path: root/gnu/java/security/key/dss/DSSKeyPairX509Codec.java

/* DSSKeyPairX509Codec.java -- X.509 Encoding/Decoding handler
   Copyright (C) 2006, 2014 Free Software Foundation, Inc.

This file is 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, 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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along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, 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
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package gnu.java.security.key.dss;

import gnu.java.security.OID;
import gnu.java.security.Registry;
import gnu.java.security.der.BitString;
import gnu.java.security.der.DER;
import gnu.java.security.der.DERReader;
import gnu.java.security.der.DERValue;
import gnu.java.security.der.DERWriter;
import gnu.java.security.key.IKeyPairCodec;
import gnu.java.security.util.DerUtil;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.InvalidParameterException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.ArrayList;

/**
 * An implementation of an {@link IKeyPairCodec} that knows how to encode /
 * decode X.509 ASN.1 external representation of DSS public keys.
 */
public class DSSKeyPairX509Codec
    implements IKeyPairCodec
{
  private static final OID DSA_ALG_OID = new OID(Registry.DSA_OID_STRING);

  // implicit 0-arguments constructor

  public int getFormatID()
  {
    return X509_FORMAT;
  }

  /**
   * Returns the X.509 ASN.1 <i>SubjectPublicKeyInfo</i> representation of a
   * DSA public key. The ASN.1 specification, as defined in RFC-3280, and
   * RFC-2459, is as follows:
   *
   * <pre>
   *   SubjectPublicKeyInfo ::= SEQUENCE {
   *     algorithm         AlgorithmIdentifier,
   *     subjectPublicKey  BIT STRING
   *   }
   *
   *   AlgorithmIdentifier ::= SEQUENCE {
   *     algorithm   OBJECT IDENTIFIER,
   *     parameters  ANY DEFINED BY algorithm OPTIONAL
   *   }
   *
   *   DssParams ::= SEQUENCE {
   *     p   INTEGER,
   *     q   INTEGER,
   *     g   INTEGER
   *   }
   * </pre>
   * <p>
   * Note that RFC-3280 (page 79) implies that some certificates MAY have an
   * absent, or NULL, parameters field in their AlgorithmIdentifier element,
   * implying that those parameters MUST be <i>inherited</i> from another
   * certificate. This implementation, encodes a <i>NULL</i> element as the DER
   * value of the parameters field when such is the case.
   * <p>
   * The <i>subjectPublicKey</i> field, which is a BIT STRING, contains the
   * DER-encoded form of the DSA public key as an INTEGER.
   *
   * <pre>
   *       DSAPublicKey ::= INTEGER -- public key, Y
   * </pre>
   *
   * @param key the {@link PublicKey} instance to encode. MUST be an instance of
   *          {@link DSSPublicKey}.
   * @return the ASN.1 representation of the <i>SubjectPublicKeyInfo</i> in an
   *         X.509 certificate.
   * @throw InvalidParameterException if <code>key</code> is not an instance
   *        of {@link DSSPublicKey} or if an exception occurs during the
   *        marshalling process.
   */
  public byte[] encodePublicKey(PublicKey key)
  {
    if (! (key instanceof DSSPublicKey))
      throw new InvalidParameterException("key");

    DERValue derOID = new DERValue(DER.OBJECT_IDENTIFIER, DSA_ALG_OID);

    DSSPublicKey dssKey = (DSSPublicKey) key;
    DERValue derParams;
    if (dssKey.hasInheritedParameters())
      derParams = new DERValue(DER.NULL, null);
    else
      {
        BigInteger p = dssKey.getParams().getP();
        BigInteger q = dssKey.getParams().getQ();
        BigInteger g = dssKey.getParams().getG();

        DERValue derP = new DERValue(DER.INTEGER, p);
        DERValue derQ = new DERValue(DER.INTEGER, q);
        DERValue derG = new DERValue(DER.INTEGER, g);

        ArrayList<DERValue> params = new ArrayList<DERValue>(3);
        params.add(derP);
        params.add(derQ);
        params.add(derG);
        derParams = new DERValue(DER.CONSTRUCTED | DER.SEQUENCE, params);
      }

    ArrayList<DERValue> algorithmID = new ArrayList<DERValue>(2);
    algorithmID.add(derOID);
    algorithmID.add(derParams);
    DERValue derAlgorithmID = new DERValue(DER.CONSTRUCTED | DER.SEQUENCE,
                                           algorithmID);

