Logto is an Auth0 alternative designed for modern apps and SaaS products. It offers both Cloud and Open-source services to help you quickly launch your identity and management (IAM) system. Enjoy authentication, authorization, and multi-tenant management all in one.
We recommend starting with a free development tenant on Logto Cloud. This allows you to explore all the features easily.
In this article, we will go through the steps to quickly build the Facebook sign-in experience (user authentication) with Flutter and Logto.
Prerequisites
- A running Logto instance. Check out the introduction page to get started.
- Basic knowledge of Flutter.
- A usable Facebook account.
Create an application in Logtoβ
Logto is based on OpenID Connect (OIDC) authentication and OAuth 2.0 authorization. It supports federated identity management across multiple applications, commonly called Single Sign-On (SSO).
To create your Native app application, simply follow these steps:
- Open the Logto Console. In the "Get started" section, click the "View all" link to open the application frameworks list. Alternatively, you can navigate to Logto Console > Applications, and click the "Create application" button.
- In the opening modal, click the "Native app" section or filter all the available "Native app" frameworks using the quick filter checkboxes on the left. Click the "Flutter" framework card to start creating your application.
- Enter the application name, e.g., "Bookstore," and click "Create application".
π Ta-da! You just created your first application in Logto. You'll see a congrats page which includes a detailed integration guide. Follow the guide to see what the experience will be in your application.
Integrate Flutter SDKβ
- The SDK package is available on pub.dev and Logto GitHub repository.
- The sample project is built using Flutter material. You can find it on pub.dev.
- This SDK is compatible with Flutter applications on iOS, Android, and Web platforms. Compatibility with other platforms has not been tested.
Installationβ
- pub.dev
- GitHub
You can install the logto_dart_sdk package
directly using the pub package manager.
Run the following command under your project root:
flutter pub add logto_dart_sdk
Or add the following to your pubspec.yaml
file:
dependencies:
logto_dart_sdk: ^3.0.0
Then run:
flutter pub get
If you prefer to fork your own version of the SDK, you can clone the repository directly from GitHub.
git clone https://github.com/logto-io/dart
Dependency and configurationsβ
SDK version compatibilityβ
Logto SDK version | Dart SDK version | Dart 3.0 compatible |
---|---|---|
< 2.0.0 | >= 2.17.6 < 3.0.0 | false |
>= 2.0.0 < 3.0.0 | >= 3.0.0 | true |
>= 3.0.0 | >= 3.6.0 | true |
flutter_secure_storage set upβ
Under the hood, this SDK uses flutter_secure_storage to implement the cross-platform persistent secure token storage.
- Keychain is used for iOS
- AES encryption is used for Android.
Config Android versionβ
Set the android:minSdkVersion to >= 18
in your project's android/app/build.gradle
file.
android {
...
defaultConfig {
...
minSdkVersion 18
...
}
}
Disable auto backup on Androidβ
By default Android backups data on Google Drive. It can cause exception java.security.InvalidKeyException:Failed
to unwrap key. To avoid this,
-
To disable auto backup, go to your app manifest file and set the
android:allowBackup
andandroid:fullBackupContent
attributes tofalse
.AndroidManifest.xml<manifest ... >
...
<application
android:allowBackup="false"
android:fullBackupContent="false"
...
>
...
</application>
</manifest> -
Exclude
sharedprefs
fromFlutterSecureStorage
.If you need to keep the
android:fullBackupContent
for your app rather than disabling it, you can exclude thesharedprefs
directory from the backup. See more details in the Android documentation.In your AndroidManifest.xml file, add the android:fullBackupContent attribute to the
<application>
element, as shown in the following example. This attribute points to an XML file that contains backup rules.AndroidManifest.xml<application ...
android:fullBackupContent="@xml/backup_rules">
</application>Create an XML file called
@xml/backup_rules
in theres/xml/
directory. In this file, add rules with the<include>
and<exclude>
elements. The following sample backs up all shared preferences except device.xml:@xml/backup_rules<?xml version="1.0" encoding="utf-8"?>
<full-backup-content>
<exclude domain="sharedpref" path="FlutterSecureStorage"/>
</full-backup-content>
Please check flutter_secure_storage for more details.
flutter_web_auth_2 set upβ
Behind the scenes, this SDK uses flutter_web_auth_2 to authenticate users with Logto. This package provides a simple way to authenticate users with Logto using the system webview or browser.
This plugin uses ASWebAuthenticationSession
on iOS 12+ and macOS 10.15+, SFAuthenticationSession
on iOS 11, Chrome Custom Tabs
on Android and opens a new window on Web.
