Table of Contents

Micronaut Token Propagation

Learn how to leverage token propagation in Micronaut to simplify your code while keeping your microservices secure.

Authors: Sergio del Amo

Micronaut Version: 2.5.0

1. Getting Started

Let’s describe the microservices you are going to build through the tutorial.

  • gateway - A secured via JWT microservice which exposes an endpoint /user. The output of that endpoint is the result of consuming the userecho endpoint.

  • userecho - A secured via JWT microservice which exposes an endpoint /user which responds the username of the authenticated user.

The next diagram illustrates the flow:

tokenpropagation

We generate a valid JWT in the gateway microservice. Then every microservice in our app is able to validate this JWT. We want every internal request to contain a valid JWT token. If we want to talk to another microservice we need to propagate the valid JWT get received.

If you are using Java or Kotlin and IntelliJ IDEA, make sure you have enabled annotation processing.

annotationprocessorsintellij

2. What you will need

To complete this guide, you will need the following:

  • Some time on your hands

  • A decent text editor or IDE

  • JDK 1.8 or greater installed with JAVA_HOME configured appropriately

3. Solution

We recommend that you follow the instructions in the next sections and create the app step by step. However, you can go right to the completed example.

4. Writing the App

We are going to write the app first without token propagation. Then we are going to configure a token propagation, and you will see how much code we can get rid of.

4.1. Gateway

Create the microservice:

mn create-app example.micronaut.gateway --build=maven --lang=java

Add the security-jwt module to the configuration:

pom.xml
<!-- Add the following to your annotationProcessorPaths element -->
<path>
    <groupId>io.micronaut.security</groupId>
    <artifactId>micronaut-security-annotations</artifactId>
</path>
<dependency>
    <groupId>io.micronaut.security</groupId>
    <artifactId>micronaut-security-jwt</artifactId>
    <scope>compile</scope>
</dependency>

To keep this guide simple, create a naive AuthenticationProvider to simulate user’s authentication.

intermediate-gateway/src/main/java/example/micronaut/AuthenticationProviderUserPassword.java
package example.micronaut;

import io.micronaut.core.annotation.Nullable;
import io.micronaut.http.HttpRequest;
import io.micronaut.security.authentication.AuthenticationException;
import io.micronaut.security.authentication.AuthenticationFailed;
import io.micronaut.security.authentication.AuthenticationProvider;
import io.micronaut.security.authentication.AuthenticationRequest;
import io.micronaut.security.authentication.AuthenticationResponse;
import io.micronaut.security.authentication.UserDetails;
import io.reactivex.BackpressureStrategy;
import io.reactivex.Flowable;
import org.reactivestreams.Publisher;

import javax.inject.Singleton;
import java.util.Collections;

@Singleton (1)
public class AuthenticationProviderUserPassword implements AuthenticationProvider { (2)
    
    @Override
    public Publisher<AuthenticationResponse> authenticate(@Nullable HttpRequest<?> httpRequest, AuthenticationRequest<?, ?> authenticationRequest) {
        return Flowable.create(emitter -> {
            if ((authenticationRequest.getIdentity().equals("sherlock") || authenticationRequest.getIdentity().equals("watson")) &&
                    authenticationRequest.getSecret().equals("password")) {
                emitter.onNext(new UserDetails((String) authenticationRequest.getIdentity(), Collections.emptyList()));
                emitter.onComplete();
            } else {
                emitter.onError(new AuthenticationException(new AuthenticationFailed()));
            }

        }, BackpressureStrategy.ERROR);

    }
}
1 To register a Singleton in Micronaut’s application context, annotate your class with javax.inject.Singleton.
2 A Micronaut’s Authentication Provider implements the interface io.micronaut.security.authentication.AuthenticationProvider.

Create a class UserController which exposes /user endpoint.

intermediate-gateway/src/main/java/example/micronaut/UserController.java
package example.micronaut;

import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Header;
import io.micronaut.http.annotation.Produces;
import io.micronaut.security.annotation.Secured;
import io.micronaut.security.rules.SecurityRule;
import io.reactivex.Single;

@Controller("/user") (1)
public class UserController {

    private final UsernameFetcher usernameFetcher;

    public UserController(UsernameFetcher usernameFetcher) {  (2)
        this.usernameFetcher = usernameFetcher;
    }

    @Secured(SecurityRule.IS_AUTHENTICATED)  (3)
    @Produces(MediaType.TEXT_PLAIN) (4)
    @Get (5)
    Single<String> index(@Header("Authorization") String authorization) {  (6)
        return usernameFetcher.findUsername(authorization);
    }
}
1 Annotate with io.micronaut.http.annotation.Controller to designate a class as a Micronaut’s controller.
2 Constructor dependency injection
3 Annotate with io.micronaut.security.Secured to configure secured access. The isAuthenticated() expression will allow access only to authenticated users.
4 Since we return a string which is not valid JSON, set the media type to text/plain.
5 You can specify the HTTP verb that a controller’s action responds to. To respond to a GET request, use the io.micronaut.http.annotation.Get annotation.
6 You can bind an Http Header to a controller method argument.

