51 lines
2.5 KiB
JavaScript
51 lines
2.5 KiB
JavaScript
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// Self-destructing service worker, served ONLY at https://www.securebit.chat/sw.js.
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//
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// www.securebit.chat answered TLS for the first time when its Fly certificate was
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// issued, and for the couple of minutes before the redirect below shipped it served
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// the real app. That was long enough for visitors to register the site's service
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// worker against the www origin. A registered worker outlives the server change: it
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// keeps serving its cached app shell, so the 301 is never reached, while every
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// subresource request does reach the network, gets redirected to the apex, and is
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// then refused by the page's own CSP (`script-src 'self'` — and 'self' is www).
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//
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// The redirect cannot clear this on its own. A service worker script is re-fetched
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// to check for updates, and the spec fails that update if the script URL redirects
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// at all, let alone cross-origin — so a plain 301 on /sw.js pins the stale worker in
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// place permanently. The only way out is to answer /sw.js with a real script that
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// takes over and then removes itself.
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//
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// It is served with no-store, so browsers re-check it on every navigation rather
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// than trusting a cached copy for 24 hours.
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self.addEventListener('install', () => {
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// Do not wait for the old worker's clients to go away — they are exactly the
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// broken tabs this exists to rescue.
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self.skipWaiting();
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});
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self.addEventListener('activate', (event) => {
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event.waitUntil((async () => {
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// Drop the app shell the previous worker cached under this origin, so nothing
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// can be replayed from it if the unregister below is interrupted.
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const names = await caches.keys();
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await Promise.all(names.map((name) => caches.delete(name)));
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await self.registration.unregister();
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// Reload whatever is still open. With no worker left, the navigation reaches
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// nginx and follows the 301 to the apex, where the app actually lives.
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const clients = await self.clients.matchAll({ type: 'window' });
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for (const client of clients) {
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try {
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await client.navigate(client.url);
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} catch (_) {
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// A client that refuses to be navigated (cross-origin owner, or already
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// gone) is not worth failing activation over; its next reload is clean.
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}
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}
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})());
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});
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// Deliberately no fetch handler: until the unregister lands, requests should go
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// straight to the network, which is where the redirect is.
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