Extensive sendmail wrapper with sender throttling

In this tutorial I’d like to describe how to create an extensive sendmail wrapper for a web server to monitor all sent emails and throttle daily sent email volume by the senders original UID (user id). This is useful if you e.g. run PHP in CGI-mode with SuExec, that is: all customers run their scripts under their own UID. The wrapper described here is not just a PHP-only wrapper (as described in my Simple PHP mail wrapper tutorial) – it directly replaces /usr/sbin/sendmail so we are able track all sent email of the whole system.

requirements:

Perl
Perl DBI (Perl Database Interface)
MySQL

On a Debian/Ubuntu system, make sure you have the the following packages installed:


apt-get install libdbd-mysql-perl libdbi-perl libmailtools-perl

apt-get install libdbd-mysql-perl libdbi-perl libmailtools-perl

Now create the database sendmailwrapper and the one and only needed table throlltle in MySQL:


CREATE DATABASE IF NOT EXISTS sendmailwrapper;
GRANT ALL ON sendmailwrapper.* TO smwrapper@localhost IDENTIFIED BY 'yourPassword';
FLUSH PRIVILEGES;

USE sendmailwrapper;

CREATE TABLE `throttle` (
  `id` INT NOT NULL auto_increment,
  `orig_uid` int(10) unsigned NOT NULL default '0',
  `count_max` mediumint(8) unsigned NOT NULL default '1000',
  `count_cur` mediumint(8) unsigned NOT NULL default '1',
  `last_request` datetime NOT NULL default '1970-01-01 00:00:00',
  `reported` BOOL NOT NULL default '0',
  UNIQUE KEY `orig_uid` (`orig_uid`),
  PRIMARY KEY (`id`)
) TYPE=InnoDB;

CREATE DATABASE IF NOT EXISTS sendmailwrapper;

GRANT ALL ON sendmailwrapper.* TO smwrapper@localhost IDENTIFIED BY 'yourPassword';

FLUSH PRIVILEGES;

USE sendmailwrapper;

CREATE TABLE `throttle` (

`id` INT NOT NULL auto_increment,

`orig_uid` int(10) unsigned NOT NULL default '0',

`count_max` mediumint(8) unsigned NOT NULL default '1000',

`count_cur` mediumint(8) unsigned NOT NULL default '1',

`last_request` datetime NOT NULL default '1970-01-01 00:00:00',

`reported` BOOL NOT NULL default '0',

UNIQUE KEY `orig_uid` (`orig_uid`),

PRIMARY KEY (`id`)

) TYPE=InnoDB;

Let’s now move the original /usr/sbin/sendmail and replace it with our wrapper script (download below and put it into e.g. /opt/sendmail-wrapper/). Make sure, we got a logfile where all web-users are allowed to write to and only root can read from:


if test ! -s /usr/sbin/sendmail.orig
then
    # create logfile
    mkdir /var/www/log
    chmod 777 /var/www/log
    touch /var/www/log/sendmail-wrapper.log
    chmod 622 /var/www/log/sendmail-wrapper.log
    # install wrapper script
    mv /usr/sbin/sendmail /usr/sbin/sendmail.orig
    ln -sf /opt/sendmail-wrapper/sendmail-wrapper.pl /usr/sbin/sendmail
    echo 'Installed sendmail-wrapper!'
fi

if test ! -s /usr/sbin/sendmail.orig

then

# create logfile

mkdir /var/www/log

chmod 777 /var/www/log

touch /var/www/log/sendmail-wrapper.log

chmod 622 /var/www/log/sendmail-wrapper.log

# install wrapper script

mv /usr/sbin/sendmail /usr/sbin/sendmail.orig

ln -sf /opt/sendmail-wrapper/sendmail-wrapper.pl /usr/sbin/sendmail

echo 'Installed sendmail-wrapper!'

Install the following cronjobs for daily cleanup and reporting (download cleanup.pl and report.pl below and put them into /opt/sendmail-wrapper/):


# Sendmail-wrapper
05 5    * * *   root    /opt/sendmail-wrapper/cleanup.pl
01 *    * * *   root    /opt/sendmail-wrapper/report.pl

# Sendmail-wrapper

05 5 * * * root /opt/sendmail-wrapper/cleanup.pl

01 * * * * root /opt/sendmail-wrapper/report.pl

The script now throttles sent email to a limit of 1000/day and prints log output to /var/www/log/sendmail-wrapper.log, e.g.:


[Sat, 03 Jan 2009 14:58:15 +0100] 83.77.98.62 ran /test.php at www.onlime.ch (OK)
[Sat, 03 Jan 2009 14:58:21 +0100] 83.77.98.62 ran /send.php at www.iezzi.ch (OK)

[Sat, 03 Jan 2009 14:58:15 +0100] 83.77.98.62 ran /test.php at www.onlime.ch (OK)

[Sat, 03 Jan 2009 14:58:21 +0100] 83.77.98.62 ran /send.php at www.iezzi.ch (OK)

This has been tested on a Debian Etch system running Perl 5.8.8 / MySQL 5.0.32 / exim4 (4.63). It works as well with Postfix but there are known problems with mailq and similar commands that pass parameters to /usr/sbin/sendmail.

Download needed wrapper files and don’t forget to configure them properly (CONFIGURATION section):

sendmail-wrapper.pl
cleanup.pl
report.pl
sendmail-wrapper.sql (used for database setup)

6 Responses

Boris
Jul 08, 2009 - 01:26 PM

Hi,

i have a Problem with it, if i install all described here, i start a mail.php

and the wrapper starts to loop and try to send the message initiated from the php script till its maximum throttle count.

So it looks like.
If i have a look to top, i see that the scripts starts 100 sendmail processes, but dosnt send anything.

If i disable logging, it starts only 1 process, but no message was sent.

Can you help ?

Best regards

Boris
Boris
Jul 08, 2009 - 01:34 PM

Problem fixed 🙂
have inside the script the path to sendmail directed to sendmail. Simply a Bad idea 😉 Pointed to sendmail.orig and now it runs. Thanks

Boris
Andreas
Feb 04, 2011 - 08:52 PM

You should update your installer script. If you are running with Postfix this may destroy the newaliases tool. Just relink it to the orig sendmail:
rm /usr/bin/newaliases; ln -s /usr/sbin/sendmail.orig /usr/bin/newaliases
This could avoid unusual side effects.
Cheers.
claudio
Nov 29, 2013 - 09:40 AM

Hi,
After the installation on my Server Debian 6.0.7 with Plesk 11.5.30 an Roundcube 0.8.6, Roundcube is not working anymore…
It pops up with an error: An error occured, sending of message failed..
Do you have a idea why.. or did anybody had the same problem..
thanks for help