Table of Contents

Secure a Micronaut application with an OCI Identity Domain using idtoken authentication

Learn how to create a Micronaut application and secure it with an OCI (Oracle Cloud Infrastructure) Identity Domain.

Authors: Sergio del Amo

Micronaut Version: 4.9.1

1. Getting Started

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

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. Oracle Cloud Identity Domain

To provide authentication, sign in to your Oracle Cloud account and create an Identity Domains.

Copy the domain URL from the Identity Domain page. Obtain the client ID and Client secret from the Integrated applications / OAuth Configuration section.

Define the following environment variables:

export OAUTH_CLIENT_ID=XXXXXXXXXX
export OAUTH_CLIENT_SECRET=YYYYYYYYYY
export OAUTH_ISSUER=https://idcs-xxx.identity.oraclecloud.com/

4.1. OAuth 2.0 Authorization Code Flow

We want to use an Authorization Code grant type flow which it 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=java
If you don’t specify the --build argument, Gradle with the Kotlin DSL 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.

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. OAuth 2.0

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")

6.1.1. OAuth 2.0 Configuration

Add the following OAuth2 Configuration:

src/main/resources/application.properties
(1)
micronaut.security.authentication=idtoken
(2)
(3)
micronaut.security.oauth2.clients.oci.client-id=${OAUTH_CLIENT_ID:XXX}
(4)
micronaut.security.oauth2.clients.oci.client-secret=${OAUTH_CLIENT_SECRET:YYY}
(5)
micronaut.security.oauth2.clients.oci.openid.issuer=${OAUTH_ISSUER}
(6)
micronaut.security.endpoints.logout.get-allowed=true
1 Set micronaut.security.authentication as idtoken. The idtoken provided by oci 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 oci. JWKS is exposed by the jws-uri entry of oci .well-known/openid-configuration.
2 The provider identifier must match the last part of the URL you entered as a redirect URL: /oauth/callback/oci.
3 Client ID. You can obtain it in the Oracle Cloud Console: Identity Domain / Integrated applications / OAuth Configuration section.
4 Client Secret. You can obtain it in the Oracle Cloud Console: Identity Domain / Integrated applications / OAuth Configuration section.
5 issuer URL. It allows the Micronaut framework to discover the configuration of the OpenID Connect server.
6 Accept GET request to the /logout endpoint.
OpenID Auto Configuration

Upon application startup, the Micronaut application visits the OpenID discovery endpoint to configure your application. if you set micronaut.security.oauth2.clients.oci.openid.issuer to https://idcs-xxx.identity.oraclecloud.com/, Micronaut visits https://idcs-xxx.identity.oraclecloud.com/.well-known/openid-configuration on startup.

Scopes Configuration

If you want to consider the Identity Domain User groups as your application roles, you can request the get_groups scope:

src/main/resources/application.properties
micronaut.security.token.roles-name=groups
micronaut.security.oauth2.clients.oci.scopes[0]=openid
micronaut.security.oauth2.clients.oci.scopes[1]=profile
micronaut.security.oauth2.clients.oci.scopes[2]=email
micronaut.security.oauth2.clients.oci.scopes[3]=get_groups

Oracle Cloud Infrastructure IAM Identity Domain OAuth and OpenID Connect Flows and Best Practices

When you’re using an OpenID Connect flow, often there’s a need for the application to get user groups. In OCI IAM, you can request groups as part of the ID token or get an access token that’s eligible to fetch user groups. When you request scope=get_groups in a request to the authorization endpoint, OCI IAM returns the user groups as part of the ID token, which increases the size of the ID token. An alternative is to use scope=groups, which allows the returned access token to get user groups from the userinfo endpoints. So, scope=get_groups saves an API call but increases the ID token size.

