Keycloak User Registration And Authentication In Flutter With Traefik And Docker
This article delves into the intricate process of implementing user registration and authentication in a Flutter application, leveraging the robust capabilities of Keycloak as an Identity and Access Management (IAM) solution. We will explore how to seamlessly integrate Keycloak with a Flutter app, focusing on creating a custom user interface (UI) for registration while ensuring secure communication through Traefik, a modern reverse proxy, all within a Dockerized environment. This comprehensive guide addresses the challenges developers face when building secure and scalable authentication flows in their Flutter applications.
Understanding the Core Components
Before diving into the implementation details, let's establish a firm understanding of the key technologies involved in this setup:
- Keycloak: At the heart of our authentication system lies Keycloak, an open-source IAM solution that provides a centralized platform for managing users, roles, and permissions. Keycloak simplifies the complexities of authentication and authorization, offering features like single sign-on (SSO), multi-factor authentication (MFA), and social login integration. Keycloak's flexibility and scalability make it an ideal choice for modern applications.
- Flutter: On the client-side, we have Flutter, Google's UI toolkit for building natively compiled applications for mobile, web, and desktop from a single codebase. Flutter's rich set of widgets, hot-reloading capabilities, and cross-platform compatibility make it a powerful tool for developing engaging user interfaces. Integrating Flutter with Keycloak allows us to create a secure and user-friendly authentication experience.
- Traefik: To secure our application and manage traffic effectively, we employ Traefik, a modern reverse proxy and load balancer. Traefik dynamically configures itself based on the services running in our Docker environment, simplifying the deployment and management of our application. Traefik handles SSL termination, load balancing, and request routing, ensuring a secure and scalable architecture.
- Docker: Docker provides a containerization platform that allows us to package our application and its dependencies into isolated containers. This ensures consistency and portability across different environments. Docker simplifies the deployment process and makes it easier to scale our application.
Setting up Keycloak with Docker
To begin, we need to set up a Keycloak instance using Docker. This involves creating a docker-compose.yml file that defines the Keycloak service and its dependencies. Here's a basic example:
version: '3.8'
services:
keycloak:
image: jboss/keycloak
ports:
- "8080:8080"
environment:
- KEYCLOAK_USER=admin
- KEYCLOAK_PASSWORD=admin
volumes:
- keycloak_data:/opt/jboss/keycloak/standalone/data
volumes:
keycloak_data:
This configuration defines a Keycloak service that listens on port 8080. It also sets the initial admin username and password. For production environments, it's crucial to configure a persistent volume for the Keycloak data to prevent data loss.
Once the docker-compose.yml file is created, you can start the Keycloak container using the following command:
docker-compose up -d
After the container is running, you can access the Keycloak admin console by navigating to http://localhost:8080 in your web browser. Log in using the credentials specified in the docker-compose.yml file.
Configuring Keycloak Realms and Clients
Within the Keycloak admin console, you need to create a realm for your application. A realm is a logical grouping of users, roles, and clients. It allows you to isolate different applications and their respective users.
To create a realm, click on the "Add realm" button and provide a name for your realm. Once the realm is created, you need to configure a client for your Flutter application. A client represents an application that interacts with Keycloak for authentication and authorization.
To create a client, select your realm and click on the "Clients" menu item. Then, click on the "Create" button and configure the following settings:
- Client ID: A unique identifier for your client.
- Client Protocol: Select "openid-connect".
- Root URL: The base URL of your Flutter application.
- Valid Redirect URIs: The URIs to which Keycloak will redirect after successful authentication.
- Web Origins: The origins from which your Flutter application will make requests to Keycloak.
It's essential to configure these settings correctly to ensure secure communication between your Flutter application and Keycloak. Incorrectly configured settings can lead to security vulnerabilities.
Implementing User Registration in Flutter
Now, let's focus on implementing user registration in your Flutter application. There are two primary approaches:
- Redirecting to Keycloak's Registration Page: This is the simplest approach, where you redirect users to the Keycloak registration page. Keycloak handles the UI and logic for user registration. However, this approach provides less control over the user experience.
- Creating a Custom Registration UI: This approach involves building your own registration UI in Flutter and using the Keycloak Admin REST API to create users. This approach offers greater flexibility and control over the user experience but requires more implementation effort.
Creating a Custom Registration UI in Flutter
For a more tailored user experience, we'll explore creating a custom registration UI in Flutter. This involves designing the UI, handling user input, and making API calls to Keycloak to create the user.
