Weave Packet Receiver

components/proximity_auth/ble/bluetooth_low_energy_weave_packet_receiver.cc

+// Copyright 2016 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/ble/bluetooth_low_energy_weave_packet_receiver.h"
+
+#include "base/logging.h"
+
+using proximity_auth::BluetoothLowEnergyWeavePacketGenerator;
+
+namespace {
+typedef BluetoothLowEnergyWeavePacketGenerator::PacketType PacketType;
+typedef BluetoothLowEnergyWeavePacketGenerator::ControlCommand ControlCommand;
+typedef BluetoothLowEnergyWeavePacketGenerator::ReasonForClose ReasonForClose;
+
+const uint8_t kMaxPacketCounter = 8;
+}  // namespace
+
+namespace proximity_auth {
+
+BluetoothLowEnergyWeavePacketReceiver::Factory*
+    BluetoothLowEnergyWeavePacketReceiver::Factory::factory_instance_ = nullptr;
+
+std::unique_ptr<BluetoothLowEnergyWeavePacketReceiver>
+BluetoothLowEnergyWeavePacketReceiver::Factory::NewInstance() {
+  if (factory_instance_ == nullptr) {
+    factory_instance_ = new Factory();
+  }
+  return std::unique_ptr<BluetoothLowEnergyWeavePacketReceiver>(
+      factory_instance_->BuildInstance());
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::Factory::SetInstanceForTesting(
+    Factory* factory) {
+  factory_instance_ = factory;
+}
+
+BluetoothLowEnergyWeavePacketReceiver*
+BluetoothLowEnergyWeavePacketReceiver::Factory::BuildInstance() {
+  return new BluetoothLowEnergyWeavePacketReceiver();
+}
+
+BluetoothLowEnergyWeavePacketReceiver::BluetoothLowEnergyWeavePacketReceiver()
+    : packet_size_(0),
+      packet_number_(0),
+      state_(State::CONNECTING),
+      reason_for_close_(ReasonForClose::CLOSE_WITHOUT_ERROR) {}
+
+BluetoothLowEnergyWeavePacketReceiver::
+    ~BluetoothLowEnergyWeavePacketReceiver() {}
+
+BluetoothLowEnergyWeavePacketReceiver::State
+BluetoothLowEnergyWeavePacketReceiver::GetState() {
+  return state_;
+}
+
+uint32_t BluetoothLowEnergyWeavePacketReceiver::GetPacketSize() {
+  // packet_size_ is well defined in every state.
+  return packet_size_;
+}
+
+ReasonForClose BluetoothLowEnergyWeavePacketReceiver::GetReasonForClose() {
+  DCHECK(state_ == State::CONNECTION_CLOSED);
+  return reason_for_close_;
+}
+
+std::string BluetoothLowEnergyWeavePacketReceiver::GetDataMessage() {
+  DCHECK(state_ == State::DATA_READY);
+  return std::string(data_message_.begin(), data_message_.end());
+}
+
+BluetoothLowEnergyWeavePacketReceiver::State
+BluetoothLowEnergyWeavePacketReceiver::ReceivePacket(const Packet& packet) {
+  if (packet.empty()) {
+    DLOG(ERROR) << "Empty packet is not a valid uWeave packet.";
+    state_ = State::ERROR;
+  } else {
+    VerifyPacketCounter(packet);
+
+    switch (state_) {
+      case State::CONNECTING:
+        ReceiveControlPacket(packet);
+        break;
+      case State::RECEIVING_DATA:
+        ReceiveDataPacket(packet);
+        break;
+      case State::DATA_READY:
+        data_message_.clear();
+        ReceiveDataPacket(packet);
+        break;
+      default:
+        // Receiving an message in connection close or error state is not valid.
+        DLOG(ERROR) << "Receiving message in " << state_
+                    << " state is not valid.";
+        state_ = State::ERROR;
+        break;
+    }
+  }
+  return state_;
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveControlPacket(

[Tim Song, 2016/06/11 00:39:46]

This should probably be called ReceiveConnectionPacket(). It shouldn't be valid
to receive a CONNECTION_CLOSE control in this state.

