HOWTO_Install_Courier_with_maildrop_and_ClamAV_and_SpamAssassin

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Introduction

Background

After installing Courier I went started trying to get maildrop to filter the incoming email - without much luck unfortunately. So I naively turned to the courier-users mailinglist hoping for help - didn't get much there either. So now that I've gotten things working I (with some encouraging) decided to make this article.

Assumptions

• When writing this I have already installed everything - and it was a couple of months ago so everything here might not work out-of-the-box. If that is the case I expect you to be able to solve it (and hopefully edit this page so that it is correct).
• You will be using virtual users - i.e. the users for the system will be fetched from a MySQL database
• SpamAssassin user-defined rules will also be stored in a MySQL database.
• Your mailboxes are correctly configured (you should be able to recieve mail if you start courier after configuring the Courier-MTA)
• You know how to add scripts to a runlevel (to start automatically at boot)
• You will be using IMAP-SSL only to access mail (webmail should work as well - but is not covered)
• You will want to be able to use ESMTP-SSL

Environment

You should have a working Courier mailsystem working before venturing any further. You can use HOWTO Email Virtual Hosting with Courier and MySQL to accomplish this

Versions

This HOWTO was written/has been updated to work with (later probably works, but config files might be in other locations)

• mail-mta/courier-0.50.1 (or mail-filter/maildrop-1.8.0-r3, but not *guaranteed* to work)
• mail-filter/spamassassin-3.1.0
• app-antivirus/clamav-0.87.1

Disclaimer

The HOWTO is provieded as-is - neither I nor any one else who has edited this article can be held responsible if your system goes haywire after following this HOWTO.

Installing software

ClamAV

emerge clamav

SpamAssassin

emerge spamassassin

Configuring software

ClamAV

 
#!/bin/bash
# Created by Tom Walsh, slim at ala.net
# slightly modified by Wolfgang Ziegler, nuppla at gmx.at

RUN=clamscan
# Enable this line, if you are using the clamav-daemon.
# RUN=clamdscan


#start
MSG=$(< /proc/self/fd/0) # stdin -> $MSG
SCAN=$(echo "$MSG" | $RUN - --stdout --disable-summary)
EXIT="$?"
VIRUS=$(echo "$SCAN" | awk '{print $2}')
SUBJECT=$(echo "$MSG" | reformail -x Subject:)

if [ "$EXIT" == "1" ]; then
 SUBJECT="**VIRUS** [$VIRUS] $SUBJECT"
 MSG=$(echo "$MSG" | reformail -i"X-Virus-Status: INFECTED")
 MSG=$(echo "$MSG" | reformail -i"Subject: $(echo "$SUBJECT")")
else
 MSG=$(echo "$MSG" | reformail -i"X-Virus-Status: CLEAN")
fi

echo "$MSG"
exit 0
  

Don't forget to make the file executable...

chmod +x /usr/bin/clamscan.sh

I did not need to change any of the ClamAV configuration files to get it to work.

SpamAssassin

For this to work you need to have the appropiate perl module installed - for MySQL you get it by

emerge Msql-Mysql-modules

Creating the user and database in MySQL

Execute these commands in mysql:

CREATE DATABASE spamassassin;
USE spamassassin;
CREATE TABLE userpref (
 id int(8) unsigned NOT NULL auto_increment,
 username varchar(128) NOT NULL default '',
 preference varchar(64) NOT NULL default '',
 value varchar(128) default NULL,
 descript varchar(128) default NULL,
 added datetime NOT NULL default '2003-01-01 00:00:00',
 added_by varchar(128) NOT NULL default '',
 modified timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
 UNIQUE KEY id (id),
 KEY type (preference),
 KEY added_by (added_by),
 KEY preference (preference),
 KEY username (username)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COMMENT='Spamassassin Preferences';
GRANT SELECT ON spamassassin.* TO spamassassin@localhost IDENTIFIED BY '<password>';
FLUSH PRIVILEGES;

Change <password> with some suitable password.