Designing the Registration UI
First, you need to design the registration UI in Flutter. This typically involves creating a form with fields for username, email, password, and other relevant user information. Use Flutter's rich set of widgets to create an intuitive and visually appealing form.
import 'package:flutter/material.dart';
class RegistrationScreen extends StatefulWidget {
@override
_RegistrationScreenState createState() => _RegistrationScreenState();
}
class _RegistrationScreenState extends State<RegistrationScreen> {
final _formKey = GlobalKey<FormState>();
final _usernameController = TextEditingController();
final _emailController = TextEditingController();
final _passwordController = TextEditingController();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Register')),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: Form(
key: _formKey,
child: Column(
children: [
TextFormField(
controller: _usernameController,
decoration: InputDecoration(labelText: 'Username'),
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter a username';
}
return null;
},
),
TextFormField(
controller: _emailController,
decoration: InputDecoration(labelText: 'Email'),
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter an email';
}
if (!value.contains('@')) {
return 'Please enter a valid email';
}
return null;
},
),
TextFormField(
controller: _passwordController,
decoration: InputDecoration(labelText: 'Password'),
obscureText: true,
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter a password';
}
return null;
},
),
SizedBox(height: 16),
ElevatedButton(
onPressed: () {
if (_formKey.currentState!.validate()) {
// Call registration API
}
},
child: Text('Register'),
),
],
),
),
),
);
}
}
This code snippet demonstrates a basic registration form with fields for username, email, and password. It includes validation to ensure that the user provides valid input.
Calling the Keycloak Admin REST API
To create users in Keycloak, you need to use the Keycloak Admin REST API. This API allows you to programmatically manage users, roles, and other Keycloak entities. To use the API, you need to obtain an access token with appropriate permissions.
The process typically involves the following steps:
- Obtain an access token: You need to authenticate as an administrator user or a service account with the
realm-adminrole to obtain an access token. - Make a POST request to the
/auth/admin/realms/{realm}/usersendpoint: This endpoint allows you to create new users in the specified realm. - Include the user data in the request body: The request body should be a JSON object containing the user's information, such as username, email, password, and enabled status.
import 'dart:convert';
import 'package:http/http.dart' as http;
Future<void> registerUser(String username, String email, String password) async {
final url = Uri.parse('http://localhost:8080/auth/admin/realms/your-realm/users');
final token = 'YOUR_ADMIN_ACCESS_TOKEN'; // Replace with your actual token
final headers = {
'Content-Type': 'application/json',
'Authorization': 'Bearer $token',
};
final body = jsonEncode({
'username': username,
'email': email,
'enabled': true,
'credentials': [
{
'type': 'password',
'value': password,
'temporary': false,
},
],
});
final response = await http.post(url, headers: headers, body: body);
if (response.statusCode == 201) {
// User created successfully
print('User registered successfully');
} else {
// Handle error
print('Error registering user: ${response.statusCode} ${response.body}');
}
}
This code snippet demonstrates how to make a POST request to the Keycloak Admin REST API to create a user. Remember to replace YOUR_ADMIN_ACCESS_TOKEN with your actual access token and your-realm with your realm name. Also, handle potential errors and display appropriate messages to the user.
Securing the Admin API Calls
It's crucial to secure the calls to the Keycloak Admin REST API. Never expose your admin access token in the client-side code. Instead, implement a backend service that handles the API calls to Keycloak. This service can authenticate the Flutter application and then make the necessary API calls to Keycloak on its behalf. This approach adds an extra layer of security and prevents unauthorized access to the Keycloak Admin REST API.
Implementing User Authentication in Flutter
After user registration, the next step is to implement user authentication in your Flutter application. This involves authenticating the user against Keycloak and obtaining an access token.
Using the OpenID Connect Protocol
Keycloak supports the OpenID Connect (OIDC) protocol, which is a widely used standard for authentication and authorization. You can use an OIDC client library in your Flutter application to handle the authentication flow. Several Flutter packages are available that simplify the integration with Keycloak using OIDC.
The authentication flow typically involves the following steps:
- Redirect the user to the Keycloak authorization endpoint: This endpoint initiates the authentication process.
- Keycloak authenticates the user: Keycloak prompts the user to enter their credentials or use a social login provider.
- Keycloak redirects the user back to your application with an authorization code: This code is a temporary credential that can be exchanged for an access token.
- Your application exchanges the authorization code for an access token: This involves making a POST request to the Keycloak token endpoint.
- Keycloak returns an access token and a refresh token: The access token is used to authenticate subsequent requests to your application's backend. The refresh token is used to obtain a new access token when the current one expires.
Integrating with a Flutter OIDC Client Library
Let's look at an example of how to integrate with Keycloak using a Flutter OIDC client library. For instance, you can use the flutter_appauth package.
First, add the flutter_appauth dependency to your pubspec.yaml file:
dependencies:
flutter_appauth: ^4.2.0
Then, run flutter pub get to install the dependency.
