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 "components/proximity_auth/logging/logging.h"
+
+using proximity_auth::BluetoothLowEnergyWeavePacketGenerator;
+
+namespace {
+typedef BluetoothLowEnergyWeavePacketGenerator::PacketType PacketType;
+typedef BluetoothLowEnergyWeavePacketGenerator::ControlCommand ControlCommand;
+typedef BluetoothLowEnergyWeavePacketGenerator::ReasonForClose ReasonForClose;
+
+const uint8_t kMaxPacketCounter = 8;
+const uint16_t kMaxControlPacketSize = 20;
+const uint16_t kMinMaxPacketSize = 20;
+const uint16_t kSelectDefaultPacketSize = 0;
+const uint16_t kMinConnectionRequestSize = 7;
+const uint16_t kMinConnectionResponseSize = 5;
+const uint16_t kMinConnectionCloseSize = 3;
+const uint16_t kSupportedWeaveVersion = 1;
+
+}  // namespace
+
+namespace proximity_auth {
+
+BluetoothLowEnergyWeavePacketReceiver::Factory*
+    BluetoothLowEnergyWeavePacketReceiver::Factory::factory_instance_ = nullptr;
+
+std::unique_ptr<BluetoothLowEnergyWeavePacketReceiver>
+BluetoothLowEnergyWeavePacketReceiver::Factory::NewInstance(
+    ReceiverType receiver_type) {
+  if (factory_instance_ == nullptr) {
+    factory_instance_ = new Factory();
+  }
+  return std::unique_ptr<BluetoothLowEnergyWeavePacketReceiver>(
+      factory_instance_->BuildInstance(receiver_type));
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::Factory::SetInstanceForTesting(
+    Factory* factory) {
+  factory_instance_ = factory;
+}
+
+BluetoothLowEnergyWeavePacketReceiver*
+BluetoothLowEnergyWeavePacketReceiver::Factory::BuildInstance(
+    ReceiverType receiver_type) {
+  return new BluetoothLowEnergyWeavePacketReceiver(receiver_type);
+}
+
+BluetoothLowEnergyWeavePacketReceiver::BluetoothLowEnergyWeavePacketReceiver(
+    ReceiverType receiver_type)
+    : receiver_type_(receiver_type),
+      next_packet_number_(0),
+      state_(State::CONNECTING),
+      reason_for_close_(ReasonForClose::CLOSE_WITHOUT_ERROR),
+      reason_to_close_(ReasonForClose::CLOSE_WITHOUT_ERROR) {
+  SetMaxPacketSize(kMinMaxPacketSize);
+}
+
+BluetoothLowEnergyWeavePacketReceiver::
+    ~BluetoothLowEnergyWeavePacketReceiver() {}
+
+BluetoothLowEnergyWeavePacketReceiver::State
+BluetoothLowEnergyWeavePacketReceiver::GetState() {
+  return state_;
+}
+
+uint16_t BluetoothLowEnergyWeavePacketReceiver::GetMaxPacketSize() {
+  // max_packet_size_ is well defined in every state.
+  return max_packet_size_;
+}
+
+ReasonForClose BluetoothLowEnergyWeavePacketReceiver::GetReasonForClose() {
+  DCHECK(state_ == State::CONNECTION_CLOSED);
+  return reason_for_close_;
+}
+
+ReasonForClose BluetoothLowEnergyWeavePacketReceiver::GetReasonToClose() {
+  DCHECK(state_ == State::ERROR);
+  return reason_to_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()) {
+    ThrowError(
+        "Received empty packet. "
+        "Empty packet is not a valid uWeave packet.",
+        ReasonForClose::UNKNOWN_ERROR);
+  } else if (packet.size() > GetConceptualMaxPacketSize()) {
+    ThrowError("Received packet with size " + std::to_string(packet.size()) +
+                   ", which is greater than maximum packet size" +
+                   std::to_string(GetConceptualMaxPacketSize()),
+               ReasonForClose::UNKNOWN_ERROR);
+  } else {
+    VerifyPacketCounter(packet);
+
+    switch (state_) {
+      case State::CONNECTING:
+        ReceiveFirstPacket(packet);
+        break;
+      case State::WAITING:
+        ReceiveNonFirstPacket(packet, true);
+        break;
+      case State::RECEIVING_DATA:
+        ReceiveNonFirstPacket(packet, false);
+        break;
+      case State::DATA_READY:
+        data_message_.clear();
+        ReceiveNonFirstPacket(packet, true);
+        break;
+      case State::CONNECTION_CLOSED:
+        ThrowError("Received message in ConnectionClosed state.",
+                   ReasonForClose::UNKNOWN_ERROR);
+        break;
+      case State::ERROR:
+        PA_LOG(ERROR) << "Received message in ERROR state.";
+        break;
+      default:
+        NOTREACHED();
+    }
+  }
+  return state_;
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveFirstPacket(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::CONNECTING);
+
+  if (GetPacketType(packet) != PacketType::CONTROL) {
+    ThrowError("Received data packets when not connected.",
+               ReasonForClose::UNKNOWN_ERROR);
+    return;
+  }
+
+  uint8_t command = GetControlCommand(packet);
+  switch (command) {
+    case ControlCommand::CONNECTION_REQUEST:
+      if (receiver_type_ == ReceiverType::SERVER) {
+        ReceiveConnectionRequest(packet);
