Refactor security preferences module

src/models/nsa-policy.js

+/**
+ * NSA Policy model.
+ */
+class NsaPolicy {
+
+    /**
+     * Creates an NSA Policy.
+     */
+    constructor () {
+
+        this.UNTRUSTED = {};
+
+        this.TRUSTED = {
+
+            'js': true,
+            'webgl': true,
+            'java': true,
+            'flash': true,
+            'silverlight': true,
+            'plugin': true,
+            'media': true,
+            'frame': true,
+            'font': true
+        };
+
+        this.DEFAULT = {
+            'frame': true
+        };
+
+        this['mozilla.org'] = 1;
+        this['mozilla.com'] = 1;
+        this['mozilla.net'] = 1;
+        this['google.com'] = 1;
+        this['gstatic.com'] = 1;
+        this['googleapis.com'] = 1;
+        this['yahoo.com'] = 1;
+        this['yimg.com'] = 1;
+        this['yahooapis.com'] = 1;
+        this['hotmail.com'] = 1;
+        this['live.com'] = 1;
+        this['wlxrs.com'] = 1;
+        this['securecode.com'] = 1;
+        this['recaptcha.net'] = 1;
+        this['noscript.net'] = 1;
+        this['flashgot.net'] = 1;
+        this['informaction.com'] = 1;
+        this['youtube.com'] = 1;
+        this['ytimg.com'] = 1;
+    }
+};
+
+exports.NsaPolicy = NsaPolicy;

src/modules/security-preferences.js

@@ -13,6 +13,13 @@
  */
 var sdkPreferences = require('sdk/preferences/service');
 
+/**
+ * The NSA policy model.
+ *
+ * @var {NsaPolicy} NsaPolicy
+ */
+var { NsaPolicy } = require('../models/nsa-policy');
+
 /**
  * Contains generic utility functions.
  *
@@ -20,6 +27,13 @@ var sdkPreferences = require('sdk/preferences/service');
  */
 var utilities = require('./utilities.js');
 
+/**
+ * Indicates whether or not this module has been initialized.
+ *
+ * @var {boolean} initialized
+ */
+var initialized = false;
+
 /**
  * Bindings between preferences and slider levels.
  *
@@ -38,141 +52,221 @@ var preferenceBindings = {
     'svg.in-content.enabled':                  [true,     true,   false]
 };
 
-// The Security Settings prefs in question.
-const kSliderPref = 'extensions.tor-browser-settings@torproject.org.security_level';
-const kCustomPref = 'extensions.tor-browser-settings@torproject.org.security_custom';
-const nsaPolicyPref = 'extensions.nsa.policy';
-
-const nsaStandard = {
-  'js': true,
-  'webgl': true,
-  'java': true,
-  'flash': true,
-  'silverlight': true,
-  'plugin': true,
-  'media': true,
-  'frame': true,
-  'font': true
+/**
+ * Bindings between NSA policy rules and slider levels.
+ *
+ * @var {Object} nsaPolicyBindings
+ */
+var nsaPolicyBindings = {
+
+    // NSA policy rule name                    Standard   Safer   Safest
+
+    'js':                                      [true,     false,  false],
+    'webgl':                                   [true,     false,  false],
+    'java':                                    [true,     false,  false],
+    'flash':                                   [true,     false,  false],
+    'silverlight':                             [true,     false,  false],
+    'plugin':                                  [true,     false,  false],
+    'media':                                   [true,     false,  false],
+    'frame':                                   [true,     false,  false],
+    'font':                                    [true,     false,  false]
 };
 
-const nsaSafest = {
-  'js': false,
-  'webgl': false,
-  'java': false,
-  'flash': false,
-  'silverlight': false,
-  'plugin': false,
-  'media': false,
-  'frame': false,
-  'font': false
+/**
+ * The NoScript Anywhere policy preference domain.
+ *
+ * @constant NSA_POLICY_DOMAIN
+ * @type {string}
+ */
+const NSA_POLICY_DOMAIN = 'extensions.nsa.policy';
+
+/**
+ * The custom security settings preference domain.
+ *
+ * @constant SECURITY_CUSTOM_DOMAIN
+ * @type {string}
+ */
+const SECURITY_CUSTOM_DOMAIN = 'extensions.tor-browser-settings@torproject.org.security_custom';
+
+/**
+ * The security level preference domain.
+ *
+ * @constant SECURITY_LEVEL_DOMAIN
+ * @type {string}
+ */
+const SECURITY_LEVEL_DOMAIN = 'extensions.tor-browser-settings@torproject.org.security_level';
+
+/**
+ * Generates a NoScript Anywhere policy string.
+ *
+ * @returns {string} NSA policy string
+ * @private
+ */
+function generateNsaPolicyString () {
+
+    let securityLevel, nsaPolicyString, nsaPolicy;
+
+    securityLevel = sdkPreferences.get(SECURITY_LEVEL_DOMAIN);
+    nsaPolicyString = sdkPreferences.get(NSA_POLICY_DOMAIN);
+
+    try {
+        nsaPolicy = JSON.parse(nsaPolicyString);
+    } catch (exception) {
+        nsaPolicy = new NsaPolicy();
+    }
+
+    nsaPolicy.UNTRUSTED = generateNsaRuleset('UNTRUSTED', securityLevel);
+    nsaPolicy.TRUSTED = generateNsaRuleset('TRUSTED', securityLevel);
+    nsaPolicy.DEFAULT = generateNsaRuleset('DEFAULT', securityLevel);
+
+    return JSON.stringify(nsaPolicy);
 };
 