Next, implement the authentication flow in your Flutter application:
import 'package:flutter_appauth/flutter_appauth.dart';
final FlutterAppAuth appAuth = FlutterAppAuth();
Future<void> login() async {
try {
final AuthorizationTokenResponse? result = await appAuth.authorizeAndExchangeCode(
AuthorizationTokenRequest(
'your-client-id', // Replace with your client ID
'your-redirect-uri', // Replace with your redirect URI
issuer: 'http://localhost:8080/auth/realms/your-realm', // Replace with your Keycloak URL
scopes: ['openid', 'profile', 'email'],
),
);
if (result != null) {
// Authentication successful
print('Access token: ${result.accessToken}');
} else {
// Authentication failed
print('Authentication failed');
}
} catch (e) {
print('Error during authentication: $e');
}
}
This code snippet demonstrates how to use the flutter_appauth package to initiate the authentication flow. Remember to replace your-client-id, your-redirect-uri, and http://localhost:8080/auth/realms/your-realm with your actual values.
Storing and Using the Access Token
After obtaining the access token, you need to store it securely and use it to authenticate subsequent requests to your application's backend. You can use a secure storage mechanism, such as flutter_secure_storage, to store the access token.
To use the access token, include it in the Authorization header of your HTTP requests:
import 'package:http/http.dart' as http;
Future<void> makeAuthenticatedRequest(String accessToken) async {
final url = Uri.parse('your-backend-api-endpoint'); // Replace with your API endpoint
final headers = {
'Authorization': 'Bearer $accessToken',
};
final response = await http.get(url, headers: headers);
if (response.statusCode == 200) {
// Request successful
print('Response: ${response.body}');
} else {
// Handle error
print('Error: ${response.statusCode} ${response.body}');
}
}
This code snippet demonstrates how to include the access token in the Authorization header of an HTTP request. Your backend should validate the access token before processing the request.
Integrating Traefik for Secure Communication
To secure communication with Keycloak and your application's backend, we'll integrate Traefik as a reverse proxy. Traefik can handle SSL termination, load balancing, and request routing, ensuring a secure and scalable architecture.
Configuring Traefik
To configure Traefik, you need to create a traefik.yml file that defines the Traefik configuration. Here's a basic example:
api:
dashboard: true
entryPoints:
web:
address: ":80"
websecure:
address: ":443"
providers:
docker:
exposedByDefault: false
certificatesResolvers:
letsencrypt:
acme:
email: "your-email@example.com" # Replace with your email
storage: /letsencrypt/acme.json
httpChallenge:
entryPoint: web
This configuration defines two entry points: web (port 80) and websecure (port 443). It also configures Traefik to use the Docker provider, which allows Traefik to dynamically configure itself based on the services running in your Docker environment. The letsencrypt certificate resolver is configured to automatically obtain SSL certificates from Let's Encrypt.
Configuring Docker Services for Traefik
To integrate your services with Traefik, you need to add labels to your Docker service definitions. These labels tell Traefik how to route requests to your services. For example, to route requests to your Keycloak service, you can add the following labels to your Keycloak service definition in docker-compose.yml:
services:
keycloak:
image: jboss/keycloak
ports:
- "8080:8080"
environment:
- KEYCLOAK_USER=admin
- KEYCLOAK_PASSWORD=admin
volumes:
- keycloak_data:/opt/jboss/keycloak/standalone/data
labels:
- "traefik.enable=true"
- "traefik.http.routers.keycloak.rule=Host(`keycloak.your-domain.com`)" # Replace with your domain
- "traefik.http.routers.keycloak.entrypoints=websecure"
- "traefik.http.routers.keycloak.tls.certresolver=letsencrypt"
volumes:
keycloak_data:
These labels tell Traefik to:
- Enable Traefik for this service.
- Route requests with the host
keycloak.your-domain.comto this service. - Use the
websecureentry point (port 443). - Use the
letsencryptcertificate resolver to obtain an SSL certificate.
Repeat this process for your application's backend service.
Running Traefik with Docker
To run Traefik with Docker, you need to create a docker-compose.yml file that defines the Traefik service. Here's an example:
version: '3.8'
services:
traefik:
image: traefik:v2.5
ports:
- "80:80"
- "443:443"
- "8080:8080" # Optional: for Traefik dashboard
volumes:
- ./traefik.yml:/etc/traefik/traefik.yml
- ./letsencrypt:/letsencrypt
- /var/run/docker.sock:/var/run/docker.sock:ro
labels:
- "traefik.enable=true"
This configuration defines a Traefik service that listens on ports 80, 443, and 8080. It also mounts the traefik.yml file and the letsencrypt directory, which stores the SSL certificates. The /var/run/docker.sock:/var/run/docker.sock:ro volume allows Traefik to communicate with the Docker daemon and dynamically configure itself based on the services running in your environment.
Start Traefik using docker-compose up -d. Once Traefik is running, it will automatically configure itself based on the labels defined in your Docker service definitions.
Conclusion
Integrating Keycloak with a Flutter application for user registration and authentication, while leveraging Traefik and Docker, provides a robust and scalable solution for modern application development. This article has covered the essential steps, from setting up Keycloak with Docker to implementing custom registration UIs in Flutter and securing communication with Traefik. By following these guidelines, developers can build secure and user-friendly authentication flows in their Flutter applications, ensuring a seamless user experience while maintaining a high level of security.