    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.codec.digest;
    018
    019import java.nio.charset.StandardCharsets;
    020import java.security.MessageDigest;
    021import java.security.NoSuchAlgorithmException;
    022import java.security.SecureRandom;
    023import java.util.Arrays;
    024import java.util.Random;
    025import java.util.concurrent.ThreadLocalRandom;
    026import java.util.regex.Matcher;
    027import java.util.regex.Pattern;
    028
    029/**
    030 * SHA2-based Unix crypt implementation.
    031 * <p>
    032 * Based on the C implementation released into the Public Domain by Ulrich Drepper &lt;drepper@redhat.com&gt;
    033 * http://www.akkadia.org/drepper/SHA-crypt.txt
    034 * <p>
    035 * Conversion to Kotlin and from there to Java in 2012 by Christian Hammers &lt;ch@lathspell.de&gt; and likewise put
    036 * into the Public Domain.
    037 * <p>
    038 * This class is immutable and thread-safe.
    039 *
    040 * @since 1.7
    041 */
    042public class Sha2Crypt {
    043
    044    /** Default number of rounds if not explicitly specified. */
    045    private static final int ROUNDS_DEFAULT = 5000;
    046
    047    /** Maximum number of rounds. */
    048    private static final int ROUNDS_MAX = 999999999;
    049
    050    /** Minimum number of rounds. */
    051    private static final int ROUNDS_MIN = 1000;
    052
    053    /** Prefix for optional rounds specification. */
    054    private static final String ROUNDS_PREFIX = "rounds=";
    055
    056    /** The number of bytes the final hash value will have (SHA-256 variant). */
    057    private static final int SHA256_BLOCKSIZE = 32;
    058
    059    /** The prefixes that can be used to identify this crypt() variant (SHA-256). */
    060    static final String SHA256_PREFIX = "$5$";
    061
    062    /** The number of bytes the final hash value will have (SHA-512 variant). */
    063    private static final int SHA512_BLOCKSIZE = 64;
    064
    065    /** The prefixes that can be used to identify this crypt() variant (SHA-512). */
    066    static final String SHA512_PREFIX = "$6$";
    067
    068    /** The pattern to match valid salt values. */
    069    private static final Pattern SALT_PATTERN = Pattern
    070            .compile("^\\$([56])\\$(rounds=(\\d+)\\$)?([\\.\\/a-zA-Z0-9]{1,16}).*");
    071
    072    /**
    073     * Generates a libc crypt() compatible "$5$" hash value with random salt.
    074     * <p>
    075     * See {@link Crypt#crypt(String, String)} for details.
    076     * </p>
    077     * <p>
    078     * A salt is generated for you using {@link ThreadLocalRandom}; for more secure salts consider using
    079     * {@link SecureRandom} to generate your own salts and calling {@link #sha256Crypt(byte[], String)}.
    080     * </p>
    081     *
    082     * @param keyBytes
    083     *            plaintext to hash
    084     * @return complete hash value
    085     * @throws IllegalArgumentException
    086     *             when a {@link java.security.NoSuchAlgorithmException} is caught.
    087     */
    088    public static String sha256Crypt(final byte[] keyBytes) {
    089        return sha256Crypt(keyBytes, null);
    090    }
    091
    092    /**
    093     * Generates a libc6 crypt() compatible "$5$" hash value.
    094     * <p>
    095     * See {@link Crypt#crypt(String, String)} for details.
    096     * </p>
    097     * @param keyBytes
    098     *            plaintext to hash
    099     * @param salt
    100     *            real salt value without prefix or "rounds=". The salt may be null, in which case a salt
    101     *            is generated for you using {@link SecureRandom}. If one does not want to use {@link SecureRandom},
    102     *            you can pass your own {@link Random} in {@link #sha256Crypt(byte[], String, Random)}.
    103     * @return complete hash value including salt
    104     * @throws IllegalArgumentException
    105     *             if the salt does not match the allowed pattern
    106     * @throws IllegalArgumentException
    107     *             when a {@link java.security.NoSuchAlgorithmException} is caught.