    BigInteger y = dssKey.getY();
    DERValue derDSAPublicKey = new DERValue(DER.INTEGER, y);
    byte[] yBytes = derDSAPublicKey.getEncoded();
    DERValue derSPK = new DERValue(DER.BIT_STRING, new BitString(yBytes));

    ArrayList<DERValue> spki = new ArrayList<DERValue>(2);
    spki.add(derAlgorithmID);
    spki.add(derSPK);
    DERValue derSPKI = new DERValue(DER.CONSTRUCTED | DER.SEQUENCE, spki);

    byte[] result;
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try
      {
        DERWriter.write(baos, derSPKI);
        result = baos.toByteArray();
      }
    catch (IOException x)
      {
        InvalidParameterException e = new InvalidParameterException(x.getMessage());
        e.initCause(x);
        throw e;
      }
    return result;
  }

  /**
   * @throws InvalidParameterException ALWAYS.
   */
  public byte[] encodePrivateKey(PrivateKey key)
  {
    throw new InvalidParameterException("Wrong format for private keys");
  }

  /**
   * @param input the byte array to unmarshall into a valid DSS
   *          {@link PublicKey} instance. MUST NOT be null.
   * @return a new instance of a {@link DSSPublicKey} decoded from the
   *         <i>SubjectPublicKeyInfo</i> material in an X.509 certificate.
   * @throw InvalidParameterException if an exception occurs during the
   *        unmarshalling process.
   */
  public PublicKey decodePublicKey(byte[] input)
  {
    if (input == null)
      throw new InvalidParameterException("Input bytes MUST NOT be null");

    BigInteger p = null;
    BigInteger g = null;
    BigInteger q = null;
    BigInteger y;
    DERReader der = new DERReader(input);
    try
      {
        DERValue derSPKI = der.read();
        DerUtil.checkIsConstructed(derSPKI, "Wrong SubjectPublicKeyInfo field");

        DERValue derAlgorithmID = der.read();
        DerUtil.checkIsConstructed(derAlgorithmID, "Wrong AlgorithmIdentifier field");

        DERValue derOID = der.read();
        if (! (derOID.getValue() instanceof OID))
          throw new InvalidParameterException("Wrong Algorithm field");

        OID algOID = (OID) derOID.getValue();
        if (! algOID.equals(DSA_ALG_OID))
          throw new InvalidParameterException("Unexpected OID: " + algOID);

        DERValue val = der.read();
        // RFC-3280, page 79 states: "If the subjectPublicKeyInfo field of the
        // certificate contains an algorithm field with null parameters or
        // parameters are omitted, compare the certificate subjectPublicKey
        // algorithm to the working_public_key_algorithm.  If the certificate
        // subjectPublicKey algorithm and the working_public_key_algorithm are
        // different, set the working_public_key_parameters to null."
        // in other words, the parameters field of an AlgorithmIdentifier
        // element MAY NOT be present at all, or if present MAY be NULL!
        // the Mauve test ValidDSAParameterInheritenceTest5, in
        // gnu.testlet.java.security.cert.pkix.pkits, is/was failing because
        // of this.
        if (val.getTag() == DER.NULL)
          val = der.read();
        else if (val.isConstructed())
          {
            val = der.read();
            DerUtil.checkIsBigInteger(val, "Wrong P field");
            p = (BigInteger) val.getValue();
            val = der.read();
            DerUtil.checkIsBigInteger(val, "Wrong Q field");
            q = (BigInteger) val.getValue();
            val = der.read();
            DerUtil.checkIsBigInteger(val, "Wrong G field");
            g = (BigInteger) val.getValue();

            val = der.read();
          }

        if (! (val.getValue() instanceof BitString))
          throw new InvalidParameterException("Wrong SubjectPublicKey field");

        byte[] yBytes = ((BitString) val.getValue()).toByteArray();

        DERReader dsaPub = new DERReader(yBytes);
        val = dsaPub.read();
        DerUtil.checkIsBigInteger(val, "Wrong Y field");
        y = (BigInteger) val.getValue();
      }
    catch (IOException x)
      {
        InvalidParameterException e = new InvalidParameterException(x.getMessage());
        e.initCause(x);
        throw e;
      }
    return new DSSPublicKey(Registry.X509_ENCODING_ID, p, q, g, y);
  }

  /**
   * @throws InvalidParameterException ALWAYS.
   */
  public PrivateKey decodePrivateKey(byte[] input)
  {
    throw new InvalidParameterException("Wrong format for private keys");
  }
}