Why is My Spring Security CORS Filter Not Adding the \'Access-Control-Allow-Origin\' Header?

Spring Security CORS Filter: Troubleshooting 401 Error

Despite implementing Spring Security in your existing project, you continue to encounter a 401 "No 'Access-Control-Allow-Origin' header" error from your server. This arises because no such header is attached to the response.

To resolve this, you attempted to add a custom filter to the filter chain before the logout filter. However, it appears that the filter is not applying to your requests. Let's examine your existing configuration and potential issues:

Security Configuration:

The security configuration is utilizing CORS configuration, which is configured correctly. However, it's important to note that the @CrossOrigin annotation in your controller may conflict with this configuration, leading to unpredictable behavior.

Filter Implementation:

Your filter seems to be configured properly as a OncePerRequestFilter. It defines the necessary methods for filter operation, including adding CORS headers to the response.

Filter Registration:

Your filter is being registered via Spring Boot, which is confirmed by the log entry. The filter is mapped to "/*" and its position in the filter chain is appropriate.

Generated Filter Chain:

The generated filter chain output indicates that your CORS filter is missing from the list. This may explain why it's not taking effect.

Response Headers:

You have not provided the full response headers received from the server. Examining these headers would offer insights into the actual CORS headers present in the response.

Edit 1:

The solution suggested by @Piotr Sołtysiak was attempted, but it also failed to resolve the issue. The CORS filter was absent from the generated filter chain, and the 401 error persisted.

Resolution:

In Spring Security 4.1 and later, implementing CORS support has changed. The preferred approach is to use the following configurations:

• Create a WebConfig class that extends WebMvcConfigurerAdapter and implements the addCorsMappings method to define allowed origins, methods, and headers:

<code class="java">@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedMethods("HEAD", "GET", "PUT", "POST", "DELETE", "PATCH");
    }
}</code>

• In your SecurityConfig class, enable CORS and define a custom CorsConfigurationSource:

<code class="java">@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.cors();
    }

    @Bean
    public CorsConfigurationSource corsConfigurationSource() {
        // ... (Define the CORS configuration and return a UrlBasedCorsConfigurationSource)
    }
}</code>

Avoid using the following incorrect approaches:

• http.authorizeRequests().antMatchers(HttpMethod.OPTIONS, "/**").permitAll();
• web.ignoring().antMatchers(HttpMethod.OPTIONS);

These methods are deprecated and provide an incomplete CORS implementation.

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