How To Log Emails Sent With PHP's mail() Function To Detect Form Spam
Version 1.0
Author: Till Brehm <t [dot] brehm [at] ispconfig [dot] com>
If you are running a webserver you might have faced the problem already: somewhere on your server is a vulnerable contact form or CMS system written in PHP that gets abused by spammers to send emails trough your server. If you have more than a few websites, it is a pain to detect which of the sites is vulnerable and sends the spam emails. This tutorial explains the installation of a small wrapper script which logs email messages sent trough the PHP mail() function.
I'm using Debian Linux here for this tutorial but the script should work on any Linux distribution.
1 Installing the wrapper script
Open a new file /usr/local/bin/phpsendmail...
vi /usr/local/bin/phpsendmail
... and insert the following script code:
#!/usr/bin/php
<?php
/**
This script is a sendmail wrapper for php to log calls of the php mail() function.
Author: Till Brehm, www.ispconfig.org
(Hopefully) secured by David Goodwin <david @ _palepurple_.co.uk>
*/
$sendmail_bin = '/usr/sbin/sendmail';
$logfile = '/tmp/mail_php.log';
//* Get the email content
$logline = '';
$pointer = fopen('php://stdin', 'r');
while ($line = fgets($pointer)) {
if(preg_match('/^to:/i', $line) || preg_match('/^from:/i', $line)) {
$logline .= trim($line).' ';
}
$mail .= $line;
}
//* compose the sendmail command
$command = 'echo ' . escapeshellarg($mail) . ' | '.$sendmail_bin.' -t -i';
for ($i = 1; $i < $_SERVER['argc']; $i++) {
$command .= escapeshellarg($_SERVER['argv'][$i]).' ';
}
//* Write the log
file_put_contents($logfile, date('Y-m-d H:i:s') . ' ' . $_ENV['PWD'] . ' ' . $logline, FILE_APPEND);
//* Execute the command
return shell_exec($command);
?>
If you use a different Linux distribution than Debian, the sendmail binary might be in a different location than /usr/sbin/sendmail and you have to change the sendmail path in the line $sendmail_bin = '/usr/sbin/sendmail'; of the script.
Now make the script executable...
chmod +x /usr/local/bin/phpsendmail
... and create the logfile and make it writable:
touch /var/log/mail.form
chmod 777 /var/log/mail.form
2 Modifying the php.ini
Now we reconfigure PHP so that it uses our wrapper script to send the emails.
Open the php.ini file...
vi /etc/php5/apache2/php.ini
... and change the lines...
[mail function] ; For Win32 only. SMTP = localhost smtp_port = 25 ; For Win32 only. ;sendmail_from = [email protected] ; For Unix only. You may supply arguments as well (default: "sendmail -t -i"). ;sendmail_path =
... to:
[mail function] ; For Win32 only. ;SMTP = localhost ;smtp_port = 25 ; For Win32 only. ;sendmail_from = [email protected] ; For Unix only. You may supply arguments as well (default: "sendmail -t -i"). sendmail_path = /usr/local/bin/phpsendmail
If you use php as cgi, with suphp or as fcgi, then change the same lines in the file /etc/php5/cgi/php.ini, too.
Restart the Apache webserver to apply the changes.
/etc/init.d/apache2 restart
3 Test the setup
To test this setup, create a new php file with the name mailtest.php in one of your websites with the content:
<?php
mail('[email protected]','This is a test message subject','This is a test message body');
echo 'Mail sent.';
?>
Then open the file in a webbrowser to execute it. The test message should be logged now into the logfile. Check this with the command:
cat /var/log/mail.form
