Initial revision

From-SVN: r102074

libjava/classpath/java/security/SecureRandom.java

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+/* SecureRandom.java --- Secure Random class implementation
+   Copyright (C) 1999, 2001, 2002, 2003, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package java.security;
+
+import gnu.java.security.Engine;
+
+import java.util.Enumeration;
+import java.util.Random;
+
+/**
+ * An interface to a cryptographically secure pseudo-random number
+ * generator (PRNG). Random (or at least unguessable) numbers are used
+ * in all areas of security and cryptography, from the generation of
+ * keys and initialization vectors to the generation of random padding
+ * bytes.
+ *
+ * @author Mark Benvenuto (ivymccough@worldnet.att.net)
+ * @author Casey Marshall
+ */
+public class SecureRandom extends Random
+{
+
+  // Constants and fields.
+  // ------------------------------------------------------------------------
+
+  /** Service name for PRNGs. */
+  private static final String SECURE_RANDOM = "SecureRandom";
+
+  private static final long serialVersionUID = 4940670005562187L;
+
+  //Serialized Field
+  long counter = 0;		//Serialized
+  Provider provider = null;
+  byte[] randomBytes = null;	//Always null
+  int randomBytesUsed = 0;
+  SecureRandomSpi secureRandomSpi = null;
+  byte[] state = null;
+
+  // Constructors.
+  // ------------------------------------------------------------------------
+
+  /**
+     Default constructor for SecureRandom. It constructs a 
+     new SecureRandom by instantating the first SecureRandom 
+     algorithm in the default security provier. 
+
+     It is not seeded and should be seeded using setSeed or else
+     on the first call to getnextBytes it will force a seed.
+
+     It is maintained for backwards compatibility and programs
+     should use {@link #getInstance(java.lang.String)}.
+   */
+  public SecureRandom()
+  {
+    Provider[] p = Security.getProviders();
+
+    //Format of Key: SecureRandom.algname
+    String key;
+
+    String classname = null;
+    int i;
+    Enumeration e;
+    for (i = 0; i < p.length; i++)
+      {
+        e = p[i].propertyNames();
+        while (e.hasMoreElements())
+          {
+            key = (String) e.nextElement();
+            if (key.startsWith("SECURERANDOM."))
+              {
+                if ((classname = p[i].getProperty(key)) != null)
+                  {
+                    try
+                      {
+                        secureRandomSpi = (SecureRandomSpi) Class.
+                          forName(classname).newInstance();
+                        provider = p[i];
+                        return;
+                      }
+                    catch (ThreadDeath death)
+                      {
+                        throw death;
+                      }
+                    catch (Throwable t)
+		      {
+			// Ignore.
+		      }
+                  }
+              }
+          }
+      }
+
+    // Nothing found. Fall back to SHA1PRNG
+    secureRandomSpi = new gnu.java.security.provider.SHA1PRNG();
+  }
+
+  /**
+     A constructor for SecureRandom. It constructs a new 
+     SecureRandom by instantating the first SecureRandom algorithm 
+     in the default security provier. 
+
+     It is seeded with the passed function and is useful if the user
+     has access to hardware random device (like a radiation detector).
+
+     It is maintained for backwards compatibility and programs
+     should use getInstance.
+
+     @param seed Seed bytes for class
+   */
+  public SecureRandom(byte[] seed)
+  {
+    this();
+    setSeed(seed);
+  }
+
+  /**
+     A constructor for SecureRandom. It constructs a new 
+     SecureRandom using the specified SecureRandomSpi from
+     the specified security provier. 
+
+     @param secureRandomSpi A SecureRandomSpi class
+     @param provider A Provider class
+   */
+  protected SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider)
+  {
+    this.secureRandomSpi = secureRandomSpi;
+    this.provider = provider;
+  }
+
+  // Class methods.
+  // ------------------------------------------------------------------------
+
+  /**
+   * Returns an instance of a SecureRandom. It creates the class from
+   * the first provider that implements it.
+   *
+   * @param algorithm The algorithm name.
+   * @return A new SecureRandom implementing the given algorithm.
+   * @throws NoSuchAlgorithmException If no installed provider implements
+   *         the given algorithm.
+   */
+  public static SecureRandom getInstance(String algorithm)
+    throws NoSuchAlgorithmException
+  {
+    Provider[] p = Security.getProviders();
+    
+    for (int i = 0; i < p.length; i++)
+      {
+        try
+          {
+            return getInstance(algorithm, p[i]);
+          }
+        catch (NoSuchAlgorithmException e)
+          {
+	    // Ignore.
+          }
+      }
+
+    // None found.
+    throw new NoSuchAlgorithmException(algorithm);
+  }
+
+  /**
+   * Returns an instance of a SecureRandom. It creates the class
+   * for the specified algorithm from the named provider.
+   *
+   * @param algorithm The algorithm name.
+   * @param provider  The provider name.
+   * @return A new SecureRandom implementing the chosen algorithm.
