On Tue, Aug 27, 2019 at 2:28 AM Yaron Sheffer <[email protected]> wrote:

> The new version contains some significant changes:
>
> - Addition of the STIR use case.
> - Refinement of the CDNI use case.
> - Addition of the CSR template (partial, more work required).
> - Further security considerations (work in progress).
>
> Thanks,
>         Yaron
>

I was a bit surprised to not see any references to the Delegated
Credentials for TLS ( https://tools.ietf.org/html/draft-ietf-tls-subcerts )
specification. Is my understanding correct that these are functionally
addressing the same problem?

Introduction:
The introduction introduces the concept of NDC, but then transitions to use
the acronym CDN. Perhaps it would be useful to explicitly specify if you
meant a Content Delivery Network (CDN) to be a Name Delegation Consumer
(NDC), or if perhaps that was just a typo.

Also in the introduction, it states "Understandably, most IdOs balk at
sharing their long-term private keys", but this is difficult to quantify.
It would imply that most sites do not use CDNs, when I suspect the reality
is actually inverted - more sites use CDNs or hosting provider than those
that don't. Perhaps this should be updated to say "some IdOs", or perhaps
quantify as "IdOs may balk", both of which indicate possibilities without
indicating magnitude.

4.1.2 Chained Delegation
The use of the terms uCDN and dCDN are... a bit surprising. Could you
indicate a bit what those letters are meant to specify? My worry is that
the u will be seen as similar to the Greek letter mu - aka the prefix
typically used to indicate micro.

That said, I admit, I'm a bit confused about the protocol design attempting
to accommodate this. The motivation appears to be because "IdO may not even
know about dCDN", but then immediately following, it notes that such
proxying as proposed by the protocol is "governed by policy and contracts
between the parties". It seems that if the intent is to leave it to policy,
such accommodation may not be necessary. Alternative, if the intent is to
explicitly support this, it may be desirable to allow the IdO to express
its policy to the uCDN as to expectations related to the dCDN, rather than
relying upon an out-of-band mechanism.

6.1 Restricting CDNs to the Delegation Mechanism
There are RFC 2119 MUSTs attached here, when it seems these functionally
should be SHOULDs. That is, I think it's fair to highlight the
consideration of concerns between the IdO and the CDN, but I don't think
it's reasonable to normatively specify the policy consideration mechanism.
For example, as specified, those requirements would not be sufficient to
guarantee that a conforming CA uses this mechanism, as a number of CAs
"comply with ACME" (second bullet), but also offer additional validation
methods/issuance flows which also use the "dns-01" method.

As CAA is intentionally flexible to allow for CA-specific policy
identifiers to be expressed between the IdO and the CA, I think it's best
to change these to SHOULD, and to recognize that CAs may devise other means
of technically expressing this conformance, and that's between the IdO and
the CA. CAA provides the necessary component (to allow them to restrict to
CAs that respect CAA, to allow CA-specific policy), but I think that's the
extent to which policy-specific requirements can be made.
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