Can't set headers after they are sent...no issue until I added in authentication?

Question

I'm having some issues trying to send an axios requests with custom headers from my app so I can use them for authentication on my server.

I have a react native app that uses firebase authentication and a node/express backend server.

When a user signs in, I will grab their firebase idtoken and store it.

I will then send that idtoken as a header whenever I make an axios request to the server.

 const { currentUser } = firebase.auth();

  const url = ${serverUrl}/api/users/${user.uid`;

  const idtoken = await currentUser.getToken(true);

    var config = {
      headers: { idtoken },
    };

const response = await axios(url, config);

In the server code, there will be an express middleware that checks whether the idtoken sent in the request header is valid or not. If it is, it will call next() and proceed to execute the logic. If not, then it'll fail and send a 401 status.

This is in my app.js:

const app = express();


  app.use(bodyParser.json());

  app.use(firebaseAuthentication);
  router(app);

This is the firebaseAuthentication middleware:

const firebaseAuthentication = async (req, res, next) => {
  console.log(req);
  try {
    const { idtoken } = req.headers;

    await admin.auth().verifyIdToken(idtoken);
    next();
  } catch (e) {
    res.status(401).send({ error: 'Unauthorized request. Must be signed in via firebase' });
  }
};

This is the router:

module.exports = app => {

    app.get('/api/users/:firebaseUID', UserController.getUser);
}

The issue is that everything seems to go through until it tries to send the good data back to the user...but I get a 404 and a Error: Can't set headers after they are sent

This is the specific request that is failing:

  async getUser(req, res, next) {
    const firebaseUID = req.params.firebaseUID;
    try {
      const user = await User.findOne({ firebaseUID });

      res.send(user);
    } catch (e) {
      next(e);
    }
  },

What is happening here and how can I fix it? Thanks!

do you get the correct data back when you log `response` also are you sure it gets authenticated, because it seems like it sends `401` first — Ahmed Can Unbay, Sep 10 '17 at 19:52
Basically this error comes when you have sent back a response prematurely. That is headers have already been sent back to the client from Node. — trk, Sep 10 '17 at 19:53
@82Tuskers you have a point, async might be the problem here, the function might throw as it is waiting for **auth** — Ahmed Can Unbay, Sep 10 '17 at 19:55
if I `console.log(user)`, then it sends back exactly what it should do. — judgejab, Sep 10 '17 at 19:56
Do include `more` code to debug this. The exact flow between the server's middleware (route handler and `next()`) presently seems unclear (to me). — trk, Sep 10 '17 at 20:00
` app.use(firebaseAuthentication); router(app); ` I have it in that order in my `app.js`. All of the routes are within the `router()` — judgejab, Sep 10 '17 at 20:02
@MattCleary did you try removing `async` here `async getUser(req, res, next) {...}` — trk, Sep 10 '17 at 20:10
@MattCleary also I see that you have a more `next()` s . You have other middleware's too that will receive them ? — trk, Sep 10 '17 at 20:12
re: `and use promises instead? ` I don't think you need it. Can you try running it without ? Let me post it in the answer section and then may be I can interactively correct it. — trk, Sep 10 '17 at 20:13
How can I pass it onto the request handler if I don't call next? — judgejab, Sep 10 '17 at 20:14
Tried to take it off, but doesn't work, User.findOne() is async. It's connecting to my mongoDb — judgejab, Sep 10 '17 at 20:15
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/154084/discussion-between-82tuskers-and-matt-cleary). — trk, Sep 10 '17 at 20:34

Can't set headers after they are sent...no issue until I added in authentication?

0 Answers0