Getting 400 Server Error in LTI 1.3 Deep Linking

[KartikShah]

Hi Team,

We are trying to implement LTI 1.3 Advantage (Deep Linking) in our tool, we are able to generate JWT token and while sending that token to the Canvas server we are getting below error.

{"errors":{"jwt":[{"attribute":"jwt","type":"JWT format is invalid","message":"JWT format is invalid"}]}}

We have verified the response JWT, which is per the LTI standard. Attached is the same below.

Header (The kid is matched with my inserted jwks kid)

{
  "alg": "RS256",
  "kid": "RV6OzALomjinkCIWc9QXYnRBxJw0jzWcdf6a8M05Mye6RaPqilZI81ptDsWLc90q",
  "typ": "JWT"
}

Payload

{
  "https://purl.imsglobal.org/spec/lti/claim/message_type": "LtiDeepLinkingResponse",
  "https://purl.imsglobal.org/spec/lti/claim/version": "1.3.0",
  "iss": "<canvas-client-id>",
  "aud": "https://canvas.instructure.com",
  "exp": "1674118953",
  "iat": "1674118653",
  "nonce": "HeP1fUhtbus",
  "azp": "EptPvHHKXr0",
  "https://purl.imsglobal.org/spec/lti/claim/deployment_id": "11796:896746821c480c1601d9f9521a6f454e8cb7625a",
  "https://purl.imsglobal.org/spec/lti-dl/claim/content_items": [
    {
      "text": "Diffusion Description",
      "title": "Diffusion",
      "type": "ltiResourceLink",
      "url": "https://my-url.cloudfront.net/nurl/index.html"
    }
  ]
}

Can anyone please help me with the resolution?

[svickers2]

The two things I would suggest you try first are to make the aud claim an array (this is not required but recommended, I believe), and either drop the azp claim (which is optional) or make sure that it is the same value as the aud claim.