Re: [apps-discuss] Review of: draft-ietf-appsawg-malformed-mail-03

"Murray S. Kucherawy" <superuser@gmail.com> Wed, 29 May 2013 07:05 UTC

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Date: Wed, 29 May 2013 00:05:54 -0700
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From: "Murray S. Kucherawy" <superuser@gmail.com>
To: Ned Freed <ned.freed@mrochek.com>
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Cc: John R Levine <johnl@taugh.com>, IETF Apps Discuss <apps-discuss@ietf.org>
Subject: Re: [apps-discuss] Review of: draft-ietf-appsawg-malformed-mail-03
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On Tue, May 28, 2013 at 5:50 PM, Ned Freed <ned.freed@mrochek.com> wrote:

> > Consider a system that has several independent filtering modules.  It's
> > important that the modules don't change the content as it passes from one
> > to the next as doing so might obscure something that the next module
> might
> > consider reject-worthy.  Therefore, whatever transformations need to be
> > done have to be kept internal to the module and not released as the
> "real"
> > content.
>
> It's nowhere near this simple. Sometimes you want filtering modules exposed
> to unadulterated content. One way to arrange for that is preclude any
> changes, but another is to run the modules in parallel. After all, if
> they're
> not talking to each other, why wouldn't you want them to run
> simultaneously?
>
> But other times you want them to be able to pass information to each other.
> Unfortunately that often can only be done by adding headers. And there are
> even times when you want much more radical transformations applies, such
> as the removal of encryption, forced conversion to MIME format, etc. etc.
>
> There really isn't a one size fits all answer here, and it's silly to think
> one can be found.
>

The -05 version of this document makes it clear that we're talking about a
system where the handling modules operate in a sequence, since that's the
model I had in mind when I rewrote that text.  I'll add some additional
prose about the points you've made here.

-MSK