1 files changed, 209 insertions, 0 deletions
diff --git a/toolkit/components/resistfingerprinting/UserCharacteristicsPageService.sys.mjs b/toolkit/components/resistfingerprinting/UserCharacteristicsPageService.sys.mjs
new file mode 100644
index 0000000000..d24a2eae33
--- /dev/null
+++ b/toolkit/components/resistfingerprinting/UserCharacteristicsPageService.sys.mjs
@@ -0,0 +1,209 @@
+// -*- 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 https://mozilla.org/MPL/2.0/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  HiddenFrame: "resource://gre/modules/HiddenFrame.sys.mjs",
+});
+
+ChromeUtils.defineLazyGetter(lazy, "console", () => {
+  return console.createInstance({
+    prefix: "UserCharacteristicsPage",
+    maxLogLevelPref: "toolkit.telemetry.user_characteristics_ping.logLevel",
+  });
+});
+
+const BACKGROUND_WIDTH = 1024;
+const BACKGROUND_HEIGHT = 768;
+
+/**
+ * A manager for hidden browsers. Responsible for creating and destroying a
+ * hidden frame to hold them.
+ * All of this is copied from PageDataService.sys.mjs
+ */
+class HiddenBrowserManager {
+  /**
+   * The hidden frame if one has been created.
+   *
+   * @type {HiddenFrame | null}
+   */
+  #frame = null;
+  /**
+   * The number of hidden browser elements currently in use.
+   *
+   * @type {number}
+   */
+  #browsers = 0;
+
+  /**
+   * Creates and returns a new hidden browser.
+   *
+   * @returns {Browser}
+   */
+  async #acquireBrowser() {
+    this.#browsers++;
+    if (!this.#frame) {
+      this.#frame = new lazy.HiddenFrame();
+    }
+
+    let frame = await this.#frame.get();
+    let doc = frame.document;
+    let browser = doc.createXULElement("browser");
+    browser.setAttribute("remote", "true");
+    browser.setAttribute("type", "content");
+    browser.setAttribute(
+      "style",
+      `
+        width: ${BACKGROUND_WIDTH}px;
+        min-width: ${BACKGROUND_WIDTH}px;
+        height: ${BACKGROUND_HEIGHT}px;
+        min-height: ${BACKGROUND_HEIGHT}px;
+      `
+    );
+    browser.setAttribute("maychangeremoteness", "true");
+    doc.documentElement.appendChild(browser);
+
+    return browser;
+  }
+
+  /**
+   * Releases the given hidden browser.
+   *
+   * @param {Browser} browser
+   *   The hidden browser element.
+   */
+  #releaseBrowser(browser) {
+    browser.remove();
+
+    this.#browsers--;
+    if (this.#browsers == 0) {
+      this.#frame.destroy();
+      this.#frame = null;
+    }
+  }
+
+  /**
+   * Calls a callback function with a new hidden browser.
+   * This function will return whatever the callback function returns.
+   *
+   * @param {Callback} callback
+   *   The callback function will be called with the browser element and may
+   *   be asynchronous.
+   * @returns {T}
+   */
+  async withHiddenBrowser(callback) {
+    let browser = await this.#acquireBrowser();
+    try {
+      return await callback(browser);
+    } finally {
+      this.#releaseBrowser(browser);
+    }
+  }
+}
+
+export class UserCharacteristicsPageService {
+  classId = Components.ID("{ce3e9659-e311-49fb-b18b-7f27c6659b23}");
+  QueryInterface = ChromeUtils.generateQI([
+    "nsIUserCharacteristicsPageService",
+  ]);
+
+  _initialized = false;
+  _isParentProcess = false;
+
+  /**
+   * A manager for hidden browsers.
+   *
+   * @type {HiddenBrowserManager}
+   */
+  _browserManager = new HiddenBrowserManager();
+
+  /**
+   * A map of hidden browsers to a resolve function that should be passed the
+   * actor that was created for the browser.
+   *
+   * @type {WeakMap<Browser, function(PageDataParent): void>}
+   */
+  _backgroundBrowsers = new WeakMap();
+
+  constructor() {
+    lazy.console.debug("Init");
+
+    if (
+      Services.appinfo.processType !== Services.appinfo.PROCESS_TYPE_DEFAULT
+    ) {
+      throw new Error(
+        "Shouldn't init UserCharacteristicsPage in content processes."
+      );
+    }
+
+    // Return if we have initiated.
+    if (this._initialized) {
+      lazy.console.warn("preventing re-initilization...");
+      return;
+    }
+    this._initialized = true;
+  }
+
+  shutdown() {}
+
+  createContentPage() {
+    lazy.console.debug("called createContentPage");
+    return this._browserManager.withHiddenBrowser(async browser => {
+      lazy.console.debug(`In withHiddenBrowser`);
+      try {
+        let { promise, resolve } = Promise.withResolvers();
+        this._backgroundBrowsers.set(browser, resolve);
+
+        let principal = Services.scriptSecurityManager.getSystemPrincipal();
+        let loadURIOptions = {
+          triggeringPrincipal: principal,
+        };
+
+        let userCharacteristicsPageURI = Services.io.newURI(
+          "about:fingerprinting"
+        );
+
+        browser.loadURI(userCharacteristicsPageURI, loadURIOptions);
+
+        let data = await promise;
+        if (data.debug) {
+          lazy.console.debug(`Debugging Output:`);
+          for (let line of data.debug) {
+            lazy.console.debug(line);
+          }
+          lazy.console.debug(`(debugging output done)`);
+        }
+        lazy.console.debug(`Data:`, data.output);
+
+        lazy.console.debug("Populating Glean metrics...");
+        Glean.characteristics.timezone.set(data.output.foo);
+
+        lazy.console.debug("Unregistering actor");
+        Services.obs.notifyObservers(
+          null,
+          "user-characteristics-populating-data-done"
+        );
+      } finally {
+        this._backgroundBrowsers.delete(browser);
+      }
+    });
+  }
+
+  async pageLoaded(browsingContext, data) {
+    lazy.console.debug(
+      `pageLoaded browsingContext=${browsingContext} data=${data}`
+    );
+
+    let browser = browsingContext.embedderElement;
+
+    let backgroundResolve = this._backgroundBrowsers.get(browser);
+    if (backgroundResolve) {
+      backgroundResolve(data);
+      return;
+    }
+    throw new Error(`No backround resolve for ${browser} found`);
+  }
+}