Marco Gonçalves

A couple of years ago I posted my Qmail installation guide, and has expected it served me good when was time to reform to the old mail server. But, i made some changes on this iteration and i think is more polished and shiny than ever.

Again, this is to my own reference, but i will be very glad if it also can help someone. On the other hand, if you follow it, and nukes your system or kills every life form on Earth please don’t blame me. You are warned.

The old picture:

2 Qmail instances, 1 published MX record that accepts emails from other MTAs, does the RBL checks and forwards the passed emails to the main Qmail instance via artificial smtproutes. The forwarded emails are then checked against virus (by Clamav) and spam (by SpamAssassin) trough qmail-scanner qmail-queue drop in replacement.

Users receive and send email trough the non published MX Qmail instance. They need to smtp-auth to relay email (send email to remote domains). Delivery to local domains doesn’t require smtp-auth.

Identified problems:

1 – One problem is that the main Qmail instance (that has no published MX records), that works with Vpopmail and holds all the accounts information, maildirs and email is somehow vulnerable:

The main weakness of this installation, is that if a clever spammer discovers that mail.domain.com accepts incoming emails for local domains, he can spam down your users bypassing the rbl tests.

also, one has to rememeber that has SPF and A records published, and it’s IP is printed on all outgoing email headers, so it’s not anonymous.

2 – The user debug is somewhat tricky, if there is a smtp-auth client configuration problem. The problem is that the user will be able to send emails to local domains, but will get the dreadful 553 sorry that domain isn’t in my list of allowed rcpthosts (#5.7.1) error.

3 – Qmail-scanner, is a very neat piece of software, but it is fundamentally flawed performance wise because for each and every email it must load the PERL interpreter.

4 – Restarting Qmail every 15m to recognize new or deleted domains is plain dumb.

The new picture:

All of the previous mentioned issues have been addressed and polished. The main Qmail instance (mail) will only accept outside authenticated connections for both local and remote deliveries. The external email comes trough the published mx record Qmail instance only, filtered by rbl, then routed to Amavis for virus and spam scans, and finally routed to the main Qmail instance (if virus and spam free). In this scenario you must trust your customers, because as they authenticate and send emails, these will bypass all the virus and spam checks.

Let’s put our hands to work, the first slice is on point 15 of the original guide “Clam Anti Virus, Spam Assassin and Qmail-scanner”, this version will move the virus and spam filter to the other Qmail instance. So follow the original guide until point 15, and then:

1 – Install qfilter

cd /usr/ports/mail/qmail-qfilter/
make install clean

2 – Make a shell script wrapper that will invoke the filters used by qfilter

mkdir -p /var/qmail/qfilter
edit /var/qmail/qfilter/qfilter-wrapper

and put these contents on the file

#!/bin/sh
exec /usr/local/bin/qmail-qfilter /var/qmail/qfilter/smtp-auth-only

save and mark it executable

chmod +x /var/qmail/qfilter/smtp-auth-only

Note:
actually there is only one filter being invoked (smtp-auth-only), but qfilter supports several filters (exec /usr/local/bin/qmail-qfilter /path/to/filter-one –/path/to/filter-two –/path/to/filter-three)

3 – Install the smtp-auth-only filter

This is just a very simple perl script that will test the presence of the environment variable TCPREMOTEINFO, as this variable is only set upon successful smtp-auth. If the mail comes from an authenticated user the script returns 0, else if it’s from a non-authenticated user the script returns 31 signaling a permanent error.

edit /var/qmail/qfilter/smtp-auth-only

the script is very simple

#!/usr/local/bin/perl

if (defined $ENV{'TCPREMOTEINFO'} == false) {
        use Sys::Syslog qw(:DEFAULT :standard);
        openlog("qfilter", 'ndelay,pid', 'mail');
        syslog('info', "No SMTP-Auth - Rejecting Email");
        exit 31;
}

exit 0;

save it and mark it executable

chmod +x /var/qmail/qfilter/smtp-auth-only

4 – Adjust /etc/tcp.smtp to use qfilter

this is my last line now of /etc/tcp.smtp

:allow,MAXLOAD="2000",SPFBEHAVIOR="0",RBLSMTPD="",QMAILQUEUE="/var/qmail/qfilter/qfilter-wrapper"

it accepts connections from everywhere (if cpu load > 20 rejects connections) it bypasses SPF and RBL checks, and it uses qfilter-wrapper as qmailqueue. After

qmailctl cdb

to build the new smtp tcp rules cdb file and reload qmail, the main Qmail instance will only accept authenticated user email. Email routed from mx should match a previous /etc/tcp.smtp rule.

