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flutter_secure_storage

Pub style: lint flutter_secure_storage flutter_secure_storage GitHub Sponsors

A Flutter plugin to securely store sensitive data in a key-value pair format using platform-specific secure storage solutions. It supports Android, iOS, macOS, Windows, and Linux.

Features

  • Secure Data Storage: Uses Keychain for iOS, Encrypted Shared Preferences via Tink for Android, and secure mechanisms on other supported platforms.
  • Encryption: Encrypts data before storing it in the underlying storage system.
  • Cross-Platform: Works seamlessly across multiple platforms.
  • Customizable Options: Set accessibility attributes, key expiration, and more.

Important notice for Android

Beginning with version 10, all data will be transitioned to encryptedSharedPreferences. As a result, the useEncryptedSharedPreferences option will be deprecated.

In version 11, the migration tool will no longer be available. To ensure users retain their data, it is essential to first upgrade to version 10 before proceeding to version 11.

Due to this update, the minimum required Android SDK will be 23.

Important notice for Web

flutter_secure_storage only works on HTTPS or localhost environments. Please see this issue for more information.

WASM support

You can opt-in into the new WASM compatible version of flutter_secure_storage_web by adding the following override in your pubspec.yaml:

dependency_overrides:
  flutter_secure_storage_web: ^2.0.0-beta.2

Installation

If not present already, please call WidgetsFlutterBinding.ensureInitialized() in your main before you do anything with the MethodChannel. Please see this issue for more info.

Add the dependency in your pubspec.yaml file:

dependencies:
flutter_secure_storage: ^<latest_version>

Then run:

flutter pub get

Usage

Import the Package

import 'package:flutter_secure_storage/flutter_secure_storage.dart';

Create an Instance

final storage = FlutterSecureStorage();

Write Data

await storage.write(key: 'username', value: 'flutter_user');

Read Data

String? username = await storage.read(key: 'username');

Delete Data

await storage.delete(key: 'username');

Delete All Data

await storage.deleteAll();

Check for Key Existence

bool containsKey = await storage.containsKey(key: 'username');

Configuration

Each platform provides its own set of configuration options to tailor secure storage behavior. For example, on iOS, the IOSOptions class includes an accessibility option that determines when the app can access secure values stored in the Keychain.

The accessibility option allows you to specify conditions under which secure values are accessible. For instance:

  • first_unlock: Enables access to secure values after the device is unlocked for the first time after a reboot.
  • first_unlock_this_device: Allows access to secure values only after the device is unlocked for the first time since installation on this device.
  • unlocked (default): Values are accessible only when the device is unlocked.

Here’s an example of configuring the accessibility option on iOS:

final options = IOSOptions(accessibility: KeychainAccessibility.first_unlock);
await storage.write(key: key, value: value, iOptions: options);

By setting accessibility, you can control when secure values are accessible, enhancing security and usability for your app on iOS. Similar platform-specific options are available for other platforms as well.

Android

Note By default Android backups data on Google Drive. It can cause exception java.security.InvalidKeyException:Failed to unwrap key. You need to

Add the following to your android/app/src/main/AndroidManifest.xml:

<application android:allowBackup="false" ...>

iOS

Set the Keychain accessibility options in the Info.plist file (if needed):

keychain-access-groups $(AppIdentifierPrefix)com.example.flutterSecureStorageExample

macOS

You also need to add Keychain Sharing as capability to your macOS runner. To achieve this, please add the following in both your macos/Runner/DebugProfile.entitlements and macos/Runner/Release.entitlements (you need to change both files).

<key>keychain-access-groups</key>
<array/>

If you have set your application up to use App Groups then you will need to add the name of the App Group to the keychain-access-groups argument above. Failure to do so will result in values appearing to be written successfully but never actually being written at all. For example if your app has an App Group named "aoeu" then your value for above would instead read:

<key>keychain-access-groups</key>
<array>
	<string>$(AppIdentifierPrefix)aoeu</string>
</array>

If you are configuring this value through XCode then the string you set in the Keychain Sharing section would simply read "aoeu" with XCode appending the $(AppIdentifierPrefix) when it saves the configuration.

Web

Flutter Secure Storage uses an experimental implementation using WebCrypto. Use at your own risk at this time. Feedback welcome to improve it. The intent is that the browser is creating the private key, and as a result, the encrypted strings in local_storage are not portable to other browsers or other machines and will only work on the same domain.

It is VERY important that you have HTTP Strict Forward Secrecy enabled and the proper headers applied to your responses or you could be subject to a javascript hijack.

Please see:

application-specific key option

On the web, all keys are stored in LocalStorage. flutter_secure_storage has an option for the web to wrap this stored key with an application-specific key to make it more difficult to analyze.

final _storage = const FlutterSecureStorage(
  webOptions: WebOptions(
    wrapKey: '${your_application_specific_key}',
    wrapKeyIv: '${your_application_specific_iv}',
  ),
);

Windows

You need the C++ ATL libraries installed along with the rest of Visual Studio Build Tools. Download them from here and make sure the C++ ATL under optional is installed as well.

Linux

You need libsecret-1-dev and libjsoncpp-dev on your machine to build the project, and libsecret-1-0 and libjsoncpp1 to run the application (add it as a dependency after packaging your app). If you using snapcraft to build the project use the following

parts:
  uet-lms:
    source: .
    plugin: flutter
    flutter-target: lib/main.dart
    build-packages:
      - libsecret-1-dev
      - libjsoncpp-dev
    stage-packages:
      - libsecret-1-0
      - libjsoncpp-dev

Apart from libsecret you also need a keyring service, for that you need either gnome-keyring (for Gnome users) or ksecretsservice (for KDE users) or other light provider like secret-service.

Integration Tests

To run the integration tests, navigate to the example directory and execute the following command:

flutter drive --target=test_driver/app.dart

This will launch the integration tests specified in the test_driver directory.

Contributing

We welcome contributions to this project! To set up your workspace after cloning the repository, follow these steps:

  1. Fetch the Flutter dependencies: flutter pub get

  2. Activate melos: dart pub global activate melos

  3. (Optional) Add pub executables to your path: export PATH="$PATH":"$HOME/.pub-cache/bin"

  4. Bootstrap the workspace with melos: melos bootstrap

This will prepare the project for development by linking and configuring all required dependencies.

API Reference

For a complete list of available methods and configuration options, refer to the API documentation.

License

This project is licensed under the BSD 3 License. See the LICENSE file for details.