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@FezVrasta
Created February 6, 2021 15:00
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Firebase Twitch OAuth Flow (Cloud Functions implementation)
'use strict';
const functions = require('firebase-functions');
const admin = require('firebase-admin');
const cookieParser = require('cookie-parser');
const crypto = require('crypto');
const { AuthorizationCode } = require('simple-oauth2');
const fetch = require('node-fetch');
// Firebase Setup
const admin = require('firebase-admin');
// @ts-ignore
const serviceAccount = require('./service-account.json');
admin.initializeApp({
credential: admin.credential.cert(serviceAccount),
databaseURL: `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`,
});
const OAUTH_REDIRECT_URI = `https://${process.env.GCLOUD_PROJECT}.firebaseapp.com/popup.html`;;
const OAUTH_SCOPES = 'user:read:email';
/**
* Creates a configured simple-oauth2 client for Twitch.
*/
function twitchOAuth2Client() {
// Twitch OAuth 2 setup
// TODO: Configure the `twitch.client_id` and `twitch.client_secret` Google Cloud environment variables.
const credentials = {
client: {
id: functions.config().twitch.client_id,
secret: functions.config().twitch.client_secret,
},
auth: {
tokenHost: 'https://id.twitch.tv',
tokenPath: '/oauth2/token',
authorizePath: '/oauth2/authorize',
},
options: {
bodyFormat: 'json',
authorizationMethod: 'body',
},
};
return new AuthorizationCode(credentials);
}
/**
* Redirects the User to the Twitch authentication consent screen. Also the 'state' cookie is set for later state
* verification.
*/
exports.redirect = functions.https.onRequest((req, res) => {
const authorizationCode = twitchOAuth2Client();
cookieParser()(req, res, () => {
const state = req.cookies.__session || crypto.randomBytes(20).toString('hex');
console.log('Setting verification state:', state);
res.cookie('__session', state.toString(), { maxAge: 3600000, httpOnly: true });
const redirectUri = authorizationCode.authorizeURL({
redirect_uri: OAUTH_REDIRECT_URI,
scope: OAUTH_SCOPES,
state: state,
});
console.log('Redirecting to:', redirectUri);
res.redirect(redirectUri);
});
});
/**
* Exchanges a given Twitch auth code passed in the 'code' URL query parameter for a Firebase auth token.
* The request also needs to specify a 'state' query parameter which will be checked against the 'state' cookie.
* The Firebase custom auth token, display name, photo URL and Twitch acces token are sent back in a JSONP callback
* function with function name defined by the 'callback' query parameter.
*/
exports.token = functions.https.onRequest((req, res) => {
const authorizationCode = twitchOAuth2Client();
try {
cookieParser()(req, res, async () => {
try {
console.log('Received verification state:', req.cookies.__session);
console.log('Received state:', req.query.state);
if (!req.cookies.__session) {
throw new Error(
'State cookie not set or expired. Maybe you took too long to authorize. Please try again.'
);
} else if (req.cookies.__session !== req.query.state) {
throw new Error('State validation failed');
}
} catch (error) {
return res.jsonp({ error: error.toString() });
}
let accessToken;
try {
console.log('Received auth code:', req.query.code);
const options = {
client_id: functions.config().twitch.client_id,
client_secret: functions.config().twitch.client_secret,
code: req.query.code,
grant_type: 'authorization_code',
redirect_uri: OAUTH_REDIRECT_URI,
};
console.log('Asking token with options', JSON.stringify(options));
accessToken = await authorizationCode.getToken(options);
console.log('Auth code exchange result received');
const twitchUser = await getTwitchUser(accessToken.toJSON().access_token);
// Create a Firebase account and get the Custom Auth Token.
const firebaseToken = await createFirebaseAccount(twitchUser);
// Serve an HTML page that signs the user in and updates the user profile.
return res.jsonp({ token: firebaseToken });
} catch (error) {
return res.jsonp({ error: error.toString() });
}
});
} catch (error) {
return res.jsonp({ error: error.toString() });
}
});
/**
* Creates a Firebase account with the given user profile and returns a custom auth token allowing
* signing-in this account.
*
* @returns {Promise<string>} The Firebase custom auth token in a promise.
*/
async function createFirebaseAccount(twitchUser) {
// The UID we'll assign to the user.
const uid = `twitch:${twitchUser.id}`;
// Save the access token to the Firebase Database.
const db = admin.firestore();
const databaseTask = db.collection('users').doc(uid).set(twitchUser);
// Create or update the user account.
const userCreationTask = admin
.auth()
.updateUser(uid, {
displayName: twitchUser['display_name'],
photoURL: twitchUser['profile_image_url'],
email: twitchUser['email'],
})
.catch((error) => {
// If user does not exists we create it.
if (error.code === 'auth/user-not-found') {
return admin.auth().createUser({
uid: uid,
displayName: twitchUser['display_name'],
photoURL: twitchUser['profile_image_url'],
email: twitchUser['email'],
});
}
throw error;
});
// Wait for all async task to complete then generate and return a custom auth token.
await Promise.all([userCreationTask, databaseTask]);
// Create a Firebase custom auth token.
const token = await admin.auth().createCustomToken(uid);
console.log('Created Custom token for UID "', uid, '" Token:', token);
return token;
}
async function getTwitchUser(accessToken) {
console.log('Fetching Twitch user with access_token', accessToken);
try {
const response = await fetch('https://api.twitch.tv/helix/users', {
method: 'GET',
headers: {
'Client-Id': functions.config().twitch.client_id,
Authorization: 'Bearer ' + accessToken,
},
});
const data = await response.json();
return { ...data.data[0], access_token: accessToken };
} catch (error) {
console.error(error);
}
}
@FezVrasta
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I can't find it in my code anymore, I think I switched to the full redirect flow for some reason.

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