Thanks for pointing out that the JOSE header parameter usage location
registrations at
https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-header-parameters
for “iss”, “sub”, and “aud” were only for JWE. I believe that was an
oversight on our part.
As for “enforcement power”, the registrations ensure that those parameters can
be used in JWEs. But the registrations don’t prevent them from being used in
other ways or for other claims to be used.
Thanks again for your careful attention to this specification!
-- Mike
From: AJITOMI Daisuke <[email protected]>
Sent: Friday, June 30, 2023 8:47 PM
To: Michael Jones <[email protected]>
Cc: Cose Chairs Wg <[email protected]>; cose <[email protected]>; Mike Prorock
<[email protected]>; Ivaylo Petrov <[email protected]>; Tobias Looker
<[email protected]>; Orie Steele <[email protected]>
Subject: Re: [COSE] 🔔 WGLC of draft-ietf-cose-cwt-claims-in-headers
Hi Mke,
I'm sorry for the late reply. I did not have any time to check the COSE WG
mailing list for the past few weeks...
And thank you for incorporating my comment into the latest draft.
Your explanation helped me understand your design policy and thank you again,
but I would like to add one thing because my previous comment may have been
insufficient and lead to misunderstanding.
In JWT, any claim can be duplicated to a header parameter. This is described
in https://www.rfc-editor.org/rfc/rfc7519.html#section-5.3. There was no
restriction on use in structures without payloads, etc. It’s a design goal of
CWT to be as parallel to JWT as possible. Therefore, I don’t think it makes
sense to impose restrictions on CWTs that were not made in JWTs.
RFC7519#section-5.3 describes only the JWE thing but, as you pointed out, this
section does not have any restrictions regarding the structures that can have
JWT claims.
However, The IANA Registry for JOSE
(https://www.iana.org/assignments/jose/jose.xhtml) have a "Header Parameter
Usage Location(s)" column and it seems to me that it limits the use of JWT
claims to JW"E".
I'm not sure of the importance (enforcement power?) of the "Header Parameter
Usage Location(s)" column, but from the perspective of aligning the constraints
of CWT with JWT as much as possible, I pointed this out.
I understand your policy of not wanting to impose constraints on the locations
where the CWT claims can be used, without limiting the use cases.
Therefore, I leave the final decision on whether to focus on the Encrypt
structures or not up to you. Whichever you choose, I support the latest version
being published.
Best regards,
Daisuke
2023年6月30日(金) 12:52 Michael Jones
<[email protected]<mailto:[email protected]>>:
https://www.ietf.org/archive/id/draft-ietf-cose-cwt-claims-in-headers-05.html
moves the statement about verifying that claim values present in both the
header and payload are identical from the Security Considerations to the body
of the specification. I’ll note that -04 already said that “It is RECOMMENDED
that the CWT claims header parameter is used only in a protected header” and
that remains in -05.
Thanks again for your review, Daisuke.
-- Mike
From: Michael Jones
Sent: Monday, June 19, 2023 11:56 AM
To: AJITOMI Daisuke <[email protected]<mailto:[email protected]>>; Cose Chairs
Wg <[email protected]<mailto:[email protected]>>; cose
<[email protected]<mailto:[email protected]>>
Cc: Mike Prorock <[email protected]<mailto:[email protected]>>; Ivaylo Petrov
<[email protected]<mailto:[email protected]>>; Tobias Looker
<[email protected]<mailto:[email protected]>>; Orie Steele
<[email protected]<mailto:[email protected]>>
Subject: RE: [COSE] 🔔 WGLC of draft-ietf-cose-cwt-claims-in-headers
Thanks for the review, Daisuke! Responses are inline below in green.
From: AJITOMI Daisuke <[email protected]<mailto:[email protected]>>
Sent: Tuesday, May 2, 2023 3:57 PM
To: Cose Chairs Wg <[email protected]<mailto:[email protected]>>; cose
<[email protected]<mailto:[email protected]>>
Cc: Mike Prorock <[email protected]<mailto:[email protected]>>; Michael Jones
<[email protected]<mailto:[email protected]>>; Ivaylo
Petrov <[email protected]<mailto:[email protected]>>; Tobias Looker
<[email protected]<mailto:[email protected]>>; Orie Steele
<[email protected]<mailto:[email protected]>>
Subject: Re: [COSE] 🔔 WGLC of draft-ietf-cose-cwt-claims-in-headers
Hi authors,
I read the draft for the first time today. I think it's basically fine, but
there are some points I'm concerned about, so I'd like to make some comments
from an imprementor's perspective.
