extension.java

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/*
 * @(#)Extension.java	1.23 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program 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 version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package sun.security.x509;

import java.io.IOException;
import java.util.Arrays;
import sun.security.util.*;

/**
 * Represent a X509 Extension Attribute.
 *
 * <p>Extensions are additional attributes which can be inserted in a X509
 * v3 certificate. For example a "Driving License Certificate" could have
 * the driving license number as a extension.
 *
 * <p>Extensions are represented as a sequence of the extension identifier
 * (Object Identifier), a boolean flag stating whether the extension is to
 * be treated as being critical and the extension value itself (this is again
 * a DER encoding of the extension value).
 * <pre>
 * ASN.1 definition of Extension:
 * Extension ::= SEQUENCE {
 *	ExtensionId	OBJECT IDENTIFIER,
 *	critical	BOOLEAN DEFAULT FALSE,
 *	extensionValue	OCTET STRING
 * }
 * </pre>
 * All subclasses need to implement a constructor of the form
 * <pre>
 *     <subclass> (Boolean, Object)
 * <pre>
 * where the Object is typically an array of DER encoded bytes.
 * <p>
 * @author Amit Kapoor
 * @author Hemma Prafullchandra
 * @version 1.16
 */
public class Extension {
    protected ObjectIdentifier	extensionId = null;
    protected boolean		critical = false;
    protected byte[]		extensionValue = null;

    /**
     * Default constructor.  Used only by sub-classes.
     */
    public Extension() { }

    /**
     * Constructs an extension from a DER encoded array of bytes.
     */
    public Extension(DerValue derVal) throws IOException {

        DerInputStream in = derVal.toDerInputStream();

        // Object identifier
        extensionId = in.getOID();

        // If the criticality flag was false, it will not have been encoded.
        DerValue val = in.getDerValue();
        if (val.tag == DerValue.tag_Boolean) {
            critical = val.getBoolean();

            // Extension value (DER encoded)
            val = in.getDerValue();
            extensionValue = val.getOctetString();
        } else {
            critical = false;
            extensionValue = val.getOctetString();
        }
    }

    /**
     * Constructs an Extension from individual components of ObjectIdentifier,
     * criticality and the DER encoded OctetString.
     *
     * @param extensionId the ObjectIdentifier of the extension
     * @param critical the boolean indicating if the extension is critical
     * @param extensionValue the DER encoded octet string of the value.
     */
    public Extension(ObjectIdentifier extensionId, boolean critical,
                     byte[] extensionValue) throws IOException {
        this.extensionId = extensionId;
        this.critical = critical;
        // passed in a DER encoded octet string, strip off the tag
        // and length
        DerValue inDerVal = new DerValue(extensionValue);
        this.extensionValue = inDerVal.getOctetString();
    }

    /**
     * Constructs an Extension from another extension. To be used for
     * creating decoded subclasses.
     *
     * @param ext the extension to create from.
     */
    public Extension(Extension ext) {
        this.extensionId = ext.extensionId;
        this.critical = ext.critical;
        this.extensionValue = ext.extensionValue;
    }

    /**
     * Write the extension to the DerOutputStream.
     *
     * @param out the DerOutputStream to write the extension to.
     * @exception IOException on encoding errors
     */
    public void encode(DerOutputStream out) throws IOException {

        if (extensionId == null)
            throw new IOException("Null OID to encode for the extension!");
        if (extensionValue == null)
            throw new IOException("No value to encode for the extension!");

        DerOutputStream dos = new DerOutputStream();

        dos.putOID(extensionId);
        if (critical)
            dos.putBoolean(critical);
        dos.putOctetString(extensionValue);

        out.write(DerValue.tag_Sequence, dos);
    }

    /**
     * Returns true if extension is critical.
     */
    public boolean isCritical() {
        return (critical);
    }

    /**
     * Returns the ObjectIdentifier of the extension.
     */
    public ObjectIdentifier getExtensionId() {
        return (extensionId);
    }

    /**
     * Returns the extension value as an byte array for further processing.
     * Note, this is the raw DER value of the extension, not the DER
     * encoded octet string which is in the certificate.
     */
    public byte[] getExtensionValue() {
        if (extensionValue == null)
            return null;

        byte[] dup = new byte[extensionValue.length];
        System.arraycopy(extensionValue, 0, dup, 0, dup.length);
        return (dup);
    }

    /**
     * Returns the Extension in user readable form.
     */
    public String toString() {
        String s = "ObjectId: " + extensionId.toString();
        if (critical) {
            s += " Criticality=true\n";
        } else {
            s += " Criticality=false\n";
        }
        return (s);
    }

    // Value to mix up the hash
    private static final int hashMagic = 31;

    /**
     * Returns a hashcode value for this Extension.
     *
     * @return the hashcode value.
     */
    public int hashCode() {
	int h = 0;
	if (extensionValue != null) {
            byte[] val = extensionValue;
            int len = val.length;
            while (len > 0)
                h += len * val[--len];
	}
	h = h * hashMagic + extensionId.hashCode();
	h = h * hashMagic + (critical?1231:1237);
        return h;
    }

    /**
     * Compares this Extension for equality with the specified
     * object. If the <code>other</code> object is an
     * <code>instanceof</code> <code>Extension</code>, then
     * its encoded form is retrieved and compared with the
     * encoded form of this Extension.
     *
     * @param other the object to test for equality with this Extension.
     * @return true iff the other object is of type Extension, and the
     * criticality flag, object identifier and encoded extension value of 
     * the two Extensions match, false otherwise.
     */
    public boolean equals(Object other) {
        if (this == other)
            return true;
        if (!(other instanceof Extension))
            return false;
	Extension otherExt = (Extension) other;
	if (critical != otherExt.critical)
	    return false;
	if (!extensionId.equals(otherExt.extensionId))
	    return false;
        return Arrays.equals(extensionValue, otherExt.extensionValue);
    }
}