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
5package org.chromium.chromoting;
6
7import java.io.FileInputStream;
8import java.io.IOException;
9import 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 */
16public 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}
42