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Date:      Mon, 24 Dec 2001 20:23:45 -0600
From:      David Kelly <dkelly@hiwaay.net>
To:        Martin Schweizer <info@pc-service.ch>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: ipfw & ftp 
Message-ID:  <200112250223.fBP2NjU37711@grumpy.dyndns.org>
In-Reply-To: Message from Martin Schweizer <pcservi@spectraweb.ch>  of "Mon, 24 Dec 2001 09:51:43 %2B0100." <20011224095143.B318@spectraweb.ch> 

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Martin Schweizer writes:
> Hello Darryl
> =

> I attached you my rc.firewall. I found a solution with passive and acti=
ve ftp

The flip side of "passive ftp" is "non-passive ftp". Is not really ftp =

that is being passive but its "ftp for passive firewalls who don't know =

the ftp protocol."

[...]
> ipfw add allow tcp from any 20 to me 1024-49151 keep-state # aktives FT=
P
> ipfw add allow tcp from any 20 to 192.168.1.1/24 1024-49151 keep-state

So all I have to do to probe you with impunity is to source my probes =

from port 20. Looking at my ipfw logs your rule would let about 1 in 50 =

probes past. But then again you are running ftpd and intend outside =

connections to come in but the above firewall rule opens everything =

else.

For outgoing connections I have found the punch_fw option of natd works =

perfectly for non-passive ftp but doesn't detect passive outgoing =

connections.

-- =

David Kelly N4HHE, dkelly@hiwaay.net
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.



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