/*
 *  SSHTools - Java SSH2 API
 *
 *  Copyright (C) 2002-2003 Lee David Painter and Contributors.
 *
 *  Contributions made by:
 *
 *  Brett Smith
 *  Richard Pernavas
 *  Erwin Bolwidt
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public License
 *  as published by the Free Software Foundation; either version 2 of
 *  the License, or (at your option) any later version.
 *
 *  You may also distribute it and/or modify it under the terms of the
 *  Apache style J2SSH Software License. A copy of which should have
 *  been provided with the distribution.
 *
 *  This program 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
 *  License document supplied with your distribution for more details.
 *
 */
package com.sshtools.j2ssh.openssh;

import com.sshtools.j2ssh.util.SimpleASNReader;
import com.sshtools.j2ssh.util.SimpleASNWriter;

import java.io.IOException;

import java.math.BigInteger;

import java.security.spec.DSAPrivateKeySpec;
import java.security.spec.DSAPublicKeySpec;
import java.security.spec.KeySpec;


/**
 *
 *
 * @author $author$
 * @version $Revision: 1.12 $
 */
public class DSAKeyInfo implements KeyInfo {
    private BigInteger p;
    private BigInteger q;
    private BigInteger g;
    private BigInteger x;
    private BigInteger y;

    /**
     * Creates a new DSAKeyInfo object.
     *
     * @param p
     * @param q
     * @param g
     * @param x
     * @param y
     */
    public DSAKeyInfo(BigInteger p, BigInteger q, BigInteger g, BigInteger x,
        BigInteger y) {
        this.p = p;
        this.q = q;
        this.g = g;
        this.x = x;
        this.y = y;
    }

    /**
     *
     *
     * @return
     */
    public BigInteger getG() {
        return g;
    }

    /**
     *
     *
     * @return
     */
    public BigInteger getP() {
        return p;
    }

    /**
     *
     *
     * @return
     */
    public BigInteger getQ() {
        return q;
    }

    /**
     *
     *
     * @return
     */
    public BigInteger getX() {
        return x;
    }

    /**
     *
     *
     * @return
     */
    public BigInteger getY() {
        return y;
    }

    /**
     *
     *
     * @return
     */
    public KeySpec getPrivateKeySpec() {
        return new DSAPrivateKeySpec(x, p, q, g);
    }

    /**
     *
     *
     * @return
     */
    public KeySpec getPublicKeySpec() {
        return new DSAPublicKeySpec(y, p, q, g);
    }

    /**
     *
     *
     * @param asn
     *
     * @return
     *
     * @throws IOException
     */
    public static DSAKeyInfo getDSAKeyInfo(SimpleASNReader asn)
        throws IOException {
        asn.assertByte(0x30); // SEQUENCE

        int length = asn.getLength();
        asn.assertByte(0x02); // INTEGER (version)

        byte[] version = asn.getData();
        asn.assertByte(0x02); // INTEGER (p)

        byte[] paramP = asn.getData();
        asn.assertByte(0x02); // INTEGER (q)

        byte[] paramQ = asn.getData();
        asn.assertByte(0x02); // INTEGER (g)

        byte[] paramG = asn.getData();
        asn.assertByte(0x02); // INTEGER (y)

        byte[] paramY = asn.getData();
        asn.assertByte(0x02); // INTEGER (x)

        byte[] paramX = asn.getData();

        return new DSAKeyInfo(new BigInteger(paramP), new BigInteger(paramQ),
            new BigInteger(paramG), new BigInteger(paramX),
            new BigInteger(paramY));
    }

    /**
     *
     *
     * @param asn
     * @param keyInfo
     */
    public static void writeDSAKeyInfo(SimpleASNWriter asn, DSAKeyInfo keyInfo) {
        // Write to a substream temporarily.
        // This code needs to know the length of the substream before it can write the data from
        // the substream to the main stream.
        SimpleASNWriter asn2 = new SimpleASNWriter();
        asn2.writeByte(0x02); // INTEGER (version)

        byte[] version = new byte[1];
        asn2.writeData(version);
        asn2.writeByte(0x02); // INTEGER (p)
        asn2.writeData(keyInfo.getP().toByteArray());
        asn2.writeByte(0x02); // INTEGER (q)
        asn2.writeData(keyInfo.getQ().toByteArray());
        asn2.writeByte(0x02); // INTEGER (g)
        asn2.writeData(keyInfo.getG().toByteArray());
        asn2.writeByte(0x02); // INTEGER (y)
        asn2.writeData(keyInfo.getY().toByteArray());
        asn2.writeByte(0x02); // INTEGER (x)
        asn2.writeData(keyInfo.getX().toByteArray());

        byte[] dsaKeyEncoded = asn2.toByteArray();
        asn.writeByte(0x30); // SEQUENCE
        asn.writeData(dsaKeyEncoded);
    }
}