+      } else {
+        ThrowError("Server received connection response instead of request.",
+                   ReasonForClose::UNKNOWN_ERROR);
+      }
+      break;
+    case ControlCommand::CONNECTION_RESPONSE:
+      if (receiver_type_ == ReceiverType::CLIENT) {
+        ReceiveConnectionResponse(packet);
+      } else {
+        ThrowError("Client received connection request instead of response.",
+                   ReasonForClose::UNKNOWN_ERROR);
+      }
+      break;
+    case ControlCommand::CONNECTION_CLOSE:
+      ThrowError("Received connection close when not even connected.",
+                 ReasonForClose::UNKNOWN_ERROR);
+      break;
+    default:
+      ThrowError("Received unrecognized control packet command " +
+                     std::to_string(command),
+                 ReasonForClose::UNKNOWN_ERROR);
+      break;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveNonFirstPacket(
+    const Packet& packet,
+    bool expect_first_packet) {
+  DCHECK(!packet.empty());
+  DCHECK(((state_ == State::WAITING || state_ == State::DATA_READY) &&
+          expect_first_packet) ||
+         (state_ == State::RECEIVING_DATA && !expect_first_packet));
+
+  uint8_t command;
+  switch (GetPacketType(packet)) {
+    case PacketType::CONTROL:
+      command = GetControlCommand(packet);
+      if (command == ControlCommand::CONNECTION_CLOSE) {
+        ReceiveConnectionClose(packet);
+      } else {
+        ThrowError("Received invalid command " + std::to_string(command) +
+                       " during data transaction",
+                   ReasonForClose::UNKNOWN_ERROR);
+      }
+      break;
+    case PacketType::DATA:
+      if (!AreLowerTwoBitsCleared(packet)) {
+        ThrowError(
+            "Lower two bits of data packet header are not clear as "
+            "expected.",
+            ReasonForClose::UNKNOWN_ERROR);
+      } else if (expect_first_packet != IsFirstDataPacket(packet)) {
+        // This means that expectation of whether a packet would be a
+        // first packet and what we actually got are different.
+        ThrowError("First bit of data packet is set incorrectly to " +
+                       std::to_string(IsFirstDataPacket(packet)),
+                   ReasonForClose::RECEIVED_PACKET_OUT_OF_SEQUENCE);
+      } else {
+        AppendData(packet, 1);
+        if (IsLastDataPacket(packet)) {
+          state_ = State::DATA_READY;
+        } else {
+          state_ = State::RECEIVING_DATA;
+        }
+      }
+      break;
+    default:
+      ThrowError("Received invalid packet type.",
+                 ReasonForClose::UNKNOWN_ERROR);
+      break;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveConnectionRequest(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::CONNECTING);
+
+  if (packet.size() < kMinConnectionRequestSize ||
+      packet.size() > kMaxControlPacketSize) {
+    ThrowError("Received invalid connection request packet size " +
+                   std::to_string(packet.size()),
+               ReasonForClose::UNKNOWN_ERROR);
+    return;
+  }
+
+  uint16_t packet_size = GetShortField(packet, 5);
+  // Packet size of 0 means the server can observe the ATT_MTU and select an
+  // appropriate packet size;
+  if (packet_size != kSelectDefaultPacketSize &&
+      packet_size < kMinMaxPacketSize) {
+    ThrowError("Received requested max packet size of " +
+                   std::to_string(packet_size) +
+                   ". Client must support at least " +
+                   std::to_string(kMinMaxPacketSize) + " bytes per packet.",
+               ReasonForClose::UNKNOWN_ERROR);
+    return;
+  }
+  SetMaxPacketSize(packet_size);
+
+  uint16_t min_version = GetShortField(packet, 1);
+  uint16_t max_version = GetShortField(packet, 3);
+  if (kSupportedWeaveVersion < min_version ||
+      kSupportedWeaveVersion > max_version) {
+    ThrowError("Server does not support client version range.",
+               ReasonForClose::NO_COMMON_VERSION_SUPPORTED);
+    return;
+  }
+
+  if (packet.size() > kMinConnectionRequestSize) {
+    AppendData(packet, kMinConnectionRequestSize);
+    state_ = State::DATA_READY;
+  } else {
+    state_ = State::WAITING;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveConnectionResponse(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  DCHECK(state_ == State::CONNECTING);
+
+  if (packet.size() < kMinConnectionResponseSize ||
+      packet.size() > kMaxControlPacketSize) {
+    ThrowError("Received invalid connection response packet size " +
+                   std::to_string(packet.size()),
