path: root/application/basilisk/base/content/sanitize.js

// -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
/* 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/. */

Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
Components.utils.import("resource://gre/modules/Services.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "AppConstants",
                                  "resource://gre/modules/AppConstants.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
                                  "resource://gre/modules/PlacesUtils.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "FormHistory",
                                  "resource://gre/modules/FormHistory.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
                                  "resource://gre/modules/Downloads.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Promise",
                                  "resource://gre/modules/Promise.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Task",
                                  "resource://gre/modules/Task.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "DownloadsCommon",
                                  "resource:///modules/DownloadsCommon.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "console",
                                  "resource://gre/modules/Console.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Preferences",
                                  "resource://gre/modules/Preferences.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "setTimeout",
                                  "resource://gre/modules/Timer.jsm");


XPCOMUtils.defineLazyServiceGetter(this, "serviceWorkerManager",
                                   "@mozilla.org/serviceworkers/manager;1",
                                   "nsIServiceWorkerManager");
XPCOMUtils.defineLazyServiceGetter(this, "quotaManagerService",
                                   "@mozilla.org/dom/quota-manager-service;1",
                                   "nsIQuotaManagerService");

var {classes: Cc, interfaces: Ci, results: Cr} = Components;

/**
 * A number of iterations after which to yield time back
 * to the system.
 */
const YIELD_PERIOD = 10;

function Sanitizer() {
}
Sanitizer.prototype = {
  // warning to the caller: this one may raise an exception (e.g. bug #265028)
  clearItem: function (aItemName)
  {
    this.items[aItemName].clear();
  },

  prefDomain: "",

  getNameFromPreference: function (aPreferenceName)
  {
    return aPreferenceName.substr(this.prefDomain.length);
  },

  /**
   * Deletes privacy sensitive data in a batch, according to user preferences.
   * Returns a promise which is resolved if no errors occurred.  If an error
   * occurs, a message is reported to the console and all other items are still
   * cleared before the promise is finally rejected.
   *
   * @param [optional] itemsToClear
   *        Array of items to be cleared. if specified only those
   *        items get cleared, irrespectively of the preference settings.
   * @param [optional] options
   *        Object whose properties are options for this sanitization.
   *        TODO (bug 1167238) document options here.
   */
  sanitize: Task.async(function*(itemsToClear = null, options = {}) {
    let progress = options.progress || {};
    let promise = this._sanitize(itemsToClear, progress);

    // Depending on preferences, the sanitizer may perform asynchronous
    // work before it starts cleaning up the Places database (e.g. closing
    // windows). We need to make sure that the connection to that database
    // hasn't been closed by the time we use it.
    // Though, if this is a sanitize on shutdown, we already have a blocker.
    if (!progress.isShutdown) {
      let shutdownClient = Cc["@mozilla.org/browser/nav-history-service;1"]
                             .getService(Ci.nsPIPlacesDatabase)
                             .shutdownClient
                             .jsclient;
      shutdownClient.addBlocker("sanitize.js: Sanitize",
        promise,
        {
          fetchState: () => ({ progress })
        }
      );
    }

    try {
      yield promise;
    } finally {
      Services.obs.notifyObservers(null, "sanitizer-sanitization-complete", "");
    }
  }),

  _sanitize: Task.async(function*(aItemsToClear, progress = {}) {
    let seenError = false;
    let itemsToClear;
    if (Array.isArray(aItemsToClear)) {
      // Shallow copy the array, as we are going to modify
      // it in place later.
      itemsToClear = [...aItemsToClear];
    } else {
      let branch = Services.prefs.getBranch(this.prefDomain);
      itemsToClear = Object.keys(this.items).filter(itemName => {
        try {
          return branch.getBoolPref(itemName);
        } catch (ex) {
          return false;
        }
      });
    }

    // Store the list of items to clear, in case we are killed before we
    // get a chance to complete.
    Preferences.set(Sanitizer.PREF_SANITIZE_IN_PROGRESS,
                    JSON.stringify(itemsToClear));

    // Store the list of items to clear, for debugging/forensics purposes
    for (let k of itemsToClear) {
      progress[k] = "ready";
    }

