[sync] Fix decryption failure caused by missing user_key

components/sync/base/nigori.h

 // Copyright 2012 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 COMPONENTS_SYNC_BASE_NIGORI_H_
 #define COMPONENTS_SYNC_BASE_NIGORI_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 23 matching lines @@
   Nigori();
   virtual ~Nigori();
 
   // Initialize the client with the given |hostname|, |username| and |password|.
   bool InitByDerivation(const std::string& hostname,
                         const std::string& username,
                         const std::string& password);
 
   // Initialize the client by importing the given keys instead of deriving new
   // ones.
-  bool InitByImport(const std::string& encryption_key,
+  bool InitByImport(const std::string& user_key,
+                    const std::string& encryption_key,
                     const std::string& mac_key);
 
   // Derives a secure lookup name from |type| and |name|. If |hostname|,
   // |username| and |password| are kept constant, a given |type| and |name| pair
   // always yields the same |permuted| value. Note that |permuted| will be
   // Base64 encoded.
   bool Permute(Type type, const std::string& name, std::string* permuted) const;
 
   // Encrypts |value|. Note that on success, |encrypted| will be Base64
   // encoded.
   bool Encrypt(const std::string& value, std::string* encrypted) const;
 
   // Decrypts |value| into |decrypted|. It is assumed that |value| is Base64
   // encoded.
   bool Decrypt(const std::string& value, std::string* decrypted) const;
 
   // Exports the raw derived keys.
-  bool ExportKeys(std::string* encryption_key, std::string* mac_key) const;
+  bool ExportKeys(std::string* user_key,
+                  std::string* encryption_key,
+                  std::string* mac_key) const;
 
   static const char kSaltSalt[];  // The salt used to derive the user salt.
   static const size_t kSaltKeySizeInBits = 128;
   static const size_t kDerivedKeySizeInBits = 128;
   static const size_t kIvSize = 16;
   static const size_t kHashSize = 32;
 
   static const size_t kSaltIterations = 1001;
+  static const size_t kUserIterations = 1002;
   static const size_t kEncryptionIterations = 1003;
   static const size_t kSigningIterations = 1004;
 
  private:
+  // user_key isn't used any more, but legacy clients will fail to import a
+  // nigori node without one. We preserve it for the sake of those clients, but
+  // it should be removed once enough clients have upgraded to code that doesn't
+  // enforce its presence.
+  std::unique_ptr<crypto::SymmetricKey> user_key_;
   std::unique_ptr<crypto::SymmetricKey> encryption_key_;
   std::unique_ptr<crypto::SymmetricKey> mac_key_;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_BASE_NIGORI_H_