feat: make desktopCapturer main-process-only

[nornagon]

Description of Change

This makes desktopCapturer.getSources a main-process-only method.

This is a security precaution; it prohibits renderers from being able to
request images from the desktop without explicit permission from the main
process.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: desktopCapturer.getSources is now only available in the main process.

[MarshallOfSound]

Breaking changes document needs to be updated.
And this needs to be deprecated first rught?

[nornagon]

@MarshallOfSound yep, i thought i'd open this first instead of an issue, to gauge a response before going through the longer process of deprecation/etc.

are you on board with removing this, ultimately?

[MarshallOfSound]

are you on board with removing this, ultimately?

Yes 👍 It's just a convenience IPC wrapper at the moment that is trivial to implement but is currently non trivial to intercept and protect against abuse. removing makes sense.

[miniak]

we should merge lib/browser/api/desktop-capturer.ts with lib/browser/desktop-capturer.ts

[miniak]

@MarshallOfSound

It's just a convenience IPC wrapper at the moment that is trivial to implement

that's not entirely true, it depends on

electron/lib/common/type-utils.ts

Lines 39 to 110 in f9c6f9a

	function serializeNativeImage (image: Electron.NativeImage) {
	const representations = [];
	const scaleFactors = image.getScaleFactors();
	// Use Buffer when there's only one representation for better perf.
	// This avoids compressing to/from PNG where it's not necessary to
	// ensure uniqueness of dataURLs (since there's only one).
	if (scaleFactors.length === 1) {
	const scaleFactor = scaleFactors[0];
	const size = image.getSize(scaleFactor);
	const buffer = image.toBitmap({ scaleFactor });
	representations.push({ scaleFactor, size, buffer });
	} else {
	// Construct from dataURLs to ensure that they are not lost in creation.
	for (const scaleFactor of scaleFactors) {
	const size = image.getSize(scaleFactor);
	const dataURL = image.toDataURL({ scaleFactor });
	representations.push({ scaleFactor, size, dataURL });
	}
	}
	return { __ELECTRON_SERIALIZED_NativeImage__: true, representations };
	}
	function deserializeNativeImage (value: any, createNativeImage: typeof Electron.nativeImage['createEmpty']) {
	const image = createNativeImage();
	// Use Buffer when there's only one representation for better perf.
	// This avoids compressing to/from PNG where it's not necessary to
	// ensure uniqueness of dataURLs (since there's only one).
	if (value.representations.length === 1) {
	const { buffer, size, scaleFactor } = value.representations[0];
	const { width, height } = size;
	image.addRepresentation({ buffer, scaleFactor, width, height });
	} else {
	// Construct from dataURLs to ensure that they are not lost in creation.
	for (const rep of value.representations) {
	const { dataURL, size, scaleFactor } = rep;
	const { width, height } = size;
	image.addRepresentation({ dataURL, scaleFactor, width, height });
	}
	}
	return image;
	}
	export function serialize (value: any): any {
	if (value && value.constructor && value.constructor.name === 'NativeImage') {
	return serializeNativeImage(value);
	} if (Array.isArray(value)) {
	return value.map(serialize);
	} else if (isSerializableObject(value)) {
	return value;
	} else if (value instanceof Object) {
	return objectMap(value, serialize);
	} else {
	return value;
	}
	}
	export function deserialize (value: any, createNativeImage: typeof Electron.nativeImage['createEmpty'] = getCreateNativeImage()): any {
	if (value && value.__ELECTRON_SERIALIZED_NativeImage__) {
	return deserializeNativeImage(value, createNativeImage);
	} else if (Array.isArray(value)) {
	return value.map(value => deserialize(value, createNativeImage));
	} else if (isSerializableObject(value)) {
	return value;
	} else if (value instanceof Object) {
	return objectMap(value, value => deserialize(value, createNativeImage));
	} else {
	return value;
	}
	}

but is currently non trivial to intercept

https://github.com/electron/electron/blob/main/docs/api/web-contents.md#event-desktop-capturer-get-sources
https://github.com/electron/electron/blob/main/docs/api/app.md#event-desktop-capturer-get-sources

[nornagon]

@miniak see #30729

[nornagon]

draft until 16.x forks

[miniak]

@nornagon also remove --enable-api-filtering-logging from docs/api/command-line-switches.md
and kEnableApiFilteringLogging from shell/common/options_switches.h, etc.

[miniak]

@nornagon 16-x-y was branched off, we can land this now in main

[zcbenz]

nornagon is off until next year, so we should either pick this up, or wait for some time.

[miniak]

@zcbenz taking it over. rebased and conflicts resolved

[release-clerk]

Release Notes Persisted

desktopCapturer.getSources is now only available in the main process.