libjava/classpath/gnu/java/security/sig/dss/DSSSignatureRawCodec.java

   1 /* DSSSignatureRawCodec.java --
   2    Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.
   3
   4 This file is a part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or (at
   9 your option) any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19 USA
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version.  */
  37
  38
  39 package gnu.java.security.sig.dss;
  40
  41 import gnu.java.security.Registry;
  42 import gnu.java.security.sig.ISignatureCodec;
  43
  44 import java.io.ByteArrayOutputStream;
  45 import java.math.BigInteger;
  46
  47 /**
  48  * <p>An object that implements the {@link ISignatureCodec} operations for the
  49  * <i>Raw</i> format to use with DSS signatures.</p>
  50  */
  51 public class DSSSignatureRawCodec implements ISignatureCodec
  52 {
  53
  54   // Constants and variables
  55   // -------------------------------------------------------------------------
  56
  57   // Constructor(s)
  58   // -------------------------------------------------------------------------
  59
  60   // implicit 0-arguments constructor
  61
  62   // Class methods
  63   // -------------------------------------------------------------------------
  64
  65   // Instance methods
  66   // -------------------------------------------------------------------------
  67
  68   // gnu.crypto.sig.ISignatureCodec interface implementation -----------------
  69
  70   public int getFormatID()
  71   {
  72     return RAW_FORMAT;
  73   }
  74
  75   /**
  76    * <p>Returns the encoded form of the designated DSS (Digital Signature
  77    * Standard) signature object according to the <i>Raw</i> format supported by
  78    * this library.</p>
  79    *
  80    * <p>The <i>Raw</i> format for a DSA signature, in this implementation, is a
  81    * byte sequence consisting of the following:</p>
  82    *
  83    * <ol>
  84    *            <li>4-byte magic consisting of the value of the literal
  85    *    {@link Registry#MAGIC_RAW_DSS_SIGNATURE},</li>
  86    *            <li>1-byte version consisting of the constant: 0x01,</li>
  87    *            <li>4-byte count of following bytes representing the DSS parameter
  88    *            <code>r</code> in internet order,</li>
  89    *            <li>n-bytes representation of a {@link BigInteger} obtained by invoking
  90    *    the <code>toByteArray()</code> method on the DSS parameter <code>r</code>,</li>
  91    *            <li>4-byte count of following bytes representing the DSS parameter
  92    *            <code>s</code>,</li>
  93    *            <li>n-bytes representation of a {@link BigInteger} obtained by invoking
  94    *    the <code>toByteArray()</code> method on the DSS parameter <code>s</code>.</li>
  95    * </ol>
  96    *
  97    * @param signature the signature to encode, consisting of the two DSS
  98    * parameters <code>r</code> and <code>s</code> as a {@link java.math.BigInteger}
  99    * array.
 100    * @return the <i>Raw</i> format encoding of the designated signature.
 101    * @exception IllegalArgumentException if the designated signature is not a
 102    * DSS (Digital Signature Standard) one.
 103    */
 104   public byte[] encodeSignature(Object signature)
 105   {
 106     BigInteger r, s;
 107     try
 108       {
 109         BigInteger[] sig = (BigInteger[]) signature;
 110         r = sig[0];
 111         s = sig[1];
 112       }
 113     catch (Exception x)
 114       {
 115         throw new IllegalArgumentException("key");
 116       }
 117
 118     ByteArrayOutputStream baos = new ByteArrayOutputStream();
 119
 120     // magic
 121     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[0]);
 122     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[1]);
 123     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[2]);
 124     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[3]);
 125
 126     // version
 127     baos.write(0x01);
 128
 129     // r
 130     byte[] buffer = r.toByteArray();
 131     int length = buffer.length;
 132     baos.write(length >>> 24);
 133     baos.write((length >>> 16) & 0xFF);
 134     baos.write((length >>> 8) & 0xFF);
 135     baos.write(length & 0xFF);
 136     baos.write(buffer, 0, length);
 137
 138     // s
 139     buffer = s.toByteArray();
 140     length = buffer.length;
 141     baos.write(length >>> 24);
 142     baos.write((length >>> 16) & 0xFF);
 143     baos.write((length >>> 8) & 0xFF);
 144     baos.write(length & 0xFF);
 145     baos.write(buffer, 0, length);
 146
 147     return baos.toByteArray();
 148   }
 149
 150   public Object decodeSignature(byte[] k)
 151   {
 152     // magic
 153     if (k[0] != Registry.MAGIC_RAW_DSS_SIGNATURE[0]
 154         || k[1] != Registry.MAGIC_RAW_DSS_SIGNATURE[1]
 155         || k[2] != Registry.MAGIC_RAW_DSS_SIGNATURE[2]
 156         || k[3] != Registry.MAGIC_RAW_DSS_SIGNATURE[3])
 157       {
 158         throw new IllegalArgumentException("magic");
 159       }
 160
 161     // version
 162     if (k[4] != 0x01)
 163       {
 164         throw new IllegalArgumentException("version");
 165       }
 166
 167     int i = 5;
 168     int l;
 169     byte[] buffer;
 170
 171     // r
 172     l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8
 173         | (k[i++] & 0xFF);
 174     buffer = new byte[l];
 175     System.arraycopy(k, i, buffer, 0, l);
 176     i += l;
 177     BigInteger r = new BigInteger(1, buffer);
 178
 179     // s
 180     l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8
 181         | (k[i++] & 0xFF);
 182     buffer = new byte[l];
 183     System.arraycopy(k, i, buffer, 0, l);
 184     i += l;
 185     BigInteger s = new BigInteger(1, buffer);
 186
 187     return new BigInteger[] { r, s };
 188   }
 189 }