ipfw question

Thu Jun 30 15:32:44 UTC 2016

I had an oddball occurence this A.M. I sat down to check E-mails & surf 
& found that I couldn't recover any E-mails. I poked around a bit & 
found some entries in /var/log/security indicating that traffic from my 
DNS server was being dropped by the firewall:

[root at kabini1, ~, 10:04:03am] 587 % tail -20 /var/log/security ; date
May 31 09:18:41 kabini1 last message repeated 6 times
Jun 19 13:23:53 kabini1 kernel: ipfw: 65500 Deny TCP 163.172.131.88:993 
192.168.0.27:47277 in via re0
Jun 19 13:23:57 kabini1 last message repeated 4 times
Jun 26 08:34:13 kabini1 kernel: ipfw: 65500 Deny TCP 212.47.233.86:9001 
192.168.0.27:28210 in via re0
Jun 26 08:34:17 kabini1 last message repeated 4 times
Jun 26 09:23:39 kabini1 kernel: ipfw: 65500 Deny TCP 193.0.6.135:43 
192.168.0.27:60843 in via re0
Jun 26 09:23:42 kabini1 last message repeated 3 times
Jun 27 09:47:14 kabini1 kernel: ipfw: 65500 Deny TCP 212.47.233.86:9001 
192.168.0.27:54688 in via re0
Jun 27 09:47:18 kabini1 last message repeated 4 times
Jun 27 11:55:17 kabini1 kernel: ipfw: 65500 Deny TCP 212.47.233.86:9001 
192.168.0.27:45670 in via re0
Jun 27 11:55:21 kabini1 last message repeated 4 times
Jun 30 08:24:04 kabini1 kernel: ipfw: 65500 Deny UDP 209.244.0.3:53 
192.168.0.27:46927 in via re0
Jun 30 08:25:30 kabini1 kernel: ipfw: 65500 Deny UDP 209.244.0.3:53 
192.168.0.27:44681 in via re0
Jun 30 08:25:32 kabini1 kernel: ipfw: 65500 Deny UDP 209.244.0.3:53 
192.168.0.27:29687 in via re0
Jun 30 08:27:20 kabini1 kernel: ipfw: 65500 Deny UDP 209.244.0.3:53 
192.168.0.27:51623 in via re0
Jun 30 08:34:56 kabini1 kernel: ipfw: 65500 Deny UDP 209.244.0.3:53 
192.168.0.27:46764 in via re0
Jun 30 08:34:57 kabini1 kernel: ipfw: 65500 Deny UDP 209.244.0.3:53 
192.168.0.27:24172 in via re0
Jun 30 08:48:04 kabini1 kernel: ipfw: 65500 Deny TCP 163.172.131.88:993 
192.168.0.27:42869 in via re0
Jun 30 08:48:46 kabini1 last message repeated 17 times
Jun 30 08:50:41 kabini1 last message repeated 5 times
Thu Jun 30 10:04:07 MCDT 2016
[root at kabini1, ~, 10:04:07am] 588 %

I haven't made any changes to my firewall setup in months, maybe a year 
or more (so long that I found I had forgotten what to do initially :-/ 
). I eventually recalled where to tweak & added a line to my rc.fiewwall 
file & restarted ipfw. It spit out all rules, including my new one, 
which implied that I hadn't botched the syntax. E-mail went back to 
working & all is well. However, I want to make sure I didn't open up 
more than I think I am. My rule list as echoed out from the restart is 
below:

[root at kabini1, /etc, 8:52:59am] 467 % service  ipfw restart
net.inet.ip.fw.enable: 1 -> 0
net.inet6.ip6.fw.enable: 1 -> 0
Flushed all rules.
00100 allow ip from any to any via lo0
00200 deny ip from any to 127.0.0.0/8
00300 deny ip from 127.0.0.0/8 to any
00400 deny ip from any to ::1
00500 deny ip from ::1 to any
00600 allow ipv6-icmp from :: to ff02::/16
00700 allow ipv6-icmp from fe80::/10 to fe80::/10
00800 allow ipv6-icmp from fe80::/10 to ff02::/16
00900 allow ipv6-icmp from any to any ip6 icmp6types 1
01000 allow ipv6-icmp from any to any ip6 icmp6types 2,135,136
01100 check-state
01200 allow tcp from me to any established
01300 allow tcp from me to any setup keep-state
01400 allow udp from me to any keep-state
01500 allow icmp from me to any keep-state
01600 allow ipv6-icmp from me to any keep-state
01700 allow udp from 0.0.0.0 68 to 255.255.255.255 dst-port 67 out
01800 allow udp from any 67 to me dst-port 68 in
01900 allow udp from any 67 to 255.255.255.255 dst-port 68 in
02000 allow udp from fe80::/10 to me dst-port 546 in
02100 allow udp from any 53 to me in                # <-------- my new 
rule !!!!
02200 allow icmp from any to me icmptypes 8
02300 allow ipv6-icmp from any to any ip6 icmp6types 128,129
02400 allow icmp from any to me icmptypes 3,4,11,13
02500 allow ipv6-icmp from any to any ip6 icmp6types 3
02600 allow tcp from 192.168.0.0/24 to me
02700 allow udp from 192.168.0.0/24 to me
02800 allow udp from 192.168.0.0/24 513 to 192.168.0.0/24 dst-port 513
02900 allow udp from 192.168.0.0/24 525 to 192.168.0.0/24 dst-port 525
65000 count ip from any to any
65100 deny { tcp or udp } from any to any dst-port 111,137,138 in
65200 deny { tcp or udp } from 192.168.0.0/24 to me
65300 deny ip from any to 255.255.255.255
65400 deny ip from any to 224.0.0.0/24 in
65500 deny udp from any to any dst-port 520 in
65500 deny tcp from any 80,443 to any dst-port 1024-65535 in
65500 deny log logamount 50000 ip from any to any
Firewall rules loaded.
[root at kabini1, /etc, 8:53:11am] 468 %

with my new rule marked. I noticed that the dropped DNS packets were 
destined for oddball ports on my box, so I have no port specification in 
my rule. Am I just allowing DNS replies back in, or 
(humorously/tragically) more :-) ? This box is my daily driver 
workstation desktop, *NOT* a public server, so I want it locked down as 
much as possible.

[root at kabini1, /etc, 8:53:11am] 468 % uname -a
FreeBSD kabini1.local 9.3-RELEASE-p33 FreeBSD 9.3-RELEASE-p33 #0: Wed 
Jan 13 17:55:39 UTC 2016 
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
[root at kabini1, /etc, 10:22:42am] 469 %

TIA & have a good one.

-- 

	William A. Mahaffey III

  ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.