    // Ensure open windows get cleared first, if they're in our list, so that they don't stick
    // around in the recently closed windows list, and so we can cancel the whole thing
    // if the user selects to keep a window open from a beforeunload prompt.
    let openWindowsIndex = itemsToClear.indexOf("openWindows");
    if (openWindowsIndex != -1) {
      itemsToClear.splice(openWindowsIndex, 1);
      yield this.items.openWindows.clear();
      progress.openWindows = "cleared";
    }

    // Cache the range of times to clear
    let range = null;
    // If we ignore timespan, clear everything,
    // otherwise, pick a range.
    if (!this.ignoreTimespan) {
      range = this.range || Sanitizer.getClearRange();
    }

    // For performance reasons we start all the clear tasks at once, then wait
    // for their promises later.
    // Some of the clear() calls may raise exceptions (for example bug 265028),
    // we catch and store them, but continue to sanitize as much as possible.
    // Callers should check returned errors and give user feedback
    // about items that could not be sanitized

    let annotateError = (name, ex) => {
      progress[name] = "failed";
      seenError = true;
      console.error("Error sanitizing " + name, ex);
    };

    // Array of objects in form { name, promise }.
    // `name` is the item's name and `promise` may be a promise, if the
    // sanitization is asynchronous, or the function return value, otherwise.
    let handles = [];
    for (let itemName of itemsToClear) {
      // Workaround for bug 449811.
      let name = itemName;
      let item = this.items[name];
      try {
        // Catch errors here, so later we can just loop through these.
        handles.push({ name,
                       promise: item.clear(range)
                                    .then(() => progress[name] = "cleared",
                                          ex => annotateError(name, ex))
                     });
      } catch (ex) {
        annotateError(name, ex);
      }
    }
    for (let handle of handles) {
      progress[handle.name] = "blocking";
      yield handle.promise;
    }

    // Sanitization is complete.

    // Reset the inProgress preference since we were not killed during
    // sanitization.
    Preferences.reset(Sanitizer.PREF_SANITIZE_IN_PROGRESS);
    progress = {};
    if (seenError) {
      throw new Error("Error sanitizing");
    }
  }),

  // Time span only makes sense in certain cases.  Consumers who want
  // to only clear some private data can opt in by setting this to false,
  // and can optionally specify a specific range.  If timespan is not ignored,
  // and range is not set, sanitize() will use the value of the timespan
  // pref to determine a range
  ignoreTimespan : true,
  range : null,

  items: {
    cache: {
      clear: Task.async(function* (range) {
        let seenException;

        try {
          // Cache doesn't consult timespan, nor does it have the
          // facility for timespan-based eviction.  Wipe it.
          let cache = Cc["@mozilla.org/netwerk/cache-storage-service;1"]
                        .getService(Ci.nsICacheStorageService);
          cache.clear();
        } catch (ex) {
          seenException = ex;
        }

        try {
          let imageCache = Cc["@mozilla.org/image/tools;1"]
                             .getService(Ci.imgITools)
                             .getImgCacheForDocument(null);
          imageCache.clearCache(false); // true=chrome, false=content
        } catch (ex) {
          seenException = ex;
        }

        if (seenException) {
          throw seenException;
        }
      })
    },

    cookies: {
      clear: Task.async(function* (range) {
        let seenException;
        let yieldCounter = 0;

        // Clear cookies.
        try {
          let cookieMgr = Components.classes["@mozilla.org/cookiemanager;1"]
                                    .getService(Ci.nsICookieManager);
          if (range) {
            // Iterate through the cookies and delete any created after our cutoff.
            let cookiesEnum = cookieMgr.enumerator;
            while (cookiesEnum.hasMoreElements()) {
              let cookie = cookiesEnum.getNext().QueryInterface(Ci.nsICookie2);

              if (cookie.creationTime > range[0]) {
                // This cookie was created after our cutoff, clear it
                cookieMgr.remove(cookie.host, cookie.name, cookie.path,
                                 false, cookie.originAttributes);

                if (++yieldCounter % YIELD_PERIOD == 0) {
                  yield new Promise(resolve => setTimeout(resolve, 0)); // Don't block the main thread too long
                }
              }
            }
          }
          else {
            // Remove everything
            cookieMgr.removeAll();
            yield new Promise(resolve => setTimeout(resolve, 0)); // Don't block the main thread too long
          }
        } catch (ex) {
          seenException = ex;
        }

