Update CastSocket connection flow to check for receiver credentials.

chrome/browser/extensions/api/cast_channel/cast_auth_util.h

+// Copyright 2013 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_API_CAST_CHANNEL_CAST_AUTH_UTIL_H_
+#define CHROME_BROWSER_EXTENSIONS_API_CAST_CHANNEL_CAST_AUTH_UTIL_H_
+
+#include <string>
+
+namespace extensions {
+namespace api {
+namespace cast_channel {
+
+class CastMessage;
+
+// Authenticates the given |challenge_reply|:
+// 1. Signature contained in the reply is valid.
+// 2. Certficate used to sign is rooted to a trusted CA.
+bool AuthenticateChallengeReply(const CastMessage& challenge_reply,
+                                const std::string& peer_cert);
+
+}  // namespace cast_channel
+}  // namespace api
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_CAST_CHANNEL_CAST_AUTH_UTIL_H_