Develop Reference

Single flow: sign user in via Google oAuth AND grant offline/server access?

I'm trying to implement Google sign-in and API access for a web app with a Node.js back end. Google's docs provide two options using a combo of platform.js client-side and google-auth-library server-side:
Google Sign-In with back-end auth, via which users can log into my app using their Google account. (auth2.signIn() on the client and verifyIdToken() on the server.)
Google Sign-in for server-side apps, via which I can authorize the server to connect to Google directly on behalf of my users. (auth2.grantOfflineAccess() on the client, which returns a code I can pass to getToken() on the server.)
I need both: I want to authenticate users via Google sign-in; and, I want to set up server auth so it can also work on behalf of the user.
I can't figure out how to do this with a single authentication flow. The closest I can get is to do the two in sequence: authenticate the user first with signIn(), and then (as needed), do a second pass via grantOfflineAccess(). This is problematic:
The user now has to go through two authentications back to back, which is awkward and makes it look like there's something broken with my app.
In order to avoid running afoul of popup blockers, I can't give them those two flows on top of each other; I have to do the first authentication, then supply a button to start the second authentication. This is super-awkward because now I have to explain why the first one wasn't enough.
Ideally there's some variant of signIn() that adds the offline access into the initial authentication flow and returns the code along with the usual tokens, but I'm not seeing anything. Help?
(Edit: Some advice I received elsewhere is to implement only flow #2, then use a secure cookie store some sort of user identifier that I check against the user account with each request. I can see that this would work functionally, but it basically means I'm rolling my own login system, which would seem to increase the chance I introduce bugs in a critical system.)

To add an API to an existing Google Sign-In integration the best option is to implement incremental authorization. For this, you need to use both google-auth-library and googleapis, so that users can have this workflow:
Authenticate with Google Sign-In.
Authorize your application to use their information to integrate it with a Google API. For instance, Google Calendar. 
For this, your client-side JavaScript for authentication might require some changes to request
offline access:
$('#signinButton').click(function() {
auth2.grantOfflineAccess().then(signInCallback);
});
In the response, you will have a JSON object with an authorization code:
{"code":"4/yU4cQZTMnnMtetyFcIWNItG32eKxxxgXXX-Z4yyJJJo.4qHskT-UtugceFc0ZRONyF4z7U4UmAI"}
After this, you can use the one-time code to exchange it for an access token and refresh token.
Here are some workflow details:
The code is your one-time code that your server can exchange for its own access token and refresh token. You can only obtain a refresh token after the user has been presented an authorization dialog requesting offline access. If you've specified the select-account prompt in the OfflineAccessOptions [...], you must store the refresh token that you retrieve for later use because subsequent exchanges will return null for the refresh token
Therefore, you should use google-auth-library to complete this workflow in the back-end. For this,
you'll use the authentication code to get a refresh token. However, as this is an offline workflow,
you also need to verify the integrity of the provided code as the documentation explains:
If you use Google Sign-In with an app or site that communicates with a backend server, you might need to identify the currently signed-in user on the server. To do so securely, after a user successfully signs in, send the user's ID token to your server using HTTPS. Then, on the server, verify the integrity of the ID token and use the user information contained in the token
The final function to get the refresh token that you should persist in your database might look like
this:
const { OAuth2Client } = require('google-auth-library');
/**
* Create a new OAuth2Client, and go through the OAuth2 content
* workflow. Return the refresh token.
*/
function getRefreshToken(code, scope) {
return new Promise((resolve, reject) => {
// Create an oAuth client to authorize the API call. Secrets should be
// downloaded from the Google Developers Console.
const oAuth2Client = new OAuth2Client(
YOUR_CLIENT_ID,
YOUR_CLIENT_SECRET,
YOUR_REDIRECT_URL
);
// Generate the url that will be used for the consent dialog.
await oAuth2Client.generateAuthUrl({
access_type: 'offline',
scope,
});
// Verify the integrity of the idToken through the authentication
// code and use the user information contained in the token
const { tokens } = await client.getToken(code);
const ticket = await client.verifyIdToken({
idToken: tokens.id_token!,
audience: keys.web.client_secret,
});
idInfo = ticket.getPayload();
return tokens.refresh_token;
})
}
At this point, we've refactored the authentication workflow to support Google APIs. However, you haven't asked the user to authorize it yet. Since you also need to grant offline access, you should request additional permissions through your client-side application. Keep in mind that you already need an active session.
const googleOauth = gapi.auth2.getAuthInstance();
const newScope = "https://www.googleapis.com/auth/calendar"
googleOauth = auth2.currentUser.get();
googleOauth.grantOfflineAccess({ scope: newScope }).then(
function(success){
console.log(JSON.stringify({ message: "success", value: success }));
},
function(fail){
alert(JSON.stringify({message: "fail", value: fail}));
});
You're done with the front-end changes and you're only missing one step. To create a Google API's client in the back-end with the googleapis library, you need to use the refresh token from the previous step.
For a complete workflow with a Node.js back-end, you might find my gist helpful.

