# Returns a valid response when a request has appropriate credentials.
def main(request, response):
    cookie = request.cookies.first(b"cookieName", None)
    expected_value = request.GET.first(b"value", None)
    source_origin = request.headers.get(b"origin", None)

    response_headers = [(b"Content-Type", b"text/javascript"),
                        (b"Access-Control-Allow-Origin", source_origin),
                        (b"Access-Control-Allow-Credentials", b"true")]

    if cookie == expected_value:
        return (200, response_headers, u"")

    return (404, response_headers)