My Publick JWK URL is not working

[RipunjayShuklaM]

I have developed an LTI 1.3 integration that is working successfully, including the Names & Roles service and Grade Passback. It works correctly with a Public Key or JWK value, but it is not working with my Public JWK URL (KeySet URL). My JWK URL is https://mbx-staging.getmagicbox.com/api/mag/lti/v1_3/keyset/690/jwks. Could you please help me identify the issue?

The response value is:

{
  "keys": [
    {
      "kty": "RSA",
      "e": "AQAB",
      "use": "sig",
      "kid": "4VVX",
      "alg": "RS256",
      "n": "ALt-j9QLyFJujrUU4XaL--twnv-RZ3mrfzDX71Q_FB7IodKQ5WjKNP3S-GgBgR2fcRL5iO-Kw62K1Mt130DzOGFf_Crt3Q9b5igoiNO7gxNDKPUmAmdT9aV6nFSMgTPthzWn-GpiSZK-7bPTl-frAsraX-w-NkNzTbLhEuelVMYtOd-Xndkz-EWEIoAUZ-2O1FFjCc5gr0vrPn4wzDB-xTiRcqeWr_lyDOs_2UzZ7RoBmkB1o83DZidEb8aEFjMR3m7-J-szaIAePeJSqcZOkFK_ah3OEtnwd_8sihJFYJMzsh4VlADv8rZPydeI0hIVKiFiNqkjptbze9jhVsfVYb0="
    }
  ]
} 

[matthew_buckett · Accepted solution]

Some things I've run into in the past with JWK URLs:

• The content-type header on your JWK URL, you have `application/json` which is known to work. Some RFCs state that `application/jwk-set+json` should also work but there have been reports of this being broken in the past (I'm not sure if it's fixed now).
• That you are adding a `kid` claim when creating your signed JWT. I think that when you upload a single JWK to Canvas it doesn't require you to set a `kid` claim in your JWT, but as soon as you switch to a JWK set (which can contain multiple JWKs) it refuses to verify the JWT unless it has a matching `kid` claim. I think this is the most likely problem.
• That the developer key values are correctly updating when saving. There used to be a bug where some JWK values didn't save correctly and if you still had a JWK URL set when you pasted in a JWK key it would continue to use the URL. This was really confusing when I was testing things, but the "fix" used to be to clear out the URL before switching the dropdown. I don't think this is the issue you're seeing but might not be helping with debugging.
• That the URL is accessible to Canvas. 

What error are you getting back from Canvas?

[RipunjayShuklaM]

Thanks for the support, Yes the issue was related to kid.