Spring Boot 2 native approach to SSO with OAuth 2/OpenID Connect

This post is the final part of a 3 post series exploring ways to enable SSO with an OAuth2 provider for Spring Boot 2 based applications. The 3 posts are:

1. Ways to bootstrap an OpenID Connect compliant OAuth2 Authorization Server/OpenID Provider
2. Legacy Spring Boot/Spring 5 approach to integrating with an OAuth2 Authorization Server/OpenID Provider
3. Newer Spring Boot 2/Spring 5 approach to integrating with an OAuth2 Authorization Server/OpenID Connect Provider - this post

This post will explore the shiny new way to enable SSO for a Spring Boot 2 application using the native OAuth2 support in Spring Security.

The post again assumes that everything described in the first post is completed.

Spring Boot 2 Auto-configuration

Spring Boot 2 provides an auto-configuration for native OAuth2 support in Spring Security ( see class org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientAutoConfiguration).
The auto-configuration is activated by the presence of "spring-security-oauth2-client" library available via the following gradle coordinates:

compile "org.springframework.security:spring-security-oauth2-client"

This auto-configuration works off a set of properties, for the UAA Identity provider that has been started up, the set of properties are the following:

uaa-base-url: http://localhost:8080/uaa

spring:
  security:
    oauth2:
      client:
        registration:
          uaa:
            client-id: client1
            client-secret: client1
            authorizationGrantType: authorization_code
            redirect_uri_template: "{baseUrl}/login/oauth2/code/{registrationId}"
            scope: resource.read,resource.write,openid,profile
            clientName: oauth2-sample-client
        provider:
          uaa:
            token-uri: ${uaa-base-url}/oauth/token
            authorization-uri: ${uaa-base-url}/oauth/authorize
            user-info-uri: ${uaa-base-url}/userinfo
            jwk-set-uri: ${uaa-base-url}/token_keys
            userNameAttribute: user_name

If I were to depend on Spring Boot 2 auto-configuration support for native OAuth2 support to do its magic and were to start the application up, I would be presented with this page on accessing the application:

Note that this login page is a default page created by Spring Security OAuth2 and by default presents the list of registrations.

Clicking on "oauth2-sample-client" presents the login page of the Identity provider, UAA in this instance:

For an OpenID Connect based flow, applications are issued an ID Token along with an Access Token which I am decoding and presenting on a page:

Customizations

One of the quick customizations that I want to make is to redirect to UAA on access of any secured page specified via a "/secured" uri pattern, the following is a set of configuration that should enable this:

package sample.oauth2.config

import org.springframework.context.annotation.Configuration
import org.springframework.security.config.annotation.web.builders.HttpSecurity
import org.springframework.security.config.annotation.web.builders.WebSecurity
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter

@Configuration
class OAuth2SecurityConfig : WebSecurityConfigurerAdapter() {
    override fun configure(web: WebSecurity) {
        super.configure(web)
        web.ignoring()
                .mvcMatchers(
                        "/favicon.ico",
                        "/webjars/**",
                        "/css/**"
                )
    }

    override fun configure(http: HttpSecurity) {
        http.csrf().disable()

        http.authorizeRequests()
                .antMatchers("/secured/**")
                    .authenticated()
                .antMatchers("/", "/custom_login")
                    .permitAll()
                .anyRequest()
                    .authenticated()
                .and()
                    .oauth2Login()
                    .loginPage("/custom_login")
    }
}

See the "/custom_login" being set as the URI above, which in turn simply hands over control to OAuth2 controlled endpoints which know to set the appropriate parameters and redirect to UAA:

@Controller
class LoginController {

    @RequestMapping("/custom_login")
    fun loginPage(): String {
        return "redirect:/oauth2/authorization/uaa"
    }
}

This concludes the exploration of native OAuth2 support in Spring Boo2 applications.

All of the samples are available in my github repo - https://github.com/bijukunjummen/oauth2-boot2


The following references were helpful in understanding the OAuth2 support:

1. Spring Security Documentation - https://docs.spring.io/spring-security/site/docs/current/reference/html/
2. Joe Grandja's Spring One Platform 2017 Presentation - https://www.youtube.com/watch?v=WhrOCurxFWU