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    1   /*
    2    * Copyright (c) 2011, 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 javax.crypto.spec;
   27   
   28   import java.security.spec.AlgorithmParameterSpec;
   29   
   30   /**
   31    * Specifies the set of parameters required by a {@link
   32    * javax.crypto.Cipher} using the Galois/Counter Mode (GCM) mode.
   33    * <p>
   34    * Simple block cipher modes (such as CBC) generally require only an
   35    * initialization vector (such as {@code IvParameterSpec}),
   36    * but GCM needs these parameters:
   37    * <ul>
   38    * <li>{@code IV}: Initialization Vector (IV) </li>
   39    * <li>{@code tLen}: length (in bits) of authentication tag T</li>
   40    * </ul>
   41    * <p>
   42    * In addition to the parameters described here, other GCM inputs/output
   43    * (Additional Authenticated Data (AAD), Keys, block ciphers,
   44    * plain/ciphertext and authentication tags) are handled in the {@code
   45    * Cipher} class.
   46     <p>
   47    * Please see <a href="http://www.ietf.org/rfc/rfc5116.txt"> RFC 5116
   48    * </a> for more information on the Authenticated Encryption with
   49    * Associated Data (AEAD) algorithm, and <a href=
   50    * "http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf">
   51    * NIST Special Publication 800-38D</a>, "NIST Recommendation for Block
   52    * Cipher Modes of Operation:  Galois/Counter Mode (GCM) and GMAC."
   53    * <p>
   54    * The GCM specification states that {@code tLen} may only have the
   55    * values {128, 120, 112, 104, 96}, or {64, 32} for certain
   56    * applications.  Other values can be specified for this class, but not
   57    * all CSP implementations will support them.
   58    *
   59    * @see javax.crypto.Cipher
   60    *
   61    * @since 1.7
   62    */
   63   public class GCMParameterSpec implements AlgorithmParameterSpec {
   64   
   65       // Initialization Vector.  Could use IvParameterSpec, but that
   66       // would add extra copies.
   67       private byte[] iv;
   68   
   69       // Required Tag length (in bits).
   70       private int tLen;
   71   
   72       /**
   73        * Constructs a GCMParameterSpec using the specified authentication
   74        * tag bit-length and IV buffer.
   75        *
   76        * @param tLen the authentication tag length (in bits)
   77        * @param src the IV source buffer.  The contents of the buffer are
   78        * copied to protect against subsequent modification.
   79        *
   80        * @throws IllegalArgumentException if {@code tLen} is negative,
   81        * or {@code src} is null.
   82        */
   83       public GCMParameterSpec(int tLen, byte[] src) {
   84           if (src == null) {
   85               throw new IllegalArgumentException("src array is null");
   86           }
   87   
   88           init(tLen, src, 0, src.length);
   89       }
   90   
   91       /**
   92        * Constructs a GCMParameterSpec object using the specified
   93        * authentication tag bit-length and a subset of the specified
   94        * buffer as the IV.
   95        *
   96        * @param tLen the authentication tag length (in bits)
   97        * @param src the IV source buffer.  The contents of the
   98        * buffer are copied to protect against subsequent modification.
   99        * @param offset the offset in {@code src} where the IV starts
  100        * @param len the number of IV bytes
  101        *
  102        * @throws IllegalArgumentException if {@code tLen} is negative,
  103        * {@code src} is null, {@code len} or {@code offset} is negative,
  104        * or the sum of {@code offset} and {@code len} is greater than the
  105        * length of the {@code src} byte array.
  106        */
  107       public GCMParameterSpec(int tLen, byte[] src, int offset, int len) {
  108           init(tLen, src, offset, len);
  109       }
  110   
  111       /*
  112        * Check input parameters.
  113        */
  114       private void init(int tLen, byte[] src, int offset, int len) {
  115           if (tLen < 0) {
  116               throw new IllegalArgumentException(
  117                   "Length argument is negative");
  118           }
  119           this.tLen = tLen;
  120   
  121           // Input sanity check
  122           if ((src == null) ||(len < 0) || (offset < 0)
  123                   || ((len + offset) > src.length)) {
  124               throw new IllegalArgumentException("Invalid buffer arguments");
  125           }
  126   
  127           iv = new byte[len];
  128           System.arraycopy(src, offset, iv, 0, len);
  129       }
  130   
  131       /**
  132        * Returns the authentication tag length.
  133        *
  134        * @return the authentication tag length (in bits)
  135        */
  136       public int getTLen() {
  137           return tLen;
  138       }
  139   
  140       /**
  141        * Returns the Initialization Vector (IV).
  142        *
  143        * @return the IV.  Creates a new array each time this method
  144        * is called.
  145        */
  146       public byte[] getIV() {
  147           return iv.clone();
  148       }
  149   }

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