Postfix Randomizing Outgoing IP Using TCP_TABLE And Perl

This time i’ll show you how to randomize your smtp outbound’s IP addresses. This can be done via transport map. But, since ordinary Postfix lookup tables store information as (key, value) pairs. it will provide static value only. we need someting that can manipulate the value (right hand side) of a lookup table. In order to answer random transport value.

first come to mind was tcp_tables, tcp_tables lookup table gives some flexibility for us to execute our tiny perl script that will randomizing transport. that’s the basic idea.

Ok, here’s the first part, create perl script call random.pl, anyway this script only provide answer in “catch-all” manner. so it will randomized, all outgoing mail.

# cd /etc/postfix
# vi random.pl

#!/usr/bin/perl -w
# author: Hari Hendaryanto <hari.h -at- csmcom.com>

use strict;
use warnings;
use Sys::Syslog qw(:DEFAULT setlogsock);

#
# our transports array, we will define this in master.cf as transport services
#

our @array = (
'rotate1:',
'rotate2:',
'rotate3:',
'rotate4:',
'rotate5:'
);

#
# Initalize and open syslog.
#
openlog('postfix/randomizer','pid','mail');

#
# Autoflush standard output.
#
select STDOUT; $|++;

while (<>) {
        chomp;
        # randomizing transports array
        my $random_smtp = int(rand(scalar(@array)));
        if (/^get\s(.+)$/i) {
                print "200 $array[$random_smtp]\n";
                syslog("info","Using: %s Transport Service", $random_smtp);
                next;
        }

	print "200 smtp:";
}

Make it executable

# chmod 755 random.pl

master.cf parts

Run the scripts via postfix spawn daemon service.

127.0.0.1:2527 inet  n       n       n       -       0      spawn
          user=nobody argv=/etc/postfix/random.pl

add 5 smtp client services called rotate1, rotate2, rotate3, rotate4, rotate5, that bind to its own ip
address and has uniq syslog/helo name.

# random smtp
rotate1  unix -       -       n       -       -       smtp
          -o syslog_name=postfix-rotate1
          -o smtp_helo_name=smtp1.example.com
          -o smtp_bind_address=1.2.3.1

rotate2  unix -       -       n       -       -       smtp
          -o syslog_name=postfix-rotate2
          -o smtp_helo_name=smtp2.example.com
          -o smtp_bind_address=1.2.3.2

rotate3  unix -       -       n       -       -       smtp
          -o syslog_name=postfix-rotate3
          -o smtp_helo_name=smtp3.example.com
          -o smtp_bind_address=1.2.3.3

rotate4  unix -       -       n       -       -       smtp
          -o syslog_name=postfix-rotate4
          -o smtp_helo_name=smtp4.example.com
          -o smtp_bind_address=1.2.3.4

rotate5  unix -       -       n       -       -       smtp
          -o syslog_name=postfix-rotate5
          -o smtp_helo_name=smtp5.example.com
          -o smtp_bind_address=1.2.3.5

Before we actually implement our randomize transport, let’s make sure that the setting actually work.

Reload postfix

# postfix reload

Run this query fiew times, and you’ll see the perl script will return “random answer” transport

# postmap -q "whatever" tcp:127.0.0.1:2527
rotate1:

# postmap -q "whatever" tcp:127.0.0.1:2527
rotate5:

And so on..

Note on “whatever”, since the script acted in “catch-all” mode as i’ve mentioned earlier, what ever postfix transport_maps client asked. it will be answered with random values such as rotate1, rotate2, rotate3, rotate4, rotate5 in randomized fashion.

main.cf parts

Add these lines

transport_maps = tcp:[127.0.0.1]:2527
127.0.0.1:2527_time_limit = 3600s

Reload postfix
that’s it. example log would be like these and that’s indicate that randomizer is working.

Month date 12:26:53 host postfix-rotate1/smtp[4252]: A1CA68480A4: to=<xxx@example.com>, relay=mx.example.com.com[xx.xx.xxx.xx]:25], delay=3.6, delays=0.69/0.01/0.81/2, dsn=2.0.0, status=sent (250 ok dirdel)
--snip--
Month date 12:27:06 host postfix-rotate5/smtp[4253]: 41C2E8480A4: to=<xxx@example.net>, relay=mx.example.net[xx.xxx.xxx.xxx]:25], delay=6, delays=0.14/0.01/0.85/5, dsn=2.0.0, status=sent (250 ok dirdel)
--snip--
Month date 12:27:22 host postfix-rotate3/smtp[4277]: 4BA9F8480A4: to=<xxx@example.org>, relay=mx.example.org[xx.xxx.xx.xxx]:25], delay=7.9, delays=0.85/0.02/0.61/6.4, dsn=2.0.0, status=sent (250 ok dirdel)

disclaimer:
I’m not taking any responsible if the reader “misuse” this tutorial.the tutorial is provide as-is for experimental purposes.

You may also want to read these posts:

• Postfix Rotating Outgoing IP Using TCP_TABLE And Perl
• Postfix Changing Outgoing IP By Time Interval Using TCP_TABLE And Perl
• Postfix Bind Sender Outgoing IP, Based On GeoIP Location
• Postfix Bind Sender Domain To Dedicated Outgoing IP Address
• postfix, integrating memcache as a lookup table using tcp_table
• Postfix Create Blackhole For Authenticated User’s Outgoing Submission (revised)
• Postfix smtp outgoing load balancing
• Measure Response Time Of SMTP Connections Using Perl
• Postfix Smtp Outgoing IP Rotator using iptables
• Postfix GeoIP Based Rejections