Date: Wed, 29 Mar 2000 09:58:45 -0800 From: Alan Batie <batie@rdrop.com> To: Pierre Chiu <pccb@yahoo.com> Cc: freebsd-security@FreeBSD.ORG Subject: Re: FTP with firewall rules Message-ID: <20000329095845.54716@rdrop.com> In-Reply-To: <4520.000329@yahoo.com>; from Pierre Chiu on Wed, Mar 29, 2000 at 12:30:08PM -0500 References: <4520.000329@yahoo.com>
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On Wed, Mar 29, 2000 at 12:30:08PM -0500, Pierre Chiu wrote:
> In FreeBSD 4.0, ipfw supports stateful inspection.
>
> I think this is very useful for running ftp server and would works for both
> active and passive setup.
As I read the man page, that doesn't mean what it sounds like you think
it means. To do active mode ftp properly, ipfw would need to parse the
contents of the packets on the ftp control channel and dynamically allow
the corresponding incoming connection. There's no indication that this
parsing capability is present.
On the other hand, it's not clear just what keep-state/check-state do
either; what is the difference between the example:
ipfw add check-state
ipfw add deny tcp from any to any established
ipfw add allow tcp from my-net to any setup keep-state
and
ipfw add allow tcp from any to my-net established
ipfw add allow tcp from my-net to any
Both only allow outgoing connections. I suppose in the latter case,
it would be possible to send in packets that pretend to be "established"
but I'm not sure what that would get a hacker...
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