/*
* @(#)SecureRandom.java 1.54 06/04/21
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.security;
import java.util.*;
import java.security.Provider.Service;
import sun.security.jca.*;
import sun.security.jca.GetInstance.Instance;
/**
* This class provides a cryptographically strong random number
* generator (RNG).
*
* <p>A cryptographically strong random number
* minimally complies with the statistical random number generator tests
* specified in <a href="http://csrc.nist.gov/cryptval/140-2.htm">
* <i>FIPS 140-2, Security Requirements for Cryptographic Modules</i></a>,
* section 4.9.1.
* Additionally, SecureRandom must produce non-deterministic output.
* Therefore any seed material passed to a SecureRandom object must be
* unpredictable, and all SecureRandom output sequences must be
* cryptographically strong, as described in
* <a href="http://www.ietf.org/rfc/rfc1750.txt">
* <i>RFC 1750: Randomness Recommendations for Security</i></a>.
*
* <p>A caller obtains a SecureRandom instance via the
* no-argument constructor or one of the <code>getInstance</code> methods:
*
* <pre>
* SecureRandom random = new SecureRandom();
* </pre>
*
* <p> Many SecureRandom implementations are in the form of a pseudo-random
* number generator (PRNG), which means they use a deterministic algorithm
* to produce a pseudo-random sequence from a true random seed.
* Other implementations may produce true random numbers,
* and yet others may use a combination of both techniques.
*
* <p> Typical callers of SecureRandom invoke the following methods
* to retrieve random bytes:
*
* <pre>
* SecureRandom random = new SecureRandom();
* byte bytes[] = new byte[20];
* random.nextBytes(bytes);
* </pre>
*
* <p> Callers may also invoke the <code>generateSeed</code> method
* to generate a given number of seed bytes (to seed other random number
* generators, for example):
* <pre>
* byte seed[] = random.generateSeed(20);
* </pre>
*
* @see java.security.SecureRandomSpi
* @see java.util.Random
*
* @version 1.54, 04/21/06
* @author Benjamin Renaud
* @author Josh Bloch
*/
public class SecureRandom extends java.util.Random {
/**
* The provider.
*
* @serial
* @since 1.2
*/
private Provider provider = null;
/**
* The provider implementation.
*
* @serial
* @since 1.2
*/
private SecureRandomSpi secureRandomSpi = null;
/*
* The algorithm name of null if unknown.
*
* @serial
* @since 1.5
*/
private String algorithm;
// Seed Generator
private static volatile SecureRandom seedGenerator = null;
/**
* Constructs a secure random number generator (RNG) implementing the
* default random number algorithm.
*
* <p> This constructor traverses the list of registered security Providers,
* starting with the most preferred Provider.
* A new SecureRandom object encapsulating the
* SecureRandomSpi implementation from the first
* Provider that supports a SecureRandom (RNG) algorithm is returned.
* If none of the Providers support a RNG algorithm,
* then an implementation-specific default is returned.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* <p> See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard RNG algorithm names.
*
* <p> The returned SecureRandom object has not been seeded. To seed the
* returned object, call the <code>setSeed</code> method.
* If <code>setSeed</code> is not called, the first call to
* <code>nextBytes</code> will force the SecureRandom object to seed itself.
* This self-seeding will not occur if <code>setSeed</code> was
* previously called.
*/
public SecureRandom() {
/*
* This call to our superclass constructor will result in a call
* to our own <code>setSeed</code> method, which will return
* immediately when it is passed zero.
*/
super(0);
getDefaultPRNG(false, null);
}
/**
* Constructs a secure random number generator (RNG) implementing the
* default random number algorithm.
* The SecureRandom instance is seeded with the specified seed bytes.
*
* <p> This constructor traverses the list of registered security Providers,
* starting with the most preferred Provider.
* A new SecureRandom object encapsulating the
* SecureRandomSpi implementation from the first
* Provider that supports a SecureRandom (RNG) algorithm is returned.
* If none of the Providers support a RNG algorithm,
* then an implementation-specific default is returned.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* <p> See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard RNG algorithm names.
*
* @param seed the seed.
*/
public SecureRandom(byte seed[]) {
super(0);
getDefaultPRNG(true, seed);
}
private void getDefaultPRNG(boolean setSeed, byte[] seed) {
String prng = getPrngAlgorithm();
if (prng == null) {
// bummer, get the SUN implementation
prng = "SHA1PRNG";
this.secureRandomSpi = new sun.security.provider.SecureRandom();
this.provider = new sun.security.provider.Sun();
if (setSeed) {
this.secureRandomSpi.engineSetSeed(seed);
}
} else {
try {
SecureRandom random = SecureRandom.getInstance(prng);
this.secureRandomSpi = random.getSecureRandomSpi();
this.provider = random.getProvider();
if (setSeed) {
this.secureRandomSpi.engineSetSeed(seed);
}
} catch (NoSuchAlgorithmException nsae) {
// never happens, because we made sure the algorithm exists
throw new RuntimeException(nsae);
}
}
// JDK 1.1 based implementations subclass SecureRandom instead of
// SecureRandomSpi. They will also go through this code path because
// they must call a SecureRandom constructor as it is their superclass.
