u2fd/u2fhid.h

// Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef U2FD_U2FHID_H_
#define U2FD_U2FHID_H_

#include <memory>
#include <string>
#include <vector>

#include <base/timer/timer.h>
#include <brillo/errors/error.h>

#include "u2fd/hid_interface.h"

namespace u2f {

// U2fHid emulates U2FHID protocol on top of the TPM U2F implementation.
// The object reads the HID report sent by the HIDInterface passed to the
// constructor, parses it and extracts the U2FHID command. If this is a U2F
// message, finally sends the raw U2F APDU to the |transmit_func| callback
// passed to the constructor. It returns the final result (response APDU or
// error code) inside an HID report through the HIDInterface.
class U2fHid {
 public:
  // Callback to send the raw U2F APDU in |req| and get the corresponding
  // response APDU in |resp|.
  using TransmitApduCallback =
      base::Callback<int(const std::string& req, std::string* resp)>;
  // Callback to disable the power button for |in_timeout_internal| when using
  // it as physical presence for U2F.
  using IgnoreButtonCallback = base::Callback<bool(
      int64_t in_timeout_internal, brillo::ErrorPtr* error, int timeout)>;

  U2fHid(std::unique_ptr<HidInterface> hid,
         const TransmitApduCallback& transmit_func,
         const IgnoreButtonCallback& ignore_button_func);
  ~U2fHid();
  bool Init();

  // Retrieves the U2f implementation version available through the
  // |transmit_func| provided to the constructor.
  // Returns true on success.
  bool GetU2fVersion(std::string* version_out);

 private:
  enum class U2fHidCommand : uint8_t;
  enum class U2fHidError : uint8_t;

  // U2FHID protocol commands implementation.
  void CmdInit(uint32_t cid, const std::string& payload);
  int CmdLock(std::string* resp);
  int CmdMsg(std::string* resp);
  int CmdPing(std::string* resp);
  int CmdWink(std::string* resp);

  // Fully resets the state of the possibly on-going U2FHID transaction.
  void ClearTransaction();

  // Sends back a U2FHID report with just the |errcode| error code inside
  // on channel |cid|.
  // If |clear| is set, clear the transaction state at the same time.
  void ReturnError(U2fHidError errcode, uint32_t cid, bool clear);

  // Called when we reach the deadline for the on-going transaction.
  void TransactionTimeout();

  // Called when we reach the deadline for an unreleased channel lock.
  void LockTimeout();

  // Sends back a U2FHID report indicating success and carrying the response
  // payload |resp|.
  void ReturnResponse(const std::string& resp);

  // Parses the ISO7816-4:2005 U2F APDU contained in |payload| to guess
  // if it contains a user physical presence request and mask the power button
  // actions if it does.
  void ScanApdu(const std::string& payload);

  // Executes the action requested by the command contained in the current
  // transaction.
  void ExecuteCmd();

  // Parses the HID report contained in |report| and append the content to the
  // current U2FHID transaction or create a new one.
  void ProcessReport(const std::string& report);

  std::unique_ptr<HidInterface> hid_;
  TransmitApduCallback transmit_apdu_;
  IgnoreButtonCallback ignore_button_;
  uint32_t free_cid_;
  uint32_t locked_cid_;
  base::OneShotTimer lock_timeout_;

  class HidPacket;
  class HidMessage;
  struct Transaction;

  std::unique_ptr<Transaction> transaction_;

  DISALLOW_COPY_AND_ASSIGN(U2fHid);
};

}  // namespace u2f

#endif  // U2FD_U2FHID_H_