how to test a launch function

[perllaghu]

I've a working system - I can connect from a test moodle to my tool - and now I want to add a test for the code.

My test code starts:

Overall imports

from rest_framework_jwt.settings import api_settings as jwt_settings
from mock import patch
from unittest.mock import Mock
from urllib import parse
from django.test import Client
from myApp.lti1p3_backend import ToolConfMyApp # My version of DjangoDbToolConf
from myApp_utils.test_utils import TestCreators  # some helper methods for creating test objects in the db

class TestToolConfMyApp(TestCreators):

There are a whole suite of tests for the ToolConfMyApp functions: check_iss_has_one_client, check_iss_has_many_clients, get_public_key, get_iss_config, etc...

I've even got POST and GET tests for login - and test the parameters in the response.url from those calls

For the specific launch test - this is what I start with:

    @patch('pylti1p3.message_launch.MessageLaunch.fetch_public_key')
    def test_launch(self, mock_fpk: Mock):

        # Set up the environment, and the initial login
        key = self.create_lti1p3_tool_key(name="test", private_key="foo", public_key=pub_key)
        self.create_lti1p3_tool(
            title="test",
            tool_key=key,
            issuer="example_dot_com",
            client_id="foo",
            auth_login_url="http://example.com/a",
            auth_token_url="http://example.com/b",
            deployment_ids='["test-id-1", "test-id-2"]',
            key_set_url="http://example.com/c",
        )
        c = Client()
        response = c.get("/lti1p3/login/?lti1p3_new_window=1&iss=example_dot_com&login_hint=5&target_link_uri=http%3A%2F%2Fexample.com%2Flti1p3%2Flaunch%2F&lti_message_hint=5&lti_deployment_id=3&client_id=foo")

        # Cookies should now exist, test launch

Then we want to set up the token for actual call:

        query_string = parse.urlparse(response.url)[4]
        query_dict = parse.parse_qs(query_string)
        tool_conf = ToolConfNoteable()
        mock_fpk.return_value = tool_conf.get_jwks("example_dot_com")

        # create id_token that VLE creates - needs nonce to match login nonce!
        source_token = {
            "nonce": query_dict["nonce"][0],
            "iat": 1649251764,
            "exp": 1649251824,
            "iss": "example_dot_com",
            "aud": "foo",
            "https://purl.imsglobal.org/spec/lti/claim/deployment_id": "test-id-1",
            "https://purl.imsglobal.org/spec/lti/claim/target_link_uri": "http://vle.example.com/lti1p3/launch/",
            "sub": "5",
            "https://purl.imsglobal.org/spec/lti/claim/lis": {
                "person_sourcedid": "",
                "course_section_sourcedid": ""
            },
            "https://purl.imsglobal.org/spec/lti/claim/roles": [
                "http://purl.imsglobal.org/vocab/lis/v2/institution/person#Administrator",
                "http://purl.imsglobal.org/vocab/lis/v2/membership#Instructor",
                "http://purl.imsglobal.org/vocab/lis/v2/system/person#Administrator"
            ],
            "https://purl.imsglobal.org/spec/lti/claim/context": {
                "id": "3",
                "label": "sample_course",
                "title": "An Example of a Course Title",
                "type": [
                "CourseSection"
                ]
            },
            "https://purl.imsglobal.org/spec/lti/claim/resource_link": {
                "title": "some link text",
                "id": "3"
            },
            "https://purl.imsglobal.org/spec/lti-bo/claim/basicoutcome": {
                "lis_result_sourcedid": "{\"data\":{\"instanceid\":\"3\",\"userid\":\"5\",\"typeid\":\"3\",\"launchid\":1293835966},\"hash\":\"f85b809cb4b10a0bb65ce2824e8c892a2d08f6a2015edd68d3ccaf014486cf81\"}",
                "lis_outcome_service_url": "https://vle.example.com/lti/service.php"
            },
            "given_name": "Jo",
            "family_name": "Doe",
            "name": "Jo Doe",
            "https://purl.imsglobal.org/spec/lti/claim/ext": {
                "user_username": "student1",
                "lms": "moodle-2"
            },
            "https://purl.imsglobal.org/spec/lti/claim/launch_presentation": {
                "locale": "en",
                "document_target": "window",
                "return_url": "https://vle.example.com/lti/return.php?course=3&launch_container=4&instanceid=3&sesskey=BKH3oeWS3f"
            },
            "https://purl.imsglobal.org/spec/lti/claim/tool_platform": {
                "product_family_code": "moodle",
                "version": "2020061512",
                "guid": "vle.example.com",
                "name": "vle.example.com",
                "description": "VLE for example.com"
            },
            "https://purl.imsglobal.org/spec/lti/claim/version": "1.3.0",
            "https://purl.imsglobal.org/spec/lti/claim/message_type": "LtiResourceLinkRequest",
            "https://purl.imsglobal.org/spec/lti/claim/custom": {
                "course_suffix": "foo",
                "system_setting_url": "https://vle.example.com/lti/services.php/tool/3/custom",
                "context_setting_url": "https://vle.example.com/lti/services.php/CourseSection/3/bindings/tool/3/custom",
                "link_setting_url": "https://vle.example.com/lti/services.php/links/{link_id}/custom"
            },
            "https://purl.imsglobal.org/spec/lti-ags/claim/endpoint": {
                "scope": [
                "https://purl.imsglobal.org/spec/lti-ags/scope/lineitem",
                "https://purl.imsglobal.org/spec/lti-ags/scope/lineitem.readonly",
                "https://purl.imsglobal.org/spec/lti-ags/scope/result.readonly",
                "https://purl.imsglobal.org/spec/lti-ags/scope/score"
                ],
                "lineitems": "https://vle.example.com/lti/services.php/3/lineitems?type_id=3",
                "lineitem": "https://vle.example.com/lti/services.php/3/lineitems/5/lineitem?type_id=3"
            }
        }
        jwt_encode_handler = jwt_settings.JWT_ENCODE_HANDLER
        token = jwt_encode_handler(source_token)

