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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.security.GeneralSecurityException;
import java.util.Properties;
import java.util.Random;

import org.apache.commons.crypto.Crypto;
import org.apache.commons.crypto.utils.Utils;


OpenSSL secure random using JNI. This implementation is thread-safe.


If using an Intel chipset with RDRAND, the high-performance hardware random
number generator will be used and it's much faster than SecureRandom. If
RDRAND is unavailable, default OpenSSL secure random generator will be used.
It's still faster and can generate strong random bytes.

See Also:

 *      https://wiki.openssl.org/index.php/Random_Numbers

 *      http://en.wikipedia.org/wiki/RdRand/**
 * <p>
 * OpenSSL secure random using JNI. This implementation is thread-safe.
 * </p>
 *
 * <p>
 * If using an Intel chipset with RDRAND, the high-performance hardware random
 * number generator will be used and it's much faster than SecureRandom. If
 * RDRAND is unavailable, default OpenSSL secure random generator will be used.
 * It's still faster and can generate strong random bytes.
 * </p>
 *
 * @see <a href="https://wiki.openssl.org/index.php/Random_Numbers">
 *      https://wiki.openssl.org/index.php/Random_Numbers</a>
 * @see <a href="http://en.wikipedia.org/wiki/RdRand">
 *      http://en.wikipedia.org/wiki/RdRand</a>
 */
class OpenSslCryptoRandom extends Random implements CryptoRandom {
    private static final long serialVersionUID = -7828193502768789584L;

    private static final boolean nativeEnabled;

    private static final Throwable initException;

    static {
        boolean opensslLoaded = false;
        Throwable except = null;
        if (Crypto.isNativeCodeLoaded()) {
            try {
                OpenSslCryptoRandomNative.initSR();
                opensslLoaded = true;
            } catch (Exception t) {
                except = t;
            } catch (UnsatisfiedLinkError t) {
                except = t;
            }
        }
        nativeEnabled = opensslLoaded;
        initException = except;
    }

    
Judges whether native library was successfully loaded and initialised.
Returns:
true if library was loaded and initialised/**
     * Judges whether native library was successfully loaded and initialised.
     *
     * @return true if library was loaded and initialised
     */
    public static boolean isNativeCodeEnabled() {
        return nativeEnabled;
    }

    
Constructs a OpenSslCryptoRandom. 
Params:
props – the configuration properties - not used
Throws:
GeneralSecurityException – if the native library could not be initialised successfully/**
     * Constructs a {@link OpenSslCryptoRandom}.
     *
     * @param props the configuration properties - not used
     * @throws GeneralSecurityException if the native library could not be initialised successfully
     */
    // 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 OpenSslCryptoRandom(Properties props) throws GeneralSecurityException { // NOPMD
        if (!nativeEnabled) {
            if (initException != null) {
                throw new GeneralSecurityException("Native library could not be initialised", initException);
            }
            throw new GeneralSecurityException("Native library is not loaded");
        }
        // Check that nextRandBytes works (is this really needed?)
        if (!OpenSslCryptoRandomNative.nextRandBytes(new byte[1])) {
            throw new GeneralSecurityException("Check of nextRandBytes failed");
        }
    }

    
Generates a user-specified number of random bytes. It's thread-safe.
Params:
bytes – the array to be filled in with random bytes./**
     * Generates a user-specified number of random bytes. It's thread-safe.
     *
     * @param bytes the array to be filled in with random bytes.
     */
    @Override
    public void nextBytes(byte[] bytes) {
        // Constructor ensures that native is enabled here
        if (!OpenSslCryptoRandomNative.nextRandBytes(bytes)) {
            // Assume it's a problem with the argument, rather than an internal issue
            throw new IllegalArgumentException("The nextRandBytes method failed");
        }
    }

    
Overrides OpenSslCryptoRandom. For OpenSslCryptoRandom, we don't need to set seed. 
Params:
seed – the initial seed./**
     * Overrides {@link OpenSslCryptoRandom}. For {@link OpenSslCryptoRandom},
     * we don't need to set seed.
     *
     * @param seed the initial seed.
     */
    @Override
    public void setSeed(long seed) {
        // Self-seeding.
    }

    
Overrides Random#next(). Generates an integer containing the
user-specified number of random bits(right justified, with leading
zeros).
Params:
numBits – number of random bits to be generated, where 0 <= numBits <= 32.
Returns:
int an int containing the user-specified number of
        random bits (right justified, with leading zeros)./**
     * Overrides Random#next(). Generates an integer containing the
     * user-specified number of random bits(right justified, with leading
     * zeros).
     *
     * @param numBits number of random bits to be generated, where 0
     *        {@literal <=} <code>numBits</code> {@literal <=} 32.
     * @return int an <code>int</code> containing the user-specified number of
     *         random bits (right justified, with leading zeros).
     */
    @Override
    final protected int next(int numBits) {
        Utils.checkArgument(numBits >= 0 && numBits <= 32);
        int numBytes = (numBits + 7) / 8;
        byte b[] = new byte[numBytes];
        int next = 0;

        nextBytes(b);
        for (int i = 0; i < numBytes; i++) {
            next = (next << 8) + (b[i] & 0xFF);
        }

        return next >>> (numBytes * 8 - numBits);
    }

    
Overrides AutoCloseable.close(). Does nothing. /**
     * Overrides {@link java.lang.AutoCloseable#close()}.
     * Does nothing.
     */
    @Override
    public void close() {
    }
}