[jingxuy, 2016/06/16 08:42:28]

Done.

+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::CONNECTING);
+
+  if (GetPacketType(packet) == PacketType::CONTROL) {
+    uint8_t command = GetControlCommand(packet);
+    switch (command) {
+      case ControlCommand::CONNECTION_REQUEST:
+        ReceiveConnectionRequest(packet);
+        break;
+      case ControlCommand::CONNECTION_RESPONSE:
+        ReceiveConnectionResponse(packet);
+        break;
+      case ControlCommand::CONNECTION_CLOSE:
+        ReceiveConnectionClose(packet);
+        break;
+      default:
+        DLOG(ERROR) << "Unrecognized control packet command " << command;
+        state_ = State::ERROR;
+        break;
+    }
+  } else {
+    DLOG(ERROR) << "Can't receive data packets when not connected.";
+    state_ = State::ERROR;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveDataPacket(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::RECEIVING_DATA);

[Tim Song, 2016/06/11 00:39:46]

Also check if state_ == State::DATA_READY

[jingxuy, 2016/06/16 08:42:28]

Done.

+
+  switch (GetPacketType(packet)) {
+    case PacketType::CONTROL:
+      if (GetControlCommand(packet) == ControlCommand::CONNECTION_CLOSE) {
+        ReceiveConnectionClose(packet);
+      } else {
+        DLOG(ERROR) << "Can't receive request/response during data "
+                    << "transaction.";
+        state_ = State::ERROR;
+      }
+      break;
+    case PacketType::DATA:
+      // Either it's a first packet and data_message_ is empty,
+      // or it's not a first packet and data_message_ is not empty.
+      if (IsFirstDataPacket(packet) ^ !data_message_.empty()) {
+        AppendData(packet);
+        if (IsLastDataPacket(packet)) {
+          state_ = State::DATA_READY;
+        }
+      } else {
+        DLOG(ERROR) << "First bit of data packet is not set correctly.";
+        state_ = State::ERROR;
+      }
+      break;
+    default:
+      DLOG(ERROR) << "Invalid packet type.";
+      state_ = State::ERROR;
+      break;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveConnectionRequest(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::CONNECTING);
+
+  uint16_t min_version = GetShortField(packet, 1);
+  uint16_t max_version = GetShortField(packet, 3);

[Tim Song, 2016/06/11 00:39:46]

You should validate that the packet is sufficiently long.

[sacomoto, 2016/06/13 17:16:40]

+1. 

And you should move the error state if that's not the case. 

[jingxuy, 2016/06/16 08:42:28]

Done.

+  if (!(min_version == 1 && max_version == 1)) {

[sacomoto, 2016/06/13 17:16:40]

This is not correct. 

As long as, min_version <= 1 <= max_version, you are fine. The version should
only contain your supported version.

[jingxuy, 2016/06/16 08:42:28]

Done.

+    state_ = State::ERROR;
+  } else {
+    packet_size_ = GetShortField(packet, 5);
+    state_ = State::RECEIVING_DATA;
+    // TODO(jingxuy): what do I do with the 13 bytes of data?

[sacomoto, 2016/06/13 17:16:40]

If there is any data in the connection request payload, you should store it
|data_message_| and move to State::DATA_READY, the owner of this class should
then report that as the first received message. 

[jingxuy, 2016/06/16 08:42:28]

Done.

+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveConnectionResponse(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::CONNECTING);
+
+  uint16_t selected_version = GetShortField(packet, 1);
+  if (selected_version != 1) {
+    state_ = State::ERROR;
+  } else {
+    packet_size_ = GetShortField(packet, 3);

[Tim Song, 2016/06/11 00:39:46]

You should validate that the packet is sufficiently long.

[sacomoto, 2016/06/13 17:16:40]

+1. 

And you should move the error state if that's not the case. 

[jingxuy, 2016/06/16 08:42:28]

Done.

+    state_ = State::RECEIVING_DATA;
+    // TODO(jingxuy): what do I do with the 15 bytes of data?

