TECH:postfix mail server: filter email by php script

Howto: create simple scrip using PHP to filter incoming email on POSTFIX MAIL SERVER

read article :  http://www.postfix.org/FILTER_README.html ("Simple content filter example")

* for the sample we use /etc/postfix to save the script files.

Step 1: create script file  "/etc/postfix/content-filter.sh"

#!/bin/sh

# Localize these. The -G option does nothing before Postfix 2.3.

INSPECT_DIR=/var/spool/filter
SENDMAIL="/usr/sbin/sendmail -G -i" # NEVER NEVER NEVER use "-t" here.

# Exit codes from <sysexits.h>
EX_TEMPFAIL=75
EX_UNAVAILABLE=69

# Clean up when done or when aborting.
trap "rm -f in.$$" 0 1 2 3 15

# Start processing.
cd $INSPECT_DIR || {
 echo $INSPECT_DIR does not exist; exit $EX_TEMPFAIL; }

cat >in.$$ || { 
 echo Cannot save mail to file; exit $EX_TEMPFAIL; }

/./etc/postfix/mail-cleaner.php in.$$
$SENDMAIL "$@" <in.$$

exit $?

Step 2: create php content filter file "/etc/postfix/mail-cleaner.php"

#!/usr/bin/php
<?php
//read mail file.
$file=$argv[1];
$data=file_get_contents($file);

$mail_parts=explode("\n\n",$data);
//Get header
$header=$mail_parts[0];

//Get all mail parts.
$mail_parts[0]="";
$content=implode($mail_parts,"\n\n");

//Remove all email address from  mail content
$content=preg_replace("/[^\s]*@[^@\s]*\.[^@\s]*/", "***@***.***", $content);

//Remove all websites from mail contant
$content=preg_replace("/[a-zA-Z]*[:\/\/]*[A-Za-z0-9\-_]+\.+[A-Za-z0-9\.\/%&=\?\-_]+\.+/i", "www.***.***", $content);

//Save the new email.
file_put_contents($file,$header."\n\n".$content);
?>

Step 3: add configuration to "/etc/postfix/master.cf"

add the following lines to "master.cf"

filter    unix  -       n       n       -       10      pipe
    flags=Rq user=filter null_sender=
    argv=/etc/postfix/content-filter.sh -f ${sender} -- ${recipient}

add option "-o content_filter=filter:dummy" to smtp service 

smtp      inet  n       -       -       -       -       smtpd
 -o content_filter=filter:dummy

Step 4: Create user "filter" and add premissions 
simple run commands :

# (for centOS 6) create new user without home directory
useradd -M filter 

#add execute permissions to script files
chmod +rx /etc/postfix/content-filter.sh   
chmod +rx /etc/postfix/mail-cleaner.php

#create directory filter
mkdir /var/spool/filter

#change owner and group to filter
chown filter /var/spool/filter
chgrp filter /var/spool/filter

Step 5: (*) Disable SELinux security
to running the scripts we must to trun off the selinux security
http://www.crypt.gen.nz/selinux/disable_selinux.html

change the in file "/etc/selinux/config"

from :

SELINUX=enforcing

to:
SELINUX=disabled

Step 6: Reboot.

enjoy!

Attention :
(*) if you don't disable the  SELinux you will see in the maillog file ("/var/log/maillog")
the errors:
Sep 9 18:50:22 localhost postfix/pipe[2960]: 9F2349ABB01: to=<em...@domain.com>, relay=postfixfilter, delay=7441, delays=7441/0.08/0/0.65, dsn=4.3.0, status=deferred (temporary failure. Command output: pipe: fatal: pipe_command: execvp /etc/postfix/content-filter.sh: Permission denied )