/* Certificate.java --- Certificate class
   Copyright (C) 1999, 2003, 2004 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.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 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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terms of your choice, provided that you also meet, for each linked
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.security.cert;

import java.io.ByteArrayInputStream;
import java.io.InvalidObjectException;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PublicKey;
import java.security.SignatureException;

/**
 * The Certificate class is an abstract class used to manage 
 * identity certificates. An identity certificate is a
 * combination of a principal and a public key which is 
 * certified by another principal. This is the puprose of 
 * Certificate Authorities (CA).
 * 
 * <p>This class is used to manage different types of certificates
 * but have important common puposes. Different types of 
 * certificates like X.509 and OpenPGP share general certificate
 * functions (like encoding and verifying) and information like
 * public keys.
 * 
 * <p>X.509, OpenPGP, and SDSI can be implemented by subclassing this
 * class even though they differ in storage methods and information
 * stored.
 *
 * @see CertificateFactory
 * @see X509Certificate
 * @since JDK 1.2
 * @author Mark Benvenuto
 * @author Casey Marshall
 */
public abstract class Certificate implements Serializable
{
  private static final long serialVersionUID = -6751606818319535583L;
	
  private String type;

  /**
     Constructs a new certificate of the specified type. An example
     is "X.509".

     @param type a valid standard name for a certificate.
  */
  protected Certificate(String type)
  {
    this.type = type;
  }

  /**
     Returns the Certificate type.

     @return a string representing the Certificate type
  */
  public final String getType()
  {
    return type;
  }

  /**
     Compares this Certificate to other. It checks if the
     object if instanceOf Certificate and then checks if
     the encoded form matches.

     @param other An Object to test for equality

     @return true if equal, false otherwise
  */
  public boolean equals(Object other)
  {
    if( other instanceof Certificate ) {
      try {
	Certificate x = (Certificate) other;
	if( getEncoded().length != x.getEncoded().length )
	  return false;

	byte[] b1 = getEncoded();
	byte[] b2 = x.getEncoded();

	for( int i = 0; i < b1.length; i++ )
	  if( b1[i] != b2[i] )
	    return false;

      } catch( CertificateEncodingException cee ) { 
	return false;
      }
      return true;
    }
    return false;
  }

  /**
     Returns a hash code for this Certificate in its encoded
     form.

     @return A hash code of this class
  */
  public int hashCode()
  {
    return super.hashCode();
  }

  /**
     Gets the DER ASN.1 encoded format for this Certificate.
     It assumes each certificate has only one encoding format.
     Ex: X.509 is encoded as ASN.1 DER

     @return byte array containg encoded form

     @throws CertificateEncodingException if an error occurs
  */
  public abstract byte[] getEncoded() throws CertificateEncodingException;

  /**
     Verifies that this Certificate was properly signed with the
     PublicKey that corresponds to its private key. 

     @param key PublicKey to verify with

     @throws CertificateException encoding error
     @throws NoSuchAlgorithmException unsupported algorithm
     @throws InvalidKeyException incorrect key
     @throws NoSuchProviderException no provider
     @throws SignatureException signature error
  */
  public abstract void verify(PublicKey key)
    throws CertificateException,
    NoSuchAlgorithmException,
    InvalidKeyException,
    NoSuchProviderException,
    SignatureException;

  /**
     Verifies that this Certificate was properly signed with the
     PublicKey that corresponds to its private key and uses
     the signature engine provided by the provider. 

     @param key PublicKey to verify with
     @param sigProvider Provider to use for signature algorithm

     @throws CertificateException encoding error
     @throws NoSuchAlgorithmException unsupported algorithm
     @throws InvalidKeyException incorrect key
     @throws NoSuchProviderException incorrect provider
     @throws SignatureException signature error
  */
  public abstract void verify(PublicKey key,
			      String sigProvider)
    throws CertificateException,
    NoSuchAlgorithmException,
    InvalidKeyException,
    NoSuchProviderException,
    SignatureException;

  /**
     Returns a string representing the Certificate.

     @return a string representing the Certificate.
  */
  public abstract String toString();


  /**
     Returns the public key stored in the Certificate.

     @return The public key
  */
  public abstract PublicKey getPublicKey();

  // Protected methods.
  // ------------------------------------------------------------------------

  /**
   * Returns a replacement for this certificate to be serialized. This
   * method returns the equivalent to the following for this class:
   *
   * <blockquote>
   * <pre>new CertificateRep(getType(), getEncoded());</pre>
   * </blockquote>
   *
   * <p>This thusly replaces the certificate with its name and its
   * encoded form, which can be deserialized later with the {@link
   * CertificateFactory} implementation for this certificate's type.
   *
   * @return The replacement object to be serialized.
   * @throws ObjectStreamException If the replacement could not be
   * created.
   */
  protected Object writeReplace() throws ObjectStreamException
  {
    try
      {
        return new CertificateRep(getType(), getEncoded());
      }
    catch (CertificateEncodingException cee)
      {
        throw new InvalidObjectException(cee.toString());
      }
  }

  // Inner class.
  // ------------------------------------------------------------------------

  /**
     Certificate.CertificateRep is an inner class used to provide an alternate
     storage mechanism for serialized Certificates.
  */
  protected static class CertificateRep implements java.io.Serializable
  {

    /** From JDK1.4. */
    private static final long serialVersionUID = -8563758940495660020L;
  
    /** The certificate type, e.g. "X.509". */
    private String type;

    /** The encoded certificate data. */
    private byte[] data;

    /**
     * Create an alternative representation of this certificate. The
     * <code>(type, data)</code> pair is typically the certificate's
     * type as returned by {@link Certificate#getType()} (i.e. the
     * canonical name of the certificate type) and the encoded form as
     * returned by {@link Certificate#getEncoded()}.
     *
     * <p>For example, X.509 certificates would create an instance of
     * this class with the parameters "X.509" and the ASN.1
     * representation of the certificate, encoded as DER bytes.
     *
     * @param type The certificate type.
     * @param data The encoded certificate data.
     */
    protected CertificateRep(String type, byte[] data)
    {
      this.type = type;
      this.data = data;
    }

    /**
     * Deserialize this certificate replacement into the appropriate
     * certificate object. That is, this method attempts to create a
     * {@link CertificateFactory} for this certificate's type, then
     * attempts to parse the encoded data with that factory, returning
     * the resulting certificate.
     *
     * @return The deserialized certificate.
     * @throws ObjectStreamException If there is no appropriate
     * certificate factory for the given type, or if the encoded form
     * cannot be parsed.
     */
    protected Object readResolve() throws ObjectStreamException
    {
      try
        {
          CertificateFactory fact = CertificateFactory.getInstance(type);
          return fact.generateCertificate(new ByteArrayInputStream(data));
        }
      catch (Exception e)
        {
          throw new InvalidObjectException(e.toString());
        }
    }
  }
}