        // Clear deviceIds. Done asynchronously (returns before complete).
        try {
          let mediaMgr = Components.classes["@mozilla.org/mediaManagerService;1"]
                                   .getService(Ci.nsIMediaManagerService);
          mediaMgr.sanitizeDeviceIds(range && range[0]);
        } catch (ex) {
          seenException = ex;
        }

        // Clear plugin data.
        // As evidenced in bug 1253204, clearing plugin data can sometimes be
        // very, very long, for mysterious reasons. Unfortunately, this is not
        // something actionable by Mozilla, so crashing here serves no purpose.
        //
        // For this reason, instead of waiting for sanitization to always
        // complete, we introduce a soft timeout. Once this timeout has
        // elapsed, we proceed with the shutdown of Firefox.
        let promiseClearPluginCookies;
        try {
          // We don't want to wait for this operation to complete...
          promiseClearPluginCookies = this.promiseClearPluginCookies(range);

          // ... at least, not for more than 10 seconds.
          yield Promise.race([
            promiseClearPluginCookies,
            new Promise(resolve => setTimeout(resolve, 10000 /* 10 seconds */))
          ]);
        } catch (ex) {
          seenException = ex;
        }

        // Detach waiting for plugin cookies to be cleared.
        promiseClearPluginCookies.catch(() => {
          // If this exception is raised before the soft timeout, it
          // will appear in `seenException`. Otherwise, it's too late
          // to do anything about it.
        });

        if (seenException) {
          throw seenException;
        }
      }),

      promiseClearPluginCookies: Task.async(function* (range) {
        const FLAG_CLEAR_ALL = Ci.nsIPluginHost.FLAG_CLEAR_ALL;
        let ph = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);

        // Determine age range in seconds. (-1 means clear all.) We don't know
        // that range[1] is actually now, so we compute age range based
        // on the lower bound. If range results in a negative age, do nothing.
        let age = range ? (Date.now() / 1000 - range[0] / 1000000) : -1;
        if (!range || age >= 0) {
          let tags = ph.getPluginTags();
          for (let tag of tags) {
            try {
              let rv = yield new Promise(resolve =>
                ph.clearSiteData(tag, null, FLAG_CLEAR_ALL, age, resolve)
              );
              // If the plugin doesn't support clearing by age, clear everything.
              if (rv == Components.results.NS_ERROR_PLUGIN_TIME_RANGE_NOT_SUPPORTED) {
                yield new Promise(resolve =>
                  ph.clearSiteData(tag, null, FLAG_CLEAR_ALL, -1, resolve)
                );
              }
            } catch (ex) {
              // Ignore errors from plug-ins
            }
          }
        }
      })
    },

    offlineApps: {
      clear: Task.async(function* (range) {
        // AppCache
        Components.utils.import("resource:///modules/offlineAppCache.jsm");
        // This doesn't wait for the cleanup to be complete.
        OfflineAppCacheHelper.clear();

        // LocalStorage
        Services.obs.notifyObservers(null, "extension:purge-localStorage", null);

        // ServiceWorkers
        let serviceWorkers = serviceWorkerManager.getAllRegistrations();
        for (let i = 0; i < serviceWorkers.length; i++) {
          let sw = serviceWorkers.queryElementAt(i, Ci.nsIServiceWorkerRegistrationInfo);
          let host = sw.principal.URI.host;
          serviceWorkerManager.removeAndPropagate(host);
        }

        // QuotaManager
        let promises = [];
        yield new Promise(resolve => {
          quotaManagerService.getUsage(request => {
            if (request.resultCode != Cr.NS_OK) {
              // We are probably shutting down. We don't want to propagate the
              // error, rejecting the promise.
              resolve();
              return;
            }

            for (let item of request.result) {
              let principal = Services.scriptSecurityManager.createCodebasePrincipalFromOrigin(item.origin);
              let uri = principal.URI;
              if (uri.scheme == "http" || uri.scheme == "https" || uri.scheme == "file") {
                promises.push(new Promise(r => {
                  let req = quotaManagerService.clearStoragesForPrincipal(principal, null, true);
                  req.callback = () => { r(); };
                }));
              }
            }
            resolve();
          });
        });

