Android Open Source - bitfynd-wallet-android Linux Secure Random

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * Copyright 2013 Google Inc.//from w  w  w.  j ava 2  s  .  com
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package de.schildbach.wallet.util;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.security.Provider;
import java.security.SecureRandomSpi;
import java.security.Security;

/**
 * A SecureRandom implementation that is able to override the standard JVM provided implementation, and which simply
 * serves random numbers by reading /dev/urandom. That is, it delegates to the kernel on UNIX systems and is unusable on
 * other platforms. Attempts to manually set the seed are ignored. There is no difference between seed bytes and
 * non-seed bytes, they are all from the same source.
 */
public class LinuxSecureRandom extends SecureRandomSpi
{
  private static final FileInputStream urandom;

  private static class LinuxSecureRandomProvider extends Provider
  {
    public LinuxSecureRandomProvider()
    {
      super("LinuxSecureRandom", 1.0, "A Linux specific random number provider that uses /dev/urandom");
      put("SecureRandom.LinuxSecureRandom", LinuxSecureRandom.class.getName());
    }
  }

  static
  {
    try
    {
      File file = new File("/dev/urandom");
      if (file.exists())
      {
        // This stream is deliberately leaked.
        urandom = new FileInputStream(file);
        // Now override the default SecureRandom implementation with this one.
        Security.insertProviderAt(new LinuxSecureRandomProvider(), 1);
      }
      else
      {
        urandom = null;
      }
    }
    catch (FileNotFoundException e)
    {
      // Should never happen.
      throw new RuntimeException(e);
    }
  }

  private final DataInputStream dis;

  public LinuxSecureRandom()
  {
    // DataInputStream is not thread safe, so each random object has its own.
    dis = new DataInputStream(urandom);
  }

  @Override
  protected void engineSetSeed(byte[] bytes)
  {
    // Ignore.
  }

  @Override
  protected void engineNextBytes(byte[] bytes)
  {
    try
    {
      dis.readFully(bytes); // This will block until all the bytes can be read.
    }
    catch (IOException e)
    {
      throw new RuntimeException(e); // Fatal error. Do not attempt to recover from this.
    }
  }

  @Override
  protected byte[] engineGenerateSeed(int i)
  {
    byte[] bits = new byte[i];
    engineNextBytes(bits);
    return bits;
  }
}

Java Source Code List

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