From 79a9034051e71b47f57a6cb820b64da86732b543 Mon Sep 17 00:00:00 2001
From: kkapsner <github@mail.kkapsner.de>
Date: Fri, 17 May 2019 00:36:34 +0200
Subject: [PATCH] Preventing double interception

---
 lib/frame.js     | 52 +++++++++++++++++++++++++++++++++++++++++++++---
 releaseNotes.txt |  1 +
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/lib/frame.js b/lib/frame.js
index 1282d25..de73007 100644
--- a/lib/frame.js
+++ b/lib/frame.js
@@ -7,7 +7,7 @@
 	const settings = require("./settings");
 	const {preIntercept: intercept} = require("./intercept");
 	const {ask} = require("./askForPermission");
-	const lists = require("./lists");
+	const {sha256String: hashing} = require("./hash");
 	const {check: originalCheck, checkStack: originalCheckStack} = require("./check");
 	const {getWrapped} = require("./modifiedAPIFunctions");
 	const extension = require("./extension");
@@ -44,6 +44,33 @@
 		});
 	}
 	
+	let extensionSecret;
+	function computeExtensionSecret(){
+		function hashString(string){
+			return hashing(new Uint16Array(
+				string.split("").map(function(c){
+					return c.charCodeAt(0);
+				})
+			));
+		}
+		const now = new Date();
+		const lastTenMinutes = Math.floor(now.getMinutes() / 10) * 10;
+		const nextRun = new Date(
+			now.getFullYear(), now.getMonth(), now.getDate(),
+			now.getHours(), lastTenMinutes + 10, 0, 0
+		);
+		window.setTimeout(
+			computeExtensionSecret,
+			nextRun .getTime() - now.getTime()
+		);
+		
+		let string =
+			extension.extensionID +
+			`${now.getFullYear()}-${now.getMonth() + 1}-${now.getDate()} ${now.getHours()}:${lastTenMinutes}`;
+		extensionSecret = [hashString("input" + string), hashString(string + "output")];
+	}
+	computeExtensionSecret();
+	
 	message("open port to background script");
 	var port = browser.runtime.connect();
 	if (window === window.top){
@@ -106,8 +133,13 @@
 			warning("NOT intercepting window due to SOP", window);
 			return false;
 		}
+		const wrappedWindow = getWrapped(window);
 		
-		if (!enabled || interceptedWindows.get(getWrapped(window))){
+		if (!enabled || interceptedWindows.get(wrappedWindow)){
+			return false;
+		}
+		if (wrappedWindow.matchMedia(extensionSecret[0]) === extensionSecret[1]){
+			interceptedWindows.set(wrappedWindow, true);
 			return false;
 		}
 		
@@ -153,7 +185,21 @@
 			);
 		});
 		
-		interceptedWindows.set(getWrapped(window), true);
+		const matchMediaDescriptor = Object.getOwnPropertyDescriptor(wrappedWindow, "matchMedia");
+		const originalMatchMedia = matchMediaDescriptor.value;
+		matchMediaDescriptor.value = exportFunction(function matchMedia(query){
+			if (query === extensionSecret[0]){
+				return extensionSecret[1];
+			}
+			else {
+				return arguments.length > 1?
+					originalMatchMedia.apply(this, wrappedWindow.Array.from(arguments)):
+					originalMatchMedia.call(this, query);
+			}
+		}, window);
+		Object.defineProperty(wrappedWindow, "matchMedia", matchMediaDescriptor);
+		
+		interceptedWindows.set(wrappedWindow, true);
 		return true;
 	}
 	
diff --git a/releaseNotes.txt b/releaseNotes.txt
index 5e07abd..19f80ed 100644
--- a/releaseNotes.txt
+++ b/releaseNotes.txt
@@ -23,6 +23,7 @@ Version 0.5.9:
 		- fixed description for "show notifications"
 		- improved DOMRect performance
 		- improved general performance when stack list is disabled
+		- preventing double interception (increased performance and reduced detectability)
 	
 	known issues:
 		- if a data URL is blocked the page action button does not appear