Re: Last Call: <draft-ietf-lamps-eai-addresses-05.txt> (Internationalized Email Addresses in X.509 certificates) to Proposed Standard

Viktor Dukhovni <ietf-dane@dukhovni.org> Fri, 03 February 2017 19:51 UTC

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Subject: Re: Last Call: <draft-ietf-lamps-eai-addresses-05.txt> (Internationalized Email Addresses in X.509 certificates) to Proposed Standard
From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Date: Fri, 3 Feb 2017 14:51:24 -0500
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> On Feb 3, 2017, at 2:38 PM, Wei Chuang <weihaw@google.com> wrote:
> 
> Can you clarify what this means for addresses such as:
> 
>         U: ietf-dane@духовный.org
> 
> Not recommended but supported by SmtpUtf8Name.
>  
> 
>         A: ietf-dane@xn--b1adqpd3ao5c.org
> 
> Use rfc822Name.  This is recommended.

So, to be clear, for the same domain, some addresses will be
represented as rfc822Name SAN elements (with the domain in
A-label form), and other addresses (those with non-ASCII
localparts) will be represented as SmtpUtf8Name SAN elements
(with the domain in U-label form).

A verifier checking for an address with a non-ASCII localpart
will compare against SmtpUtf8Name elements with U-label domain
encodings, while a verifier checking for an address with an all
ASCII localpart will check against rfc822Name elements using an
A-label domain encoding (of the same domain).

Is that right?  Thus the verifier would sometimes need to convert
from U-labels to A-labels (when the localpart is all ASCII), and
at other times from A-labels to U-labels (when the localpart is not
all ASCII)...

-- 
	Viktor.