1 files changed, 381 insertions, 0 deletions
diff --git a/browser/components/sessionstore/SessionWorker.js b/browser/components/sessionstore/SessionWorker.js
new file mode 100644
index 000000000..7d802a7df
--- /dev/null
+++ b/browser/components/sessionstore/SessionWorker.js
@@ -0,0 +1,381 @@
+/* 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/. */
+
+/**
+ * A worker dedicated to handle I/O for Session Store.
+ */
+
+"use strict";
+
+importScripts("resource://gre/modules/osfile.jsm");
+
+var PromiseWorker = require("resource://gre/modules/workers/PromiseWorker.js");
+
+var File = OS.File;
+var Encoder = new TextEncoder();
+var Decoder = new TextDecoder();
+
+var worker = new PromiseWorker.AbstractWorker();
+worker.dispatch = function(method, args = []) {
+  return Agent[method](...args);
+};
+worker.postMessage = function(result, ...transfers) {
+  self.postMessage(result, ...transfers);
+};
+worker.close = function() {
+  self.close();
+};
+
+self.addEventListener("message", msg => worker.handleMessage(msg));
+
+// The various possible states
+
+/**
+ * We just started (we haven't written anything to disk yet) from
+ * `Paths.clean`. The backup directory may not exist.
+ */
+const STATE_CLEAN = "clean";
+/**
+ * We know that `Paths.recovery` is good, either because we just read
+ * it (we haven't written anything to disk yet) or because have
+ * already written once to `Paths.recovery` during this session.
+ * `Paths.clean` is absent or invalid. The backup directory exists.
+ */
+const STATE_RECOVERY = "recovery";
+/**
+ * We just started from `Paths.recoverBackupy` (we haven't written
+ * anything to disk yet). Both `Paths.clean` and `Paths.recovery` are
+ * absent or invalid. The backup directory exists.
+ */
+const STATE_RECOVERY_BACKUP = "recoveryBackup";
+/**
+ * We just started from `Paths.upgradeBackup` (we haven't written
+ * anything to disk yet). Both `Paths.clean`, `Paths.recovery` and
+ * `Paths.recoveryBackup` are absent or invalid. The backup directory
+ * exists.
+ */
+const STATE_UPGRADE_BACKUP = "upgradeBackup";
+/**
+ * We just started without a valid session store file (we haven't
+ * written anything to disk yet). The backup directory may not exist.
+ */
+const STATE_EMPTY = "empty";
+
+var Agent = {
+  // Path to the files used by the SessionWorker
+  Paths: null,
+
+  /**
+   * The current state of the worker, as one of the following strings:
+   * - "permanent", once the first write has been completed;
+   * - "empty", before the first write has been completed,
+   *   if we have started without any sessionstore;
+   * - one of "clean", "recovery", "recoveryBackup", "cleanBackup",
+   *   "upgradeBackup", before the first write has been completed, if
+   *   we have started by loading the corresponding file.
+   */
+  state: null,
+
+  /**
+   * Number of old upgrade backups that are being kept
+   */
+  maxUpgradeBackups: null,
+
+  /**
+   * Initialize (or reinitialize) the worker
+   *
+   * @param {string} origin Which of sessionstore.js or its backups
+   *   was used. One of the `STATE_*` constants defined above.
+   * @param {object} paths The paths at which to find the various files.
+   * @param {object} prefs The preferences the worker needs to known.
+   */
+  init(origin, paths, prefs = {}) {
+    if (!(origin in paths || origin == STATE_EMPTY)) {
+      throw new TypeError("Invalid origin: " + origin);
+    }
+
+    // Check that all required preference values were passed.
+    for (let pref of ["maxUpgradeBackups", "maxSerializeBack", "maxSerializeForward"]) {
+      if (!prefs.hasOwnProperty(pref)) {
+        throw new TypeError(`Missing preference value for ${pref}`);
+      }
+    }
+
+    this.state = origin;
+    this.Paths = paths;
+    this.maxUpgradeBackups = prefs.maxUpgradeBackups;
+    this.maxSerializeBack = prefs.maxSerializeBack;
+    this.maxSerializeForward = prefs.maxSerializeForward;
+    this.upgradeBackupNeeded = paths.nextUpgradeBackup != paths.upgradeBackup;
+    return {result: true};
+  },
+
+  /**
+   * Write the session to disk.
