/*
 * Copyright  1999-2004 The Apache Software Foundation.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package com.sun.org.apache.xml.internal.security.algorithms.implementations;



import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.AlgorithmParameterSpec;

import com.sun.org.apache.xml.internal.security.algorithms.JCEMapper;
import com.sun.org.apache.xml.internal.security.algorithms.SignatureAlgorithmSpi;
import com.sun.org.apache.xml.internal.security.signature.XMLSignatureException;
import com.sun.org.apache.xml.internal.security.utils.Base64;
import com.sun.org.apache.xml.internal.security.utils.Constants;


/**
 *
 * @author $Author: vishal $
 */
public class SignatureDSA extends SignatureAlgorithmSpi {

   /** {@link java.util.logging} logging facility */
    static java.util.logging.Logger log = 
        java.util.logging.Logger.getLogger(SignatureDSA.class.getName());

   /** Field _URI */
   public static final String _URI = Constants.SignatureSpecNS + "dsa-sha1";

   /** Field algorithm */
   private java.security.Signature _signatureAlgorithm = null;

   /**
    * Method engineGetURI
    *
    * @inheritDoc
    */
   protected String engineGetURI() {
      return SignatureDSA._URI;
   }

   /**
    * Constructor SignatureDSA
    *
    * @throws XMLSignatureException
    */
   public SignatureDSA() throws XMLSignatureException {

      String algorithmID = JCEMapper.translateURItoJCEID(SignatureDSA._URI);
      if (true)
      	if (log.isLoggable(java.util.logging.Level.FINE))                                     log.log(java.util.logging.Level.FINE, "Created SignatureDSA using " + algorithmID);

      try {
         this._signatureAlgorithm = Signature.getInstance(algorithmID);
      } catch (java.security.NoSuchAlgorithmException ex) {
         Object[] exArgs = { algorithmID,
                             ex.getLocalizedMessage() };

         throw new XMLSignatureException("algorithms.NoSuchAlgorithm", exArgs);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineSetParameter(AlgorithmParameterSpec params)
           throws XMLSignatureException {

      try {
         this._signatureAlgorithm.setParameter(params);
      } catch (InvalidAlgorithmParameterException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected boolean engineVerify(byte[] signature)
           throws XMLSignatureException {

      try {
         if (true)
         	if (log.isLoggable(java.util.logging.Level.FINE))                                     log.log(java.util.logging.Level.FINE, "Called DSA.verify() on " + Base64.encode(signature));

         byte[] jcebytes = SignatureDSA.convertXMLDSIGtoASN1(signature);

         return this._signatureAlgorithm.verify(jcebytes);
      } catch (SignatureException ex) {
         throw new XMLSignatureException("empty", ex);
      } catch (IOException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineInitVerify(Key publicKey) throws XMLSignatureException {

      if (!(publicKey instanceof PublicKey)) {
         String supplied = publicKey.getClass().getName();
         String needed = PublicKey.class.getName();
         Object exArgs[] = { supplied, needed };

         throw new XMLSignatureException("algorithms.WrongKeyForThisOperation",
                                         exArgs);
      }

      try {
         this._signatureAlgorithm.initVerify((PublicKey) publicKey);
      } catch (InvalidKeyException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected byte[] engineSign() throws XMLSignatureException {

      try {
         byte jcebytes[] = this._signatureAlgorithm.sign();

         return SignatureDSA.convertASN1toXMLDSIG(jcebytes);
      } catch (IOException ex) {
         throw new XMLSignatureException("empty", ex);
      } catch (SignatureException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineInitSign(Key privateKey, SecureRandom secureRandom)
           throws XMLSignatureException {

      if (!(privateKey instanceof PrivateKey)) {
         String supplied = privateKey.getClass().getName();
         String needed = PrivateKey.class.getName();
         Object exArgs[] = { supplied, needed };

         throw new XMLSignatureException("algorithms.WrongKeyForThisOperation",
                                         exArgs);
      }

      try {
         this._signatureAlgorithm.initSign((PrivateKey) privateKey,
                                           secureRandom);
      } catch (InvalidKeyException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineInitSign(Key privateKey) throws XMLSignatureException {

      if (!(privateKey instanceof PrivateKey)) {
         String supplied = privateKey.getClass().getName();
         String needed = PrivateKey.class.getName();
         Object exArgs[] = { supplied, needed };

         throw new XMLSignatureException("algorithms.WrongKeyForThisOperation",
                                         exArgs);
      }

      try {
         this._signatureAlgorithm.initSign((PrivateKey) privateKey);
      } catch (InvalidKeyException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineUpdate(byte[] input) throws XMLSignatureException {

      try {
         this._signatureAlgorithm.update(input);
      } catch (SignatureException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineUpdate(byte input) throws XMLSignatureException {

      try {
         this._signatureAlgorithm.update(input);
      } catch (SignatureException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * @inheritDoc
    */
   protected void engineUpdate(byte buf[], int offset, int len)
           throws XMLSignatureException {

      try {
         this._signatureAlgorithm.update(buf, offset, len);
      } catch (SignatureException ex) {
         throw new XMLSignatureException("empty", ex);
      }
   }

