package gnu.crypto.sig;

// ----------------------------------------------------------------------------
// $Id: BaseSignature.java,v 1.8 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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 Crypto 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 this program; 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.
// ----------------------------------------------------------------------------

import gnu.crypto.hash.IMessageDigest;
import gnu.crypto.prng.IRandom;
import gnu.crypto.prng.LimitReachedException;
import gnu.crypto.util.PRNG;

import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.Map;
import java.util.Random;

/**
 * <p>A base abstract class to facilitate implementations of concrete
 * Signatures.</p>
 *
 * @version $Revision: 1.8 $
 */
public abstract class BaseSignature implements ISignature {

   // Constants and variables
   // -------------------------------------------------------------------------

   /** The canonical name of this signature scheme. */
   protected String schemeName;

   /** The underlying message digest instance for this signature scheme. */
   protected IMessageDigest md;

   /** The public key to use when verifying signatures. */
   protected PublicKey publicKey;

   /** The private key to use when generating signatures (signing). */
   protected PrivateKey privateKey;

   /** The optional {@link Random} instance to use. */
   private Random rnd;

   /** The optional {@link IRandom} instance to use. */
   private IRandom irnd;

   // Constructor(s)
   // -------------------------------------------------------------------------

   /**
    * <p>Trivial constructor.</p>
    *
    * @param schemeName the name of this signature scheme.
    * @param md the underlying instance of the message digest algorithm.
    */
   protected BaseSignature(String schemeName, IMessageDigest md) {
      super();

      this.schemeName = schemeName;
      this.md = md;
   }

   // Class methods
   // -------------------------------------------------------------------------

   // Instance methods
   // -------------------------------------------------------------------------

   // gnu.crypto.sig.ISignature interface implementation ----------------------

   public String name() {
      return schemeName;
   }

   public void setupVerify(Map attributes) throws IllegalArgumentException {
      setup(attributes);

      // do we have a public key?
      PublicKey key = (PublicKey) attributes.get(VERIFIER_KEY);
      if (key != null) {
         setupForVerification(key);
      }
   }

   public void setupSign(Map attributes) throws IllegalArgumentException {
      setup(attributes);

      // do we have a private key?
      PrivateKey key = (PrivateKey) attributes.get(SIGNER_KEY);
      if (key != null) {
         setupForSigning(key);
      }
   }

   public void update(byte b) {
      if (md == null) {
         throw new IllegalStateException();
      }
      md.update(b);
   }

   public void update(byte[] b, int off, int len) {
      if (md == null) {
         throw new IllegalStateException();
      }
      md.update(b, off, len);
   }

   public Object sign() {
      if (md == null || privateKey == null) {
         throw new IllegalStateException();
      }

      return generateSignature();
   }

   public boolean verify(Object sig) {
      if (md == null || publicKey == null) {
         throw new IllegalStateException();
      }

      return verifySignature(sig);
   }

   // abstract methods to be implemented by concrete subclasses ---------------

   public abstract Object clone();

   protected abstract void setupForVerification(PublicKey key)
   throws IllegalArgumentException;

   protected abstract void setupForSigning(PrivateKey key)
   throws IllegalArgumentException;

   protected abstract Object generateSignature()
   throws IllegalStateException;

   protected abstract boolean verifySignature(Object signature)
   throws IllegalStateException;

   // Other instance methods --------------------------------------------------

   /** Initialises the internal fields of this instance. */
   protected void init() {
      md.reset();
      rnd = null;
      irnd = null;
      publicKey = null;
      privateKey = null;
   }

   /**
    * <p>Fills the designated byte array with random data.</p>
    *
    * @param buffer the byte array to fill with random data.
    */
   protected void nextRandomBytes(byte[] buffer) {
      if (rnd != null) {
         rnd.nextBytes(buffer);
      } else if (irnd != null) {
         try {
            irnd.nextBytes(buffer, 0, buffer.length);
         } catch (IllegalStateException x) {
            throw new RuntimeException("nextRandomBytes(): "+String.valueOf(x));
         } catch (LimitReachedException x) {
            throw new RuntimeException("nextRandomBytes(): "+String.valueOf(x));
         }
      } else {
         PRNG.nextBytes(buffer);
      }
   }

   private void setup(Map attributes) {
      init();

      // do we have a Random or SecureRandom, or should we use our own?
      Object obj = attributes.get(SOURCE_OF_RANDOMNESS);
      if (obj instanceof Random) {
         rnd = (Random) obj;
      } else if (obj instanceof IRandom) {
         irnd = (IRandom) obj;
      }
   }
}
