components/proximity_auth/device_to_device_secure_context.cc

   1 // Copyright 2015 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 "components/proximity_auth/device_to_device_secure_context.h"
   6
   7 #include "base/bind.h"
   8 #include "base/callback.h"
   9 #include "components/proximity_auth/cryptauth/proto/cryptauth_api.pb.h"
  10 #include "components/proximity_auth/cryptauth/proto/securemessage.pb.h"
  11 #include "components/proximity_auth/cryptauth/secure_message_delegate.h"
  12 #include "components/proximity_auth/logging/logging.h"
  13
  14 namespace proximity_auth {
  15
  16 namespace {
  17
  18 // The version to put in the GcmMetadata field.
  19 const int kGcmMetadataVersion = 1;
  20
  21 // The sequence number of the last message used during authentication. These
  22 // messages are sent and received before the SecureContext is created.
  23 const int kAuthenticationSequenceNumber = 2;
  24
  25 }  // namespace
  26
  27 DeviceToDeviceSecureContext::DeviceToDeviceSecureContext(
  28     scoped_ptr<SecureMessageDelegate> secure_message_delegate,
  29     const std::string& symmetric_key,
  30     const std::string& responder_auth_message,
  31     ProtocolVersion protocol_version)
  32     : secure_message_delegate_(secure_message_delegate.Pass()),
  33       symmetric_key_(symmetric_key),
  34       responder_auth_message_(responder_auth_message),
  35       protocol_version_(protocol_version),
  36       last_sequence_number_(kAuthenticationSequenceNumber),
  37       weak_ptr_factory_(this) {}
  38
  39 DeviceToDeviceSecureContext::~DeviceToDeviceSecureContext() {}
  40
  41 void DeviceToDeviceSecureContext::Decode(const std::string& encoded_message,
  42                                          const MessageCallback& callback) {
  43   SecureMessageDelegate::UnwrapOptions unwrap_options;
  44   unwrap_options.encryption_scheme = securemessage::AES_256_CBC;
  45   unwrap_options.signature_scheme = securemessage::HMAC_SHA256;
  46
  47   secure_message_delegate_->UnwrapSecureMessage(
  48       encoded_message, symmetric_key_, unwrap_options,
  49       base::Bind(&DeviceToDeviceSecureContext::HandleUnwrapResult,
  50                  weak_ptr_factory_.GetWeakPtr(), callback));
  51 }
  52
  53 void DeviceToDeviceSecureContext::Encode(const std::string& message,
  54                                          const MessageCallback& callback) {
  55   // Create a GcmMetadata field to put in the header.
  56   cryptauth::GcmMetadata gcm_metadata;
  57   gcm_metadata.set_type(cryptauth::DEVICE_TO_DEVICE_MESSAGE);
  58   gcm_metadata.set_version(kGcmMetadataVersion);
  59
  60   // Wrap |message| inside a DeviceToDeviceMessage proto.
  61   securemessage::DeviceToDeviceMessage device_to_device_message;
  62   device_to_device_message.set_sequence_number(++last_sequence_number_);
  63   device_to_device_message.set_message(message);
  64
  65   SecureMessageDelegate::CreateOptions create_options;
  66   create_options.encryption_scheme = securemessage::AES_256_CBC;
  67   create_options.signature_scheme = securemessage::HMAC_SHA256;
  68   gcm_metadata.SerializeToString(&create_options.public_metadata);
  69
  70   secure_message_delegate_->CreateSecureMessage(
  71       device_to_device_message.SerializeAsString(), symmetric_key_,
  72       create_options, callback);
  73 }
  74
  75 std::string DeviceToDeviceSecureContext::GetReceivedAuthMessage() const {
  76   return responder_auth_message_;
  77 }
  78
  79 SecureContext::ProtocolVersion DeviceToDeviceSecureContext::GetProtocolVersion()
  80     const {
  81   return protocol_version_;
  82 }
  83
  84 void DeviceToDeviceSecureContext::HandleUnwrapResult(
  85     const DeviceToDeviceSecureContext::MessageCallback& callback,
  86     bool verified,
  87     const std::string& payload,
  88     const securemessage::Header& header) {
  89   // The payload should contain a DeviceToDeviceMessage proto.
  90   securemessage::DeviceToDeviceMessage device_to_device_message;
  91   if (!verified || !device_to_device_message.ParseFromString(payload)) {
  92     PA_LOG(ERROR) << "Failed to unwrap secure message.";
  93     callback.Run(std::string());
  94     return;
  95   }
  96
  97   // Check that the sequence number matches the expected sequence number.
  98   if (device_to_device_message.sequence_number() != last_sequence_number_ + 1) {
  99     PA_LOG(ERROR) << "Expected sequence_number=" << last_sequence_number_ + 1
 100                   << ", but got " << device_to_device_message.sequence_number();
 101     callback.Run(std::string());
 102     return;
 103   }
 104
 105   // Validate the GcmMetadata proto in the header.
 106   cryptauth::GcmMetadata gcm_metadata;
 107   if (!gcm_metadata.ParseFromString(header.public_metadata()) ||
 108       gcm_metadata.type() != cryptauth::DEVICE_TO_DEVICE_MESSAGE ||
 109       gcm_metadata.version() != kGcmMetadataVersion) {
 110     PA_LOG(ERROR) << "Failed to validate GcmMetadata.";
 111     callback.Run(std::string());
 112     return;
 113   }
 114
 115   last_sequence_number_++;
 116   callback.Run(device_to_device_message.message());
 117 }
 118
 119 }  // proximity_auth