remoting/protocol/negotiating_client_authenticator.cc

   1 // Copyright 2013 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 #include "remoting/protocol/negotiating_client_authenticator.h"
   6
   7 #include <algorithm>
   8 #include <sstream>
   9
  10 #include "base/bind.h"
  11 #include "base/callback.h"
  12 #include "base/logging.h"
  13 #include "base/strings/string_split.h"
  14 #include "remoting/protocol/channel_authenticator.h"
  15 #include "remoting/protocol/pairing_client_authenticator.h"
  16 #include "remoting/protocol/v2_authenticator.h"
  17 #include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
  18
  19 namespace remoting {
  20 namespace protocol {
  21
  22 NegotiatingClientAuthenticator::NegotiatingClientAuthenticator(
  23     const std::string& client_pairing_id,
  24     const std::string& shared_secret,
  25     const std::string& authentication_tag,
  26     const FetchSecretCallback& fetch_secret_callback,
  27     scoped_ptr<ThirdPartyClientAuthenticator::TokenFetcher> token_fetcher,
  28     const std::vector<AuthenticationMethod>& methods)
  29     : NegotiatingAuthenticatorBase(MESSAGE_READY),
  30       client_pairing_id_(client_pairing_id),
  31       shared_secret_(shared_secret),
  32       authentication_tag_(authentication_tag),
  33       fetch_secret_callback_(fetch_secret_callback),
  34       token_fetcher_(token_fetcher.Pass()),
  35       method_set_by_host_(false),
  36       weak_factory_(this) {
  37   DCHECK(!methods.empty());
  38   for (std::vector<AuthenticationMethod>::const_iterator it = methods.begin();
  39        it != methods.end(); ++it) {
  40     AddMethod(*it);
  41   }
  42 }
  43
  44 NegotiatingClientAuthenticator::~NegotiatingClientAuthenticator() {
  45 }
  46
  47 void NegotiatingClientAuthenticator::ProcessMessage(
  48     const buzz::XmlElement* message,
  49     const base::Closure& resume_callback) {
  50   DCHECK_EQ(state(), WAITING_MESSAGE);
  51
  52   std::string method_attr = message->Attr(kMethodAttributeQName);
  53   AuthenticationMethod method = AuthenticationMethod::FromString(method_attr);
  54
  55   // The host picked a method different from the one the client had selected.
  56   if (method != current_method_) {
  57     // The host must pick a method that is valid and supported by the client,
  58     // and it must not change methods after it has picked one.
  59     if (method_set_by_host_ || !method.is_valid() ||
  60         std::find(methods_.begin(), methods_.end(), method) == methods_.end()) {
  61       state_ = REJECTED;
  62       rejection_reason_ = PROTOCOL_ERROR;
  63       resume_callback.Run();
  64       return;
  65     }
  66
  67     current_method_ = method;
  68     method_set_by_host_ = true;
  69     state_ = PROCESSING_MESSAGE;
  70
  71     // Copy the message since the authenticator may process it asynchronously.
  72     base::Closure callback = base::Bind(
  73         &NegotiatingAuthenticatorBase::ProcessMessageInternal,
  74         base::Unretained(this), base::Owned(new buzz::XmlElement(*message)),
  75         resume_callback);
  76     CreateAuthenticatorForCurrentMethod(WAITING_MESSAGE, callback);
  77     return;
  78   }
  79   ProcessMessageInternal(message, resume_callback);
  80 }
  81
  82 scoped_ptr<buzz::XmlElement> NegotiatingClientAuthenticator::GetNextMessage() {
  83   DCHECK_EQ(state(), MESSAGE_READY);
  84
  85   // This is the first message to the host, send a list of supported methods.
  86   if (!current_method_.is_valid()) {
  87     // If no authentication method has been chosen, see if we can optimistically
  88     // choose one.
  89     scoped_ptr<buzz::XmlElement> result;
  90     CreatePreferredAuthenticator();
  91     if (current_authenticator_) {
  92       DCHECK(current_authenticator_->state() == MESSAGE_READY);
  93       result = GetNextMessageInternal();
  94     } else {
  95       result = CreateEmptyAuthenticatorMessage();
  96     }
  97
  98     // Include a list of supported methods.
  99     std::stringstream supported_methods(std::stringstream::out);
 100     for (std::vector<AuthenticationMethod>::iterator it = methods_.begin();
 101          it != methods_.end(); ++it) {
 102       if (it != methods_.begin())
 103         supported_methods << kSupportedMethodsSeparator;
 104       supported_methods << it->ToString();
 105     }
 106     result->AddAttr(kSupportedMethodsAttributeQName, supported_methods.str());
 107     state_ = WAITING_MESSAGE;
 108     return result.Pass();
 109   }
 110   return GetNextMessageInternal();
 111 }
 112
 113 void NegotiatingClientAuthenticator::CreateAuthenticatorForCurrentMethod(
 114     Authenticator::State preferred_initial_state,
 115     const base::Closure& resume_callback) {
 116   DCHECK(current_method_.is_valid());
 117   if (current_method_.type() == AuthenticationMethod::THIRD_PARTY) {
 118     // |ThirdPartyClientAuthenticator| takes ownership of |token_fetcher_|.
 119     // The authentication method negotiation logic should guarantee that only
 120     // one |ThirdPartyClientAuthenticator| will need to be created per session.
 121     DCHECK(token_fetcher_);
 122     current_authenticator_.reset(new ThirdPartyClientAuthenticator(
 123         token_fetcher_.Pass()));
 124     resume_callback.Run();
 125   } else {
 126     DCHECK(current_method_.type() == AuthenticationMethod::SPAKE2 ||
 127            current_method_.type() == AuthenticationMethod::SPAKE2_PAIR);
 128     bool pairing_supported =
 129         (current_method_.type() == AuthenticationMethod::SPAKE2_PAIR);
 130     SecretFetchedCallback callback = base::Bind(
 131         &NegotiatingClientAuthenticator::CreateV2AuthenticatorWithSecret,
 132         weak_factory_.GetWeakPtr(), preferred_initial_state, resume_callback);
 133     fetch_secret_callback_.Run(pairing_supported, callback);
 134   }
 135 }
 136
 137 void NegotiatingClientAuthenticator::CreatePreferredAuthenticator() {
 138   if (!client_pairing_id_.empty() && !shared_secret_.empty() &&
 139       std::find(methods_.begin(), methods_.end(),
 140                 AuthenticationMethod::Spake2Pair()) != methods_.end()) {
 141     // If the client specified a pairing id and shared secret, then create a
 142     // PairingAuthenticator.
 143     current_authenticator_.reset(new PairingClientAuthenticator(
 144         client_pairing_id_, shared_secret_, fetch_secret_callback_,
 145         authentication_tag_));
 146     current_method_ = AuthenticationMethod::Spake2Pair();
 147   }
 148 }
 149
 150 void NegotiatingClientAuthenticator::CreateV2AuthenticatorWithSecret(
 151     Authenticator::State initial_state,
 152     const base::Closure& resume_callback,
 153     const std::string& shared_secret) {
 154   current_authenticator_ = V2Authenticator::CreateForClient(
 155       AuthenticationMethod::ApplyHashFunction(
 156           current_method_.hash_function(), authentication_tag_, shared_secret),
 157       initial_state);
 158   resume_callback.Run();
 159 }
 160
 161 }  // namespace protocol
 162 }  // namespace remoting