Cross-Site Request Forgery (CSRF)

Introduction

Cross-Site Request Forgery (CSRF) is a web security vulnerability that allows attackers to trick authenticated users into executing unwanted actions on a web application. CSRF attacks commonly target AJAX applications by taking advantage of the trust placed in a user's browser and their authenticated session. By crafting malicious requests and tricking users into executing them, attackers can perform actions on behalf of the user without their consent. In this tutorial, you will learn about CSRF attacks in AJAX applications and how to prevent them to ensure the security of your web application.

Example Code

Here's an example of a CSRF vulnerability in an AJAX application:


        function changePassword() {
          var xhr = new XMLHttpRequest();
          xhr.open("POST", "https://example.com/change-password", true);
          xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
          xhr.send("newPassword=attackerpassword");
        }

In this example, the changePassword() function sends a POST request to the server to change the user's password. However, there are no security measures in place to prevent CSRF attacks. An attacker could craft a malicious web page that automatically executes this function when visited by a user who is already authenticated on the target application. As a result, the user's password would be changed without their knowledge or consent.

Steps to Prevent CSRF

Use anti-CSRF tokens: Generate unique tokens for each session and include them in requests. Validate the tokens on the server-side to ensure requests originate from trusted sources.
Implement SameSite cookies: Set the SameSite attribute of cookies to "Strict" or "Lax" to prevent cross-site requests.
Use the Referer header: Check the Referer header on the server-side to verify that requests originate from trusted sources.
Implement reauthentication: Prompt users to reauthenticate for sensitive actions, such as changing passwords or making financial transactions.

Common Mistakes

Not implementing anti-CSRF tokens or failing to validate them on the server-side.
Not properly configuring SameSite attributes for cookies, leaving them vulnerable to CSRF attacks.
Not checking the Referer header to ensure requests originate from trusted sources.

Frequently Asked Questions

Q: Can CSRF attacks be executed from different domains?

A: CSRF attacks can be executed from different domains if the target application does not implement proper security measures. Attackers can use techniques like Cross-Origin Resource Sharing (CORS) or open redirect vulnerabilities to launch CSRF attacks from different domains.
Q: How can I implement anti-CSRF tokens in AJAX applications?

A: To implement anti-CSRF tokens in AJAX applications, you need to generate a unique token for each session and include it in requests. The token should be validated on the server-side to ensure requests originate from trusted sources. You can store the token in a server-side session variable or include it as a hidden input field in HTML forms.

Summary

Cross-Site Request Forgery (CSRF) attacks pose a significant threat to the security of AJAX applications. By tricking authenticated users into performing unwanted actions, attackers can compromise the integrity and privacy of user data. This tutorial provided an overview of CSRF attacks in AJAX applications and outlined steps to prevent them. By implementing anti-CSRF tokens, using SameSite cookies, checking the Referer header, and considering reauthentication for sensitive actions, you can protect your application from CSRF vulnerabilities. By prioritizing security measures, you can ensure the safety of your users' data and maintain the trustworthiness of your web application.

Cross-Site Request Forgery (CSRF) - AJAX Tutorial