamp, next_frame, &encoded_frame,
                             &render_time)) {
@@ -293,6 +339,13 @@ void VideoReceiver::PlayoutTimeout() {
   VLOG(1) << "PlayoutTimeout retrieved frame "
           << static_cast<int>(encoded_frame->frame_id);
 
+  if (decryptor_) {
+    if (!DecryptVideoFrame(&encoded_frame)) {
+      DCHECK(false) << "Decryption error";
+      return;
+    }
+  }
+
   base::TimeTicks render_time;
   if (PullEncodedVideoFrame(rtp_timestamp, next_frame, &encoded_frame,
                             &render_time)) {