Problem with spamlogd

Matthew Seaman m.seaman at
Sun Jun 17 13:30:03 UTC 2012

On 17/06/2012 11:45, Doug Hardie wrote:
> I am using spamd on several systems and started encountering a problem awhile ago with FreeBSD 7.2 servers, but let it go since I am in the process of upgrading the servers.  However, I now am encountering the same issue on FreeBSD 9.0 with spamlogd.  It never reads pflog0.  pflogd reads the entries just fine.  I set up syslog to log all the spamlogd messages and when spamlogd is started it gives:
> spamlogd: Listening on pflog0 for all interfaces. 
> lsof shows that it is connected to bpf0 as is pflogd.  However, pflogd shows an offset into the file that appears to be the end of the file.  spamlogd shows an offset of 0.  It is periodically reading the file as shown by ktrace but always getting back a 0 size return.  spamd itself is working just fine.  However, the expiration times are not being updated so white entries are timed out way too often.  spamlogd used to update them.  The rc.conf entries are:
> obspamd_enable="YES"
> obspamd_flags="-G 2:1:1728"
> obspamd_setup_flags=""
> obspamd_grey=YES
> obspamlogd_enable="YES"
> obspamlogd_flags="-W 1728"
> These were established a few years ago and worked up till short while ago.  I don't recall any changes I made to anything, but…
> Looking through the spamlogd source it appears to be building a filter for the pcap routines with:
> "ip and port 25 and action pass and tcp[13]&0x12=0x2"
> Using that filter on pflog yields no output.  I believe the pass item requires there to be some logging of the pass actions and those are not appearing in the pflog or in the pfctl counts for those rules.  I suspect that is the problem.  The pf.conf is: (mail server is on this machine)
> ext_if="em0"
> table <blackhole> persist file "/etc/blackhole"
> table <spamd> persist
> table <spamd-white> persist
> table <spamd-white-local> persist file "/etc/mail/whitelist"
> no rdr on { lo0, lo1 } from any to any
> no rdr on { lo0, lo1 } from any to any
> MAILHOSTS = "{}"
> rdr pass log on $ext_if inet proto tcp from <spamd-white-local> to port smtp -> port smtp
> rdr pass log on $ext_if inet proto tcp from <spamd-white> to port smtp -> port smtp
> rdr pass log on $ext_if inet proto tcp to $MAILHOSTS port smtp -> port spamd
> pass in on lo0
> pass in log on $ext_if inet proto tcp to port smtp
> pass out log on $ext_if inet proto tcp from to any port smtp
> block in quick log on $ext_if from <blackhole> to any

You seem to be logging all the SMTP traffic that passes through pf in
any direction.  Which doesn't make a lot of sense to me -- obspamlogd
will see the logged SMTP packets, assume that's valid traffic and add
the hosts to the whitelist.  Even if that's the incoming SYN packet from
some dubious mailer trying to inject you full of spam.

You should only log the SYN packets going out of your upstream (egress)
interface for obspamlogd -- that way it immediately whitelists anyone
you send email to, so they can reply without delay due to greylisting.

A good way of doing that is to log SMTP traffic to a separate log
device. eg:

pass log (to pflog1) on $ext_if proto tcp \
     from any to any port smtp            \
     flags S/SA keep state

then in /etc/rc.conf, tell obspamlogd to use pflog1:

obspamlogd_flags="-i em0"

That way you can keep pflog0 for doing the normal packet logging that is
usual with pf -- typically, logging anything that gets dropped by the
firewall -- without getting obspamlogd confused.



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP:     Ramsgate
JID: matthew at               Kent, CT11 9PW

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