2:45 a.m.
My trusty old heavily customized firewall-2.4-stronger script doesn't
like systemd, so I think firewalld is probably the way to go, but it
doesn't seem to support some of the things I need to do without
resorting to direct rules, which seems to be undermining the whole
"dynamic" idea. Maybe I missed something and there are better ways to
do this. This is for a small office that I can't really replicate the
setup of, so I can't test it properly without them being offline for a
while. Maybe someone could tell me if I'm on the right track before I
do that.
There are three relevant ethernet interfaces:
0) cable modem in bridge mode (p35p1) - "external" zone
1) office lan (p2p1) - "work" zone - 192.168.10.0/24 segment
2) dmz for testing client machines (p3p1) - "dmz" zone 192.168.20.0/24
question 1
Internet traffic is being routed successfully from both internal
networks out to the world and back. I used to have rules dropping
packets between the two localnets, just to keep the customer machines
from spreading viruses to the office. Even without those rules, the few
tests I was able to try without their network to test on didn't connect.
Did I miss something? Do I have to do something more to /enable/
routing between the two localnets? Or is this a
fluke/misconfiguration/bad test I need to be concerned about?
question 2
How exactly are zones applied? When a packet wants to be routed from
the "work" localnet to the masquerading "external", which zone
applies?
Both of them? What if the packet is coming from an interface with one
zone, from an address with another zone, routed to an interface with a
third zone? How do zone rules translate to incoming, outgoing, and
forwarding traffic?
question 3
What are the recommended methods of blocking specific localnet addresses
or the whole "work" zone from connecting to specific ports on external
host ranges, i.e. no FaceBook at work? Would rich rules in the "work"
zone be the proper way? It's kinda messy not being able to note the
purpose of blocking a specific address when you have 20 or so different
address ranges blocked and keep adding more.
question 4
Is there a way to specify classes of destinations, like a destination
zone? It would be nice to bundle up the ip ranges or even domains of
FaceBook and Twitter and Tumblr and whatnot into a "SocialMedia" class
and just block any traffic to those destinations, either from the "work"
zone or from specific localnet IPs. Lists of IPs with no notes are
pretty unwieldy and not very reliable. Although, the xml file does
allow notes, so that's what I'm doing so far. It works, I think, but
it's ugly.
question 5
If I want to allow the dmz to only call out to the internet on specific
services, like http/https, but no smtp or ftp, is it sufficient to just
enable the services I want in the dmz zone? Does that affect
connections that would just be masqueraded and forwarded out the
external zone? What if I want to temporarily enable ftp from the dmz to
one specific address, like a server on the work localnet? Would a rich
rule for FTP service with an accept action do it? Would it have to be
passive FTP only?
That's a bit more question than I thought I had when I started writing
this, but hopefully someone's still reading. Thanks in advance for any
guidance you can offer.
--
-Dave Noelle, dave(a)Straylight.org