ipfw and ssh problem
Tongai. T Zimbiti
tongai at yoafrica.com
Fri Mar 26 10:11:27 UTC 2010
will give that a try.
>> Hi guys,
>> I have searched everywhere and failed to find a solution, hence I write
>> I have installed 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:02:08
>> UTC 2009 root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
>> together with ipfw. The problem I have is this, if I am on the box I can
>> restart my firewall with no problem, but when I log in remotely and
>> restart the firewall for reason I am locked out and can not ssh into it.
>> Below is the messages log:
>> Mar 25 14:51:04 panadine kernel: Trying to mount root from ufs:/dev/ad4s1a
>> Mar 25 14:51:04 panadine kernel: ipfw2 (+ipv6) initialized, divert
>> loadable, nat loadable, rule-based forwarding disabled, default to deny,
>> logging disabled
>> Mar 25 14:51:06 panadine kernel: ae0: link state changed to UP
>> Mar 25 14:51:16 panadine ntpd: ntpd 4.2.4p5-a (1)
>> Mar 25 14:51:17 panadine nrpe: Starting up daemon
>> Mar 25 14:51:25 panadine ntpd: kernel time sync status change 2001
>> Mar 25 14:51:32 panadine su: systz to root on /dev/pts/0
>> Mar 25 15:01:46 panadine kernel: ifa_del_loopback_route: deletion failed
>> Mar 25 15:01:46 panadine kernel: ae0: link state changed to DOWN
>> Mar 25 15:01:47 panadine sshd: fatal: Write failed: Permission denied
>> Mar 25 15:01:48 panadine kernel: ae0: link state changed to UP
>> Here is a few lines from my /etc/firewall_rules
>> # vim: set syntax=pf :
>> -f flush
>> # Let me talk out
>> add 100 allow all from me to any out keep-state
>> add 101 allow icmp from any to any via any
>> add 102 allow udp from any to any 33434-33523
>> # Deal with loopback
>> #add 1000 allow all from any to any via lo0
>> add 1001 deny ip from any to 127.0.0.0/8
>> add 1002 deny ip from 127.0.0.0/8 to any
>> # Allow established and fragmented sessions
>> add 2000 allow tcp from any to any established
>> add 2001 allow ip from any to any frag
>> add 2002 check-state
>> add 2003 allow icmp from any to any
>> I have enabled net.inet.ip.fw.verbose=1 in /etc/sysctl.conf
>> please help
> ipfw -f flush - deletes all rules except the default which is usually
> 'deny from any to any'
> As soon as that gets processed, your sshd connection is killed as seen in
> the message up there:
> sshd: fatal: Write failed: Permission denied
> With ssh dead, your shell is terminated and the rest of the script is
> never ran, so you are stuck with a firewall that did not get any rules
> added to it.
> Using quiet 'ipfw -q' or doing 'sh /etc/rc.firewall > /dev/null ; sleep 3'
> is what I've usually done.
> or my favorite is to do the firewall from 'local console' using 'watch -W
> v4' so even if ssh is killed, the console is up to finish up the script.
> [ this works great for 'buildworld' too where I want to start it, pack my
> laptop and and leave, reconnecting later ]
> With quiet mode, ssh is not sending anything back, so the connection is
> not terminated.
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