ipfw statefull ruleset problem
gmeijer at palmweb.nl
Sat Jan 29 12:52:30 PST 2005
First of all, I'm not very experienced with ipfw, so if this is a stupid question, I'm sorry.
I have a question regarding my statefull ipfw ruleset. I have the following rules:
$cmd 00015 check-state
$cmd 00200 allow tcp from any to any 80 out via $pif setup keep-state
$cmd 00231 allow tcp from any to any 110 out via $pif setup keep-state
$cmd 00283 allow tcp from any to any 21 out via $pif setup keep-state
# Allow in standard www function because I have apache server
$cmd 00400 allow tcp from any to me 80 in via $pif setup limit src-addr 2
# Allow in FTP
$cmd 00410 allow tcp from any to me 21 in via $pif setup limit src-addr 2
# Allow in mail
$cmd 00420 allow tcp from any to me 110 in via $pif
(there are more rules, but these are the ones that it's about)
The problem that I'm having is that I can't check mail, and can't FTP and see a lot of:
ipfw: 299 Deny TCP [my-server-ip]:80 [some-ip]:[some-port-other-than-80] out via em0
messages in my logfile.
When I try to check mail I see in my log:
ipfw: 299 Deny TCP [my-server-ip]:110 [my-home-pc-ip]:[some-port-other-than-110] out via em0
What happens (I think, as far as I understand ipfw), there is an connection setup on port 21/80/110 (ftp/http/mail), which is allowed by the rules. A dynamic rules is created, but then the other computer switches ports. The check-state command checks for a dynamic rule, but the port doesn't match anymore and so it doesn't find a dynamic rule and the other rules also don't apply, since they only allow connection initialization. Am I correct?
I can solve all this by putting in the rule:
# $cmd 00020 allow tcp from any to any established
But I learned that that is not the right way to do this in a statefull ruleset, because the dynamic rules don't have any use in this way. So what is the right way to solve this?
Thanks a lot in advance!
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