metasploit-gs/tools/exploit/nasm_shell.rb

#!/usr/bin/env ruby

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

#
# This tool provides an easy way to see what opcodes are associated with
# certain x86 instructions by making use of nasm if it is installed and
# reachable through the PATH environment variable.
#

msfbase = __FILE__
while File.symlink?(msfbase)
  msfbase = File.expand_path(File.readlink(msfbase), File.dirname(msfbase))
end

$:.unshift(File.expand_path(File.join(File.dirname(msfbase), '..', '..', 'lib')))
require 'msfenv'

$:.unshift(ENV['MSF_LOCAL_LIB']) if ENV['MSF_LOCAL_LIB']

require 'rex'
require 'rex/ui'

# Check to make sure nasm is installed and reachable through the user's PATH.
begin
  Rex::Assembly::Nasm.check
rescue RuntimeError
  puts "#{$!}"
  exit
end

bits = ARGV.length > 0 ? ARGV[0].to_i : 32
if ! [16, 32, 64].include?(bits) then
    puts "#{bits} bits not supported"
    exit 1
end

# Start a pseudo shell and dispatch lines to be assembled and then
# disassembled.
shell = Rex::Ui::Text::PseudoShell.new("%bldnasm%clr")
shell.init_ui(Rex::Ui::Text::Input::Stdio.new, Rex::Ui::Text::Output::Stdio.new)

shell.run { |line|
  line.gsub!(/(\r|\n)/, '')
  line.gsub!(/\\n/, "\n")

  break if (line =~ /^(exit|quit)/i)

  begin
    puts(Rex::Assembly::Nasm.disassemble(
      Rex::Assembly::Nasm.assemble(line, bits), bits))
  rescue RuntimeError
    puts "Error: #{$!}"
  end
}