Table of Contents

Secure a Micronaut app with Okta

Learn how to create Micronaut app and secure it with an Authorization Server provided by Okta.

Authors: Sergio del Amo

Micronaut Version: 2.5.0

1. Getting Started

In this guide we are going to create a Micronaut app written in Java.

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

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

mn create-app example.micronaut.micronautguide --build=gradle --lang=java
If you don’t specify the --build argument, Gradle is used as a build tool.
If you don’t specify the --lang argument, Java is used as a language.

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

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

annotationprocessorsintellij

4.1. Views

Although Micronaut is primarily designed around message encoding / decoding, there are occasions where it is convenient to render a view on the server side.

To use 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")

4.2. OAuth 2.0

Sign up at developer.okta.com and create a Web app with the following characteristics:

okta app

To use OAuth 2.0 integration, add the next dependency:

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

Add also JWT Micronaut’s JWT support dependencies:

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

Add the following Oauth2 Configuration:

src/main/resources/application.yml
  security:
    authentication: idtoken (1)
    oauth2:
      clients:
        okta: (2)
          client-secret: '${OAUTH_CLIENT_SECRET:yyy}' (3)
          client-id: '${OAUTH_CLIENT_ID:xxx}' (4)
          openid:
            issuer: '${OIDC_ISSUER_DOMAIN:`https://dev-XXXXX.oktapreview.com`}/oauth2/${OIDC_ISSUER_AUTHSERVERID:default}' (5)
    endpoints:
      logout:
        get-allowed: true (6)
1 Set micronaut.security.authentication as idtoken. The idtoken provided by Okta 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, Micronaut extracts the JWT from the Cookie and validates the JWT signature with the remote Json Web Key Set exposed by Okta. JWKS is exposed by the jws-uri entry of Okta .well-known/openid-configuration
2 The provider identifier should match the last part of the url you entered as a redirect url /oauth/callback/okta
3 Client Secret. See previous screenshot.
4 Client ID. See previous screenshot.
5 issuer url. It allows micronaut to discover the configuration of the OpenID Connect server.
6 Accept GET request to the /logout endpoint.

The previous configuration uses several placeholders. You will need to setup OAUTH_CLIENT_ID, OAUTH_CLIENT_SECRET, OIDC_ISSUER_DOMAIN and OIDC_ISSUER_AUTHSERVERID environment variables.

export OAUTH_CLIENT_ID=XXXXXXXXXX
export OAUTH_CLIENT_SECRET=YYYYYYYYYY
export OIDC_ISSUER_DOMAIN=https://dev-XXXXX.oktapreview.com
export OIDC_ISSUER_AUTHSERVERID=default

Check OKTA .well-known/openid-configuration documentation.

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

diagramm

4.3. Home

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

src/main/java/example/micronaut/HomeController.java
package example.micronaut;

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;

import java.util.HashMap;
import java.util.Map;

@Controller (1)
public class HomeController {

    @Secured(SecurityRule.IS_ANONYMOUS) (2)
    @View("home") (3)
    @Get (4)
    public Map<String, Object> index() {
        return new HashMap<>();
    }
}
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 would you like to render the response against.
4 The @Get annotation is used to map the index method to GET / requests.

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 - Okta 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="${security}"><a href="/oauth/login/okta">Enter</a></li>
        <li th:if="${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.

5. Running the Application

To run the application use the ./gradlew run command which will start the application on port 8080.

oktavideo

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 Gradle run:

$ ./gradlew nativeImage

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

It is also possible to customize the name of the native image or pass additional parameters to GraalVM:

build.gradle
nativeImage {
    args('--verbose')
    imageName('mn-graalvm-application') (1)
}
1 The native image name will now be mn-graalvm-application

After you execute the native image, navigate to localhost:8080 and authenticate with Okta.

7. Next steps

Read Micronaut OAuth 2.0 documentation to learn more.

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.