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/libjingle/source/talk/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 virtual ~NegotiatingAuthenticatorBase(); 64 65 // Authenticator interface. 66 virtual State state() const OVERRIDE; 67 virtual RejectionReason rejection_reason() const OVERRIDE; 68 virtual scoped_ptr<ChannelAuthenticator> 69 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_ 111
