Make third partiness computation much faster

Based on the method used in Privacy Badger Chrome.
Also changes from using hosts (which include port) to hostnames.
Fix #696

Auditors: @bbondy

app/filtering.js

@@ -11,7 +11,7 @@ const BrowserWindow = electron.BrowserWindow
 const AppStore = require('../js/stores/appStore')
 const AppConfig = require('../js/constants/appConfig')
 const urlParse = require('url').parse
-const psl = require('psl')
+const getBaseDomain = require('../js/lib/baseDomain').getBaseDomain
 
 const filteringFns = []
 
@@ -46,8 +46,8 @@ function registerForSession (session) {
 
     let requestHeaders = details.requestHeaders
     if (module.exports.isResourceEnabled(AppConfig.resourceNames.COOKIEBLOCK) &&
-        module.exports.isThirdPartyHost(urlParse(details.firstPartyUrl || '').host,
-                                        urlParse(details.url || '').host)) {
+        module.exports.isThirdPartyHost(urlParse(details.firstPartyUrl || '').hostname,
+                                        urlParse(details.url || '').hostname)) {
       // Clear cookie and referer on third-party requests
       if (requestHeaders['Cookie']) {
         requestHeaders['Cookie'] = undefined
@@ -73,12 +73,16 @@ function registerForSession (session) {
 }
 
 module.exports.isThirdPartyHost = (baseContextHost, testHost) => {
+  // TODO: Always return true if these are IP addresses that aren't the same
   if (!testHost || !baseContextHost) {
     return true
   }
-  const testSuffix = psl.parse(testHost).domain
-  const baseContextSuffix = psl.parse(baseContextHost).domain
-  return testSuffix !== baseContextSuffix || !testSuffix || !baseContextSuffix
+  const documentDomain = getBaseDomain(baseContextHost)
+  if (testHost.length > documentDomain.length) {
+    return (testHost.substr(testHost.length - documentDomain.length - 1) !== '.' + documentDomain)
+  } else {
+    return (testHost !== documentDomain)
+  }
 }
 
 module.exports.init = () => {

app/trackingProtection.js

@@ -28,7 +28,7 @@ const startTrackingProtection = (wnd) => {
       cachedFirstParty = {}
     }
     const firstPartyUrl = URL.parse(details.firstPartyUrl)
-    let firstPartyUrlHost = firstPartyUrl.host || ''
+    let firstPartyUrlHost = firstPartyUrl.hostname || ''
     if (firstPartyUrlHost.startsWith('www.')) {
       firstPartyUrlHost = firstPartyUrlHost.substring(4)
     }
@@ -40,7 +40,7 @@ const startTrackingProtection = (wnd) => {
         ++cachedFirstPartyCount
       }
     }
-    const urlHost = URL.parse(details.url).host
+    const urlHost = URL.parse(details.url).hostname
     const shouldBlock = firstPartyUrl.protocol &&
       details.resourceType !== 'mainFrame' &&
       firstPartyUrl.protocol.startsWith('http') &&

js/lib/baseDomain.js

@@ -0,0 +1,48 @@
+/* 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/. */
+
+const punycode = require('punycode')
+const publicSuffixes = require('./psl')
+
+/**
+ * Returns base domain for specified host based on Public Suffix List.
+ * @param {string} hostname The name of the host to get the base domain for
+ */
+module.exports.getBaseDomain = function (hostname) {
+  // decode punycode if exists
+  if (hostname.indexOf('xn--') >= 0) {
+    hostname = punycode.toUnicode(hostname)
+  }
+
+  // search through PSL
+  var prevDomains = []
+  var curDomain = hostname
+  var nextDot = curDomain.indexOf('.')
+  var tld = 0
+  var suffix
+
+  while (true) {
+    suffix = publicSuffixes[curDomain]
+    if (typeof suffix !== 'undefined') {
+      tld = suffix
+      break
+    }
+
+    if (nextDot < 0) {
+      tld = 1
+      break
+    }
+
+    prevDomains.push(curDomain.substring(0, nextDot))
+    curDomain = curDomain.substring(nextDot + 1)
+    nextDot = curDomain.indexOf('.')
+  }
+
+  while (tld > 0 && prevDomains.length > 0) {
+    curDomain = prevDomains.pop() + '.' + curDomain
+    tld--
+  }
+
+  return curDomain
+}