-
iOS: No additional setup required
-
Android: Register the callback url on Android
In order to capture the callback url from Logto's sign-in web page, you will need to register your sign-in redirectUri to your
AndroidManifest.xml
file.AndroidManifest.xml<manifest>
<application>
<activity
android:name="com.linusu.flutter_web_auth_2.CallbackActivity"
android:exported="true">
<intent-filter android:label="flutter_web_auth_2">
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
<data android:scheme="YOUR_CALLBACK_URL_SCHEME_HERE" />
</intent-filter>
</activity>
</application>
</manifest> -
Web browser: Create an endpoint to handle the callback URL
If you are using the web platform, you need to create an endpoint to handle the callback URL and send it back to the application using the
postMessage
API.callback.html<!doctype html>
<title>Authentication complete</title>
<p>Authentication is complete. If this does not happen automatically, please close the window.</p>
<script>
function postAuthenticationMessage() {
const message = {
'flutter-web-auth-2': window.location.href,
};
if (window.opener) {
window.opener.postMessage(message, window.location.origin);
window.close();
} else if (window.parent && window.parent !== window) {
window.parent.postMessage(message, window.location.origin);
} else {
localStorage.setItem('flutter-web-auth-2', window.location.href);
window.close();
}
}
postAuthenticationMessage();
</script>
Please check the setup guide in the flutter_web_auth_2 package for more details.
Integrationβ
Init LogtoClientβ
Import the logto_dart_sdk
package and initialize the LogtoClient
instance at the root of your application.
import 'package:logto_dart_sdk/logto_dart_sdk.dart';
import 'package:http/http.dart' as http;
void main() async {
WidgetsFlutterBinding.ensureInitialized();
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Flutter Demo',
home: MyHomePage(title: 'Logto Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
late LogtoClient logtoClient;
void render() {
// state change
}
// LogtoConfig
final logtoConfig = const LogtoConfig(
endpoint: "<your-logto-endpoint>",
appId: "<your-app-id>"
);
void _init() {
logtoClient = LogtoClient(
config: logtoConfig,
httpClient: http.Client(), // Optional http client
);
render();
}
void initState() {
super.initState();
_init();
}
// ...
}
Implement sign-inβ
Before we dive into the details, here's a quick overview of the end-user experience. The sign-in process can be simplified as follows:
- Your app invokes the sign-in method.
- The user is redirected to the Logto sign-in page. For native apps, the system browser is opened.
- The user signs in and is redirected back to your app (configured as the redirect URI).
Regarding redirect-based sign-inβ
- This authentication process follows the OpenID Connect (OIDC) protocol, and Logto enforces strict security measures to protect user sign-in.
- If you have multiple apps, you can use the same identity provider (Logto). Once the user signs in to one app, Logto will automatically complete the sign-in process when the user accesses another app.
To learn more about the rationale and benefits of redirect-based sign-in, see Logto sign-in experience explained.
Before starting, you need to add a redirect URI in the Admin Console for your application.
Let's switch to the Application details page of Logto Console. Add a Redirect URI io.logto://callback
and click "Save changes".
- For iOS, the redirect URI scheme does not really matter since the
ASWebAuthenticationSession
class will listen to the redirect URI regardless of if it's registered. - For Android, the redirect URI scheme must be registered in the
AndroidManifest.xml
file.
After the redirect URI is configured, we add a sign-in button to your page, which will call logtoClient.signIn
API to invoke the Logto sign-in flow:
class _MyHomePageState extends State<MyHomePage> {
// ...
final redirectUri = 'io.logto://callback';
Widget build(BuildContext context) {
// ...
Widget signInButton = TextButton(
onPressed: () async {
await logtoClient.signIn(redirectUri);
render();
},
child: const Text('Sign In'),
);
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
SelectableText('My Demo App'),
signInButton,
],
),
),
);
}
}
Implement sign-outβ
Let's switch to the Application details page of Logto Console. Add a Post Sign-out Redirect
URI io.logto://callback
and click "Save changes".
Post Sign-outRedirect URI is an OAuth 2.0 concept which implies the location should redirect after signing out.
Now let's add a sign-out button on the main page so users can sign out from your application.
class _MyHomePageState extends State<MyHomePage> {
// ...
final postSignOutRedirectUri = 'io.logto//home';
Widget build(BuildContext context) {
// ...
Widget signOutButton = TextButton(
onPressed: () async {
await logtoClient.signOut(postSignOutRedirectUri);
render();
},
child: const Text('Sign Out'),
);
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
SelectableText('My Demo App'),
signInButton,
signOutButton,
],
),
),
);
}
}
Handle authentication statusβ
Logto SDK provides an asynchronous method to check the authentication status. The method is logtoClient.isAuthenticated
. The method returns a boolean value, true
if the user is authenticated, otherwise false
.
In the example we conditionally render the sign-in and sign-out buttons based on the authentication status. Now let's update the render
method in our Widget to handle the state change:
class _MyHomePageState extends State<MyHomePage> {
// ...
bool? isAuthenticated = false;
void render() {
setState(() async {
isAuthenticated = await logtoClient.isAuthenticated;
});
}
Widget build(BuildContext context) {
// ...
