[ExpDev] Polymorphic Shellcode

What is Polymorphism?

The polymorphism means the ability of an object to take on many forms. In computer science, the term polymorphism also means the ability of different objects/codes to respond in a unique way to the same functionality.

Shellcode Selection

I will use the following shellcode from the Shell-Storm to demonstrate the polymorphic shellcode:

• sys_exit(0) — http://shell-storm.org/shellcode/files/shellcode-623.php
• /bin/sh — http://shell-storm.org/shellcode/files/shellcode-752.php
• /bin/cat /etc/passwd — http://shell-storm.org/shellcode/files/shellcode-571.php

1) sys_exit(0)

The original shellcode from the Shell-Storm is as following:

/*
Name   : 8 bytes sys_exit(0) x86 linux shellcode
Date   : may, 31 2010
Author : gunslinger_
Web    : devilzc0de.com
blog   : gunslinger.devilzc0de.com
tested on : linux debian
*/
char *bye=
 "\x31\xc0"                    /* xor    %eax,%eax */
 "\xb0\x01"                    /* mov    $0x1,%al */
 "\x31\xdb"                    /* xor    %ebx,%ebx */
 "\xcd\x80";                   /* int    $0x80 */
int main(void)
{
		((void (*)(void)) bye)();
		return 0;
}