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8463ed9 Mar 20, 2018
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#!/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 Metasm! Also allows to get
# friendly output from a GAS assembler source code file.
#
#
# 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
gem 'rex-text'
$:.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'
require 'metasm'
#PowerPC, seems broken for now in metasm
#@Arch = ['Ia32','MIPS','PowerPC','ARM','X86_64']
@Arch = ['Ia32','MIPS','ARM','X86_64']
@Endian = ['little','big']
@architecture = ""
@endianess = ""
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(/\, $/,'')})"],
"-e" => [ true, "The endianess to encode as (#{@Endian.sort.collect{|a| a + ', ' }.join.gsub(/\, $/,'')})" ],
"-h" => [ false, "Display this help information" ])
$args.parse(ARGV) { |opt, idx, val|
case opt
when "-a"
found = nil
@Arch.each { |a|
if val.downcase == a.downcase
@architecture = a
found = true
end
}
usage if not found
when "-e"
found = nil
@Endian.each { |e|
if val.downcase == e.downcase
@endianess = e
found = true
end
}
usage if not found
when "-h"
usage
else
usage
end
}
unless @architecture.empty?
if @endianess.empty?
String.class_eval("@@cpu = Metasm::#{@architecture}.new")
else
String.class_eval("@@cpu = Metasm::#{@architecture}.new(:#{@endianess})")
end
end
class String
@@cpu ||= Metasm::Ia32.new
class << self
def cpu() @@cpu end
def cpu=(c) @@cpu=c end
end
# encodes the current string as a Shellcode, returns the resulting EncodedData
def metasm_encode_edata
s = Metasm::Shellcode.assemble @@cpu, self
s.encoded
end
# encodes the current string as a Shellcode, returns the resulting binary String
# outputs warnings on unresolved relocations
def metasm_encode
ed = metasm_encode_edata
if not ed.reloc.empty?
puts 'W: encoded string has unresolved relocations: ' + ed.reloc.map { |o, r| r.target.inspect }.join(', ')
end
ed.fill
ed.data
end
# decodes the current string as a Shellcode, with specified base address
# returns the resulting Disassembler
def metasm_decode_blocks(base_addr=0, eip=base_addr)
sc = Metasm::Shellcode.metasm_decode(self, @@cpu)
sc.base_addr = base_addr
sc.metasm_disassemble(eip)
end
# decodes the current string as a Shellcode, with specified base address
# returns the asm source equivallent
def metasm_decode(base_addr=0, eip=base_addr)
metasm_decode_blocks(base_addr, eip).to_s
end
def metasm_disassemble(str, eip=0)
Metasm::Shellcode.metasm_disassemble(@@cpu, str, eip)
end
end
def parse_gas_file(filename)
filename = File.expand_path(filename)
unless ::File.exist?(filename)
puts "File #{filename} not found"
return
end
shellcode = ""
puts "Reading file #{filename}"
::File.open(filename, "rb") do |f|
f.each_line do |l|
l.gsub!(/#.*$/, "") # Delete comments
l.gsub!(/@.*$/, "") # Delete comments
l.gsub!(/\..*$/, "") # Delete directives
l.gsub!(/(\r|\n)/, '') # Delete newlines... just in case...
next if l.strip.empty?
shellcode << "#{l}\n"
end
end
begin
encoded = shellcode.metasm_encode
puts Rex::Text.to_ruby(encoded)
puts encoded.metasm_disassemble(shellcode.metasm_encode)
rescue Metasm::Exception => e
puts "Error: #{e.class} #{e.message}"
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',
'type "file <file>" to parse a GAS assembler source file',
'']
shell.run { |l|
l.gsub!(/(\r|\n)/, '')
l.gsub!(/\\n/, "\n")
l.gsub!(';', "\n")
break if %w[quit exit].include? l.chomp
if l.chomp.index(/^file (.*)/)
parse_gas_file($1)
next
end
next if l.strip.empty?
begin
l = l.metasm_encode
puts '"' + l.unpack('C*').map { |c| '\\x%02x' % c }.join + '"'
rescue Metasm::Exception => e
puts "Error: #{e.class} #{e.message}"
end
}