5 – Install Clam Anti Virus, Spam Assassin and Amavis

This step kind of mimics the step 15 on the original guide, with two main differences. We are installing all the filtering software on the MX instance of Qmail. And qmail-scanner as been replaced by Amavis.

So, log in to the MX console and install the software.

cd /usr/ports/security/clamav
make install clean

options selected: ARC, ARJ, DMG_XAR, DOCS, ICONV, LHA, LLVM, TESTS, UNRAR, UNZOO

cd /usr/ports/mail/spamassassin
make install clean

options selected: AS_ROOT, GNUPG, UPDATE_AND_COMPILE, DCC, DKIM, PYZOR, RAZOR, RELAY_COUNTRY

cd /usr/ports/security/amavisd-new
make install clean

options selected: ALTERMIME, ARC, ARJ, BDB, CABS, DOCS, FILE, FREEZE, LHA, LZOP, MSWORD, MYSQL, P7ZIP, RAR, RPM, SPAMASSASSIN, TNEF, UNARJ, ZOO

as always on FreeBSD the installation is easy and a breeze. Now the fun part, configuring and make all this work together…

6 – Configure Clam Anti Virus

First ClamAV and FreshClam (the anti-virus updater daemon). Here’s a comment striped out of /usr/local/etc/clamd.conf

LogSyslog yes
LogFacility LOG_MAIL
LogVerbose yes
ExtendedDetectionInfo yes
PidFile /var/run/clamav/clamd.pid
DatabaseDirectory /var/db/clamav
LocalSocket /var/run/clamav/clamd.sock
FixStaleSocket yes
ReadTimeout 300
CommandReadTimeout 5
User vscan
AllowSupplementaryGroups yes
ScanMail yes

and the comment stripped version of /usr/local/etc/freshclam.conf

DatabaseDirectory /var/db/clamav
LogVerbose yes
LogSyslog yes
LogFacility LOG_MAIL
PidFile /var/run/clamav/freshclam.pid
DatabaseOwner vscan
AllowSupplementaryGroups yes
DatabaseMirror database.clamav.net
NotifyClamd /usr/local/etc/clamd.conf

There are few modifications to the distribution configuration files, mainly 2 things, to run clamd/freshclam daemons as the user ‘vscan’, the same user that will run amavis, and to log via syslog mail facility.

It makes perfect sense to take advantage of syslog and newsyslog automatic maintenance and log rotation. Also, having most of stuff logging to /var/log/mail makes it easy to spot any error message outputted by any of the several components. The downsize, is that in a busy server the log can become a bit messy.

Adjust the ownership on ClamAV directories:

chown -R vscan:vscan /var/db/clamav
chown -R vscan:vscan /var/run/clamav

add the rcvars to /etc/rc.conf
clamav_clamd_enable=”YES”
clamav_freshclam_enable=”YES”

and start both of the daemons

/usr/local/etc/rc.d/clamav-clamd start
/usr/local/etc/rc.d/clamav-freshclam start

7 – Configure Spamassassin

First, as Spamassassin uses the GeoIP database, you should have an updated database on /usr/local/share/GeoIP/GeoIP.dat, to do so automaticaly write this file on /usr/local/etc/periodic/daily/updategeoip

#!/bin/sh

cd /usr/local/share/GeoIP
/usr/local/bin/wget -q http://geolite.maxmind.com/download/geoip/database/GeoLiteCountry/GeoIP.dat.gz
gzip -d -f GeoIP.dat.gz

exit 0

and mark it executable

chow +x /usr/local/etc/periodic/daily/updategeoip

and run it manually (you should have installed on your system /usr/ports/ftp/wget)

/usr/local/etc/periodic/daily/updategeoip

update and compile Spamassassin rules

sa-update
sa-compile

and make this process automatic, edit /usr/local/etc/periodic/weekly/spamassassin

