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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 and up.
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package org.bouncycastle.jcajce.provider.drbg;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.Provider;
import java.security.SecureRandom;
import java.security.SecureRandomSpi;
import java.security.Security;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import org.bouncycastle.crypto.digests.SHA512Digest;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.prng.EntropySource;
import org.bouncycastle.crypto.prng.EntropySourceProvider;
import org.bouncycastle.crypto.prng.SP800SecureRandom;
import org.bouncycastle.crypto.prng.SP800SecureRandomBuilder;
import org.bouncycastle.jcajce.provider.config.ConfigurableProvider;
import org.bouncycastle.jcajce.provider.symmetric.util.ClassUtil;
import org.bouncycastle.jcajce.provider.util.AsymmetricAlgorithmProvider;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.Pack;
import org.bouncycastle.util.Properties;
import org.bouncycastle.util.Strings;
/**
* DRBG Configuration
* org.bouncycastle.drbg.gather_pause_secs - is to stop the entropy collection thread from grabbing all
* available entropy on the system. The original motivation for the hybrid infrastructure was virtual machines
* sometimes produce very few bits of entropy a second, the original approach (which "worked" at least for BC) was
* to just read on the second thread and allow things to progress around it, but it did tend to hog the system
* if other processes were using /dev/random. By default the thread will pause for 5 seconds between 64 bit reads,
* increasing this time will reduce the demands on the system entropy pool. Ideally the pause will be set to large
* enough to allow everyone to work together, but small enough to ensure the provider's DRBG is being regularly
* reseeded.
*
* org.bouncycastle.drbg.entropysource - is the class name for an implementation of EntropySourceProvider.
* For example, one could be provided which just reads directly from /dev/random and the extra infrastructure used here
* could be avoided.
*/
public class DRBG
{
private static final String PREFIX = DRBG.class.getName();
// {"Provider class name","SecureRandomSpi class name"}
private static final String[][] initialEntropySourceNames = new String[][]
{
// Normal JVM
{"sun.security.provider.Sun", "sun.security.provider.SecureRandom"},
// Apache harmony
{"org.apache.harmony.security.provider.crypto.CryptoProvider", "org.apache.harmony.security.provider.crypto.SHA1PRNG_SecureRandomImpl"},
// Android.
{"com.android.org.conscrypt.OpenSSLProvider", "com.android.org.conscrypt.OpenSSLRandom"},
{"org.conscrypt.OpenSSLProvider", "org.conscrypt.OpenSSLRandom"},
};
// Cascade through providers looking for match.
private final static Object[] findSource()
{
for (int t = 0; t < initialEntropySourceNames.length; t++)
{
String[] pair = initialEntropySourceNames[t];
try
{
Object[] r = new Object[]{Class.forName(pair[0]).newInstance(), Class.forName(pair[1]).newInstance()};
return r;
}
catch (Throwable ex)
{
continue;
}
}
return null;
}
private static class CoreSecureRandom
extends SecureRandom
{
CoreSecureRandom(Object[] initialEntropySourceAndSpi)
{
super((SecureRandomSpi)initialEntropySourceAndSpi[1], (Provider)initialEntropySourceAndSpi[0]);
}
}
// unfortunately new SecureRandom() can cause a regress and it's the only reliable way of getting access
// to the JVM's seed generator.
