Скачать или смотреть Resolving HttpServletResponse.sendError Empty Body in Spring with CSRF Protection

This guide discusses how to handle the issue of empty response bodies when using `sendError` in Spring applications with CSRF protection enabled. Learn how to configure Spring Security to ensure informative error messages are returned.
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Understanding the Issue: Empty Response Body with CSRF Tokens in Spring

When developing applications using Spring and the Spring Security framework, it’s essential to ensure that user interactions with the application are secure. One of the common security measures is Cross-Site Request Forgery (CSRF) protection, which helps prevent unauthorized commands from being transmitted from a user that the web application trusts. However, developers may encounter a perplexing issue: when a POST request is made without a valid CSRF token, they receive an HTTP 403 response status, but the response body remains empty.

This problem often arises when using Spring's error handling mechanism with a custom AccessDeniedHandler. In this post, we will explore why this issue occurs and provide a solution to ensure that informative error messages are included in the response.

The Setup

To illustrate the issue, consider the following code snippets that configure a simple Spring Boot application:

Controller

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Security Configuration

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Custom Access Denied Handler

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When making a POST request to the /hello/ endpoint without including a CSRF token, users will receive a 403 Forbidden response. However, the problem occurs when the body of the response is empty, leading to confusion regarding the cause of the request denial.

Root Cause Analysis

The root of this issue lies within the Spring Security configuration. Specifically, when the configuration requires authentication for any request using the method .anyRequest().authenticated(), it inadvertently blocks access to the default error page (/error), which is where Spring would redirect for handling error responses.

This access denial results in the response that you see—an empty body when calling response.sendError(). Since the custom error handler has no way to redirect or return an appropriate error response (as it can't access the /error path), it leads to confusion for the developer facing this issue.

Solution: Granting Access to the Error Page

To resolve this issue, you need to explicitly allow access to the /error endpoint. This can be done by modifying the security configuration to include a directive that permits access to this path. Here’s how you can adjust your SecurityConfig class:

Updated Security Configuration

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By adding .antMatchers("/error").permitAll(), you ensure that the Spring application can properly handle error responses and provide meaningful feedback in the response body instead of leaving it empty.

Summary

In conclusion, the issue of obtaining an empty response body when using HttpServletResponse.sendError results from certain Spring Security configurations that block access to the error handling paths. By allowing unauthenticated access to the /error page, you enable the application to generate thoughtful error messages, thereby improving the overall user and developer experience.

Key Takeaway

When configuring Spring Security, always consider how it affects predefined system paths, like error handling routes, especially when implementing a custom error handler. With the proper configurations, your application will effectively communicate errors, ensuring both security and usability.