How To Implement SSO (Single Sign-on) in Your Application?

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When users juggle multiple accounts across various platforms, the demand for seamless authentication experiences has never been higher.

Single Sign-On (SSO) emerges as a solution, simplifying access management while enhancing security. For companies seeking to empower their applications with this functionality, understanding how to implement Single Sign On correctly is paramount.

In this comprehensive guide, we explore the benefits of Single Sign-On and best practices. We share our expertise on how to implement SSO.

Delve into the knowledge and tools necessary to understand how to implement SSO in web application seamlessly!

Understanding Single Sign-On

Single sign-on SSO is an authentication method that allows users to securely authenticate to multiple applications and sites using one set of credentials.

By allowing users to utilize a single set of credentials to access various services, Single Sign On implementation boosts user convenience and minimizes the need to remember multiple passwords. To enhance user experience and bolster security, developers can implement SSO for web applications.

With this technology, users can seamlessly access multiple web services with just one set of login credentials.

How Does SSO Work?

SSO is based on setting up a trust relationship between an application, known as a service provider, and an access control system, such as OneLogin. Such trust relationships are often based on the exchange of a certificate between the access control system and the service provider.

Such a certificate can be used to indicate identification information that is sent from the access control system to the service provider, so the service provider knows that the information comes from a trusted source. In SSO, identity data takes the form of tokens containing identifying values of user information such as email or username.

At its core, SSO authentication allows users to log in once and gain access to various systems without being prompted to log in again at each of them. This is achieved through a centralized authentication server that all applications trust. When an application requires authentication, it redirects the user to this server. If the user is already authenticated, the server redirects the user back to the application with an authentication token, typically a JSON Web Token (JWT).

Choosing an SSO Protocol

First of all, developers should decide on how to implement SSO login. This step involves configuring authentication protocols such as OAuth or SAML (Security Assertion Markup Language) to enable seamless access across multiple web applications. While SAML is widely used in enterprise environments, OAuth 2.0 is more prevalent in modern web applications due to its simplicity and flexibility.

Developers typically integrate their application with an identity provider (IdP) like Okta or Auth0, allowing users to authenticate once and gain access to all connected services without the need for separate logins.

Get tech insights from our blog post about OAuth 2.0 implementation!

Recommendations for Implementation

For most web-based applications, OAuth 2.0 is recommended due to its extensive support and adaptability to various use cases, including mobile and desktop applications. OAuth 2.0 also integrates well with OpenID Connect (OIDC), providing not just authorization but also authentication, making it a comprehensive solution for SSO.

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Technical Implementation Using Java

Integrating SSO into a Java application involves several key steps. The examples below illustrate how to implement SSO with a simplified version, focusing on OAuth 2.0 with OIDC for authentication.

Setting Up Dependencies

First, include the necessary dependencies in your project. For a Spring Boot application, Spring Security makes OAuth 2.0 integration straightforward:


<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-oauth2-client</artifactId>
</dependency>

Configuring OAuth 2.0

In the application.yml (or application.properties), configure the OAuth 2.0 details provided by the identity provider (IdP):


spring:
 security:
   oauth2:
     client:
       registration:
         google:
           clientId: [CLIENT-ID]
           clientSecret: [CLIENT-SECRET]
           scope: profile, email
       provider:
         google:
           authorization-uri: https://accounts.google.com/o/oauth2/auth
           token-uri: https://oauth2.googleapis.com/token
           user-info-uri: https://www.googleapis.com/oauth2/v3/userinfo
           user-name-attribute: sub

This example uses Google as the identity provider but can be adapted for any OAuth 2.0-compliant provider.

Securing Endpoints

Secure application endpoints by configuring security settings. Spring Security simplifies this with Java configuration:


@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

   @Override
   protected void configure(HttpSecurity http) throws Exception {
       http
           .authorizeRequests(authorizeRequests ->
               authorizeRequests
                   .antMatchers("/", "/home").permitAll()
                   .anyRequest().authenticated())
           .oauth2Login();
   }
}

This configuration ensures that the home page is accessible without authentication, whereas other endpoints require the user to be authenticated.

Handling Authentication Tokens

After successful authentication, applications receive an authentication token. Here’s a simple way to use the token to make authenticated requests:


@Autowired
private OAuth2AuthorizedClientService authorizedClientService;

public String getUserName(String clientRegistrationId, Authentication authentication) {
   OAuth2AuthorizedClient client = authorizedClientService.loadAuthorizedClient(
           clientRegistrationId, authentication.getName());

   String userInfoEndpointUri = client.getClientRegistration()
           .getProviderDetails().getUserInfoEndpoint().getUri();

   if (!StringUtils.isEmpty(userInfoEndpointUri)) {
       RestTemplate restTemplate = new RestTemplate();
       HttpHeaders headers = new HttpHeaders();
       headers.add(HttpHeaders.AUTHORIZATION, "Bearer " +client.getAccessToken().getTokenValue());

       HttpEntity<String> entity = new HttpEntity<>("", headers);
       ResponseEntity<Map> response = restTemplate.exchange(userInfoEndpointUri,HttpMethod.GET, entity, Map.class);
       Map userAttributes = response.getBody();
       return (String) userAttributes.get("name");
   }

   return null;
}

This method retrieves the user’s name using the OAuth 2.0 token to authenticate the request to the user info endpoint.

Conclusion

Integrating SSO in Java applications can significantly enhance user experience by simplifying the login process across multiple platforms. While the choice between SAML and OAuth 2.0 depends on specific application needs, OAuth 2.0 with OIDC is generally recommended for its adaptability. We've general the common vision on how SSO is implemented.

Following the outlined steps for a Java-based SSO implementation, developers can ensure a streamlined authentication process, reinforcing both user convenience and security.

Don’t hesitate to contact us to get started and receive a free consultation on how to implement SSO in your app!

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