[sync] Fix decryption failure caused by missing user_key

components/sync/base/nigori.cc

 // Copyright (c) 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.
 
 #include "components/sync/base/nigori.h"
 
 #include <stdint.h>
 
 #include <sstream>
 #include <vector>
@@ skipping 61 matching lines @@
   // Suser = PBKDF2(Username || Servername, "saltsalt", Nsalt, 8)
   std::unique_ptr<SymmetricKey> user_salt(SymmetricKey::DeriveKeyFromPassword(
       SymmetricKey::HMAC_SHA1, salt_password.str(), kSaltSalt, kSaltIterations,
       kSaltKeySizeInBits));
   DCHECK(user_salt);
 
   std::string raw_user_salt;
   if (!user_salt->GetRawKey(&raw_user_salt))
     return false;
 
+  // Kuser = PBKDF2(P, Suser, Nuser, 16)
+  user_key_ = SymmetricKey::DeriveKeyFromPassword(
+      SymmetricKey::AES, password, raw_user_salt, kUserIterations,
+      kDerivedKeySizeInBits);

[pavely, 2017/04/10 21:27:29]

Could you keep DCHECK and return value check for InitByDerivation as it
generates nigori to be consumed by older clients. 

[Patrick Noland, 2017/04/10 23:43:06]

Done.

+
   // Kenc = PBKDF2(P, Suser, Nenc, 16)
   encryption_key_ = SymmetricKey::DeriveKeyFromPassword(
       SymmetricKey::AES, password, raw_user_salt, kEncryptionIterations,
       kDerivedKeySizeInBits);
   DCHECK(encryption_key_);
 
   // Kmac = PBKDF2(P, Suser, Nmac, 16)
   mac_key_ = SymmetricKey::DeriveKeyFromPassword(
       SymmetricKey::HMAC_SHA1, password, raw_user_salt, kSigningIterations,
       kDerivedKeySizeInBits);
   DCHECK(mac_key_);
 
   return encryption_key_ && mac_key_;
 }
 
-bool Nigori::InitByImport(const std::string& encryption_key,
+bool Nigori::InitByImport(const std::string& user_key,
+                          const std::string& encryption_key,
                           const std::string& mac_key) {
+  user_key_ = SymmetricKey::Import(SymmetricKey::AES, user_key);

[pavely, 2017/04/10 21:27:29]

Could you add a comment here or in nigori.h explaining that user_key_ is not
used anywhere, but since legacy clients check for it we should keep it around.

[Patrick Noland, 2017/04/10 23:43:06]

Done.

+
   encryption_key_ = SymmetricKey::Import(SymmetricKey::AES, encryption_key);
   DCHECK(encryption_key_);
 
   mac_key_ = SymmetricKey::Import(SymmetricKey::HMAC_SHA1, mac_key);
   DCHECK(mac_key_);
 
   return encryption_key_ && mac_key_;
 }
 
 // Permute[Kenc,Kmac](type || name)
@@ skipping 107 matching lines @@
   Encryptor encryptor;
   if (!encryptor.Init(encryption_key_.get(), Encryptor::CBC, iv))
     return false;
 
   if (!encryptor.Decrypt(ciphertext, value))
     return false;
 
   return true;
 }
 
-bool Nigori::ExportKeys(std::string* encryption_key,
+bool Nigori::ExportKeys(std::string* user_key,
+                        std::string* encryption_key,
                         std::string* mac_key) const {
   DCHECK(encryption_key);
   DCHECK(mac_key);
 
+  user_key_->GetRawKey(user_key);
+
   return encryption_key_->GetRawKey(encryption_key) &&
          mac_key_->GetRawKey(mac_key);
 }
 
 }  // namespace syncer