Remove all web_accessible_resources, inject page code with Blob urls.

src/js/constants.js

@@ -55,7 +55,11 @@ const FINGERPRINTING = 'fingerprinting',
   BLOCK = 'block',
   HEADER_DEACTIVATE_ON_HOST = 'header_deactivate_on_host';
 
-const FINGERPRINTING_PATH = '/js/contentscripts/injector.js';
+const CONTENTSCRIPTS = new Set([
+  '/js/bootstrap.js',
+  '/js/contentscripts/fingercounting.js',
+  '/js/initialize_contentscripts.js',
+]);
 
 const etag = {
   ETAG_TRACKING: 'etag_tracking',
@@ -87,7 +91,7 @@ Object.assign(exports, {
   request_methods,
   header_methods,
   FINGERPRINTING,
-  FINGERPRINTING_PATH,
+  CONTENTSCRIPTS,
   USER_HOST_DEACTIVATE,
   USER_URL_DEACTIVATE,
   BLOCK,

src/js/contentscripts/fingercounting.js

@@ -0,0 +1,272 @@
+"use strict";
+
+[(function(exports) {
+/**
+ * This watches methods that are commonly used for fingerprinting, and reports
+ * when a suspicious number of them are used by one script.
+ *
+ * We watch the methods by adding some accounting code to their getters, see `wrapMethod`.
+ *
+ * In the accounting code we track the usage *per script*. We determine which
+ * script is accessing the method by checking the stack, see `getScriptLocation`.
+ */
+
+function makeFingerCounting(event_id = 0, init = true) {
+  // stuff for default config in browser
+  const threshold = 0.60;
+
+  function send(msg) {
+    document.dispatchEvent(new CustomEvent(event_id, {detail: msg}));
+  }
+
+  function listen(func) {
+    document.addEventListener(event_id, func);
+  }
+
+  // gets the location of arguments.callee.caller
+  function getScriptLocation() {  // todo: to do split('\n') we do a O(n) read of the stack, this could be reduced by a constant factor by only reading to the third '\n'. but this is micro optimisation
+    let lines = (new Error()).stack.split('\n');
+    try {
+      try {
+        return getUrlFromStackLine(lines[3]);
+      } catch (e) {
+        return getUrlFromStackLine(lines[2]);
+      }
+    } catch (ee) {
+      return null;
+    }
+  }
+
+  const urlEndRegex = /^.*?.(?=(\?|#|:(?!\/\/)))/,
+    startsWithHttpScheme = /^https?:\/\//;
+
+  function getUrlFromStackLine(line) {
+    while (line.slice(-1) === ')') { // there are parenthese
+      line = line.slice(line.lastIndexOf('(') + 1);
+      line = line.slice(0, line.indexOf(')'));
+    }
+    line = line.split(' ').pop(); // remove stuff up to the url
+    if (!startsWithHttpScheme.test(line) && !line.startsWith('/')) {
+      // in firefox we have to strip func name
+      line = line.slice(line.indexOf('@') + 1);
+    }
+    return line.match(urlEndRegex)[0]; // strip stuff after the path of url (query, hash, and line numbers);
+  }
+
+  function randString() {
+    return Math.random().toString(36).substr(2);
+  }
+
+  function randNumber(min = 0, max = 1) {
+    return (Math.random() * (max - min)) + min;
+  }
+
+  function randInt(min, max) {
+    return Math.floor(randNumber(min, max));
+  }
+
+  function randArr(min, max, filler) {
+    return () => {
+      let size = randInt(min, max)
+      return Array.from(new Array(size), filler);
+    }
+  }
+
+  let randoThing = {
+    [Symbol.toPrimitive](hint) {
+      if (hint === 'number') {
+        return randInt(0, 10);
+      }
+      if (hint === 'string') {
+        return randString();
+      }
+      return true;
+    }
+  }
+
+  function trap() {
+    let target = () => {},
+      lol = (target, property) => {
+        if (typeof property === 'symbol' && property === Symbol.toPrimitive) {
+          return randoThing[property];
+        }
+        return new Proxy(target, descriptor);
+      },
+      descriptor = {apply: lol, get: lol};
+    return lol(target);
+  }
+
+
+  function noop() {return noop};
+
+  /**
+   * fingerprintjs2 defines the following "keys"
+   *
+   * then some jsFontsKeys and flashFontsKeys
+   *
+   * I'll try to catch each of these
+   */
+  const methods = [
+    //    keys = this.userAgentKey(keys);
+    ['navigator.userAgent', randString],
+    //    keys = this.languageKey(keys);
+    ['navigator.language', randString],
+    //    keys = this.pixelRatioKey(keys);
+    ['window.devicePixelRatio', randNumber.bind(0, 2)],
+    //    keys = this.hasLiedLanguagesKey(keys);
+    ['navigator.languages', randArr(0, 7, randString)],
+    //    keys = this.colorDepthKey(keys);
+    ['screen.colorDepth', randInt.bind(5, 40)],
+    //    keys = this.hardwareConcurrencyKey(keys);
+    ['navigator.hardwareConcurrency', randInt.bind(1, 10)],
+    //    keys = this.cpuClassKey(keys);
+    ['navigator.cpuClass', trap()],
+    //    keys = this.platformKey(keys);