private static SecureRandom createInitialEntropySource()
{
boolean hasGetInstanceStrong = AccessController.doPrivileged(new PrivilegedAction()
{
public Boolean run()
{
try
{
Class def = SecureRandom.class;
return def.getMethod("getInstanceStrong") != null;
}
catch (Exception e)
{
return false;
}
}
});
if (hasGetInstanceStrong)
{
return AccessController.doPrivileged(new PrivilegedAction()
{
public SecureRandom run()
{
try
{
return (SecureRandom)SecureRandom.class.getMethod("getInstanceStrong").invoke(null);
}
catch (Exception e)
{
return createCoreSecureRandom();
}
}
});
}
else
{
return createCoreSecureRandom();
}
}
private static SecureRandom createCoreSecureRandom()
{
if (Security.getProperty("securerandom.source") == null)
{
return new CoreSecureRandom(findSource());
}
else
{
try
{
String source = Security.getProperty("securerandom.source");
return new URLSeededSecureRandom(new URL(source));
}
catch (Exception e)
{
return new CoreSecureRandom(findSource());
}
}
}
private static EntropySourceProvider createEntropySource()
{
final String sourceClass = Properties.getPropertyValue("org.bouncycastle.drbg.entropysource");
return AccessController.doPrivileged(new PrivilegedAction()
{
public EntropySourceProvider run()
{
try
{
Class clazz = ClassUtil.loadClass(DRBG.class, sourceClass);
return (EntropySourceProvider)clazz.newInstance();
}
catch (Exception e)
{
throw new IllegalStateException("entropy source " + sourceClass + " not created: " + e.getMessage(), e);
}
}
});
}
private static SecureRandom createBaseRandom(boolean isPredictionResistant)
{
if (Properties.getPropertyValue("org.bouncycastle.drbg.entropysource") != null)
{
EntropySourceProvider entropyProvider = createEntropySource();
EntropySource initSource = entropyProvider.get(16 * 8);
byte[] personalisationString = isPredictionResistant ? generateDefaultPersonalizationString(initSource.getEntropy())
: generateNonceIVPersonalizationString(initSource.getEntropy());
return new SP800SecureRandomBuilder(entropyProvider)
.setPersonalizationString(personalisationString)
.buildHash(new SHA512Digest(), Arrays.concatenate(initSource.getEntropy(), initSource.getEntropy()), isPredictionResistant);
}
else
{
SecureRandom randomSource = new HybridSecureRandom(); // needs to be done late, can't use static
byte[] personalisationString = isPredictionResistant ? generateDefaultPersonalizationString(randomSource.generateSeed(16))
: generateNonceIVPersonalizationString(randomSource.generateSeed(16));
return new SP800SecureRandomBuilder(randomSource, true)
.setPersonalizationString(personalisationString)
.buildHash(new SHA512Digest(), randomSource.generateSeed(32), isPredictionResistant);
}
}
public static class Default
extends SecureRandomSpi
{
private static final SecureRandom random = createBaseRandom(true);
public Default()
{
}
protected void engineSetSeed(byte[] bytes)
{
random.setSeed(bytes);
}
protected void engineNextBytes(byte[] bytes)
{
random.nextBytes(bytes);
}
protected byte[] engineGenerateSeed(int numBytes)
{
return random.generateSeed(numBytes);
}
}
public static class NonceAndIV
extends SecureRandomSpi
{
private static final SecureRandom random = createBaseRandom(false);
public NonceAndIV()
{
}
protected void engineSetSeed(byte[] bytes)
{
random.setSeed(bytes);
}
protected void engineNextBytes(byte[] bytes)
{
random.nextBytes(bytes);
}
protected byte[] engineGenerateSeed(int numBytes)
{
return random.generateSeed(numBytes);
}
}
public static class Mappings
extends AsymmetricAlgorithmProvider
{
public Mappings()
{
}
public void configure(ConfigurableProvider provider)
{
provider.addAlgorithm("SecureRandom.DEFAULT", PREFIX + "$Default");
provider.addAlgorithm("SecureRandom.NONCEANDIV", PREFIX + "$NonceAndIV");
}
}
private static byte[] generateDefaultPersonalizationString(byte[] seed)
{
return Arrays.concatenate(Strings.toByteArray("Default"), seed,
Pack.longToBigEndian(Thread.currentThread().getId()), Pack.longToBigEndian(System.currentTimeMillis()));
}
private static byte[] generateNonceIVPersonalizationString(byte[] seed)
{
return Arrays.concatenate(Strings.toByteArray("Nonce"), seed,
Pack.longToLittleEndian(Thread.currentThread().getId()), Pack.longToLittleEndian(System.currentTimeMillis()));
}
private static class HybridRandomProvider
extends Provider
{
protected HybridRandomProvider()
{
