Q:

modify password with expressjs mongoose passport-local

First of all, I'm french, and my english is not really good, I do my best :)
I created a local authentification using PassportJs, Mongoose and Expressjs (v3.x). 
It works perfectly.  When the user is logged, in the /account/ space, I created a form to change the current password (3 input : pass, newpass, newpassconfirm).  But after that, I have no idea how to process ...
Do I have to create another passport LocalStrategy to find my user and call a "setPassword" function declared in my Users Schema ? 
Can I maybe do this operation without using passportjs .. ?  If it's possible, how can I get my User access to the database ? 
Here is my code for my authentification that works. 
My /login POST (/routes/user.js)
app.post('/login', function(req, res, next) {
    passport.authenticate('local-login', function(err, user, info) {
        if (err) { 
            return next(err); 
        }

        if (! user) { 
            return res.redirect('/login'); 
        }

        req.logIn(user, function(err) {
            if (err) { 
                return next(err); 
            }

            req.session.pseudo = user.pseudo;
            return res.redirect('/');
        });
    })(req, res, next);
});

My passport script (/script/passport.js)
passport.use('local-login', new LocalStrategy({
    usernameField : 'pseudo',
    passwordField : 'pass',
    passReqToCallback : true // permet de passer l'objet req dans le callback
}, function (req, pseudo, pass, done) {
    Users.findOne({ 'pseudo': pseudo }, function (err, user) {
        if (err) { 
            return done(err); 
        }
        if (! user) { 
            return done(null, false, req.flash('loginMessage', 'Cet utilisateur n\'existe pas.')); 
        }
        if (! user.verifyPassword(pass)) { 
            return done(null, false, req.flash('loginMessage', 'Mot de passe incorrect.'));  
        }
        return done(null, user);
    });
}));

My User Schema (/models/db_Users.js)
var mongoose = require('mongoose');
var bcrypt   = require('bcrypt-nodejs');

// Schema de la collection User
var usersSchema = mongoose. Schema({
    pseudo: String,
    pass: String,
    admin: Boolean,
}, 
{
    collection: 'Users' 
});

usersSchema.methods.generateHash = function(password) {
    return bcrypt.hashSync(password, bcrypt.genSaltSync(8), null);
};

usersSchema.methods.verifyPassword = function(password) {
    return bcrypt.compareSync(password, this.pass);
};

module.exports = mongoose.model('Users', usersSchema);

the /changepass POST where I have issues (/routes/users.js)
app.post('/changepass' , function (req, res, next) {
    //console.log(req.body.pass, req.body.newpass, req.body.newpassconfirm);

    // Should I call another passport LocalStrategy to acces to my User and set the new password here ? 

    res.redirect('/account');
});

You can find all the project here, if you have questions about the structure of my app : https://github.com/tibaldev/docu
Thanks for your help ! 

A:

/models/db_Users.js
// bcrypt middleware
usersSchema.pre('save', function(next){
    var user = this;

    //check if password is modified, else no need to do anything
    if (! user.isModified('pass')) {
       return next()
    }

    user.pass = bcrypt.hashSync(password, bcrypt.genSaltSync(8), null);
    next()
})

Inside your routes/users.js
var User = require('mongoose').model('Users')

app.post('/changepass' , function (req, res, next) {
     if (newpass ! == newpassconfirm) {
        throw new Error('password and confirm password do not match');
     }

     var user = req.user;

     user.pass = newpass;

     user.save(function(err){
         if (err) { next(err) }
         else {
             res.redirect('/account');
         }
     })
});

