Example code for my blog post "The TOCTTOU attack", available at http://out-println.appspot.com/posts/tocttou.

Tocttou.java

import java.util.Date;

/**
 * Example code for my blog post "The TOCTTOU attack", available at http://out-println.appspot.com/posts/tocttou.
 */
public class Tocttou {
  
  public static final class Interval {
    
    private final Date min;
    private final Date max;
    
    public Interval(final Date min, final Date max) {
      if (min.after(max)) {
        throw new IllegalArgumentException();
      }
      this.min = (Date) min.clone();
      this.max = (Date) max.clone();
    }

    public Date min() { return (Date) min.clone(); }
    public Date max() { return (Date) max.clone(); }
  }

  public static class Attacker {
    volatile Date max = new Date();
    
    final Thread burglar = new Thread() {
      @Override public void run() {
        max.setTime(0);
      }
    };
    
    public Interval attack() {
      Date min = new Date();
      max.setTime(min.getTime());
      burglar.start();
      try {
        Interval i = new Interval(min, max);
        if (i.min().after(i.max())) {
          System.out.println("Success!");
          return i;
        } else System.out.println("Too late");
      }
      catch (final IllegalArgumentException e) {
        System.out.println("Too soon");
      }
      return null;
    }
  }

  public static void main(final String[] args) {
    Interval corrupted;
    long start = System.currentTimeMillis();
    int count = 0;
    while ((corrupted = (new Attacker()).attack()) == null) count += 1;

    System.out.println("In " + (System.currentTimeMillis() - start) + " ms and " +
      count + " attacks, I have created a corrupt interval with min=" +
      corrupted.min() + " and max=" + corrupted.max());
  }
}