From: Hugh Sasse Staff Elec Eng <hgs@...>
Date: 2003-08-26T19:04:09+09:00
Subject: Re: Email and smtp.sendmail security vulnerabilities?

On Tue, 26 Aug 2003, John W. Long wrote:

> Hi,
>
> I've created a small class and supporting methods for sending email from a
> web page. I use it like this:
>
>     msg = Web::Email::Message.new(
>      :from => from,
>      :to => to,
>      :subject => subject,
>      :body => body.untaint # security vulnerability?
>     )
>     Web::Email.send(msg)
>
> All of the email strings (:from, :to, etc...) could potentially come from
> the the outside world. I'm doing some munging on the :from, :to, and

That is your security problem in itself.  Far better would be to
permit certain addresses only, and let the user choose them by
passing a hash (such as MD5) of the desired address into the form.
Thus different addresses cannot easily be created, because only
those selected addresses will be reverse mapped (md5->address).
This selection would obviously have to be done from a radio button
or similar selector.

Why go to all this trouble?  See
http://spamcop.net/fom-serve/cache/270.html
for links to details about formmail which used to be open.
Basically, anyone could use your script for relaying mail via your
machine...

        Hugh