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	/*
	* Copyright (c) 2005, 2008, 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.
	*/

	package sun.security.krb5.internal.crypto.dk;

	import java.security.*;
	import javax.crypto.*;
	import javax.crypto.spec.*;
	import java.util.*;
	import sun.security.krb5.EncryptedData;
	import sun.security.krb5.KrbCryptoException;
	import sun.security.krb5.Confounder;
	import sun.security.krb5.internal.crypto.KeyUsage;

	/**
	* Support for ArcFour in Kerberos
	* as defined in RFC 4757.
	* http://www.ietf.org/rfc/rfc4757.txt
	*
	* @author Seema Malkani
	*/

	public class ArcFourCrypto extends DkCrypto {

	private static final boolean debug = false;

	private static final int confounderSize = 8;
	private static final byte[] ZERO_IV = new byte[] {0, 0, 0, 0, 0, 0, 0, 0};
	private static final int hashSize = 16;
	private final int keyLength;

	public ArcFourCrypto(int length) {
	keyLength = length;
	}

	protected int getKeySeedLength() {
	return keyLength; // bits; RC4 key material
	}

	protected byte[] randomToKey(byte[] in) {
	// simple identity operation
	return in;
	}

	public byte[] stringToKey(char[] passwd)
	throws GeneralSecurityException {
	return stringToKey(passwd, null);
	}

	/*
	* String2Key(Password)
	* K = MD4(UNICODE(password))
	*/
	private byte[] stringToKey(char[] secret, byte[] opaque)
	throws GeneralSecurityException {

	if (opaque != null && opaque.length > 0) {
	throw new RuntimeException("Invalid parameter to stringToKey");
	}

	byte[] passwd = null;
	byte[] digest = null;
	try {
	// convert ascii to unicode
	passwd = charToUtf16(secret);

	// provider for MD4
	MessageDigest md = sun.security.provider.MD4.getInstance();
	md.update(passwd);
	digest = md.digest();
	} catch (Exception e) {
	return null;
	} finally {
	if (passwd != null) {
	Arrays.fill(passwd, (byte)0);
	}
	}

	return digest;
	}

	protected Cipher getCipher(byte[] key, byte[] ivec, int mode)
	throws GeneralSecurityException {

	// IV
	if (ivec == null) {
	ivec = ZERO_IV;
	}
	SecretKeySpec secretKey = new SecretKeySpec(key, "ARCFOUR");
	Cipher cipher = Cipher.getInstance("ARCFOUR");
	IvParameterSpec encIv = new IvParameterSpec(ivec, 0, ivec.length);
	cipher.init(mode, secretKey, encIv);
	return cipher;
	}

	public int getChecksumLength() {
	return hashSize; // bytes
	}

	/**
	* Get the HMAC-MD5
	*/
	protected byte[] getHmac(byte[] key, byte[] msg)
	throws GeneralSecurityException {

	SecretKey keyKi = new SecretKeySpec(key, "HmacMD5");
	Mac m = Mac.getInstance("HmacMD5");
	m.init(keyKi);

	// generate hash
	byte[] hash = m.doFinal(msg);
	return hash;
	}

	/**
	* Calculate the checksum
	*/
	public byte[] calculateChecksum(byte[] baseKey, int usage, byte[] input,
	int start, int len) throws GeneralSecurityException {

	if (debug) {
	System.out.println("ARCFOUR: calculateChecksum with usage = " +
	usage);
	}

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}

	byte[] Ksign = null;
	// Derive signing key from session key
	try {
	byte[] ss = "signaturekey".getBytes();
	// need to append end-of-string 00
	byte[] new_ss = new byte[ss.length+1];
	System.arraycopy(ss, 0, new_ss, 0, ss.length);
	Ksign = getHmac(baseKey, new_ss);
	} catch (Exception e) {
	GeneralSecurityException gse =
	new GeneralSecurityException("Calculate Checkum Failed!");
	gse.initCause(e);
	throw gse;
	}

	// get the salt using key usage
	byte[] salt = getSalt(usage);

	// Generate checksum of message
	MessageDigest messageDigest = null;
	try {
	messageDigest = MessageDigest.getInstance("MD5");
	} catch (NoSuchAlgorithmException e) {
	GeneralSecurityException gse =
	new GeneralSecurityException("Calculate Checkum Failed!");
	gse.initCause(e);
	throw gse;
	}
	messageDigest.update(salt);
	messageDigest.update(input, start, len);
	byte[] md5tmp = messageDigest.digest();

	// Generate checksum
	byte[] hmac = getHmac(Ksign, md5tmp);
	if (debug) {
	traceOutput("hmac", hmac, 0, hmac.length);
	}
	if (hmac.length == getChecksumLength()) {
	return hmac;
	} else if (hmac.length > getChecksumLength()) {
	byte[] buf = new byte[getChecksumLength()];
	System.arraycopy(hmac, 0, buf, 0, buf.length);
	return buf;
	} else {
	throw new GeneralSecurityException("checksum size too short: " +
	hmac.length + "; expecting : " + getChecksumLength());
	}
	}

