Firewalls in FreeBSD?

[Jeremy Chadwick]

On Fri, Oct 31, 2008 at 12:05:28PM -0400, Lowell Gilbert wrote:
> Jeremy Chadwick <koitsu at FreeBSD.org> writes:
> 
> > On Thu, Oct 30, 2008 at 06:34:31PM -0500, Jack Barnett wrote:
> >>
> >> Ok, I had some progress with this last night. Basically what I do is:
> >>
> >> in natd - redirect_port 1000 to 10000 to the internal windows box.
> >> set ipfw to "open" file wall.
> >>
> >> Obviously this isn't prefect - but gives some idea of what's going on.
> >>
> >> What I'd like to do, is a) keep the nat redirects since that works  
> >> pretty well.
> >> b) in ipfw, ONLY allow data back on these ports IF the windows box has  
> >> established the connection out first then deny everything else.
> >
> > This is called "port triggering" in the residential router world.  I
> > don't know how to do this on FreeBSD.
> 
> Stateful rules are the only way to do it.
> In fact, this is the main purpose of stateful rules.

Read this part of the thread, where I outline protocol flow (based on
what the OP has stated about the protocol, which so far appears to be
accurate):

http://lists.freebsd.org/pipermail/freebsd-questions/2008-October/thread.html

Stateful rules will not solve this problem.

The OP wants a feature that tells ipfw or pf "after the TCP handshake
has completed, dynamically add a port forward for port X on interface Y
to machine A on port Z; when the TCP session is FIN'd cleanly, or
extinguishes, dynamically remove that port forward".

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |