Websocket Authentication and Authorization in Spring

As stated above the documentation looks unclear (IMHO), until Spring provide some clear documentation, here is a boilerplate to save you from spending two days trying to understand what the security chain is doing.

A really nice attempt was made by Rob-Leggett but, he was forking some Springs class and I don’t feel comfortable doing so.

Things to know before you start:

• Security chain and Security config for http and WebSocket are completely independent.
• Spring AuthenticationProvider take not part at all in Websocket authentication.
• The authentication won’t happen on HTTP negotiation endpoint in our case, because none of the JavaScripts STOMP (websocket) libraries I know sends the necessary authentication headers along with the HTTP request.
• Once set on CONNECT request, the user (simpUser) will be stored in the websocket session and no more authentication will be required on further messages.

Maven deps

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-websocket</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-messaging</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-messaging</artifactId>
</dependency>

WebSocket configuration

The below config register a simple message broker (a simple endpoint that we will later protect).

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends WebSocketMessageBrokerConfigurer {
    @Override
    public void configureMessageBroker(final MessageBrokerRegistry config) {
        // These are endpoints the client can subscribes to.
        config.enableSimpleBroker("/queue/topic");
        // Message received with one of those below destinationPrefixes will be automatically router to controllers @MessageMapping
        config.setApplicationDestinationPrefixes("/app");
    }

    @Override
    public void registerStompEndpoints(final StompEndpointRegistry registry) {
        // Handshake endpoint
        registry.addEndpoint("stomp"); // If you want to you can chain setAllowedOrigins("*")
    }
}

Spring security config

Since the Stomp protocol rely on a first HTTP Request, we’ll need to authorize HTTP call to our stomp handshake endpoint.

@Configuration
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(final HttpSecurity http) throws Exception {
        // This is not for websocket authorization, and this should most likely not be altered.
        http
                .httpBasic().disable()
                .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS).and()
                .authorizeRequests().antMatchers("/stomp").permitAll()
                .anyRequest().denyAll();
    }
}

Then we’ll create a service responsible for authenticating users.

@Component
public class WebSocketAuthenticatorService {
    // This method MUST return a UsernamePasswordAuthenticationToken instance, the spring security chain is testing it with 'instanceof' later on. So don't use a subclass of it or any other class
    public UsernamePasswordAuthenticationToken getAuthenticatedOrFail(final String  username, final String password) throws AuthenticationException {
        if (username == null || username.trim().isEmpty()) {
            throw new AuthenticationCredentialsNotFoundException("Username was null or empty.");
        }
        if (password == null || password.trim().isEmpty()) {
            throw new AuthenticationCredentialsNotFoundException("Password was null or empty.");
        }
        // Add your own logic for retrieving user in fetchUserFromDb()
        if (fetchUserFromDb(username, password) == null) {
            throw new BadCredentialsException("Bad credentials for user " + username);
        }

        // null credentials, we do not pass the password along
        return new UsernamePasswordAuthenticationToken(
                username,
                null,
                Collections.singleton((GrantedAuthority) () -> "USER") // MUST provide at least one role
        );
    }
}

Note that: UsernamePasswordAuthenticationToken MUST have at least one GrantedAuthority, if you use another constructor, Spring will auto-set isAuthenticated = false.

Almost there, now we need to create an Interceptor that will set the `simpUser` header or throw `AuthenticationException` on CONNECT messages.

@Component
public class AuthChannelInterceptorAdapter extends ChannelInterceptor {
    private static final String USERNAME_HEADER = "login";
    private static final String PASSWORD_HEADER = "passcode";
    private final WebSocketAuthenticatorService webSocketAuthenticatorService;

    @Inject
    public AuthChannelInterceptorAdapter(final WebSocketAuthenticatorService webSocketAuthenticatorService) {
        this.webSocketAuthenticatorService = webSocketAuthenticatorService;
    }

    @Override
    public Message<?> preSend(final Message<?> message, final MessageChannel channel) throws AuthenticationException {
        final StompHeaderAccessor accessor = MessageHeaderAccessor.getAccessor(message, StompHeaderAccessor.class);

        if (StompCommand.CONNECT == accessor.getCommand()) {
            final String username = accessor.getFirstNativeHeader(USERNAME_HEADER);
            final String password = accessor.getFirstNativeHeader(PASSWORD_HEADER);

            final UsernamePasswordAuthenticationToken user = webSocketAuthenticatorService.getAuthenticatedOrFail(username, password);

            accessor.setUser(user);
        }
        return message;
    }
}

Note that: preSend() MUST return a UsernamePasswordAuthenticationToken, another element in the spring security chain test this.
Note that: If your UsernamePasswordAuthenticationToken was built without passing GrantedAuthority, the authentication will fail, because the constructor without granted authorities auto set authenticated = false THIS IS AN IMPORTANT DETAIL which is not documented in spring-security.

Finally create two more class to handle respectively Authorization and Authentication.

@Configuration
@Order(Ordered.HIGHEST_PRECEDENCE + 99)
public class WebSocketAuthenticationSecurityConfig extends  WebSocketMessageBrokerConfigurer {
    @Inject
    private AuthChannelInterceptorAdapter authChannelInterceptorAdapter;
    
    @Override
    public void registerStompEndpoints(final StompEndpointRegistry registry) {
        // Endpoints are already registered on WebSocketConfig, no need to add more.
    }

    @Override
    public void configureClientInboundChannel(final ChannelRegistration registration) {
        registration.setInterceptors(authChannelInterceptorAdapter);
    }

}

Note that: The @Order is CRUCIAL don’t forget it, it allows our interceptor to be registered first in the security chain.

@Configuration
public class WebSocketAuthorizationSecurityConfig extends AbstractSecurityWebSocketMessageBrokerConfigurer {
    @Override
    protected void configureInbound(final MessageSecurityMetadataSourceRegistry messages) {
        // You can customize your authorization mapping here.
        messages.anyMessage().authenticated();
    }

    // TODO: For test purpose (and simplicity) i disabled CSRF, but you should re-enable this and provide a CRSF endpoint.
    @Override
    protected boolean sameOriginDisabled() {
        return true;
    }
}