[Draft] Fix canceling pin prompt causes host overload

remoting/protocol/authenticator.h

 // Copyright (c) 2012 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 REMOTING_PROTOCOL_AUTHENTICATOR_H_
 #define REMOTING_PROTOCOL_AUTHENTICATOR_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 71 matching lines @@
   // returns NULL otherwise.
   static const buzz::XmlElement* FindAuthenticatorMessage(
       const buzz::XmlElement* message);
 
   Authenticator() {}
   virtual ~Authenticator() {}
 
   // Returns current state of the authenticator.
   virtual State state() const = 0;
 
+  // Returns whether authentication has started. The chromoting host uses this
+  // method to starts the back off process to prevent malicious clients from
+  // guessing the PIN by spamming the host with auth requests.
+  virtual bool started() const = 0;
+
   // Returns rejection reason. Can be called only when in REJECTED state.
   virtual RejectionReason rejection_reason() const = 0;
 
   // Called in response to incoming message received from the peer.
   // Should only be called when in WAITING_MESSAGE state. Caller retains
   // ownership of |message|. |resume_callback| will be called when processing is
   // finished. The implementation must guarantee that |resume_callback| is not
   // called after the Authenticator is destroyed.
   virtual void ProcessMessage(const buzz::XmlElement* message,
                               const base::Closure& resume_callback) = 0;
@@ skipping 25 matching lines @@
   virtual scoped_ptr<Authenticator> CreateAuthenticator(
       const std::string& local_jid,
       const std::string& remote_jid,
       const buzz::XmlElement* first_message) = 0;
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_AUTHENTICATOR_H_