How do you handle CSRF protection in Spring Boot?

Table of Contents

• Introduction
• CSRF Protection in Spring Boot
  • 1. How CSRF Protection Works in Spring Security
  • Default Behavior of CSRF in Spring Security
  • Example of CSRF Token in HTML Form:
  • 2. Disabling CSRF Protection in Spring Boot
    • Disabling CSRF Protection Globally
    • Disabling CSRF Protection for Specific Endpoints
  • 3. Enabling CSRF Protection for Stateless Applications
  • 4. Customizing CSRF Token Repository
• Conclusion

Introduction

Cross-Site Request Forgery (CSRF) is a type of attack where a malicious user can trick a logged-in user into performing unintended actions on a web application. CSRF protection ensures that any state-changing requests (like POST, PUT, DELETE) are legitimate and come from trusted sources. Spring Security provides a robust mechanism to handle CSRF attacks, and it’s crucial to understand how to configure it properly in your Spring Boot applications.

By default, Spring Security enables CSRF protection, but there are cases where you may want to disable it or customize its behavior based on the needs of your application (e.g., for stateless applications using JWT).

CSRF Protection in Spring Boot

1. How CSRF Protection Works in Spring Security

Spring Security’s CSRF protection works by requiring that every state-changing request (such as POST, PUT, DELETE) includes a CSRF token that verifies the authenticity of the request. This token is typically included in the HTML form or sent via an HTTP header (for AJAX requests). The server verifies that the request is coming from the user’s own session and not from a malicious source.

Default Behavior of CSRF in Spring Security

By default, Spring Security enables CSRF protection for state-changing requests, and it expects a CSRF token to be included in the request. The CSRF token can be injected into HTML forms or added to AJAX requests.

Spring automatically generates this token and stores it in the user's session. If a state-changing request is received without the correct token, Spring Security will block the request.

Example of CSRF Token in HTML Form:

When using Spring Security with form-based authentication, Spring automatically generates a CSRF token and inserts it into HTML forms like this:

In this case, the **_csrf** parameter holds the token value, which is validated by Spring Security when the form is submitted.

2. Disabling CSRF Protection in Spring Boot

While CSRF protection is essential for most web applications, it is sometimes not required for certain types of applications, particularly stateless REST APIs or applications that rely on tokens (like JWTs). In such cases, you may need to disable CSRF protection to avoid unnecessary overhead or conflicts.

Disabling CSRF Protection Globally

To disable CSRF protection globally, you can configure it in your **SecurityConfig** class:

In the example above, **http.csrf().disable()** disables CSRF protection for the entire application.

Disabling CSRF Protection for Specific Endpoints

If you only want to disable CSRF protection for certain endpoints (e.g., a REST API), you can selectively disable CSRF protection for specific URL patterns.

In this configuration, CSRF protection is disabled for **/api/**** endpoints, while other parts of the application continue to use CSRF protection.

3. Enabling CSRF Protection for Stateless Applications

For stateless applications, such as those using JWT (JSON Web Tokens) for authentication, CSRF protection is typically unnecessary. Since these applications do not rely on cookies to maintain sessions, attackers cannot exploit CSRF vulnerabilities.

However, if you are using JWT for authentication, you should configure Spring Security to properly handle authentication headers and disable CSRF protection.

Example of stateless configuration with JWT (CSRF disabled):

In this example:

• CSRF protection is disabled since the application uses JWT-based authentication.
• Stateless authentication is achieved by adding a custom JWT filter (e.g., **JwtAuthenticationFilter**).

4. Customizing CSRF Token Repository

If you need more control over how Spring Security handles CSRF tokens, you can customize the CSRF token repository. By default, Spring Security uses an in-memory repository to store CSRF tokens. You can replace it with a cookie-based or database-backed repository if necessary.

Here’s an example of using a custom CSRF token repository:

In this example, we are using a cookie-based CSRF token repository (CookieCsrfTokenRepository.withHttpOnlyFalse()), which stores the CSRF token in an HTTP-only cookie.

Conclusion

CSRF protection is an essential security feature for most web applications, as it protects against malicious requests designed to exploit an authenticated user’s session. In Spring Boot applications, Spring Security enables CSRF protection by default, but it can be easily customized or disabled based on the application’s requirements.

• For stateless applications (e.g., those using JWT), CSRF protection is typically not needed, and it can be safely disabled.
• For traditional web applications with sessions and cookies, CSRF protection is crucial and should be enabled, with tokens provided in forms or AJAX requests.
• Customizing CSRF settings (such as using a cookie-based CSRF repository) can provide more flexibility depending on your application’s needs.

Always evaluate your application's security requirements to determine whether to enable, disable, or customize CSRF protection in Spring Boot.