/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * 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: mullan $
 */
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 (log.isLoggable(java.util.logging.Level.FINE))
            log.log(java.util.logging.Level.FINE, "Created SignatureDSA using " + algorithmID);

        String provider = JCEMapper.getProviderId();
        try {
            if (provider == null) {
                this._signatureAlgorithm = Signature.getInstance(algorithmID);
            } else {
                this._signatureAlgorithm =
                    Signature.getInstance(algorithmID, provider);
            }
        } catch (java.security.NoSuchAlgorithmException ex) {
            Object[] exArgs = { algorithmID, ex.getLocalizedMessage() };
            throw new XMLSignatureException("algorithms.NoSuchAlgorithm", exArgs);
        } catch (java.security.NoSuchProviderException 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 (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) {
            // reinstantiate Signature object to work around bug in JDK
            // see: http://bugs.sun.com/view_bug.do?bug_id=4953555
            Signature sig = this._signatureAlgorithm;
            try {
                this._signatureAlgorithm = Signature.getInstance
                    (_signatureAlgorithm.getAlgorithm());
            } catch (Exception e) {
                // this shouldn't occur, but if it does, restore previous
                // Signature
                if (log.isLoggable(java.util.logging.Level.FINE)) {
                    log.log(java.util.logging.Level.FINE, "Exception when reinstantiating Signature:" + e);
                }
                this._signatureAlgorithm = sig;
            }
            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");
    }
}