hackerCD - intercept canvas calls

tiktok.js

function wrapObject(fn, that, args, name) {
	const instance = fn.apply(that, args);
	instance.__base = instance;
	return new Proxy(instance, {
		get: (target, key) => {
			if(!['__base'].includes(key)) console.log(`[GET] ${name}.${key}`);
			const value = target[key];
			return value;
		},
		set: (target, key, value) => {
			console.log(`${name}.${key} = ${value}`);
			return target[key] = value;
		},
	});
}
function createHandler(fn, name) {
	const handler = {
		apply: (target, that, args) => {
			if(that.__base) that = that.__base;
			if (name === 'getContext') {
					console.log(name, 'apply', args);
					if (args[0] === 'webgl') return wrapObject(fn, that, args, 'WebGLRenderingContext');			
					if (args[0] === '2d') return wrapObject(fn, that, args, 'CanvasRenderingContext2D');
			}
			const res = fn.apply(that, args);
			console.log(`${that.constructor.name}.${name}()`, args, res);
			return res;
		},
	};
	return new Proxy(fn, handler);
}
function wrapProto(obj) {
	for(const key of Object.keys(obj.prototype).filter(x => {try { return typeof obj.prototype[x] === 'function'; } catch { return false; }})) {
		obj.prototype[key] = createHandler(obj.prototype[key], key);
	}
}
wrapProto(HTMLCanvasElement);
wrapProto(CanvasRenderingContext2D);
wrapProto(WebGLRenderingContext);