Validate User IP and User Session in ExpressJS

Here's an example of an express middleware that retrieves the IP address and user agent from a Mongoose collection called "Session" and compares it with the incoming request's user IP and user agent:

const mongoose = require('mongoose');
const Session = mongoose.model('Session');

const verifySession = async (req, res, next) => {
  try {
    const session = await Session.findOne({ _id: req.sessionID });
    if (!session) {
      return res.status(401).send('Session not found');
    }
    const ipAddress = req.headers['x-forwarded-for'] || req.socket.remoteAddress;
    const userAgent = req.headers['user-agent'];
    if (session.ipAddress !== ipAddress || session.userAgent !== userAgent) {
      return res.status(401).send('Unauthorized access');
    }
    next();
  } catch (err) {
    console.error(err);
    res.status(500).send('Server Error');
  }
};

module.exports = verifySession;

Explanation:

1. First, we import the Mongoose model for "Session".
2. Then we define a middleware function called "verifySession" that takes in the "req", "res", and "next" parameters.
3. Inside the "verifySession" function, we use the "findOne" method of the "Session" model to find the session corresponding to the "req.sessionID" value.
4. If the session is not found, we return a 401 Unauthorized status code with the message "Session not found".
5. We then retrieve the IP address and user agent from the request headers using the "x-forwarded-for" and "user-agent" properties, respectively.
6. Next, we compare the retrieved IP address and user agent with the corresponding values in the session document.
7. If they don't match, we return a 401 Unauthorized status code with the message "Unauthorized access".
8. If everything checks out, we call the "next" function to pass control to the next middleware in the chain.
9. If there's an error while retrieving the session, we catch it and return a 500 Internal Server Error status code with the message "Server Error".
10. Finally, we export the middleware function for use in our application.