chrome/browser/prefs/pref_hash_store.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_BROWSER_PREFS_PREF_HASH_STORE_H_
   6 #define CHROME_BROWSER_PREFS_PREF_HASH_STORE_H_
   7
   8 #include <string>
   9
  10 #include "base/memory/scoped_ptr.h"
  11
  12 namespace base {
  13 class Value;
  14 }  // namespace base
  15
  16 namespace internals {
  17
  18 // Hash of hashes for each profile, used to validate the existing hashes when
  19 // debating whether an unknown value is to be trusted, will be stored as a
  20 // string under
  21 // |kProfilePreferenceHashes|.|kHashOfHashesPref|.|hash_stored_id_|.
  22 const char kHashOfHashesPref[] = "hash_of_hashes";
  23
  24 }  // namespace internals
  25
  26 // Stores hashes of and verifies preference values. To use, first call
  27 // |InitializeTrackedValue| with each preference that should be tracked. Then
  28 // call |OnPrefValueChanged| to update the hash store when preference values
  29 // change.
  30 class PrefHashStore {
  31  public:
  32   virtual ~PrefHashStore() {}
  33
  34   enum ValueState {
  35     // The preference value corresponds to its stored hash.
  36     UNCHANGED,
  37     // The preference has been cleared since the last hash.
  38     CLEARED,
  39     // The preference value corresponds to its stored hash, which was calculated
  40     // using a legacy hash algorithm.
  41     MIGRATED,
  42     // The preference value has been changed since the last hash.
  43     CHANGED,
  44     // No stored hash exists for the preference value.
  45     UNTRUSTED_UNKNOWN_VALUE,
  46     // No stored hash exists for the preference value, but the current set of
  47     // hashes stored is trusted and thus this value can safely be seeded. This
  48     // happens when all hashes are already properly seeded and a newly
  49     // tracked value needs to be seeded). NULL values are inherently trusted as
  50     // well.
  51     TRUSTED_UNKNOWN_VALUE,
  52   };
  53
  54   // Checks |initial_value| against the existing stored value hash.
  55   virtual ValueState CheckValue(
  56       const std::string& path, const base::Value* initial_value) const = 0;
  57
  58   // Stores a hash of the current |value| of the preference at |path|.
  59   virtual void StoreHash(const std::string& path,
  60                          const base::Value* value) = 0;
  61 };
  62
  63 #endif  // CHROME_BROWSER_PREFS_PREF_HASH_STORE_H_