Annotation of src/share/ipf/firewall.2, Revision 1.2
1.1 dm 1: #
2: # This is an example of a fairly heavy firewall used to keep everyone
3: # out of a particular network while still allowing people within that
4: # network to get outside.
5: #
6: # The example assumes it is running on a gateway with interface ppp0
7: # attached to the outside world, and interface ed0 attached to
8: # network 192.168.4.0 which needs to be protected.
9: #
10: #
11: # Pass any packets not explicitly mentioned by subsequent rules
12: #
13: pass out from any to any
14: pass in from any to any
15: #
16: # Block any inherently bad packets coming in from the outside world.
17: # These include ICMP redirect packets, IP fragments so short the
18: # filtering rules won't be able to examine the whole UDP/TCP header,
19: # and anything with IP options.
20: #
21: block in log quick on ppp0 proto icmp from any to any icmp-type redir
22: block in log quick on ppp0 proto tcp/udp all with short
23: block in log quick on ppp0 from any to any with ipopts
24: #
25: # Block any IP spoofing atempts. (Packets "from" our network
26: # shouldn't be coming in from outside).
27: #
28: block in log quick on ppp0 from 198.168.4.0/24 to any
29: block in log quick on ppp0 from localhost to any
30: #
31: # Block all incoming UDP traffic except talk and DNS traffic. NFS
32: # and portmap are special-cased and logged.
33: #
34: block in on ppp0 proto udp from any to any
35: block in log on ppp0 proto udp from any to any port = sunrpc
36: block in log on ppp0 proto udp from any to any port = 2049
37: pass in on ppp0 proto udp from any to any port = domain
38: pass in on ppp0 proto udp from any to any port = talk
39: pass in on ppp0 proto udp from any to any port = ntalk
40: #
41: # Block all incoming TCP traffic connections to known services,
42: # returning a connection reset so things like ident don't take
43: # forever timing out. Don't log ident (auth port) as it's so common.
44: #
45: block return-rst in log on ppp0 proto tcp from any to any flags S/SA
1.2 ! dm 46: block return-rst in on ppp0 proto tcp from any to any port = auth flags S/SA
1.1 dm 47: #
48: # Allow incoming TCP connections to ports between 1024 and 5000, as
49: # these don't have daemons listening but are used by outgoing
50: # services like ftp and talk. For slightly more obscurity (though
51: # not much more security), the second commented out rule can chosen
52: # instead.
53: #
54: pass in on ppp0 proto tcp from any to any port 1024 >< 5000
55: #pass in on ppp0 proto tcp from any port = ftp-data to any port 1024 >< 5000
56: #
57: # Now allow various incoming TCP connections to particular hosts, TCP
58: # to the main nameserver so secondaries can do zone transfers, SMTP
59: # to the mail host, www to the web server (which really should be
60: # outside the firewall if you care about security), and ssh to a
61: # hypothetical machine caled 'gatekeeper' that can be used to gain
62: # access to the protected network from the outside world.
63: #
64: pass in on ppp0 proto tcp from any to ns1 port = domain
65: pass in on ppp0 proto tcp from any to mail port = smtp
66: pass in on ppp0 proto tcp from any to www port = www
67: pass in on ppp0 proto tcp from any to gatekeeper port = ssh