auth.js

var users = require('./models/users');
var Strategy = require('passport-local').Strategy;

module.exports = function(mongoose, passport){
    var Users = mongoose.model('Users', users.usersSchema);

    // Configure the local strategy for use by Passport.
    //
    // The local strategy require a `verify` function which receives the credentials
    // (`username` and `password`) submitted by the user.  The function must verify
    // that the password is correct and then invoke `cb` with a user object, which
    // will be set at `req.user` in route handlers after authentication.
    passport.use(new Strategy(
        function(username, password, cb) {
        Users.find({username:username}, function(err, user) {
            if (err) { return cb(err); }
            if (!user) { return cb(null, false); }
            if (user.password != password) { return cb(null, false); }
            return cb(null, user);
        });
    }));


    // Configure Passport authenticated session persistence.
    //
    // In order to restore authentication state across HTTP requests, Passport needs
    // to serialize users into and deserialize users out of the session.  The
    // typical implementation of this is as simple as supplying the user ID when
    // serializing, and querying the user record by ID from the database when
    // deserializing.
    passport.serializeUser(function(user, cb) {
        cb(null, user.id);
    });

    passport.deserializeUser(function(id, cb) {
        Users.findById(id, function (err, user) {
            if (err) { return cb(err); }
            cb(null, user);
        });
    });

}