How do you implement OAuth 2.0 authentication for REST APIs in Spring Boot?

Table of Contents

• Introduction
• Steps to Implement OAuth 2.0 Authentication in Spring Boot
  • 1. Add Dependencies
  • 2. Configure OAuth 2.0 Client in **application.yml**
  • 3. Configure Spring Security for OAuth 2.0
  • 4. Handle the OAuth2 Login Callback
    • Example: Accessing the Authenticated User’s Details
  • 5. Configure Resource Server (Optional)
• Conclusion

Introduction

OAuth 2.0 is a widely used authorization framework that allows third-party applications to access user resources without exposing user credentials. It is commonly used to secure REST APIs in modern applications. In Spring Boot, OAuth 2.0 authentication can be easily implemented using Spring Security, providing a secure and flexible way to protect resources. This guide will walk you through how to implement OAuth 2.0 authentication for REST APIs in Spring Boot.

Steps to Implement OAuth 2.0 Authentication in Spring Boot

1. Add Dependencies

First, you need to add the necessary dependencies for OAuth 2.0 and Spring Security. In your pom.xml file, add the following dependencies:

The spring-boot-starter-oauth2-client dependency is used for OAuth 2.0 client support, and spring-boot-starter-security enables Spring Security.

2. Configure OAuth 2.0 Client in **application.yml**

In the configuration file application.yml or application.properties, set up the OAuth 2.0 client configuration. This includes the authorization server details, such as the authorization URI, token URI, and client credentials.

In this example, we configure Google as the OAuth 2.0 provider. You would replace YOUR_CLIENT_ID and YOUR_CLIENT_SECRET with the credentials you obtain from the OAuth provider (e.g., Google, GitHub).

3. Configure Spring Security for OAuth 2.0

Spring Security needs to be configured to secure the REST APIs with OAuth 2.0. For OAuth 2.0 authentication, you can use the OAuth2LoginAuthenticationFilter and configure the security settings in SecurityConfig.java.

In this example, we allow public access to the login and error endpoints, while all other requests require authentication via OAuth 2.0.

4. Handle the OAuth2 Login Callback

When a user successfully authenticates through the OAuth 2.0 provider, the authorization server will redirect back to the application with the authorization code. Spring Boot handles the token exchange and login process automatically. You can access the authenticated user's details through the OAuth2AuthenticationToken class.

Example: Accessing the Authenticated User’s Details

In this example, the @AuthenticationPrincipal annotation is used to inject the authenticated user's details. You can access any attributes returned by the OAuth provider, such as the user's name or email.

5. Configure Resource Server (Optional)

If your application acts as a resource server (e.g., using JWT tokens to access protected resources), you will need to configure Spring Security to validate the tokens.

Conclusion

Implementing OAuth 2.0 authentication in Spring Boot is straightforward, thanks to Spring Security and the spring-boot-starter-oauth2-client dependency. By configuring the OAuth 2.0 client in application.yml and securing your API endpoints with Spring Security, you can quickly add secure authentication to your REST APIs. Additionally, you can access the authenticated user's details and handle tokens efficiently for both client and resource server configurations. This ensures that your APIs are securely protected while enabling smooth integration with popular OAuth 2.0 providers like Google, GitHub, and others.