Implementing OAuth2 Authorization Code Grant Flow with Spring Boot and Spring Security

Hello, Spring enthusiasts! 👋 Today, we’re going to explore how to implement an OAuth2 Authorization Code Grant Flow using Spring Boot and Spring Security. This flow is one of the most commonly used OAuth2 flows and is ideal for web applications where the client can securely store the client secret.

Understanding OAuth2 Authorization Code Grant Flow

The OAuth2 Authorization Code Grant Flow involves two main steps:

Authorization Request: The client directs the user to the authorization server, where the user logs in and consents to the requested scopes. The authorization server then redirects the user back to the client with an authorization code.
Token Request: The client exchanges the authorization code for an access token by making a request to the authorization server's token endpoint.

Steps to Implement the Authorization Code Grant Flow

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 Authorization Server: Configure the authorization server to manage client registrations and token issuance.
Create the Authorization Endpoint: Implement the endpoint to handle authorization requests.
Create the Token Endpoint: Implement the endpoint to handle token requests.
Test the Flow: Ensure the flow works correctly by testing it with various clients.

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:
      authorizationserver:
        issuer-uri: https://your-issuer-uri

Step 3: Create the Authorization Server

Create a configuration class to set up the authorization server:


import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableAuthorizationServer;
import org.springframework.security.oauth2.config.annotation.web.configuration.AuthorizationServerConfigurerAdapter;
import org.springframework.security.oauth2.config.annotation.web.configurers.AuthorizationServerEndpointsConfigurer;
import org.springframework.security.oauth2.config.annotation.web.configurers.AuthorizationServerSecurityConfigurer;
import org.springframework.security.oauth2.provider.token.TokenStore;
import org.springframework.security.oauth2.provider.token.store.InMemoryTokenStore;

@Configuration
@EnableAuthorizationServer
public class AuthorizationServerConfig extends AuthorizationServerConfigurerAdapter {

    @Bean
    public TokenStore tokenStore() {
        return new InMemoryTokenStore();
    }

    @Override
    public void configure(AuthorizationServerSecurityConfigurer security) throws Exception {
        security.tokenKeyAccess("permitAll()").checkTokenAccess("isAuthenticated()");
    }

    @Override
    public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
        clients.inMemory()
            .withClient("client-id")
            .secret("{noop}client-secret")
            .authorizedGrantTypes("authorization_code")
            .scopes("read", "write")
            .redirectUris("https://your-redirect-uri");
    }

    @Override
    public void configure(AuthorizationServerEndpointsConfigurer endpoints) throws Exception {
        endpoints.tokenStore(tokenStore());
    }
}

Step 4: Create the Authorization Endpoint

Create a new controller to handle the authorization requests:


import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AuthorizationController {

    @GetMapping("/oauth2/authorize")
    public AuthorizationResponse authorize(@RequestParam String responseType,
                                           @RequestParam String clientId,
                                           @RequestParam String redirectUri,
                                           @RequestParam String scope,
                                           @RequestParam String state) {
        // Implement authorization logic here
        return new AuthorizationResponse(authorizationCode);
    }
}

Step 5: Create the Token Endpoint

Create a new controller to handle the token 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 TokenController {

    @PostMapping("/oauth2/token")
    public TokenResponse exchangeCode(@RequestBody TokenRequest request) {
        // Implement token exchange logic here
        return new TokenResponse(accessToken, refreshToken, expiresIn);
    }
}

Step 6: Test the Flow

Use tools like Postman or curl to test the flow. Ensure that the authorization code grant flow works as expected and handles various scenarios, such as valid and invalid authorization codes, expired codes, and successful token exchanges.

Conclusion

Implementing an OAuth2 Authorization Code Grant Flow in Spring Boot with Spring Security enhances your application's security by allowing clients to securely obtain access tokens. By following these steps, you can efficiently manage the authorization process and ensure secure communication between clients and your server. Happy coding! 🚀

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

OAuth2 Authorization Code Grant Flow with Spring Boot