#!/usr/bin/env ruby
#
# $Id$
#
# This tool provides an easy way to see what opcodes are associated with
# certain x86 instructions by making use of Metasm!
#
#
# $Revision$
#

#    This file is part of Metasm, the Ruby assembly manipulation suite
#    Copyright (C) 2007 Yoann GUILLOT
#
#    Licence is LGPL, see LICENCE in the top-level directory

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 'fastlib'

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

require 'rex'
require 'rex/ui'
require 'metasm'

#PowerPC, seems broken for now in metasm
#@Arch = ['Ia32','MIPS','PowerPC','ARM','X86_64']
@Arch = ['Ia32','MIPS','ARM','X86_64']

def usage
	$stderr.puts("\nUsage: #{$0} <options>\n" + $args.usage)
	exit
end
		
$args = Rex::Parser::Arguments.new(
	"-a" => [ true, "The architecture to encode as (#{@Arch.sort.collect{|a| a + ', ' }.join.gsub(/\, $/,'')})"],
	"-h" => [ false, "Display this help information"	])

$args.parse(ARGV) { |opt, idx, val|
	case opt
	when "-a"
		found = nil
		@Arch.each { |a|
			if val.downcase == a.downcase
				String.class_eval("@@cpu = Metasm::#{a}.new")
				found = true
			end
		}
		usage if not found

	when "-h"
		usage
	else
		usage
	end
}

class String
	@@cpu ||= Metasm::Ia32.new
	class << self
		def cpu()   @@cpu   end
		def cpu=(c) @@cpu=c end
	end

	# encodes the current string as a Shellcode, returns the resulting EncodedData
	def encode_edata
		s = Metasm::Shellcode.assemble @@cpu, self
		s.encoded
	end

	# encodes the current string as a Shellcode, returns the resulting binary String
	# outputs warnings on unresolved relocations
	def encode
		ed = encode_edata
		if not ed.reloc.empty?
			puts 'W: encoded string has unresolved relocations: ' + ed.reloc.map { |o, r| r.target.inspect }.join(', ')
		end
		ed.fill
		ed.data
	end

	# decodes the current string as a Shellcode, with specified base address
	# returns the resulting Disassembler
	def decode_blocks(base_addr=0, eip=base_addr)
		sc = Metasm::Shellcode.decode(self, @@cpu)
		sc.base_addr = base_addr
		sc.disassemble(eip)
	end

	# decodes the current string as a Shellcode, with specified base address
	# returns the asm source equivallent
	def decode(base_addr=0, eip=base_addr)
		decode_blocks(base_addr, eip).to_s
	end
end



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

puts 'type "exit" or "quit" to quit', 'use ";" or "\\n" for newline', ''

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

	break if %w[quit exit].include? l.chomp
	next if l.strip.empty?

	begin
		l = l.encode
		puts '"' + l.unpack('C*').map { |c| '\\x%02x' % c }.join + '"'
	rescue Metasm::Exception => e
		puts "Error: #{e.class} #{e.message}"
	end
}