Plugin loading breaks when resistFingerprinting is enabled

[Luzifer]

Description

When Firefox is hardened against fingerprinting by enabling privacy.resistFingerprinting loading of plugins breaks with an error to the console. This for example breaks language-support-plugins.

Reproduction Steps

• Fetch theiaide/theia:next docker image and start it (:latest shows same behavior)
• Get a recent Firefox
• Access about:config and enable privacy.resistFingerprinting
• Try to load the application
• See error:

root ERROR Failed to load plugins: U</e.prototype.createMeasurement/<@https://***HOST***/bundle.js:8:376112
U</e.prototype.logMeasurement@https://***HOST***/bundle.js:8:376368
U</e.prototype.syncPlugins/</<@https://***HOST***/bundle.js:8:366859
s/</<@https://***HOST***/bundle.js:8:360880
s/<@https://***HOST***/bundle.js:8:360985
a@https://***HOST***/bundle.js:8:359728

OS and Theia version:

• Theia: @theia/core 0.16.0-next.00c1747c
• OS: Archlinux, Firefox 73.0

Diagnostics:

• Firefox Bug 1369303
• Firefox Bug 1511941 (Possible fix)
• Relevant code:

  theia/packages/plugin-ext/src/hosted/browser/hosted-plugin.ts

  Lines 577 to 594 in 00c1747

  	protected createMeasurement(name: string): () => number {
  	const startMarker = `${name}-start`;
  	const endMarker = `${name}-end`;
  	performance.clearMeasures(name);
  	performance.clearMarks(startMarker);
  	performance.clearMarks(endMarker);
  	performance.mark(startMarker);
  	return () => {
  	performance.mark(endMarker);
  	performance.measure(name, startMarker, endMarker);
  	const duration = performance.getEntriesByName(name)[0].duration;
  	performance.clearMeasures(name);
  	performance.clearMarks(startMarker);
  	performance.clearMarks(endMarker);
  	return duration;
  	};
  	}

• Failing code:

  theia/packages/plugin-ext/src/hosted/browser/hosted-plugin.ts

  Line 588 in 00c1747

  const duration = performance.getEntriesByName(name)[0].duration;

Example (tested in dev-console):

21:27:49.736 performance.mark('foo-start')
21:27:49.756 undefined
21:28:08.117 performance.mark('foo-end')
21:28:08.178 undefined
21:28:32.134 performance.measure('foo-name', 'foo-start', 'foo-end')
21:28:32.152 undefined
21:28:42.935 performance.getEntriesByName('foo-name')
21:28:42.982 Array []
21:28:46.752 performance.getEntriesByName('foo-name')[0]
21:28:46.763 undefined
21:28:51.444 performance.getEntriesByName('foo-name')[0].duration
21:28:51.487 TypeError: performance.getEntriesByName(...)[0] is undefined

refs / obsoletes theia-ide/theia-apps#306

[akosyakov]

I wonder what their recommendation to use instead of performance API in such case. As far as I know that it is the standardised API and expected to work in all browsers.

[Luzifer]

@akosyakov the API itself works. It just does not return performance data. While in core there is an iteration through the returned array which in that case would be an iteration over Array[] in this code the first element is just accessed.

Firefox does not return any elements when resistFingerprinting is enabled and therefore a length check is required in before accessing the duration of the first element.