+    ['navigator.platform', randString],
+    //    keys = this.doNotTrackKey(keys);
+    ['navigator.doNotTrack', trap()],
+    //    keys = this.touchSupportKey(keys);
+    ['navigator.maxTouchPoints', randInt.bind(0, 5)],
+
+    //    keys = this.screenResolutionKey(keys);
+    ['screen.width', randInt.bind(500, 3000)],
+    //    keys = this.availableScreenResolutionKey(keys);
+    ['screen.availWidth', randInt.bind(500, 3000)],
+    // these also are counted with:
+    //    keys = this.hasLiedResolutionKey(keys);
+
+    //    keys = this.timezoneOffsetKey(keys);
+    ['Date.prototype.getTimezoneOffset', () => randInt.bind(0, 200)],
+    //    keys = this.sessionStorageKey(keys);
+    ['window.sessionStorage', noop],
+    //    keys = this.localStorageKey(keys);
+    ['window.localStorage', noop],
+    //    keys = this.indexedDbKey(keys);
+    ['window.indexedDB', noop],
+    //    keys = this.openDatabaseKey(keys);
+    ['window.openDatabase', noop],
+    //    keys = this.pluginsKey(keys);
+    ['navigator.plugins', trap()],
+    //    keys = this.canvasKey(keys);
+    ['window.HTMLCanvasElement.prototype.getContext', trap()],
+    //    keys = this.webglKey(keys);
+    ['window.WebGLRenderingContext.prototype.createBuffer', trap()],
+    //    keys = this.adBlockKey(keys);
+    //    keys = this.addBehaviorKey(keys);
+    //    keys = this.hasLiedOsKey(keys);
+    //    keys = this.hasLiedBrowserKey(keys);
+    //    keys = this.customEntropyFunction(keys);
+  ];
+
+  class Counter {
+    constructor({globalObj, methods, getScriptLocation, threshold, send, listen}) {
+      Object.assign(this, {globalObj, methods, getScriptLocation, threshold, send, listen});
+
+      this.locations = {};
+      this.nMethods = methods.length;
+      for (const [name, lieFunc] of methods) {
+        this.wrapMethod(name, lieFunc);
+      }
+
+      this.listen(this.firstpartyFingerprintingListener.bind(this));
+      this.send({type: 'ready'});
+    }
+
+    onFingerprinting(loc) {
+      this.send({type: 'fingerprinting', url: loc});
+    }
+
+    firstpartyFingerprintingListener(e) {
+      let {type, url} = e.detail;
+      if (type === 'firstparty-fingerprinting') {
+        if (!this.locations.hasOwnProperty(url)) {
+          this.locations[url] = this.addLocation();
+        }
+        this.locations[url].isFingerprinting = true;
+      }
+    }
+
+    // wrap a dotted method name with a counter
+    wrapMethod(dottedPropName, lieFunc) {
+      const self = this,
+        arr = dottedPropName.split('.'),
+        propName = arr.pop();
+
+      let baseObj = arr.reduce((o, i) => o[i], this.globalObj);
+      let before = baseObj[propName];
+      try {
+        Object.defineProperty(baseObj, propName, {
+          get: function() {
+            let loc = self.addCall(dottedPropName, self.getScriptLocation());
+            if (loc.isFingerprinting) {
+              return lieFunc(before);
+            }
+            return before;
+          },
+          set: function(value) {
+            return before = value;
+          },
+          configurable: true,
+        });
+      } catch (ignore) {
+        // property probably non-configurable from other userscript
+      }
+    }
+
+    addLocation() {
+      return {isFingerprinting: false, counts: {}, nnzCounts: 0};
+    }
+
+    /*
+     * Keep a running score/nnzCounts. This lets us avoid polling
+     * counter.isFingerprinting.
+     */
+    addCall(prop_name, loc_name) {
+      if (!loc_name) {
+        return;
+      }
+
+      let loc = this.locations[loc_name];
+      if (!loc) {
+        loc = this.locations[loc_name] = this.addLocation();
+      }
+
+      if (!loc.counts.hasOwnProperty(prop_name)) {
+        loc.counts[prop_name] = 0;
+        loc.nnzCounts += 1;
+
+        if ((loc.nnzCounts/this.nMethods) > this.threshold &&
+            (!loc.isFingerprinting)) {
+          loc.isFingerprinting = true;
+          this.onFingerprinting(loc_name);
+        }
+      }
+
+      loc.counts[prop_name] += 1;
+      return loc;
+    }
+  };
+
+  // initialize for browser
+  function initialize() {
+    const config = {
+      globalObj: window,
+      methods,
+      getScriptLocation,
+      threshold,
+      send,
+      listen,
+    };
+
+    return new Counter(config); // eslint-disable-line
+  }
+  if (init) {
+    return initialize();
+  } else {
+    return {Counter, getUrlFromStackLine, initialize};
+  }
+}
+
+Object.assign(exports, {makeFingerCounting});
+
+})].map(func => typeof exports == 'undefined' ? define('/contentscripts/fingercounting', func) : func(exports));

