Spring Security CORS Filter: Troubleshooting Common Issues

When integrating Spring Security into an existing project, you may encounter CORS-related errors if headers like 'Access-Control-Allow-Origin' are not set in the response. To resolve this, you can implement a custom filter, such as the MyFilter in your code snippet. However, you also mentioned that this filter was not being applied to your requests.

Since Spring Security 4.1, there is a more straightforward approach to enable CORS support:

Proper CORS Configuration:

<pre>
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

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

}
</pre>

Spring Security Configuration:

<pre>
@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

@Override
protected void configure(HttpSecurity http) throws Exception {
    http.cors();
}

@Bean
public CorsConfigurationSource corsConfigurationSource() {
    // Configure CORS settings here
}

}
</pre>

Avoid These Incorrect Solutions:

Do not use the following incorrect approaches, such as:

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

Additional Troubleshooting Tips:

• Ensure that your custom filter, MyFilter, is properly registered in the Spring context.
• Verify that the CORS settings in your SecurityConfiguration class are correct.
• Check the generated filter chain to ensure that MyFilter is included and sequenced accordingly.
• Use tools like HTTPie or browser extensions to inspect the request and response headers to identify any discrepancies.

By following the recommended configuration and avoiding incorrect solutions, you should be able to resolve the CORS errors and enable proper CORS support in your application.