Firewalls and RPC (was "Re: Improvement to IPFilter / nfsd in FBSD (6.2+?)")

[Chuck Swiger]

On Jan 11, 2007, at 1:50 PM, Garrett Cooper wrote:
>> Actually, no.  While rpcbind/portmap/portmapper is assigned to 111/ 
>> tcp &
>> udp, most other RPC services get assigned high port numbers in the  
>> 327xx
>> range, but that varies considerably from platform to platform.
>
> True. NFS is port 2049 by default, anyhow..

Good example, yet this is true on some platforms but not on others.

>> A firewall system should not be running any kind of filesharing;  
>> while
>> you can run PF, IPFW, etc on your fileserver, that ought to be a
>> secondary line of protection for "defense in depth", and your  
>> Internet
>> connection ought to have a dual-homed or multihomed firewall machine
>> which is dedicated to that role and which runs zero services.
>
> Right. However, I don't trust the rest of the clients on my subnet  
> other
> than the ones I maintain, so that's why I have setup the firewall  
> rules
> I have.

You really don't want to mix machines which are trusted with machines  
which are not trusted on the same subnet.  If you can't control which  
client machines get which IPs, you pretty much cannot use firewall  
rules to restrict filesharing only to the legit clients.

> Sorry for not more clearly defining the situation earlier, but here's
> the reasoning / rationale for what I'm doing..
>
> <IT nightmare>
>
> - -I live in a house with a shared LAN with a total of around 50 hosts
> connected / disconnected at various times of the day.
>
> - -I don't trust any of the Windows clients devoid a small handful  
> because
> I have had a variety of connectivity problems caused by improperly
> managed personal machines, virii, and spyware on machines here.
>
> - -There isn't a real means of properly controlling IP distribution  
> and
> people are free to change their IP addresses to whatever they choose
> (host information is set statically, not dynamically).
>
> - -I have 5 machines which have access to the network--2 serving  
> machines
> and 3 clients which aren't always attached to the network. I have set
> the IP addresses up so they all lie in a range, but I don't trust
> whether someone will IP squat my address and do whatever they want  
> to my
> serving machines (whether they mean to or it happens by accident).
>
> - -Some of the machines on the network have access to the machine  
> serving
> via Samba, but that's a limited number.

Perhaps you should consider setting up your own private subnet for  
your machines, and having a firewall guarding access to your machines  
which performs static NAT for the set of five IP addresses you've  
made claim to.

-- 
-Chuck