components/proximity_auth/messenger_impl.cc

// Copyright 2014 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.

#include "components/proximity_auth/messenger_impl.h"

#include <utility>

#include "base/base64url.h"
#include "base/bind.h"
#include "base/json/json_reader.h"
#include "base/json/json_writer.h"
#include "base/location.h"
#include "base/memory/ptr_util.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/values.h"
#include "components/proximity_auth/connection.h"
#include "components/proximity_auth/logging/logging.h"
#include "components/proximity_auth/messenger_observer.h"
#include "components/proximity_auth/remote_status_update.h"
#include "components/proximity_auth/secure_context.h"
#include "components/proximity_auth/wire_message.h"

namespace proximity_auth {
namespace {

// The key names of JSON fields for messages sent between the devices.
const char kTypeKey[] = "type";
const char kNameKey[] = "name";
const char kDataKey[] = "data";
const char kEncryptedDataKey[] = "encrypted_data";

// The types of messages that can be sent and received.
const char kMessageTypeLocalEvent[] = "event";
const char kMessageTypeRemoteStatusUpdate[] = "status_update";
const char kMessageTypeDecryptRequest[] = "decrypt_request";
const char kMessageTypeDecryptResponse[] = "decrypt_response";
const char kMessageTypeUnlockRequest[] = "unlock_request";
const char kMessageTypeUnlockResponse[] = "unlock_response";

// The name for an unlock event originating from the local device.
const char kUnlockEventName[] = "easy_unlock";

// Messages sent and received from the iOS app when polling for it's lock screen
// status.
// TODO(tengs): Unify the iOS status update protocol with the existing Android
// protocol, so we don't have this special case.
const char kPollScreenState[] = "PollScreenState";
const char kScreenUnlocked[] = "Screen Unlocked";
const char kScreenLocked[] = "Screen Locked";
const int kIOSPollingIntervalSeconds = 5;

// Serializes the |value| to a JSON string and returns the result.
std::string SerializeValueToJson(const base::Value& value) {
  std::string json;
  base::JSONWriter::Write(value, &json);
  return json;
}

// Returns the message type represented by the |message|. This is a convenience
// wrapper that should only be called when the |message| is known to specify its
// message type, i.e. this should not be called for untrusted input.
std::string GetMessageType(const base::DictionaryValue& message) {
  std::string type;
  message.GetString(kTypeKey, &type);
  return type;
}

}  // namespace

MessengerImpl::MessengerImpl(std::unique_ptr<Connection> connection,
                             std::unique_ptr<SecureContext> secure_context)
    : connection_(std::move(connection)),
      secure_context_(std::move(secure_context)),
      weak_ptr_factory_(this) {
  DCHECK(connection_->IsConnected());
  connection_->AddObserver(this);

  // TODO(tengs): We need CryptAuth to report if the phone runs iOS or Android,
  // rather than relying on this heuristic.
  if (connection_->remote_device().bluetooth_type == RemoteDevice::BLUETOOTH_LE)
    PollScreenStateForIOS();
}

MessengerImpl::~MessengerImpl() {
  if (connection_)
    connection_->RemoveObserver(this);
}

void MessengerImpl::AddObserver(MessengerObserver* observer) {
  observers_.AddObserver(observer);
}

void MessengerImpl::RemoveObserver(MessengerObserver* observer) {
  observers_.RemoveObserver(observer);
}

bool MessengerImpl::SupportsSignIn() const {
  // TODO(tengs): Support sign-in for Bluetooth LE protocol.
  return (secure_context_->GetProtocolVersion() ==
          SecureContext::PROTOCOL_VERSION_THREE_ONE) &&
         connection_->remote_device().bluetooth_type !=
             RemoteDevice::BLUETOOTH_LE;
}

void MessengerImpl::DispatchUnlockEvent() {
  base::DictionaryValue message;
  message.SetString(kTypeKey, kMessageTypeLocalEvent);
  message.SetString(kNameKey, kUnlockEventName);
  queued_messages_.push_back(PendingMessage(message));
  ProcessMessageQueue();
}

void MessengerImpl::RequestDecryption(const std::string& challenge) {
  if (!SupportsSignIn()) {
    PA_LOG(WARNING) << "Dropping decryption request, as remote device "
                    << "does not support protocol v3.1.";
    FOR_EACH_OBSERVER(MessengerObserver, observers_,
                      OnDecryptResponse(std::string()));
    return;
  }

  const std::string encrypted_message_data = challenge;
  std::string encrypted_message_data_base64;
  base::Base64UrlEncode(encrypted_message_data,
                        base::Base64UrlEncodePolicy::INCLUDE_PADDING,
                        &encrypted_message_data_base64);

  base::DictionaryValue message;
  message.SetString(kTypeKey, kMessageTypeDecryptRequest);
  message.SetString(kEncryptedDataKey, encrypted_message_data_base64);
  queued_messages_.push_back(PendingMessage(message));
  ProcessMessageQueue();
}

void MessengerImpl::RequestUnlock() {
  if (!SupportsSignIn()) {
    PA_LOG(WARNING) << "Dropping unlock request, as remote device does not "
                    << "support protocol v3.1.";
    FOR_EACH_OBSERVER(MessengerObserver, observers_, OnUnlockResponse(false));
    return;
  }

  base::DictionaryValue message;
  message.SetString(kTypeKey, kMessageTypeUnlockRequest);
  queued_messages_.push_back(PendingMessage(message));
  ProcessMessageQueue();
}

SecureContext* MessengerImpl::GetSecureContext() const {
  return secure_context_.get();
}

MessengerImpl::PendingMessage::PendingMessage() {}

MessengerImpl::PendingMessage::PendingMessage(
    const base::DictionaryValue& message)
    : json_message(SerializeValueToJson(message)),
      type(GetMessageType(message)) {}

MessengerImpl::PendingMessage::PendingMessage(const std::string& message)
    : json_message(message), type(std::string()) {}

MessengerImpl::PendingMessage::~PendingMessage() {}

void MessengerImpl::ProcessMessageQueue() {
  if (pending_message_ || queued_messages_.empty() ||
      connection_->is_sending_message())
    return;

  pending_message_.reset(new PendingMessage(queued_messages_.front()));
  queued_messages_.pop_front();

  secure_context_->Encode(pending_message_->json_message,
                          base::Bind(&MessengerImpl::OnMessageEncoded,
                                     weak_ptr_factory_.GetWeakPtr()));
}

void MessengerImpl::OnMessageEncoded(const std::string& encoded_message) {
  connection_->SendMessage(base::MakeUnique<WireMessage>(encoded_message));
}

void MessengerImpl::OnMessageDecoded(const std::string& decoded_message) {
  // TODO(tengs): Unify the iOS status update protocol with the existing Android
  // protocol, so we don't have this special case.
  if (decoded_message == kScreenUnlocked || decoded_message == kScreenLocked) {
    RemoteStatusUpdate update;
    update.user_presence =
        (decoded_message == kScreenUnlocked ? USER_PRESENT : USER_ABSENT);
    update.secure_screen_lock_state = SECURE_SCREEN_LOCK_ENABLED;
    update.trust_agent_state = TRUST_AGENT_ENABLED;
    FOR_EACH_OBSERVER(MessengerObserver, observers_,
                      OnRemoteStatusUpdate(update));
    pending_message_.reset();
    ProcessMessageQueue();
    return;
  }

  // The decoded message should be a JSON string.
  std::unique_ptr<base::Value> message_value =
      base::JSONReader::Read(decoded_message);
  if (!message_value || !message_value->IsType(base::Value::TYPE_DICTIONARY)) {
    PA_LOG(ERROR) << "Unable to parse message as JSON:\n" << decoded_message;
    return;
  }

  base::DictionaryValue* message;
  bool success = message_value->GetAsDictionary(&message);
  DCHECK(success);

  std::string type;
  if (!message->GetString(kTypeKey, &type)) {
    PA_LOG(ERROR) << "Missing '" << kTypeKey << "' key in message:\n "
                  << decoded_message;
    return;
  }

  // Remote status updates can be received out of the blue.
  if (type == kMessageTypeRemoteStatusUpdate) {
    HandleRemoteStatusUpdateMessage(*message);
    return;
  }

  // All other messages should only be received in response to a message that
  // the messenger sent.
  if (!pending_message_) {
    PA_LOG(WARNING) << "Unexpected message received:\n" << decoded_message;
    return;
  }

  std::string expected_type;
  if (pending_message_->type == kMessageTypeDecryptRequest)
    expected_type = kMessageTypeDecryptResponse;
  else if (pending_message_->type == kMessageTypeUnlockRequest)
    expected_type = kMessageTypeUnlockResponse;
  else
    NOTREACHED();  // There are no other message types that expect a response.

  if (type != expected_type) {
    PA_LOG(ERROR) << "Unexpected '" << kTypeKey << "' value in message. "
                  << "Expected '" << expected_type << "' but received '" << type
                  << "'.";
    return;
  }

  if (type == kMessageTypeDecryptResponse)
    HandleDecryptResponseMessage(*message);
  else if (type == kMessageTypeUnlockResponse)
    HandleUnlockResponseMessage(*message);
  else
    NOTREACHED();  // There are no other message types that expect a response.

