JWT & OpenID Connect Authentication Setup Guide

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JWT & OpenID Connect Authentication Setup Guide

Hey guys! Today, we're diving deep into setting up authentication in your application using JWT (JSON Web Tokens) and OpenID Connect. This setup ensures that your application only accepts tokens generated by a trusted OpenID provider and validates them using the provider's JWK (JSON Web Key) set. This is crucial for securing your application and ensuring that only authenticated users gain access.

Overview

Setting up authentication using JWT tokens and OpenID Connect might sound intimidating, but trust me, it's manageable once you break it down. The main idea is to ensure that your application trusts only the tokens issued by a known and reliable OpenID provider. We achieve this by validating the tokens against the provider's JWK set, which contains the public keys used to sign the tokens. This way, we can verify that the tokens haven't been tampered with and are indeed issued by the trusted provider.

Why JWT and OpenID Connect?

JWT is a standard for creating access tokens. These tokens contain information about the user and are digitally signed, ensuring their integrity. OpenID Connect is an authentication layer on top of OAuth 2.0 that allows clients to verify the identity of the end-user based on the authentication performed by an authorization server.

Using JWT with OpenID Connect gives us a secure and standardized way to handle authentication. The OpenID provider handles user authentication and issues JWTs, which our application then validates. This approach has several benefits:

  • Security: Tokens are digitally signed, preventing tampering.
  • Standardization: JWT and OpenID Connect are widely adopted standards.
  • Delegation: The authentication process is delegated to a trusted provider.
  • Flexibility: Supports various grant types and flows.

Tasks

To get this setup working, we need to accomplish a few key tasks:

  1. Integrate JWT Validation: We'll integrate JWT validation into our application's authentication logic. This involves writing code that intercepts incoming requests, extracts the JWT, and validates it.
  2. Validate Tokens with JWK Set: Ensure that the tokens are validated using the OpenID Connect provider's JWK set. This means fetching the JWK set and using it to verify the token's signature.
  3. Retrieve JWK Set: We'll retrieve the JWK set from the OpenID discovery endpoint. The discovery endpoint provides metadata about the OpenID provider, including the location of the JWK set.
  4. Keycloak Testcontainer: For local testing, we'll configure a Keycloak testcontainer with a test realm, client, and user. This allows us to test our authentication logic in a controlled environment.
  5. Reject Invalid Tokens: Implement logic to reject tokens that are not signed by a JWK from the provider's set. This is crucial for ensuring that only valid tokens are accepted.

Let's break down each of these tasks in more detail.

1. Integrate JWT Validation

The first step is to integrate JWT validation into your application's authentication logic. This typically involves adding middleware or interceptors that check for the presence of a JWT in the request headers. Once the JWT is found, it needs to be validated.

Here’s a basic outline of the process:

  1. Extract the JWT: Usually, the JWT is included in the Authorization header as a Bearer token. You'll need to extract this token from the header.
  2. Validate the JWT: Use a JWT library (like jjwt in Java or jsonwebtoken in Node.js) to validate the token. This involves verifying the signature, checking the expiration time, and ensuring that the issuer matches your trusted OpenID provider.
  3. Set Authentication Context: If the token is valid, set the authentication context in your application. This might involve creating a user object and storing it in the request context so that it can be accessed by subsequent handlers.

2. Validate Tokens with JWK Set

The JWK set is a crucial component of JWT validation. It contains the public keys that the OpenID provider uses to sign the JWTs. By validating the token's signature against these public keys, we can ensure that the token hasn't been tampered with.

Here's how you can validate tokens using the JWK set:

  1. Fetch the JWK Set: Retrieve the JWK set from the OpenID provider's discovery endpoint. This is typically a JSON document containing an array of JWKs.
  2. Identify the Key: Determine which key in the JWK set was used to sign the JWT. This is usually indicated by the kid (key ID) in the JWT header.
  3. Validate the Signature: Use the corresponding public key from the JWK set to validate the JWT's signature. The JWT library you're using should provide a method for this.

3. Retrieve JWK Set

The JWK set is typically exposed at a well-known endpoint, as defined by the OpenID Connect discovery specification. This endpoint is usually located at /.well-known/openid-configuration relative to the OpenID provider's base URL.

To retrieve the JWK set, you'll need to make an HTTP request to this endpoint and parse the JSON response. The response will contain a jwks_uri field, which points to the location of the JWK set.

