remoting/android/java/src/org/chromium/chromoting/SecureRandomInitializer.java

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 package org.chromium.chromoting;
   6
   7 import java.io.FileInputStream;
   8 import java.io.IOException;
   9 import java.security.SecureRandom;
  10
  11 /**
  12  * This class contains code to initialize a SecureRandom generator securely on Android platforms
  13  * <= 4.3. See
  14  * {@link http://android-developers.blogspot.com/2013/08/some-securerandom-thoughts.html}.
  15  */
  16 public class SecureRandomInitializer {
  17     private static final int NUM_RANDOM_BYTES = 16;
  18
  19     /**
  20      * Safely initializes the random number generator, by seeding it with data from /dev/urandom.
  21      */
  22     public static void initialize(SecureRandom generator) throws IOException {
  23         FileInputStream fis = null;
  24         try {
  25             fis = new FileInputStream("/dev/urandom");
  26             byte[] bytes = new byte[NUM_RANDOM_BYTES];
  27             if (bytes.length != fis.read(bytes)) {
  28                 throw new IOException("Failed to get enough random data.");
  29             }
  30             generator.setSeed(bytes);
  31         } finally {
  32             try {
  33                 if (fis != null) {
  34                     fis.close();
  35                 }
  36             } catch (IOException e) {
  37                 // Ignore exception closing the device.
  38             }
  39         }
  40     }
  41 }