range-request-with-different-cors-modes-worker.js

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// This worker is meant to test range requests where the responses are a mix of

// opaque ones and non-opaque ones. It forwards the first request to a

// cross-origin URL (generating an opaque response). The server is expected to

// return a 206 Partial Content response.  Then the worker forwards subsequent

// range requests to that URL, with CORS sharing generating a non-opaque

// responses. The intent is to try to trick the browser into treating the

// resource as non-opaque.

//

// It would also be interesting to do the reverse test where the first request

// uses 'cors', and subsequent range requests use 'no-cors' mode. But the

// service worker cannot do this, because in 'no-cors' mode the 'range' HTTP

// header is disallowed.

importScripts('/common/get-host-info.sub.js')

let initial = true;

function is_initial_request() {

  const old = initial;

  initial = false;

  return old;

self.addEventListener('fetch', e => {

    const url = new URL(e.request.url);

    if (url.search.indexOf('VIDEO') == -1) {

      // Fall back for non-video.

      return;

    let cross_origin_url = get_host_info().HTTPS_REMOTE_ORIGIN +

        url.pathname + url.search;

    // The first request is no-cors.

    if (is_initial_request()) {

      const init = { mode: 'no-cors', headers: e.request.headers };

      const cross_origin_request = new Request(cross_origin_url, init);

      e.respondWith(fetch(cross_origin_request));

      return;

    // Subsequent range requests are cors.

    // Copy headers needed for range requests.

    let my_headers = new Headers;

    if (e.request.headers.get('accept'))

      my_headers.append('accept', e.request.headers.get('accept'));

    if (e.request.headers.get('range'))

    my_headers.append('range', e.request.headers.get('range'));

    // Add &ACAOrigin to allow CORS.

    cross_origin_url += '&ACAOrigin=' + get_host_info().HTTPS_ORIGIN;

    // Add &ACAHeaders to allow range requests.

    cross_origin_url += '&ACAHeaders=accept,range';

    // Make the CORS request.

    const init = { mode: 'cors', headers: my_headers };

    const cross_origin_request = new Request(cross_origin_url, init);

    e.respondWith(fetch(cross_origin_request));

});