node passport的问题

var express=require("express");
var cookieParser=require("cookie-parser");
var session=require("express-session");
var passport=require("passport");
var LocalStrategy=require("passport-local").Strategy;

var app=new express();

app.use(cookieParser());
app.use(session({ secret: 'keyboard cat' , resave: false, saveUninitialized: false}));

app.use(passport.initialize());
app.use(passport.session());




passport.use(new LocalStrategy(
    function(username, password, cb) {
        console.log(";kflasjfaskfjas");
      var username_details="a",password_details="b";
        if (username!==username_details){
            console.log("1");
            return cb(null,false);
        }
        if (password!==password_details) {
            console.log("2");
            return cb(null, false);
        }
        console.log(user);
        return cb(null,user);
    }));

app.post('/login',function(req,res,next){
        var post="";
        req.on("data",function(chunk){
            post+=chunk;
        });
        req.on("end",function (){
            console.log(util.inspect(querystring.parse(post)));
            next();
        })
    },
    passport.authenticate('local',
        {
            successRedirect: '/',
            failureRedirect: '/login'
        })
);



var server=app.listen(9000,function (){
    console.log("the web is start");
});

为什么用户名密码输入正确也无法登陆？？？passport 是这么使用吗？
passport.use(new LocalStrategy(

function(username, password, cb) {
    console.log(";kflasjfaskfjas");
  var username_details="a",password_details="b";
    if (username!==username_details){
        console.log("1");
        return cb(null,false);
    }
    if (password!==password_details) {
        console.log("2");
        return cb(null, false);
    }
    console.log(user);
    return cb(null,user);
}));
压根就没有执行

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各位求教了，谢谢