Reset PF Firewall Automatically While Testing Configuration With Remote Server Over SSH Session

by on May 13, 2009 · 3 comments· LAST UPDATED April 11, 2014

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I would like to tell my BSD based PF firewall to flush out the current configuration every 2 minutes. This will help me, when I'm testing a new rules and configuration options.
Tutorial details
DifficultyEasy (rss)
Root privilegesYes
Requirements*BSD+pf
Estimated completion time1m
Some time I find myself locked out of my own remote server. How do I reset PF firewall automatically without issuing hard reboot?

There is no need to write a shell script and call it from cron. You can load the rules from the /etc/pf.conf and sleep or 120 seconds then disable pf using the following syntax:
#/sbin/pfctl -f /etc/pf.conf && sleep 120 && /sbin/pfctl -d
Where,

  • -f /etc/pf.conf - Load the rules contained in /etc/pf.conf.
  • -d - Disable the packet filter.
  • sleep 120: The sleep command suspends execution for a minimum of 200 seconds before calling the next command.

You can also test pf.conf for syntax errors using the following options:
# /sbin/pfctl -nf /etc/pf.conf
Finally, && (AND list) shell control operator is to used run next command only if, first command returns an exit status of zero. So each command in list must be successful in order to run next command.
# /sbin/pfctl -nf /etc/pf.conf && /sbin/pfctl -f /etc/pf.conf && sleep 120 && /sbin/pfctl -d

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{ 3 comments… read them below or add one }

1 gregf May 13, 2009 at 10:53 pm

This is great, although you might already have a working rule set. In which case you wouldn’t want to take down the whole firewall over a mistake. My working method has been about the same as above, but I keep new rules in there own file pf.testing. Then you can do the 120 second delay to load the original set if things went wrong. This way there is no open hole(s) in your firewall while your testing. Obviously it’s highly unlikely you’ll have an attack the moment you bring the firewall down. I just think it’s better practice if there is a choice.

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2 eigenheit June 23, 2009 at 1:22 am

Thinking about it the command -nf is very useful in testing new rules, you are always kept behind your trustful gateway.

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3 Nilesh January 17, 2011 at 10:16 am

Saviour!

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