1 files changed, 399 insertions, 0 deletions
diff --git a/application/basilisk/components/sessionstore/SessionFile.jsm b/application/basilisk/components/sessionstore/SessionFile.jsm
new file mode 100644
index 0000000000..2fdf2e101e
--- /dev/null
+++ b/application/basilisk/components/sessionstore/SessionFile.jsm
@@ -0,0 +1,399 @@
+/* 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/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["SessionFile"];
+
+/**
+ * Implementation of all the disk I/O required by the session store.
+ * This is a private API, meant to be used only by the session store.
+ * It will change. Do not use it for any other purpose.
+ *
+ * Note that this module implicitly depends on one of two things:
+ * 1. either the asynchronous file I/O system enqueues its requests
+ *   and never attempts to simultaneously execute two I/O requests on
+ *   the files used by this module from two distinct threads; or
+ * 2. the clients of this API are well-behaved and do not place
+ *   concurrent requests to the files used by this module.
+ *
+ * Otherwise, we could encounter bugs, especially under Windows,
+ *   e.g. if a request attempts to write sessionstore.js while
+ *   another attempts to copy that file.
+ *
+ * This implementation uses OS.File, which guarantees property 1.
+ */
+
+const Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/osfile.jsm");
+Cu.import("resource://gre/modules/Promise.jsm");
+Cu.import("resource://gre/modules/AsyncShutdown.jsm");
+Cu.import("resource://gre/modules/Preferences.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "console",
+  "resource://gre/modules/Console.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PromiseUtils",
+  "resource://gre/modules/PromiseUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "RunState",
+  "resource:///modules/sessionstore/RunState.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "TelemetryStopwatch",
+  "resource://gre/modules/TelemetryStopwatch.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyServiceGetter(this, "Telemetry",
+  "@mozilla.org/base/telemetry;1", "nsITelemetry");
+XPCOMUtils.defineLazyServiceGetter(this, "sessionStartup",
+  "@mozilla.org/browser/sessionstartup;1", "nsISessionStartup");
+XPCOMUtils.defineLazyModuleGetter(this, "SessionWorker",
+  "resource:///modules/sessionstore/SessionWorker.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "SessionStore",
+  "resource:///modules/sessionstore/SessionStore.jsm");
+
+const PREF_UPGRADE_BACKUP = "browser.sessionstore.upgradeBackup.latestBuildID";
+const PREF_MAX_UPGRADE_BACKUPS = "browser.sessionstore.upgradeBackup.maxUpgradeBackups";
+
+const PREF_MAX_SERIALIZE_BACK = "browser.sessionstore.max_serialize_back";
+const PREF_MAX_SERIALIZE_FWD = "browser.sessionstore.max_serialize_forward";
+
+this.SessionFile = {
+  /**
+   * Read the contents of the session file, asynchronously.
+   */
+  read: function () {
+    return SessionFileInternal.read();
+  },
+  /**
+   * Write the contents of the session file, asynchronously.
+   */
+  write: function (aData) {
+    return SessionFileInternal.write(aData);
+  },
+  /**
+   * Wipe the contents of the session file, asynchronously.
+   */
+  wipe: function () {
+    return SessionFileInternal.wipe();
+  },
+
+  /**
+   * Return the paths to the files used to store, backup, etc.
+   * the state of the file.
+   */
+  get Paths() {
+    return SessionFileInternal.Paths;
+  }
+};
+
+Object.freeze(SessionFile);
+
+var Path = OS.Path;
+var profileDir = OS.Constants.Path.profileDir;
+
+var SessionFileInternal = {
+  Paths: Object.freeze({
+    // The path to the latest version of sessionstore written during a clean
+    // shutdown. After startup, it is renamed `cleanBackup`.
+    clean: Path.join(profileDir, "sessionstore.js"),
+
+    // The path at which we store the previous version of `clean`. Updated
+    // whenever we successfully load from `clean`.
+    cleanBackup: Path.join(profileDir, "sessionstore-backups", "previous.js"),
+
+    // The directory containing all sessionstore backups.
+    backups: Path.join(profileDir, "sessionstore-backups"),
+
+    // The path to the latest version of the sessionstore written
+    // during runtime. Generally, this file contains more
+    // privacy-sensitive information than |clean|, and this file is
+    // therefore removed during clean shutdown. This file is designed to protect
+    // against crashes / sudden shutdown.
+    recovery: Path.join(profileDir, "sessionstore-backups", "recovery.js"),
+
+    // The path to the previous version of the sessionstore written
+    // during runtime (e.g. 15 seconds before recovery). In case of a
+    // clean shutdown, this file is removed.  Generally, this file
+    // contains more privacy-sensitive information than |clean|, and
+    // this file is therefore removed during clean shutdown.  This
+    // file is designed to protect against crashes that are nasty
+    // enough to corrupt |recovery|.
+    recoveryBackup: Path.join(profileDir, "sessionstore-backups", "recovery.bak"),
+
+    // The path to a backup created during an upgrade of Firefox.
