Passport-cas2总是重定向到failureRedirect

我对Node.js很陌生，我正试图通过外部CAS服务器实现身份验证系统。我正在使用Passport.js + passport-cas2，但它总是将我重定向到failureRedirect页面，即使CAS正确地对我进行了身份验证。下面是我的代码:

var SocketIOFileUpload = require('socketio-file-upload'),
    socketio           = require('socket.io'),
    express            = require('express'),
    path               = require('path'),
    express            = require('express'),
    passport           = require('passport'),
    session            = require('express-session'),
    bodyParser         = require('body-parser');
var CasStrategy = require('passport-cas2').Strategy;
var cas = new CasStrategy({
       casURL: 'https://my.cas.server'
    }, 
    function(username, profile, done) {
        console.log("authenticating");
        done(null, new User());
});
var app = express()
     .use(bodyParser.urlencoded({ extended: true }))
     .use(SocketIOFileUpload.router)
     .use(passport.initialize());
passport.use(cas);
app.use(session({ secret: 'my secret phrase' }))
    .use(passport.session())
    .get('/', function(req, res){
         res.redirect('/auth/cas');
     })
    .get('/auth/cas',
      passport.authenticate('cas', { failureRedirect: '/error', successRedirect: '/upload' }),
      function(req, res) {
        // Successful.
        res.redirect('/upload');
    })
    .use('/upload', function(req, res, next){
        if (req.user)
            return express.static(path.join(__dirname, 'html'));
        else
            res.redirect('/auth/cas');
    })
    .get('/error', function(req, res) {
        res.send('Error in authentication. Please <a href="/auth/cas">Try Again</a>.');
    })
    .listen(8080, function () {
    console.log('Upload Server started on http://localhost:8080');
    });

console.log("authenticating")根本就没有被执行!

谢谢你的帮助。