Set the path to return to after a successful authentication in Passport.js GitHub strategy (Express.js).

passportjs-github-returnto.js

/**
 * Part 1: Set up the authentication endpoints.
 */

// Point 1: Notice the checkReturnTo middleware, is defined at the bottom.
app.get('/auth/github', checkReturnTo, passport.authenticate('github', {state: 'Bublifuk'}));

// Point 2: Use 'successReturnToOrRedirect', otherwise the middleware will not work.
app.get('/auth/github/callback',
  passport.authenticate('github', { successReturnToOrRedirect: '/', // IMPORTANT!
                                    failureRedirect: '/error/account-not-found'}));

/**
 * Part 2: The middleware to set up the parameters for Passport.js
 */

var querystring = require('querystring');

// The middleware to set up the parameters for the authenticate middleware.
function checkReturnTo(req, res, next) {
  var returnTo = req.query['returnTo'];
  if (returnTo) {
    // Maybe unnecessary, but just to be sure.
    req.session = req.session || {};
    
    // Set returnTo to the absolute path you want to be redirect to after the authentication succeeds.
    req.session.returnTo = getFullUrl(querystring.unescape(returnTo));
  }
  next();
}

/**
 * Part 3: Usage
 */

// Restrict the important paths in your app using middleware.
// Just adding restrictTo('authenticated') will do the job.
function restrictTo(roles) {
  if (roles === 'authenticated') return function (req, res, next) {
    if (req.isAuthenticated()) return next();
    else res.redirect('/auth/github?returnTo=' + querystring.escape(req.url));
  };
  else return function(req, res, next) {
    next();
  };
}