/*

 * Copyright (c) 2000, 2019, 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;

import java.util.Arrays;

import sun.security.util.*;

import sun.security.krb5.internal.*;

import sun.security.krb5.internal.crypto.*;

import java.io.IOException;

import java.math.BigInteger;

/**

 * This class encapsulates the concept of a Kerberos checksum.

 */

public class Checksum {

    private int cksumType;

    private byte[] checksum;

    // ----------------------------------------------+-------------+-----------

    //                      Checksum type            |sumtype      |checksum

    //                                               |value        | size

    // ----------------------------------------------+-------------+-----------

    public static final int CKSUMTYPE_NULL          = 0;               // 0

    public static final int CKSUMTYPE_CRC32         = 1;               // 4

    public static final int CKSUMTYPE_RSA_MD4       = 2;               // 16

    public static final int CKSUMTYPE_RSA_MD4_DES   = 3;               // 24

    public static final int CKSUMTYPE_DES_MAC       = 4;               // 16

    public static final int CKSUMTYPE_DES_MAC_K     = 5;               // 8

    public static final int CKSUMTYPE_RSA_MD4_DES_K = 6;               // 16

    public static final int CKSUMTYPE_RSA_MD5       = 7;               // 16

    public static final int CKSUMTYPE_RSA_MD5_DES   = 8;               // 24

     // draft-ietf-krb-wg-crypto-07.txt

    public static final int CKSUMTYPE_HMAC_SHA1_DES3_KD = 12;          // 20

    // draft-raeburn-krb-rijndael-krb-07.txt

    public static final int CKSUMTYPE_HMAC_SHA1_96_AES128 = 15;        // 96

    public static final int CKSUMTYPE_HMAC_SHA1_96_AES256 = 16;        // 96

    // rfc8009

    public static final int CKSUMTYPE_HMAC_SHA256_128_AES128 = 19;        // 96

    public static final int CKSUMTYPE_HMAC_SHA384_192_AES256 = 20;        // 96

    // draft-brezak-win2k-krb-rc4-hmac-04.txt

    public static final int CKSUMTYPE_HMAC_MD5_ARCFOUR = -138;

    static int CKSUMTYPE_DEFAULT;

    static int SAFECKSUMTYPE_DEFAULT;

    private static boolean DEBUG = Krb5.DEBUG;

    static {

        initStatic();

    }

    public static void initStatic() {

        String temp = null;

        Config cfg = null;

        try {

            cfg = Config.getInstance();

            temp = cfg.get("libdefaults", "default_checksum");

            if (temp != null)

                {

                    CKSUMTYPE_DEFAULT = Config.getType(temp);

                } else {

                    /*

                     * If the default checksum is not

                     * specified in the configuration we

                     * set it to RSA_MD5. We follow the MIT and

                     * SEAM implementation.

                     */

                    CKSUMTYPE_DEFAULT = CKSUMTYPE_RSA_MD5;

                }

        } catch (Exception exc) {

            if (DEBUG) {

                System.out.println("Exception in getting default checksum "+

                                   "value from the configuration " +

                                   "Setting default checksum to be RSA-MD5");

                exc.printStackTrace();

            }

            CKSUMTYPE_DEFAULT = CKSUMTYPE_RSA_MD5;

        }

        try {

            temp = cfg.get("libdefaults", "safe_checksum_type");

            if (temp != null)

                {

                    SAFECKSUMTYPE_DEFAULT = Config.getType(temp);

                } else {

                    SAFECKSUMTYPE_DEFAULT = CKSUMTYPE_RSA_MD5_DES;

                }

        } catch (Exception exc) {

            if (DEBUG) {

                System.out.println("Exception in getting safe default " +

                                   "checksum value " +

                                   "from the configuration Setting  " +

                                   "safe default checksum to be RSA-MD5");

                exc.printStackTrace();

            }

            SAFECKSUMTYPE_DEFAULT = CKSUMTYPE_RSA_MD5_DES;

        }

    }

    /**

     * Constructs a new Checksum using the raw data and type.

     * @param data the byte array of checksum.

     * @param new_cksumType the type of checksum.

     *

     */

         // used in InitialToken

    public Checksum(byte[] data, int new_cksumType) {

        cksumType = new_cksumType;

        checksum = data;

    }

    /**

     * Constructs a new Checksum by calculating the checksum over the data

     * using specified checksum type.

     * @param new_cksumType the type of checksum.

     * @param data the data that needs to be performed a checksum calculation on.

     */

    public Checksum(int new_cksumType, byte[] data)

        throws KdcErrException, KrbCryptoException {

        cksumType = new_cksumType;

        CksumType cksumEngine = CksumType.getInstance(cksumType);

        if (!cksumEngine.isSafe()) {

            checksum = cksumEngine.calculateChecksum(data, data.length);

        } else {

            throw new KdcErrException(Krb5.KRB_AP_ERR_INAPP_CKSUM);

        }

    }

    /**

     * Constructs a new Checksum by calculating the keyed checksum

     * over the data using specified checksum type.

     * @param new_cksumType the type of checksum.

     * @param data the data that needs to be performed a checksum calculation on.