+    // Having this backup protects the user essentially from bugs in
+    // Firefox or add-ons, especially for users of Nightly. This file
+    // does not contain any information more sensitive than |clean|.
+    upgradeBackupPrefix: Path.join(profileDir, "sessionstore-backups", "upgrade.js-"),
+
+    // The path to the backup of the version of the session store used
+    // during the latest upgrade of Firefox. During load/recovery,
+    // this file should be used if both |path|, |backupPath| and
+    // |latestStartPath| are absent/incorrect.  May be "" if no
+    // upgrade backup has ever been performed. This file does not
+    // contain any information more sensitive than |clean|.
+    get upgradeBackup() {
+      let latestBackupID = SessionFileInternal.latestUpgradeBackupID;
+      if (!latestBackupID) {
+        return "";
+      }
+      return this.upgradeBackupPrefix + latestBackupID;
+    },
+
+    // The path to a backup created during an upgrade of Firefox.
+    // Having this backup protects the user essentially from bugs in
+    // Firefox, especially for users of Nightly.
+    get nextUpgradeBackup() {
+      return this.upgradeBackupPrefix + Services.appinfo.platformBuildID;
+    },
+
+    /**
+     * The order in which to search for a valid sessionstore file.
+     */
+    get loadOrder() {
+      // If `clean` exists and has been written without corruption during
+      // the latest shutdown, we need to use it.
+      //
+      // Otherwise, `recovery` and `recoveryBackup` represent the most
+      // recent state of the session store.
+      //
+      // Finally, if nothing works, fall back to the last known state
+      // that can be loaded (`cleanBackup`) or, if available, to the
+      // backup performed during the latest upgrade.
+      let order = ["clean",
+                   "recovery",
+                   "recoveryBackup",
+                   "cleanBackup"];
+      if (SessionFileInternal.latestUpgradeBackupID) {
+        // We have an upgradeBackup
+        order.push("upgradeBackup");
+      }
+      return order;
+    },
+  }),
+
+  // Number of attempted calls to `write`.
+  // Note that we may have _attempts > _successes + _failures,
+  // if attempts never complete.
+  // Used for error reporting.
+  _attempts: 0,
+
+  // Number of successful calls to `write`.
+  // Used for error reporting.
+  _successes: 0,
+
+  // Number of failed calls to `write`.
+  // Used for error reporting.
+  _failures: 0,
+
+  // Resolved once initialization is complete.
+  // The promise never rejects.
+  _deferredInitialized: PromiseUtils.defer(),
+
+  // `true` once we have started initialization, i.e. once something
+  // has been scheduled that will eventually resolve `_deferredInitialized`.
+  _initializationStarted: false,
+
+  // The ID of the latest version of Goanna for which we have an upgrade backup
+  // or |undefined| if no upgrade backup was ever written.
+  get latestUpgradeBackupID() {
+    try {
+      return Services.prefs.getCharPref(PREF_UPGRADE_BACKUP);
+    } catch (ex) {
+      return undefined;
+    }
+  },
+
+  // Find the correct session file, read it and setup the worker.
+  read: Task.async(function* () {
+    this._initializationStarted = true;
+
+    let result;
+    let noFilesFound = true;
+    // Attempt to load by order of priority from the various backups
+    for (let key of this.Paths.loadOrder) {
+      let corrupted = false;
+      let exists = true;
+      try {
+        let path = this.Paths[key];
+        let startMs = Date.now();
+
+        let source = yield OS.File.read(path, { encoding: "utf-8" });
+        let parsed = JSON.parse(source);
+
+        if (!SessionStore.isFormatVersionCompatible(parsed.version || ["sessionrestore", 0] /*fallback for old versions*/)) {
+          // Skip sessionstore files that we don't understand.
+          Cu.reportError("Cannot extract data from Session Restore file " + path + ". Wrong format/version: " + JSON.stringify(parsed.version) + ".");
+          continue;
+        }
+        result = {
+          origin: key,
+          source: source,
+          parsed: parsed
+        };
+        Telemetry.getHistogramById("FX_SESSION_RESTORE_CORRUPT_FILE").
+          add(false);
+        Telemetry.getHistogramById("FX_SESSION_RESTORE_READ_FILE_MS").
+          add(Date.now() - startMs);
+        break;
+      } catch (ex if ex instanceof OS.File.Error && ex.becauseNoSuchFile) {
+        exists = false;
+      } catch (ex if ex instanceof OS.File.Error) {
+        // The file might be inaccessible due to wrong permissions
+        // or similar failures. We'll just count it as "corrupted".
+        console.error("Could not read session file ", ex, ex.stack);
+        corrupted = true;
+      } catch (ex if ex instanceof SyntaxError) {
+        console.error("Corrupt session file (invalid JSON found) ", ex, ex.stack);
+        // File is corrupted, try next file
+        corrupted = true;
+      } finally {
+        if (exists) {
+          noFilesFound = false;
+          Telemetry.getHistogramById("FX_SESSION_RESTORE_CORRUPT_FILE").
