chrome/browser/prefs/pref_hash_store_transaction.h

// Copyright 2014 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_PREFS_PREF_HASH_STORE_TRANSACTION_H_
#define CHROME_BROWSER_PREFS_PREF_HASH_STORE_TRANSACTION_H_

#include <string>
#include <vector>

namespace base {
class DictionaryValue;
class Value;
}  // namespace base

// Used to perform a series of checks/transformations on a PrefHashStore.
class PrefHashStoreTransaction {
 public:
  enum ValueState {
    // The preference value corresponds to its stored hash.
    UNCHANGED,
    // The preference has been cleared since the last hash.
    CLEARED,
    // The preference value corresponds to its stored hash, which was calculated
    // using a deprecated hash algorithm which isn't as safe as the current one.
    WEAK_LEGACY,
    // The preference value corresponds to its stored hash, but the hash was
    // calculated using a deprecated hash algorithm which is just as safe as
    // the current one.
    SECURE_LEGACY,
    // The preference value has been changed since the last hash.
    CHANGED,
    // No stored hash exists for the preference value.
    UNTRUSTED_UNKNOWN_VALUE,
    // No stored hash exists for the preference value, but the current set of
    // hashes stored is trusted and thus this value can safely be seeded. This
    // happens when all hashes are already properly seeded and a newly
    // tracked value needs to be seeded). NULL values are inherently trusted as
    // well.
    TRUSTED_UNKNOWN_VALUE,
  };

  // Finalizes any remaining work after the transaction has been performed.
  virtual ~PrefHashStoreTransaction() {}

  // Checks |initial_value| against the existing stored value hash.
  virtual ValueState CheckValue(
      const std::string& path, const base::Value* initial_value) const = 0;

  // Stores a hash of the current |value| of the preference at |path|.
  virtual void StoreHash(const std::string& path,
                         const base::Value* value) = 0;

  // Checks |initial_value| against the existing stored hashes for the split
  // preference at |path|. |initial_split_value| being an empty dictionary or
  // NULL is equivalent. |invalid_keys| must initially be empty. |invalid_keys|
  // will not be modified unless the return value is CHANGED, in which case it
  // will be filled with the keys that are considered invalid (unknown or
  // changed).
  virtual ValueState CheckSplitValue(
      const std::string& path,
      const base::DictionaryValue* initial_split_value,
      std::vector<std::string>* invalid_keys) const = 0;

  // Stores hashes for the |value| of the split preference at |path|.
  // |split_value| being an empty dictionary or NULL is equivalent.
  virtual void StoreSplitHash(
      const std::string& path,
      const base::DictionaryValue* split_value) = 0;

  // Indicates whether the store contains a hash for the preference at |path|.
  virtual bool HasHash(const std::string& path) const = 0;

  // Sets the hash for the preference at |path|.
  // If |path| is a split preference |hash| must be a DictionaryValue whose
  // keys are keys in the split preference and whose values are MACs of the
  // corresponding values in the split preference.
  // If |path| is an atomic preference |hash| must be a StringValue
  // containing a MAC of the preference value.
  // |hash| should originate from a PrefHashStore sharing the same MAC
  // parameters as this transaction's store.
  // The (in)validity of the super MAC will be maintained by this call.
  virtual void ImportHash(const std::string& path, const base::Value* hash) = 0;

  // Removes the hash stored at |path|. The (in)validity of the super MAC will
  // be maintained by this call.
  virtual void ClearHash(const std::string& path) = 0;

  // Indicates whether the super MAC was successfully verified at the beginning
  // of this transaction.
  virtual bool IsSuperMACValid() const = 0;

  // Forces a valid super MAC to be stored when this transaction terminates.
  // Returns true if this results in a change to the store contents.
  virtual bool StampSuperMac() = 0;
};

#endif  // CHROME_BROWSER_PREFS_PREF_HASH_STORE_TRANSACTION_H_