/*

 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5.internal.crypto;

import sun.security.krb5.Confounder;

import sun.security.krb5.KrbCryptoException;

import sun.security.krb5.internal.*;

abstract class DesCbcEType extends EType {

    protected abstract byte[] calculateChecksum(byte[] data, int size)

        throws KrbCryptoException;

    public int blockSize() {

        return 8;

    }

    public int keyType() {

        return Krb5.KEYTYPE_DES;

    }

    public int keySize() {

        return 8;

    }

    /**

     * Encrypts the data using DES in CBC mode.

     * @param data the buffer for plain text.

     * @param key the key to encrypt the data.

     * @return the buffer for encrypted data.

     *

     * @written by Yanni Zhang, Dec 6 99.

     */

    public byte[] encrypt(byte[] data, byte[] key, int usage)

         throws KrbCryptoException {

        byte[] ivec = new byte[keySize()];

        return encrypt(data, key, ivec, usage);

    }

    /**

     * Encrypts the data using DES in CBC mode.

     * @param data the buffer for plain text.

     * @param key the key to encrypt the data.

     * @param ivec initialization vector.

     * @return buffer for encrypted data.

     *

     * @modified by Yanni Zhang, Feb 24 00.

     */

    public byte[] encrypt(byte[] data, byte[] key, byte[] ivec,

        int usage) throws KrbCryptoException {

        /*

         * To meet export control requirements, double check that the

         * key being used is no longer than 64 bits.

         *

         * Note that from a protocol point of view, an

         * algorithm that is not DES will be rejected before this

         * point. Also, a  DES key that is not 64 bits will be

         * rejected by a good implementations of JCE.

         */

        if (key.length > 8)

        throw new KrbCryptoException("Invalid DES Key!");

        int new_size = data.length + confounderSize() + checksumSize();

        byte[] new_data;

        byte pad;

        /*Data padding: using Kerberos 5 GSS-API mechanism (1.2.2.3), Jun 1996.

         *Before encryption, plain text data is padded to the next highest multiple of blocksize.

         *by appending between 1 and 8 bytes, the value of each such byte being the total number

         *of pad bytes. For example, if new_size = 10, blockSize is 8, we should pad 2 bytes,

         *and the value of each byte is 2.

         *If plaintext data is a multiple of blocksize, we pad a 8 bytes of 8.

         */

        if (new_size % blockSize() == 0) {

            new_data = new byte[new_size + blockSize()];

            pad = (byte)8;

        }

        else {

            new_data = new byte[new_size + blockSize() - new_size % blockSize()];

            pad = (byte)(blockSize() - new_size % blockSize());

        }

        for (int i = new_size; i < new_data.length; i++) {

            new_data[i] = pad;

        }

        byte[] conf = Confounder.bytes(confounderSize());

        System.arraycopy(conf, 0, new_data, 0, confounderSize());

        System.arraycopy(data, 0, new_data, startOfData(), data.length);

        byte[] cksum = calculateChecksum(new_data, new_data.length);

        System.arraycopy(cksum, 0, new_data, startOfChecksum(),

                         checksumSize());

        byte[] cipher = new byte[new_data.length];

        Des.cbc_encrypt(new_data, cipher, key, ivec, true);

        return cipher;

    }

    /**

     * Decrypts the data using DES in CBC mode.

     * @param cipher the input buffer.

     * @param key the key to decrypt the data.

     *

     * @written by Yanni Zhang, Dec 6 99.

     */

    public byte[] decrypt(byte[] cipher, byte[] key, int usage)

        throws KrbApErrException, KrbCryptoException{

        byte[] ivec = new byte[keySize()];

        return decrypt(cipher, key, ivec, usage);

    }

    /**

     * Decrypts the data using DES in CBC mode.

     * @param cipher the input buffer.

     * @param key the key to decrypt the data.

     * @param ivec initialization vector.

     *

     * @modified by Yanni Zhang, Dec 6 99.

     */

    public byte[] decrypt(byte[] cipher, byte[] key, byte[] ivec, int usage)

        throws KrbApErrException, KrbCryptoException {

        /*

         * To meet export control requirements, double check that the

         * key being used is no longer than 64 bits.

         *

         * Note that from a protocol point of view, an

         * algorithm that is not DES will be rejected before this

         * point. Also, a DES key that is not 64 bits will be

         * rejected by a good JCE provider.

         */

        if (key.length > 8)

            throw new KrbCryptoException("Invalid DES Key!");

        byte[] data = new byte[cipher.length];

        Des.cbc_encrypt(cipher, data, key, ivec, false);

        if (!isChecksumValid(data))

            throw new KrbApErrException(Krb5.KRB_AP_ERR_BAD_INTEGRITY);

        return data;

    }

    private void copyChecksumField(byte[] data, byte[] cksum) {

        for (int i = 0; i < checksumSize();  i++)

            data[startOfChecksum() + i] = cksum[i];

    }

    private byte[] checksumField(byte[] data) {

        byte[] result = new byte[checksumSize()];

        for (int i = 0; i < checksumSize(); i++)

        result[i] = data[startOfChecksum() + i];

        return result;

    }

    private void resetChecksumField(byte[] data) {

        for (int i = startOfChecksum(); i < startOfChecksum() +

                 checksumSize();  i++)

            data[i] = 0;

    }

    /*

        // Not used.

    public void setChecksum(byte[] data, int size) throws KrbCryptoException{

        resetChecksumField(data);

        byte[] cksum = calculateChecksum(data, size);

        copyChecksumField(data, cksum);

    }

*/

    private byte[] generateChecksum(byte[] data) throws KrbCryptoException{

        byte[] cksum1 = checksumField(data);

        resetChecksumField(data);

        byte[] cksum2 = calculateChecksum(data, data.length);

        copyChecksumField(data, cksum1);

        return cksum2;

    }

    private boolean isChecksumEqual(byte[] cksum1, byte[] cksum2) {

        if (cksum1 == cksum2)

            return true;

        if ((cksum1 == null && cksum2 != null) ||

            (cksum1 != null && cksum2 == null))

            return false;

        if (cksum1.length != cksum2.length)

            return false;

        for (int i = 0; i < cksum1.length; i++)

            if (cksum1[i] != cksum2[i])

                return false;

        return true;

    }

    protected boolean isChecksumValid(byte[] data) throws KrbCryptoException {

        byte[] cksum1 = checksumField(data);

        byte[] cksum2 = generateChecksum(data);

        return isChecksumEqual(cksum1, cksum2);

    }

}