        yield Promise.all(promises);
      })
    },

    history: {
      clear: Task.async(function* (range) {
        let seenException;
        try {
          if (range) {
            yield PlacesUtils.history.removeVisitsByFilter({
              beginDate: new Date(range[0] / 1000),
              endDate: new Date(range[1] / 1000)
            });
          } else {
            // Remove everything.
            yield PlacesUtils.history.clear();
          }
        } catch (ex) {
          seenException = ex;
        }

        try {
          let clearStartingTime = range ? String(range[0]) : "";
          Services.obs.notifyObservers(null, "browser:purge-session-history", clearStartingTime);
        } catch (ex) {
          seenException = ex;
        }

        try {
          let predictor = Components.classes["@mozilla.org/network/predictor;1"]
                                    .getService(Components.interfaces.nsINetworkPredictor);
          predictor.reset();
        } catch (ex) {
          seenException = ex;
        }

        if (seenException) {
          throw seenException;
        }
      })
    },

    formdata: {
      clear: Task.async(function* (range) {
        let seenException;
        try {
          // Clear undo history of all searchBars
          let windows = Services.wm.getEnumerator("navigator:browser");
          while (windows.hasMoreElements()) {
            let currentWindow = windows.getNext();
            let currentDocument = currentWindow.document;
            let searchBar = currentDocument.getElementById("searchbar");
            if (searchBar)
              searchBar.textbox.reset();
            let tabBrowser = currentWindow.gBrowser;
            if (!tabBrowser) {
              // No tab browser? This means that it's too early during startup (typically,
              // Session Restore hasn't completed yet). Since we don't have find
              // bars at that stage and since Session Restore will not restore
              // find bars further down during startup, we have nothing to clear.
              continue;
            }
            for (let tab of tabBrowser.tabs) {
              if (tabBrowser.isFindBarInitialized(tab))
                tabBrowser.getFindBar(tab).clear();
            }
            // Clear any saved find value
            tabBrowser._lastFindValue = "";
          }
        } catch (ex) {
          seenException = ex;
        }

        try {
          let change = { op: "remove" };
          if (range) {
            [ change.firstUsedStart, change.firstUsedEnd ] = range;
          }
          yield new Promise(resolve => {
            FormHistory.update(change, {
              handleError(e) {
                seenException = new Error("Error " + e.result + ": " + e.message);
              },
              handleCompletion() {
                resolve();
              }
            });
          });
        } catch (ex) {
          seenException = ex;
        }

        if (seenException) {
          throw seenException;
        }
      })
    },

    downloads: {
      clear: Task.async(function* (range) {
        try {
          let filterByTime = null;
          if (range) {
            // Convert microseconds back to milliseconds for date comparisons.
            let rangeBeginMs = range[0] / 1000;
            let rangeEndMs = range[1] / 1000;
            filterByTime = download => download.startTime >= rangeBeginMs &&
                                       download.startTime <= rangeEndMs;
          }

          // Clear all completed/cancelled downloads
          let list = yield Downloads.getList(Downloads.ALL);
          list.removeFinished(filterByTime);
        } catch (ex) {
	}
      })
    },

    sessions: {
      clear: Task.async(function* (range) {

        try {
          // clear all auth tokens
          let sdr = Components.classes["@mozilla.org/security/sdr;1"]
                              .getService(Components.interfaces.nsISecretDecoderRing);
          sdr.logoutAndTeardown();

          // clear FTP and plain HTTP auth sessions
          Services.obs.notifyObservers(null, "net:clear-active-logins", null);
        } catch (ex) {
	}
      })
    },

    siteSettings: {
      clear: Task.async(function* (range) {
        let seenException;

        let startDateMS = range ? range[0] / 1000 : null;

        try {
          // Clear site-specific permissions like "Allow this site to open popups"
          // we ignore the "end" range and hope it is now() - none of the
          // interfaces used here support a true range anyway.
          if (startDateMS == null) {
            Services.perms.removeAll();
          } else {
            Services.perms.removeAllSince(startDateMS);
          }
        } catch (ex) {
          seenException = ex;
        }

        try {
          // Clear site-specific settings like page-zoom level
          let cps = Components.classes["@mozilla.org/content-pref/service;1"]
                              .getService(Components.interfaces.nsIContentPrefService2);
          if (startDateMS == null) {
            cps.removeAllDomains(null);
          } else {
            cps.removeAllDomainsSince(startDateMS, null);
          }
        } catch (ex) {
          seenException = ex;
        }

        try {
          // Clear site security settings - no support for ranges in this
          // interface either, so we clearAll().
          let sss = Cc["@mozilla.org/ssservice;1"]
                      .getService(Ci.nsISiteSecurityService);
          sss.clearAll();
        } catch (ex) {
          seenException = ex;
        }