[sacomoto, 2016/06/13 17:16:40]

If there is any data in the connection response payload, you should store it
|data_message_| and move to State::DATA_READY, the owner of this class should
then report that as the first received message. 

[jingxuy, 2016/06/16 08:42:28]

Done.

+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveConnectionClose(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+
+  uint16_t reason = GetShortField(packet, 1);

[sacomoto, 2016/06/13 17:16:40]

Check if the packet is large enough.

[jingxuy, 2016/06/16 08:42:28]

Done.

+
+  switch (reason) {
+    case ReasonForClose::CLOSE_WITHOUT_ERROR:
+    case ReasonForClose::UNKNOWN_ERROR:
+    case ReasonForClose::NO_COMMON_VERSION_SUPPORTED:
+    case ReasonForClose::RECEIVED_PACKET_OUT_OF_SEQUENCE:
+    case ReasonForClose::APPLICATION_ERROR:
+      reason_for_close_ = static_cast<ReasonForClose>(GetShortField(packet, 1));

[sacomoto, 2016/06/13 17:16:40]

Check if the packet is large enough. 

But you should also accept the cases where the connection close packet contains
no payload, as this the case for the current implementations.  Consider and
UNKNOWN_ERROR in this case.

[jingxuy, 2016/06/16 08:42:28]

I don't really understand the comment. Should I not jump to State::ERROR upon
receiving a short close packet? Should I invent the error as UNKNOWN_ERROR?

[sacomoto, 2016/06/17 15:31:07]

I was referring to the current iOS and Android implementations that do not
include the reason for close in the payload. The connection close in those cases
will only contain a single byte. 

[jingxuy, 2016/06/17 18:59:51]

Done.

+      state_ = State::CONNECTION_CLOSED;
+      break;
+    default:
+      DLOG(ERROR) << "Invalid reason for close " << reason << ".";
+      state_ = State::ERROR;
+      break;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::AppendData(const Packet& packet) {
+  DCHECK(!packet.empty());
+
+  // Append to data_message_ bytes 1 through end of the packet.
+  data_message_.insert(data_message_.end(), packet.begin() + 1, packet.end());
+}
+
+uint16_t BluetoothLowEnergyWeavePacketReceiver::GetShortField(
+    const Packet& packet,
+    uint32_t index) {
+  DCHECK_LT(index, packet.size());
+  DCHECK_LT(index + 1, packet.size());
+
+  // packet[index + 1] is the upper byte and packet[index] is the lower byte.
+  return (packet[index + 1] << 8) | packet[index];
+}
+
+uint8_t BluetoothLowEnergyWeavePacketReceiver::GetPacketType(
+    const Packet& packet) {
+  // Packet type is stored in the highest bit of the first byte.
+  return (packet[0] >> 7) & 1;
+}
+
+uint8_t BluetoothLowEnergyWeavePacketReceiver::GetControlCommand(
+    const Packet& packet) {
+  // Control command is stored in the lower 4 bits of the first byte.
+  return packet[0] & 0x0F;
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::VerifyPacketCounter(
+    const Packet& packet) {
+  if (state_ == State::ERROR)
+    return;
+
+  // Packet counter is bits 4, 5, and 6 of the first byte.
+  uint8_t count = (packet[0] >> 4) & 7;
+
+  if (count == (packet_number_ % kMaxPacketCounter)) {
+    packet_number_++;
+  } else {
+    DLOG(ERROR) << "Invalid packet counter " << count << ".";
+    state_ = State::ERROR;
+  }
+}
+
+bool BluetoothLowEnergyWeavePacketReceiver::IsFirstDataPacket(
+    const Packet& packet) {
+  // Bit 3 determines whether the packet is the first packet of the message.
+  return (packet[0] >> 3) & 1;
+}
+
+bool BluetoothLowEnergyWeavePacketReceiver::IsLastDataPacket(
+    const Packet& packet) {
+  // Bit 2 determines whether the packet is the last packet of the message.
+  return (packet[0] >> 2) & 1;
+}
+
+}  // namespace proximity_auth