super("BCHEP", 1.0, "Bouncy Castle Hybrid Entropy Provider");
}
}
private static class URLSeededSecureRandom
extends SecureRandom
{
private final InputStream seedStream;
URLSeededSecureRandom(final URL url)
{
super(null, new HybridRandomProvider());
this.seedStream = AccessController.doPrivileged(new PrivilegedAction()
{
public InputStream run()
{
try
{
return url.openStream();
}
catch (IOException e)
{
throw new IllegalStateException("unable to open random source");
}
}
});
}
public void setSeed(byte[] seed)
{
// ignore
}
public void setSeed(long seed)
{
// ignore
}
public byte[] generateSeed(int numBytes)
{
synchronized (this)
{
byte[] data = new byte[numBytes];
int off = 0;
int len;
while (off != data.length && (len = privilegedRead(data, off, data.length - off)) > -1)
{
off += len;
}
if (off != data.length)
{
throw new InternalError("unable to fully read random source");
}
return data;
}
}
private int privilegedRead(final byte[] data, final int off, final int len)
{
return AccessController.doPrivileged(new PrivilegedAction()
{
public Integer run()
{
try
{
return seedStream.read(data, off, len);
}
catch (IOException e)
{
throw new InternalError("unable to read random source");
}
}
});
}
}
private static class HybridSecureRandom
extends SecureRandom
{
private final AtomicBoolean seedAvailable = new AtomicBoolean(false);
private final AtomicInteger samples = new AtomicInteger(0);
private final SecureRandom baseRandom = createInitialEntropySource();
private final SP800SecureRandom drbg;
HybridSecureRandom()
{
super(null, new HybridRandomProvider());
drbg = new SP800SecureRandomBuilder(new EntropySourceProvider()
{
public EntropySource get(final int bitsRequired)
{
return new SignallingEntropySource(bitsRequired);
}
})
.setPersonalizationString(Strings.toByteArray("Bouncy Castle Hybrid Entropy Source"))
.buildHMAC(new HMac(new SHA512Digest()), baseRandom.generateSeed(32), false); // 32 byte nonce
}
public void setSeed(byte[] seed)
{
if (drbg != null)
{
drbg.setSeed(seed);
}
}
public void setSeed(long seed)
{
if (drbg != null)
{
drbg.setSeed(seed);
}
}
public byte[] generateSeed(int numBytes)
{
byte[] data = new byte[numBytes];
// after 20 samples we'll start to check if there is new seed material.
if (samples.getAndIncrement() > 20)
{
if (seedAvailable.getAndSet(false))
{
samples.set(0);
drbg.reseed((byte[])null); // need for Java 1.9
}
}
drbg.nextBytes(data);
return data;
}
private class SignallingEntropySource
implements EntropySource
{
private final int byteLength;
private final AtomicReference entropy = new AtomicReference();
private final AtomicBoolean scheduled = new AtomicBoolean(false);
SignallingEntropySource(int bitsRequired)
{
this.byteLength = (bitsRequired + 7) / 8;
}
public boolean isPredictionResistant()
{
return true;
}
public byte[] getEntropy()
{
byte[] seed = (byte[])entropy.getAndSet(null);
if (seed == null || seed.length != byteLength)
{
seed = baseRandom.generateSeed(byteLength);
}
else
{
scheduled.set(false);
}
if (!scheduled.getAndSet(true))
{
// don't try to be clever here - things change in Java 11!
Thread gatherer = new Thread(new EntropyGatherer(byteLength));
gatherer.setDaemon(true);
gatherer.start();
}
return seed;
}
public int entropySize()
{
return byteLength * 8;
}
private class EntropyGatherer
implements Runnable
{
private final int numBytes;
EntropyGatherer(int numBytes)
{
this.numBytes = numBytes;
}
private void sleep(long ms)
{
try
{
Thread.sleep(ms);
}
catch (InterruptedException e)
{
Thread.currentThread().interrupt();
}
}
public void run()
{
long ms;
String pause = Properties.getPropertyValue("org.bouncycastle.drbg.gather_pause_secs");
if (pause != null)
{
try
{
ms = Long.parseLong(pause) * 1000;
}
catch (Exception e)
{
ms = 5000;
}
}
else
{
ms = 5000;
}
byte[] seed = new byte[numBytes];
for (int i = 0; i < byteLength / 8; i++)
{
// we need to be mindful that we may not be the only thread/process looking for entropy
sleep(ms);
byte[] rn = baseRandom.generateSeed(8);
System.arraycopy(rn, 0, seed, i * 8, rn.length);
}
int extra = byteLength - ((byteLength / 8) * 8);
if (extra != 0)
{
sleep(ms);
byte[] rn = baseRandom.generateSeed(extra);
System.arraycopy(rn, 0, seed, seed.length - rn.length, rn.length);
}
entropy.set(seed);
seedAvailable.set(true);
}
}
}
}
}
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