-// ### Prefs
-
-var generate_nsa_policy = function () {
-  let currentNsaPolicy = sdkPreferences.get(nsaPolicyPref) || '{"UNTRUSTED":{},"TRUSTED":{"js":true,"webgl":true,"java":true,"flash":true,"silverlight":true,"plugin":true,"media":true,"frame":true,"font":true},"DEFAULT":{"frame":true},"mozilla.org":1,"mozilla.com":1,"mozilla.net":1,"google.com":1,"gstatic.com":1,"googleapis.com":1,"yahoo.com":1,"yimg.com":1,"yahooapis.com":1,"hotmail.com":1,"live.com":1,"wlxrs.com":1,"securecode.com":1,"recaptcha.net":1,"noscript.net":1,"flashgot.net":1,"informaction.com":1,"youtube.com":1,"ytimg.com":1}';
-  let securitySliderValue = sdkPreferences.get(kSliderPref);
-  currentNsaPolicy = JSON.parse(currentNsaPolicy);
-  currentNsaPolicy.UNTRUSTED = {};
-  if (securitySliderValue === 0 || securitySliderValue === '0') {
-    currentNsaPolicy.TRUSTED = nsaStandard;
-    currentNsaPolicy.DEFAULT = nsaStandard;
-  } else {
-    currentNsaPolicy.TRUSTED = nsaSafest;
-    currentNsaPolicy.DEFAULT = nsaSafest;
-  }
-  return JSON.stringify(currentNsaPolicy);
+/**
+ * Generates a NoScript Anywhere ruleset.
+ *
+ * @returns {Object} NSA ruleset
+ * @private
+ */
+function generateNsaRuleset (nsaRulesetName, securityLevel) {
+
+    let nsaRuleset  = {};
+
+    if (nsaRulesetName === 'TRUSTED' || nsaRulesetName === 'DEFAULT') {
+
+        let nsaRuleNames = Object.keys(nsaPolicyBindings);
+
+        nsaRuleNames.forEach(function (nsaRuleName) {
+            nsaRuleset[nsaRuleName] = nsaPolicyBindings[nsaRuleName][securityLevel];
+        });
+    }
+
+    return nsaRuleset;
 };
 
-// __write_setting_to_prefs(settingIndex)__.
-// Take a given setting index and write the appropriate pref values
-// to the pref database.
-var write_setting_to_prefs = function (settingIndex) {
-  Object.keys(preferenceBindings).forEach(
-    prefName => sdkPreferences.set(
-      prefName, preferenceBindings[prefName][settingIndex]));
+/**
+ * Applies preference bindings for a given security level.
+ *
+ * @param {number} securityLevel
+ * @private
+ */
+function applyPreferenceBindings (securityLevel) {
+
+    let preferenceNames = Object.keys(preferenceBindings);
+
+    preferenceNames.forEach(function (preferenceName) {
+
+        let preferenceValue = preferenceBindings[preferenceName][securityLevel];
+        sdkPreferences.set(preferenceName, preferenceValue);
+    });
 };
 
-// __read_setting_from_prefs()__.
-// Read the current pref values, and decide if any of our
-// security settings matches. Otherwise return null.
-var read_setting_from_prefs = function () {
-  let prefNames = Object.keys(preferenceBindings);
-  for (let settingIndex of [0, 1, 2]) {
-    let possibleSetting = true;
-    // For the given settingIndex, check if all current pref values
-    // match the setting.
-    for (let prefName of prefNames) {
-      if (preferenceBindings[prefName][settingIndex] !==
-          sdkPreferences.get(prefName)) {
-        possibleSetting = false;
-      }
-    }
-    if (possibleSetting) {
-      // We have a match!
-      return settingIndex;
+/**
+ * Attempts to determine the current security level.
+ *
+ * @returns {number|null} Security level or null
+ * @private
+ */
+function determineCurrentSecurityLevel () {
+
+    let preferenceNames = Object.keys(preferenceBindings);
+
+    for (let securityLevel of [0, 1, 2]) {
+
+        let perfectMatch = true;
+
+        for (let preferenceName of preferenceNames) {
+
+            let expectedValue, actualValue;
+
+            expectedValue = preferenceBindings[preferenceName][securityLevel];
+            actualValue = sdkPreferences.get(preferenceName);
+
+            if (expectedValue !== actualValue) {
+
+                perfectMatch = false;
+                break;
+            }
+        }
+
+        if (perfectMatch === true) {
+            return securityLevel;
+        }
     }
-  }
-  // No matching setting; return null.
-  return null;
+
+    return null;
 };
 