Create an interface to encapsulate the collaboration with the userecho microservice.

intermediate-gateway/src/main/java/example/micronaut/UsernameFetcher.java
package example.micronaut;

import io.micronaut.http.annotation.Header;
import io.reactivex.Single;

public interface UsernameFetcher {
    Single<String> findUsername(@Header("Authorization") String authorization);
}

Create a Micronaut HTTP Declarative client:

intermediate-gateway/src/main/java/example/micronaut/UserEchoClient.java
package example.micronaut;

import io.micronaut.context.annotation.Requires;
import io.micronaut.context.env.Environment;
import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Consumes;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Header;
import io.micronaut.http.client.annotation.Client;
import io.reactivex.Single;

@Client(id = "userecho") (1)
@Requires(notEnv = Environment.TEST) (2)
public interface UserEchoClient extends UsernameFetcher {

    @Override
    @Consumes(MediaType.TEXT_PLAIN)
    @Get("/user") (3)
    Single<String> findUsername(@Header("Authorization") String authorization); (4)
}
1 The @Client annotation is used with a service id. We will reference the exact service id in the configuration shortly.
2 Don’t load this bean in the Test environment.
3 Use @Get annotation to define the client mapping
4 Supply the JWT to the HTTP Authorization header value to the @Client method.

Add this snippet to application.yml to configure the service url of the echo service

intermediate-gateway/src/main/resources/application.yml
micronaut:
  http:
    services:
      userecho: (1)
        urls:
          - "http://localhost:8081" (2)
1 This is the same service ID we used in the @Client annotation.
2 Configure a URL where the userecho microservice resides.

Add this snippet to application.yml to configure security:

intermediate-gateway/src/main/resources/application.yml
micronaut:
  security:
    authentication: bearer (1)
    token:
      jwt:
        signatures:
          secret:
            generator: (2)
              secret: '"${JWT_GENERATOR_SIGNATURE_SECRET:pleaseChangeThisSecretForANewOne}"' (3)
1 Set authentication to bearer to receive a JSON response from the login endpoint.
2 You can create a SecretSignatureConfiguration named generator via configuration as illustrated above. The generator signature is used to sign the issued JWT claims.
3 Change this by your own secret and keep it safe (do not store this in your VCS)

4.1.1. Tests

Provide a UsernameFetcher bean replacement for the Test environment.

intermediate-gateway/src/test/java/example/micronaut/UserEchoClientReplacement.java
package example.micronaut;

import io.micronaut.context.annotation.Requires;
import io.micronaut.context.env.Environment;
import io.micronaut.http.annotation.Header;
import io.reactivex.Single;

import javax.inject.Singleton;

@Requires(env = Environment.TEST)
@Singleton
public class UserEchoClientReplacement implements UsernameFetcher {

    @Override
    public Single<String> findUsername(@Header("Authorization") String authorization) {
        return Single.just("sherlock");
    }
}

Create a tests which verifies the app is secured and we can access it after login in:

intermediate-gateway/src/test/java/example/micronaut/UserControllerTest.java
package example.micronaut;

import io.micronaut.http.HttpRequest;
import io.micronaut.http.HttpStatus;
import io.micronaut.http.client.RxHttpClient;
import io.micronaut.http.client.annotation.Client;
import io.micronaut.http.client.exceptions.HttpClientResponseException;
import io.micronaut.security.authentication.UsernamePasswordCredentials;
import io.micronaut.security.token.jwt.render.BearerAccessRefreshToken;
import io.micronaut.test.extensions.junit5.annotation.MicronautTest;
import org.junit.jupiter.api.Test;

import javax.inject.Inject;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;

@MicronautTest (1)
public class UserControllerTest {

    @Inject
    @Client("/")
    RxHttpClient client; (2)