#! /bin/sh

/usr/local/bin/sa-update && /usr/local/bin/sa-compile

exit 0

mark it executable, and run by hand the first time

chmod +x /usr/local/etc/periodic/weekly/spamassassin

Spamassassin doesn’t need so much configuration, and it pretty much works out of the box, but i made some fine tuning to everything play happy, so there it is the commented striped version of /usr/local/etc/mail/spamassassin/local.cf

use_dcc 1
dcc_home /var/dcc
dcc_path /usr/local/bin/dccproc
dcc_timeout     10
add_header all  DCC _DCCB_: _DCCR_
use_pyzor 1
pyzor_path /usr/local/bin/pyzor
use_razor2 1
razor_config /var/amavis/.razor/razor-agent.conf
score RAZOR2_CHECK 2.500
score PYZOR_CHECK 2.500
score DCC_CHECK 4.000

create the /var/amavis/.razor directory, and set up razor

mkdir /var/amavis/.razor
razor-admin -home=/var/amavis/.razor -create
razor-admin -home=/var/amavis/.razor -discover

and change ownership to the vscan user

chown -R vscan:vscan /var/amavis/.razor

time to set up the rc vars at /etc/rc.conf and start Spamassassin (replace aaa.bbb.ccc.ddd for the allowed IP address to connect)

spamd_enable="YES"
spamd_flags="-A 127.0.0.1,aaa.bbb.ccc.ddd"

and start it

/usr/local/etc/rc.d/sa-spamd start

8 – Configure Amavis

Amavis will be the glue between Qmail and ClamAV and Spamassassin in a dual MTA setup. It will accept routed emails from Qmail (mx instance) on port 10024, fiter, and re-route to the main Qmail for local delivery (email instance).

Here it is the /usr/local/etc/amavisd.conf configuration file. Now some customizations required to amavis work properly:

• set $mydomain and $myhostname to your host fqdn
• configure $forward_method = ‘smtp:[aaa.bbb.ccc.ddd]:25’; Set aaa.bbb.ccc.ddd to the IP address of the main Qmail instance (email host) to where the filtered emails are forward. Remember that in the Qmail instance you need a corresponding entry in /etc/tcp.smtp that accepts the forward emails and skips SPF and RBL checks (replace aaa.bbb.ccc.ddd for the incoming IP of Amavis):
  aaa.bbb.ccc.ddd:allow,MAXLOAD=”2000″,SPFBEHAVIOR=”0″,RBLSMTPD=””,QMAILQUEUE=”/var/qmail/bin/qmail-queue”
• the $max_servers should, as commented, match the width of your MTA pipe /var/qmail/control/concurrencylocal
• @local_domains_maps = [‘.’]; we accept every incoming email as a local domain email, because by configuration the mx Qmail instance will only accept and forward to Amavis emails to local domains
• customize $inet_socket_bind, generally the loopback address IP should be fine, but if your are running inside a jail (and if you are following this guide you are) replace the loopback IP for the main jail IP
• setup @inet_acl list (this is space delimited list of IPs that Amavis will accept email from). If you are running everything in the same jail (Qmail mx instance and Amavis) this is the main jail IP, if Qmail mx is running in other jail or host add the mx Qmail outgoing IP

These are some of the most important things that you should consider to setup Amavis to your own taste, and as pretty neat software everything (or just about everything) is customizable. The configuration file has extensive comments so it’s easy to understand each and every option:

