Proof of Concept: Google OAuth2 without the browser.identity API

background.js

/* 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/.
 * Portions Copyright (C) Philipp Kewisch, 2020 */

class OAuth2 {
  AUTH_URL = "https://accounts.google.com/o/oauth2/v2/auth"
  APPROVAL_URL = "https://accounts.google.com/o/oauth2/approval/v2"
  TOKEN_URL = "https://oauth2.googleapis.com/token"
  LOGOUT_URL = "https://oauth2.googleapis.com/revoke"

  EXPIRE_GRACE_SECONDS = 60
  WINDOW_WIDTH = 430
  WINDOW_HEIGHT = 750

  constructor({ clientId, clientSecret, scope }) {
    this.clientId = clientId;
    this.clientSecret = clientSecret;
    this.scope = scope;
  }

  get expired() {
    return Date.now() > this.expires;
  }

  async _approvalUrlViaTabs(wnd) {
    return new Promise((resolve, reject) => {
      let tabListener = (tabId, changeInfo) => {
        if (changeInfo.url) {
          browser.tabs.onUpdated.removeListener(tabListener);
          browser.windows.onRemoved.removeListener(windowListener);
          resolve(new URL(changeInfo.url));
        }
      };

      let windowListener = (windowId) => {
        if (windowId == wnd.id) {
          browser.tabs.onUpdated.removeListener(tabListener);
          browser.windows.onRemoved.removeListener(windowListener);
          reject({ error: "canceled" });
        }
      };

      browser.windows.onRemoved.addListener(windowListener);
      browser.tabs.onUpdated.addListener(tabListener, {
        urls: [this.APPROVAL_URL + "*"],
        windowId: wnd.id
      });
    });
  }

  async _approvalUrlViaWebRequest(wnd) {
    return new Promise((resolve, reject) => {
      let listener = (details) => {
        browser.webRequest.onBeforeRequest.removeListener(listener);
        browser.windows.onRemoved.removeListener(windowListener);

        resolve(new URL(details.url));
      };

      let windowListener = (windowId) => {
        if (windowId == wnd.id) {
          browser.webRequest.onBeforeRequest.removeListener(listener);
          browser.windows.onRemoved.removeListener(windowListener);
          reject({ error: "canceled" });
        }
      };

      browser.windows.onRemoved.addListener(windowListener);
      browser.webRequest.onBeforeRequest.addListener(listener, {
        urls: [this.APPROVAL_URL + "*"],
        windowId: wnd.id
      });
    });
  }

  async login({ titlePreface="", loginHint="" }) {
    // Create a window initiating the OAuth2 login process
    let params = new URLSearchParams({
      client_id: this.clientId,
      scope: this.scope,
      response_type: "code",
      redirect_uri: "urn:ietf:wg:oauth:2.0:oob:auto",
      login_hint: loginHint,
      hl: browser.i18n.getUILanguage(), // eslint-disable-line id-length
    });

    let wnd = await browser.windows.create({
      titlePreface: titlePreface,
      type: "popup",
      url: this.AUTH_URL + "?" + params,
      width: this.WINDOW_WIDTH,
      height: this.WINDOW_HEIGHT,
    });

    // Wait for the approval request to settle. There are two ways to do this: via the tabs
    // permission, or via webRequest. Use the method that uses the least amount of extra
    // permissions.
    let approvalUrl = await this._approvalUrlViaTabs(wnd);
    await browser.windows.remove(wnd.id);

    // Turn the approval code into the refresh and access tokens
    params = new URLSearchParams(approvalUrl.search.substr(1));

    if (params.get("response").startsWith("error=")) {
      throw { error: params.get("response").substr(6) };
    }

    let response = await fetch(this.TOKEN_URL, {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded;charset=utf-8", },
      body: new URLSearchParams({
        client_id: this.clientId,
        client_secret: this.clientSecret,
        code: params.get("approvalCode"),
        grant_type: "authorization_code",
        redirect_uri: "urn:ietf:wg:oauth:2.0:oob:auto"
      })
    });

    if (!response.ok) {
      throw { error: "request_error" };
    }

    let details = await response.json();

    this.accessToken = details.access_token;
    this.refreshToken = details.refresh_token;
    this.grantedScopes = details.scope;
    this.expires = new Date(Date.now() + 1000 * (details.expires_in - this.EXPIRE_GRACE_SECONDS));
  }

  async refresh(force=false) {
    if (!force && !this.expired) {
      return;
    }

    let response = await fetch(this.TOKEN_URL, {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded;charset=utf-8", },
      body: new URLSearchParams({
        client_id: this.clientId,
        client_secret: this.clientSecret,
        grant_type: "refresh_token",
        refresh_token: this.refreshToken
      })
    });

    if (!response.ok) {
      throw { error: "request_error" };
    }

    let details = await response.json();

    this.accessToken = details.access_token;
    this.expires = new Date(Date.now() + 1000 * (details.expires_in - this.EXPIRE_GRACE_SECONDS));
    this.grantedScopes = details.scope;
  }

  async logout() {
    let token = this.expired ? this.refreshToken : this.accessToken;

    let response = await fetch(this.LOGOUT_URL, {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded;charset=utf-8", },
      body: new URLSearchParams({ token })
    });

    if (!response.ok) {
      throw { error: "request_error" };
    }

    this.accessToken = null;
    this.refreshToken = null;
    this.grantedScopes = null;
    this.expires = null;
  }
}

browser.browserAction.onClicked.addListener(async () => {
  try {
    let oauth = new OAuth2({
      clientId: "YOUR_CLIENT_ID_HERE",
      clientSecret: "YOUR_CLIENT_SECRET_HERE",
      scope: "SPACE_SEPARATED_SCOPES_HERE",
    });

    await oauth.login({
      titlePreface: "Google OAuth Login: ",
      loginHint: "ACCOUNT_EMAIL_HERE",
    });

    console.log("AUTHINFO", oauth.accessToken, oauth.refreshToken);

    await oauth.refresh(true);
    console.log("AUTHINFO", oauth.accessToken, oauth.refreshToken);

    await oauth.logout();
  } catch (e) {
    console.error(e);
  }
});

manifest.json

// 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/.
// Portions Copyright (C) Philipp Kewisch, 2020

{
  "manifest_version": 2,
  "name": "Google OAuth2 PoC",
  "description": "Proof of concept for OAuth2 without the browser.identity API",
  "version": "1.0.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "google-oauth-poc@mozilla.kewis.ch"
    }
  },

  "icons": {
    "128": "images/addon.svg"
  },

  "permissions": [
    // There are two methods to wait for the OAuth process to complete. Via webRequest:
    // "webRequest",
    // "https://accounts.google.com/o/oauth2/approval/v2",

    // ...or via tabs.onUpdated. Pick whatever permission you already use.
    "tabs"
  ],

  "browser_action": {
    "default_icon": "images/addon.svg",
    "default_title": "Start Google OAuth"
  },

  "background": {
    "scripts": [
      "background.js"
    ]
  }
}