        // Clear all push notification subscriptions
        try {
          yield new Promise((resolve, reject) => {
            let push = Cc["@mozilla.org/push/Service;1"]
                         .getService(Ci.nsIPushService);
            push.clearForDomain("*", status => {
              if (Components.isSuccessCode(status)) {
                resolve();
              } else {
                reject(new Error("Error clearing push subscriptions: " +
                                 status));
              }
            });
          });
        } catch (ex) {
          seenException = ex;
        }

        if (seenException) {
          throw seenException;
        }
      })
    },

    openWindows: {
      privateStateForNewWindow: "non-private",
      _canCloseWindow: function(aWindow) {
        if (aWindow.CanCloseWindow()) {
          // We already showed PermitUnload for the window, so let's
          // make sure we don't do it again when we actually close the
          // window.
          aWindow.skipNextCanClose = true;
          return true;
        }
        return false;
      },
      _resetAllWindowClosures: function(aWindowList) {
        for (let win of aWindowList) {
          win.skipNextCanClose = false;
        }
      },
      clear: Task.async(function* () {
        // NB: this closes all *browser* windows, not other windows like the library, about window,
        // browser console, etc.

        // Keep track of the time in case we get stuck in la-la-land because of onbeforeunload
        // dialogs
        let existingWindow = Services.appShell.hiddenDOMWindow;
        let startDate = existingWindow.performance.now();

        // First check if all these windows are OK with being closed:
        let windowEnumerator = Services.wm.getEnumerator("navigator:browser");
        let windowList = [];
        while (windowEnumerator.hasMoreElements()) {
          let someWin = windowEnumerator.getNext();
          windowList.push(someWin);
          // If someone says "no" to a beforeunload prompt, we abort here:
          if (!this._canCloseWindow(someWin)) {
            this._resetAllWindowClosures(windowList);
            throw new Error("Sanitize could not close windows: cancelled by user");
          }

          // ...however, beforeunload prompts spin the event loop, and so the code here won't get
          // hit until the prompt has been dismissed. If more than 1 minute has elapsed since we
          // started prompting, stop, because the user might not even remember initiating the
          // 'forget', and the timespans will be all wrong by now anyway:
          if (existingWindow.performance.now() > (startDate + 60 * 1000)) {
            this._resetAllWindowClosures(windowList);
            throw new Error("Sanitize could not close windows: timeout");
          }
        }

        // If/once we get here, we should actually be able to close all windows.

        // First create a new window. We do this first so that on non-mac, we don't
        // accidentally close the app by closing all the windows.
        let handler = Cc["@mozilla.org/browser/clh;1"].getService(Ci.nsIBrowserHandler);
        let defaultArgs = handler.defaultArgs;
        let features = "chrome,all,dialog=no," + this.privateStateForNewWindow;
        let newWindow = existingWindow.openDialog("chrome://browser/content/", "_blank",
                                                  features, defaultArgs);

        let onFullScreen = null;
        if (AppConstants.platform == "macosx") {
          onFullScreen = function(e) {
            newWindow.removeEventListener("fullscreen", onFullScreen);
            let docEl = newWindow.document.documentElement;
            let sizemode = docEl.getAttribute("sizemode");
            if (!newWindow.fullScreen && sizemode == "fullscreen") {
              docEl.setAttribute("sizemode", "normal");
              e.preventDefault();
              e.stopPropagation();
              return false;
            }
            return undefined;
          }
          newWindow.addEventListener("fullscreen", onFullScreen);
        }

        let promiseReady = new Promise(resolve => {
          // Window creation and destruction is asynchronous. We need to wait
          // until all existing windows are fully closed, and the new window is
          // fully open, before continuing. Otherwise the rest of the sanitizer
          // could run too early (and miss new cookies being set when a page
          // closes) and/or run too late (and not have a fully-formed window yet
          // in existence). See bug 1088137.
          let newWindowOpened = false;
          let onWindowOpened = function(subject, topic, data) {
            if (subject != newWindow)
              return;

