On Thu, May 10, 2018 at 12:38 AM Benjamin Kaduk <[email protected]> wrote:

> On Wed, May 09, 2018 at 11:43:50AM -0700, Ned Freed wrote:
> > > Benjamin Kaduk has entered the following ballot position for
> > > draft-ietf-uta-mta-sts-17: No Objection
> >
> > > When responding, please keep the subject line intact and reply to all
> > > email addresses included in the To and CC lines. (Feel free to cut this
> > > introductory paragraph, however.)
> >
> >
> > > Please refer to
> https://www.ietf.org/iesg/statement/discuss-criteria.html
> > > for more information about IESG DISCUSS and COMMENT positions.
> >
> >
> > > The document, along with other ballot positions, can be found here:
> > > https://datatracker.ietf.org/doc/draft-ietf-uta-mta-sts/
> >
> >
> >
> > > ----------------------------------------------------------------------
> > > COMMENT:
> > > ----------------------------------------------------------------------
> >
> > > Thanks for the well-written document!  Other people have noted some
> things already,
> > > so I can only add small things.
> >
> > > Section 3.1
> >
> > > Did you consider ABNF that would let new versions be defined without
> > > having to redefine the ABNF?
> >
> > First, since the cost of "redefinition" is a single line of ABNF:
> [...]
>
> ("Yes" would have sufficed.)
>
> > > Section 7.2
> >
> > > It's probably better to cite this as BCP 195 than RFC 7525 directly.
> >
> > Given the liklihood of BCP 195 being upgraded to TLS 1.3 at some point
> without
> > full consideration of the impace on email infrastructure,  I'm by no
> means sure
> > that's the case.
> >
> > Or, to put this another way, if you want to reference a changing set of
> secure
> > substrate best practices here, that in turn imposes a requirement on
> future
> > versions of those best practices to give full consideration to email
> > infrastructure realities.
> >
> > As the wise man once said, "Are you sure this is what you want?"
>
> It seems rather inherent that when one is using the phrase
> "infrastructure realities" in this sort of context, it will be in
> conflict with "best current practice", because if there was no
> conflict, it wouldn't be worth talking about.  So if this is simply
> a matter of giving a more direct pointer to the conflict between
> deployed reality and (ideal) best practices, yes, I'm fine with
> that.
>
> I also expect that a hypothetical rev of BCP 195 to include TLS 1.3
> will take into account all consumers of TLS, and not limit itself to
> just the Web ecosystem, since TLS is a general-purpose protocol.
>
> > > Section 8.1
> >
> > >    Recipients should also prefer to update the HTTPS policy body before
> > >    updating the TXT record; this ordering avoids the risk that senders,
> > >    seeing a new TXT record, mistakenly cache the old policy from HTTPS.
> >
> > > It seems like this risk would be mitigated if the "id" value from
> > > the TXT record was required to also appear in the policy body as an
> > > identifier.  But presumably that would cause issues elsewhere, as it
> > > is not the case in the current document.
> >
> > The problem with including the id in the policy is that now you have a
> gap
> > no matter how you order the update.
>
> Right.
>

Yes, but an alternate approach is to have the "id" in the TXT become a part
of the policy URI--e.g.

..well-known/mta-sts-$id.txt

We chose not to do this because it seemed like greater complexity with
little benefit; in general, it's not hard advice to tell people to publish
the policy body first, and fixed paths seem a bit more coherent to me. But
I thought I'd call that out for interest's sake.


>
> -Benjamin
>
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