+               ReasonForClose::UNKNOWN_ERROR);
+    return;
+  }
+
+  uint16_t selected_packet_size = GetShortField(packet, 3);
+  if (selected_packet_size < kMinMaxPacketSize) {
+    ThrowError("Received selected max packet size of " +
+                   std::to_string(selected_packet_size) +
+                   "Server must support at least " +
+                   std::to_string(kMinMaxPacketSize) + " bytes per packet.",
+               ReasonForClose::UNKNOWN_ERROR);
+    return;
+  }
+  SetMaxPacketSize(selected_packet_size);
+
+  uint16_t selected_version = GetShortField(packet, 1);
+  if (selected_version != kSupportedWeaveVersion) {
+    ThrowError("Client does not support server selected version.",
+               ReasonForClose::NO_COMMON_VERSION_SUPPORTED);
+    return;
+  }
+
+  if (packet.size() > kMinConnectionResponseSize) {
+    AppendData(packet, kMinConnectionResponseSize);
+    state_ = State::DATA_READY;
+  } else {
+    state_ = State::WAITING;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ReceiveConnectionClose(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+
+  if (packet.size() > kMaxControlPacketSize) {
+    ThrowError("Received invalid connection close packet size " +
+                   std::to_string(packet.size()),
+               ReasonForClose::UNKNOWN_ERROR);
+    return;
+  }
+
+  uint16_t reason;
+  if (packet.size() < kMinConnectionCloseSize) {
+    reason = ReasonForClose::UNKNOWN_ERROR;
+  } else {
+    reason = GetShortField(packet, 1);
+  }
+
+  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>(reason);
+      state_ = State::CONNECTION_CLOSED;
+      break;
+    default:
+      ThrowError("Received invalid reason for close " + std::to_string(reason),
+                 ReasonForClose::UNKNOWN_ERROR);
+      break;
+  }
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::AppendData(const Packet& packet,
+                                                       uint32_t byte_offset) {
+  DCHECK(!packet.empty());
+
+  // Append to data_message_ bytes 1 through end of the packet.
+  data_message_.insert(data_message_.end(), packet.begin() + byte_offset,
+                       packet.end());
+}
+
+uint16_t BluetoothLowEnergyWeavePacketReceiver::GetShortField(
+    const Packet& packet,
+    uint32_t byte_offset) {
+  DCHECK_LT(byte_offset, packet.size());
+  DCHECK_LT(byte_offset + 1, packet.size());
+
+  // packet[byte_offset + 1] is the upper byte and packet[byte_offset] is the
+  // lower byte.
+  return (packet[byte_offset + 1] << 8) | packet[byte_offset];
+}
+
+uint8_t BluetoothLowEnergyWeavePacketReceiver::GetPacketType(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  // Packet type is stored in the highest bit of the first byte.
+  return (packet[0] >> 7) & 1;
+}
+
+uint8_t BluetoothLowEnergyWeavePacketReceiver::GetControlCommand(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  // 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;
+
+  DCHECK(!packet.empty());
+  // Packet counter is bits 4, 5, and 6 of the first byte.
+  uint8_t count = (packet[0] >> 4) & 7;
+
+  if (count == (next_packet_number_ % kMaxPacketCounter)) {
+    next_packet_number_++;
+  } else {
+    ThrowError("Received invalid packet counter " + std::to_string(count),
+               ReasonForClose::RECEIVED_PACKET_OUT_OF_SEQUENCE);
+  }
+}
+
+bool BluetoothLowEnergyWeavePacketReceiver::IsFirstDataPacket(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  // Bit 3 determines whether the packet is the first packet of the message.
+  return (packet[0] >> 3) & 1;
+}
+
+bool BluetoothLowEnergyWeavePacketReceiver::IsLastDataPacket(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  // Bit 2 determines whether the packet is the last packet of the message.
+  return (packet[0] >> 2) & 1;
+}
+
+bool BluetoothLowEnergyWeavePacketReceiver::AreLowerTwoBitsCleared(
+    const Packet& packet) {
+  DCHECK(!packet.empty());
+  return (packet[0] & 3) == 0;
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::ThrowError(
+    std::string error_message,
+    ReasonForClose reason_to_close) {
+  PA_LOG(ERROR) << error_message;
+  state_ = State::ERROR;
+  reason_to_close_ = reason_to_close;
+}
+
+void BluetoothLowEnergyWeavePacketReceiver::SetMaxPacketSize(
+    uint16_t packet_size) {
+  DCHECK(packet_size == kSelectDefaultPacketSize ||
+         packet_size >= kMinMaxPacketSize);
+  max_packet_size_ = packet_size;
+}
+
+uint16_t BluetoothLowEnergyWeavePacketReceiver::GetConceptualMaxPacketSize() {
+  if (!max_packet_size_)
+    return 20;
+  return max_packet_size_;
+}
+
+}  // namespace proximity_auth