cros: Implement cryptohome backend for pin.

chrome/browser/chromeos/login/quick_unlock/pin_storage.h

-// 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.
-
-#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_QUICK_UNLOCK_PIN_STORAGE_H_
-#define CHROME_BROWSER_CHROMEOS_LOGIN_QUICK_UNLOCK_PIN_STORAGE_H_
-
-#include <string>
-
-#include "base/gtest_prod_util.h"
-#include "base/time/time.h"
-
-class PrefRegistrySimple;
-class PrefService;
-
-namespace chromeos {
-
-class PinStorageTestApi;
-
-namespace quick_unlock {
-
-class QuickUnlockStorage;
-
-class PinStorage {
- public:
-  // TODO(sammiequon): Pull this value in from policy. See crbug.com/612271.
-  static const int kMaximumUnlockAttempts = 3;
-
-  // Registers profile prefs.
-  static void RegisterProfilePrefs(PrefRegistrySimple* registry);
-
-  explicit PinStorage(PrefService* pref_service);
-  ~PinStorage();
-
-  // Add a PIN unlock attempt count.
-  void AddUnlockAttempt();
-  // Reset the number of unlock attempts to 0.
-  void ResetUnlockAttemptCount();
-  // Returns the number of unlock attempts.
-  int unlock_attempt_count() const { return unlock_attempt_count_; }
-
-  // Returns true if a pin is set.
-  bool IsPinSet() const;
-  // Sets the pin to the given value; IsPinSet will return true.
-  void SetPin(const std::string& pin);
-  // Removes the pin; IsPinSet will return false.
-  void RemovePin();
-
- private:
-  friend class chromeos::PinStorageTestApi;
-  friend class QuickUnlockStorage;
-
-  // Is PIN entry currently available?
-  bool IsPinAuthenticationAvailable() const;
-
-  // Tries to authenticate the given pin. This will consume an unlock attempt.
-  // This always returns false if IsPinAuthenticationAvailable returns false.
-  bool TryAuthenticatePin(const std::string& pin);
-
-  // Return the stored salt/secret. This is fetched directly from pref_service_.
-  std::string PinSalt() const;
-  std::string PinSecret() const;
-
-  PrefService* pref_service_;
-  int unlock_attempt_count_ = 0;
-
-  DISALLOW_COPY_AND_ASSIGN(PinStorage);
-};
-
-}  // namespace quick_unlock
-}  // namespace chromeos
-
-#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_QUICK_UNLOCK_PIN_STORAGE_H_