mirror of git://gcc.gnu.org/git/gcc.git
128 lines
4.2 KiB
Java
128 lines
4.2 KiB
Java
/* MDGenerator.java --
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Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.
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This file is a part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at
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your option) any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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USA
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.java.security.prng;
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import gnu.java.security.Registry;
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import gnu.java.security.hash.HashFactory;
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import gnu.java.security.hash.IMessageDigest;
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import java.util.Map;
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/**
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* A simple pseudo-random number generator that relies on a hash algorithm, that
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* (a) starts its operation by hashing a <code>seed</code>, and then (b)
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* continuously re-hashing its output. If no hash algorithm name is specified in
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* the {@link Map} of attributes used to initialise the instance then the
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* SHA-160 algorithm is used as the underlying hash function. Also, if no
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* <code>seed</code> is given, an empty octet sequence is used.
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*/
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public class MDGenerator
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extends BasePRNG
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implements Cloneable
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{
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/** Property name of underlying hash algorithm for this generator. */
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public static final String MD_NAME = "gnu.crypto.prng.md.hash.name";
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/** Property name of seed material. */
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public static final String SEEED = "gnu.crypto.prng.md.seed";
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/** The underlying hash instance. */
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private IMessageDigest md;
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/** Trivial 0-arguments constructor. */
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public MDGenerator()
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{
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super(Registry.MD_PRNG);
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}
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public void setup(Map attributes)
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{
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// find out which hash to use
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String underlyingMD = (String) attributes.get(MD_NAME);
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if (underlyingMD == null)
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{
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if (md == null)
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{ // happy birthday
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// ensure we have a reliable implementation of this hash
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md = HashFactory.getInstance(Registry.SHA160_HASH);
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}
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else // a clone. reset it for reuse
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md.reset();
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}
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else // ensure we have a reliable implementation of this hash
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md = HashFactory.getInstance(underlyingMD);
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// get the seeed
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byte[] seed = (byte[]) attributes.get(SEEED);
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if (seed == null)
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seed = new byte[0];
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md.update(seed, 0, seed.length);
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}
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public void fillBlock() throws LimitReachedException
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{
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IMessageDigest mdc = (IMessageDigest) md.clone();
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buffer = mdc.digest();
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md.update(buffer, 0, buffer.length);
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}
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public void addRandomByte(final byte b)
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{
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if (md == null)
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throw new IllegalStateException("not initialized");
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md.update(b);
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}
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public void addRandomBytes(final byte[] buf, final int off, final int len)
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{
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if (md == null)
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throw new IllegalStateException("not initialized");
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md.update(buf, off, len);
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}
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public Object clone() throws CloneNotSupportedException
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{
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MDGenerator result = (MDGenerator) super.clone();
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if (this.md != null)
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result.md = (IMessageDigest) this.md.clone();
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return result;
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}
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}
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