Hi Ryan!

From: Ryan Sleevi <[email protected]>
Sent: Friday, August 13, 2021 4:26 PM
To: Roman Danyliw <[email protected]>
Cc: Brian Sipos <[email protected]>; [email protected]
Subject: Re: [Acme] AD Review of draft-ietf-acme-dtnnodeid-04



On Fri, Aug 13, 2021 at 4:04 PM Roman Danyliw 
<[email protected]<mailto:[email protected]>> wrote:
I think the current options might be:

(1) Roughly what you said above + Make it clear that this document is NOT using 
the RFC5280 profile and simply reusing the data structures (but not the 
validation logic).  Related to this, and excuse my ignorance about DTN, would 
it be possible to constrain these non-RFC5280-conforming certificates from 
appear on the internet with some normative phrasing.  Technically, RFC5280 is 
the _Internet_ PKIX profile.  This document goes to great pains to separate the 
internet portion of the ACME protocol exchange and the validation happening 
over DTN (which might be considered a "limited domain" as framed by RFC8799).

(2) Revise RFC5280.  I'm loath to pursue this path unless we really need to.

I suspect that either of these options would be a quick way to doom 
interoperability. That is, for better or worse, RFC 5280 is _the_ profile of 
X.509 that is commonly targeted by libraries and implementations. Attempting to 
diverge here, or special-case exceptions, generally means that implementing an 
interoperable and spec-compliant implementation are increasingly unlikely, 
given the extant complexity inherent in X.509 and RFC 5280 to begin with (e.g. 
as so many implementations overlook RFC 4158 to their own peril - and to the 
harm of interop)

To that end, is

(3) Express the DTN ID as an otherName within the SAN, rather than a 
(non-conforming) URI

Not an option? The downside here is the obvious loss of nameConstraints 
processing (RFC 5280 does not define even a processing algorithm for otherName 
nameConstraints, which makes sense, given the complexities there vis-a-vis 
multiple distinct otherNames vs multiple otherNames that make up a single 
logical name), but if that's an acceptable trade-off, that likely represents 
the most interoperable path forward.

That's not to say otherName is readily supported "out of the box", although it 
is in some (e.g. most famously, Active Directory's use of the otherName for the 
userPrincipalName), but it fits within the "no special cases" goal of promoting 
interoperability, and lets one build/extend existing RFC 5280 implementations. 
Here, the lack of nameConstraints processing is a benefit, rather than a 
limitation - it makes processing and extracting such fields something 
relatively simple you can build on post-validation, if your library is not 
extensible or not receptive towards exposing library-level API support specific 
for DTN node IDs.

[Roman] Thanks for proposing another option.  I’d be interested to hear if this 
would be viable.  If I’m not mistaken, in addition to changing to otherName 
here, Section 4.4.1 of draft-ietf-dtn-tcpclv4 would also require revision.

Regards,
Roman
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