Applying settings in SpamAssassin

Add

user_scores_dsn                  DBI:mysql:spamassassin:localhost:3306
user_scores_sql_password         <password>
user_scores_sql_username         spamassassin
user_scores_sql_custom_query     SELECT preference, value FROM _TABLE_ WHERE username = _USERNAME_ OR  username = '$GLOBAL' OR username = CONCAT('%',_DOMAIN_) ORDER BY username ASC

to /etc/spamassassin/secrets.cf (and don't forget to enter the correct password to be used...)

And at last you need to change the SPAMD_OPTS option in /etc/conf.d/spamd to look something like this:

SPAMD_OPTS="-m 5 -q -x -H -u mail"

Here "-q -x" is essential to get it to read preferences from database. The option "-c" should be there as default and must be removed - see the manpage for spamd for the reason.

Getting Courier-MTA to send mail thru maildrop

To get the mail to be filtered throught maildrop you can put a file ".courier" in the homedir of each virtual mail user (it should be a single directory) and inside this file write:

| /usr/bin/maildrop

or for a global configuration, so every mail is filtered open the file /etc/courier/courierd and set:

DEFAULTDELIVERY="| /usr/bin/maildrop"

Be sure of the pipe " | " at the beginning.

Getting maildrop to filter the mail thru ClamAV and SpamAssassin

This is the default maildropfile for the entire system - I'm unclear on if this file is processed before or after the user .maildrop files.

 
# Only scan mails smaller than VSCANSIZE for a virus
VSCANSIZE="2000000"

# Only scan mails smaller than SCANSPAMSIZE for spam
SCANSPAMSIZE="200000"

###############################################################################
#
# Use ClamAV to scan for viruses.
#
###############################################################################

if( $SIZE < $VSCANSIZE ) 
{
  exception {
    xfilter "/usr/bin/clamscan.sh"
  }
}
 
if(/^X-Virus-Status:.*INFECTED/)
{
  `test -d $DEFAULT/.Quarantine`
  if ( $RETURNCODE == 1 )
  {
    `/usr/bin/maildirmake -f Quarantine $DEFAULT`
    `echo INBOX.Quarantine >> $DEFAULT/courierimapsubscribed`
  }
  exception {
    to "$DEFAULT/.Quarantine/"
  }
}

###############################################################################
#
# Use SpamAssassin to filter SPAM
#
###############################################################################
if( $SIZE < $SCANSPAMSIZE ) 
{
  xfilter "/usr/bin/spamc -u $USER -s $SCANSPAMSIZE"
}

if (/^X-Spam-Status: *Yes/:h)
{
  #Create SPAM IMAP folder if they don't have one
  `test -d $DEFAULT/.Spam`
  if( $RETURNCODE == 1 )
  {
    `/usr/bin/maildirmake -f Spam $DEFAULT`
    `echo INBOX.Spam >> $DEFAULT/courierimapsubscribed`
  }
  exception {
    to "$DEFAULT/.Spam/"
  }
}
  

In many case you might not be interested in keeping virus in quarantine as it may bother your users or spend useless data on your account. So I personaly replace : {#Create SPAM IMAP folder if they don't have one `test -d $DEFAULT/.Spam` if( $RETURNCODE == 1 ) { `/usr/bin/maildirmake -f Spam $DEFAULT` `echo INBOX.Spam >> $DEFAULT/courierimapsubscribed` } exception { to "$DEFAULT/.Spam/" }} by : { exit } This way, mail is trashed and only a log remain in the clamav log file that a virus has been found

Starting the system

This is fairly simple:

/etc/init.d/spamd start
/etc/init.d/clamd start
/etc/init.d/courier restart

Training SpamAssassin

Check Gentoo Linux Documentation -- Setting up an integrated local email delivery system for a good way to do this - the simple way