+   * @throws NoSuchAlgorithmException If the named provider does not implement
+   *         the algorithm, or if the implementation cannot be
+   *         instantiated.
+   * @throws NoSuchProviderException If no provider named
+   *         <code>provider</code> is currently installed.
+   * @throws IllegalArgumentException If <code>provider</code> is null
+   *         or is empty.
+   */
+  public static SecureRandom getInstance(String algorithm, String provider)
+  throws NoSuchAlgorithmException, NoSuchProviderException
+  {
+    if (provider == null || provider.length() == 0)
+      throw new IllegalArgumentException("Illegal provider");
+
+    Provider p = Security.getProvider(provider);
+    if (p == null)
+      throw new NoSuchProviderException(provider);
+    
+    return getInstance(algorithm, p);
+  }
+
+  /**
+   * Returns an instance of a SecureRandom. It creates the class for
+   * the specified algorithm from the given provider.
+   *
+   * @param algorithm The SecureRandom algorithm to create.
+   * @param provider  The provider to get the instance from.
+   * @throws NoSuchAlgorithmException If the algorithm cannot be found, or
+   *         if the class cannot be instantiated.
+   * @throws IllegalArgumentException If <code>provider</code> is null.
+   */
+  public static SecureRandom getInstance(String algorithm, Provider provider)
+  throws NoSuchAlgorithmException
+  {
+    if (provider == null)
+      throw new IllegalArgumentException("Illegal provider");
+    try
+      {
+        return new SecureRandom((SecureRandomSpi)
+          Engine.getInstance(SECURE_RANDOM, algorithm, provider),
+          provider);
+      }
+    catch (java.lang.reflect.InvocationTargetException ite)
+      {
+	throw new NoSuchAlgorithmException(algorithm);
+      }
+    catch (ClassCastException cce)
+      {
+        throw new NoSuchAlgorithmException(algorithm);
+      }
+  }
+
+  // Instance methods.
+  // ------------------------------------------------------------------------
+
+  /**
+     Returns the provider being used by the current SecureRandom class.
+
+     @return The provider from which this SecureRandom was attained
+   */
+  public final Provider getProvider()
+  {
+    return provider;
+  }
+
+  /**
+     Seeds the SecureRandom. The class is re-seeded for each call and 
+     each seed builds on the previous seed so as not to weaken security.
+
+     @param seed seed bytes to seed with
+   */
+  public void setSeed(byte[] seed)
+  {
+    secureRandomSpi.engineSetSeed(seed);
+  }
+
+  /**
+     Seeds the SecureRandom. The class is re-seeded for each call and 
+     each seed builds on the previous seed so as not to weaken security.
+
+     @param seed 8 seed bytes to seed with
+   */
+  public void setSeed(long seed)
+  {
+    // This particular setSeed will be called by Random.Random(), via
+    // our own constructor, before secureRandomSpi is initialized.  In
+    // this case we can't call a method on secureRandomSpi, and we
+    // definitely don't want to throw a NullPointerException.
+    // Therefore we test.
+    if (secureRandomSpi != null)
+      {
+        byte[] tmp = { (byte) (0xff & (seed >> 56)),
+		       (byte) (0xff & (seed >> 48)),
+		       (byte) (0xff & (seed >> 40)),
+		       (byte) (0xff & (seed >> 32)),
+		       (byte) (0xff & (seed >> 24)),
+		       (byte) (0xff & (seed >> 16)),
+		       (byte) (0xff & (seed >> 8)),
+		       (byte) (0xff & seed)
+        };
+        secureRandomSpi.engineSetSeed(tmp);
+      }
+  }
+
+  /**
+     Generates a user specified number of bytes. This function
+     is the basis for all the random functions.
+
+     @param bytes array to store generated bytes in
+   */
+  public void nextBytes(byte[] bytes)
+  {
+    randomBytesUsed += bytes.length;
+    counter++;
+    secureRandomSpi.engineNextBytes(bytes);
+  }
+
+  /**
+     Generates an integer containing the user specified
+     number of random bits. It is right justified and padded
+     with zeros.
+
+     @param numBits number of random bits to get, 0 <= numBits <= 32;
+
+     @return the random bits
+   */
+  protected final int next(int numBits)
+  {
+    if (numBits == 0)
+      return 0;
+
+    byte[] tmp = new byte[numBits / 8 + (1 * (numBits % 8))];
+
+    secureRandomSpi.engineNextBytes(tmp);
+    randomBytesUsed += tmp.length;
+    counter++;
+
+    int ret = 0;
+
+    for (int i = 0; i < tmp.length; i++)
+      ret |= (tmp[i] & 0xFF) << (8 * i);
+
+    long mask = (1L << numBits) - 1;
+    return (int) (ret & mask);
+  }
+
+  /**
+     Returns the given number of seed bytes. This method is
+     maintained only for backwards capability. 
+
+     @param numBytes number of seed bytes to get
+
+     @return an array containing the seed bytes
+   */
+  public static byte[] getSeed(int numBytes)
+  {
+    byte[] tmp = new byte[numBytes];
+
+    new Random().nextBytes(tmp);
+    return tmp;
+    //return secureRandomSpi.engineGenerateSeed( numBytes );
+  }
+
+  /**
+     Returns the specified number of seed bytes.
+
+     @param numBytes number of seed bytes to get
+
+     @return an array containing the seed bytes
+   */
+  public byte[] generateSeed(int numBytes)
+  {
+    return secureRandomSpi.engineGenerateSeed(numBytes);
+  }
+
+}