[Full-Disclosure] Strange netcat behavior

["thalm" <thalm@netcabo.pt>]

Since netcat is a widely used network tool, this may have been discussed 
already, but since I wasn't able to found such discussion, here goes:
 
When using netcat (Windows and Linux versions) to connect to a web server, and 
everytime ENTER is pressed in the command line, netcat only sends LF (0x0A) 
instead of CRLF (0x0D 0x0A).
ex: GET / HTTP/1.0[LF][LF]
 
when using telnet, the behavior is different:
ex: GET / HTTP/1.0[CRLF][CRLF]
 
Although webservers (IIS and probably Apache) don't mind such behavior and 
accept it (LF) as if it was CRLF, RFC 2616 clearly states that the HTTP 
Request/Response Line and HTTP Headers *MUST* be separated by a CRLF and not 
only by a LF.
 
Why is there such a difference between netcat and telnet behavior?
 
NOTE: I'm wondering if sometimes a webserver exploit works when HTTP "lines" 
are separated by [CRLF] and does not work when HTTP "lines" are separated only 
by [LF].
This is actually the point I am refering to...
 
Tiago Halm
http://www.kodeit.org

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