Back to index...

	/*
	* 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.Checksum;
	import sun.security.krb5.Confounder;
	import sun.security.krb5.KrbCryptoException;
	import sun.security.krb5.internal.*;
	import javax.crypto.spec.DESKeySpec;
	import java.security.MessageDigest;
	import java.security.InvalidKeyException;

	public final class RsaMd5DesCksumType extends CksumType {

	public RsaMd5DesCksumType() {
	}

	public int confounderSize() {
	return 8;
	}

	public int cksumType() {
	return Checksum.CKSUMTYPE_RSA_MD5_DES;
	}

	public boolean isKeyed() {
	return true;
	}

	public int cksumSize() {
	return 24;
	}

	public int keyType() {
	return Krb5.KEYTYPE_DES;
	}

	public int keySize() {
	return 8;
	}

	/**
	* Calculates keyed checksum.
	* @param data the data used to generate the checksum.
	* @param size length of the data.
	* @param key the key used to encrypt the checksum.
	* @return keyed checksum.
	*
	* @modified by Yanni Zhang, 12/08/99.
	*/
	public byte[] calculateChecksum(byte[] data, int size, byte[] key,
	int usage) throws KrbCryptoException {
	//prepend confounder
	byte[] new_data = new byte[size + confounderSize()];
	byte[] conf = Confounder.bytes(confounderSize());
	System.arraycopy(conf, 0, new_data, 0, confounderSize());
	System.arraycopy(data, 0, new_data, confounderSize(), size);

	//calculate md5 cksum
	byte[] mdc_cksum = calculateRawChecksum(new_data, new_data.length);
	byte[] cksum = new byte[cksumSize()];
	System.arraycopy(conf, 0, cksum, 0, confounderSize());
	System.arraycopy(mdc_cksum, 0, cksum, confounderSize(),
	cksumSize() - confounderSize());

	//compute modified key
	byte[] new_key = new byte[keySize()];
	System.arraycopy(key, 0, new_key, 0, key.length);
	for (int i = 0; i < new_key.length; i++)
	new_key[i] = (byte)(new_key[i] ^ 0xf0);
	//check for weak keys
	try {
	if (DESKeySpec.isWeak(new_key, 0)) {
	new_key[7] = (byte)(new_key[7] ^ 0xF0);
	}
	} catch (InvalidKeyException ex) {
	// swallow, since it should never happen
	}
	byte[] ivec = new byte[new_key.length];

	//des-cbc encrypt
	byte[] enc_cksum = new byte[cksum.length];
	Des.cbc_encrypt(cksum, enc_cksum, new_key, ivec, true);
	return enc_cksum;
	}

	/**
	* Verifies keyed checksum.
	* @param data the data.
	* @param size the length of data.
	* @param key the key used to encrypt the checksum.
	* @param checksum the checksum.
	* @return true if verification is successful.
	*
	* @modified by Yanni Zhang, 12/08/99.
	*/
	public boolean verifyChecksum(byte[] data, int size,
	byte[] key, byte[] checksum, int usage) throws KrbCryptoException {
	//decrypt checksum
	byte[] cksum = decryptKeyedChecksum(checksum, key);

	//prepend confounder
	byte[] new_data = new byte[size + confounderSize()];
	System.arraycopy(cksum, 0, new_data, 0, confounderSize());
	System.arraycopy(data, 0, new_data, confounderSize(), size);

	byte[] new_cksum = calculateRawChecksum(new_data, new_data.length);
	//extract original cksum value
	byte[] orig_cksum = new byte[cksumSize() - confounderSize()];
	System.arraycopy(cksum, confounderSize(), orig_cksum, 0,
	cksumSize() - confounderSize());

	return isChecksumEqual(orig_cksum, new_cksum);
	}

	/**
	* Decrypts keyed checksum.
	* @param enc_cksum the buffer for encrypted checksum.
	* @param key the key.
	* @return the checksum.
	*
	* @modified by Yanni Zhang, 12/08/99.
	*/
	private byte[] decryptKeyedChecksum(byte[] enc_cksum, byte[] key) throws KrbCryptoException {
	//compute modified key
	byte[] new_key = new byte[keySize()];
	System.arraycopy(key, 0, new_key, 0, key.length);
	for (int i = 0; i < new_key.length; i++)
	new_key[i] = (byte)(new_key[i] ^ 0xf0);
	//check for weak keys
	try {
	if (DESKeySpec.isWeak(new_key, 0)) {
	new_key[7] = (byte)(new_key[7] ^ 0xF0);
	}
	} catch (InvalidKeyException ex) {
	// swallow, since it should never happen
	}
	byte[] ivec = new byte[new_key.length];

	byte[] cksum = new byte[enc_cksum.length];
	Des.cbc_encrypt(enc_cksum, cksum, new_key, ivec, false);
	return cksum;
	}

	/**
	* Calculates checksum using MD5.
	* @param data the data used to generate the checksum.
	* @param size length of the data.
	* @return the checksum.
	*
	* @modified by Yanni Zhang, 12/08/99.
	*/
	private byte[] calculateRawChecksum(byte[] data, int size) throws KrbCryptoException{
	MessageDigest md5;
	byte[] result = null;
	try {
	md5 = MessageDigest.getInstance("MD5");
	} catch (Exception e) {
	throw new KrbCryptoException("JCE provider may not be installed. " + e.getMessage());
	}
	try {
	md5.update(data);
	result = md5.digest();
	} catch (Exception e) {
	throw new KrbCryptoException(e.getMessage());
	}
	return result;
	}
	}

Back to index...