Implement KeepAlive logic for CTAP HID device

CTAP HID transport specification adds KEEP_ALIVE command. Add logic for
handling keep alive messages. That is, message from HID device should be
re-read after 100 milliseconds.

Change-Id: Iecb002f141d1a57f5753d25d728a5f1d851323db
Reviewed-on: https://chromium-review.googlesource.com/947193
Commit-Queue: Jun Choi <hongjunchoi@chromium.org>
Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548626}

device/fido/fake_hid_impl_for_testing.cc

@@ -6,10 +6,19 @@
 
 #include <utility>
 
-#include "base/optional.h"
+#include "device/fido/u2f_parsing_utils.h"
 
 namespace device {
 
+namespace {
+
+MATCHER_P(IsCtapHidCommand, expected_command, "") {
+  return arg.size() >= 5 &&
+         arg[4] == (0x80 | static_cast<uint8_t>(expected_command));
+}
+
+}  // namespace
+
 MockHidConnection::MockHidConnection(
     device::mojom::HidDeviceInfoPtr device,
     device::mojom::HidConnectionRequest request,
@@ -45,6 +54,31 @@ void MockHidConnection::SetNonce(base::span<uint8_t const> nonce) {
   nonce_ = std::vector<uint8_t>(nonce.begin(), nonce.end());
 }
 
+void MockHidConnection::ExpectWriteHidInit() {
+  EXPECT_CALL(*this, WritePtr(::testing::_,
+                              IsCtapHidCommand(FidoHidDeviceCommand::kInit),
+                              ::testing::_))
+      .WillOnce(::testing::Invoke(
+          [&](auto&&, const std::vector<uint8_t>& buffer,
+              device::mojom::HidConnection::WriteCallback* cb) {
+            ASSERT_EQ(64u, buffer.size());
+            // First 7 bytes are 4 bytes of channel id, one byte representing
+            // HID command, 2 bytes for payload length.
+            SetNonce(base::make_span(buffer).subspan(7, 8));
+            std::move(*cb).Run(true);
+          }));
+}
+
+void MockHidConnection::ExpectHidWriteWithCommand(FidoHidDeviceCommand cmd) {
+  EXPECT_CALL(*this,
+              WritePtr(::testing::_, IsCtapHidCommand(cmd), ::testing::_))
+      .WillOnce(::testing::Invoke(
+          [&](auto&&, const std::vector<uint8_t>& buffer,
+              device::mojom::HidConnection::WriteCallback* cb) {
+            std::move(*cb).Run(true);
+          }));
+}
+
 bool FakeHidConnection::mock_connection_error_ = false;
 
 FakeHidConnection::FakeHidConnection(device::mojom::HidDeviceInfoPtr device)

device/fido/fake_hid_impl_for_testing.h

@@ -13,6 +13,7 @@
 #include "base/containers/span.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "device/fido/fido_constants.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "mojo/public/cpp/bindings/interface_ptr_set.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
@@ -47,6 +48,9 @@ class MockHidConnection : public device::mojom::HidConnection {
                          SendFeatureReportCallback callback) override;
   void SetNonce(base::span<uint8_t const> nonce);
 
+  void ExpectWriteHidInit();
+  void ExpectHidWriteWithCommand(FidoHidDeviceCommand cmd);
+
   const std::vector<uint8_t>& connection_channel_id() const {
     return connection_channel_id_;
   }

device/fido/fido_ble_device.h

@@ -69,7 +69,6 @@ class COMPONENT_EXPORT(DEVICE_FIDO) FidoBleDevice : public FidoDevice {
   void StopTimeout();
   void OnTimeout();
 
-  State state_ = State::kInit;
   base::OneShotTimer timer_;
 
   std::unique_ptr<FidoBleConnection> connection_;

device/fido/fido_constants.cc

@@ -51,6 +51,8 @@ const std::array<uint8_t, 6> kU2fVersionResponse = {'U', '2', 'F',
                                                     '_', 'V', '2'};
 
 const base::TimeDelta kDeviceTimeout = base::TimeDelta::FromSeconds(3);
+const base::TimeDelta kHidKeepAliveDelay =
+    base::TimeDelta::FromMilliseconds(100);
 
 const char kFormatKey[] = "fmt";
 const char kAttestationStatementKey[] = "attStmt";

device/fido/fido_constants.h

@@ -260,6 +260,11 @@ extern const std::array<uint8_t, 6> kU2fVersionResponse;
 // Maximum wait time before client error outs on device.
 COMPONENT_EXPORT(DEVICE_FIDO) extern const base::TimeDelta kDeviceTimeout;
 
