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* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
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*/
package org.picketlink.idm.credential.util;
import java.math.BigInteger;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
/**
* TOTP: Time-based One-time Password Algorithm Based on http://tools.ietf.org/html/draft-mraihi-totp-timebased-06
*
* @author anil saldhana
* @since Sep 20, 2010
*/
public class TimeBasedOTP {
public static final String HMAC_SHA1 = "HmacSHA1";
public static final String HMAC_SHA256 = "HmacSHA256";
public static final String HMAC_SHA512 = "HmacSHA512";
public static final String DEFAULT_ALGORITHM = HMAC_SHA1;
public static final int DEFAULT_NUMBER_DIGITS = 6;
public static final int DEFAULT_INTERVAL_SECONDS = 30;
public static final int DEFAULT_DELAY_WINDOW = 1;
// 0 1 2 3 4 5 6 7 8
private static final int[] DIGITS_POWER = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000};
private Clock clock;
private final String algorithm;
private final int numberDigits;
private final int delayWindow;
public TimeBasedOTP() {
this(DEFAULT_ALGORITHM, DEFAULT_NUMBER_DIGITS, DEFAULT_INTERVAL_SECONDS, DEFAULT_DELAY_WINDOW);
}
/**
* @param algorithm the encryption algorithm
* @param numberDigits the number of digits for tokens
* @param timeIntervalInSeconds the number of seconds a token is valid
* @param delayWindow the number of previous intervals that should be used to validate tokens.
*/
public TimeBasedOTP(String algorithm, int numberDigits, int timeIntervalInSeconds, int delayWindow) {
this.algorithm = algorithm;
this.numberDigits = numberDigits;
this.clock = new Clock(timeIntervalInSeconds);
this.delayWindow = delayWindow;
}
/**
* <p>Generates a token.</p>
*
* @param secretKey the secret key to derive the token from.
*/
public String generate(String secretKey) {
long T = this.clock.getCurrentInterval();
String steps = Long.toHexString(T).toUpperCase();
// Just get a 16 digit string
while (steps.length() < 16)
steps = "0" + steps;
return generateTOTP(secretKey, steps, this.numberDigits, this.algorithm);
}
/**
* This method generates an TOTP value for the given set of parameters.
*
* @param key the shared secret, HEX encoded
* @param time a value that reflects a time
* @param returnDigits number of digits to return
* @param crypto the crypto function to use
* @return A numeric String in base 10 that includes {@link truncationDigits} digits
* @throws java.security.GeneralSecurityException
*
*/
public String generateTOTP(String key, String time, int returnDigits, String crypto) {
String result = null;
byte[] hash;
// Using the counter
// First 8 bytes are for the movingFactor
// Complaint with base RFC 4226 (HOTP)
while (time.length() < 16)
time = "0" + time;
// Get the HEX in a Byte[]
byte[] msg = hexStr2Bytes(time);
// Adding one byte to get the right conversion
// byte[] k = hexStr2Bytes(key);
byte[] k = key.getBytes();
hash = hmac_sha1(crypto, k, msg);
// put selected bytes into result int
int offset = hash[hash.length - 1] & 0xf;
int binary = ((hash[offset] & 0x7f) << 24) | ((hash[offset + 1] & 0xff) << 16) | ((hash[offset + 2] & 0xff) << 8)
| (hash[offset + 3] & 0xff);
int otp = binary % DIGITS_POWER[returnDigits];
result = Integer.toString(otp);
while (result.length() < returnDigits) {
result = "0" + result;
}
return result;
}
/**
* <p>Validates a token using a secret key.</p>
*
* @param token OTP string to validate
* @param secret Shared secret
* @return
*/
public boolean validate(String token, byte[] secret) {
long currentInterval = this.clock.getCurrentInterval();
for (int i = this.delayWindow; i >= 0; --i) {
String steps = Long.toHexString(currentInterval - i).toUpperCase();
// Just get a 16 digit string
while (steps.length() < 16)
steps = "0" + steps;
String candidate = generateTOTP(new String(secret), steps, this.numberDigits, this.algorithm);
if (candidate.equals(token)) {
return true;
}
}
return false;
}
public void setCalendar(Calendar calendar) {
this.clock.setCalendar(calendar);
}
/**
* This method uses the JCE to provide the crypto algorithm. HMAC computes a Hashed Message Authentication Code with the
* crypto hash algorithm as a parameter.
*
* @param crypto the crypto algorithm (HmacSHA1, HmacSHA256, HmacSHA512)
* @param keyBytes the bytes to use for the HMAC key
* @param text the message or text to be authenticated.
* @throws java.security.NoSuchAlgorithmException
*
* @throws java.security.InvalidKeyException
*
*/
private byte[] hmac_sha1(String crypto, byte[] keyBytes, byte[] text) {
byte[] value;
try {
Mac hmac = Mac.getInstance(crypto);
SecretKeySpec macKey = new SecretKeySpec(keyBytes, "RAW");
hmac.init(macKey);
value = hmac.doFinal(text);
} catch (Exception e) {
throw new RuntimeException(e);
}
return value;
}
/**
* This method converts HEX string to Byte[]
*
* @param hex the HEX string
* @return A byte array
*/
private byte[] hexStr2Bytes(String hex) {
// Adding one byte to get the right conversion
// values starting with "0" can be converted
byte[] bArray = new BigInteger("10" + hex, 16).toByteArray();
// Copy all the REAL bytes, not the "first"
byte[] ret = new byte[bArray.length - 1];
for (int i = 0; i < ret.length; i++)
ret[i] = bArray[i + 1];
return ret;
}
private class Clock {
private final int interval;
private Calendar calendar;
public Clock(int interval) {
this.interval = interval;
}
public long getCurrentInterval() {
Calendar currentCalendar = this.calendar;
if (currentCalendar == null) {
currentCalendar = GregorianCalendar.getInstance(TimeZone.getTimeZone("UTC"));
}
return (currentCalendar.getTimeInMillis() / 1000) / this.interval;
}
public void setCalendar(Calendar calendar) {
this.calendar = calendar;
}
}
}