    108     */
    109    public static String sha256Crypt(final byte[] keyBytes, String salt) {
    110        if (salt == null) {
    111            salt = SHA256_PREFIX + B64.getRandomSalt(8);
    112        }
    113        return sha2Crypt(keyBytes, salt, SHA256_PREFIX, SHA256_BLOCKSIZE, MessageDigestAlgorithms.SHA_256);
    114    }
    115
    116    /**
    117     * Generates a libc6 crypt() compatible "$5$" hash value.
    118     * <p>
    119     * See {@link Crypt#crypt(String, String)} for details.
    120     * </p>
    121     * @param keyBytes
    122     *            plaintext to hash
    123     * @param salt
    124     *            real salt value without prefix or "rounds=".
    125     * @param random
    126     *            the instance of {@link Random} to use for generating the salt. Consider using {@link SecureRandom}
    127     *            or {@link ThreadLocalRandom}.
    128     * @return complete hash value including salt
    129     * @throws IllegalArgumentException
    130     *             if the salt does not match the allowed pattern
    131     * @throws IllegalArgumentException
    132     *             when a {@link java.security.NoSuchAlgorithmException} is caught.
    133     * @since 1.12
    134     */
    135    public static String sha256Crypt(final byte[] keyBytes, String salt, final Random random) {
    136        if (salt == null) {
    137            salt = SHA256_PREFIX + B64.getRandomSalt(8, random);
    138        }
    139        return sha2Crypt(keyBytes, salt, SHA256_PREFIX, SHA256_BLOCKSIZE, MessageDigestAlgorithms.SHA_256);
    140    }
    141
    142    /**
    143     * Generates a libc6 crypt() compatible "$5$" or "$6$" SHA2 based hash value.
    144     * <p>
    145     * This is a nearly line by line conversion of the original C function. The numbered comments are from the algorithm
    146     * description, the short C-style ones from the original C code and the ones with "Remark" from me.
    147     * <p>
    148     * See {@link Crypt#crypt(String, String)} for details.
    149     *
    150     * @param keyBytes
    151     *            plaintext to hash
    152     * @param salt
    153     *            real salt value without prefix or "rounds="; may not be null
    154     * @param saltPrefix
    155     *            either $5$ or $6$
    156     * @param blocksize
    157     *            a value that differs between $5$ and $6$
    158     * @param algorithm
    159     *            {@link MessageDigest} algorithm identifier string
    160     * @return complete hash value including prefix and salt
    161     * @throws IllegalArgumentException
    162     *             if the given salt is {@code null} or does not match the allowed pattern
    163     * @throws IllegalArgumentException
    164     *             when a {@link NoSuchAlgorithmException} is caught
    165     * @see MessageDigestAlgorithms
    166     */
    167    private static String sha2Crypt(final byte[] keyBytes, final String salt, final String saltPrefix,
    168            final int blocksize, final String algorithm) {
    169
    170        final int keyLen = keyBytes.length;
    171
    172        // Extracts effective salt and the number of rounds from the given salt.
    173        int rounds = ROUNDS_DEFAULT;
    174        boolean roundsCustom = false;
    175        if (salt == null) {
    176            throw new IllegalArgumentException("Salt must not be null");
    177        }
    178
    179        final Matcher m = SALT_PATTERN.matcher(salt);
    180        if (!m.find()) {
    181            throw new IllegalArgumentException("Invalid salt value: " + salt);
    182        }
    183        if (m.group(3) != null) {
    184            rounds = Integer.parseInt(m.group(3));
    185            rounds = Math.max(ROUNDS_MIN, Math.min(ROUNDS_MAX, rounds));
    186            roundsCustom = true;
    187        }
    188        final String saltString = m.group(4);
    189        final byte[] saltBytes = saltString.getBytes(StandardCharsets.UTF_8);
    190        final int saltLen = saltBytes.length;
    191
    192        // 1. start digest A
    193        // Prepare for the real work.
    194        MessageDigest ctx = DigestUtils.getDigest(algorithm);
    195
    196        // 2. the password string is added to digest A
    197        /*
    198         * Add the key string.
