/*
 *
 * MariaDB Client for Java
 *
 * Copyright (c) 2012-2014 Monty Program Ab.
 * Copyright (c) 2015-2017 MariaDB Ab.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along
 * with this library; if not, write to Monty Program Ab info@montyprogram.com.
 *
 * This particular MariaDB Client for Java file is work
 * derived from a Drizzle-JDBC. Drizzle-JDBC file which is covered by subject to
 * the following copyright and notice provisions:
 *
 * Copyright (c) 2009-2011, Marcus Eriksson
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this list
 * of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice, this
 * list of conditions and the following disclaimer in the documentation and/or
 * other materials provided with the distribution.
 *
 * Neither the name of the driver nor the names of its contributors may not be
 * used to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS  AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 */

package org.mariadb.jdbc.internal.com.send;


import org.mariadb.jdbc.internal.com.send.ed25519.math.GroupElement;
import org.mariadb.jdbc.internal.com.send.ed25519.math.ed25519.ScalarOps;
import org.mariadb.jdbc.internal.com.send.ed25519.spec.EdDSANamedCurveTable;
import org.mariadb.jdbc.internal.com.send.ed25519.spec.EdDSAParameterSpec;
import org.mariadb.jdbc.internal.io.output.PacketOutputStream;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.sql.SQLException;
import java.util.Arrays;

public class SendEd25519PasswordAuthPacket extends AbstractAuthSwitchSendResponsePacket implements InterfaceAuthSwitchSendResponsePacket {

    public SendEd25519PasswordAuthPacket(String password, byte[] authData, int packSeq, String passwordCharacterEncoding) {
        super(packSeq, authData, password, passwordCharacterEncoding);
    }

    /**
     * Send Ed25519 plugin authentication result.
     *
     * @param pos database socket
     * @throws IOException if socket error occur
     * @throws SQLException if other kind of error occur
     */
    public void send(PacketOutputStream pos) throws IOException, SQLException {

        if (password == null || password.isEmpty()) {
            pos.writeEmptyPacket(packSeq);
            return;
        }

        pos.startPacket(packSeq);
        pos.write(ed25519SignWithPassword(password, authData, passwordCharacterEncoding));
        pos.flush();

    }


    /**
     * The client signs the random seed from server, using the password as a private key.
     * The server will verifies the signature using the public key from mysql.user table.
     *
     * @param password                  password
     * @param seed                      server seed
     * @param passwordCharacterEncoding password encoding
     * @return signed hash
     * @throws SQLException  if anything wrong occur
     */
    private static byte[] ed25519SignWithPassword(final String password, final byte[] seed, String passwordCharacterEncoding)
            throws SQLException {


        try {
            byte[] bytePwd;
            if (passwordCharacterEncoding != null && !passwordCharacterEncoding.isEmpty()) {
                bytePwd = password.getBytes(passwordCharacterEncoding);
            } else {
                bytePwd = password.getBytes();
            }

            MessageDigest hash = MessageDigest.getInstance("SHA-512");

            int mlen = seed.length;
            byte[] sm = new byte[64 + mlen];

            byte[] az = hash.digest(bytePwd);
            az[0] &= 248;
            az[31] &= 63;
            az[31] |= 64;

            System.arraycopy(seed, 0, sm, 64, mlen);
            System.arraycopy(az, 32, sm, 32, 32);

            byte[] buff = Arrays.copyOfRange(sm, 32, 96);
            hash.reset();
            byte[] nonce = hash.digest(buff);

            ScalarOps scalar = new ScalarOps();

            EdDSAParameterSpec spec = EdDSANamedCurveTable.getByName("Ed25519");
            GroupElement elementAvalue = spec.getB().scalarMultiply(az);
            byte[] elementAarray = elementAvalue.toByteArray();
            System.arraycopy(elementAarray, 0, sm, 32, elementAarray.length);

            nonce = scalar.reduce(nonce);
            GroupElement elementRvalue = spec.getB().scalarMultiply(nonce);
            byte[] elementRarray = elementRvalue.toByteArray();
            System.arraycopy(elementRarray, 0, sm, 0, elementRarray.length);

            hash.reset();
            byte[] hram = hash.digest(sm);
            hram = scalar.reduce(hram);
            byte[] tt = scalar.multiplyAndAdd(hram, az, nonce);
            System.arraycopy(tt, 0, sm, 32, tt.length);

            return Arrays.copyOfRange(sm, 0, 64);

        } catch (NoSuchAlgorithmException e) {
            throw new SQLException("Could not use SHA-512, failing", e);
        } catch (UnsupportedEncodingException use) {
            throw new SQLException("Unsupported encoding '" + passwordCharacterEncoding + "' (option passwordCharacterEncoding)", use);
        }

    }

}