While authentication (sign in), you need to add "offline" access type (by default online) , so you will get a refresh token which you can use to get access token later without further user consent/authentication. You don't need to grant offline later, but only during signing in by adding the offline access_type. I don't know about platform.js but used "passport" npm module . I have also used "googleapis" npm module/library, this is official by Google.
https://developers.google.com/identity/protocols/oauth2/web-server
https://github.com/googleapis/google-api-nodejs-client
Check this:
https://github.com/googleapis/google-api-nodejs-client#generating-an-authentication-url
EDIT: You have a server side & you need to work on behalf of the user. You also want to use Google for signing in. You just need #2 Google Sign-in for server-side apps , why are you considering both #1 & #2 options.
I can think of #2 as the proper way based on your requirements. If you just want to signin, use basic scope such as email & profile (openid connect) to identify the user. And if you want user delegated permission (such as you want to automatically create an event in users calendar), just add the offline access_type during sign in. You can use only signing in for registered users & offline_access for new users.
Above is a single authentication flow.

how to reauthenticate user with firebase authentication?

I'm new to firebase.
In my nuxt js project with multiple pages, firestore rule is set to read or write once request.auth != null.
so if when refresh in a page, auth will be gone and it display error 'permission-denied' in terminal.
i tried Authentication State Persistence LOCAL but it doesn't work.
What is the purpose of using these auth persistence mode ?
firebase.auth().setPersistence(firebase.auth.Auth.Persistence.LOCAL)
.then(function() {
return firebase.auth().signInWithEmailAndPassword(email, password);
})

Auth session is automatically persistent on the frontend of your app, however Nuxt.js contains frontend and backend part. If you are storing user data somewhere on the frontend, you probably need to wait until the user data become accessible.
Example of the listener:
firebase.auth().onAuthStateChanged(function (user) {
if (user) {
console.log('User is logged: ', user);
}
});
However this will make user accessible only on the frontend, if you want to preload data on the backend you would need to store id and refresh token in the cookies or use Nuxt Firebase module which should handle service worker for you.
So, in your case it looks like you are trying to read the data before your user data become accessible (this can be caused by trying to fetch data on the backend).

REST API with Google Firebase Authentication & Functions using Bearer Token

Quick Background: I'm programming an API that is thought to be used "standalone" i.e. there is no frontend involved. API access should be possible directly from e.g. Postman or Curl with a Bearer token in the Authentication Header.
I was looking at Google Firebase and thought it is probably a really good fit because all of the authentication is already "builtin" and directly compatible with Google Cloud Functions.
However after a weekend of experimenting I can not seem to figure out how to implement an REST API (With Google Cloud Functions) where the User can (In an web-interface) request an API token to interact with the API.
I don't want to handle authentication myself. I really would love to use the Firebase authentication for the API.
Here is what the final process should look like:
User logs into an web-interface with the standard Firebase Authentication process.
User clicks on something like "Request API Key" and gets a key shown in the web-interface (e.g. abc...). that is generated by Firebase Authentication.
User can make requests with e.g. curl to the API Hosted in Google Cloud Functions and just has to set the Authorization Header (Bearer abc...) and the "validation" of that token is handled by Firebase Authentication.
Here is what I already tried to generate the token:
admin.auth().createCustomToken(uid)
.then(function(customToken) {
console.log(customToken);
})
.catch(function(error) {
console.log('Error creating custom token:', error);
})
And then set the Token logged to the console in Postman as Bearer Token, and then use the following function to verify the token:
const authenticate = async (req, res, next) => {
if (!req.headers.authorization || !req.headers.authorization.startsWith('Bearer ')) {
res.status(403).send('Unauthorized');
return;
}
const idToken = req.headers.authorization.split('Bearer ')[1];
try {
const decodedIdToken = await admin.auth().verifyIdToken(idToken);
req.user = decodedIdToken;
next();
return;
} catch(e) {
console.log(e);
res.status(403).send('Unauthorized');
return;
}
}
Then I get this error
message: 'verifyIdToken() expects an ID token, but was given a custom token. See https://firebase.google.com/docs/auth/admin/verify-id-tokens for details on how to retrieve an ID token.'
I understand that if I would implement an web-interface I could grab the ID token from the devtools (?), but the token is then only valid 1 hour... What I need is a token that is valid "indefinitely" and can be generated and shown to the user.
I think I know that I have to use Custom Tokens somehow but can not figure out how to get them working... (https://firebase.google.com/docs/auth/admin/create-custom-tokens).
Thanks very much in advance everybody!
Best
Rick

