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/*
* Copyright 2015 Anton Tananaev (anton@traccar.org)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.traccar.helper;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.xml.bind.DatatypeConverter;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
public final class Hashing {
public static final int ITERATIONS = 1000;
public static final int SALT_SIZE = 24;
public static final int HASH_SIZE = 24;
private static SecretKeyFactory factory;
static {
try {
factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
} catch (NoSuchAlgorithmException e) {
}
}
public static class HashingResult {
private final String hash;
private final String salt;
public HashingResult(String hash, String salt) {
this.hash = hash;
this.salt = salt;
}
public String getHash() {
return hash;
}
public String getSalt() {
return salt;
}
}
private Hashing() {
}
private static byte[] function(char[] password, byte[] salt) {
try {
PBEKeySpec spec = new PBEKeySpec(password, salt, ITERATIONS, HASH_SIZE * Byte.SIZE);
return factory.generateSecret(spec).getEncoded();
} catch (InvalidKeySpecException e) {
throw new SecurityException(e);
}
}
private static final SecureRandom RANDOM = new SecureRandom();
public static HashingResult createHash(String password) {
byte[] salt = new byte[SALT_SIZE];
RANDOM.nextBytes(salt);
byte[] hash = function(password.toCharArray(), salt);
return new HashingResult(
DatatypeConverter.printHexBinary(hash),
DatatypeConverter.printHexBinary(salt));
}
public static boolean validatePassword(String password, String hashHex, String saltHex) {
byte[] hash = DatatypeConverter.parseHexBinary(hashHex);
byte[] salt = DatatypeConverter.parseHexBinary(saltHex);
return slowEquals(hash, function(password.toCharArray(), salt));
}
/**
* Compares two byte arrays in length-constant time. This comparison method
* is used so that password hashes cannot be extracted from an on-line
* system using a timing attack and then attacked off-line.
*/
private static boolean slowEquals(byte[] a, byte[] b) {
int diff = a.length ^ b.length;
for (int i = 0; i < a.length && i < b.length; i++) {
diff |= a[i] ^ b[i];
}
return diff == 0;
}
}
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