[Sync] Add intelligent re-encryption support.

chrome/browser/sync/util/cryptographer_unittest.cc

 // Copyright (c) 2011 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 "chrome/browser/sync/util/cryptographer.h"
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/string_util.h"
@@ skipping 69 matching lines @@
 
   sync_pb::EncryptedData encrypted;
   EXPECT_TRUE(cryptographer.Encrypt(original, &encrypted));
 
   sync_pb::PasswordSpecificsData decrypted;
   EXPECT_TRUE(cryptographer.Decrypt(encrypted, &decrypted));
 
   EXPECT_EQ(original.SerializeAsString(), decrypted.SerializeAsString());
 }
 
+TEST(CryptographerTest, EncryptOnlyIfDifferent) {
+  Cryptographer cryptographer;
+
+  KeyParams params = {"localhost", "dummy", "dummy"};
+  EXPECT_TRUE(cryptographer.AddKey(params));
+  EXPECT_TRUE(cryptographer.is_ready());
+
+  sync_pb::PasswordSpecificsData original;
+  original.set_origin("http://example.com");
+  original.set_username_value("azure");
+  original.set_password_value("hunter2");
+
+  sync_pb::EncryptedData encrypted;
+  EXPECT_TRUE(cryptographer.Encrypt(original, &encrypted));
+
+  sync_pb::EncryptedData encrypted2, encrypted3;
+  encrypted2.CopyFrom(encrypted);
+  encrypted3.CopyFrom(encrypted);
+  EXPECT_TRUE(cryptographer.Encrypt(original, &encrypted2));
+
+  // Now encrypt with a new default key. Should overwrite the old data.
+  KeyParams params_new = {"localhost", "dummy", "dummy2"};
+  cryptographer.AddKey(params_new);
+  EXPECT_TRUE(cryptographer.Encrypt(original, &encrypted3));
+
+  sync_pb::PasswordSpecificsData decrypted;
+  EXPECT_TRUE(cryptographer.Decrypt(encrypted2, &decrypted));
+  // encrypted2 should match encrypted, encrypted3 should not (due to salting).
+  EXPECT_EQ(encrypted.SerializeAsString(), encrypted2.SerializeAsString());
+  EXPECT_NE(encrypted.SerializeAsString(), encrypted3.SerializeAsString());
+  EXPECT_EQ(original.SerializeAsString(), decrypted.SerializeAsString());
+}
+
 TEST(CryptographerTest, AddKeySetsDefault) {
   Cryptographer cryptographer;
 
   KeyParams params1 = {"localhost", "dummy", "dummy1"};
   EXPECT_TRUE(cryptographer.AddKey(params1));
   EXPECT_TRUE(cryptographer.is_ready());
 
   sync_pb::PasswordSpecificsData original;
   original.set_origin("http://example.com");
   original.set_username_value("azure");
@@ skipping 260 matching lines @@
         iter.Get() == syncable::BOOKMARKS)
       EXPECT_TRUE(encrypted_types.Has(iter.Get()));
     else
       EXPECT_FALSE(encrypted_types.Has(iter.Get()));
   }
 
   cryptographer.RemoveObserver(&observer);
 }
 
 }  // namespace browser_sync