1 /*
   2  * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.security.cert;
  27 
  28 import java.io.IOException;
  29 import java.io.OutputStream;
  30 import java.io.Serializable;
  31 
  32 /**
  33  * This interface represents an X.509 extension.
  34  *
  35  * <p>
  36  * Extensions provide a means of associating additional attributes with users
  37  * or public keys and for managing a certification hierarchy.  The extension
  38  * format also allows communities to define private extensions to carry
  39  * information unique to those communities.
  40  *
  41  * <p>
  42  * Each extension contains an object identifier, a criticality setting
  43  * indicating whether it is a critical or a non-critical extension, and
  44  * and an ASN.1 DER-encoded value. Its ASN.1 definition is:
  45  *
  46  * <pre>
  47  *
  48  *     Extension ::= SEQUENCE {
  49  *         extnId        OBJECT IDENTIFIER,
  50  *         critical      BOOLEAN DEFAULT FALSE,
  51  *         extnValue     OCTET STRING
  52  *                 -- contains a DER encoding of a value
  53  *                 -- of the type registered for use with
  54  *                 -- the extnId object identifier value
  55  *     }
  56  *
  57  * </pre>
  58  *
  59  * <p>
  60  * This interface is designed to provide access to a single extension,
  61  * unlike {@link java.security.cert.X509Extension} which is more suitable
  62  * for accessing a set of extensions.
  63  *
  64  * @since 1.7
  65  */
  66 public interface Extension {
  67 
  68     /**
  69      * Gets the extensions's object identifier.
  70      *
  71      * @return the object identifier as a String
  72      */
  73     String getId();
  74 
  75     /**
  76      * Gets the extension's criticality setting.
  77      *
  78      * @return true if this is a critical extension.
  79      */
  80     boolean isCritical();
  81 
  82     /**
  83      * Gets the extensions's DER-encoded value. Note, this is the bytes
  84      * that are encoded as an OCTET STRING. It does not include the OCTET
  85      * STRING tag and length.
  86      *
  87      * @return a copy of the extension's value, or <code>null</code> if no
  88      *    extension value is present.
  89      */
  90     byte[] getValue();
  91 
  92     /**
  93      * Generates the extension's DER encoding and writes it to the output
  94      * stream.
  95      *
  96      * @param out the output stream
  97      * @exception IOException on encoding or output error.
  98      * @exception NullPointerException if <code>out</code> is <code>null</code>.
  99      */
 100     void encode(OutputStream out) throws IOException;
 101 }