From: Richard Turner <richard.turner@...>
Date: 2005-04-06T22:22:13+09:00
Subject: Re: Net::SMTP/mod_ruby SecurityError

On Wed, 2005-04-06 at 20:21 +0900, Richard Turner wrote:
> Hi,
> 
> I have an application that uses mod_ruby and I need to be able to have
> it email a message to an address specified by a user using a web form. I
> seem to have everything set-up fine, I run the entered email address
> through a validation process before continuing so I'm confident it's
> safe to untaint it, but sendmessage() still raises a SecurityError.
> 

Apologies for replying to myself :)

Unless I'm very much mistaken I've tracked the problem to the
send_message() method in smtp.rb. This method calls Array#flatten on its
to_addrs parameter which, it seems, causes any elements in that array
that had been explicitly untainted to become tainted again. Later, in
send0(), a SecurityError is then thrown (if $SAFE > 0) regardless of any
programmer's steps to untaint email addresses.

So, my question becomes, is there a way for me to untaint a validated
email address and ensure that it stays untainted even when the array
it's in is flattened by Net::SMTP.send_message?

In the meantime I've hacked my version of smtp.rb to recursively check
all the elements of the to_addrs array to ensure that they're not
tainted and only proceed if that's the case. Then I can flatten the
array and merrily untaint all its elements again in case flatten()
caused them to become tainted.

Cheers,

Richard.