/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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.apache.commons.codec.digest;

 import java.security.MessageDigest;

 import java.util.Arrays;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 import org.apache.commons.codec.Charsets;

 /**

  * The libc crypt() "$1$" and Apache "$apr1$" MD5-based hash algorithm.

  * <p>

  * Based on the public domain ("beer-ware") C implementation from Poul-Henning Kamp which was found at: <a

  * href="http://www.freebsd.org/cgi/cvsweb.cgi/src/lib/libcrypt/crypt-md5.c?rev=1.1;content-type=text%2Fplain">

  * crypt-md5.c @ freebsd.org</a><br/>

  * <p>

  * Source:

  *

  * <pre>

  * $FreeBSD: src/lib/libcrypt/crypt-md5.c,v 1.1 1999/01/21 13:50:09 brandon Exp $

  * </pre>

  * <p>

  * Conversion to Kotlin and from there to Java in 2012.

  * <p>

  * The C style comments are from the original C code, the ones with "//" from the port.

  * <p>

  * This class is immutable and thread-safe.

  *

  * @version $Id: Md5Crypt.java 1429868 2013-01-07 16:08:05Z ggregory $

  * @since 1.7

  */

 public class Md5Crypt {

     /** The Identifier of the Apache variant. */

     static final String APR1_PREFIX = "$apr1$";

     /** The number of bytes of the final hash. */

     private static final int BLOCKSIZE = 16;

     /** The Identifier of this crypt() variant. */

     static final String MD5_PREFIX = "$1$";

     /** The number of rounds of the big loop. */

     private static final int ROUNDS = 1000;

     /**

      * See {@link #apr1Crypt(String, String)} for details.

      *

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught. *

      */

     public static String apr1Crypt(final byte[] keyBytes) {

         return apr1Crypt(keyBytes, APR1_PREFIX + B64.getRandomSalt(8));

     }

     /**

      * See {@link #apr1Crypt(String, String)} for details.

      *

      * @throws IllegalArgumentException

      *             if the salt does not match the allowed pattern

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught.

      */

     public static String apr1Crypt(final byte[] keyBytes, String salt) {

         // to make the md5Crypt regex happy

         if (salt != null && !salt.startsWith(APR1_PREFIX)) {

             salt = APR1_PREFIX + salt;

         }

         return Md5Crypt.md5Crypt(keyBytes, salt, APR1_PREFIX);

     }

     /**

      * See {@link #apr1Crypt(String, String)} for details.

      *

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught.

      */

     public static String apr1Crypt(final String keyBytes) {

         return apr1Crypt(keyBytes.getBytes(Charsets.UTF_8));

     }

     /**

      * Generates an Apache htpasswd compatible "$apr1$" MD5 based hash value.

      * <p>

      * The algorithm is identical to the crypt(3) "$1$" one but produces different outputs due to the different salt

      * prefix.

      *

      * @param keyBytes

      *            plaintext string that should be hashed.

      * @param salt

      *            salt string including the prefix and optionally garbage at the end. Will be generated randomly if

      *            null.

      * @return computed hash value

      * @throws IllegalArgumentException

      *             if the salt does not match the allowed pattern

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught.

      */

     public static String apr1Crypt(final String keyBytes, final String salt) {

         return apr1Crypt(keyBytes.getBytes(Charsets.UTF_8), salt);

     }

     /**

      * Generates a libc6 crypt() compatible "$1$" hash value.

      * <p>

      * See {@link Crypt#crypt(String, String)} for details.

      *

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught.

      */

     public static String md5Crypt(final byte[] keyBytes) {

         return md5Crypt(keyBytes, MD5_PREFIX + B64.getRandomSalt(8));

     }

     /**

      * Generates a libc crypt() compatible "$1$" MD5 based hash value.

      * <p>

      * See {@link Crypt#crypt(String, String)} for details.

      *

      * @param keyBytes

      *            plaintext string that should be hashed.

      * @param salt

      *            salt string including the prefix and optionally garbage at the end. Will be generated randomly if

      *            null.

      * @return computed hash value

      * @throws IllegalArgumentException

      *             if the salt does not match the allowed pattern

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught.

      */

     public static String md5Crypt(final byte[] keyBytes, final String salt) {

         return md5Crypt(keyBytes, salt, MD5_PREFIX);

     }

     /**

      * Generates a libc6 crypt() "$1$" or Apache htpasswd "$apr1$" hash value.

