Hi all!

We are working on the remaining open issues regarding
draft-ietf-cose-cbor-encoded-cert. Below are two areas in which we are
interested in hearing the opinions of the community before making decisions
on which updates to make:

1. The encoding of the NameConstraints extension, applicable only for CA
certificates (originally defined in
https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.10)

NameConstraint contains GeneralSubtree, which in turn, in the current
version of the draft is defined as:


GeneralSubtree = [ GeneralName, minimum: uint, ? maximum: uint ]

Due to current limitations of how GeneralName is encoded, we need to either
update the GeneralName encoding (making it slightly longer). Alternatively,
limit the scope of the draft to certificates that don’t contain explicit
min-max specifications.

- Is the usage of min-max considered an important aspect which needs to be
supported, or an acceptable restriction to impose?

2. Limitations regarding the certificate policies extension; the current
version of the draft states the following restrictions:


“If noticeRef is not used and any explicitText are encoded as UTF8String,
the extension value can be CBOR encoded.”

With the following CDDL:


PolicyIdentifier = int / ~oid

PolicyQualifierInfo = (

  policyQualifierId: int / ~oid,

  qualifier: text,

)

CertificatePolicies = [

  + ( PolicyIdentifier, ? [ + PolicyQualifierInfo ] )

]

The RFC5280 defines the two PolicyQualifierIds CPS Pointer and User Notice (
https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.4).

The question to the community becomes:

- Are you aware of other PolicyQualifierInfo used, which include their own
non-text qualifiers? That is, is it worth the effort to make the qualifier
encoding more general, dependent on the policyQualifierId type.

A related issue is that there exist certificates using text types other
than the recommended UTF8String encoding for explicitText. This we suggest
accepting as a limitation, but are interested in hearing if there are other
opinions.

The current latest version 05 can be found here:

https://www.ietf.org/archive/id/draft-ietf-cose-cbor-encoded-cert-05.html

Looking forward to your input!

Joel Höglund
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