Table of Contents

Secure a Micronaut application with Auth0

Learn how to create a Micronaut application and secure it with an Authorization Server provided by Auth0.

Authors: Sergio del Amo

Micronaut Version: 4.4.1

1. Getting Started

In this guide, we will create a Micronaut application written in Groovy.

2. What you will need

To complete this guide, you will need the following:

3. Solution

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

4. OAuth 2.0

To provide authentication, sign in to your Auth0 account.

Create an Application

auth0 create application

Fill the Application URIs:

auth0 application uris

  • Enter http://localhost:8080/oauth/callback/auth0 as callback URL.

  • Enter http://localhost:8080/logout as allowed logout URL.

  • Enter http://localhost:8080 as allowed web origins.

Once you have an HTTPS domain (e.g. https://myapp.org), enter it as Application Login URI: https://myapp.org/oauth/login/auth0.

You can obtain the application’s domain, client id, and secret in the Auth0 console.

auth0 clientid clientsecret

We want to use an Authorization Code grant type flow, which is described in the following diagram:

diagramm

5. Writing the Application

Create an application using the Micronaut Command Line Interface or with Micronaut Launch.

mn create-app example.micronaut.micronautguide --build=gradle --lang=groovy
If you don’t specify the --build argument, Gradle is used as the build tool.
If you don’t specify the --lang argument, Java is used as the language.
If you don’t specify the --test argument, JUnit is used for Java and Kotlin, and Spock is used for Groovy.

The previous command creates a Micronaut application with the default package example.micronaut in a directory named micronautguide.

Setup IntelliJ IDEA to develop Micronaut Applications.

5.1. Dependencies

To use OAuth 2.0 integration, add the following dependency:

build.gradle
implementation("io.micronaut.security:micronaut-security-oauth2")

Also add Micronaut JWT support dependencies:

build.gradle
implementation("io.micronaut.security:micronaut-security-jwt")

5.2. Configuration

Add the following OAuth2 Configuration:

Since Micronaut Framework 4.0, to use YAML configuration, you have to add the YAML dependency.
src/main/resources/application.yml
  security:
    authentication: idtoken (1)
    oauth2:
      clients:
        auth0: (2)
          client-id: '${OAUTH_CLIENT_ID:xxx}' (3)
          client-secret: '${OAUTH_CLIENT_SECRET:yyy}' (4)
          openid:
            issuer: 'https://${OAUTH_DOMAIN:micronautguides.eu.auth0.com}/' (5)
    endpoints:
      logout:
        get-allowed: true (6)
1 Set micronaut.security.authentication as idtoken. The idtoken provided by Auth0 when the OAuth 2.0 Authorization code flow ends will be saved in a cookie. The id token is a signed JWT. For every request, the Micronaut framework extracts the JWT from the Cookie and validates the JWT signature with the remote Json Web Key Set exposed by Auth0. JWKS is exposed by the jws-uri entry of Auth0 .well-known/openid-configuration.
2 The provider identifier must match the last part of the URL you entered as a redirect URL: /oauth/callback/auth0.
3 Client ID. See previous screenshot.
4 Client Secret. See previous screenshot.
5 issuer URL. It allows the Micronaut framework to discover the configuration of the OpenID Connect server. Note: we will use the application’s domain.
6 Accept GET request to the /logout endpoint.

When you start the Micronaut application, it fetches the Auth0 application’s openidconfiguration:

https://{auth0domain}/.well-known/openid-configuration

The previous configuration uses several placeholders. You will need to set up OAUTH_CLIENT_ID, OAUTH_CLIENT_SECRET, and OAUTH_DOMAIN environment variables.

export OAUTH_CLIENT_ID=XXXXXXXXXX
export OAUTH_CLIENT_SECRET=YYYYYYYYYY
export OAUTH_DOMAIN=micronautguides.eu.auth0.com

6. Views

To use the Thymeleaf Java template engine to render views in a Micronaut application, add the following dependency on your classpath.

build.gradle
implementation("io.micronaut.views:micronaut-views-thymeleaf")

6.1. Home controller

Create a controller to handle the requests to /. You will display the email of the authenticated person if any. Annotate the controller endpoint with @View, since we will use a Thymeleaf template.

src/main/groovy/example/micronaut/HomeController.groovy
package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import io.micronaut.security.annotation.Secured
import io.micronaut.security.rules.SecurityRule
import io.micronaut.views.View

@CompileStatic
@Controller (1)
class HomeController {

    @Secured(SecurityRule.IS_ANONYMOUS) (2)
    @View('home') (3)
    @Get (4)
    Map<String, Object> index() {
        [:]
    }
}
1 The class is defined as a controller with the @Controller annotation mapped to the path /.
2 Annotate with io.micronaut.security.Secured to configure secured access. The SecurityRule.IS_ANONYMOUS expression will allow access without authentication.
3 Use View annotation to specify which template to use to render the response.
4 The @Get annotation maps the index method to an HTTP GET request on /.

6.2. Thymeleaf template

Create a Thymeleaf template:

src/main/resources/views/home.html
<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Home</title>
</head>
<body>
<h1>Micronaut - Auth0 example</h1>

<h2 th:if="${security}">username: <span th:text="${security.attributes.get('email')}"></span></h2>
<h2 th:unless="${security}">username: Anonymous</h2>

<nav>
    <ul>
        <li th:unless="${security}"><a href="/oauth/login/auth0">Enter</a></li>
        <li th:if="${security}"><a href="/oauth/logout">Logout</a></li>
    </ul>
</nav>
</body>
</html>

Also, note that we return an empty model in the controller. However, we are accessing security in the Thymeleaf template.

7. Running the Application

To run the application, use the ./gradlew run command, which starts the application on port 8080.

auth0video

8. Next steps

Read Micronaut OAuth 2.0 documentation to learn more.

9. Help with the Micronaut Framework

The Micronaut Foundation sponsored the creation of this Guide. A variety of consulting and support services are available.

10. License

All guides are released with an Apache license 2.0 license for the code and a Creative Commons Attribution 4.0 license for the writing and media (images…​).