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/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.commons.crypto.random; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.util.Properties; import java.util.Random; import org.apache.commons.crypto.utils.IoUtils;
A Random implementation that uses random bytes sourced from the operating system.
/** * A Random implementation that uses random bytes sourced from the operating * system. */
class OsCryptoRandom extends Random implements CryptoRandom { private static final long serialVersionUID = 6391500337172057900L; private static final int RESERVOIR_LENGTH = 8192; private transient FileInputStream stream; private final byte[] reservoir = new byte[RESERVOIR_LENGTH]; private int pos = reservoir.length;
Fills the reservoir.
Params:
  • min – the length.
/** * Fills the reservoir. * * @param min the length. */
private void fillReservoir(final int min) { if (pos >= reservoir.length - min) { try { IoUtils.readFully(stream, reservoir, 0, reservoir.length); } catch (final IOException e) { throw new IllegalStateException("failed to fill reservoir", e); } pos = 0; } }
Constructs a OsCryptoRandom.
Params:
/** * Constructs a {@link OsCryptoRandom}. * * @param props the configuration properties. * Uses {@link CryptoRandomFactory#DEVICE_FILE_PATH_KEY} to determine the * path to the random device, default is * {@link CryptoRandomFactory#DEVICE_FILE_PATH_DEFAULT} */
// N.B. this class is not public/protected so does not appear in the main Javadoc // Please ensure that property use is documented in the enum CryptoRandomFactory.RandomProvider public OsCryptoRandom(final Properties props) { final File randomDevFile = new File( props.getProperty(CryptoRandomFactory.DEVICE_FILE_PATH_KEY, CryptoRandomFactory.DEVICE_FILE_PATH_DEFAULT)); try { close(); this.stream = new FileInputStream(randomDevFile); } catch (final IOException e) { throw new IllegalArgumentException(e); } try { fillReservoir(0); } catch (final IllegalStateException e) { close(); throw e; } }
Overrides CryptoRandom.nextBytes(byte[]). Generates random bytes and places them into a user-supplied byte array. The number of random bytes produced is equal to the length of the byte array.
Params:
  • bytes – the array to be filled in with random bytes.
/** * Overrides {@link CryptoRandom#nextBytes(byte[])}. Generates random bytes * and places them into a user-supplied byte array. The number of random * bytes produced is equal to the length of the byte array. * * @param bytes the array to be filled in with random bytes. */
@Override synchronized public void nextBytes(final byte[] bytes) { int off = 0; int n = 0; while (off < bytes.length) { fillReservoir(0); n = Math.min(bytes.length - off, reservoir.length - pos); System.arraycopy(reservoir, pos, bytes, off, n); off += n; pos += n; } }
Overrides Random#next(). Generates the next pseudorandom number. Subclasses should override this, as this is used by all other methods.
Params:
  • nbits – random bits.
Returns:the next pseudorandom value from this random number generator's sequence.
/** * Overrides Random#next(). Generates the next pseudorandom number. * Subclasses should override this, as this is used by all other methods. * * @param nbits random bits. * @return the next pseudorandom value from this random number generator's * sequence. */
@Override synchronized protected int next(final int nbits) { fillReservoir(4); int n = 0; for (int i = 0; i < 4; i++) { n = (n << 8) | (reservoir[pos++] & 0xff); } return n & (0xffffffff >> (32 - nbits)); }
Overrides AutoCloseable.close(). Closes the OS stream.
/** * Overrides {@link java.lang.AutoCloseable#close()}. Closes the OS stream. */
@Override synchronized public void close() { if (stream != null) { IoUtils.closeQuietly(stream); stream = null; } } }