// If we are dealing with such an implementation, do not set the
// algorithm value as it would be inaccurate.
if (getClass() == SecureRandom.class) {
this.algorithm = prng;
}
}
/**
* Creates a SecureRandom object.
*
* @param secureRandomSpi the SecureRandom implementation.
* @param provider the provider.
*/
protected SecureRandom(SecureRandomSpi secureRandomSpi,
Provider provider) {
this(secureRandomSpi, provider, null);
}
private SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider,
String algorithm) {
super(0);
this.secureRandomSpi = secureRandomSpi;
this.provider = provider;
this.algorithm = algorithm;
}
/**
* Returns a SecureRandom object that implements the specified
* Random Number Generator (RNG) algorithm.
*
* <p> This method traverses the list of registered security Providers,
* starting with the most preferred Provider.
* A new SecureRandom object encapsulating the
* SecureRandomSpi implementation from the first
* Provider that supports the specified algorithm is returned.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* <p> The returned SecureRandom object has not been seeded. To seed the
* returned object, call the <code>setSeed</code> method.
* If <code>setSeed</code> is not called, the first call to
* <code>nextBytes</code> will force the SecureRandom object to seed itself.
* This self-seeding will not occur if <code>setSeed</code> was
* previously called.
*
* @param algorithm the name of the RNG algorithm.
* See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard RNG algorithm names.
*
* @return the new SecureRandom object.
*
* @exception NoSuchAlgorithmException if no Provider supports a
* SecureRandomSpi implementation for the
* specified algorithm.
*
* @see Provider
*
* @since 1.2
*/
public static SecureRandom getInstance(String algorithm)
throws NoSuchAlgorithmException {
Instance instance = GetInstance.getInstance("SecureRandom",
SecureRandomSpi.class, algorithm);
return new SecureRandom((SecureRandomSpi)instance.impl,
instance.provider, algorithm);
}
/**
* Returns a SecureRandom object that implements the specified
* Random Number Generator (RNG) algorithm.
*
* <p> A new SecureRandom object encapsulating the
* SecureRandomSpi implementation from the specified provider
* is returned. The specified provider must be registered
* in the security provider list.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* <p> The returned SecureRandom object has not been seeded. To seed the
* returned object, call the <code>setSeed</code> method.
* If <code>setSeed</code> is not called, the first call to
* <code>nextBytes</code> will force the SecureRandom object to seed itself.
* This self-seeding will not occur if <code>setSeed</code> was
* previously called.
*
* @param algorithm the name of the RNG algorithm.
* See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard RNG algorithm names.
*
* @param provider the name of the provider.
*
* @return the new SecureRandom object.
*
* @exception NoSuchAlgorithmException if a SecureRandomSpi
* implementation for the specified algorithm is not
* available from the specified provider.
*
* @exception NoSuchProviderException if the specified provider is not
* registered in the security provider list.
*
* @exception IllegalArgumentException if the provider name is null
* or empty.
*
* @see Provider
*
* @since 1.2
*/
public static SecureRandom getInstance(String algorithm, String provider)
throws NoSuchAlgorithmException, NoSuchProviderException {
Instance instance = GetInstance.getInstance("SecureRandom",
SecureRandomSpi.class, algorithm, provider);
return new SecureRandom((SecureRandomSpi)instance.impl,
instance.provider, algorithm);
}
/**
* Returns a SecureRandom object that implements the specified
* Random Number Generator (RNG) algorithm.
*
* <p> A new SecureRandom object encapsulating the
* SecureRandomSpi implementation from the specified Provider
* object is returned. Note that the specified Provider object
* does not have to be registered in the provider list.
*
* <p> The returned SecureRandom object has not been seeded. To seed the
* returned object, call the <code>setSeed</code> method.
* If <code>setSeed</code> is not called, the first call to
* <code>nextBytes</code> will force the SecureRandom object to seed itself.
* This self-seeding will not occur if <code>setSeed</code> was
* previously called.
*
* @param algorithm the name of the RNG algorithm.
* See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard RNG algorithm names.
*
* @param provider the provider.
*
* @return the new SecureRandom object.
*
* @exception NoSuchAlgorithmException if a SecureRandomSpi
* implementation for the specified algorithm is not available
* from the specified Provider object.
*
* @exception IllegalArgumentException if the specified provider is null.
*
* @see Provider
*
* @since 1.4
*/
public static SecureRandom getInstance(String algorithm,
Provider provider) throws NoSuchAlgorithmException {
Instance instance = GetInstance.getInstance("SecureRandom",
SecureRandomSpi.class, algorithm, provider);
return new SecureRandom((SecureRandomSpi)instance.impl,
instance.provider, algorithm);
}
/**
* Returns the SecureRandomSpi of this SecureRandom object.
*/
SecureRandomSpi getSecureRandomSpi() {
return secureRandomSpi;
}
/**
* Returns the provider of this SecureRandom object.