            Services.obs.removeObserver(onWindowOpened, "browser-delayed-startup-finished");
            if (AppConstants.platform == "macosx") {
              newWindow.removeEventListener("fullscreen", onFullScreen);
            }
            newWindowOpened = true;
            // If we're the last thing to happen, invoke callback.
            if (numWindowsClosing == 0) {
              resolve();
            }
          }

          let numWindowsClosing = windowList.length;
          let onWindowClosed = function() {
            numWindowsClosing--;
            if (numWindowsClosing == 0) {
              Services.obs.removeObserver(onWindowClosed, "xul-window-destroyed");
              // If we're the last thing to happen, invoke callback.
              if (newWindowOpened) {
                resolve();
              }
            }
          }
          Services.obs.addObserver(onWindowOpened, "browser-delayed-startup-finished", false);
          Services.obs.addObserver(onWindowClosed, "xul-window-destroyed", false);
        });

        // Start the process of closing windows
        while (windowList.length) {
          windowList.pop().close();
        }
        newWindow.focus();
        yield promiseReady;
      })
    },
  }
};

// The preferences branch for the sanitizer.
Sanitizer.PREF_DOMAIN = "privacy.sanitize.";
// Whether we should sanitize on shutdown.
Sanitizer.PREF_SANITIZE_ON_SHUTDOWN = "privacy.sanitize.sanitizeOnShutdown";
// During a sanitization this is set to a json containing the array of items
// being sanitized, then cleared once the sanitization is complete.
// This allows to retry a sanitization on startup in case it was interrupted
// by a crash.
Sanitizer.PREF_SANITIZE_IN_PROGRESS = "privacy.sanitize.sanitizeInProgress";
// Whether the previous shutdown sanitization completed successfully.
// This is used to detect cases where we were supposed to sanitize on shutdown
// but due to a crash we were unable to.  In such cases there may not be any
// sanitization in progress, cause we didn't have a chance to start it yet.
Sanitizer.PREF_SANITIZE_DID_SHUTDOWN = "privacy.sanitize.didShutdownSanitize";

// Time span constants corresponding to values of the privacy.sanitize.timeSpan
// pref.  Used to determine how much history to clear, for various items
Sanitizer.TIMESPAN_EVERYTHING = 0;
Sanitizer.TIMESPAN_HOUR       = 1;
Sanitizer.TIMESPAN_2HOURS     = 2;
Sanitizer.TIMESPAN_4HOURS     = 3;
Sanitizer.TIMESPAN_TODAY      = 4;
Sanitizer.TIMESPAN_5MIN       = 5;
Sanitizer.TIMESPAN_24HOURS    = 6;

// Return a 2 element array representing the start and end times,
// in the uSec-since-epoch format that PRTime likes.  If we should
// clear everything, return null.  Use ts if it is defined; otherwise
// use the timeSpan pref.
Sanitizer.getClearRange = function (ts) {
  if (ts === undefined)
    ts = Sanitizer.prefs.getIntPref("timeSpan");
  if (ts === Sanitizer.TIMESPAN_EVERYTHING)
    return null;

  // PRTime is microseconds while JS time is milliseconds
  var endDate = Date.now() * 1000;
  switch (ts) {
    case Sanitizer.TIMESPAN_5MIN :
      var startDate = endDate - 300000000; // 5*60*1000000
      break;
    case Sanitizer.TIMESPAN_HOUR :
      startDate = endDate - 3600000000; // 1*60*60*1000000
      break;
    case Sanitizer.TIMESPAN_2HOURS :
      startDate = endDate - 7200000000; // 2*60*60*1000000
      break;
    case Sanitizer.TIMESPAN_4HOURS :
      startDate = endDate - 14400000000; // 4*60*60*1000000
      break;
    case Sanitizer.TIMESPAN_TODAY :
      var d = new Date();  // Start with today
      d.setHours(0);      // zero us back to midnight...
      d.setMinutes(0);
      d.setSeconds(0);
      startDate = d.valueOf() * 1000; // convert to epoch usec
      break;
    case Sanitizer.TIMESPAN_24HOURS :
      startDate = endDate - 86400000000; // 24*60*60*1000000
      break;
    default:
      throw "Invalid time span for clear private data: " + ts;
  }
  return [startDate, endDate];
};

