Re: [jose] Gen-Art LC review: draft-ietf-jose-jws-signing-input-options-06

Mike Jones <Michael.Jones@microsoft.com> Mon, 14 December 2015 04:04 UTC

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From: Mike Jones <Michael.Jones@microsoft.com>
To: Robert Sparks <rjsparks@nostrum.com>, General Area Review Team <gen-art@ietf.org>, "ietf@ietf.org" <ietf@ietf.org>, "jose@ietf.org" <jose@ietf.org>, "draft-ietf-jose-jws-signing-input-options@ietf.org" <draft-ietf-jose-jws-signing-input-options@ietf.org>
Thread-Topic: Gen-Art LC review: draft-ietf-jose-jws-signing-input-options-06
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Date: Mon, 14 Dec 2015 04:04:45 +0000
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Subject: Re: [jose] Gen-Art LC review: draft-ietf-jose-jws-signing-input-options-06
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Hi Robert,

You asked "_WHY_ is crit not sufficient? I think that's the thing that's missing as motivation."

There are two goals we're discussing, which are related:
(a) Having an application that uses "b64":false work.
(b) Having an application that receives a JWT with "b64":false not misinterpret the payload content.

Including "crit":["b64"] would be sufficient to achieve (b), as it would cause the JWS to be rejected by implementations not supporting "b64".  But it does not achieve (a), since the JWS would be rejected.

In contrast, using an implementation that understands "b64" achieves both (a) and (b) without needing to include "crit".  That's why it's not required.

Does that make sense now?

				Best wishes,
				-- Mike 

-----Original Message-----
From: Robert Sparks [mailto:rjsparks@nostrum.com] 
Sent: Sunday, December 13, 2015 1:11 PM
To: Mike Jones <Michael.Jones@microsoft.com>om>; General Area Review Team <gen-art@ietf.org>rg>; ietf@ietf.org; jose@ietf.org; draft-ietf-jose-jws-signing-input-options@ietf.org
Subject: Re: Gen-Art LC review: draft-ietf-jose-jws-signing-input-options-06

Cutting away a bit to focus on the question:

On 12/12/15 8:32 PM, Mike Jones wrote:
> Hi Robert.  Thanks for the useful review.  Replies are inline below...
>
>> -----Original Message-----
<snip/>
>>
>>
>> I would have been much more comfortable with a consensus to require 'crit'.
>> (Count me in the rough if this proceeds with crit being optional).
>>
>> I assume there is a strong reason to allow for option 1. Please add 
>> the motivation for it to the draft, and consider adding a SHOULD use 'crit'
>> requirement if option 1 remains.
> It's a reasonable request to have the draft say why "crit" isn't required.  My working draft adds the following new paragraph at the end of the security considerations section to do this.  Unless I hear objections, I'll plan on publishing an updated draft with the paragraph shortly.
>
> "Note that methods 2 and 3 are sufficient to cause JWSs using this extension to be rejected by implementations not supporting this extension but they are not sufficient to enable JWSs using this extension to be successfully used by applications.
The conclusion you draw here is not at all obvious.
_WHY_ is crit not sufficient? I think that's the thing that's missing as motivation.

>   Thus, method 1 - requiring support for this extension - is the preferred approach and the only means for this extension to be practically useful to applications. Method 2 - requiring the use of <spanx style="verb">crit</spanx> - while theoretically useful to ensure that confusion between encoded and unencoded payloads cannot occur, is not particularly useful in practice, since method 1 is still required for the extension to be usable. When method 1 is employed, method 2 doesn't add any value and since it increases the size of the JWS, its use is not required by this specification."
>
>> Nits/editorial comments:
>>
>> In the security considerations, the last sentence of the first 
>> paragraph needs to be simplified. I suggest replacing it with:
>>
>> "It then becomes the responsibility of the application to ensure that 
>> payloads only contain characters that will not cause parsing problems 
>> for the serialization used, as described in Section 5. The 
>> application also incurs the responsibility to ensure that the payload 
>> will not be modified during retransmission.
> I have simplified this in the manner that you suggested.
>
> 				Thanks again,
> 				-- Mike