auth_controller.js

var request = require('request');

AuthController.twitterReverseAuth = function() {
  var self = this;
  
  request.post({
      url: 'https://api.twitter.com/oauth/request_token'
    , oauth: { 
          consumer_key: self.app.set('twitter client key')
        , consumer_secret: self.app.set('twitter client secret')
      }
    , form: { 
          x_auth_mode: 'reverse_auth'
      }
  }, function (err, r, body) {
    if (err) {
      return self.response.send(500, { message: e.message });
    }
    
    if (body.indexOf('OAuth') !== 0) {
      return self.response.send(500, { message: 'Malformed response from Twitter' });
    }
    
    self.response.send({ x_reverse_auth_parameters: body });
  });
};

express.js

var request = require('request');

app.post('/auth/twitter/reverse', function(req, res) {
  var self = this;
  
  request.post({
      url: 'https://api.twitter.com/oauth/request_token'
    , oauth: { 
          consumer_key: app.set('twitter client key')
        , consumer_secret: app.set('twitter client secret')
      }
    , form: { 
          x_auth_mode: 'reverse_auth'
      }
  }, function (err, r, body) {
    if (err) {
      return res.send(500, { message: e.message });
    }
    
    if (body.indexOf('OAuth') !== 0) {
      return res.send(500, { message: 'Malformed response from Twitter' });
    }
    
    res.send({ x_reverse_auth_parameters: body });
  });
};