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[ + [email protected] ]

On 2/18/13 11:04 AM, Chris Newman wrote:
> --On February 14, 2013 14:24:17 -0700 Peter Saint-Andre 
> <[email protected]> wrote:
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>> 
>> On 2/14/13 2:12 PM, Peter Saint-Andre wrote:
>>> Hi Chris, thank you for the review.
>>> 
>>> On 2/14/13 12:37 PM, Chris Newman wrote:
>>>> A common construction for user names on the Internet is the
>>>> form "[email protected]", specifically, a subset of
>>>> email-address syntax with an embedded domain name is commonly
>>>> used for login identity strings (although theses login
>>>> identity strings may or may not be usable as actual email
>>>> addresses).
>>> 
>>>> As a result, the character class used for user names used
>>>> for authentication needs to be a superset of the character
>>>> class used for domain names. I was not able to tell from the 
>>>> specification if that was the case. If it isn't, I believe
>>>> that should be fixed.
>>> 
>>> It is the case, because all characters in the ASCII range are 
>>> grandfathered into the PRECIS NameClass. Thus some examples
>>> are definitely in order! We'll add those to the next version.
>> 
>> I propose adding the second paragraph shown below to the end of 
>> Section 2.1, which defines the handling of simple user names:
>> 
>> Note well that all code points and blocks not explicitly allowed
>> in the PRECIS NameClass are disallowed; this includes private
>> use characters, surrogate code points, and the other code points
>> and blocks defined as "Prohibited Output" in Section 2.3 of RFC
>> 4013.
>> 
>> However, all characters in the ASCII range are "grandfathered"
>> into the PRECIS NameClass.  As a result, common constructions
>> such as "[email protected]" are allowed as simple user names when
>> using software that conforms to this specification, as they were
>> under [RFC4013].
> 
> I don't see this as a necessary addition. It was quite clear from
> the specifications that the ASCII range was grandfathered in
> NameClass. It appears I was unclear in stating my concern, let me
> try again to explain my concern.

Yes, I did misconstrue your question.

> My concern is that login identities should be able to contain a
> valid IDNA U-label. It is not clear to me if NameClass permits all
> valid U-labels. If it does not, then I believe using NameClass for
> login identities is a mistake. The [email protected] form for login
> identities will continue to be useful as the infrastructure is
> expanded to allow UTF-8 characters in both the "user" part and the
> "example.com" part of that form. If we disallow valid U-labels in
> login identities then we break the multi-domain model for lots of
> software out there and will force that software to change its
> architecture when it adopts this technology or to choose not to
> adopt this technology. If valid IDNA U-labels are permitted in
> login identities then implementers can keep their current
> architecture and adopt saslprepbis.

Ah, I see. You raise a good question. The intent was that any code
point allowed in IDNs would be allowed in the PRECIS NameClass, but
looking closely at draft-ietf-precis-framework I realize that the
intent might not be reflected in the spec right now. I will
investigate further and post again when I have something definitive to
report.

Peter

- -- 
Peter Saint-Andre
https://stpeter.im/


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