Re: [Ietf-dkim] Rechartering

["Murray S. Kucherawy" <[e-mail]>]

On Sun, Nov 27, 2022 at 6:50 PM Dave Crocker <[e-mail]> wrote:

> On 11/27/2022 6:30 PM, Murray S. Kucherawy wrote:
> > Domain Keys Identified Mail (DKIM, RFC 6376) defines a mechanism for
> > using a digital signature to associate a domain identity with an email
> > message in a secure way, and to assure receiving domains that the
> > message has
> > not been altered since the signature was created.  Receiving systems
>
> Again:  DKIM does not assure that the message has not been altered.  It
> assures only the covered portions of the message.
>
> That's not a small difference in data integrity protection.
>

OK, I'll add that in.


> > A DKIM-signed message can be re-posted, to a different set of
> > recipients, without
> > disturbing the signature's validity.  This can be used to confound the
> > engines that
> > identify abusive content.  RFC 6376 identified a risk of these
> > "replay" attacks, but
> > at the time did not consider this to be a problem in need of a
> > solution.  Recently,
> > the community has decided that it has become enough of a problem to
> > warrant being revisited.
>
> This does not provide any real understanding of how replay is
> accomplished.  And since it's easy to explain and doesn't take much
> text, I'll again encourage including that in the document that defines
> the nature of the problem we will be working on, namely the charter.
>

Doesn't the "A DKIM-signed message can be re-posted, ..." sentence do
that?  I pulled it from your suggested text for that very reason.  Maybe
add something to the second sentence making clear the roles in the attack?


> > The DKIM working group will produce one or more technical
> > specifications that
> > describe the abuse and propose replay-resistant mechanisms that are
> > compatible
> > with DKIM's broad deployment.  The working group may produce documents
> > describing
> > relevant experimental trials first.
>
> This draft doesn't include the 'preservation of installed base' cover
> text that Barry's had and I forgot to include in mine.  I think it's
> important.
>

I had intended "compatible with DKIM's broad deployment" to cover exactly
this.  Should I word it differently?

-MSK