remoting/protocol/negotiating_authenticator_base.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef REMOTING_PROTOCOL_NEGOTIATING_AUTHENTICATOR_BASE_H_
   6 #define REMOTING_PROTOCOL_NEGOTIATING_AUTHENTICATOR_BASE_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "remoting/protocol/authentication_method.h"
  15 #include "remoting/protocol/authenticator.h"
  16 #include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
  17
  18 namespace remoting {
  19 namespace protocol {
  20
  21 // This class provides the common base for a meta-authenticator that allows
  22 // clients and hosts that support multiple authentication methods to negotiate a
  23 // method to use.
  24 //
  25 // The typical flow is:
  26 //  * Client sends a message to host with its supported methods.
  27 //      (clients may additionally pick a method and send its first message).
  28 //  * Host picks a method and sends its first message (if any).
  29 //      (if a message for that method was sent by the client, it is processed).
  30 //  * Client creates the authenticator selected by the host. If the method
  31 //      starts with a message from the host, it is processed.
  32 //  * Client and host exchange messages until the authentication is ACCEPTED or
  33 //      REJECTED.
  34 //
  35 // The details:
  36 //  * CreateAuthenticator() may be asynchronous (i.e. require user interaction
  37 //      to determine initial parameters, like PIN). This happens inside
  38 //      ProcessMessage, so to the outside this behaves like any asynchronous
  39 //      message processing. Internally, CreateAuthenticator() receives a
  40 //      callback, that will resume the authentication once the authenticator is
  41 //      created. If there is already a message to be processed by the new
  42 //      authenticator, this callback includes a call to the underlying
  43 //      ProcessMessage().
  44 //  * Some authentication methods may have a specific starting direction (e.g.
  45 //      host always sends the first message), while others are versatile (e.g.
  46 //      SPAKE, where either side can send the first message). When an
  47 //      authenticator is created, it is given a preferred initial state, which
  48 //      the authenticator may ignore.
  49 //  * If the new authenticator state doesn't match the preferred one,
  50 //      the NegotiatingAuthenticator deals with that, by sending an empty
  51 //      <authenticator> stanza if the method has no message to send, and
  52 //      ignoring such empty messages on the receiving end.
  53 //  * The client may optimistically pick a method on its first message (assuming
  54 //      it doesn't require user interaction to start). If the host doesn't
  55 //      support that method, it will just discard that message, and choose
  56 //      another method from the client's supported methods list.
  57 //  * The host never sends its own supported methods back to the client, so once
  58 //      the host picks a method from the client's list, it's final.
  59 //  * Any change in this class must maintain compatibility between any version
  60 //      mix of webapp, client plugin and host, for both Me2Me and IT2Me.
  61 class NegotiatingAuthenticatorBase : public Authenticator {
  62  public:
  63   ~NegotiatingAuthenticatorBase() override;
  64
  65   // Authenticator interface.
  66   State state() const override;
  67   bool started() const override;
  68   RejectionReason rejection_reason() const override;
  69   scoped_ptr<ChannelAuthenticator> CreateChannelAuthenticator() const override;
  70
  71   // Calls |current_authenticator_| to process |message|, passing the supplied
  72   // |resume_callback|.
  73   void ProcessMessageInternal(const buzz::XmlElement* message,
  74                               const base::Closure& resume_callback);
  75
  76   const AuthenticationMethod& current_method_for_testing() const {
  77     return current_method_;
  78   }
  79
  80  protected:
  81   static const buzz::StaticQName kMethodAttributeQName;
  82   static const buzz::StaticQName kSupportedMethodsAttributeQName;
  83   static const char kSupportedMethodsSeparator;
  84
  85   explicit NegotiatingAuthenticatorBase(Authenticator::State initial_state);
  86
  87   void AddMethod(const AuthenticationMethod& method);
  88
  89   // Updates |state_| to reflect the current underlying authenticator state.
  90   // |resume_callback| is called after the state is updated.
  91   void UpdateState(const base::Closure& resume_callback);
  92
  93   // Gets the next message from |current_authenticator_|, if any, and fills in
  94   // the 'method' tag with |current_method_|.
  95   virtual scoped_ptr<buzz::XmlElement> GetNextMessageInternal();
  96
  97   std::vector<AuthenticationMethod> methods_;
  98   AuthenticationMethod current_method_;
  99   scoped_ptr<Authenticator> current_authenticator_;
 100   State state_;
 101   RejectionReason rejection_reason_;
 102
 103  private:
 104   DISALLOW_COPY_AND_ASSIGN(NegotiatingAuthenticatorBase);
 105 };
 106
 107 }  // namespace protocol
 108 }  // namespace remoting
 109
 110 #endif  // REMOTING_PROTOCOL_NEGOTIATING_AUTHENTICATOR_BASE_H_