[Sync] Add SyncEncryptionHandler

sync/internal_api/public/sync_encryption_handler.h

+// 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.
+
+#ifndef SYNC_INTERNAL_API_PUBLIC_SYNC_ENCRYPTION_HANDLER_H_
+#define SYNC_INTERNAL_API_PUBLIC_SYNC_ENCRYPTION_HANDLER_H_
+
+#include <string>
+
+#include "sync/internal_api/public/base/model_type.h"
+
+namespace sync_pb {
+class EncryptedData;
+}
+
+namespace syncer {
+
+class Cryptographer;
+
+// Reasons due to which Cryptographer might require a passphrase.
+enum PassphraseRequiredReason {
+  REASON_PASSPHRASE_NOT_REQUIRED = 0,  // Initial value.
+  REASON_ENCRYPTION = 1,               // The cryptographer requires a
+                                       // passphrase for its first attempt at
+                                       // encryption. Happens only during
+                                       // migration or upgrade.
+  REASON_DECRYPTION = 2,               // The cryptographer requires a
+                                       // passphrase for its first attempt at
+                                       // decryption.
+};
+
+// Sync's encryption handler. Handles tracking encrypted types, ensuring the
+// cryptographer encrypts with the proper key and has the most recent keybag,
+// and keeps the nigori node up to date.
+class SyncEncryptionHandler {
+ public:
+  // All Observer methods are done synchronously from within a transaction and
+  // on the sync thread.
+  class Observer {
+   public:
+    Observer();
+
+    // Called when user interaction is required to obtain a valid passphrase.
+    // - If the passphrase is required for encryption, |reason| will be
+    //   REASON_ENCRYPTION.
+    // - If the passphrase is required for the decryption of data that has
+    //   already been encrypted, |reason| will be REASON_DECRYPTION.
+    // - If the passphrase is required because decryption failed, and a new
+    //   passphrase is required, |reason| will be REASON_SET_PASSPHRASE_FAILED.
+    //
+    // |pending_keys| is a copy of the cryptographer's pending keys, that may be
+    // cached by the frontend for subsequent use by the UI.
+    virtual void OnPassphraseRequired(
+        PassphraseRequiredReason reason,
+        const sync_pb::EncryptedData& pending_keys) = 0;
+    // Called when the passphrase provided by the user has been accepted and is
+    // now used to encrypt sync data.
+
+    virtual void OnPassphraseAccepted() = 0;
+    // |bootstrap_token| is an opaque base64 encoded representation of the key
+    // generated by the current passphrase, and is provided to the observer for
+    // persistence purposes and use in a future initialization of sync (e.g.
+    // after restart). The boostrap token will always be derived from the most
+    // recent GAIA password (for accounts with implicit passphrases), even if
+    // the data is still encrypted with an older GAIA password. For accounts
+    // with explicit passphrases, it will be the most recently seen custom
+    // passphrase.
+    virtual void OnBootstrapTokenUpdated(
+        const std::string& bootstrap_token) = 0;
+
+    // Called when the set of encrypted types or the encrypt
+    // everything flag has been changed.  Note that encryption isn't
+    // complete until the OnEncryptionComplete() notification has been
+    // sent (see below).
+    //
+    // |encrypted_types| will always be a superset of
+    // Cryptographer::SensitiveTypes().  If |encrypt_everything| is
+    // true, |encrypted_types| will be the set of all known types.
+    //
+    // Until this function is called, observers can assume that the
+    // set of encrypted types is Cryptographer::SensitiveTypes() and
+    // that the encrypt everything flag is false.
+    virtual void OnEncryptedTypesChanged(
+        ModelTypeSet encrypted_types,
+        bool encrypt_everything) = 0;
+
+    // Called after we finish encrypting the current set of encrypted
+    // types.
+    virtual void OnEncryptionComplete() = 0;
+
+    // The cryptographer has been updated. Listeners should check that their
+    // own state matches the cryptographer.
+    // Used primarily for debugging.
+    virtual void OnCryptographerStateChanged(Cryptographer* cryptographer) = 0;
+
+   protected:
+    virtual ~Observer();
+  };
+
+  SyncEncryptionHandler();
+  virtual ~SyncEncryptionHandler();
+
+  // Add/Remove SyncEncryptionHandler::Observer's.
+  // Must be called from sync thread.
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+
+  // Reads the nigori node, updates internal state as needed, and, if an
+  // empty/stale nigori node is detected, overwrites the existing
+  // nigori node. Upon completion, if the cryptographer is still ready
+  // attempts to re-encrypt all sync data.
+  // Note: This method is expensive (it iterates through all encrypted types),
+  // so should only be used sparingly (e.g. on startup).
+  virtual void Init() = 0;
+
+  // Attempts to re-encrypt encrypted data types using the passphrase provided.
+  // Notifies observers of the result of the operation via OnPassphraseAccepted
+  // or OnPassphraseRequired, updates the nigori node, and does re-encryption as
+  // appropriate. If an explicit password has been set previously, we drop
+  // subsequent requests to set a passphrase. If the cryptographer has pending
+  // keys, and a new implicit passphrase is provided, we try decrypting the
+  // pending keys with it, and if that fails, we cache the passphrase for
+  // re-encryption once the pending keys are decrypted.
+  virtual void SetEncryptionPassphrase(const std::string& passphrase,
+                                       bool is_explicit) = 0;
+
+  // Provides a passphrase for decrypting the user's existing sync data.
+  // Notifies observers of the result of the operation via OnPassphraseAccepted
+  // or OnPassphraseRequired, updates the nigori node, and does re-encryption as
+  // appropriate if there is a previously cached encryption passphrase. It is an
+  // error to call this when we don't have pending keys.
+  virtual void SetDecryptionPassphrase(const std::string& passphrase) = 0;
+
+  // Enables encryption of all datatypes.
+  virtual void EnableEncryptEverything() = 0;
+
+  // Whether encryption of all datatypes is enabled. If false, only sensitive
+  // types are encrypted.
+  virtual bool EncryptEverythingEnabled() const = 0;
+
+  // Whether the account requires a user-provided passphrase to decrypt
+  // encrypted data.
+  virtual bool IsUsingExplicitPassphrase() const = 0;
+
+  // The set of types that are always encrypted.
+  static ModelTypeSet SensitiveTypes();
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_ENCRYPTION_HANDLER_H_