CSRF Identification

1. Identification of CSRF Vulnerabilities

Identification Process:

  • A penetration tester looks for sensitive actions (like changing a password, modifying user details, etc.) that can be performed without any unique token or with predictable tokens.
  • The tester crafts a malicious request (usually in the form of a URL or HTML page) that, if visited or submitted by a victim, will cause the application to perform an action on behalf of the victim without their consent.

Example:

  • Suppose there's a function in the application that allows a user to change their email address with a simple POST request, and this function doesn't require a CSRF token.

  • The pentester crafts an HTML page with a form that auto-submits upon loading and targets the email change function:

    htmlCopy code
<html>
  <body>
    <form action="<http://example.com/changeEmail>" method="POST" id="csrf-form">
      <input type="hidden" name="newEmail" value="attacker@example.com" />
    </form>
    <script>document.getElementById('csrf-form').submit();</script>
  </body>
</html>

  • If a logged-in user is tricked into loading this page, and their email address changes without further interaction, the application is vulnerable to CSRF.

2. Tools and Techniques

  • Automated Scanning: Tools like OWASP ZAP and Burp Suite can be configured to test for CSRF vulnerabilities by identifying forms or requests that lack anti-CSRF tokens.
  • Manual Testing: Manual testing involves reviewing the application's source code or observed behavior to identify state-changing operations that do not require a unique token or use predictable tokens.

3. Mitigation Strategies

  • CSRF Tokens: Ensure that every state-changing request from the client includes a unique, unpredictable token validated by the server.
  • SameSite Cookies: Use the SameSite attribute in cookies to restrict them to first-party contexts, reducing the risk of CSRF.
  • Double Submit Cookie: Although not as strong as CSRF tokens, this technique involves matching a value in the cookie with a value sent in a hidden form field to ensure the request originated from the user's browser.

4. Best Practices for Penetration Testers

  • Document and Report: Clearly document and report the CSRF vulnerabilities, including the potential impact and steps to reproduce the issue.
  • Ethical Considerations: Ensure that all testing is authorized and conducted without causing unnecessary harm or disruption to the application's normal operations.

By systematically identifying CSRF vulnerabilities and recommending robust defenses, penetration testers play a crucial role in enhancing the security of web applications.