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

/* DSSSignatureRawCodec.java --
   Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

GNU Classpath 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 for more details.

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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package gnu.java.security.sig.dss;

import gnu.java.security.Registry;
import gnu.java.security.sig.ISignatureCodec;

import java.io.ByteArrayOutputStream;
import java.math.BigInteger;

/**
 * An object that implements the {@link ISignatureCodec} operations for the
 * <i>Raw</i> format to use with DSS signatures.
 */
public class DSSSignatureRawCodec
    implements ISignatureCodec
{
  public int getFormatID()
  {
    return RAW_FORMAT;
  }

  /**
   * Returns the encoded form of the designated DSS (Digital Signature Standard)
   * signature object according to the <i>Raw</i> format supported by this
   * library.
   * <p>
   * The <i>Raw</i> format for a DSA signature, in this implementation, is a
   * byte sequence consisting of the following:
   * <ol>
   * <li>4-byte magic consisting of the value of the literal
   * {@link Registry#MAGIC_RAW_DSS_SIGNATURE},</li>
   * <li>1-byte version consisting of the constant: 0x01,</li>
   * <li>4-byte count of following bytes representing the DSS parameter
   * <code>r</code> in internet order,</li>
   * <li>n-bytes representation of a {@link BigInteger} obtained by invoking
   * the <code>toByteArray()</code> method on the DSS parameter <code>r</code>,
   * </li>
   * <li>4-byte count of following bytes representing the DSS parameter
   * <code>s</code>,</li>
   * <li>n-bytes representation of a {@link BigInteger} obtained by invoking
   * the <code>toByteArray()</code> method on the DSS parameter <code>s</code>.
   * </li>
   * </ol>
   *
   * @param signature the signature to encode, consisting of the two DSS
   *          parameters <code>r</code> and <code>s</code> as a
   *          {@link BigInteger} array.
   * @return the <i>Raw</i> format encoding of the designated signature.
   * @exception IllegalArgumentException if the designated signature is not a
   *              DSS (Digital Signature Standard) one.
   */
  public byte[] encodeSignature(Object signature)
  {
    BigInteger r, s;
    try
      {
        BigInteger[] sig = (BigInteger[]) signature;
        r = sig[0];
        s = sig[1];
      }
    catch (Exception x)
      {
        throw new IllegalArgumentException("signature");
      }
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    // magic
    baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[0]);
    baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[1]);
    baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[2]);
    baos.write(Registry.MAGIC_RAW_DSS_SIGNATURE[3]);
    // version
    baos.write(0x01);
    // r
    byte[] buffer = r.toByteArray();
    int length = buffer.length;
    baos.write( length >>> 24);
    baos.write((length >>> 16) & 0xFF);
    baos.write((length >>> 8) & 0xFF);
    baos.write(length & 0xFF);
    baos.write(buffer, 0, length);
    // s
    buffer = s.toByteArray();
    length = buffer.length;
    baos.write( length >>> 24);
    baos.write((length >>> 16) & 0xFF);
    baos.write((length >>> 8) & 0xFF);
    baos.write(length & 0xFF);
    baos.write(buffer, 0, length);
    return baos.toByteArray();
  }

  public Object decodeSignature(byte[] k)
  {
    // magic
    if (k[0] != Registry.MAGIC_RAW_DSS_SIGNATURE[0]
        || k[1] != Registry.MAGIC_RAW_DSS_SIGNATURE[1]
        || k[2] != Registry.MAGIC_RAW_DSS_SIGNATURE[2]
        || k[3] != Registry.MAGIC_RAW_DSS_SIGNATURE[3])
      throw new IllegalArgumentException("magic");
    // version
    if (k[4] != 0x01)
      throw new IllegalArgumentException("version");

    int i = 5;
    int l;
    byte[] buffer;
    // r
    l =  k[i++]         << 24
      | (k[i++] & 0xFF) << 16
      | (k[i++] & 0xFF) << 8
      | (k[i++] & 0xFF);
    buffer = new byte[l];
    System.arraycopy(k, i, buffer, 0, l);
    i += l;
    BigInteger r = new BigInteger(1, buffer);
    // s
    l =  k[i++]         << 24
      | (k[i++] & 0xFF) << 16
      | (k[i++] & 0xFF) << 8
      | (k[i++] & 0xFF);
    buffer = new byte[l];
    System.arraycopy(k, i, buffer, 0, l);
    i += l;
    BigInteger s = new BigInteger(1, buffer);
    return new BigInteger[] { r, s };
  }
}