bugtraq - Re: Spammers can hide behind 'Email a friend/article' scripts.

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Date: Tue, 27 Apr 2004 08:15:20 +0200 (CEST)
From: matthias@...rum.ch
To: bugtraq@...urityfocus.com
Subject: Re: Spammers can hide behind 'Email a friend/article' scripts.

> # Description: Spammers can hide behind 'Email a friend/article' scripts.

These are just an instance of the more general form hijacking attacks. I've
seen several attempts to abuse feedback forms and similar through a simple
scheme - each form field was filled with

"To: <someaddr>\nFrom: <someaddr>\n"

Form scripts that do not check for newlines within the fields are vulnerable
to those attacks in general, for example in perl pseudocode:

open(SENDMAIL, "|/usr/sbin/sendmail -someflags")
     or print "Some Error: $!\n";
print SENDMAIL "From: $formfield_from\n";
print SENDMAIL "To: $recipient-taken-from-some-config\n";
print SENDMAIL "Subject: Foo Bar '$formfield_subject'\n";
print SENDMAIL "\nMail content\n";
close(SENDMAIL);

If $formfield_subject contains the above line with additional To:s, it
depends on the MTA whether he parses the additional headers and sends
them along.

Around end of march/beginning of april 2004 I've seen a number of attempts
to abuse such scripts. It look like a systematic approach and not some
random guesses.

-- Matthias

-- 
Matthias' Braindump http://matthias.leisi.net/