You can create a bean replacement for a bean of type RolesFinder, to consider the user groups as roles:

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

import io.micronaut.context.annotation.Replaces;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.annotation.Nullable;
import io.micronaut.core.util.StringUtils;
import io.micronaut.json.JsonMapper;
import io.micronaut.security.token.RolesFinder;
import io.micronaut.security.token.config.TokenConfiguration;
import jakarta.inject.Singleton;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

@Singleton (1)
@Replaces(RolesFinder.class)
public class IdentityDomainRolesFinder implements RolesFinder {
    private static final String KEY_NAME = "name";
    private final TokenConfiguration tokenConfiguration;

    public IdentityDomainRolesFinder(TokenConfiguration tokenConfiguration,
                                     JsonMapper jsonMapper) {
        this.tokenConfiguration = tokenConfiguration;
    }

    @Override
    public @NonNull List<String> resolveRoles(@Nullable Map<String, Object> attributes) {
        if (!attributes.containsKey(tokenConfiguration.getRolesName())) {
            return Collections.emptyList();
        }
        Object obj = attributes.get(tokenConfiguration.getRolesName());
        if (obj == null) {
            return Collections.emptyList();
        }
        if (obj instanceof Iterable objIterable) {
            List<String> roles = new ArrayList<>();
            for(Object o : objIterable) {
                if (o instanceof Map m) {
                    Object name = m.get(KEY_NAME);
                    if (name != null) {
                        String nameValue = name.toString();
                        if (StringUtils.isNotEmpty(nameValue)) {
                            roles.add(nameValue);
                        }
                    }
                }
            }
            return roles;
        }
        return Collections.emptyList();
    }
}
1 Use jakarta.inject.Singleton to designate a class as a singleton.

6.2. Home

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/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 to use to render the response.
4 The @Get annotation maps 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 - OCI Identity Domain example</h1>

<h2 th:if="${security}">username: <span th:text="${security.name}"></span></h2>
<h2 th:unless="${security}">username: Anonymous</h2>

<nav>
    <ul>
        <li th:unless="${security}"><a href="/oauth/login/oci">Enter</a></li>
        <li th:if="${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.

oraclecloudidentitydomain

8. Generate a Micronaut Application Native Executable with GraalVM

We will use GraalVM, an advanced JDK with ahead-of-time Native Image compilation, to generate a native executable of this Micronaut application.

Compiling Micronaut applications ahead of time with GraalVM significantly improves startup time and reduces the memory footprint of JVM-based applications.

Only Java and Kotlin projects support using GraalVM’s native-image tool. Groovy relies heavily on reflection, which is only partially supported by GraalVM.

8.1. GraalVM Installation

The easiest way to install GraalVM on Linux or Mac is to use SDKMan.io.

Java 21
sdk install java 21.0.5-graal

For installation on Windows, or for a manual installation on Linux or Mac, see the GraalVM Getting Started documentation.

The previous command installs Oracle GraalVM, which is free to use in production and free to redistribute, at no cost, under the GraalVM Free Terms and Conditions.

Alternatively, you can use the GraalVM Community Edition:

Java 21
sdk install java 21.0.2-graalce

8.2. Native Executable Generation

To generate a native executable using Gradle, run:

./gradlew nativeCompile

The native executable is created in build/native/nativeCompile directory and can be run with build/native/nativeCompile/micronautguide.

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

build.gradle
graalvmNative {
    binaries {
        main {
            imageName.set('mn-graalvm-application') (1)
            buildArgs.add('-Ob') (2)
        }
    }
}
1 The native executable name will now be mn-graalvm-application
2 It is possible to pass extra build arguments to native-image. For example, -Ob enables the quick build mode.

After you execute the native executable, navigate to localhost:8080 and authenticate with Cognito.

8.3. Cleanup

Once you are done with this guide, delete the Oracle Cloud resources created (Identity Domains, Users) to avoid incurring unnecessary charges.

9. Next steps

Read Micronaut OAuth 2.0 documentation to learn more.

10. Help with the Micronaut Framework

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

11. 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…​).