IALG.java

/* IALG.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a 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 of the License, 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.

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along with GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, 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
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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
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package gnu.javax.crypto.sasl.srp;

import gnu.javax.crypto.mac.IMac;
import gnu.javax.crypto.mac.MacFactory;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;

import javax.security.sasl.SaslException;

/**
 * A Factory class that returns IALG (Integrity Algorithm) instances that
 * operate as described in the draft-burdis-cat-sasl-srp-04 and later.
 */
public final class IALG
    implements Cloneable
{
  private IMac hmac;

  /** Private constructor to enforce instantiation through Factory method. */
  private IALG(final IMac hmac)
  {
    super();

    this.hmac = hmac;
  }

  /**
   * Returns an instance of a SASL-SRP IALG implementation.
   * 
   * @param algorithm the name of the HMAC algorithm.
   * @return an instance of this object.
   */
  static synchronized IALG getInstance(final String algorithm)
      throws SaslException
  {
    final IMac hmac;
    hmac = MacFactory.getInstance(algorithm);
    if (hmac == null)
      throw new SaslException("getInstance()",
                              new NoSuchAlgorithmException(algorithm));
    return new IALG(hmac);
  }

  public Object clone() throws CloneNotSupportedException
  {
    return new IALG((IMac) hmac.clone());
  }

  public void init(final KDF kdf) throws SaslException
  {
    try
      {
        final byte[] sk = kdf.derive(hmac.macSize());
        final HashMap map = new HashMap();
        map.put(IMac.MAC_KEY_MATERIAL, sk);
        hmac.init(map);
      }
    catch (InvalidKeyException x)
      {
        throw new SaslException("getInstance()", x);
      }
  }

  public void update(final byte[] data)
  {
    hmac.update(data, 0, data.length);
  }

  public void update(final byte[] data, final int offset, final int length)
  {
    hmac.update(data, offset, length);
  }

  public byte[] doFinal()
  {
    return hmac.digest();
  }

  /**
   * Returns the length (in bytes) of this SASL SRP Integrity Algorithm.
   * 
   * @return the length, in bytes, of this integrity protection algorithm.
   */
  public int length()
  {
    return hmac.macSize();
  }
}