+            add(corrupted);
+        }
+      }
+    }
+
+    // All files are corrupted if files found but none could deliver a result.
+    let allCorrupt = !noFilesFound && !result;
+    Telemetry.getHistogramById("FX_SESSION_RESTORE_ALL_FILES_CORRUPT").
+      add(allCorrupt);
+
+    if (!result) {
+      // If everything fails, start with an empty session.
+      result = {
+        origin: "empty",
+        source: "",
+        parsed: null
+      };
+    }
+
+    result.noFilesFound = noFilesFound;
+
+    // Initialize the worker (in the background) to let it handle backups and also
+    // as a workaround for bug 964531.
+    let promiseInitialized = SessionWorker.post("init", [result.origin, this.Paths, {
+      maxUpgradeBackups: Preferences.get(PREF_MAX_UPGRADE_BACKUPS, 3),
+      maxSerializeBack: Preferences.get(PREF_MAX_SERIALIZE_BACK, 10),
+      maxSerializeForward: Preferences.get(PREF_MAX_SERIALIZE_FWD, -1)
+    }]);
+
+    promiseInitialized.catch(err => {
+      // Ensure that we report errors but that they do not stop us.
+      Promise.reject(err);
+    }).then(() => this._deferredInitialized.resolve());
+
+    return result;
+  }),
+
+  // Post a message to the worker, making sure that it has been initialized
+  // first.
+  _postToWorker: Task.async(function*(...args) {
+    if (!this._initializationStarted) {
+      // Initializing the worker is somewhat complex, as proper handling of
+      // backups requires us to first read and check the session. Consequently,
+      // the only way to initialize the worker is to first call `this.read()`.
+
+      // The call to `this.read()` causes background initialization of the worker.
+      // Initialization will be complete once `this._deferredInitialized.promise`
+      // resolves.
+      this.read();
+    }
+    yield this._deferredInitialized.promise;
+    return SessionWorker.post(...args)
+  }),
+
+  write: function (aData) {
+    if (RunState.isClosed) {
+      return Promise.reject(new Error("SessionFile is closed"));
+    }
+
+    let isFinalWrite = false;
+    if (RunState.isClosing) {
+      // If shutdown has started, we will want to stop receiving
+      // write instructions.
+      isFinalWrite = true;
+      RunState.setClosed();
+    }
+
+    let performShutdownCleanup = isFinalWrite &&
+      !sessionStartup.isAutomaticRestoreEnabled();
+
+    this._attempts++;
+    let options = {isFinalWrite, performShutdownCleanup};
+    let promise = this._postToWorker("write", [aData, options]);
+
+    // Wait until the write is done.
+    promise = promise.then(msg => {
+      // Record how long the write took.
+      this._recordTelemetry(msg.telemetry);
+      this._successes++;
+      if (msg.result.upgradeBackup) {
+        // We have just completed a backup-on-upgrade, store the information
+        // in preferences.
+        Services.prefs.setCharPref(PREF_UPGRADE_BACKUP,
+          Services.appinfo.platformBuildID);
+      }
+    }, err => {
+      // Catch and report any errors.
+      console.error("Could not write session state file ", err, err.stack);
+      this._failures++;
+      // By not doing anything special here we ensure that |promise| cannot
+      // be rejected anymore. The shutdown/cleanup code at the end of the
+      // function will thus always be executed.
+    });
+
+    // Ensure that we can write sessionstore.js cleanly before the profile
+    // becomes unaccessible.
+    AsyncShutdown.profileBeforeChange.addBlocker(
+      "SessionFile: Finish writing Session Restore data",
+      promise,
+      {
+        fetchState: () => ({
+          options,
+          attempts: this._attempts,
+          successes: this._successes,
+          failures: this._failures,
+        })
+      });
+
+    // This code will always be executed because |promise| can't fail anymore.
+    // We ensured that by having a reject handler that reports the failure but
+    // doesn't forward the rejection.
+    return promise.then(() => {
+      // Remove the blocker, no matter if writing failed or not.
+      AsyncShutdown.profileBeforeChange.removeBlocker(promise);
+
+      if (isFinalWrite) {
+        Services.obs.notifyObservers(null, "sessionstore-final-state-write-complete", "");
+      }
+    });
+  },
+
+  wipe: function () {
+    return this._postToWorker("wipe");
+  },
+
+  _recordTelemetry: function(telemetry) {
+    for (let id of Object.keys(telemetry)){
+      let value = telemetry[id];
+      let samples = [];
+      if (Array.isArray(value)) {
+        samples.push(...value);
+      } else {
+        samples.push(value);
+      }
+      let histogram = Telemetry.getHistogramById(id);
+      for (let sample of samples) {
+        histogram.add(sample);
+      }
+    }
+  }
+};