def InferUserAndSubjectFromUrn(self):
    """Infers user name and subject urn from self.urn."""
    _, cron_str, cron_job_name, user, _ = self.urn.Split(5)

    if cron_str != "cron":
      raise access_control.UnauthorizedAccess(
          "Approval object has invalid urn %s." % self.urn,
          requested_access=self.token.requested_access)

    return (user, aff4.ROOT_URN.Add("cron").Add(cron_job_name))