Legacy proof of concept code to extract the shell code of a binary

gistfile1.txt

#!/usr/bin/env python
#-*- coding: UTF-8 -*-
# File: shellCodeExtract.py
# Copyright (c) 2011 by Costas Tyfoxylos
#
# GNU General Public Licence (GPL)
# 
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation; either version 2 of the License, or (at your option) any later
# version.
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
# details.
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
# Place, Suite 330, Boston, MA  02111-1307  USA
#

from subprocess import Popen, PIPE
import sys
import os

__author__ = 'Costas Tyfoxylos <costas.tyf@gmail.com>'
__docformat__ = 'plaintext'
__date__ = '17/05/2011'


class ShellCode(object):
    def __init__(self, filename):
        asm = self.__get_asm(filename)
        if asm:
            self.code, self.text = self.__get_shell_code(asm)

    def __get_asm(self, filename):
        if os.path.isfile(filename):
            objdump = Popen(['which', 'objdump'],
                            stdout=PIPE).stdout.read().strip()
            cmd = [objdump, '-d', fileName]
            asm = Popen(cmd, stdout=PIPE).stdout.read()
            return asm
        else:
            return False

    def __get_shell_code(self, text):
        shell_code = []
        opcodes = []
        shell_code_string = ''
        shell_code_text = ''
        text = text.split('<_start>:')[1].strip()
        for line in text.splitlines():
            code = ''
            current_line = line.lstrip()
            if current_line and '>:' not in current_line:
                bytes = current_line.split(':')[1].split()
                for byte in bytes:
                    try:
                        int(byte,16)
                        shell_code.append(byte)
                    except ValueError:
                        opcodes.append(self.__format_to_size(byte, 6))
                for byte in shell_code:
                    code += r'\x' + byte
                shell_code_text += self.__format_to_size('"' + code + '"', 30) + '\t// ' + ' '.join(opcodes) + '\n'
                shell_code_string += code
                shell_code = []
                opcodes = []
        shell_code_string = '"'+shell_code_string+'"'
        shell_code_text = shell_code_text.splitlines()
        shell_code_text[-1] = shell_code_text[-1].replace('" ', '";')
        shell_code_text = '\n'.join(shell_code_text)
        return shell_code_string, shell_code_text

    def __format_to_size(self, string, length=28):
        spaces = length - len(string)
        string = string + (spaces * ' ') 
        return string


if __name__ == '__main__':
    fileName = sys.argv[1]
    shellCode = ShellCode(fileName)
    if '00' in shellCode.code:
        print 'Beware! Null bytes in shellcode. Please correct.'
    print "\nShellcode text:"
    print shellCode.text
    print "\nShellcode string:"
    print shellCode.code