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
SelectableText('My Demo App'),
isAuthenticated == true ? signOutButton : signInButton,
],
),
),
);
}
}
Checkpoint: Test your applicationβ
Now, you can test your application:
- Run your application, you will see the sign-in button.
- Click the sign-in button, the SDK will init the sign-in process and redirect you to the Logto sign-in page.
- After you signed in, you will be redirected back to your application and see the sign-out button.
- Click the sign-out button to clear token storage and sign out.
Add Facebook connectorβ
To enable quick sign-in and improve user conversion, connect with Flutter as an identity provider. The Logto social connector helps you establish this connection in minutes by allowing several parameter inputs.
To add a social connector, simply follow these steps:
- Navigate to Console > Connectors > Social Connectors.
- Click "Add social connector" and select "Facebook".
- Follow the README guide and complete required fields and customize settings.
If you are following the in-place Connector guide, you can skip the next section.
Set up Facebook loginβ
Register a Facebook developer accountβ
Register as a Facebook Developer if you don't already have one
Set up a Facebook appβ
- Visit the Apps page.
- Click your existing app or create a new one if needed.
- The selected app type is up to you, but it should have the product Facebook Login.
- On the app dashboard page, scroll to the "Add a product" section and click the "Set up" button on the "Facebook Login" card.
- Skip the Facebook Login Quickstart page, and click the sidebar -> "Products" -> "Facebook Login" -> "Settings".
- In the Facebook Login Settings page, fill
${your_logto_origin}/callback/${connector_id}
in the "Valid OAuth Redirect URIs" field. Theconnector_id
can be found on the top bar of the Logto Admin Console connector details page. E.g.:https://logto.dev/callback/${connector_id}
for productionhttps://localhost:3001/callback/${connector_id}
for testing in the local environment
- Click the "Save changes" button at the bottom right corner.
Compose the connector JSONβ
- In the Facebook app dashboard page, click the sidebar -> "Settings" -> "Basic".
- You will see the "App ID" and "App secret" on the panel.
- Click the "Show" button following the App secret input box to copy its content.
- Fill out the Logto connector settings:
- Fill out the
clientId
field with the string from App ID. - Fill out the
clientSecret
field with the string from App secret. - Fill out the
scope
field with a comma or space separated list of permissions in string. If you do not specify a scope, the default scope isemail,public_profile
.
- Fill out the
Test sign-in with Facebook's test usersβ
You can use the accounts of the test, developer, and admin users to test sign-in with the related app under both development and live app modes.
You can also take the app live directly so that any Facebook user can sign in with the app.
- In the app dashboard page, click the sidebar -> "Roles" -> "Test Users".
- Click the "Create test users" button to create a testing user.
- Click the "Options" button of the existing test user, and you will see more operations, e.g., "Change name and password".
Publish Facebook sign-in settingsβ
Usually, only the test, admin, and developer users can sign in with the related app under development mode.
To enable normal Facebook users sign-in with the app in the production environment, you maybe need to switch your Facebook app to live mode, depending on the app type. E.g., the pure business type app doesn't have the "live" switch button, but it won't block your use.
- In the Facebook app dashboard page, click the sidebar -> "Settings" -> "Basic".
- Fill out the "Privacy Policy URL" and "User data deletion" fields on the panel if required.
- Click the "Save changes" button at the bottom right corner.
- Click the "Live" switch button on the app top bar.
Config typesβ
Name | Type |
---|---|
clientId | string |
clientSecret | string |
scope | string |
Save your configurationβ
Double check you have filled out necessary values in the Logto connector configuration area. Click "Save and Done" (or "Save changes") and the Facebook connector should be available now.
Enable Facebook connector in Sign-in Experienceβ
Once you create a social connector successfully, you can enable it as a "Continue with Facebook" button in Sign-in Experience.
- Navigate to Console > Sign-in experience > Sign-up and sign-in.
- (Optional) Choose "Not applicable" for sign-up identifier if you need social login only.
- Add configured Facebook connector to the "Social sign-in" section.
Testing and Validationβ
Return to your Flutter app. You should now be able to sign in with Facebook. Enjoy!
Further readingsβ
End-user flows: Logto provides a out-of-the-box authentication flows including MFA and enterprise SSO, along with powerful APIs for flexible implementation of account settings, security verification, and multi-tenant experience.
Authorization: Authorization defines the actions a user can do or resources they can access after being authenticated. Explore how to protect your API for native and single-page applications and implement Role-based Access Control (RBAC).
Organizations: Particularly effective in multi-tenant SaaS and B2B apps, the organization feature enable tenant creation, member management, organization-level RBAC, and just-in-time-provisioning.
Customer IAM series Our serial blog posts about Customer (or Consumer) Identity and Access Management, from 101 to advanced topics and beyond.