nullPage.js

async function main() {

  window.parent.postMessage("ready", "*");
  const config = await new Promise((ok, fail) => {

    console.log("waiting for config...")

    window.addEventListener("message", ({ data }) => {

      console.log("got config message");

      if (data.type !== "config") return fail(`did not get config, instead got ${JSON.stringify(data)}`);

      return ok(data);
    }, { once: true })

  });

  console.log({ config });
  console.log("now any data the null origin gets is sent to the icloud iframe...");

  window.addEventListener("message", ({ data }) => {
    console.log("forwarding to idmsa", data)
    window.top.frames[config.idmsaFrameId].postMessage(data, "*");
  });
}


main().catch(e => console.error(e))