        response = c.post("/lti1p3/launch/?", {"state": query_dict["state"][0], "id_token": token})

.... and it fails with a pylti1p3.exception.LtiException: JWT KID not found error.

The full error reads:

Traceback (most recent call last):
  File \"/path/to/lib/python3.7/site-packages/django/core/handlers/exception.py\", line 47, in inner
    response = get_response(request)
  File \"/path/to/lib/python3.7/site-packages/django/core/handlers/base.py\", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File \"/path/to/lib/python3.7/site-packages/sentry_sdk/integrations/django/views.py\", line 36, in sentry_wrapped_callback
    return callback(request, *args, **kwargs)
  File \"/path/to/lib/python3.7/site-packages/django/views/generic/base.py\", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File \"/different/path/to/mycomponent/api/views.py\", line 554, in dispatch
    return super().dispatch(*args, **kwargs)
  File \"/different/path/to/mycomponent/api/views.py\", line 494, in dispatch
    payload = self.add_extra_jwt_claims(payload)
  File \"/different/path/to/mycomponent/api/views.py\", line 564, in add_extra_jwt_claims
    message_launch_data = message_launch.get_launch_data()
  File \"/path/to/lib/python3.7/site-packages/pylti1p3/message_launch.py\", line 494, in get_launch_data
    return self._get_jwt_body()
  File \"/path/to/lib/python3.7/site-packages/pylti1p3/message_launch.py\", line 299, in _get_jwt_body
    self.validate()
  File \"/path/to/lib/python3.7/site-packages/pylti1p3/message_launch.py\", line 284, in validate
    return self.validate_state()\\
  File \"/path/to/lib/python3.7/site-packages/pylti1p3/message_launch.py\", line 671, in validate_jwt_signature
    public_key = self.get_public_key()
  File \"/path/to/lib/python3.7/site-packages/pylti1p3/message_launch.py\", line 569, in get_public_key
    raise LtiException(\"JWT KID not found\")
pylti1p3.exception.LtiException: JWT KID not found

Digging into the code, the problem seems to be the contents of self._jwt in the MessageLaunch.get_public_key method has the id_token rather than the jwks

Any hints as to where I'm going wrong?

EDIT:
I can confirm that tool_conf.get_jwks("example_dot_com") returns an appropriate token:

{
    "alg": "RS256",
    "e": "AQAB",
    "kid": "9uXgneuBIDrQQprq9DVtQ0Za-elqN5wHsviNOtLmQdY",
    "kty": "RSA",
    "n": "u9omeEgZmWHV0448LhGFFUzpGynHhLN88sdbbHP7tEd67zcqfbSoeWiIWbVCwXFVrkTZNjXb5YANNcBrj7bOj6nGNvevYMM5YgxhfjvJ2rbAfPNtjeUzaj95la2wO14rc9b32FmMSzLE5xn5I8HqXZUHPH0W5VS3avBp_v-dyLTacXmlvzvDgJ2gNT9vPiUWLXSS9SajIYr7Sj5IILjSlHod5UkHGSyi7sK5vSpArOh3LbzM0fPPCqupIb6bouDgYRxjUqSphvY891nRMCWtQKXO4aOk65AqqQsRnQovLiyDxPYMesc3kZcNsuPlWyF5YNE81EcmdXRnrkBKqowdZQ",
    "use": "sig",
}