Validates a password using a hash. - Java Security

Java examples for Security:Password

  1. HOME
  2. Java
  3. Security
  4. Password

Description

Validates a password using a hash.

Demo Code

/* //from  w ww  . j ava 2s. c o m
 * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm).
 * Copyright (c) 2013, Taylor Hornby
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, 
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation 
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 */
//package com.java2s;

import javax.crypto.spec.PBEKeySpec;
import javax.crypto.SecretKeyFactory;

import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;

public class Main {
    public static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA1";
    public static final int ITERATION_INDEX = 0;
    public static final int SALT_INDEX = 1;
    public static final int PBKDF2_INDEX = 2;

    /**
     * Validates a password using a hash.
     *
     * @param   password        the password to check
     * @param   correctHash     the hash of the valid password
     * @return                  true if the password is correct, false if not
     */
    public static boolean validatePassword(String password,
            String correctHash) throws NoSuchAlgorithmException,
            InvalidKeySpecException {
        return validatePassword(password.toCharArray(), correctHash);
    }

    /**
     * Validates a password using a hash.
     *
     * @param   password        the password to check
     * @param   correctHash     the hash of the valid password
     * @return                  true if the password is correct, false if not
     */
    public static boolean validatePassword(char[] password,
            String correctHash) throws NoSuchAlgorithmException,
            InvalidKeySpecException {
        // Decode the hash into its parameters
        String[] params = correctHash.split(":");
        int iterations = Integer.parseInt(params[ITERATION_INDEX]);
        byte[] salt = fromHex(params[SALT_INDEX]);
        byte[] hash = fromHex(params[PBKDF2_INDEX]);
        // Compute the hash of the provided password, using the same salt, 
        // iteration count, and hash length
        byte[] testHash = pbkdf2(password, salt, iterations, hash.length);
        // Compare the hashes in constant time. The password is correct if
        // both hashes match.
        return slowEquals(hash, testHash);
    }

    /**
     * Converts a string of hexadecimal characters into a byte array.
     *
     * @param   hex         the hex string
     * @return              the hex string decoded into a byte array
     */
    private static byte[] fromHex(String hex) {
        byte[] binary = new byte[hex.length() / 2];
        for (int i = 0; i < binary.length; i++) {
            binary[i] = (byte) Integer.parseInt(
                    hex.substring(2 * i, 2 * i + 2), 16);
        }
        return binary;
    }

    /**
     *  Computes the PBKDF2 hash of a password.
     *
     * @param   password    the password to hash.
     * @param   salt        the salt
     * @param   iterations  the iteration count (slowness factor)
     * @param   bytes       the length of the hash to compute in bytes
     * @return              the PBDKF2 hash of the password
     */
    private static byte[] pbkdf2(char[] password, byte[] salt,
            int iterations, int bytes) throws NoSuchAlgorithmException,
            InvalidKeySpecException {
        PBEKeySpec spec = new PBEKeySpec(password, salt, iterations,
                bytes * 8);
        SecretKeyFactory skf = SecretKeyFactory
                .getInstance(PBKDF2_ALGORITHM);
        return skf.generateSecret(spec).getEncoded();
    }

    /**
     * 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.
     * 
     * @param   a       the first byte array
     * @param   b       the second byte array 
     * @return          true if both byte arrays are the same, false if not
     */
    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;
    }
}

Related Tutorials