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 OIDC 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 OIDC 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 OIDC 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 "OIDC".
- 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 Standard OIDC appβ
Create your OIDC appβ
When you open this page, we believe you already know which social identity provider you want to connect to. The first thing to do is to confirm that the identity provider supports the OIDC protocol, which is a prerequisite for configuring a valid connector. Then, follow the identity provider's instructions to register and create the relevant app for OIDC authorization.
Configure your connectorβ
We ONLY support "Authorization Code" grant type for security consideration and it can perfectly fit Logto's scenario.
clientId
and clientSecret
can be found at your OIDC apps details page.
clientId: The client ID is a unique identifier that identifies the client application during registration with the authorization server. This ID is used by the authorization server to verify the identity of the client application and to associate any authorized access tokens with that specific client application.
clientSecret: The client secret is a confidential key that is issued to the client application by the authorization server during registration. The client application uses this secret key to authenticate itself with the authorization server when requesting access tokens. The client secret is considered confidential information and should be kept secure at all times.
tokenEndpointAuthMethod: The token endpoint authentication method is used by the client application to authenticate itself with the authorization server when requesting access tokens. To discover supported methods, consult the token_endpoint_auth_methods_supported
field available at the OAuth 2.0 service providerβs OpenID Connect discovery endpoint, or refer to the relevant documentation provided by the OAuth 2.0 service provider.
clientSecretJwtSigningAlgorithm (Optional): Only required when tokenEndpointAuthMethod
is client_secret_jwt
. The client secret JWT signing algorithm is used by the client application to sign the JWT that is sent to the authorization server during the token request.
scope: The scope parameter is used to specify the set of resources and permissions that the client application is requesting access to. The scope parameter is typically defined as a space-separated list of values that represent specific permissions. For example, a scope value of "read write" might indicate that the client application is requesting read and write access to a user's data.
You are expected to find authorizationEndpoint
, tokenEndpoint
, jwksUri
and issuer
as OpenID Provider's configuration information. They should be available in social vendor's documentation.
authenticationEndpoint: This endpoint is used to initiate the authentication process. The authentication process typically involves the user logging in and granting authorization for the client application to access their resources.
tokenEndpoint: This endpoint is used by the client application to obtain an id token that can be used to access the requested resources. The client application typically sends a request to the token endpoint with a grant type and authorization code to receive an id token.
jwksUri: This is the URL endpoint where the JSON Web Key Set (JWKS) of the social identity provider (IdP for short) can be obtained. The JWKS is a set of cryptographic keys that the IdP uses to sign and verify JSON Web Tokens (JWTs) that are issued during the authentication process. The jwksUri
is used by the relying party (RP) to obtain the public keys used by the IdP to sign the JWTs, so the RP can verify the authenticity and integrity of the JWTs received from the IdP.
issuer: This is the unique identifier of the IdP that is used by the RP to verify the JWTs received from the IdP. It is included in the JWTs as the iss
claim (Id token is always a JWT). The issuer value should match the URL of the IdP's authorization server, and it should be a URI that the RP trusts. When the RP receives a JWT, it checks the iss
claim to ensure that it was issued by a trusted IdP, and that the JWT is intended for use with the RP.
Together, jwksUri
and issuer
provide a secure mechanism for the RP to verify the identity of the end-user during the authentication process. By using the public keys obtained from the jwksUri
, the RP can verify the authenticity and integrity of the JWTs issued by the IdP. The issuer value ensures that the RP only accepts JWTs that were issued by a trusted IdP, and that the JWTs are intended for use with the RP.
Since an authentication request is always required, an authRequestOptionalConfig
is provided to wrap all optional configs, you can find details on OIDC Authentication Request. You may also find that nonce
is missing in this config. Since nonce
should identical for each request, we put the generation of nonce
in code implementation. So do not worry about it! Previously mentioned jwksUri
and issuer
are also included in idTokenVerificationConfig
.
You may be curious as to why a standard OIDC protocol supports both the implicit and hybrid flows, yet the Logto connector only supports the authorization flow. It has been determined that the implicit and hybrid flows are less secure than the authorization flow. Due to Logto's focus on security, it only supports the authorization flow for the highest level of security for its users, despite its slightly less convenient nature.
responseType
and grantType
can ONLY be FIXED values with "Authorization Code" flow, so we make them optional and default values will be automatically filled.
For all flow types, we provided an OPTIONAL customConfig
key to put your customize parameters.
Each social identity provider could have their own variant on OIDC standard protocol. If your desired social identity provider strictly stick to OIDC standard protocol, the you do not need to care about customConfig
.
Config typesβ
Name | Type | Required |
---|---|---|
scope | string | True |
clientId | string | True |
clientSecret | string | True |
authorizationEndpoint | string | True |
tokenEndpoint | string | True |
idTokenVerificationConfig | IdTokenVerificationConfig | True |
authRequestOptionalConfig | AuthRequestOptionalConfig | False |
customConfig | Record<string, string> | False |
AuthRequestOptionalConfig properties | Type | Required |
---|---|---|
responseType | string | False |
tokenEndpoint | string | False |
responseMode | string | False |
display | string | False |
prompt | string | False |
maxAge | string | False |
uiLocales | string | False |
idTokenHint | string | False |
loginHint | string | False |
acrValues | string | False |
IdTokenVerificationConfig properties | Type | Required |
---|---|---|
jwksUri | string | True |
issuer | string | string[] | False |
audience | string | string[] | False |
algorithms | string[] | False |
clockTolerance | string | number | False |
crit | Record<string, string | boolean> | False |
currentDate | Date | False |
maxTokenAge | string | number | False |
subject | string | False |
typ | string | False |
See here to find more details about IdTokenVerificationConfig
.
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 OIDC connector should be available now.
Enable OIDC connector in Sign-in Experienceβ
Once you create a social connector successfully, you can enable it as a "Continue with OIDC" 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 OIDC connector to the "Social sign-in" section.
Testing and Validationβ
Return to your Flutter app. You should now be able to sign in with OIDC. 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.