CODEWITHSUNDEEP
javascriptfirebasecorsgoogle-cloud-functions
NeXtMaN_786
NeXtMaN_786

Reputation: 681

cors error within a cloud function

I've copied exactly what's written in the sample code here: https://github.com/firebase/functions-samples/blob/master/authorized-https-endpoint/functions/index.js

but I keep getting this error when trying to make a normal get request to the /savedProfiles endpoint

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://us-central1-my-app.cloudfunctions.net/savedProfiles. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).

This is my code:

'use strict';

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
const express = require('express');
const cookieParser = require('cookie-parser')();
const cors = require('cors')({origin: true});
const app = express();

// Express middleware that validates Firebase ID Tokens passed in the Authorization HTTP header.
// 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`.
const validateFirebaseIdToken = (req, res, next) => {
  console.log('Check if request is authorized with Firebase ID token');

  if ((!req.headers.authorization || !req.headers.authorization.startsWith('Bearer ')) &&
      !req.cookies.__session) {
    console.error('No Firebase ID token was passed as a Bearer token in the Authorization header.',
        'Make sure you authorize your request by providing the following HTTP header:',
        'Authorization: Bearer <Firebase ID Token>',
        'or by passing a "__session" cookie.');
    res.status(403).send('Unauthorized');
    return;
  }

  let idToken;
  if (req.headers.authorization && req.headers.authorization.startsWith('Bearer ')) {
    console.log('Found "Authorization" header');
    // Read the ID Token from the Authorization header.
    idToken = req.headers.authorization.split('Bearer ')[1];
  } else {
    console.log('Found "__session" cookie');
    // Read the ID Token from cookie.
    idToken = req.cookies.__session;
  }
  admin.auth().verifyIdToken(idToken).then((decodedIdToken) => {
    console.log('ID Token correctly decoded', decodedIdToken);
    req.user = decodedIdToken;
    return next();
  }).catch((error) => {
    console.error('Error while verifying Firebase ID token:', error);
    res.status(403).send('Unauthorized');
  });
};

app.use(cors);
app.use(cookieParser);
app.use(validateFirebaseIdToken);
app.get('/savedProfiles', (req, res) => {
  res.send(`Hello ${req.user.name}`);
});

// This HTTPS endpoint can only be accessed by your Firebase Users.
// Requests need to be authorized by providing an `Authorization` HTTP header
// with value `Bearer <Firebase ID Token>`.
exports.savedProfiles = functions.https.onRequest(app);

Shouldn't app.use(cors); prevent these sorts of errors?

Upvotes: 0

Views: 1548

Answers (2)

NeXtMaN_786
NeXtMaN_786

Reputation: 681

So I managed to get this to work without even using express. Here's what I came up with:

'use strict';

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
const cookieParser = require('cookie-parser')();
const cors = require('cors')({
  origin: 'http://localhost:8100'
});

exports.savedProfiles = functions.https.onRequest((req, res) => {
  cors(req, res, () => {

    console.log('Check if request is authorized with Firebase ID token');

    if ((!req.headers.authorization || !req.headers.authorization.startsWith('Bearer ')) &&
        !req.cookies.__session) {
      console.error('No Firebase ID token was passed as a Bearer token in the Authorization header.');

      res.status(403).send('Unauthorized');
      return;
    }

    let idToken;
    if (req.headers.authorization && req.headers.authorization.startsWith('Bearer ')) {
      // Read the ID Token from the Authorization header.
      idToken = req.headers.authorization.split('Bearer ')[1];
    } else {
      // Read the ID Token from cookie.
      idToken = req.cookies.__session;
    }

    admin.auth().verifyIdToken(idToken).then((decodedIdToken) => {
      req.user = decodedIdToken;
      res.status(200).send("SUCCESS");
      return;
    }).catch((error) => {
      console.error('Error while verifying Firebase ID token:', error);
      res.status(403).send('Unauthorized');
    });
  });
});

Upvotes: 2

attdona
attdona

Reputation: 18923

I did some test and on my PC the above cors setup works as expected.

Check the http response status: if I reproduce an error status (for example a 403) in my setup the Access-Control-Allow-Origin header is not present.

In validateFirebaseIdToken try to add:

res.set('Access-Control-Allow-Origin', '*');

just before res.status(403).send('Unauthorized'); expression to enable CORS also when errors happens.

Upvotes: 0

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