     */

         // KrbSafe, KrbTgsReq

    public Checksum(int new_cksumType, byte[] data,

                        EncryptionKey key, int usage)

        throws KdcErrException, KrbApErrException, KrbCryptoException {

        cksumType = new_cksumType;

        CksumType cksumEngine = CksumType.getInstance(cksumType);

        if (!cksumEngine.isSafe())

            throw new KrbApErrException(Krb5.KRB_AP_ERR_INAPP_CKSUM);

        checksum =

            cksumEngine.calculateKeyedChecksum(data,

                data.length,

                key.getBytes(),

                usage);

    }

    /**

     * Verifies the keyed checksum over the data passed in.

     */

    public boolean verifyKeyedChecksum(byte[] data, EncryptionKey key,

                                        int usage)

        throws KdcErrException, KrbApErrException, KrbCryptoException {

        CksumType cksumEngine = CksumType.getInstance(cksumType);

        if (!cksumEngine.isSafe())

            throw new KrbApErrException(Krb5.KRB_AP_ERR_INAPP_CKSUM);

        return cksumEngine.verifyKeyedChecksum(data,

                                               data.length,

                                               key.getBytes(),

                                               checksum,

            usage);

    }

    /*

    public Checksum(byte[] data) throws KdcErrException, KrbCryptoException {

        this(Checksum.CKSUMTYPE_DEFAULT, data);

    }

    */

    boolean isEqual(Checksum cksum) throws KdcErrException {

        if (cksumType != cksum.cksumType)

            return false;

        CksumType cksumEngine = CksumType.getInstance(cksumType);

        return CksumType.isChecksumEqual(checksum, cksum.checksum);

    }

    /**

     * Constructs an instance of Checksum from an ASN.1 encoded representation.

     * @param encoding a single DER-encoded value.

     * @exception Asn1Exception if an error occurs while decoding an ASN1

     * encoded data.

     * @exception IOException if an I/O error occurs while reading encoded data.

     *

     */

    public Checksum(DerValue encoding) throws Asn1Exception, IOException {

        DerValue der;

        if (encoding.getTag() != DerValue.tag_Sequence) {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        der = encoding.getData().getDerValue();

        if ((der.getTag() & (byte)0x1F) == (byte)0x00) {

            cksumType = der.getData().getBigInteger().intValue();

        }

        else

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        der = encoding.getData().getDerValue();

        if ((der.getTag() & (byte)0x1F) == (byte)0x01) {

            checksum = der.getData().getOctetString();

        }

        else

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        if (encoding.getData().available() > 0) {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

    }

    /**

     * Encodes a Checksum object.

     * <pre>{@code

     * Checksum    ::= SEQUENCE {

     *         cksumtype   [0] Int32,

     *         checksum    [1] OCTET STRING

     * }

     * }</pre>

     *

     * <p>

     * This definition reflects the Network Working Group RFC 4120

     * specification available at

     * <a href="http://www.ietf.org/rfc/rfc4120.txt">

     * http://www.ietf.org/rfc/rfc4120.txt</a>.

     * @return byte array of enocded Checksum.

     * @exception Asn1Exception if an error occurs while decoding an

     * ASN1 encoded data.

     * @exception IOException if an I/O error occurs while reading

     * encoded data.

     *

     */

    public byte[] asn1Encode() throws Asn1Exception, IOException {

        DerOutputStream bytes = new DerOutputStream();

        DerOutputStream temp = new DerOutputStream();

        temp.putInteger(BigInteger.valueOf(cksumType));

        bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT,

                                       true, (byte)0x00), temp);

        temp = new DerOutputStream();

        temp.putOctetString(checksum);

        bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT,

                                       true, (byte)0x01), temp);

        temp = new DerOutputStream();

        temp.write(DerValue.tag_Sequence, bytes);

        return temp.toByteArray();

    }

    /**

     * Parse (unmarshal) a checksum object from a DER input stream.  This form

     * parsing might be used when expanding a value which is part of

     * a constructed sequence and uses explicitly tagged type.

     *

     * @exception Asn1Exception if an error occurs while decoding an

     * ASN1 encoded data.

     * @exception IOException if an I/O error occurs while reading

     * encoded data.

     * @param data the Der input stream value, which contains one or more

     * marshaled value.

     * @param explicitTag tag number.

     * @param optional indicates if this data field is optional

     * @return an instance of Checksum.

     *

     */

    public static Checksum parse(DerInputStream data,

                                 byte explicitTag, boolean optional)

        throws Asn1Exception, IOException {

        if ((optional) &&

            (((byte)data.peekByte() & (byte)0x1F) != explicitTag)) {

            return null;

        }

        DerValue der = data.getDerValue();

        if (explicitTag != (der.getTag() & (byte)0x1F))  {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        } else {

            DerValue subDer = der.getData().getDerValue();

            return new Checksum(subDer);

        }

    }

    /**

     * Returns the raw bytes of the checksum, not in ASN.1 encoded form.

     */

    public final byte[] getBytes() {

        return checksum;

    }

    public final int getType() {

        return cksumType;

    }

    @Override public boolean equals(Object obj) {

        if (this == obj) {

            return true;

        }

        if (!(obj instanceof Checksum)) {

            return false;

        }

        try {

            return isEqual((Checksum)obj);

        } catch (KdcErrException kee) {

            return false;

        }

    }

    @Override public int hashCode() {

        int result = 17;

        result = 37 * result + cksumType;

        if (checksum != null) {

            result = 37 * result + Arrays.hashCode(checksum);

        }

        return result;

    }

}