      * <p>

      * See {@link Crypt#crypt(String, String)} or {@link #apr1Crypt(String, String)} for details.

      *

      * @throws IllegalArgumentException

      *             if the salt does not match the allowed pattern

      * @throws RuntimeException

      *             when a {@link java.security.NoSuchAlgorithmException} is caught.

      */

     public static String md5Crypt(final byte[] keyBytes, final String salt, final String prefix) {

         final int keyLen = keyBytes.length;

         // Extract the real salt from the given string which can be a complete hash string.

         String saltString;

         if (salt == null) {

             saltString = B64.getRandomSalt(8);

         } else {

             final Pattern p = Pattern.compile("^" + prefix.replace("$", "\\$") + "([\\.\\/a-zA-Z0-9]{1,8}).*");

             final Matcher m = p.matcher(salt);

             if (m == null || !m.find()) {

                 throw new IllegalArgumentException("Invalid salt value: " + salt);

             }

             saltString = m.group(1);

         }

         final byte[] saltBytes = saltString.getBytes(Charsets.UTF_8);

         final MessageDigest ctx = DigestUtils.getMd5Digest();

         /*

          * The password first, since that is what is most unknown

          */

         ctx.update(keyBytes);

         /*

          * Then our magic string

          */

         ctx.update(prefix.getBytes(Charsets.UTF_8));

         /*

          * Then the raw salt

          */

         ctx.update(saltBytes);

         /*

          * Then just as many characters of the MD5(pw,salt,pw)

          */

         MessageDigest ctx1 = DigestUtils.getMd5Digest();

         ctx1.update(keyBytes);

         ctx1.update(saltBytes);

         ctx1.update(keyBytes);

         byte[] finalb = ctx1.digest();

         int ii = keyLen;

         while (ii > 0) {

             ctx.update(finalb, 0, ii > 16 ? 16 : ii);

             ii -= 16;

         }

         /*

          * Don't leave anything around in vm they could use.

          */

         Arrays.fill(finalb, (byte) 0);

         /*

          * Then something really weird...

          */

         ii = keyLen;

         final int j = 0;

         while (ii > 0) {

             if ((ii & 1) == 1) {

                 ctx.update(finalb[j]);

             } else {

                 ctx.update(keyBytes[j]);

             }

             ii >>= 1;

         }

         /*

          * Now make the output string

          */

         final StringBuilder passwd = new StringBuilder(prefix + saltString + "$");

         finalb = ctx.digest();

         /*

          * and now, just to make sure things don't run too fast On a 60 Mhz Pentium this takes 34 msec, so you would

          * need 30 seconds to build a 1000 entry dictionary...

          */

         for (int i = 0; i < ROUNDS; i++) {

             ctx1 = DigestUtils.getMd5Digest();

             if ((i & 1) != 0) {

                 ctx1.update(keyBytes);

             } else {

                 ctx1.update(finalb, 0, BLOCKSIZE);

             }

             if (i % 3 != 0) {

                 ctx1.update(saltBytes);

             }

             if (i % 7 != 0) {

                 ctx1.update(keyBytes);

             }

             if ((i & 1) != 0) {

                 ctx1.update(finalb, 0, BLOCKSIZE);

             } else {

                 ctx1.update(keyBytes);

             }

             finalb = ctx1.digest();

         }

         // The following was nearly identical to the Sha2Crypt code.

         // Again, the buflen is not really needed.

         // int buflen = MD5_PREFIX.length() - 1 + salt_string.length() + 1 + BLOCKSIZE + 1;

         B64.b64from24bit(finalb[0], finalb[6], finalb[12], 4, passwd);

         B64.b64from24bit(finalb[1], finalb[7], finalb[13], 4, passwd);

         B64.b64from24bit(finalb[2], finalb[8], finalb[14], 4, passwd);

         B64.b64from24bit(finalb[3], finalb[9], finalb[15], 4, passwd);

         B64.b64from24bit(finalb[4], finalb[10], finalb[5], 4, passwd);

         B64.b64from24bit((byte) 0, (byte) 0, finalb[11], 2, passwd);

         /*

          * Don't leave anything around in vm they could use.

          */

         // Is there a better way to do this with the JVM?

         ctx.reset();

         ctx1.reset();

         Arrays.fill(keyBytes, (byte) 0);

         Arrays.fill(saltBytes, (byte) 0);

         Arrays.fill(finalb, (byte) 0);

         return passwd.toString();

     }

 }