	/**
	* Performs encryption of Sequence Number using derived key.
	*/
	public byte[] encryptSeq(byte[] baseKey, int usage,
	byte[] checksum, byte[] plaintext, int start, int len)
	throws GeneralSecurityException, KrbCryptoException {

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}
	// derive encryption for sequence number
	byte[] salt = new byte[4];
	byte[] kSeq = getHmac(baseKey, salt);

	// derive new encryption key salted with sequence number
	kSeq = getHmac(kSeq, checksum);

	Cipher cipher = Cipher.getInstance("ARCFOUR");
	SecretKeySpec secretKey = new SecretKeySpec(kSeq, "ARCFOUR");
	cipher.init(Cipher.ENCRYPT_MODE, secretKey);
	byte[] output = cipher.doFinal(plaintext, start, len);

	return output;
	}

	/**
	* Performs decryption of Sequence Number using derived key.
	*/
	public byte[] decryptSeq(byte[] baseKey, int usage,
	byte[] checksum, byte[] ciphertext, int start, int len)
	throws GeneralSecurityException, KrbCryptoException {

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}

	// derive decryption for sequence number
	byte[] salt = new byte[4];
	byte[] kSeq = getHmac(baseKey, salt);

	// derive new encryption key salted with sequence number
	kSeq = getHmac(kSeq, checksum);

	Cipher cipher = Cipher.getInstance("ARCFOUR");
	SecretKeySpec secretKey = new SecretKeySpec(kSeq, "ARCFOUR");
	cipher.init(Cipher.DECRYPT_MODE, secretKey);
	byte[] output = cipher.doFinal(ciphertext, start, len);

	return output;
	}

	/**
	* Performs encryption using derived key; adds confounder.
	*/
	public byte[] encrypt(byte[] baseKey, int usage,
	byte[] ivec, byte[] new_ivec, byte[] plaintext, int start, int len)
	throws GeneralSecurityException, KrbCryptoException {

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}

	if (debug) {
	System.out.println("ArcFour: ENCRYPT with key usage = " + usage);
	}

	// get the confounder
	byte[] confounder = Confounder.bytes(confounderSize);

	// add confounder to the plaintext for encryption
	int plainSize = roundup(confounder.length + len, 1);
	byte[] toBeEncrypted = new byte[plainSize];
	System.arraycopy(confounder, 0, toBeEncrypted, 0, confounder.length);
	System.arraycopy(plaintext, start, toBeEncrypted,
	confounder.length, len);

	/* begin the encryption, compute K1 */
	byte[] k1 = new byte[baseKey.length];
	System.arraycopy(baseKey, 0, k1, 0, baseKey.length);

	// get the salt using key usage
	byte[] salt = getSalt(usage);

	// compute K2 using K1
	byte[] k2 = getHmac(k1, salt);

	// generate checksum using K2
	byte[] checksum = getHmac(k2, toBeEncrypted);

	// compute K3 using K2 and checksum
	byte[] k3 = getHmac(k2, checksum);

	Cipher cipher = Cipher.getInstance("ARCFOUR");
	SecretKeySpec secretKey = new SecretKeySpec(k3, "ARCFOUR");
	cipher.init(Cipher.ENCRYPT_MODE, secretKey);
	byte[] output = cipher.doFinal(toBeEncrypted, 0, toBeEncrypted.length);

	// encryptedData + HMAC
	byte[] result = new byte[hashSize + output.length];
	System.arraycopy(checksum, 0, result, 0, hashSize);
	System.arraycopy(output, 0, result, hashSize, output.length);

	return result;
	}

	/**
	* Performs encryption using derived key; does not add confounder.
	*/
	public byte[] encryptRaw(byte[] baseKey, int usage,
	byte[] seqNum, byte[] plaintext, int start, int len)
	throws GeneralSecurityException, KrbCryptoException {

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}

	if (debug) {
	System.out.println("\nARCFOUR: encryptRaw with usage = " + usage);
	}

	// Derive encryption key for data
	// Key derivation salt = 0
	byte[] klocal = new byte[baseKey.length];
	for (int i = 0; i <= 15; i++) {
	klocal[i] = (byte) (baseKey[i] ^ 0xF0);
	}
	byte[] salt = new byte[4];
	byte[] kcrypt = getHmac(klocal, salt);

	// Note: When using this RC4 based encryption type, the sequence number
	// is always sent in big-endian rather than little-endian order.

