/*

 * Copyright 1997-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code 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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code 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 in the LICENSE file that

 * accompanied this code).

 *

 * 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 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.security.x509;

import java.io.IOException;

import java.io.OutputStream;

import java.util.Enumeration;

import sun.security.util.*;

/**

 * This class represents the Basic Constraints Extension.

 *

 * <p>The basic constraints extension identifies whether the subject of the

 * certificate is a CA and how deep a certification path may exist

 * through that CA.

 *

 * <pre>

 * The ASN.1 syntax for this extension is:

 * BasicConstraints ::= SEQUENCE {

 *     cA                BOOLEAN DEFAULT FALSE,

 *     pathLenConstraint INTEGER (0..MAX) OPTIONAL

 * }

 * </pre>

 * @author Amit Kapoor

 * @author Hemma Prafullchandra

 * @see CertAttrSet

 * @see Extension

 */

public class BasicConstraintsExtension extends Extension

implements CertAttrSet<String> {

    /**

     * Identifier for this attribute, to be used with the

     * get, set, delete methods of Certificate, x509 type.

     */

    public static final String IDENT = "x509.info.extensions.BasicConstraints";

    /**

     * Attribute names.

     */

    public static final String NAME = "BasicConstraints";

    public static final String IS_CA = "is_ca";

    public static final String PATH_LEN = "path_len";

    // Private data members

    private boolean     ca = false;

    private int pathLen = -1;

    // Encode this extension value

    private void encodeThis() throws IOException {

        if (ca == false && pathLen < 0) {

            this.extensionValue = null;

            return;

        }

        DerOutputStream out = new DerOutputStream();

        DerOutputStream tmp = new DerOutputStream();

        if (ca) {

            tmp.putBoolean(ca);

        }

        if (pathLen >= 0) {

            tmp.putInteger(pathLen);

        }

        out.write(DerValue.tag_Sequence, tmp);

        this.extensionValue = out.toByteArray();

    }

    /**

     * Default constructor for this object. The extension is marked

     * critical if the ca flag is true, false otherwise.

     *

     * @param ca true, if the subject of the Certificate is a CA.

     * @param len specifies the depth of the certification path.

     */

    public BasicConstraintsExtension(boolean ca, int len) throws IOException {

        this(Boolean.valueOf(ca), ca, len);

    }

    /**

     * Constructor for this object with specified criticality.

     *

     * @param critical true, if the extension should be marked critical

     * @param ca true, if the subject of the Certificate is a CA.

     * @param len specifies the depth of the certification path.

     */

    public BasicConstraintsExtension(Boolean critical, boolean ca, int len)

    throws IOException {

        this.ca = ca;

        this.pathLen = len;

        this.extensionId = PKIXExtensions.BasicConstraints_Id;

        this.critical = critical.booleanValue();

        encodeThis();

    }

    /**

     * Create the extension from the passed DER encoded value of the same.

     *

     * @param critical flag indicating if extension is critical or not

     * @param value an array containing the DER encoded bytes of the extension.

     * @exception ClassCastException if value is not an array of bytes

     * @exception IOException on error.

     */

     public BasicConstraintsExtension(Boolean critical, Object value)

         throws IOException

    {

         this.extensionId = PKIXExtensions.BasicConstraints_Id;

         this.critical = critical.booleanValue();

         this.extensionValue = (byte[]) value;

         DerValue val = new DerValue(this.extensionValue);

         if (val.tag != DerValue.tag_Sequence) {

             throw new IOException("Invalid encoding of BasicConstraints");

         }

         if (val.data == null) {

             // non-CA cert ("cA" field is FALSE by default), return -1

             return;

         }

         DerValue opt = val.data.getDerValue();

         if (opt.tag != DerValue.tag_Boolean) {

             // non-CA cert ("cA" field is FALSE by default), return -1

             return;

         }

         this.ca = opt.getBoolean();

         if (val.data.available() == 0) {

             // From PKIX profile:

             // Where pathLenConstraint does not appear, there is no

             // limit to the allowed length of the certification path.

             this.pathLen = Integer.MAX_VALUE;

             return;

         }

         opt = val.data.getDerValue();

         if (opt.tag != DerValue.tag_Integer) {

             throw new IOException("Invalid encoding of BasicConstraints");

         }

         this.pathLen = opt.getInteger();

         /*

          * Activate this check once again after PKIX profiling

          * is a standard and this check no longer imposes an

          * interoperability barrier.

          * if (ca) {

          *   if (!this.critical) {

          *   throw new IOException("Criticality cannot be false for CA.");

          *   }

          * }

          */

     }

     /**

      * Return user readable form of extension.

      */

     public String toString() {

         String s = super.toString() + "BasicConstraints:[\n";

         s += ((ca) ? ("  CA:true") : ("  CA:false")) + "\n";

         if (pathLen >= 0) {

             s += "  PathLen:" + pathLen + "\n";

         } else {

             s += "  PathLen: undefined\n";

         }

         return (s + "]\n");

     }

     /**

      * Encode this extension value to the output stream.

      *

      * @param out the DerOutputStream to encode the extension to.

      */

     public void encode(OutputStream out) throws IOException {

         DerOutputStream tmp = new DerOutputStream();

         if (extensionValue == null) {

             this.extensionId = PKIXExtensions.BasicConstraints_Id;

             if (ca) {

                 critical = true;

             } else {

                 critical = false;

             }

             encodeThis();

         }

         super.encode(tmp);

         out.write(tmp.toByteArray());

     }

    /**

     * Set the attribute value.

     */

    public void set(String name, Object obj) throws IOException {

        if (name.equalsIgnoreCase(IS_CA)) {

            if (!(obj instanceof Boolean)) {

              throw new IOException("Attribute value should be of type Boolean.");

            }

            ca = ((Boolean)obj).booleanValue();

        } else if (name.equalsIgnoreCase(PATH_LEN)) {

            if (!(obj instanceof Integer)) {

              throw new IOException("Attribute value should be of type Integer.");

            }

            pathLen = ((Integer)obj).intValue();

        } else {

          throw new IOException("Attribute name not recognized by " +

                                "CertAttrSet:BasicConstraints.");

        }

        encodeThis();

    }

    /**

     * Get the attribute value.

     */

    public Object get(String name) throws IOException {

        if (name.equalsIgnoreCase(IS_CA)) {

            return (Boolean.valueOf(ca));

        } else if (name.equalsIgnoreCase(PATH_LEN)) {

            return (Integer.valueOf(pathLen));

        } else {

          throw new IOException("Attribute name not recognized by " +

                                "CertAttrSet:BasicConstraints.");

        }

    }

    /**

     * Delete the attribute value.

     */

    public void delete(String name) throws IOException {

        if (name.equalsIgnoreCase(IS_CA)) {

            ca = false;

        } else if (name.equalsIgnoreCase(PATH_LEN)) {

            pathLen = -1;

        } else {

          throw new IOException("Attribute name not recognized by " +

                                "CertAttrSet:BasicConstraints.");

        }

        encodeThis();

    }

    /**

     * Return an enumeration of names of attributes existing within this

     * attribute.

     */

    public Enumeration<String> getElements() {

        AttributeNameEnumeration elements = new AttributeNameEnumeration();

        elements.addElement(IS_CA);

        elements.addElement(PATH_LEN);

        return (elements.elements());

    }

    /**

     * Return the name of this attribute.

     */

    public String getName() {

        return (NAME);

    }

}