You're trying to build an API management solution on top of Firebase and Cloud Functions. Custom tokens and ID tokens are not suitable for this purpose. Custom tokens are only meant to be used as a user authentication credential on end user devices, and ID tokens represent a successful auth response. Both types of tokens expire after an hour.
If you need long-lived, managed API keys, then you will have to implement them yourself. There's nothing built into Firebase that you can use out of the box. I once implemented such a solution as a prototype, where I generated a Firestore document each time a user signed in and requested an API key. Then I used the document ID as the API key, which I could validate in the Cloud Function.
const apiKey = req.headers.authorization.split('Bearer ')[1];
const doc = await admin.firestore().collection('apiKeys').doc(apiKey).get();
if (doc.exists) {
next();
}
I also had to implement some local API key caching to make this work efficiently.
You might be able to avoid some of this work by using a solution like Google Cloud Endpoints (https://cloud.google.com/endpoints), although I don't have any personal experience with that. Finally, also look at open source solutions like https://wso2.com/api-management/ that enable you to set up your own API key management and gateway.

How to make Google Calendar API Requests using javascript and a service account?

I followed this quickstart tutorial for the Google Calendar API using javascript in my web application. As I need the possibility to show Calendar data on the webpage without user login, I need to implement API calls using a Service Account. Unfortunately I cant't find any good tutorials or explanations for doing so in javascript and since I am fairly new to the subject of API programming I kind of need some guidance.
Ty in advance.

Using Service account on client side is not secure. You may want to switch to a server side implementation for that. Assuming you are familiar with javascript I suggest to follow NodeJS implementation from here.
To create Service Account select service account after step 1->a.
Refer this image for option.
To use Service Account replace the authorize() logic with this
var email = credentials.client_email;
var key = credentials.private_key;
const jwt = new google.auth.JWT(
email, null, key, SCOPES
);
jwt.authorize((err, data) => {
if (err) {
console.error(err);
throw err;
}
console.log('You have been successfully authenticated: ', data);
callback(jwt);
});
As you are using Service Account you also need to create a calendar in your Gmail account to use. Then go to settings and select Add People to share it with client_email from your json, then use your Calendar Id (from Calendar settings) in API Call replacing primary

AWS Lambda - Cognito Identity ID changes with same login

I'm using AWS Lambda, Cognito, and API Gateway (orchestrated with Serverless) to build an API for my web-app.
A user authenticates using Cognito, and then makes an authenticated request to the API (pattern copied from the Serverless Stack tutorial, where I grab their Cognito ID:
event.requestContext.identity.cognitoIdentityId
Then I grab the user record associated with that cognitoIdentityId to perform role/permissions based logic and return the relevant data.
The trouble I've been running into is that when different people (other devs I'm working with, currently) log in using the same credentials, but from different computers (and, in some cases, countries), the cognitoIdentityId sent with their request is completely different -- for the same user userPool user record!
Note: I am not integrating with any "Federated Identities" (ie, Facebook, etc). This is plain old email sign-in. And everyone is using the same creds, but some people's requests come from different Cognito IDs.
This is highly problematic, because I don't see another way to uniquely identify the user record in my DB associated with the Cognito record.
QUESTIONS: Am I missing something? Is there a better way to do this? Is this the expected behavior?
The API is currently not actually plugged into a DB. Because our data structure is still in flux, and the app is far from live, I've built out an API that acts like it integrates with a database, and returns data, but that data is just stored in a JSON file. I'll reproduce some of the relevant code below, in case it's relevant.
An example lambda, for fetching the current user:
export function getSelf(event, context, callback) {
const { cognitoID } = parser(event);
const requester = cognitoID && users.find(u => u.cognitoID === cognitoID);
try {
if (requester) {
return callback(null, success(prep(requester, 0)));
} else {
return authError(callback, `No user found with ID: ${cognitoID}`);
}
} catch (error) {
return uncaughtError(callback, error);
}
}
That parser stuff up top is just a util to get the ID I want.
The associated user record might look like this:
{
cognitoID: 'us-west-2:605249a8-8fc1-40ed-bf89-23bc74ecc232',
id: 'some-slug',
email: 'email#whatever.com',
firstName: 'John',
lastName: 'Jacob Jingleheimer Schmidt',
headshot: 'http://fillmurray.com/g/300/300',
role: 'admin'
},

Cognito User Pools is used to authenticate users and provides you JWT tokens. When you want to access any AWS Services you need AWS Credentials (access key and secret key). This is where you should use Federated Identities. The tokens you get from Cognito User Pools should be exchanged with Federated Identities to get AWS credentials to access other AWS services. The serverless-stack also covers this in detail.
Now since you have not added the user pool as an authentication provider in your identity pool, my observation is that you are getting an unauthenticated identity from Federated Identities (you can confirm this from the Amazon Cognito console) which is why it is different for each of your team members. You should add the user pool as an authentication provider in the identity pool and follow the documentation to provide the information required in logins map.