sync: Introduce control data types

sync/engine/apply_control_data_updates.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 "sync/engine/apply_control_data_updates.h"
+
+#include "base/metrics/histogram.h"
+#include "sync/engine/conflict_resolver.h"
+#include "sync/engine/conflict_util.h"
+#include "sync/engine/syncer_util.h"
+#include "sync/syncable/directory.h"
+#include "sync/syncable/mutable_entry.h"
+#include "sync/syncable/nigori_util.h"
+#include "sync/syncable/write_transaction.h"
+#include "sync/util/cryptographer.h"
+
+namespace syncer {
+
+using syncable::GET_BY_SERVER_TAG;
+using syncable::IS_UNAPPLIED_UPDATE;
+using syncable::IS_UNSYNCED;
+using syncable::SERVER_SPECIFICS;
+using syncable::SPECIFICS;
+using syncable::SYNCER;
+
+void ApplyControlDataUpdates(syncable::Directory* dir) {
+  syncable::WriteTransaction trans(FROM_HERE, SYNCER, dir);
+
+  if (ApplyNigoriUpdates(&trans, dir->GetCryptographer(&trans))) {
+    dir->set_initial_sync_ended_for_type(NIGORI, true);
+  }
+}
+
+// Update the cryptographer with the server's nigori node.
+//
+// If we have a locally modified nigori node, we merge them manually. This
+// handles the case where two clients both set a different passphrase. The
+// second client to attempt to commit will go into a state of having pending
+// keys, unioned the set of encrypted types, and eventually re-encrypt
+// everything with the passphrase of the first client and commit the set of
+// merged encryption keys. Until the second client provides the pending
+// passphrase, the cryptographer will preserve the encryption keys based on the
+// local passphrase, while the nigori node will preserve the server encryption
+// keys.
+bool ApplyNigoriUpdates(syncable::WriteTransaction* trans,
+                        Cryptographer* cryptographer) {
+  syncable::MutableEntry nigori_node(trans, GET_BY_SERVER_TAG,
+                                     ModelTypeToRootTag(NIGORI));
+
+  // Mainly for unit tests.  We should have a Nigori node by this point.
+  if (!nigori_node.good()) {
+    return false;
+  }
+
+  if (!nigori_node.Get(IS_UNAPPLIED_UPDATE)) {
+    return true;
+  }
+
+  const sync_pb::NigoriSpecifics& nigori =
+      nigori_node.Get(SERVER_SPECIFICS).nigori();
+  cryptographer->ApplyNigoriUpdate(nigori, trans);
+
+  // Make sure any unsynced changes are properly encrypted as necessary.
+  // We only perform this if the cryptographer is ready. If not, these are
+  // re-encrypted at SetDecryptionPassphrase time (via ReEncryptEverything).
+  // This logic covers the case where the nigori update marked new datatypes
+  // for encryption, but didn't change the passphrase.
+  if (cryptographer->is_ready()) {
+    // Note that we don't bother to encrypt any data for which IS_UNSYNCED
+    // == false here. The machine that turned on encryption should know about
+    // and re-encrypt all synced data. It's possible it could get interrupted
+    // during this process, but we currently reencrypt everything at startup
+    // as well, so as soon as a client is restarted with this datatype marked
+    // for encryption, all the data should be updated as necessary.
+
+    // If this fails, something is wrong with the cryptographer, but there's
+    // nothing we can do about it here.
+    DVLOG(1) << "Received new nigori, encrypting unsynced changes.";
+    syncable::ProcessUnsyncedChangesForEncryption(trans, cryptographer);
+  }
+
+  if (!nigori_node.Get(IS_UNSYNCED)) { // Update only.
+    UpdateLocalDataFromServerData(trans, &nigori_node);
+  } else { // Conflict.
+    // Create a new set of specifics based on the server specifics (which
+    // preserves their encryption keys).
+    sync_pb::EntitySpecifics specifics = nigori_node.Get(SERVER_SPECIFICS);
+    sync_pb::NigoriSpecifics* server_nigori = specifics.mutable_nigori();
+    // Store the merged set of encrypted types (cryptographer->Update(..) will
+    // have merged the local types already).
+    cryptographer->UpdateNigoriFromEncryptedTypes(server_nigori, trans);
+    // The cryptographer has the both the local and remote encryption keys
+    // (added at cryptographer->Update(..) time).
+    // If the cryptographer is ready, then it already merged both sets of keys
+    // and we can store them back in. In that case, the remote key was already
+    // part of the local keybag, so we preserve the local key as the default
+    // (including whether it's an explicit key).
+    // If the cryptographer is not ready, then the user will have to provide
+    // the passphrase to decrypt the pending keys. When they do so, the
+    // SetDecryptionPassphrase code will act based on whether the server
+    // update has an explicit passphrase or not.
+    // - If the server had an explicit passphrase, that explicit passphrase
+    //   will be preserved as the default encryption key.
+    // - If the server did not have an explicit passphrase, we assume the
+    //   local passphrase is the most up to date and preserve the local
+    //   default encryption key marked as an implicit passphrase.
+    // This works fine except for the case where we had locally set an
+    // explicit passphrase. In that case the nigori node will have the default
+    // key based on the local explicit passphassphrase, but will not have it
+    // marked as explicit. To fix this we'd have to track whether we have a
+    // explicit passphrase or not separate from the nigori, which would
+    // introduce even more complexity, so we leave it up to the user to reset
+    // that passphrase as an explicit one via settings. The goal here is to
+    // ensure both sets of encryption keys are preserved.
+    if (cryptographer->is_ready()) {
+      cryptographer->GetKeys(server_nigori->mutable_encrypted());
+      server_nigori->set_using_explicit_passphrase(
+          nigori_node.Get(SPECIFICS).nigori().using_explicit_passphrase());
+    }
+    nigori_node.Put(SPECIFICS, specifics);
+    DVLOG(1) << "Resolving simple conflict, merging nigori nodes: "
+             << nigori_node;
+
+    OverwriteServerChanges(&nigori_node);
+
+    UMA_HISTOGRAM_ENUMERATION("Sync.ResolveSimpleConflict",
+                              ConflictResolver::NIGORI_MERGE,
+                              ConflictResolver::CONFLICT_RESOLUTION_SIZE);
+  }
+
+  return true;
+}
+
+}  // namespace syncer