	// new encryption key salted with sequence number
	kcrypt = getHmac(kcrypt, seqNum);

	Cipher cipher = Cipher.getInstance("ARCFOUR");
	SecretKeySpec secretKey = new SecretKeySpec(kcrypt, "ARCFOUR");
	cipher.init(Cipher.ENCRYPT_MODE, secretKey);
	byte[] output = cipher.doFinal(plaintext, start, len);

	return output;
	}

	/**
	* @param baseKey key from which keys are to be derived using usage
	* @param ciphertext E(Ke, conf \| plaintext \| padding, ivec) \| H1[1..h]
	*/
	public byte[] decrypt(byte[] baseKey, int usage, byte[] ivec,
	byte[] ciphertext, int start, int len)
	throws GeneralSecurityException {

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}
	if (debug) {
	System.out.println("\nARCFOUR: DECRYPT using key usage = " + usage);
	}

	// compute K1
	byte[] k1 = new byte[baseKey.length];
	System.arraycopy(baseKey, 0, k1, 0, baseKey.length);

	// get the salt using key usage
	byte[] salt = getSalt(usage);

	// compute K2 using K1
	byte[] k2 = getHmac(k1, salt);

	// compute K3 using K2 and checksum
	byte[] checksum = new byte[hashSize];
	System.arraycopy(ciphertext, start, checksum, 0, hashSize);
	byte[] k3 = getHmac(k2, checksum);

	// Decrypt [confounder \| plaintext ] (without checksum)
	Cipher cipher = Cipher.getInstance("ARCFOUR");
	SecretKeySpec secretKey = new SecretKeySpec(k3, "ARCFOUR");
	cipher.init(Cipher.DECRYPT_MODE, secretKey);
	byte[] plaintext = cipher.doFinal(ciphertext, start+hashSize,
	len-hashSize);

	// Verify checksum
	byte[] calculatedHmac = getHmac(k2, plaintext);
	if (debug) {
	traceOutput("calculated Hmac", calculatedHmac, 0,
	calculatedHmac.length);
	traceOutput("message Hmac", ciphertext, 0,
	hashSize);
	}
	boolean cksumFailed = false;
	if (calculatedHmac.length >= hashSize) {
	for (int i = 0; i < hashSize; i++) {
	if (calculatedHmac[i] != ciphertext[i]) {
	cksumFailed = true;
	if (debug) {
	System.err.println("Checksum failed !");
	}
	break;
	}
	}
	}
	if (cksumFailed) {
	throw new GeneralSecurityException("Checksum failed");
	}

	// Get rid of confounder
	// [ confounder \| plaintext ]
	byte[] output = new byte[plaintext.length - confounderSize];
	System.arraycopy(plaintext, confounderSize, output, 0, output.length);

	return output;
	}

	/**
	* Decrypts data using specified key and initial vector.
	* @param baseKey encryption key to use
	* @param ciphertext encrypted data to be decrypted
	* @param usage ignored
	*/
	public byte[] decryptRaw(byte[] baseKey, int usage, byte[] ivec,
	byte[] ciphertext, int start, int len, byte[] seqNum)
	throws GeneralSecurityException {

	if (!KeyUsage.isValid(usage)) {
	throw new GeneralSecurityException("Invalid key usage number: "
	+ usage);
	}
	if (debug) {
	System.out.println("\nARCFOUR: decryptRaw with usage = " + usage);
	}

	// Derive encryption key for data
	// Key derivation salt = 0
	byte[] klocal = new byte[baseKey.length];
	for (int i = 0; i <= 15; i++) {
	klocal[i] = (byte) (baseKey[i] ^ 0xF0);
	}
	byte[] salt = new byte[4];
	byte[] kcrypt = getHmac(klocal, salt);

	// need only first 4 bytes of sequence number
	byte[] sequenceNum = new byte[4];
	System.arraycopy(seqNum, 0, sequenceNum, 0, sequenceNum.length);

	// new encryption key salted with sequence number
	kcrypt = getHmac(kcrypt, sequenceNum);

	Cipher cipher = Cipher.getInstance("ARCFOUR");
	SecretKeySpec secretKey = new SecretKeySpec(kcrypt, "ARCFOUR");
	cipher.init(Cipher.DECRYPT_MODE, secretKey);
	byte[] output = cipher.doFinal(ciphertext, start, len);

	return output;
	}

	// get the salt using key usage
	private byte[] getSalt(int usage) {
	int ms_usage = arcfour_translate_usage(usage);
	byte[] salt = new byte[4];
	salt[0] = (byte)(ms_usage & 0xff);
	salt[1] = (byte)((ms_usage >> 8) & 0xff);
	salt[2] = (byte)((ms_usage >> 16) & 0xff);
	salt[3] = (byte)((ms_usage >> 24) & 0xff);
	return salt;
	}

	// Key usage translation for MS
	private int arcfour_translate_usage(int usage) {
	switch (usage) {
	case 3: return 8;
	case 9: return 8;
	case 23: return 13;
	default: return usage;
	}
	}

	}

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