RE: an anternative to port-knoking using the OpenBSD pf only

["Shenk, Jerry A" <jshenk () decommunications com>]

Another problem (challenge;) would be gaining access from behind a
NATting device.  Sometimes, they'll modify the headers and make the
packets look like they originated on the NATting device.  Some fields
would probably work better than others.

-----Original Message-----
From: Joachim Schipper [mailto:j.schipper () math uu nl] 
Sent: Tuesday, January 24, 2006 4:57 AM
To: pen-test () securityfocus com
Subject: Re: an anternative to port-knoking using the OpenBSD pf only

On Mon, Jan 23, 2006 at 10:44:52PM +0100, poplix wrote:
> Hi there,
>
> I wish to propose an alternative to port knoking that uses the native
> OpenBSD's pf code only. The idea is to  use the pf's passive os
> fingerprinter to authenticate initial SYN packets.
> With a tool (or kernel patch) able to rewrite packets header is
possible
> to use a specific sequence of header fields as a key to validate  
> packets.

This is an interesting - albeit not exactly new - idea, but it has the
very real disadvantage over port knocking that it requires priviliges
(typically root) on the connecting host.

                Joachim

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