Fix for AWS API Gateway Custom Authorizer Error => AuthorizerConfigurationException (message: null)

AuthorizerConfigurationException-problem.txt

Problem: you've created a Custom Authorizer Lambda and have hooked it up with Amazon AWS's API Gateway.
But now all of your responses return the following HTTP response with the "AuthorizerConfigurationException"
and your Cloudwatch logs for your Authorizer function are next to useless..

-----

HTTP/1.1 500 Internal Server Error
Connection: keep-alive
Content-Length: 16
Content-Type: application/json
Date: Mon, 03 Feb 2020 22:12:26 GMT
Via: 1.1 b9061e936b29505d1b542db7af99b46c.cloudfront.net (CloudFront)
X-Amz-Cf-Id: V_ATyX6PguLX2OKELQaw7HIwyvKcU_bXJm3rXGsCp31UCwILvA70EA==
X-Amz-Cf-Pop: LHR61-C2
X-Cache: Error from cloudfront
x-amz-apigw-id: HV0fpFt_oAMFimA=
x-amzn-ErrorType: AuthorizerConfigurationException
x-amzn-RequestId: d889cc44-cf79-404a-af1d-c8cc1f09d5bc

{
    "message": null
}

solution.txt

Solution (or at least one possible one): Your code is generating a policy with an invalid context.

For example, in Python, your authorizer might return:

    return {
        "principalId": principal_id,
        "policyDocument": {
            "Version": "2012-10-17",
            "Statement": [
                {"Action": "execute-api:Invoke", "Effect": effect, "Resource": resource}
            ],
        },
        "context": {
            "some_nested_data": {
                "id": 3
            },
            "user_id": 4,
        },
    }
    
There are no valid keys in this example context.
    
The context _must_ abide by two rules:

1. All keys must be top level. No nested data.
2. All values must be strings, integers or booleans.

That means no setting nested JSON data to the context; and no making lists/arrays as the values.

When you get the data in your endpoint function, all the values will have been stringified.

Why? Absolutely fuck knows. Sorry, I can't help you there.

Life saver!