Alright, so Firebase Authentication doesn't natively support LDAP (Lightweight Directory Access Protocol). But don't worry, we can make it work using Node.js and the 'ldapjs' module. First things first, make sure you have a Firebase project ready to go. Also, you'll need Node.js and npm installed on your computer.

Head over to the Firebase Console, pick your project or create a new one if you don't have one yet. Go to project settings (click the gear icon) -> Service Accounts, and generate a new private key. Download this key; we'll need it for the Firebase SDK later.

Create a new folder for your project. Open your terminal in this directory and run these commands to set up a new Node.js project:

npm init -y
npm install express --save
npm install ldapjs --save
npm install firebase-admin --save

This will set up a new Node.js project and install the necessary packages: Express for the web server, ldapjs for LDAP authentication, and firebase-admin to connect with Firebase.

Create an 'index.js' file with this basic structure:

const admin = require('firebase-admin');
const express = require('express');
const ldap = require('ldapjs');

const serviceAccount = require('./path-to-your-service-account-file.json');

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount)
});

const ldapClient = ldap.createClient({
  url: 'ldaps://ldap-server-url',
});

const app = express();

app.post('/login', (req, res) => {
  // Login Code Goes Here...
});

app.listen(3000, () => console.log('Server Started'));

Make sure to replace './path-to-your-service-account-file.json' and 'ldaps://ldap-server-url' with your Firebase JSON key file path and LDAP server URL.

In the '/login' route, bind the LDAP client with the provided username and password. If the binding is successful, generate a custom Firebase token for the username and send it back in the response. Here's how you can do it:

app.post('/login', (req, res) => {
  const username = req.body.username;
  const password = req.body.password;

  ldapClient.bind(username, password, (bindError) => {
    if (bindError) {
      res.status(401).send({ error: 'LDAP Binding Failed' });
    } else {
      admin.auth().createCustomToken(username)
      .then((customToken) => res.send({ firebaseToken: customToken }))
      .catch((tokenError) => res.status(401).send({ error: 'Token Generation Failed' }));
    }
  });
});

Just a heads-up, in production applications, be extra careful with sensitive data to avoid exposing passwords or tokens.

First, run your server with node index.js in the terminal. Then, send a POST request to 'http://localhost:3000/login' with the LDAP username and password. If everything goes well, the server will respond with a Firebase token that you can use in a Firebase client application.