firebaseUser.js

/**
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict';

const admin = require('firebase-admin');
const cookieParser = require('cookie-parser')();
const functions = require('firebase-functions/v1');

// Express middleware that checks if a Firebase ID Tokens is passed in the `Authorization` HTTP
// header or the `__session` cookie and decodes it.
// The Firebase ID token needs to be passed as a Bearer token in the Authorization HTTP header like this:
// `Authorization: Bearer <Firebase ID Token>`.
// When decoded successfully, the ID Token content will be added as `req.user`.
async function validateFirebaseIdToken (req, res, next) {
  functions.logger.log('Check if request is authorized with Firebase ID token');

  const idToken = await getIdTokenFromRequest(req, res);
  if (idToken) {
    await addDecodedIdTokenToRequest(idToken, req);
  }
  next();
}

/**
 * Returns a Promise with the Firebase ID Token if found in the Authorization or the __session cookie.
 */
function getIdTokenFromRequest(req, res) {
  if (req.headers.authorization && req.headers.authorization.startsWith('Bearer ')) {
    functions.logger.log('Found "Authorization" header');
    // Read the ID Token from the Authorization header.
    return Promise.resolve(req.headers.authorization.split('Bearer ')[1]);
  }
  return new Promise((resolve, reject) => {
    cookieParser(req, res, () => {
      if (req.cookies && req.cookies.__session) {
        functions.logger.log('Found "__session" cookie');
        // Read the ID Token from cookie.
        resolve(req.cookies.__session);
      } else {
        resolve();
      }
    });
  });
}

/**
 * Returns a Promise with the Decoded ID Token and adds it to req.user.
 */
async function addDecodedIdTokenToRequest(idToken, req) {
  try {
    const decodedIdToken = await admin.auth().verifyIdToken(idToken);
    req.user = decodedIdToken;
    functions.logger.log('ID Token correctly decoded', decodedIdToken);
  } catch (error) {
    functions.logger.error('Error while verifying Firebase ID token:', error);
  }
}

exports.validateFirebaseIdToken = validateFirebaseIdToken;