Here's an example of how to retrieve the JWK set in Java:

import java.net.URL;
import java.net.URLConnection;
import java.io.InputStreamReader;
import com.google.gson.Gson;
import com.google.gson.JsonObject;

public class JWKFetcher {
    public static JsonObject fetchJWKSet(String discoveryEndpoint) throws Exception {
        URL url = new URL(discoveryEndpoint);
        URLConnection connection = url.openConnection();
        try (InputStreamReader reader = new InputStreamReader(connection.getInputStream())) {
            Gson gson = new Gson();
            return gson.fromJson(reader, JsonObject.class);
        }
    }

    public static void main(String[] args) throws Exception {
        String discoveryEndpoint = "https://your-openid-provider.com/.well-known/openid-configuration";
        JsonObject discoveryInfo = fetchJWKSet(discoveryEndpoint);
        String jwksUri = discoveryInfo.get("jwks_uri").getAsString();
        System.out.println("JWKS URI: " + jwksUri);
    }
}

4. Keycloak Testcontainer

For local testing, setting up a Keycloak testcontainer is an excellent way to simulate a real OpenID provider. Testcontainers provide lightweight, throwaway instances of common databases, servers, and services.

Here's how to set up a Keycloak testcontainer using Docker and JUnit:

  1. Add Dependencies: Add the Testcontainers and Keycloak dependencies to your project.

    <dependency>
    <groupId>org.testcontainers</groupId>
    <artifactId>testcontainers</artifactId>
    <version>1.16.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.testcontainers</groupId>
    <artifactId>keycloak</artifactId>
    <version>1.16.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-api</artifactId>
    <version>5.8.0</version>
    <scope>test</scope>
</dependency>

  2. Define the Testcontainer: Create a JUnit test class and define the Keycloak testcontainer.

    import org.junit.jupiter.api.Test;
import org.testcontainers.junit.jupiter.Container;
import org.testcontainers.junit.jupiter.Testcontainers;
import org.testcontainers.containers.GenericContainer;
import org.testcontainers.utility.DockerImageName;

@Testcontainers
public class KeycloakTest {

    @Container
    private static final GenericContainer keycloak = new GenericContainer(DockerImageName.parse("jboss/keycloak:15.0.2"))
            .withExposedPorts(8080)
            .withEnv("KEYCLOAK_USER", "admin")
            .withEnv("KEYCLOAK_PASSWORD", "admin");

    @Test
    public void testKeycloakIsRunning() {
        String address = "http://" + keycloak.getHost() + ":" + keycloak.getMappedPort(8080);
        System.out.println("Keycloak is running at: " + address);
        // Add your test logic here
    }
}

  3. Configure Keycloak: Use the Keycloak Admin REST API to create a test realm, client, and user. You can do this programmatically in your test setup.

5. Reject Invalid Tokens

Finally, it's crucial to implement logic to reject tokens that are not signed by a JWK from the provider's set. This prevents attackers from forging tokens and gaining unauthorized access.

Here's how you can reject invalid tokens:

  1. Verify Signature: Ensure that the JWT library you're using throws an exception or returns an error if the token's signature is invalid.
  2. Check Issuer: Verify that the iss (issuer) claim in the JWT matches your trusted OpenID provider's URL.
  3. Check Audience: Verify that the aud (audience) claim in the JWT includes your application's client ID.
  4. Check Expiration: Ensure that the exp (expiration) claim in the JWT is still in the future.

Acceptance Criteria

To ensure that our authentication setup is working correctly, we need to meet the following acceptance criteria:

  • [x] Application can retrieve the JWK set from an OpenID Connect provider's discovery endpoint.
  • [x] Only JWT tokens signed by a valid key from the discovery endpoint's JWK set are accepted.
  • [x] Integration test exists using a Keycloak testcontainer, a test client, and a test user.
  • [x] Invalid, unsigned, or otherwise manipulated tokens are rejected.
  • [x] Documentation provided for configuring the authentication settings and setting up the local test environment.

Conclusion

Setting up authentication with JWT and OpenID Connect can seem daunting, but by breaking it down into smaller tasks, it becomes much more manageable. By following the steps outlined in this guide, you can ensure that your application is secure and that only authenticated users can access your resources. Remember to test your setup thoroughly and to provide clear documentation for configuring the authentication settings.

Hope this helps you guys get your authentication setup rock solid! If you have any questions, feel free to ask!