   /**
    * Method engineGetJCEAlgorithmString
    *
    * @inheritDoc
    */
   protected String engineGetJCEAlgorithmString() {
      return this._signatureAlgorithm.getAlgorithm();
   }

   /**
    * Method engineGetJCEProviderName
    *
    * @inheritDoc
    */
   protected String engineGetJCEProviderName() {
      return this._signatureAlgorithm.getProvider().getName();
   }


   /**
    * Converts an ASN.1 DSA value to a XML Signature DSA Value.
    *
    * The JAVA JCE DSA Signature algorithm creates ASN.1 encoded (r,s) value
    * pairs; the XML Signature requires the core BigInteger values.
    *
    * @param asn1Bytes
    * @return the decode bytes
    *
    * @throws IOException
    * @see <A HREF="http://www.w3.org/TR/xmldsig-core/#dsa-sha1">6.4.1 DSA</A>
    */
   private static byte[] convertASN1toXMLDSIG(byte asn1Bytes[])
           throws IOException {

      byte rLength = asn1Bytes[3];
      int i;

      for (i = rLength; (i > 0) && (asn1Bytes[(4 + rLength) - i] == 0); i--);

      byte sLength = asn1Bytes[5 + rLength];
      int j;

      for (j = sLength;
              (j > 0) && (asn1Bytes[(6 + rLength + sLength) - j] == 0); j--);

      if ((asn1Bytes[0] != 48) || (asn1Bytes[1] != asn1Bytes.length - 2)
              || (asn1Bytes[2] != 2) || (i > 20)
              || (asn1Bytes[4 + rLength] != 2) || (j > 20)) {
         throw new IOException("Invalid ASN.1 format of DSA signature");
      } 
      byte xmldsigBytes[] = new byte[40];

      System.arraycopy(asn1Bytes, (4 + rLength) - i, xmldsigBytes, 20 - i,
                          i);
      System.arraycopy(asn1Bytes, (6 + rLength + sLength) - j, xmldsigBytes,
                          40 - j, j);

       return xmldsigBytes;      
   }

   /**
    * Converts a XML Signature DSA Value to an ASN.1 DSA value.
    *
    * The JAVA JCE DSA Signature algorithm creates ASN.1 encoded (r,s) value
    * pairs; the XML Signature requires the core BigInteger values.
    *
    * @param xmldsigBytes
    * @return the encoded ASN.1 bytes
    *
    * @throws IOException
    * @see <A HREF="http://www.w3.org/TR/xmldsig-core/#dsa-sha1">6.4.1 DSA</A>
    */
   private static byte[] convertXMLDSIGtoASN1(byte xmldsigBytes[])
           throws IOException {

      if (xmldsigBytes.length != 40) {
         throw new IOException("Invalid XMLDSIG format of DSA signature");
      }

      int i;

      for (i = 20; (i > 0) && (xmldsigBytes[20 - i] == 0); i--);

      int j = i;

      if (xmldsigBytes[20 - i] < 0) {
         j += 1;
      }

      int k;

      for (k = 20; (k > 0) && (xmldsigBytes[40 - k] == 0); k--);

      int l = k;

      if (xmldsigBytes[40 - k] < 0) {
         l += 1;
      }

      byte asn1Bytes[] = new byte[6 + j + l];

      asn1Bytes[0] = 48;
      asn1Bytes[1] = (byte) (4 + j + l);
      asn1Bytes[2] = 2;
      asn1Bytes[3] = (byte) j;

      System.arraycopy(xmldsigBytes, 20 - i, asn1Bytes, (4 + j) - i, i);

      asn1Bytes[4 + j] = 2;
      asn1Bytes[5 + j] = (byte) l;

      System.arraycopy(xmldsigBytes, 40 - k, asn1Bytes, (6 + j + l) - k, k);

      return asn1Bytes;
   }

   /**
    * Method engineSetHMACOutputLength
    *
    * @param HMACOutputLength
    * @throws XMLSignatureException
    */
   protected void engineSetHMACOutputLength(int HMACOutputLength)
           throws XMLSignatureException {
      throw new XMLSignatureException("algorithms.HMACOutputLengthOnlyForHMAC");
   }

   /**
    * Method engineInitSign
    *
    * @param signingKey
    * @param algorithmParameterSpec
    * @throws XMLSignatureException
    */
   protected void engineInitSign(
           Key signingKey, AlgorithmParameterSpec algorithmParameterSpec)
              throws XMLSignatureException {
      throw new XMLSignatureException(
         "algorithms.CannotUseAlgorithmParameterSpecOnDSA");
   }
}