1) I think it would be better to limit the COSE structures that can have the
CWT claims parameter.
Specifically, I think the use of the CWT claims parameter should be limited
only for COSE_{Encrypt0, Encrypt} and the COSE structures without payloads
(COSE structures with detached contents). I'm not sure whether it should be
MUST, SHOULD or RECOMMENDED though. In JOSE as well, I believe the JWT claims
were only partially usable (only "iss", "sub", "aud") in JWE.
In JWT, any claim can be duplicated to a header parameter. This is described
in https://www.rfc-editor.org/rfc/rfc7519.html#section-5.3. There was no
restriction on use in structures without payloads, etc. It’s a design goal of
CWT to be as parallel to JWT as possible. Therefore, I don’t think it makes
sense to impose restrictions on CWTs that were not made in JWTs.
2) Similarly, I believe that there is no need to enable the use of the CWT
claims parameter in COSE_Recipient or COSE_Signature, as it doesn't seem
meaningful.
If my understanding is correct, it might be helpful to mention this somewhere
in the document.
Successful specifications are used in ways that the authors never envisioned,
provided they are written to enable general applicability. For instance, I
never imagined JWTs would be used to secure Caller-ID, but that very thing has
happened in the STIR working group, in specs such as RFC 8224. The same is
already true of CWTs. Therefore, I’m very reluctant to limit the applicability
of the CWT claims-in-headers feature because, as a general-purpose feature, we
are unlikely to be able to guess the productive ways that it will be used.
3) I think it would be better to limit the use of the CWT claims parameter only
to the protected header.
I believe there is no need to leave room for using it in the unprotected
header, as it would increase security concerns.
I’m fine suggesting that use in the protected headers is preferred in the
Security Considerations. But as above, it seems unwise to impose arbitrary
restrictions on the applicability of the feature.
4) I think the following sentence in Security Considerations might be better
written in the main body of this specification. Is there any reason not to
write it in Chapter 2?
"In cases where CWT claims are both present in the payload and the header, an
application receiving such a structure MUST verify that their values are
identical, unless the application defines other specific processing rules for
these claims."
I’m fine with promoting this sentence to the main body of the specification.
If there are any off-the-mark comments due to my lack of understanding of the
context, I apologize in advance.
Not at all. I appreciate you taking the time to review the specification and
make concrete suggestions. The “understanding the context” point is right on.
Some of my responses above essentially say that we don’t have a crystal ball to
gaze into to know the contexts in which the CWT feature will be used in advance.
Best regards,
AJITOMI Daisuke
Best wishes,
-- Mike
2023年4月28日(金) 7:53 Orie Steele
<[email protected]<mailto:[email protected]>>:
I support publication.
On Thu, Apr 27, 2023, 5:20 PM Mike Prorock
<[email protected]<mailto:[email protected]>> wrote:
I believe that this is ready to go as well.
Mike Prorock
mesur.io<http://mesur.io/>
On Thu, Apr 27, 2023, 15:31 Michael Jones
<[email protected]<mailto:[email protected]>> wrote:
I believe that this specification is ready for publication.
-- Mike
From: Ivaylo Petrov <[email protected]<mailto:[email protected]>>
Sent: Thursday, April 27, 2023 1:23 PM
To: [email protected]<mailto:[email protected]>; Tobias
Looker <[email protected]<mailto:[email protected]>>; cose
<[email protected]<mailto:[email protected]>>
Cc: Cose Chairs Wg <[email protected]<mailto:[email protected]>>
Subject: 🔔 WGLC of draft-ietf-cose-cwt-claims-in-headers
Dear all,
This message starts the formal Working Group Last Call of the
draft-ietf-cose-cwt-claims-in-headers [1].
The working group last call will run for **two weeks**, ending on May 12, 2022.
Please review and send any comments or feedback to the working group. Even if
your feedback is "this is ready", please let us know.
Thank you,
- Mike and Ivaylo
COSE Chairs
[1]:
https://www.ietf.org/archive/id/draft-ietf-cose-cwt-claims-in-headers-04.html
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