+// Interval wait time before retrying reading on HID connection when
+// CTAPHID_KEEPALIVE message has been received.
+// https://fidoalliance.org/specs/fido-v2.0-rd-20170927/fido-client-to-authenticator-protocol-v2.0-rd-20170927.html#ctaphid_keepalive-0x3b
+COMPONENT_EXPORT(DEVICE_FIDO) extern const base::TimeDelta kHidKeepAliveDelay;
+
 // String key values for attestation object as a response to MakeCredential
 // request.
 COMPONENT_EXPORT(DEVICE_FIDO) extern const char kFormatKey[];

device/fido/fido_hid_device.cc

@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
+#include "base/logging.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "crypto/random.h"
 #include "device/fido/fido_hid_message.h"
@@ -26,7 +27,6 @@ static constexpr uint8_t kReportId = 0x00;
 FidoHidDevice::FidoHidDevice(device::mojom::HidDeviceInfoPtr device_info,
                              device::mojom::HidManager* hid_manager)
     : FidoDevice(),
-      state_(State::kInit),
       hid_manager_(hid_manager),
       device_info_(std::move(device_info)),
       weak_factory_(this) {}
@@ -61,9 +61,11 @@ void FidoHidDevice::Transition(std::vector<uint8_t> command,
       state_ = State::kBusy;
       ArmTimeout(repeating_callback);
       // Write message to the device.
+      const auto command_type = supported_protocol() == ProtocolVersion::kCtap
+                                    ? FidoHidDeviceCommand::kCbor
+                                    : FidoHidDeviceCommand::kMsg;
       WriteMessage(
-          FidoHidMessage::Create(channel_id_, FidoHidDeviceCommand::kMsg,
-                                 std::move(command)),
+          FidoHidMessage::Create(channel_id_, command_type, std::move(command)),
           true,
           base::BindOnce(&FidoHidDevice::MessageReceived,
                          weak_factory_.GetWeakPtr(), repeating_callback));
@@ -273,13 +275,34 @@ void FidoHidDevice::MessageReceived(DeviceCallback callback,
                                     std::unique_ptr<FidoHidMessage> message) {
   if (state_ == State::kDeviceError)
     return;
+
   timeout_callback_.Cancel();
-  if (!success) {
+  if (!success || !message) {
     state_ = State::kDeviceError;
     Transition(std::vector<uint8_t>(), std::move(callback));
     return;
   }
 
+  const auto cmd = message->cmd();
+  // If received HID packet has keep_alive as command type, re-read after delay.
+  if (supported_protocol() == ProtocolVersion::kCtap &&
+      cmd == FidoHidDeviceCommand::kKeepAlive) {
+    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+        FROM_HERE,
+        base::BindOnce(&FidoHidDevice::OnKeepAlive, weak_factory_.GetWeakPtr(),
+                       std::move(callback)),
+        kHidKeepAliveDelay);
+    return;
+  }
+
+  if (cmd != FidoHidDeviceCommand::kMsg && cmd != FidoHidDeviceCommand::kCbor) {
+    DLOG(ERROR) << "Unexpected HID device command received.";
+    state_ = State::kDeviceError;
+    Transition(std::vector<uint8_t>(), std::move(callback));
+    return;
+  }
+
+  auto response = message->GetMessagePayload();
   state_ = State::kReady;
   base::WeakPtr<FidoHidDevice> self = weak_factory_.GetWeakPtr();
   std::move(callback).Run(
@@ -310,6 +333,15 @@ void FidoHidDevice::TryWink(WinkCallback callback) {
                               weak_factory_.GetWeakPtr(), std::move(callback)));
 }
 
+void FidoHidDevice::OnKeepAlive(DeviceCallback callback) {
+  auto repeating_callback =
+      base::AdaptCallbackForRepeating(std::move(callback));
+  ArmTimeout(repeating_callback);
+  ReadMessage(base::BindOnce(&FidoHidDevice::MessageReceived,
+                             weak_factory_.GetWeakPtr(),
+                             std::move(repeating_callback)));
+}
+
 void FidoHidDevice::OnWink(WinkCallback callback,
                            bool success,
                            std::unique_ptr<FidoHidMessage> response) {

device/fido/fido_hid_device.h

@@ -92,16 +92,17 @@ class COMPONENT_EXPORT(DEVICE_FIDO) FidoHidDevice : public FidoDevice {
                           bool success,
                           uint8_t report_id,
                           const base::Optional<std::vector<uint8_t>>& buf);
+  void OnKeepAlive(DeviceCallback callback);
   void OnWink(WinkCallback callback,
               bool success,
               std::unique_ptr<FidoHidMessage> response);
   void ArmTimeout(DeviceCallback callback);
   void OnTimeout(DeviceCallback callback);
+
   base::WeakPtr<FidoDevice> GetWeakPtr() override;
 
   uint32_t channel_id_ = kBroadcastChannel;
   uint8_t capabilities_ = 0;
-  State state_ = State::kInit;
 
   base::CancelableOnceClosure timeout_callback_;
   std::queue<std::pair<std::vector<uint8_t>, DeviceCallback>>

device/fido/fido_request_handler_base.cc

@@ -52,6 +52,10 @@ void FidoRequestHandlerBase::DiscoveryStarted(FidoDiscovery* discovery,
 void FidoRequestHandlerBase::DeviceAdded(FidoDiscovery* discovery,
                                          FidoDevice* device) {
   DCHECK(!base::ContainsKey(ongoing_tasks(), device->GetId()));
+  // All devices are initially assumed to support CTAP protocol and thus
+  // AuthenticatorGetInfo command is sent to all connected devices. If device
+  // errors out, then it is assumed to support U2F protocol.
+  device->set_supported_protocol(ProtocolVersion::kCtap);
   ongoing_tasks_.emplace(device->GetId(), CreateTaskForNewDevice(device));
 }