+   * Write the session to disk, performing any necessary backup
+   * along the way.
+   *
+   * @param {object} state The state to write to disk.
+   * @param {object} options
+   *  - performShutdownCleanup If |true|, we should
+   *    perform shutdown-time cleanup to ensure that private data
+   *    is not left lying around;
+   *  - isFinalWrite If |true|, write to Paths.clean instead of
+   *    Paths.recovery
+   */
+  write: function (state, options = {}) {
+    let exn;
+    let telemetry = {};
+
+    // Cap the number of backward and forward shistory entries on shutdown.
+    if (options.isFinalWrite) {
+      for (let window of state.windows) {
+        for (let tab of window.tabs) {
+          let lower = 0;
+          let upper = tab.entries.length;
+
+          if (this.maxSerializeBack > -1) {
+            lower = Math.max(lower, tab.index - this.maxSerializeBack - 1);
+          }
+          if (this.maxSerializeForward > -1) {
+            upper = Math.min(upper, tab.index + this.maxSerializeForward);
+          }
+
+          tab.entries = tab.entries.slice(lower, upper);
+          tab.index -= lower;
+        }
+      }
+    }
+
+    let stateString = JSON.stringify(state);
+    let data = Encoder.encode(stateString);
+
+    try {
+
+      if (this.state == STATE_CLEAN || this.state == STATE_EMPTY) {
+        // The backups directory may not exist yet. In all other cases,
+        // we have either already read from or already written to this
+        // directory, so we are satisfied that it exists.
+        File.makeDir(this.Paths.backups);
+      }
+
+      if (this.state == STATE_CLEAN) {
+        // Move $Path.clean out of the way, to avoid any ambiguity as
+        // to which file is more recent.
+        File.move(this.Paths.clean, this.Paths.cleanBackup);
+      }
+
+      let startWriteMs = Date.now();
+
+      if (options.isFinalWrite) {
+        // We are shutting down. At this stage, we know that
+        // $Paths.clean is either absent or corrupted. If it was
+        // originally present and valid, it has been moved to
+        // $Paths.cleanBackup a long time ago. We can therefore write
+        // with the guarantees that we erase no important data.
+        File.writeAtomic(this.Paths.clean, data, {
+          tmpPath: this.Paths.clean + ".tmp"
+        });
+      } else if (this.state == STATE_RECOVERY) {
+        // At this stage, either $Paths.recovery was written >= 15
+        // seconds ago during this session or we have just started
+        // from $Paths.recovery left from the previous session. Either
+        // way, $Paths.recovery is good. We can move $Path.backup to
+        // $Path.recoveryBackup without erasing a good file with a bad
+        // file.
+        File.writeAtomic(this.Paths.recovery, data, {
+          tmpPath: this.Paths.recovery + ".tmp",
+          backupTo: this.Paths.recoveryBackup
+        });
+      } else {
+        // In other cases, either $Path.recovery is not necessary, or
+        // it doesn't exist or it has been corrupted. Regardless,
+        // don't backup $Path.recovery.
+        File.writeAtomic(this.Paths.recovery, data, {
+          tmpPath: this.Paths.recovery + ".tmp"
+        });
+      }
+
+      telemetry.FX_SESSION_RESTORE_WRITE_FILE_MS = Date.now() - startWriteMs;
+      telemetry.FX_SESSION_RESTORE_FILE_SIZE_BYTES = data.byteLength;
+
+    } catch (ex) {
+      // Don't throw immediately
+      exn = exn || ex;
+    }
+
+    // If necessary, perform an upgrade backup
+    let upgradeBackupComplete = false;
+    if (this.upgradeBackupNeeded
+      && (this.state == STATE_CLEAN || this.state == STATE_UPGRADE_BACKUP)) {
+      try {
+        // If we loaded from `clean`, the file has since then been renamed to `cleanBackup`.