-// __watch_security_prefs(onSettingChanged)__.
-// Whenever a pref bound to the security slider changes, onSettingChanged
-// is called with the new security setting value (0,1,2 or null).
-// Returns a zero-arg function that ends this binding.
-var watch_security_prefs = function (onSettingChanged) {
-  let prefNames = Object.keys(preferenceBindings);
-  let unbindFuncs = [];
-  for (let prefName of prefNames) {
-      unbindFuncs.push(utilities.bindChangeHandlerToPreference(prefName, () => onSettingChanged(read_setting_from_prefs()), true));
-  }
-  // Call all the unbind functions.
-  return () => unbindFuncs.forEach(unbind => unbind());
+/**
+ * Adds change observers to browser preferences.
+ *
+ * @returns {function} Observer unbinder
+ * @private
+ */
+function addObserversToPreferences (handler) {
+
+    let preferenceNames, unbindFunctions;
+
+    preferenceNames = Object.keys(preferenceBindings);
+    unbindFunctions = [];
+
+    for (let preferenceName of preferenceNames) {
+
+        let unbindObserver = utilities.addObserverToPreference(preferenceName, function () {
+
+            let currentSecurityLevel = determineCurrentSecurityLevel();
+            return handler(currentSecurityLevel);
+
+        }, true);
+
+        unbindFunctions.push(unbindObserver);
+    }
+
+    // Can be invoked to unbind all previously registered observers.
+    return () => unbindFunctions.forEach(unbind => unbind());
 };
 
-// __initialized__.
-// Have we called initialize() yet?
-var initialized = false;
+/**
+ * Defines the behavior of the various preference bindings.
+ */
+exports.initialize = function () {
+
+    if (initialized === true) {
+        return;
+    }
 
-// __initialize()__.
-// Defines the behavior of "extensions.torbutton.security_custom",
-// "extensions.torbutton.security_slider", and the security-sensitive
-// prefs declared in preferenceBindings.
-var initialize = function () {
-  // Only run once.
-  if (initialized) {
-    return;
-  }
-  initialized = true;
-  sdkPreferences.set(nsaPolicyPref, generate_nsa_policy());
-  // When security_custom is set to false, apply security_slider setting
-  // to the security-sensitive prefs.
-    utilities.bindChangeHandlerToPreference(kCustomPref, function (custom) {
-
-        if (custom === false) {
-            write_setting_to_prefs(sdkPreferences.get(kSliderPref));
+    // Signal module initialization.
+    initialized = true;
+
+    // Observer for the custom security level preference.
+    utilities.addObserverToPreference(SECURITY_CUSTOM_DOMAIN, function (customized) {
+
+        if (customized === false) {
+
+            let securityLevel = sdkPreferences.get(SECURITY_LEVEL_DOMAIN);
+
+            sdkPreferences.set(NSA_POLICY_DOMAIN, generateNsaPolicyString());
+            applyPreferenceBindings(securityLevel);
         }
 
     }, true);
-  // If security_slider is given a new value, then security_custom should
-  // be set to false.
-    utilities.bindChangeHandlerToPreference(kSliderPref, function (prefIndex) {
-    sdkPreferences.set(kCustomPref, false);
-    sdkPreferences.set(nsaPolicyPref, generate_nsa_policy());
-    write_setting_to_prefs(prefIndex);
-  });
-  // If a security-sensitive pref changes, then decide if the set of pref values
-  // constitutes a security_slider setting or a custom value.
-  watch_security_prefs(settingIndex => {
-    if (settingIndex === null) {
-      sdkPreferences.set(kCustomPref, true);
-    } else {
-      sdkPreferences.set(kSliderPref, settingIndex);
-      sdkPreferences.set(kCustomPref, false);
-    }
-  });
-};
 
-// Export initialize() function for external use.
-exports.initialize = initialize;
+    // Observer for the security level preference.
+    utilities.addObserverToPreference(SECURITY_LEVEL_DOMAIN, function (securityLevel) {
+
+        sdkPreferences.set(SECURITY_CUSTOM_DOMAIN, false);
+        sdkPreferences.set(NSA_POLICY_DOMAIN, generateNsaPolicyString());
+        applyPreferenceBindings(securityLevel);
+    });
+
+    // Adds observers to related browser preferences.
+    addObserversToPreferences(function (securityLevel) {
+
+        if (securityLevel === null) {
+            sdkPreferences.set(SECURITY_CUSTOM_DOMAIN, true);
+        } else {
+            sdkPreferences.set(SECURITY_LEVEL_DOMAIN, securityLevel);
+            sdkPreferences.set(SECURITY_CUSTOM_DOMAIN, false);
+        }
+    });
+};

src/modules/utilities.js

@@ -30,7 +30,7 @@ var sdkPreferences = require('sdk/preferences/service');
 /**
  * Bind a change handler to a specific preference domain.
  */
-exports.bindChangeHandlerToPreference = function (domain, handler, initialize = false) {
+exports.addObserverToPreference = function (domain, handler, initialize = false) {
 
     let updatePreference, observer;