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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.jna;

import java.nio.ByteBuffer;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.util.Properties;
import java.util.Random;

import org.apache.commons.crypto.random.CryptoRandom;
import org.apache.commons.crypto.utils.Utils;

import com.sun.jna.NativeLong;
import com.sun.jna.ptr.PointerByReference;


OpenSSL secure random using JNA. 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 JNA. 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 OpenSslJnaCryptoRandom extends Random implements CryptoRandom {
    private static final long serialVersionUID = -7128193502768749585L;
    private final boolean rdrandEnabled;
    private PointerByReference rdrandEngine;

    
Constructs a OpenSslJnaCryptoRandom. 
Params:
props – the configuration properties (not used)
Throws:
GeneralSecurityException –  if could not enable JNA access/**
     * Constructs a {@link OpenSslJnaCryptoRandom}.
     *
     * @param props the configuration properties (not used)
     * @throws GeneralSecurityException  if could not enable JNA access
     */
    public OpenSslJnaCryptoRandom(Properties props) //NOPMD
            throws GeneralSecurityException {
        if (!OpenSslJna.isEnabled()) {
            throw new GeneralSecurityException("Could not enable JNA access", OpenSslJna.initialisationError());
        }

        boolean rdrandLoaded = false;
        try {
            OpenSslNativeJna.ENGINE_load_rdrand();
            rdrandEngine = OpenSslNativeJna.ENGINE_by_id("rdrand");
            int ENGINE_METHOD_RAND = 0x0008;
            if(rdrandEngine != null) {
                int rc = OpenSslNativeJna.ENGINE_init(rdrandEngine);
                
                if(rc != 0) {
                    int rc2 = OpenSslNativeJna.ENGINE_set_default(rdrandEngine, ENGINE_METHOD_RAND);
                    if(rc2 != 0) {
                        rdrandLoaded = true;
                    }
                }
            }
            
        } catch (Exception e) {
            throw new NoSuchAlgorithmException();
        }
        
        rdrandEnabled = rdrandLoaded;
        
        if(!rdrandLoaded) {
            closeRdrandEngine();
        }
    }

    
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) {
        
        synchronized (OpenSslJnaCryptoRandom.class) {
            //this method is synchronized for now
            //to support multithreading https://wiki.openssl.org/index.php/Manual:Threads(3) needs to be done
            
            if(rdrandEnabled && OpenSslNativeJna.RAND_get_rand_method().equals(OpenSslNativeJna.RAND_SSLeay())) {
                close();
                throw new RuntimeException("rdrand should be used but default is detected");
            }
            
            ByteBuffer buf = ByteBuffer.allocateDirect(bytes.length);
            int retVal = OpenSslNativeJna.RAND_bytes(buf, bytes.length);
            throwOnError(retVal);
            buf.rewind();
            buf.get(bytes,0, bytes.length);
        }
    }

    
Overrides OpenSslJnaCryptoRandom. For OpenSslJnaCryptoRandom, we don't need to set seed. 
Params:
seed – the initial seed./**
     * Overrides {@link OpenSslJnaCryptoRandom}. For {@link OpenSslJnaCryptoRandom},
     * 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(). Closes OpenSSL context if native enabled. /**
     * Overrides {@link java.lang.AutoCloseable#close()}. Closes OpenSSL context
     * if native enabled.
     */
    @Override
    public void close() {
        closeRdrandEngine();
        OpenSslNativeJna.ENGINE_cleanup();
        
        //cleanup locks
        //OpenSslNativeJna.CRYPTO_set_locking_callback(null);
        //LOCK.unlock();
    }

    
Closes the rdrand engine.
/**
     * Closes the rdrand engine.
     */
    private void closeRdrandEngine() {
        
        if(rdrandEngine != null) {
            OpenSslNativeJna.ENGINE_finish(rdrandEngine);
            OpenSslNativeJna.ENGINE_free(rdrandEngine);
        }
    }

    
Checks if rdrand engine is used to retrieve random bytes
Returns:
true if rdrand is used, false if default engine is used/**
     * Checks if rdrand engine is used to retrieve random bytes
     * 
     * @return true if rdrand is used, false if default engine is used
     */
    public boolean isRdrandEnabled() {
        return rdrandEnabled;
    }

    
Params:
retVal – the result value of error./**
     * @param retVal the result value of error.
     */
    private void throwOnError(int retVal) {  
        if (retVal != 1) {
            NativeLong err = OpenSslNativeJna.ERR_peek_error();
            String errdesc = OpenSslNativeJna.ERR_error_string(err, null);
            close();
            throw new RuntimeException("return code " + retVal + " from OpenSSL. Err code is " + err + ": " + errdesc);
        }
    }
}