*
* @return the provider of this SecureRandom object.
*/
public final Provider getProvider() {
return provider;
}
/**
* Returns the name of the algorithm implemented by this SecureRandom
* object.
*
* @return the name of the algorithm or <code>unknown</code>
* if the algorithm name cannot be determined.
* @since 1.5
*/
public String getAlgorithm() {
return (algorithm != null) ? algorithm : "unknown";
}
/**
* Reseeds this random object. The given seed supplements, rather than
* replaces, the existing seed. Thus, repeated calls are guaranteed
* never to reduce randomness.
*
* @param seed the seed.
*
* @see #getSeed
*/
synchronized public void setSeed(byte[] seed) {
secureRandomSpi.engineSetSeed(seed);
}
/**
* Reseeds this random object, using the eight bytes contained
* in the given <code>long seed</code>. The given seed supplements,
* rather than replaces, the existing seed. Thus, repeated calls
* are guaranteed never to reduce randomness.
*
* <p>This method is defined for compatibility with
* <code>java.util.Random</code>.
*
* @param seed the seed.
*
* @see #getSeed
*/
public void setSeed(long seed) {
/*
* Ignore call from super constructor (as well as any other calls
* unfortunate enough to be passing 0). It's critical that we
* ignore call from superclass constructor, as digest has not
* yet been initialized at that point.
*/
if (seed != 0) {
secureRandomSpi.engineSetSeed(longToByteArray(seed));
}
}
/**
* Generates a user-specified number of random bytes.
*
* <p> If a call to <code>setSeed</code> had not occurred previously,
* the first call to this method forces this SecureRandom object
* to seed itself. This self-seeding will not occur if
* <code>setSeed</code> was previously called.
*
* @param bytes the array to be filled in with random bytes.
*/
synchronized public void nextBytes(byte[] bytes) {
secureRandomSpi.engineNextBytes(bytes);
}
/**
* Generates an integer containing the user-specified number of
* pseudo-random bits (right justified, with leading zeros). This
* method overrides a <code>java.util.Random</code> method, and serves
* to provide a source of random bits to all of the methods inherited
* from that class (for example, <code>nextInt</code>,
* <code>nextLong</code>, and <code>nextFloat</code>).
*
* @param numBits number of pseudo-random bits to be generated, where
* 0 <= <code>numBits</code> <= 32.
*
* @return an <code>int</code> containing the user-specified number
* of pseudo-random bits (right justified, with leading zeros).
*/
final protected int next(int numBits) {
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);
}
/**
* Returns the given number of seed bytes, computed using the seed
* generation algorithm that this class uses to seed itself. This
* call may be used to seed other random number generators.
*
* <p>This method is only included for backwards compatibility.
* The caller is encouraged to use one of the alternative
* <code>getInstance</code> methods to obtain a SecureRandom object, and
* then call the <code>generateSeed</code> method to obtain seed bytes
* from that object.
*
* @param numBytes the number of seed bytes to generate.
*
* @return the seed bytes.
*
* @see #setSeed
*/
public static byte[] getSeed(int numBytes) {
if (seedGenerator == null)
seedGenerator = new SecureRandom();
return seedGenerator.generateSeed(numBytes);
}
/**
* Returns the given number of seed bytes, computed using the seed
* generation algorithm that this class uses to seed itself. This
* call may be used to seed other random number generators.
*
* @param numBytes the number of seed bytes to generate.
*
* @return the seed bytes.
*/
public byte[] generateSeed(int numBytes) {
return secureRandomSpi.engineGenerateSeed(numBytes);
}
/**
* Helper function to convert a long into a byte array (least significant
* byte first).
*/
private static byte[] longToByteArray(long l) {
byte[] retVal = new byte[8];
for (int i = 0; i < 8; i++) {
retVal[i] = (byte) l;
l >>= 8;
}
return retVal;
}
/**
* Gets a default PRNG algorithm by looking through all registered
* providers. Returns the first PRNG algorithm of the first provider that
* has registered a SecureRandom implementation, or null if none of the
* registered providers supplies a SecureRandom implementation.
*/
private static String getPrngAlgorithm() {
List provs = Providers.getProviderList().providers();
for (Iterator t = provs.iterator(); t.hasNext();) {
Provider p = (Provider)t.next();
for (Iterator u = p.getServices().iterator(); u.hasNext();) {
Service s = (Service)u.next();
if (s.getType().equals("SecureRandom")) {
return s.getAlgorithm();
}
}
}
return null;
}
// Declare serialVersionUID to be compatible with JDK1.1
static final long serialVersionUID = 4940670005562187L;
// Retain unused values serialized from JDK1.1
/**
* @serial
*/
private byte[] state;
/**
* @serial
*/
private MessageDigest digest = null;
/**
* @serial
*
* We know that the MessageDigest class does not implement
* java.io.Serializable. However, since this field is no longer
* used, it will always be NULL and won't affect the serialization
* of the SecureRandom class itself.
*/
private byte[] randomBytes;
/**
* @serial
*/
private int randomBytesUsed;
/**
* @serial
*/
private long counter;
}
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