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  * @version $Revision: 1.1 $
  52  */
  53 public class DSSSignatureRawCodec implements ISignatureCodec
  54 {
  55
  56   // Constants and variables
  57   // -------------------------------------------------------------------------
  58
  59   // Constructor(s)
  60   // -------------------------------------------------------------------------
  61
  62   // implicit 0-arguments constructor
  63
  64   // Class methods
  65   // -------------------------------------------------------------------------
  66
  67   // Instance methods
  68   // -------------------------------------------------------------------------
  69
  70   // gnu.crypto.sig.ISignatureCodec interface implementation -----------------
  71
  72   public int getFormatID()
  73   {
  74     return RAW_FORMAT;
  75   }
  76
  77   /**
  78    * <p>Returns the encoded form of the designated DSS (Digital Signature
  79    * Standard) signature object according to the <i>Raw</i> format supported by
  80    * this library.</p>
  81    *
  82    * <p>The <i>Raw</i> format for a DSA signature, in this implementation, is a
  83    * byte sequence consisting of the following:</p>
  84    *
  85    * <ol>
  86    *            <li>4-byte magic consisting of the value of the literal
  87    *    {@link Registry#MAGIC_RAW_DSS_SIGNATURE},</li>
  88    *            <li>1-byte version consisting of the constant: 0x01,</li>
  89    *            <li>4-byte count of following bytes representing the DSS parameter
  90    *            <code>r</code> in internet order,</li>
  91    *            <li>n-bytes representation of a {@link BigInteger} obtained by invoking
  92    *    the <code>toByteArray()</code> method on the DSS parameter <code>r</code>,</li>
  93    *            <li>4-byte count of following bytes representing the DSS parameter
  94    *            <code>s</code>,</li>
  95    *            <li>n-bytes representation of a {@link BigInteger} obtained by invoking
  96    *    the <code>toByteArray()</code> method on the DSS parameter <code>s</code>.</li>
  97    * </ol>
  98    *
  99    * @param signature the signature to encode, consisting of the two DSS
 100    * parameters <code>r</code> and <code>s</code> as a {@link java.math.BigInteger}
 101    * array.
 102    * @return the <i>Raw</i> format encoding of the designated signature.
 103    * @exception IllegalArgumentException if the designated signature is not a
 104    * DSS (Digital Signature Standard) one.
 105    */
 106   public byte[] encodeSignature(Object signature)
 107   {
 108     BigInteger r, s;
 109     try
 110       {
 111         BigInteger[] sig = (BigInteger[]) signature;
 112         r = sig[0];
 113         s = sig[1];
 114       }
 115     catch (Exception x)
 116       {
 117         throw new IllegalArgumentException("key");
 118       }
 119
 120     ByteArrayOutputStream baos = new ByteArrayOutputStream();
 121
 122     // magic
 123     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[0]);
 124     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[1]);
 125     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[2]);
 126     baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[3]);
 127
 128     // version
 129     baos.write(0x01);
 130
 131     // r
 132     byte[] buffer = r.toByteArray();
 133     int length = buffer.length;
 134     baos.write(length >>> 24);
 135     baos.write((length >>> 16) & 0xFF);
 136     baos.write((length >>> 8) & 0xFF);
 137     baos.write(length & 0xFF);
 138     baos.write(buffer, 0, length);
 139
 140     // s
 141     buffer = s.toByteArray();
 142     length = buffer.length;
 143     baos.write(length >>> 24);
 144     baos.write((length >>> 16) & 0xFF);
 145     baos.write((length >>> 8) & 0xFF);
 146     baos.write(length & 0xFF);
 147     baos.write(buffer, 0, length);
 148
 149     return baos.toByteArray();
 150   }
 151
 152   public Object decodeSignature(byte[] k)
 153   {
 154     // magic
 155     if (k[0] != Registry.MAGIC_RAW_DSS_SIGNATURE[0]
 156         || k[1] != Registry.MAGIC_RAW_DSS_SIGNATURE[1]
 157         || k[2] != Registry.MAGIC_RAW_DSS_SIGNATURE[2]
 158         || k[3] != Registry.MAGIC_RAW_DSS_SIGNATURE[3])
 159       {
 160         throw new IllegalArgumentException("magic");
 161       }
 162
 163     // version
 164     if (k[4] != 0x01)
 165       {
 166         throw new IllegalArgumentException("version");
 167       }
 168
 169     int i = 5;
 170     int l;
 171     byte[] buffer;
 172
 173     // r
 174     l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8
 175         | (k[i++] & 0xFF);
 176     buffer = new byte[l];
 177     System.arraycopy(k, i, buffer, 0, l);
 178     i += l;
 179     BigInteger r = new BigInteger(1, buffer);
 180
 181     // s
 182     l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8
 183         | (k[i++] & 0xFF);
 184     buffer = new byte[l];
 185     System.arraycopy(k, i, buffer, 0, l);
 186     i += l;
 187     BigInteger s = new BigInteger(1, buffer);
 188
 189     return new BigInteger[] { r, s };
 190   }
 191 }