+        let path = this.state == STATE_CLEAN ? this.Paths.cleanBackup : this.Paths.upgradeBackup;
+        File.copy(path, this.Paths.nextUpgradeBackup);
+        this.upgradeBackupNeeded = false;
+        upgradeBackupComplete = true;
+      } catch (ex) {
+        // Don't throw immediately
+        exn = exn || ex;
+      }
+
+      // Find all backups
+      let iterator;
+      let backups = [];  // array that will contain the paths to all upgrade backup
+      let upgradeBackupPrefix = this.Paths.upgradeBackupPrefix;  // access for forEach callback
+
+      try {
+        iterator = new File.DirectoryIterator(this.Paths.backups);
+        iterator.forEach(function (file) {
+          if (file.path.startsWith(upgradeBackupPrefix)) {
+            backups.push(file.path);
+          }
+        }, this);
+      } catch (ex) {
+          // Don't throw immediately
+          exn = exn || ex;
+      } finally {
+        if (iterator) {
+          iterator.close();
+        }
+      }
+
+      // If too many backups exist, delete them
+      if (backups.length > this.maxUpgradeBackups) {
+        // Use alphanumerical sort since dates are in YYYYMMDDHHMMSS format
+        backups.sort().forEach((file, i) => {
+          // remove backup file if it is among the first (n-maxUpgradeBackups) files
+          if (i < backups.length - this.maxUpgradeBackups) {
+            File.remove(file);
+          }
+        });
+      }
+    }
+
+    if (options.performShutdownCleanup && !exn) {
+
+      // During shutdown, if auto-restore is disabled, we need to
+      // remove possibly sensitive data that has been stored purely
+      // for crash recovery. Note that this slightly decreases our
+      // ability to recover from OS-level/hardware-level issue.
+
+      // If an exception was raised, we assume that we still need
+      // these files.
+      File.remove(this.Paths.recoveryBackup);
+      File.remove(this.Paths.recovery);
+    }
+
+    this.state = STATE_RECOVERY;
+
+    if (exn) {
+      throw exn;
+    }
+
+    return {
+      result: {
+        upgradeBackup: upgradeBackupComplete
+      },
+      telemetry: telemetry,
+    };
+  },
+
+  /**
+   * Wipes all files holding session data from disk.
+   */
+  wipe: function () {
+
+    // Don't stop immediately in case of error.
+    let exn = null;
+
+    // Erase main session state file
+    try {
+      File.remove(this.Paths.clean);
+    } catch (ex) {
+      // Don't stop immediately.
+      exn = exn || ex;
+    }
+
+    // Wipe the Session Restore directory
+    try {
+      this._wipeFromDir(this.Paths.backups, null);
+    } catch (ex) {
+      exn = exn || ex;
+    }
+
+    try {
+      File.removeDir(this.Paths.backups);
+    } catch (ex) {
+      exn = exn || ex;
+    }
+
+    // Wipe legacy Ression Restore files from the profile directory
+    try {
+      this._wipeFromDir(OS.Constants.Path.profileDir, "sessionstore.bak");
+    } catch (ex) {
+      exn = exn || ex;
+    }
+
+
+    this.state = STATE_EMPTY;
+    if (exn) {
+      throw exn;
+    }
+
+    return { result: true };
+  },
+
+  /**
+   * Wipe a number of files from a directory.
+   *
+   * @param {string} path The directory.
+   * @param {string|null} prefix If provided, only remove files whose
+   * name starts with a specific prefix.
+   */
+  _wipeFromDir: function(path, prefix) {
+    // Sanity check
+    if (typeof prefix == "undefined" || prefix == "") {
+      throw new TypeError();
+    }
+
+    let exn = null;
+
+    let iterator = new File.DirectoryIterator(path);
+    try {
+      if (!iterator.exists()) {
+        return;
+      }
+      for (let entry in iterator) {
+        if (entry.isDir) {
+          continue;
+        }
+        if (!prefix || entry.name.startsWith(prefix)) {
+          try {
+            File.remove(entry.path);
+          } catch (ex) {
+            // Don't stop immediately
+            exn = exn || ex;
+          }
+        }
+      }
+
+      if (exn) {
+        throw exn;
+      }
+    } finally {
+      iterator.close();
+    }
+  },
+};
+
+function isNoSuchFileEx(aReason) {
+  return aReason instanceof OS.File.Error && aReason.becauseNoSuchFile;
+}
+
+/**
+ * Estimate the number of bytes that a data structure will use on disk
+ * once serialized.
+ */
+function getByteLength(str) {
+  return Encoder.encode(JSON.stringify(str)).byteLength;
+}