Re: [secdir] [jose] JWK member names, was: SECDIR review of draft-ietf-jose-json-web-key-31

[John Bradley <[e-mail]>]

Inline
On Sep 15, 2014, at 6:21 PM, Tim Bray <[e-mail]> wrote:

> On Mon, Sep 15, 2014 at 12:18 PM, John Bradley <[e-mail]> wrote:
> Are you recommending that:
> That receivers MUST reject JOSE objects with duplicate keys.  
> 
> This would require compliant implementations to write there own parsers (perhaps not a good idea), or wait for I-JSON parsers (perhaps sometime soonish)
> 
> ​Agree, sigh.​
> 
> 
> Or that JOSE require producers not to send dup keys, and receivers SHOULD reject them if possible based on the parser.
> 
> ​Yeah… MUST NOT send malformed JSON (I argue that an economical way to do that would be to reference I-JSON if the schedule works).  As for the receiver, I like SHOULD reject, but I’m wondering if we can get away with that given that a high proportion of receiving software will have no way to detect the error.​
> 
> 
> For JWE and JWS the header is integrity protected so we are talking about duplicate keys inserted by a bad producer rather than an attacker modifying the message after signing..
> 
> ​Whatever. If you get a busted message, something is wrong somewhere upstream.​
> 
> 
> I suspect the important issue is taking care that when producing a JWE/JWS you are not accepting arbitrary elements for the header without verifying that they are not JOSE parameters.
> 
> ​Hm, for ID Tokens, didn’t we do exactly the opposite, and end up with a Must-Ignore policy?​

Yes the receiver ignores unknown elements in the body of the JWT.  

I think that is different than a JWS/JWE library accepting additional parameters from a calling application to go into the envelope.   In that case the sender lib may want to check that they are not JW* reserved names that might cause some interoperability problems.

The lib producing the JWE/S is probably not going to normally duplicate elements on it's own.

Where I see it perhaps going bas is if someone is counting on the receiver taking the last one of a duplicate element and trying to override some header parameter by inserting a duplicate after the lib generated one.   This would work sometime and fail others depending on the receivers parser.

We probably want to be clear that anything extra going into an envelope needs to be checked to avoid reserved elements.

John B.
> 
> 
>  
> 
> John B.
> 
> 
> On Sep 15, 2014, at 3:54 PM, Tim Bray <[e-mail]> wrote:
> 
>> ​When I talk about existing software I’m referring to generic JSON parsers such as are included in the basic library set of every programming language now, and which are unfortunately idiosyncratic and inconsistent in their handling of dupe keys, but in almost no cases actually inform the calling software whether or not dupe keys were encountered.
>> 
>> On Mon, Sep 15, 2014 at 11:51 AM, Stephen Kent <[e-mail]> wrote:
>> OK, I'm a bit confused.
>> 
>> I thought the JOSE specs were intended to create standards for transport of keys, and for sigs,
>> MACs, and encryption of JSON objects.
>> 
>> What is the existing software to which you and Tim refer, when referring to keys (vs.
>> JSON parsing in general)?
>> 
>> Steve
>> 
>> 
>> 
>> 
>> -- 
>> - Tim Bray (If you’d like to send me a private message, see https://keybase.io/timbray)
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> -- 
> - Tim Bray (If you’d like to send me a private message, see https://keybase.io/timbray)