/*

 * 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,

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 */

package java.security.cert;

import java.util.Set;

/**

 * Interface for an X.509 extension.

 *

 * <p>The extensions defined for X.509 v3

 * {@link X509Certificate Certificates} and v2

 * {@link X509CRL CRLs} (Certificate Revocation

 * Lists) provide methods

 * for associating additional attributes with users or public keys,

 * for managing the certification hierarchy, and for managing CRL

 * distribution. The X.509 extensions format also allows communities

 * to define private extensions to carry information unique to those

 * communities.

 *

 * <p>Each extension in a certificate/CRL may be designated as

 * critical or non-critical.  A certificate/CRL-using system (an application

 * validating a certificate/CRL) must reject the certificate/CRL if it

 * encounters a critical extension it does not recognize.  A non-critical

 * extension may be ignored if it is not recognized.

 * <p>

 * The ASN.1 definition for this is:

 * <pre>

 * Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension

 *

 * Extension  ::=  SEQUENCE  {

 *     extnId        OBJECT IDENTIFIER,

 *     critical      BOOLEAN DEFAULT FALSE,

 *     extnValue     OCTET STRING

 *                   -- contains a DER encoding of a value

 *                   -- of the type registered for use with

 *                   -- the extnId object identifier value

 * }

 * </pre>

 * Since not all extensions are known, the <code>getExtensionValue</code>

 * method returns the DER-encoded OCTET STRING of the

 * extension value (i.e., the <code>extnValue</code>). This can then

 * be handled by a <em>Class</em> that understands the extension.

 *

 * @author Hemma Prafullchandra

 */

public interface X509Extension {

    /**

     * Check if there is a critical extension that is not supported.

     *

     * @return <tt>true</tt> if a critical extension is found that is

     * not supported, otherwise <tt>false</tt>.

     */

    public boolean hasUnsupportedCriticalExtension();

    /**

     * Gets a Set of the OID strings for the extension(s) marked

     * CRITICAL in the certificate/CRL managed by the object

     * implementing this interface.

     *

     * Here is sample code to get a Set of critical extensions from an

     * X509Certificate and print the OIDs:

     * <pre><code>

     * InputStream inStrm = null;

     * X509Certificate cert = null;

     * try {

     *     inStrm = new FileInputStream("DER-encoded-Cert");

     *     CertificateFactory cf = CertificateFactory.getInstance("X.509");

     *     cert = (X509Certificate)cf.generateCertificate(inStrm);

     * } finally {

     *     if (inStrm != null) {

     *         inStrm.close();

     *     }

     * }<p>

     *

     * Set<String> critSet = cert.getCriticalExtensionOIDs();

     * if (critSet != null && !critSet.isEmpty()) {

     *     System.out.println("Set of critical extensions:");

     *     for (String oid : critSet) {

     *         System.out.println(oid);

     *     }

     * }

     * </code></pre>

     * @return a Set (or an empty Set if none are marked critical) of

     * the extension OID strings for extensions that are marked critical.

     * If there are no extensions present at all, then this method returns

     * null.

     */

    public Set<String> getCriticalExtensionOIDs();

    /**

     * Gets a Set of the OID strings for the extension(s) marked

     * NON-CRITICAL in the certificate/CRL managed by the object

     * implementing this interface.

     *

     * Here is sample code to get a Set of non-critical extensions from an

     * X509CRL revoked certificate entry and print the OIDs:

     * <pre><code>

     * InputStream inStrm = null;

     * CertificateFactory cf = null;

     * X509CRL crl = null;

     * try {

     *     inStrm = new FileInputStream("DER-encoded-CRL");

     *     cf = CertificateFactory.getInstance("X.509");

     *     crl = (X509CRL)cf.generateCRL(inStrm);

     * } finally {

     *     if (inStrm != null) {

     *         inStrm.close();

     *     }

     * }<p>

     *

     * byte[] certData = <DER-encoded certificate data>

     * ByteArrayInputStream bais = new ByteArrayInputStream(certData);

     * X509Certificate cert = (X509Certificate)cf.generateCertificate(bais);

     * bais.close();

     * X509CRLEntry badCert =

     *              crl.getRevokedCertificate(cert.getSerialNumber());<p>

     *

     * if (badCert != null) {

     *     Set<String> nonCritSet = badCert.getNonCriticalExtensionOIDs();<p>

     *     if (nonCritSet != null)

     *         for (String oid : nonCritSet) {

     *             System.out.println(oid);

     *         }

     * }

     * </code></pre>

     *

     * @return a Set (or an empty Set if none are marked non-critical) of

     * the extension OID strings for extensions that are marked non-critical.

     * If there are no extensions present at all, then this method returns

     * null.

     */

    public Set<String> getNonCriticalExtensionOIDs();

    /**

     * Gets the DER-encoded OCTET string for the extension value

     * (<em>extnValue</em>) identified by the passed-in <code>oid</code>

     * String.

     * The <code>oid</code> string is

     * represented by a set of nonnegative whole numbers separated

     * by periods.

     *

     * <p>For example:<br>

     * <table border=groove summary="Examples of OIDs and extension names">

     * <tr>

     * <th>OID <em>(Object Identifier)</em></th>

     * <th>Extension Name</th></tr>

     * <tr><td>2.5.29.14</td>

     * <td>SubjectKeyIdentifier</td></tr>

     * <tr><td>2.5.29.15</td>

     * <td>KeyUsage</td></tr>

     * <tr><td>2.5.29.16</td>

     * <td>PrivateKeyUsage</td></tr>

     * <tr><td>2.5.29.17</td>

     * <td>SubjectAlternativeName</td></tr>

     * <tr><td>2.5.29.18</td>

     * <td>IssuerAlternativeName</td></tr>

     * <tr><td>2.5.29.19</td>

     * <td>BasicConstraints</td></tr>

     * <tr><td>2.5.29.30</td>

     * <td>NameConstraints</td></tr>

     * <tr><td>2.5.29.33</td>

     * <td>PolicyMappings</td></tr>

     * <tr><td>2.5.29.35</td>

     * <td>AuthorityKeyIdentifier</td></tr>

     * <tr><td>2.5.29.36</td>

     * <td>PolicyConstraints</td></tr>

     * </table>

     *

     * @param oid the Object Identifier value for the extension.

     * @return the DER-encoded octet string of the extension value or

     * null if it is not present.

     */

    public byte[] getExtensionValue(String oid);

}