Re: Re: Possible hacker using php script to send e-mails?

Manuel Lemos wrote:

Hello, on 03/11/2006 09:39 AM Merlin said the following:

I am running php 4.x on a suse 9.x machine. There is a php script which resides on a webapp that is responsible for sending e-mail to myself in case of errors like db-errors or similar. Called error.php This script does include phpmailer and uses it to send the e-mails to me. Now I am receiving on the e-mail specified as TO: e-mails with different subject than specified and different text?! All english text with wired sentences, must be a bot or so. How is this possible? The subject line is fixed and right after that commend send is executed. So no idea how they do it and how I can prevent it. It looks like this: $mail->Subject = 'Fehlerbericht'; $mail->Send(); How is it possible that they change this subject line? I checked the server log and each time an e-mail has been sent to me of that kind there is a logentry in apache log that says that this script has been executed. So the e-mails definatelly come from that script?!

If you are setting message headers with untrusted values that may contain line breaks, that is your problem. Line breaks make mail systems interpret the next line as a new header. That header may be used to inject new recipients for instance using Bcc: . You can have line breaks in header but you need to escape them properly so they are interpreted as continuation lines rather than new headers.

That is only true for the additional_headers (4th) argument to the mail function. That argument is specifically for doing free-form headers, so as long as you only use the to, subject and message arguments to the mail function you are safe. -Rasmus