blacklistd: spurious whitelisting of IPs
Norman Gray
norman.gray at glasgow.ac.uk
Thu May 14 12:31:12 UTC 2020
Greetings.
My blacklistctl dump -a output currently looks a bit like this
address/ma:port id nfail last access
130.209.XX.XX/32:22 0/-1 1970/01/01 01:00:00
194.XX.XX.XX/32:22 3/-1 2020/05/14 00:35:05
[ IP addresses partially redacted ]
[...plus various reasonable-looking lines...]
Both those IP ranges are 'friendly', and the first is the local /16.
The odd thing is the -1 as the nfail limit, meaning 'do not block' or
'whitelisted', which I can't explain.
My blacklistd.conf looks like:
[local]
ssh stream * * * 4 24h
ftp stream * * * 3 24h
smtp stream * * * 3 24h
submission stream * * * 3 24h
* * * * * 3 60
[remote]
130.209.XX.XX:ssh * * * * * *
194.XX.XX.XX:ssh * * * * * *
130.209.XX.XX:ssh * * * * * *
The [local] stanza is almost the default; the [remote] explicitly
whitelists three machines.
But the whitelisted machines _do not_ match the nfail=-1 machines in the
blacklistctl output. They're in the same 130.209.0.0/16 and
194.0.0.0/8, but are not the same IP address. Looking further back, I
can see a similar pattern, with these netblocks, but no others,
apparently whitelisted. What's going on?
It's as if the local lines were being parsed as 130.209.0.0/16:ssh and
194.0.0.0/8:ssh, but there's nothing in the by-hand parser of the .conf
file that suggests that's what's happening (see
<https://github.com/freebsd/freebsd/blob/master/contrib/blacklist/bin/conf.c>
lines 224 and 586, last changed March 2018).
The machine this is running on is hosting a couple of jails (one of
which is the bastion host that this is really protecting, and the
blacklistd is listening on sockets in both the host and the bastion
jail), it has four IP addresses (two of which are in a private IP
range), and it has a non-trivial, but not particularly complicated pf
firewall configuration. This is the blacklistd in FreeBSD
12.0-RELEASE-p8 (I can't find a version option on blacklistd nor any
version strings in the blacklistd binary).
I'm perplexed.
Best wishes,
Norman
--
Norman Gray : http://www.astro.gla.ac.uk/users/norman/it/
Research IT Coordinator
SUPA School of Physics and Astronomy, University of Glasgow, UK
Charity number SC004401
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