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feat: add option to enable cross-origin isolation #234

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feat: add option to enable cross-origin isolation #234

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e01f5d9
fix: enable cross-origin isolation
nolanlawson Apr 25, 2022
87e319f
Merge remote-tracking branch 'origin/main' into cross-origin-isolation
nolanlawson Aug 4, 2024
3cd4426
fix: add header and cli option
nolanlawson Aug 4, 2024
0aee155
fix: actually expose the cli option
nolanlawson Aug 4, 2024
0b7e643
docs: update changelog
nolanlawson Aug 5, 2024
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12 changes: 12 additions & 0 deletions src/cross-origin-isolation.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
import {Middleware} from 'koa';
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// Enable cross-origin isolation for more precise timers:
// https://developer.chrome.com/blog/cross-origin-isolated-hr-timers/
export function crossOriginIsolation(): Middleware {
// Based on https://github.com/fishel-feng/koa-isolated
return async function isolated(ctx, next) {
ctx.set('Cross-Origin-Opener-Policy', 'same-origin');
ctx.set('Cross-Origin-Embedder-Policy', 'require-corp');
await next();
};
}
2 changes: 2 additions & 0 deletions src/server.ts
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Expand Up @@ -19,6 +19,7 @@ import {nodeResolve} from 'koa-node-resolve';

import {BenchmarkResponse, Deferred} from './types.js';
import {NpmInstall} from './versions.js';
import {crossOriginIsolation} from './cross-origin-isolation';

import * as url from 'url';
const __dirname = url.fileURLToPath(new URL('.', import.meta.url));
Expand Down Expand Up @@ -91,6 +92,7 @@ export class Server {
this.server = server;
const app = new Koa();

app.use(crossOriginIsolation());
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@AndrewJakubowicz AndrewJakubowicz Aug 4, 2024 •
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Is there a chance this change could be breaking in the case where someone is explicitly measuring something where external resources are requested?

In this case, may it be worth putting this change behind a ServerOpts option, where the default is the current behavior (not cross origin isolated), but the headers can be opted in?

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Good point! I totally didn't think of that. 😅

I think making this disabled by default sort of defeats the purpose of improving the timing accuracy, but I also admit I don't have any evidence that CORP/COEP actually does this (maybe the browser treats localhost differently? not sure). That said, having the option at least unblocks SharedArrayBuffer and friends.

So sure thing: I added a CLI option, --cross-origin-isolated, which is disabled by default. I think further experimentation would be needed to see if it has any effect on timing accuracy. 🙂

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I think the benefits of having it (even if behind a flag):

  • Safe roll-out of the option. Making it a non-breaking change.
  • The timers should be more accurate when cross origin isolated is enabled.
  • And we could still add the SharedArrayBuffer (and friends) features. They would just have to check the crossOriginIsolated property.

I'm a fan of this change!

app.use(bodyParser());
app.use(mount('/submitResults', this.submitResults.bind(this)));
app.use(this.instrumentRequests.bind(this));
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10 changes: 10 additions & 0 deletions src/test/server_test.ts
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Thank you for adding tests!

Original file line number Diff line number Diff line change
Expand Up @@ -137,4 +137,14 @@ suite('server', () => {
session = server.endSession();
assert.equal(session.bytesSent, 0);
});

test('enables cross-origin isolation', async () => {
const res = await fetch(`${server.url}/import-bare-module.html`);

assert.equal(res.headers.get('Cross-Origin-Opener-Policy'), 'same-origin');
assert.equal(
res.headers.get('Cross-Origin-Embedder-Policy'),
'require-corp'
);
});
});