/** \file
 * \brief Wrappers for Workers
 *
 *  \author Copyright (C) 2019  Libor Polcak
 *  \author Copyright (C) 2020  Peter Hornak
 *  \author Copyright (C) 2021  Matus Svancar
 *
 *  \license SPDX-License-Identifier: GPL-3.0-or-later
 */
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
//

/** \file
 * \ingroup wrappers
 *
 * This wrapper aims on prevention of microarchitectural attacks. This
 * code was originally a part of [ChromeZero](https://github.com/IAIK/ChromeZero).
 *
 * The wrappers support the following behaviour:
 *
 * * Polyfill: Completely eliminates the paralelism.
 * * Randomly slow messages: Add noise to the `postMessage` method execution.
 *
 * \see Lipp, M., Gruss, D., Schwarz, M., Bidner, D., Maurice, C. et al. Practical
Keystroke Timing Attacks in Sandboxed JavaScript. In:. August 2017, s. 191–209.
ISBN 978-3-319-66398-2.
 *
 * \see Schwarz, M., Lipp, M. a Gruss, D. JavaScript Zero: Real JavaScript and Zero
 *      Side-Channel Attacks. NDSS'18.
 *
 * \see <https://www.fit.vut.cz/study/thesis/22374/?year=0&sup=Pol%C4%8D%C3%A1k>
 */



/*
 * Create private namespace
 */
(function() {
	var polyfillBody = `
	/// This polyfill was adopted from https://github.com/nolanlawson/pseudo-worker under Apache License 2.0 and modified.
	function doEval(self, __pseudoworker_script) {
		/* jshint unused:false */
		(function () {
			/* jshint evil:true */
			eval(__pseudoworker_script);
		}).call(window);
	}

	var messageListeners = [];
	var errorListeners = [];
	var workerMessageListeners = [];
	var workerErrorListeners = [];
	var postMessageListeners = [];
	var terminated = false;
	var script;
	var workerSelf;

	var api = this;

	// custom each loop is for IE8 support
	function executeEach(arr, fun) {
		var i = -1;
		while (++i < arr.length) {
			if (arr[i]) {
				fun(arr[i]);
			}
		}
	}

	function callErrorListener(err) {
		return function (listener) {
			listener({
				type: 'error',
				error: err,
				message: err.message
			});
		};
	}

	function addEventListener(type, fun) {
		/* istanbul ignore else */
		if (type === 'message') {
			messageListeners.push(fun);
		} else if (type === 'error') {
			errorListeners.push(fun);
		}
	}

	function removeEventListener(type, fun) {
		var listeners;
		/* istanbul ignore else */
		if (type === 'message') {
			listeners = messageListeners;
		} else if (type === 'error') {
			listeners = errorListeners;
		} else {
			return;
		}
		var i = -1;
		while (++i < listeners.length) {
			var listener = listeners[i];
			if (listener === fun) {
				delete listeners[i];
				break;
			}
		}
	}

	function postError(err) {
		var callFun = callErrorListener(err);
		if (typeof api.onerror === 'function') {
			callFun(api.onerror);
		}
		if (workerSelf && typeof workerSelf.onerror === 'function') {
			callFun(workerSelf.onerror);
		}
		executeEach(errorListeners, callFun);
		executeEach(workerErrorListeners, callFun);
	}

	function runPostMessage(msg, transfer) {
		function callFun(listener) {
			try {
				listener({data: msg, ports: transfer});
			} catch (err) {
				postError(err);
			}
		}

		if (workerSelf && typeof workerSelf.onmessage === 'function') {
			callFun(workerSelf.onmessage);
		}
		executeEach(workerMessageListeners, callFun);
	}

	function postMessage(msg, transfer) {
		if (typeof msg === 'undefined') {
			throw new Error('postMessage() requires an argument');
		}
		if (terminated) {
			return;
		}
		if (!script) {
			postMessageListeners.push({msg: msg, transfer: (transfer ? transfer : undefined)});
			return;
		}
		runPostMessage(msg, transfer);
	}

	function terminate() {
		terminated = true;
	}

	function workerPostMessage(msg) {
		if (terminated) {
			return;
		}

		function callFun(listener) {
			listener({
				data: msg
			});
		}

		if (typeof api.onmessage === 'function') {
			callFun(api.onmessage);
		}
		executeEach(messageListeners, callFun);
	}

	function workerAddEventListener(type, fun) {
		/* istanbul ignore else */
		if (type === 'message') {
			workerMessageListeners.push(fun);
		} else if (type === 'error') {
			workerErrorListeners.push(fun);
		}
	}

	var xhr = new XMLHttpRequest();

	xhr.open('GET', path);
	xhr.onreadystatechange = function () {
		if (xhr.readyState === 4) {
			if (xhr.status >= 200 && xhr.status < 400) {
				script = xhr.responseText;
				workerSelf = {
					postMessage: workerPostMessage,
					addEventListener: workerAddEventListener,
					close: terminate
				};
				doEval(workerSelf, script);
				var currentListeners = postMessageListeners;
				postMessageListeners = [];
				for (var i = 0; i < currentListeners.length; i++) {
					runPostMessage(currentListeners[i].msg, currentListeners[i].transfer);
				}
			} else {
				postError(new Error('cannot find script ' + path));
			}
		}
	};

	xhr.send();

	api.postMessage = postMessage;
	api.addEventListener = addEventListener;
	api.removeEventListener = removeEventListener;
	api.terminate = terminate;

	return api;
	`;

	var slowBody = `
		let _data = new originalF(path);
		let _old = _data.postMessage;
		_data.postMessage = function(message) {
			let delay = Math.floor(Math.random() * 10**9)
			let j;
			for (let i = 0; i < delay;) {
				j = i;
				i = j + 1;
			}
			return _old.call(_data, message);
		}
		return _data;
	`;

	var wrappers = [
		{
			parent_object: "Navigator.prototype",
			parent_object_property: "hardwareConcurrency",
			wrapped_objects: [],
			helping_code: `
				var hw_prng = alea(domainHash, "Navigator.prototype.hardwareConcurrency");
				var ret = 2;
				if(args[0]==0){
					var realValue = navigator.hardwareConcurrency;
					ret = Math.floor(2+hw_prng()*(realValue-2));
				}
				else if(args[0]==1){
					ret = Math.floor(2+(hw_prng()*6));
				}
			`,
			post_wrapping_code: [
				{
					code_type: "object_properties",
					wrapped_name: "origConcurrency",
					wrapped_objects: [],
					parent_object: "Navigator.prototype",
					parent_object_property: "hardwareConcurrency",
					/**  \brief replaces navigator.hardwareConcurrency getter
					 *
					 * Depending on level chosen this property returns:
					 *	* (0) - random valid value from range [2 - real value]
					 *	* (1) - random valid value from range [2 - 8]
					 *	* (2) - 2
					 */
					wrapped_properties: [
						{
							property_name: "get",
							property_value: `
								function() {
									return ret;
								}`,
						},
					],
				}
			],
		},
		{
			parent_object: "window",
			parent_object_property: "Worker",
			original_function: "window.Worker",
			wrapped_objects: [],
			helping_code: `
				let doPolyfill = args[0];
			`,
			wrapping_function_args: `path`,
			wrapping_function_body: `
			if (doPolyfill) {
				${polyfillBody}
			} else {
				${slowBody}
			}
			`,
		}
	]
	add_wrappers(wrappers);
})();