How to setup IPFW working with blacklistd
Ian Smith
smithi at nimnet.asn.au
Mon Nov 6 14:10:11 UTC 2017
In freebsd-questions Digest, Vol 701, Issue 1, Message: 10
On Mon, 6 Nov 2017 09:38:40 +0100 Cos Chan <rosettas at gmail.com> wrote:
> Hi All
>
> I would run IPFW with blacklistd, my FreeBSD is 11.1-RELEASE-p1.
>
> my blacklistd is working fine to get sshd failed login attempts.
> The out put:
>
> $ sudo blacklistctl dump -b
> address/ma:port id nfail last access
> 1.1.1.1/32:22 3/-1 2017/11/05 01:05:34
> 2.2.2.2/32:22 3/-1 2017/11/05 13:22:53
>
> but I can't find information how to use the blacklistd database in IPFW
> from IPFW manpage
>
> would anybody explain that to me?
By all means work with Carmel's offer to look at parsing the database
output. All I know about blacklistd(8), blacklistd.conf(5) and
blacklistctl(8) is what I just now read skimming these manual pages.
However I was surprised to see no mention of using tables rather than
add)ing or rem)oving individual firewall rules - and you can't use
'flush' on individual rules in ipfw(8), only on whole sets of rules.
Amother problem with adding/removing individual rules is you need to
allocate a large enough block of rules, then specify distinct rule
numbers to ipfw(8). Messy and error-prone, especially for deleting.
So you might need to replace or modify /usr/libexec/blacklistd-helper,
which I haven't seen but assume is a script, to use its parameters to
generate commands more like:
/sbin/ipfw table $TABLENAME add addr[/masklen] [value]
and
/sbin/ipfw table $OTHERNAME delete addr[/masklen]
as appropriate. This is immensely more efficient than adding and
deleting single rules on the fly, moreso if there are many entries.
When adding entries, the optional [value] might be a latest timestamp,
or an expiry timestamp, or anything else you might find useful.
Of course you may need a number of different tables, for blocking ssh,
webhosts, mailserver or other services, but then need just a few rules
dedicated to denying (or even specifically enabling) hosts or ports to
addr[/masklen/ entries in a particular table.
ipfw add deny tcp from table \($SPAMMERS\) to any 25,587 setup
ipfw add deny tcp from table \($SSHBADGUYS\) to me 22 setup
ipfw add deny all from table \($REALLYNASTY\) to any in
and such. Tables really are the way to go for this sort of thing.
cheers, Ian
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