CanvasBlocker/lib/intercept.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
(function(){
	"use strict";
	
	var scope;
	if ((typeof exports) !== "undefined"){
		scope = exports;
	}
	else {
		window.scope.intercept = {};
		scope = window.scope.intercept;
	}
	
	const {changedFunctions, setRandomSupply} = require("./modifiedAPI");
	const randomSupplies = require("./randomSupplies");
	const getWrapped = require("sdk/getWrapped");
	const logging = require("./logging");
	const settings = require("./settings");

	setRandomSupply(randomSupplies.nonPersistent);
	var apiNames = Object.keys(changedFunctions);
	var undef;
	function setRandomSupplyByType(type){
		switch (type){
			case "persistent":
				setRandomSupply(randomSupplies.persistent);
				break;
			case "constant":
				setRandomSupply(randomSupplies.constant);
				break;
			case "white":
				setRandomSupply(randomSupplies.white);
				break;
			default:
				setRandomSupply(randomSupplies.nonPersistent);
		}
	}
	scope.setRandomSupplyByType = setRandomSupplyByType;
	
	function getURL(window){
		var href;
		try {
			href = window.location.href;
		}
		catch (e){
			// unable to read location due to SOP
			// since we are not able to do anything in that case we can allow everything
			return "about:SOP";
		}
		if (!href || href === "about:blank"){
			if (window !== window.parent){
				return getURL(window.parent);
			}
			else if (window.opener){
				return getURL(window.opener);
			}
		}
		return window.location.href;
	}
	
	scope.preIntercept = function preIntercept({subject: window}, apis){
		if (!settings.isStillDefault){
			logging.message("settings already loaded -> no need to pre intercept");
			scope.intercept({subject: window}, apis);
		}
		else  {
			logging.message("settings not loaded -> need to pre intercep");
			let forceLoad = true;
			let preIntercepted = false;
			let intercepted = false;
			const forEachFunction = function(callback){
				apiNames.forEach(function(name){
					const changedFunction = changedFunctions[name];
					(
						Array.isArray(changedFunction.object)?
							changedFunction.object:
							[changedFunction.object]
					).forEach(function(object){
						var constructor = getWrapped(window)[object];
						if (constructor){
							callback({name, changedFunction, constructor});
						}
					});
				});
			};
			let originalPropertyDescriptors = {};
			const doPreIntercept = function(){
				if (!preIntercepted){
					forEachFunction(function({name, constructor}){
						var map = originalPropertyDescriptors[name] || new WeakMap();
						originalPropertyDescriptors[name] = map;
						map.set(constructor, Object.getOwnPropertyDescriptor(constructor.prototype, name));
						Object.defineProperty(
							constructor.prototype,
							name,
							{
								enumerable: true,
								configureable: true,
								get: exportFunction(function(){
									if (forceLoad){
										logging.warning("force load the settings. Calling stack:", (new Error()).stack);
										undoPreIntercept();
										settings.forceLoad();
										doRealIntercept();
										var descriptor = Object.getOwnPropertyDescriptor(constructor.prototype, name);
										return descriptor.value || descriptor.get();
									}
									else {
										logging.notice("API blocked (%s)", name);
										var url = getURL(window);
										if (!url){
											return undef;
										}
										var error = new Error();
										apis.notify({
											url,
											errorStack: error.stack,
											messageId: "preBlock",
											timestamp: new Date(),
											functionName: name,
											dataURL: false
										});
										return;
									}
								}, window),
								set: exportFunction(function(){}, window)
							}
						);
					});
					preIntercepted = true;
				}
			};
			const undoPreIntercept = function(){
				if (preIntercepted){
					preIntercepted = false;
					forEachFunction(function({name, constructor}){
						Object.defineProperty(
							constructor.prototype,
							name,
							originalPropertyDescriptors[name].get(constructor)
						);
					});
				}
			};
			const doRealIntercept = function(){
				if (!intercepted){
					scope.intercept({subject: window}, apis);
					intercepted = true;
				}
			};
			
			doPreIntercept();
			settings.onloaded(function(){
				undoPreIntercept();
				doRealIntercept();
			});
		}
	};

	let extensionID = browser.extension.getURL("");
	scope.intercept = function intercept({subject: window}, {check, checkStack, ask, notify, prefs}){
		var siteStatus = check({url: getURL(window)});
		logging.verbose("status for page", window, siteStatus);
		if (siteStatus.mode !== "allow"){
			apiNames.forEach(function(name){
				var changedFunction = changedFunctions[name];
				var functionStatus = changedFunction.getStatus(undefined, siteStatus);
				logging.verbose("status for", name, ":", functionStatus);
				if (functionStatus.active){
					(
						Array.isArray(changedFunction.object)?
							changedFunction.object:
							[changedFunction.object]
					).forEach(function(object){
						var constructor = getWrapped(window)[object];
						if (constructor){
							var original = constructor.prototype[name];
						
							Object.defineProperty(
								constructor.prototype,
								name,
								{
									enumerable: true,
									configureable: true,
									get: exportFunction(function(){
										var url = getURL(window);
										if (!url){
											return undef;
										}
										var error = new Error();
										try {
											// return original if the extension itself requested the function
											if (error.stack.split("\n", 3)[1].split("@", 2)[1].startsWith(extensionID)){
												return original;
											}
										}
										catch (e) {
											// stack had an unknown form
										}
										if (checkStack(error.stack)){
											return original;
										}
										var funcStatus = changedFunction.getStatus(this, siteStatus);
										
										function notifyCallback(messageId){
											notify({
												url,
												errorStack: error.stack,
												messageId,
												timestamp: new Date(),
												functionName: name,
												dataURL:
													prefs("storeImageForInspection") &&
													prefs("showNotifications")?
														(
															this instanceof HTMLCanvasElement?
																this.toDataURL():
																(
																	this.canvas instanceof HTMLCanvasElement?
																		this.canvas.toDataURL():
																		false
																)
														):
														false
											});
										}
										
										if (funcStatus.active && !prefs("apiWhiteList")[name]){
											if (funcStatus.mode === "ask"){
												funcStatus.mode = ask({
													window: window,
													type: changedFunction.type,
													canvas: this instanceof HTMLCanvasElement?
														this:
														(
															this.canvas instanceof HTMLCanvasElement?
																this.canvas:
																false
														),
													errorStack: error.stack
												});
											}
											switch (funcStatus.mode){
												case "allow":
													return original;
												case "fake":
													setRandomSupplyByType(prefs("rng"));
													var fake = changedFunction.fakeGenerator(
														prefs,
														notifyCallback,
														window,
														original
													);
													switch (fake){
														case true:
															return original;
														case false:
															return undef;
														default:
															return exportFunction(fake, getWrapped(window));
													}
												//case "block":
												default:
													return undef;
											}
										}
										else {
											return original;
										}
									}, window),
									set: exportFunction(function(value){
										Object.defineProperty(
											constructor.prototype,
											name,
											{
												value,
												writable: true,
												configurable: true,
												enumerable: true
											}
										);
									}, window)
								}
							);
						}
					});
				}
			});
		}
	};
}());