LibreChat/api/server/routes/auth.js

const express = require('express');
const router = express.Router();
const authYourLogin = require('./authYourLogin');
const userSystemEnabled = process.env.ENABLE_USER_SYSTEM || false

router.get('/login', function (req, res) {
  if (userSystemEnabled)
    res.redirect('/auth/your_login_page')
  else
    res.redirect('/')  
})
  
router.get('/logout', function (req, res) {
  // clear the session
  req.session.user = null

  req.session.save(function (error) {
    if (userSystemEnabled)
      res.redirect('/auth/your_login_page/logout')
    else
      res.redirect('/') 
  })  
})

const authenticatedOr401 = (req, res, next) => {
  if (userSystemEnabled) {
    const user = req?.session?.user;

    if (user) next();
    else res.status(401).end();
  } else next();
}

const authenticatedOrRedirect = (req, res, next) => {
  if (userSystemEnabled) {
    const user = req?.session?.user;

    if (user) next();
    else res.redirect('/auth/login').end();
  } else next();
}

if (userSystemEnabled)
  router.use('/your_login_page', authYourLogin);

module.exports = { router, authenticatedOr401, authenticatedOrRedirect };