Hi John,

Is our intention that a chain is a CBOR sequence or is it a CBOR data item (an 
array)?  It seems the current text says it is a single data item.

> On 2021-05-24, at 12:00, John Mattsson 
> <[email protected]> wrote:
> 
> Hi,
>  
> When we discussed this at the meeting is was agreed to change 
> application/cbor to something more specific. The PR now use 
> "application/cose-x509-chain". And has the text "When the 
> application/cose-x509-chain media type is used, the data is a COSE_X509 
> structure containing a chain."
>  
> I just noticed that an IANA section registering the media type is missing. I 
> will add that to the PR. But before I do that:
>  
> - Is application/cose-x509-chain the right thing?
> - Or should it be application/cose-x509 allowing for both bag and chain?



> - Or should there be two media types application/cose-x509-chain and 
> application/cose-x509-bag?

That depends on whether the media type is needed to make the semantic 
distinction or that is taken from the context (here: header parameter).

The 8152 style was to have a single application/cose that would be further 
qualified by either an optional addition CBOR tag or an optional media-type 
parameter (cose-type=“…”).

(And don’t forget to define CoRE Content-Formats…)

Grüße, Carsten

 
> x5bag and x5chain separates bag and chain, while x5u could be either. Knowing 
> that it is a chain simplifies processing, but removes the option to transfer 
> additional certificates.
>  
> Cheers,
> John
>  
> From: John Mattsson <[email protected]>
> Date: Thursday, 13 May 2021 at 13:07
> To: cose <[email protected]>
> Subject: Re: [COSE] Pull-request addressing issues #29 #30 #31 #33 in 
> draft-ietf-cose-x509-08
> 
> Hi,
> 
> https://github.com/cose-wg/X509/pull/35
> 
> There are three remaining discussions related to the PR that has to be 
> concluded before merging the PR.
> 
> - Two of the discussion are more editorial comments from Ben.
> 
> - The third discussion is in my understanding more high-level and depend on 
> what COSE can require/expect/get information about from the CA(s). It also 
> depends on how much COSE should protect people from shooting themselves in 
> the foot. 
> 
> The current text is 
> 
> "Unless it is known that the CA required proof-of-possession of the subject's 
> private key to issue an end-entity certificate, the end-entity certificate 
> MUST be integrity protected by COSE."
> 
> Laurance commented that this is not enough and that the endpoints should 
> agree on which end-entity certificate is used. CAs may issue several 
> certificates with the same public key, and different CAs may issue several 
> certificates with the same public key.
> 
> Michael commented that this is overkill. There is also a discussion whether 
> the requirement should be MUST or SHOULD.
> 
> At a minimum I think the draft needs security consideration that discusses 
> that there might be many certificates with the same public key and unless 
> things are put in the protected header, the two endpoints might have 
> different views on which certificate was used.
> 
> I think this needs to be discussed on the list.
> 
> Cheers,
> John
> 
> 
> 
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