    @Test
    public void testUserEndpointIsSecured() { (3)
        HttpClientResponseException thrown = assertThrows(HttpClientResponseException.class, () -> {
            client.toBlocking().exchange(HttpRequest.GET("/user"));
        });

        assertEquals(HttpStatus.UNAUTHORIZED, thrown.getResponse().getStatus());
    }

    @Test
    public void testAuthenticatedCanFetchUsername() {
        UsernamePasswordCredentials credentials = new UsernamePasswordCredentials("sherlock", "password");
        HttpRequest request = HttpRequest.POST("/login", credentials);

        BearerAccessRefreshToken bearerAccessRefreshToken = client.toBlocking().retrieve(request, BearerAccessRefreshToken.class);

        String username = client.toBlocking().retrieve(HttpRequest.GET("/user")
                .header("Authorization", "Bearer " + bearerAccessRefreshToken.getAccessToken()), String.class);

        assertEquals("sherlock", username);
    }
}
1 Annotate the class with @MicronautTest to let Micronaut starts the embedded server and inject the beans. More info: https://micronaut-projects.github.io/micronaut-test/latest/guide/index.html.
2 Inject the RxHttpClient bean in the application context.
3 Test endpoint is secured

4.2. User echo

Create the microservice:

mn create-app example.micronaut.userecho --build=maven --lang=java

Add the security-jwt module to the configuration:

pom.xml
<!-- Add the following to your annotationProcessorPaths element -->
<path>
    <groupId>io.micronaut.security</groupId>
    <artifactId>micronaut-security-annotations</artifactId>
</path>
<dependency>
    <groupId>io.micronaut.security</groupId>
    <artifactId>micronaut-security-jwt</artifactId>
    <scope>compile</scope>
</dependency>

Create a class UserController which exposes /user endpoint.

intermediate-userecho/src/main/java/example/micronaut/UserController.java
package example.micronaut;

import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Produces;
import io.micronaut.security.annotation.Secured;
import io.micronaut.security.rules.SecurityRule;

import java.security.Principal;

@Controller("/user") (1)
public class UserController {

    @Secured(SecurityRule.IS_AUTHENTICATED) (2)
    @Produces(MediaType.TEXT_PLAIN) (3)
    @Get (4)
    String index(Principal principal) { (5)
        return principal.getName();
    }
}
1 Annotate with io.micronaut.http.annotation.Controller to designate a class as a Micronaut’s controller.
2 Annotate with io.micronaut.security.Secured to configure secured access. The isAuthenticated() expression will allow access only to authenticated users.
3 Since we return a string which is not valid JSON, set the media type to text/plain.
4 You can specify the HTTP verb that a controller’s action responds to. To respond to a GET request, use the io.micronaut.http.annotation.Get annotation.
5 If a user is authenticated, Micronaut will bind the user object to an argument of type java.security.Principal (if present).

Add this snippet to application.yml to fix the port where userecho starts:

intermediate-userecho/src/main/resources/application.yml
micronaut:
  server:
    port: 8081 (1)
1 Configure a fix port where the app listens.

Add this snippet to application.yml

intermediate-userecho/src/main/resources/application.yml
micronaut:
  security:
    token:
      jwt:
        signatures:
          secret:
            validation: (1)
              secret: '"${JWT_GENERATOR_SIGNATURE_SECRET:pleaseChangeThisSecretForANewOne}"' (2)
1 You can create a SecretSignatureConfiguration named validation which is able to validate JWT generated by the gateway microservice.
2 Change this by your own secret and keep it safe (do not store this in your VCS)

4.3. Token Propagation

As you can see propagating the JWT token to other microservices in our app complicates the code. We need to capture the Authorization header in the controller method arguments and then pass it to the @Client bean. In an app with several controllers and declarative clients, it can lead to a lot of repetition. Fortunately, Micronaut includes a feature called token propagation. We can tell our app to propagate the incoming token to a set of outgoing requests.

Let’s configure token propagation. We need to modify application.yml in the gateway microservice:

gateway/src/main/resources/application.yml
micronaut:
  security:
    token:
      propagation:
        enabled: true (1)
        service-id-regex: "userecho" (2)
1 Enable token propagation
2 We only want to propagate the token to certain services. We can create a regular expression to match those services ids.

