Re: [Anima] rfc822Name use in Autonomic Control Plane document

[Benjamin Kaduk <[e-mail]>]

Hi Brian,

On Fri, Jun 19, 2020 at 05:11:30PM +1200, Brian E Carpenter wrote:
> Hi Ben,
> 
> (Back on line after a couple of days spent moving apartments.)

(and me after getting slowed down by being sick)

> On 17-Jun-20 14:44, Benjamin Kaduk wrote:
> > Hi Brian, Michael,
> > 
> > On Tue, Jun 16, 2020 at 02:14:24PM +1200, Brian E Carpenter wrote:
> >> On 16-Jun-20 12:20, Michael Richardson wrote:
> >>>
> >>> Hi, I have had a few conversations with Toerless who is trying to deal with
> >>> the feedback on the ACP document.
> >>>
> >>> An item that has come up is the use, or claimed abuse of the rfc822Name SAN.
> >>>
> >>> We already had this debate.
> >>> Some time ago.  The WG decided.
> > 
> > With all due respect, this is not the sole decision of the ANIMA WG to
> > make.  If WGs had such authority then why bother with cross-area review?
> 
> Yes, but that was exactly the reason we had the discussion a year ago.

I think the expansion of the "we" is important, here -- who did you have in
mind?

> >>> Three or four years ago, I think.
> >>
> >> Yes, this is relitigating an issue that was resolved a long time ago in discussing Ben's DISCUSS:
> > 
> > I'm not sure I understand why you use the word "resolved" here:
> > 
> >> https://mailarchive.ietf.org/arch/msg/anima/lnZ-ykqas487qih86sYNVsUGbsc
> > 
> > In this message, I say that "I still feel like this is not the best
> > architectural choice" and that I will provide a sketch of an alternative in
> > my (then-)forthcoming ballot position; that ballot position retains the
> > Discuss-level concern about rfc822Name usage along with the promised
> > alternative.
> "Not the best choice" is not a DISCUSS criterion according to the IESG's own rules at https://www.ietf.org/about/groups/iesg/statements/iesg-discuss-criteria/#stand-undisc
> 
> It was exactly this sort of endless debate over "best choice" disagreements that caused the IESG to adopt the DISCUSS criteria rules in the first place.
> 
> If you are saying that one of the criteria in https://www.ietf.org/about/groups/iesg/statements/iesg-discuss-criteria/#stand-disc applies, that's a different matter, of course. But really, no AD should hold a DISCUSS over "not the best choice".

Sorry, that was the second round of Discuss and my politness filter may
have been overactive.  Allow me to rephrase:

I think that the use of rfc822Name in this document is inconsistent with
the specification for that field given in RFC 5280.  I do not believe that there
is IETF consensus (specifically, including the IETF PKIX community, e.g.,
the LAMPS WG) for this deviation from the RFC 5280 behavior, and it is not
documented (and consensus obtained for it) as such a deviation from RFC
5280.

I believe there are several ways in which the necessary functionality for
this specification can be obtained that remain consistent with RFC 5280;
specifying the use of any of them would suffice to resolve the Discuss
point.  The "smallest diff to the text" option would be to define an
otherName OID to carry the same contents currently specified for
rfc822Name, but other options involving splitting the semantic components
into EKU/iPAddress SAN/extension/etc. are possible.  I could probably even
accept a non-normative note saying that some legacy deployments used the
rfc822Name field, though given Sean's review there would probably need to
be a pretty strong disclaimer of the risks of doing so.

[one more note at the end]

> Not to mention that this is only a Proposed Standard discussion; perfection not required.
> 
> I don't consider myself enough of a subject matter expert to comment on the technical issue itself.
> 
> Regards
>     Brian
> 
> > 
> >> The explanation is at https://tools.ietf.org/html/draft-ietf-anima-autonomic-control-plane-24#page-26
> > 
> > I appreciate that the attempted justification is clearly written; however,
> > I do not find it compelling.  Russ did not, either, and I just heard back
> > from Sean Turner a few days ago to confirm that he supports Russ's
> > comments.  (There should be a few other editorial-ish comments that came
> > out of that review that are still pending.)
> > 
> >> I believe it is incorrect IETF process to rediscuss this point yet again.
> > 
> > (I'm not sure if the "yet again" refers to "after the WG decided" or "after
> > the (alleged) resolution of my first Discuss point".)
> > 
> > If you believe the technical answer is clear and that I am in error to
> > continue to hold my Discuss point for it, are there not also clear IETF
> > processes to follow?  E.g., asking for the "Single Discuss" ballot procedure
> > described at https://www.ietf.org/standards/process/iesg-ballots/?  I
> > believe I have mentioned this option to Toerless previously; my apologies
> > if that is not the case.  While I'm willing to continue discussing the
> > topic and pull in additional PKIX experts to weigh in, there is perhaps
> > some consideration to matters of expediency.
> > 
> >>>
> >>> I sure wish that we could use something else.
> >>> But, CAs and CA software make that very difficult.
> >>>
> >>> Given that the era of publically anchored Enterprise CAs is dead, there are
> >>> only two ways an (Enterprise) ACP Registrar is going to occur.
> >>>
> >>> 1) by running a private CA.
> >>>    Sure anything is possible if you are writing your own code, but
> >>>    most will not be doing that. (I've supported otherName in my code for
> >>>    other purposes, and it's not that difficult, but it's not trivial either)
> >>>    My experience with COTS CA systems it that it's really hard to
> >>>    get them to do it.    Please prove me wrong.
> > 
> > (Sadly, I have zero experience with COTS CA systems; I know too much about
> > openssl at this point and would presumably be writing my own, in this
> > position.)
> > 
> >>>    The most popular Enterprise CA software is the Microsoft CA.
> >>>
> >>> 2) by using ACME to speak to a hosted CA.  Maybe WebPKI, maybe not.
> >>>    Either way, getting otherName supported is even harder, because
> >>>    nobody else uses it.
> > 
> > Is the concern the ACME protocol support or just getting the hosted CA to
> > cope with it?  The former seems like something that we could make happen in
> > the IETF, and the latter seems to have high overlap with point (1).
> > 
> >>> If we can't depend upon otherName being filled in, then we have to look for
> >>> two things.  That means more code paths (two more) to test, more test
> >>> vectors, and what exactly does an end point do when both are present, BUT
> >>> THEY DO NOT MATCH?  So three more pages of text there.
> >>> Remember, that just rejecting the certificate means that we have to send out
> >>> a truck, which is what ACP aims to avoid, so that won't be popular.
> >>> And of course, there could also be bugs (maybe even CVEs) in the code that
> >>> tries to deal with the tie.
> > 
> > To be honest, this argument feels like a stronger one to me than the bits
> > in the -24.  I'm still not willing to accept into the RFC Series a document
> > that violates the rules set down by the specification for the technology
> > it's making use of, but the refocus on the "running code" aspect is
> > appreciated.
> > 

Thinking about this a bit more, it seems like it would be doable (and, more
importantly, testable) to require that if the otherName (or whatever) is
present, there MUST NOT be an rfc822Name present.  Which doesn't
necessarily help with the "need to implement" bit for sites that use
rfc822Name, of course, but should avoid the worst of the risks for when two
sources of data don't match.

-Ben