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

[yannick.beot@gmail.com]

No problem.
I’ll have a look and file an issue if needed

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De : Justin Richer
Envoyé le :mardi 11 octobre 2016 23:05
À : Yannick Béot
Cc : Luiz Omori; mitreid-connect at mit.edu
Objet :Re: [mitreid-connect] JWT Signatures - which public key?

Yannick, thanks for that pointer. Could you please add an issue to the MITREid Connect project to use those classes? The references will be helpful as well.

 — Justin

On Oct 11, 2016, at 4:59 PM, Yannick Béot <yannick.beot at gmail.com> wrote:

If you use JWSVerificationKeySelector from Nimbus to check the JWT (as stated http://connect2id.com/products/nimbus-jose-jwt/examples/validating-jwt-access-tokens), you should be fine.. 
JWSKeySelector is filtering keys with a JWKMatcher which checks the kid (https://bitbucket.org/connect2id/nimbus-jose-jwt/src/3810eb0a96565e7768cd54bf734dfea373ecc561/src/main/java/com/nimbusds/jose/jwk/JWKMatcher.java?at=4.15&fileviewer=file-view-default#JWKMatcher.java-562) 

JWSVerificationKeySelector is responsible for creating the JWKMatcher based on information from the signature, and especially the kid (https://bitbucket.org/connect2id/nimbus-jose-jwt/src/3810eb0a96565e7768cd54bf734dfea373ecc561/src/main/java/com/nimbusds/jose/proc/JWSVerificationKeySelector.java?at=4.15&fileviewer=file-view-default#JWSVerificationKeySelector.java-70)
@Luiz: what are you using to validate the token? 


On Tue, Oct 11, 2016 at 9:13 PM, Justin Richer <jricher at mit.edu> wrote:
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"
    },
    {
      "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
 
You should use it to differentiate the keys.
 
 
Envoyé de mon téléphone Windows 10
 
De : Luiz Omori
Envoyé le :mardi 11 octobre 2016 18:04
À : 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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