src/js/contentscripts/injector.js → src/js/initialize_contentscripts.js

@@ -1,5 +1,6 @@
 "use strict";
 
+let {makeFingerCounting} = require('./contentscripts/fingercounting');
 let event_id = Math.random();
 
 // listen for messages from the script we are about to insert
@@ -18,18 +19,28 @@ let ready = new Promise(resolve => {
   });
 
   // insert script now that ready listener is listening.
-  let s = document.createElement('script');
-  s.setAttribute('data', event_id);
-  s.src = chrome.extension.getURL('js/web_accessible/fingercounting.js');
-  s.onload = function() {
+  const scriptTag = document.createElement('script'),
+    blob = new Blob([`(${makeFingerCounting.toString()})(${event_id})`], {type: 'text/javascript'}),
+    url = URL.createObjectURL(blob);
+  scriptTag.src = url;
+  scriptTag.onload = function() {
     this.remove();
+    URL.revokeObjectURL(url);
   };
-  (document.head || document.documentElement).appendChild(s);
+  (document.head || document.documentElement).appendChild(scriptTag);
 });
 
+const clean = message => {
+  try {
+    return cloneInto(message, document.defaultView); // eslint-disable-line
+  } catch (unused) {
+    return message;
+  }
+}
 
 chrome.runtime.onMessage.addListener(message => {
   if (message.type === 'firstparty-fingerprinting') {
+    message = clean(message);
     ready.then(() => {
       document.dispatchEvent(new CustomEvent(event_id, {detail: message}));
     });

src/js/tabs.js

@@ -7,12 +7,10 @@
 [(function(exports) {
 
 const shim = require('./shim'), {URL, tabsGet, tabsQuery, tabsExecuteScript} = shim,
-  {REMOVE_ACTION, FINGERPRINTING_PATH} = require('./constants'),
+  {REMOVE_ACTION, CONTENTSCRIPTS} = require('./constants'),
   {errorOccurred, Counter, listenerMixin, setTabIconActive, safeSetBadgeText, log} = require('./utils'),
   {isThirdParty} = require('./domains/parties');
 
-const contentScripts = new Set([FINGERPRINTING_PATH]);
-
 class Resource {
   constructor({url, method, type}) {
     this.url = url;
@@ -210,7 +208,7 @@ class Tabs {
   async onNavigationCommitted({tabId, frameId, url}) {
     const tab = this.getTab(tabId);
     if ((tabId >= 0) && tab && tab.active) {
-      for (let file of contentScripts) {
+      for (let file of CONTENTSCRIPTS) {
         await tabsExecuteScript(tabId, {frameId, runAt: 'document_start', matchAboutBlank: true, file}, () => {
           if (errorOccurred()) {
             log(`cannot inject content script ${file} into url ${url} on tab ${tabId} and frame ${frameId}`);