// 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 REMOTING_PROTOCOL_PAIRING_AUTHENTICATOR_BASE_H_ #define REMOTING_PROTOCOL_PAIRING_AUTHENTICATOR_BASE_H_ #include "base/memory/weak_ptr.h" #include "remoting/protocol/authenticator.h" #include "third_party/webrtc/libjingle/xmllite/xmlelement.h" namespace remoting { namespace protocol { // The pairing authenticator builds on top of V2Authenticator to add // support for PIN-less authentication via device pairing: // // * If a client device is already paired, it includes in the initial // authentication message a Client Id and the first SPAKE message // using the Paired Secret and HMAC_SHA256. // * If the host recognizes the Client Id, it looks up the corresponding // Paired Secret and continue the SPAKE exchange. // * If it does not recognize the Client Id, it initiates a SPAKE exchange // with HMAC_SHA256 using the PIN as the shared secret. The initial // message of this exchange includes an an error message, which // informs the client that the PIN-less connection failed and causes // it to prompt the user for a PIN to use for authentication // instead. // * If, at any point, the SPAKE exchange fails with the Paired Secret, // the endpoint that detects the failure initiates a new SPAKE exchange // using the PIN, and includes an error message to instruct the peer // to do likewise. // // If a client device is not already paired, but supports pairing, then // the V2Authenticator is used instead of this class. Only the method name // differs, which the client uses to determine that pairing should be offered // to the user (see NegotiatingHostAuthenticator::CreateAuthenticator and // NegotiatingClientAuthenticator::CreateAuthenticatorForCurrentMethod). class PairingAuthenticatorBase : public Authenticator { public: PairingAuthenticatorBase(); virtual ~PairingAuthenticatorBase(); // Authenticator interface. virtual State state() const OVERRIDE; virtual bool started() const OVERRIDE; virtual RejectionReason rejection_reason() const OVERRIDE; virtual void ProcessMessage(const buzz::XmlElement* message, const base::Closure& resume_callback) OVERRIDE; virtual scoped_ptr<buzz::XmlElement> GetNextMessage() OVERRIDE; virtual scoped_ptr<ChannelAuthenticator> CreateChannelAuthenticator() const OVERRIDE; protected: typedef base::Callback<void(scoped_ptr<Authenticator> authenticator)> SetAuthenticatorCallback; static const buzz::StaticQName kPairingInfoTag; static const buzz::StaticQName kClientIdAttribute; // Create a V2 authenticator in the specified state, prompting the user for // the PIN first if necessary. virtual void CreateV2AuthenticatorWithPIN( State initial_state, const SetAuthenticatorCallback& callback) = 0; // Amend an authenticator message, for example to add client- or host-specific // elements to it. virtual void AddPairingElements(buzz::XmlElement* message) = 0; // A non-fatal error message that derived classes should set in order to // cause the peer to be notified that pairing has failed and that it should // fall back on PIN authentication. This string need not be human-readable, // nor is it currently used other than being logged. std::string error_message_; // The underlying V2 authenticator, created with either the PIN or the // Paired Secret by the derived class. scoped_ptr<Authenticator> v2_authenticator_; // Derived classes must set this to True if the underlying authenticator is // using the Paired Secret. bool using_paired_secret_; private: // Helper methods for ProcessMessage and GetNextMessage void MaybeAddErrorMessage(buzz::XmlElement* message); bool HasErrorMessage(const buzz::XmlElement* message) const; void CheckForFailedSpakeExchange(const base::Closure& resume_callback); void SetAuthenticatorAndProcessMessage( const buzz::XmlElement* message, const base::Closure& resume_callback, scoped_ptr<Authenticator> authenticator); // Set to true if a PIN-based authenticator has been requested but has not // yet been set. bool waiting_for_authenticator_; base::WeakPtrFactory<PairingAuthenticatorBase> weak_factory_; DISALLOW_COPY_AND_ASSIGN(PairingAuthenticatorBase); }; } // namespace protocol } // namespace remoting #endif // REMOTING_PROTOCOL_PAIRING_AUTHENTICATOR_H_