Secure Spring REST API Using OAuth2

Let’s secure our Spring REST API with OAuth2 + PostgreSQL. We will store user credentials in the PostgreSQL database and client credentials will be stored in the In-memory database. Every client has its own unique client ID.

To secure our REST API, we will have to do the following things:

• Configure Spring Security and the database

• Configure the authorization server and resource server

• Get an access token and a refresh token

• Get a protected Resource (REST API) using an access token

Before we start, let's look at some basic concepts related to Spring Security OAuth2.

OAuth2 Roles

Resource Owner

A resource owner is a person (like an end user) in an application that owns the service or a security policy.

Resource Server

This is the resource server hosting the protected resource or service.

Client Application

The client application is the application requesting access to resources stored on the resource server. The client application also obtains authorization from the resource owner.

Authorization Server

The authorization server is the server authorizing the client app to access the resources of the resource owner.

Application

Let's start to secure our REST API endpoints.

First, we need to enable Spring Security to add the security feature in the application. To configure and enable Spring Security, the @EnableWebSecurity annotation is used.

By using @EnableGlobalMethodSecurity, we can easily secure our methods with Java configurations. Global method security will activate  @PreFilter, @PostFilter , @PreAuthorize, and the @PostAuthorize  annotations if we want to use them.

@EnableWebSecurity
@EnableGlobalMethodSecurity(securedEnabled = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter {

  @Autowired
  UserDetailsServiceImpl userDetailsService;


  @Override
  protected void configure(HttpSecurity http) throws Exception {
    http.csrf().disable().sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS) 
      .and().authorizeRequests().antMatchers("/oauth/token")
      .permitAll().anyRequest().authenticated();
  }

  @Bean
  public DaoAuthenticationProvider authenticationProvider() {
    DaoAuthenticationProvider provider = new DaoAuthenticationProvider();
    provider.setPasswordEncoder( bCryptPasswordEncoder() );
    provider.setUserDetailsService(userDetailsService);
    return provider;
  }

  @Bean
  public BCryptPasswordEncoder bCryptPasswordEncoder() {
    return new BCryptPasswordEncoder();
  }

  @Override
  @Bean
  public AuthenticationManager authenticationManagerBean() throws Exception {
    return super.authenticationManagerBean();
  }

  @Autowired
  public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
    auth.authenticationProvider(authenticationProvider());
  }
}

Note:

• Here, WebSecurityConfigurerAdapter  is used to customize security implementation.

•  Endpoint /OAuth/tpken is used to request a token (access or refresh).

• We inject a custom implementation of UserDetailsService in order to retrieve user details from the database.

• We use the defined BCryptPasswordEncoder bean for password encoding.

Now, we need to configure the authorization server. The @EnableAuhtorizationServer  annotation enables an authorization server. AuthorizationServerConfigurerAdapter  implements the  AuthorizationServerConfigurer, which provides all the necessary methods to configure an Authorization server. It also contains information about registered clients and possible access scopes and grant types.

@Configuration
@EnableAuthorizationServer
public class OAuthConfiguration extends AuthorizationServerConfigurerAdapter {

  @Autowired
  @Qualifier("authenticationManagerBean")
  private AuthenticationManager authenticationManager;

  @Autowired
  UserDetailsService userDetailsService;

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

  @Override
  public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
    clients.inMemory()
      .withClient("fooClientId").secret("secret")
      .authorizedGrantTypes("password", "authorization_code", "refresh_token").scopes("read","write")
      .autoApprove(true);
  }

  @Override
  public void configure(final AuthorizationServerEndpointsConfigurer endpoints) throws Exception {
    endpoints.tokenStore(tokenStore()).authenticationManager(authenticationManager).accessTokenConverter(defaultAccessTokenConverter())
      .userDetailsService(userDetailsService);
  }

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

  @Bean
  public JwtAccessTokenConverter defaultAccessTokenConverter() {
    JwtAccessTokenConverter converter = new JwtAccessTokenConverter();
    converter.setSigningKey("123");
    return converter;
  }
}

Notes on the above configuration:

• Registers a client with client-id ‘fooClientId’ and password ‘ secret’ and the roles and scope they are allowed.

• Specifies authorized grant types (password, authorization_code, refresh_token).

• Specifies the JwtTokenStore to store tokens.

Next, we need to configure the resource server. The @EnableResourceServer  annotation, applied on OAuth2 Resource Servers, enables a Spring Security filter that authenticates requests using an incoming OAuth2 token. The class ResourceServerConfigurerAdapter implements the ResourceServerConfigure,  providing methods to adjust the access rules and paths that are protected by OAuth2 security.

@Configuration
@EnableResourceServer
public class ResourceServerConfiguration extends ResourceServerConfigurerAdapter {
    private static final String RESOURCE_ID = "resource-server-rest-api";
    @Override
    public void configure(ResourceServerSecurityConfigurer resources) {
        resources.resourceId(RESOURCE_ID);
    }
    @Override
    public void configure(HttpSecurity http) throws Exception {
        http.antMatcher("/**").authorizeRequests().anyRequest().authenticated();
    }
}

Next, we need to update the application.properties to configure the PostgreSQL database. Create the user_management database in PostgreSQL and add the user table to store user credentials with roles.

spring.jpa.database-platform=org.hibernate.dialect.PostgreSQL9Dialect
# Hibernate ddl auto (create, create-drop, validate, update)
spring.jpa.hibernate.ddl-auto=update
spring.datasource.url=jdbc:postgresql://localhost/user_management
spring.datasource.username=postgres
spring.datasource.password=root
spring.jpa.generate-ddl=true

Database script  :

// To create database "user_management"
CREATE DATABASE user_management;

// To create table "users" in "user_management" database
CREATE TABLE users(
   id INT PRIMARY KEY     NOT NULL,
   enabled INT NOT NULL,
   password TEXT    NOT NULL,
   username  TEXT    NOT NULL,
   role TEXT    NOT NULL
);

// To insert values into table
INSERT INTO users VALUES (1,1,'$2a$10$iFolDdAquu/qSclfNDiBK.GFpO0gUBAsCilygHuCy6pUWVd.4ZK8G', 'admin','ADMIN');

Test Application

To access any secured REST API endpoint, first, we will have to get the access token. To get the access token, we will need to add an authorization header with client credentials and add the request body with user credentials in postman.

After receiving the access token and refresh token, we can access any secured REST API endpoints using access token. When the access token expired, the refresh token is used to get a new access token.

You can refer to the whole project on GitHub.