• In this setup Amavis is logging to syslog mail facility, $DO_SYSLOG = 1; and $SYSLOG_LEVEL = ‘mail.info’; scroll up to find out why. You can change this to a $LOGFILE. Also setup the $log_level
• Virus, banned and spam (after $sa_kill_level_deflt threshold) emails are plain discarded, bounce only in case of bad headers.
  $final_virus_destiny = D_DISCARD; # (defaults to D_DISCARD)
  $final_banned_destiny = D_DISCARD; # (defaults to D_BOUNCE)
  $final_spam_destiny = D_DISCARD; # (defaults to D_BOUNCE)
  $final_bad_header_destiny = D_BOUNCE; # (defaults to D_PASS), D_BOUNCE suggested
• you can customize $virus_admin and $spam_admin with a email address to receive reports when virus/spam email is detected, in this case you should also configure the from addresses in $mailfrom_notify_admin, $mailfrom_notify_recip, $mailfrom_notify_spamadmin
• this configuration example does not notify me of positives, but i keep them in a quarantine dir, so i can do postmortem analysis and recovery,
  $QUARANTINEDIR = ‘/var/virusmails’;
  # Separate quarantine subdirectories virus, spam, banned and badh within
  # the directory $QUARANTINEDIR may be specified by the following settings
  # (the subdirectories need to exist – must be created manually):
  $virus_quarantine_method = ‘local:virus/virus-%i-%n’;
  $spam_quarantine_method = ‘local:spam/spam-%b-%i-%n’;
  $banned_files_quarantine_method = ‘local:banned/banned-%i-%n’;
  $bad_header_quarantine_method = ‘local:badh/badh-%i-%n’;
• you can also customize the spam score required to each action
  $sa_tag_level_deflt = undef; # always add spam info headers
  $sa_tag2_level_deflt = 5.0; # subject will be re-written with $sa_spam_subject_tag value
  $sa_kill_level_deflt = 10; # email will not be delivered, and we keep a copy in quarantine
  $sa_dsn_cutoff_level = 15; # Since we are using D_DISCARD, this setting will serve no purpose, but if you were using D_BOUNCE, you can use this to set a level at which the sender will no longer be notified

and many more options that you can/should look into. If you are going to quarantine emails you should create the quarantine directories:

mkdir -p /var/virusmails/badh/
mkdir -p /var/virusmails/banned/
mkdir -p /var/virusmails/spam/
mkdir -p /var/virusmails/virus/

chown -R vscan:vscan /var/virusmails

also, it’s not a bad idea to put a line in root cron to delete older (30 days older) quarantined emails:

crontab -e

05 05 * * * /usr/bin/find /var/virusmails/* -type f -mtime +30 -exec /bin/rm -f {} \;

Finally! add the rc var at /etc/rc.conf

amavisd_enable="YES"

and start it

/usr/local/etc/rc.d/amavisd start

9 – Configure Qmail to use Amavis

Just a simple php script run every 10 minutes by cron will take care of this. As a bonus when you add, rename or delete a domain the Qmail mx instance will pick up the changes.

Edit /var/qmail/control/make_smtp_routes and adjust aaa.bbb.ccc.dd with the Amavis listening IP:port ($inet_socket_bind in amavisd.conf):

#! /usr/local/bin/php
<?php

$smtp_route = 'aaa.bbb.ccc.ddd:10024';

$rcpthosts     = file('/var/qmail/control/rcpthosts');
$morercpthosts = file('/var/qmail/control/morercpthosts');

$hosts = array_merge($rcpthosts, $morercpthosts);
$hosts = array_filter($hosts);

$fp = fopen("/var/qmail/control/smtproutes.tmp", "w");
foreach ($hosts as $host)
    fwrite($fp, trim($host).":".$smtp_route."\n");
fclose($fp);

if (md5_file('/var/qmail/control/smtproutes.tmp') == md5_file('/var/qmail/control/smtproutes')) {
    unlink('/var/qmail/control/smtproutes.tmp');
    exit(0);
}

openlog('PHP', LOG_ODELAY|LOG_PID, LOG_MAIL);
syslog(LOG_INFO, "New /var/qmail/control/smtproutes");

rename("/var/qmail/control/smtproutes.tmp", "/var/qmail/control/smtproutes");

syslog(LOG_INFO, "Restarting Qmail");
exec('/root/bin/qmailctl restart');

exit(0);

?>

mark it executable

chown +x /var/qmail/control/make_smtp_routes

and add it to cron

cron -e
*/10 * * * * /var/qmail/control/make_smtp_routes > /dev/null 2>&1

That’s it, this is the end. Now go grab a well deserved beer and behold your brand new system.

Final toughts

The system is cool, addressed the issues of the old system and is maintenance free. But, there is some space to improvements:
– develop an API (work in progress) that allows for administration, domain management and email management of the system. With this piece in place is then easy to integrate and develop admin and control panels that replace the outdated qmailadmin panel and administrative tasks on the command line.
– related with the API, to give domain managers the possibility to fine tune per domain anti-virus, spam, quarantine and notification settings. This also implies a deeper knowledge of Amavis configuration.
– to compile a complete and comprehensive guide that incorporates the original guide and the stuff on this one.

FIN and CLOSED 🙂