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* 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.
*
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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;
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;
}
}
}