Re: [Spasm] Last Call: <draft-ietf-lamps-eai-addresses-05.txt> (Internat

The latest draft 08 is up:
https://tools.ietf.org/html/draft-ietf-lamps-eai-addresses-08

The diff is:
https://tools.ietf.org/rfcdiff?url2=draft-ietf-lamps-eai-addresses-08.txt

This draft attempts to capture Viktor's name constraint verifier logic, and
illustrate the examples in the diagrams.

-Wei


On Thu, Mar 9, 2017 at 10:22 AM, Wei Chuang <weihaw(_at_)google(_dot_)com> 
wrote:

> There seems to be a consensus here and internally to the changes that
> Viktor proposes.  We can put that in the next draft update.
>
> -Wei
>
> On Thu, Mar 9, 2017 at 1:34 AM, tom p. <daedulus(_at_)btconnect(_dot_)com> 
> wrote:
>
> > ----- Original Message -----
> > From: "Viktor Dukhovni" <ietf-dane(_at_)dukhovni(_dot_)org>
> > To: <spasm(_at_)ietf(_dot_)org>; "IETF general list" 
> > <ietf(_at_)ietf(_dot_)org>
> > Sent: Thursday, March 09, 2017 3:19 AM
> > > On Mar 8, 2017, at 8:17 PM, Wei Chuang <weihaw(_at_)google(_dot_)com> 
> > > wrote:
> > >
> > > Okay.  I think the direction then is to have SmtpUTF8Name respect
> > rfc822Name name constraints and vice versa.
> >
> > Well, no, the simplest proposal on the table is for SmtpUTF8Name to
> > be *prohibited* when rfc822Name constraints are present and SmtpUTF8Name
> > constraints are not.  When both present, they can operate independently.
> >
> > <tp>
> >
> > Getting security right can be tricky as the legion of failed attempts
> > that make it to RFC testify but what you are proposing here seems so
> > simple, so obviously the right thing to do that I am puzzled, bewildered
> > even, that anyone can disagree with you.
> >
> > Tom Petch
> >
> > The verifier logic is then:
> >
> > 1. If neither rfc822Name constraints nor SmtpUTF8Name constraints
> >            are present in any CA certificate in the chain, any mixture
> > of
> >            rfc822Name and SmtpUTF8Name SAN elements is valid.
> >
> > 2. If some certificate in the chain contains *only* rfc822Name
> >    constraints, then these apply to rfc822Name SAN elements, but
> >    all SmtpUTF8Names are prohibited.
> >
> > 3. When both types of constraints are present in all CA certificates
> >            that have either type, then constraints for each SAN type are
> >    exclusively based on just the corresponding constraint type.
> >
> > 4. If some certificate in the chain contains only SmtpUTF8Name
> >      constraints then those are unavoidably at risk of bypass via
> >            rfc822Name SAN elements when processed by legacy verifiers.
> >    Therefore, this should be avoided, and the CA needs to
> >      publish rfc822Name constraints that prevent bypass.  Such
> >    constraints *need not* be equivalent (not always possible)
> >    to the desired SmtpUTF8Name constraints.  Rather, it suffices
> >    to not permit rfc822Name elements that would be prohibited
> >    if they were simply cut/pasted (with no A-label to U-label
> >            conversions) as SmtpUTF8Name elements.  It is not necessary
> >    for these to permit everything that SmtpUTF8Name permits.
> >
> > Thus for example, if SmtpUtf8Name only permits addresses in the non
> > NR-LDH
> > domain "духовный.org <http://xn--b1adqpd3ao5c.org>" (or a specific set
> > of addresses in such a domain),
> > then the corresponding rfc822Name constraint could just permit "." (or
> > the
> > reserved "invalid" TLD if that's preferable) which is not a usable email
> > domain.  This ensures that only the permitted SmtpUTF8Name SANs are used
> > and no rfc822Name SANs are used.
> >
> > If, instead the Smtp8Name constraints are excluded non-ASCII address
> > forms,
> > then since these have no literal rfc822Name equivalents, the rfc822Name
> > constraints can be omitted with the same effect.
> >
> > Only when the intention is to permit NR-LDH domains with either ASCII or
> > UTF-8 localparts (or an all-ASCII full address) do the rfc822Name and
> > SmtpUTF8Name constraints need to be fully equivalent.  This is of course
> > trivial to do.  Just cut/paste the same string into both types of
> > constraint.
> >
> > --
> > Viktor.

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