Sanitizer._prefs = null;
Sanitizer.__defineGetter__("prefs", function()
{
  return Sanitizer._prefs ? Sanitizer._prefs
    : Sanitizer._prefs = Components.classes["@mozilla.org/preferences-service;1"]
                         .getService(Components.interfaces.nsIPrefService)
                         .getBranch(Sanitizer.PREF_DOMAIN);
});

// Shows sanitization UI
Sanitizer.showUI = function(aParentWindow)
{
  let win = AppConstants.platform == "macosx" ?
    null: // make this an app-modal window on Mac
    aParentWindow;
  Services.ww.openWindow(win,
                         "chrome://browser/content/sanitize.xul",
                         "Sanitize",
                         "chrome,titlebar,dialog,centerscreen,modal",
                         null);
};

/**
 * Deletes privacy sensitive data in a batch, optionally showing the
 * sanitize UI, according to user preferences
 */
Sanitizer.sanitize = function(aParentWindow)
{
  Sanitizer.showUI(aParentWindow);
};

Sanitizer.onStartup = Task.async(function*() {
  // Check if we were interrupted during the last shutdown sanitization.
  let shutownSanitizationWasInterrupted =
    Preferences.get(Sanitizer.PREF_SANITIZE_ON_SHUTDOWN, false) &&
    !Preferences.has(Sanitizer.PREF_SANITIZE_DID_SHUTDOWN);

  if (Preferences.has(Sanitizer.PREF_SANITIZE_DID_SHUTDOWN)) {
    // Reset the pref, so that if we crash before having a chance to
    // sanitize on shutdown, we will do at the next startup.
    // Flushing prefs has a cost, so do this only if necessary.
    Preferences.reset(Sanitizer.PREF_SANITIZE_DID_SHUTDOWN);
    Services.prefs.savePrefFile(null);
  }

  // Make sure that we are triggered during shutdown.
  let shutdownClient = Cc["@mozilla.org/browser/nav-history-service;1"]
                         .getService(Ci.nsPIPlacesDatabase)
                         .shutdownClient
                         .jsclient;
  // We need to pass to sanitize() (through sanitizeOnShutdown) a state object
  // that tracks the status of the shutdown blocker. This `progress` object
  // will be updated during sanitization and reported with the crash in case of
  // a shutdown timeout.
  // We use the `options` argument to pass the `progress` object to sanitize().
  let progress = { isShutdown: true };
  shutdownClient.addBlocker("sanitize.js: Sanitize on shutdown",
    () => sanitizeOnShutdown({ progress }),
    {
      fetchState: () => ({ progress })
    }
  );

  // Check if Firefox crashed during a sanitization.
  let lastInterruptedSanitization = Preferences.get(Sanitizer.PREF_SANITIZE_IN_PROGRESS, "");
  if (lastInterruptedSanitization) {
    let s = new Sanitizer();
    // If the json is invalid this will just throw and reject the Task.
    let itemsToClear = JSON.parse(lastInterruptedSanitization);
    yield s.sanitize(itemsToClear);
  } else if (shutownSanitizationWasInterrupted) {
    // Otherwise, could be we were supposed to sanitize on shutdown but we
    // didn't have a chance, due to an earlier crash.
    // In such a case, just redo a shutdown sanitize now, during startup.
    yield sanitizeOnShutdown();
  }
});

var sanitizeOnShutdown = Task.async(function*(options = {}) {
  if (!Preferences.get(Sanitizer.PREF_SANITIZE_ON_SHUTDOWN)) {
    return;
  }
  // Need to sanitize upon shutdown
  let s = new Sanitizer();
  s.prefDomain = "privacy.clearOnShutdown.";
  yield s.sanitize(null, options);
  // We didn't crash during shutdown sanitization, so annotate it to avoid
  // sanitizing again on startup.
  Preferences.set(Sanitizer.PREF_SANITIZE_DID_SHUTDOWN, true);
  Services.prefs.savePrefFile(null);
});