Manually call passport for authentication

I develop a restful nodeJS API protected by a oauth2 authentication using passport.

  var express = require('express');
    var passport = require('passport');
    var port = process.env.PORT || 8080;
    var app = express();

    app.use(passport.initialize());

    // Create our Express router
    var router = express.Router();
    var creatureController = require('./controllers/creature');

    router.route('/creature').get(passport.authenticate('accessToken', {session: false}), creatureController.getProfile);

In this case, the route is protected and it requires to send a valid token in order to access to the route.

I want to find a way to authenticate my "users" manually, by calling a function, which take the username and password of the user I want to authenticate.

Passport exposes a req.login() function that can be used to login the user manually.

app.post('/login', function (req, res, next) {
    var user = User.findOrCreate(req.body);
    // … your authentication or whatever
    req.login(user, function(err){
        if(err) return next(err);
        res.redirect('/home');
    });
});