Re: Last Call: <draft-ietf-lamps-eai-addresses-05.txt> (Internationalize

On Thu, Feb 16, 2017 at 10:26 AM, Viktor Dukhovni 
<ietf-dane(_at_)dukhovni(_dot_)org>
wrote:

> > On Feb 16, 2017, at 10:30 AM, Wei Chuang <weihaw(_at_)google(_dot_)com> 
> > wrote:
> >
> > > How about if a CA with only rfc822Name constraints can't issue certs
> > > with SmtpUTF8Names at all, and of course vice versa.  If you want both
> > > kinds of names, the CA has to constrain both.
> > I had asked a few folks at Google for an opinion about the name
> constraints.
> > Let me post Ryan Sleevi's (CC'ed) opinion:
> >
> > https://mailarchive.ietf.org/arch/msg/ietf/ngUOjvCHubjcyiG4uZ0w16-5-fg
> > [the above] basically says option 3 [the acceptable approach of the 3],
> > but unfortunately suffers from 'legacy' - namely, you cannot assume that
> > all rfc822Name clients will be updated to support SmtpUtf8Name, and short
> > of marking it critical (which would mean its undeployable), you can't
> > assume that an SmtpUtf8Name nameConstraint will constrain an rfc822Name.
> Given that rfc822Name is a well-known legacy element, while SmtpUtf8Name
> is a novel element, the prescription can be asymmetric.  Specifically,
> all that's really needed (in the simpler model proposed by John) is
> to disallow SmtpUtf8Name altnames when (only) rfc822Name constraints
> are present.
>
> The converse is not required, a parent CA that is SmtpUtf8Name aware
> and wants to issue a child CA with SmtpUtf8Name constraints can and
> should also include appropriate rfc822Name constraints that ensure
> that the desired SmtpUtf8Name constraints are not bypassed via
> unauthorized rfc822Name altnames.
>
> The rfc822Name constraints can either permit only equivalent domain
> names (LDH or A-label forms), or, if no rfc822Name can be compatible
> with the SmtpUtf8Name constraints, permit only something like
> "nouser@nodomain.invalid", thereby excluding all valid rfc822 addresses.
>
> --
>         Viktor.
Hi Viktor and everyone else on the thread,

Apologies about being pedantic.  If we specify the CA name constraints as
you describe above with the asymmetric requirements on SmtpUtf8Name, are
you okay with the draft's position on keeping separate name constraint
processing for rfc822Name and SmtpUtf8Name types?  In other words the above
is proposed to be the resolution for the issue raised in your email Feb
11th, second email, para 1-3 i.e. preventing evasion of name constraints.

thanks,
-Wei

smime.p7s
Description: S/MIME Cryptographic Signature