[Lake] Re: CDDL in EDHOC RFC 9528

[Carsten Bormann <[e-mail]>]

Hi Brian,

thank you for looking into this.
Whatever comes out of this I would like to reflect in

https://www.ietf.org/archive/id/draft-bormann-cbor-rfc-cddl-models-04.html

(And the accompanying library of referenceable CDDL specifications in the cddlc tool.)

On 2024-10-16, at 14:41, Sipos, Brian J. <[e-mail]> wrote:
> […]
>    EAD_1 = (1* ead)

Right.  Actually, this should be a + instead of a 1*, + is much more idiomatic in CDDL.

> Another is the lack of a type within the `PLAINTEXT_2` group for the field `C_R` which just seems like a simple omission.

I’m not entirely sure I understand these CDDL snippets, e.g., ID_CRED_I also isn’t defined as a type.
 
> Finally, there is the use of a type `map` within the ID_CRED_x fields, which is not actually defined anywhere for CDDL. So I added a local definition
>     map = #5
> I’m not sure if that is the best way to handle this situation. Another alternative would be something more CDDL-like
>     { * any => any }

If this is what you want, I’d prefer that a lot over #5.
But maybe it actually isn’t *any* map?

BTW, map is not a predefined name so you can say

map = { * any => any }

if you like...

> I don’t think the two differ in what they will match but maybe the second form is more tool-friendly?

The original cddl tool can be very specific in its taste, so you’ll get

  Can't generate prim 5 (RuntimeError)

for   map = #5

> As a suggestion for readability, I also think it’s helpful to have a couple of shared-type rules to make it obvious where different fields really do share the same type. One for connection IDs (shared between `C_I` and `C_R`) and one for credential IDs (shared between `ID_CRED_I` and `ID_CRED_R`) as the following
>     id_conn = bstr / -24..23
>     id_cred = map / bstr / -24..23

Very good idea.
We could include CDDL that has been combed through a bit in the above I-D.

Grüße, Carsten

>  
> Thanks for any feedback,
> Brian S.
>  
> [1] https://www.rfc-editor.org/rfc/rfc9528.html#appendix-C.2
> [2] https://crates.io/crates/cddl
> [3] https://rubygems.org/gems/cddl
>  
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