Implementing OAuth2 Introspection Endpoint with Spring Boot and Spring Security

Hello, Spring enthusiasts! 👋 Today, we’re going to explore how to implement an OAuth2 Introspection Endpoint using Spring Boot and Spring Security. This endpoint is essential for validating the status and metadata of OAuth2 tokens, ensuring that clients can verify the validity of tokens before using them to access protected resources.

Understanding the OAuth2 Introspection Endpoint

The OAuth2 Introspection Endpoint is a standardized URL where clients can send token introspection requests. This endpoint returns information about the token, such as its active status, expiration time, and associated scopes. By implementing this endpoint, you enable clients to securely validate tokens and ensure they are still valid and authorized for use.

Steps to Implement the Introspection Endpoint

Set Up the Spring Boot Project: Start by creating a new Spring Boot project with the necessary dependencies.
Configure Security: Set up Spring Security to handle OAuth2 authentication and authorization.
Create the Introspection Endpoint: Implement the endpoint to handle token introspection requests.
Handle Token Introspection Logic: Write the logic to validate the token and return its metadata.
Test the Endpoint: Ensure the endpoint works correctly by testing it with various scenarios.

Step 1: Set Up the Spring Boot Project

First, create a new Spring Boot project using Spring Initializr or your favorite IDE. Add the following dependencies:

Spring Web
Spring Security
Spring Security OAuth2 Resource Server
Spring Security OAuth2 Authorization Server

Step 2: Configure Security

In your application.yml or application.properties, configure the security settings:


spring:
  security:
    oauth2:
      resourceserver:
        jwt:
          issuer-uri: https://your-issuer-uri

Step 3: Create the Introspection Endpoint

Create a new controller to handle the token introspection requests:


import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TokenIntrospectionController {

    @PostMapping("/oauth2/token/introspect")
    public TokenIntrospectionResponse introspectToken(@RequestBody TokenIntrospectionRequest request) {
        // Implement token introspection logic here
        return new TokenIntrospectionResponse(true, "user", "read write", 3600);
    }
}

Step 4: Handle Token Introspection Logic

Implement the logic to validate the token and return its metadata:


import org.springframework.security.oauth2.jwt.JwtDecoder;
import org.springframework.security.oauth2.jwt.Jwt;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class TokenIntrospectionService {

    @Autowired
    private JwtDecoder jwtDecoder;

    public TokenIntrospectionResponse introspectToken(String token) {
        try {
            Jwt jwt = jwtDecoder.decode(token);
            // Validate the token and extract metadata
            boolean active = true; // Add your validation logic here
            String username = jwt.getSubject();
            String scopes = String.join(" ", jwt.getClaimAsStringList("scope"));
            long expiresIn = jwt.getExpiresAt().getEpochSecond() - System.currentTimeMillis() / 1000;
            return new TokenIntrospectionResponse(active, username, scopes, expiresIn);
        } catch (Exception e) {
            return new TokenIntrospectionResponse(false, null, null, 0);
        }
    }
}

Step 5: Test the Endpoint

Use tools like Postman or curl to test the endpoint. Ensure that the token introspection works as expected and handles various scenarios, such as valid and invalid tokens, expired tokens, and tokens with different scopes.

Conclusion

Implementing an OAuth2 Introspection Endpoint in Spring Boot with Spring Security enhances your application's security by allowing clients to validate tokens before using them. By following these steps, you can efficiently manage token introspection and ensure secure communication between clients and your server. Happy coding! 🚀

Hope this helps you in your Spring journey! Keep exploring and coding. 😊

OAuth2 Introspection Endpoint with Spring Boot