[mitreid-connect] JWT Signatures - which public key?

[Justin Richer]

The “kid” will be in the header of the JWT you’re validating. I think we’ve got a long-standing issue to enforce that check in the client library, but it should still work as-is.

 — Justin

> On Oct 11, 2016, at 12:27 PM, Luiz Omori <luiz.omori at duke.edu> wrote:
> 
> Well, which “kid” value should we look for? I checked the <root>/.well-known/openid-configuration and although it lists the jwk endpoint we couldn’t find the “kid” anywhere. Does it mean this info has to be transmitted offline?
>  
> {
>   "keys":[
>     {
>       "alg":"RS256",
>       "e":"xxx",
>       "n":"xxx”,
>       "kty":"RSA",
>       "use":"enc",
>       "kid":"mc.duke.edu <http://mc.duke.edu/>"
>     },
>     {
>       "e":"xxx",
>       "n":"xxx”,
>       "kty":"RSA",
>       "kid":"Test1"
>     },
>     {
>       "e":"xxx",
>       "n":"xxx”,
>       "kty":"RSA",
>       "kid":"Test2"
>     },
>     {
>       "e":"xxx",
>       "n":"xxx",
>       "kty":"RSA",
>       "kid":"rsa1"
>     }
>   ]
> } 
>  
> From: "yannick.beot at gmail.com" <yannick.beot at gmail.com>
> Date: Tuesday, October 11, 2016 at 12:16 PM
> To: Luiz Omori <luiz.omori at duke.edu>, "mitreid-connect at mit.edu" <mitreid-connect at mit.edu>
> Subject: RE: [mitreid-connect] JWT Signatures - which public key?
>  
> There is a key id present in the header that is interpreted by Nimbus: https://tools.ietf.org/html/rfc7515#section-4.1.4 <https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_rfc7515-23section-2D4.1.4&d=CwMFaQ&c=imBPVzF25OnBgGmVOlcsiEgHoG1i6YHLR0Sj_gZ4adc&r=R6m41WT3w_KtulQAsSIxc_C2mwuKoWSycEMpss0QQJA&m=946nVG8V76cufZ4NS83yWjsqNfm4xIW2uP9rsciX32I&s=HLXHrA80eziVyXZG3UyPxIKg-x7A1JpFPBB-62UILWw&e=>
>  
> You should use it to differentiate the keys.
>  
>  
> Envoyé de mon téléphone Windows 10
>  
> De : Luiz Omori <mailto:luiz.omori at duke.edu>
> Envoyé le :mardi 11 octobre 2016 18:04
> À : mitreid-connect at mit.edu <mailto:mitreid-connect at mit.edu>
> Objet :[mitreid-connect] JWT Signatures - which public key?
>  
> Hi,
>  
> In our implementation, the RS upon receiving a request it first validates the access token signature locally before introspecting it. To perform the signature validation we use a previously retrieved public key. The issue we are facing is that in our case the <root>/jwk endpoint is returning multiple keys. How do we figure out which one should be used? Should we check the “use” field? If yes, is there a standard value to check for?  
>  
> Regards,
> Luiz
>  
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