We can simplify the code:

Edit UserController.java and remove the @Header parameter:

gateway/src/main/java/example/micronaut/UserController.java
package example.micronaut;

import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Produces;
import io.micronaut.security.annotation.Secured;
import io.micronaut.security.rules.SecurityRule;
import io.reactivex.Single;

@Controller("/user")
public class UserController {

    private final UsernameFetcher usernameFetcher;

    public UserController(UsernameFetcher usernameFetcher) {
        this.usernameFetcher = usernameFetcher;
    }

    @Secured(SecurityRule.IS_AUTHENTICATED)
    @Produces(MediaType.TEXT_PLAIN)
    @Get
    Single<String> index() {
        return usernameFetcher.findUsername();
    }
}

Edit UsernameFetcher.java and remove the @Header parameter:

gateway/src/main/java/example/micronaut/UsernameFetcher.java
package example.micronaut;

import io.reactivex.Single;

public interface UsernameFetcher {
    Single<String> findUsername();
}

Edit UserEchoClient.java and remove the @Header parameter:

gateway/src/main/java/example/micronaut/UserEchoClient.java
package example.micronaut;

import io.micronaut.context.annotation.Requires;
import io.micronaut.context.env.Environment;
import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Consumes;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.client.annotation.Client;
import io.reactivex.Single;

@Client(id = "userecho")
@Requires(notEnv = Environment.TEST)
public interface UserEchoClient extends UsernameFetcher {

    @Consumes(MediaType.TEXT_PLAIN)
    @Get("/user")
    Single<String> findUsername();
}

Edit UserEchoClientReplacement.java and remove the @Header parameter:

gateway/src/test/java/example/micronaut/UserEchoClientReplacement.java
package example.micronaut;

import io.micronaut.context.annotation.Requires;
import io.micronaut.context.env.Environment;
import io.reactivex.Single;

import javax.inject.Singleton;

@Requires(env = Environment.TEST)
@Singleton
public class UserEchoClientReplacement implements UsernameFetcher {

    @Override
    public Single<String> findUsername() {
        return Single.just("sherlock");
    }
}

5. Running the App

Run both microservices:

userecho $ ./mvnw mn:run
18:29:26.500 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 671ms. Server Running: http://localhost:8081
gateway $ ./mvnw mn:run
18:28:35.723 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 707ms. Server Running: http://localhost:8080

Send a curl request to authenticate:

curl -X "POST" "http://localhost:8080/login" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{"username": "sherlock", "password": "password"}'

response:

{"username":"sherlock","access_token":"eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJzaGVybG9jayIsIm5iZiI6MTYxNTkxMDM3Nywicm9sZXMiOltdLCJpc3MiOiJnYXRld2F5IiwiZXhwIjoxNjE1OTEzOTc3LCJpYXQiOjE2MTU5MTAzNzd9.nWoaNq9YzRzYKDBvDw_QaiUyVyIoc6rHCW_vLfnrtQ8","token_type":"Bearer","expires_in":3600}

Now you can call the /user endpoint supplying the access token in the Authorization header.

curl "http://localhost:8080/user" -H 'Authorization: Bearer eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJzaGVybG9jayIsIm5iZiI6MTYxNTkxMDM3Nywicm9sZXMiOltdLCJpc3MiOiJnYXRld2F5IiwiZXhwIjoxNjE1OTEzOTc3LCJpYXQiOjE2MTU5MTAzNzd9.nWoaNq9YzRzYKDBvDw_QaiUyVyIoc6rHCW_vLfnrtQ8'

sherlock

6. Generate a Micronaut app’s Native Image with GraalVM

We are going to use GraalVM, the polyglot embeddable virtual machine, to generate a Native image of our Micronaut application.

Native images compiled with GraalVM ahead-of-time improve the startup time and reduce the memory footprint of JVM-based applications.

Use of GraalVM’s native-image tool is only supported in Java or Kotlin projects. Groovy relies heavily on reflection which is only partially supported by GraalVM.

6.1. Native Image generation

The easiest way to install GraalVM is to use SDKMan.io.

# For Java 8
$ sdk install java 21.1.0.r8-grl

# For Java 11
$ sdk install java 21.1.0.r11-grl

You need to install the native-image component which is not installed by default.

$ gu install native-image

To generate a native image using Maven run:

$ ./mvnw package -Dpackaging=native-image

The native image will be created in target/application and can be run with ./target/application.

After creating the native images for both microservices, start them and send the same curl requests as before to check that everything works using GraalVM native images.

7. Next steps

Read more about Token Propagation and Security inside Micronaut.

8. Help with Micronaut

Object Computing, Inc. (OCI) sponsored the creation of this Guide. A variety of consulting and support services are available.

Meet the Team.