[nodejs] hackathon-starter using Lusca - where is csrf value being calculated/stored?

Hi ,

I'm very new to Node so please forgive me if this is a noob question. I'm
trying to use convert this project on github over to use ejs views , but
struggling to understand how they're creating the csrf token.

Seed project I'm using -
https://github.com/sahat/hackathon-starter

Uses lusca for csrf generation
https://github.com/krakenjs/lusca


The code I'm seeing in their seed proejct (at least what I think is
relevant)

var csrf = require('lusca').csrf();

/**
  * CSRF whitelist.
  */

//app.js
var csrfExclude = ['/url1', '/url2'];

//original project uses jade
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade'); //i'm going to change this to ejs, but
don't know where to get the csrf value(below) from

app.use(function(req, res, next) {
   // CSRF protection.
   if (_.contains(csrfExclude, req.path)) return next();
   csrf(req, res, next);
});
app.use(function(req, res, next) {
   // Make user object available in templates.
   res.locals.user = req.user;
   next();
});
app.use(function(req, res, next) {
   // Remember original destination before login.
   var path = req.path.split('/')[1];
   if (/auth|login|logout|signup|fonts|favicon/i.test(path)) {
     return next();
   }
   req.session.returnTo = req.path;
   next();
});

//route controllers
app.get('/', homeController.index);



//in separate controller file - home.js

exports.index = function(req, res) {
   res.render('home', {
     title: 'Home'
   });
};


//inside their jade file - this is converted to html tag --- <meta
name="csrf-token" content="cRcgih7Vl1Ms2Xz0zgIeAyWwQm6s4kp3/8OS4=">
meta(name='csrf-token', content=_csrf)

//so value _csrf is converted to cRcgih7Vl1Ms2Xz0zgIeAyWwQm6s4kp3/8OS4=

My confusion is where is the _csrf tag being pulled from? I tried to grep
that keywork through all the files and don't actually see it set anywhere
(might be missing something?). I'm looking through my inspector and able
to see that a session variable is set req.session._csrfSecret =
nLzJqL3YIAJVzA== , but this doesn't look to be the same key as used above.
  Based on the /8OS4 I'm thinking the value is actually concatenated
somewhere.

My question is - in the jade template, where does this _csrf value come
from? I don't see where jade is grabbing it from in the js code anywhere
(I don't see _csrf set in the response anywhere).

Or what's the normal way to create and persist the csrf value using lusca?


Thanks for any help!