Third Party authentication protocol.

remoting/protocol/authenticator.h

Index: remoting/protocol/authenticator.h
diff --git a/remoting/protocol/authenticator.h b/remoting/protocol/authenticator.h
index b8aa37d4544220d010195f63a2e89be64f09f126..5fa0664649627abff92adfa3c115d3588bdec305 100644
--- a/remoting/protocol/authenticator.h
+++ b/remoting/protocol/authenticator.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace buzz {
@@ -38,9 +39,14 @@ class Authenticator {
   //    WAITING_MESSAGE -> MESSAGE_READY
   //    WAITING_MESSAGE -> ACCEPTED
   //    WAITING_MESSAGE -> REJECTED
+  //    WAITING_MESSAGE -> WAITING_EXTERNAL

[Wez, 2013/02/27 07:05:30]

I don't like "external" - can we call this WAITING_LOCAL, WAITING_ACTION,
WAITING_USER or something along those lines?  I realise we won't always actually
need an action from the user but this is where user-interaction fits in so I
think it'd be reasonable.

[rmsousa, 2013/03/05 03:30:24]

Done in another CL.

   // When GetNextMessage() is called:
   //    MESSAGE_READY -> WAITING_MESSAGE
   //    MESSAGE_READY -> ACCEPTED
+  // When PerformExternalAction() is called:
+  //    WAITING_EXTERNAL -> MESSAGE_READY
+  //    WAITING_EXTERNAL -> ACCEPTED
+  //    WAITING_EXTERNAL -> REJECTED
   enum State {
     // Waiting for the next message from the peer.
     WAITING_MESSAGE,
@@ -53,6 +59,9 @@ class Authenticator {
 
     // Session is rejected.
     REJECTED,
+
+    // Waiting for PerformExternalAction to be called, or its action to finish.
+    WAITING_EXTERNAL,
   };
 
   enum RejectionReason {
@@ -89,6 +98,10 @@ class Authenticator {
   // authentication message that needs to be sent to the peer.
   virtual scoped_ptr<buzz::XmlElement> GetNextMessage() = 0;
 
+  // Must be called when in WAITING_EXTERNAL state. Performs the external action
+  // (e.g. user prompt, network request), and calls |resume_callback| when done.
+  virtual void PerformExternalAction(const base::Closure& resume_callback);

[Wez, 2013/02/27 07:05:30]

nit: We don't provide a no-message default impl for GetNextMessage, so I'm not
sure we need one here?

Rather than having a separate PerformExternalAction API, could we add a
completion callback to ProcessMessage(), and letting that return true if it
processed the message immediately, or false if the caller needs to wait for the
completion callback?  The caller really doesn't care that the Authenticator is
performing some other activity as part of the auth process.

[rmsousa, 2013/03/05 03:30:24]

Done in another CL.

+
   // Creates new authenticator for a channel. Can be called only in
   // the ACCEPTED state.
   virtual scoped_ptr<ChannelAuthenticator>