  pending_message_.reset();
  ProcessMessageQueue();
}

void MessengerImpl::HandleRemoteStatusUpdateMessage(
    const base::DictionaryValue& message) {
  std::unique_ptr<RemoteStatusUpdate> status_update =
      RemoteStatusUpdate::Deserialize(message);
  if (!status_update) {
    PA_LOG(ERROR) << "Unexpected remote status update: " << message;
    return;
  }

  FOR_EACH_OBSERVER(MessengerObserver, observers_,
                    OnRemoteStatusUpdate(*status_update));
}

void MessengerImpl::HandleDecryptResponseMessage(
    const base::DictionaryValue& message) {
  std::string base64_data;
  std::string decrypted_data;
  if (!message.GetString(kDataKey, &base64_data) || base64_data.empty()) {
    PA_LOG(ERROR) << "Decrypt response missing '" << kDataKey << "' value.";
  } else if (!base::Base64UrlDecode(
                 base64_data, base::Base64UrlDecodePolicy::REQUIRE_PADDING,
                 &decrypted_data)) {
    PA_LOG(ERROR) << "Unable to base64-decode decrypt response.";
  }

  FOR_EACH_OBSERVER(MessengerObserver, observers_,
                    OnDecryptResponse(decrypted_data));
}

void MessengerImpl::HandleUnlockResponseMessage(
    const base::DictionaryValue& message) {
  FOR_EACH_OBSERVER(MessengerObserver, observers_, OnUnlockResponse(true));
}

void MessengerImpl::PollScreenStateForIOS() {
  if (!connection_->IsConnected())
    return;

  // Sends message requesting screen state.
  queued_messages_.push_back(PendingMessage(std::string(kPollScreenState)));
  ProcessMessageQueue();

  // Schedules the next message in |kPollingIntervalSeconds|.
  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
      FROM_HERE, base::Bind(&MessengerImpl::PollScreenStateForIOS,
                            weak_ptr_factory_.GetWeakPtr()),
      base::TimeDelta::FromSeconds(kIOSPollingIntervalSeconds));
}

void MessengerImpl::OnConnectionStatusChanged(Connection* connection,
                                              Connection::Status old_status,
                                              Connection::Status new_status) {
  DCHECK_EQ(connection, connection_.get());
  if (new_status == Connection::DISCONNECTED) {
    PA_LOG(INFO) << "Secure channel disconnected...";
    connection_->RemoveObserver(this);
    FOR_EACH_OBSERVER(MessengerObserver, observers_, OnDisconnected());
    // TODO(isherman): Determine whether it's also necessary/appropriate to fire
    // this notification from the destructor.
  }
}

void MessengerImpl::OnMessageReceived(const Connection& connection,
                                      const WireMessage& wire_message) {
  secure_context_->Decode(wire_message.payload(),
                          base::Bind(&MessengerImpl::OnMessageDecoded,
                                     weak_ptr_factory_.GetWeakPtr()));
}

void MessengerImpl::OnSendCompleted(const Connection& connection,
                                    const WireMessage& wire_message,
                                    bool success) {
  if (!pending_message_) {
    PA_LOG(ERROR) << "Unexpected message sent.";
    return;
  }

  // In the common case, wait for a response from the remote device.
  // Don't wait if the message could not be sent, as there won't ever be a
  // response in that case. Likewise, don't wait for a response to local
  // event messages, as there is no response for such messages.
  if (success && pending_message_->type != kMessageTypeLocalEvent)
    return;

  // Notify observer of failure if sending the message fails.
  // For local events, we don't expect a response, so on success, we
  // notify observers right away.
  if (pending_message_->type == kMessageTypeDecryptRequest) {
    FOR_EACH_OBSERVER(MessengerObserver, observers_,
                      OnDecryptResponse(std::string()));
  } else if (pending_message_->type == kMessageTypeUnlockRequest) {
    FOR_EACH_OBSERVER(MessengerObserver, observers_, OnUnlockResponse(false));
  } else if (pending_message_->type == kMessageTypeLocalEvent) {
    FOR_EACH_OBSERVER(MessengerObserver, observers_,
                      OnUnlockEventSent(success));
  } else {
    PA_LOG(ERROR) << "Message of unknown type '" << pending_message_->type
                  << "' sent.";
  }

  pending_message_.reset();
  ProcessMessageQueue();
}

}  // namespace proximity_auth