    199         */
    200        ctx.update(keyBytes);
    201
    202        // 3. the salt string is added to digest A. This is just the salt string
    203        // itself without the enclosing '$', without the magic salt_prefix $5$ and
    204        // $6$ respectively and without the rounds=<N> specification.
    205        //
    206        // NB: the MD5 algorithm did add the $1$ salt_prefix. This is not deemed
    207        // necessary since it is a constant string and does not add security
    208        // and /possibly/ allows a plain text attack. Since the rounds=<N>
    209        // specification should never be added this would also create an
    210        // inconsistency.
    211        /*
    212         * The last part is the salt string. This must be at most 16 characters and it ends at the first `$' character
    213         * (for compatibility with existing implementations).
    214         */
    215        ctx.update(saltBytes);
    216
    217        // 4. start digest B
    218        /*
    219         * Compute alternate sha512 sum with input KEY, SALT, and KEY. The final result will be added to the first
    220         * context.
    221         */
    222        MessageDigest altCtx = DigestUtils.getDigest(algorithm);
    223
    224        // 5. add the password to digest B
    225        /*
    226         * Add key.
    227         */
    228        altCtx.update(keyBytes);
    229
    230        // 6. add the salt string to digest B
    231        /*
    232         * Add salt.
    233         */
    234        altCtx.update(saltBytes);
    235
    236        // 7. add the password again to digest B
    237        /*
    238         * Add key again.
    239         */
    240        altCtx.update(keyBytes);
    241
    242        // 8. finish digest B
    243        /*
    244         * Now get result of this (32 bytes) and add it to the other context.
    245         */
    246        byte[] altResult = altCtx.digest();
    247
    248        // 9. For each block of 32 or 64 bytes in the password string (excluding
    249        // the terminating NUL in the C representation), add digest B to digest A
    250        /*
    251         * Add for any character in the key one byte of the alternate sum.
    252         */
    253        /*
    254         * (Remark: the C code comment seems wrong for key length > 32!)
    255         */
    256        int cnt = keyBytes.length;
    257        while (cnt > blocksize) {
    258            ctx.update(altResult, 0, blocksize);
    259            cnt -= blocksize;
    260        }
    261
    262        // 10. For the remaining N bytes of the password string add the first
    263        // N bytes of digest B to digest A
    264        ctx.update(altResult, 0, cnt);
    265
    266        // 11. For each bit of the binary representation of the length of the
    267        // password string up to and including the highest 1-digit, starting
    268        // from to lowest bit position (numeric value 1):
    269        //
    270        // a) for a 1-digit add digest B to digest A
    271        //
    272        // b) for a 0-digit add the password string
    273        //
    274        // NB: this step differs significantly from the MD5 algorithm. It
    275        // adds more randomness.
    276        /*
    277         * Take the binary representation of the length of the key and for every 1 add the alternate sum, for every 0
    278         * the key.
    279         */
    280        cnt = keyBytes.length;
    281        while (cnt > 0) {
    282            if ((cnt & 1) != 0) {
    283                ctx.update(altResult, 0, blocksize);
    284            } else {
    285                ctx.update(keyBytes);
    286            }
    287            cnt >>= 1;
    288        }
    289
    290        // 12. finish digest A
    291        /*
    292         * Create intermediate result.
    293         */
    294        altResult = ctx.digest();
    295
    296        // 13. start digest DP
    297        /*
    298         * Start computation of P byte sequence.
    299         */
    300        altCtx = DigestUtils.getDigest(algorithm);
    301
    302        // 14. for every byte in the password (excluding the terminating NUL byte
    303        // in the C representation of the string)
    304        //
    305        // add the password to digest DP
    306        /*
    307         * For every character in the password add the entire password.
    308         */
    309        for (int i = 1; i <= keyLen; i++) {
    310            altCtx.update(keyBytes);
    311        }
    312
    313        // 15. finish digest DP
    314        /*
    315         * Finish the digest.
    316         */
    317        byte[] tempResult = altCtx.digest();
    318
    319        // 16. produce byte sequence P of the same length as the password where
    320        //
    321        // a) for each block of 32 or 64 bytes of length of the password string
    322        // the entire digest DP is used
    323        //
    324        // b) for the remaining N (up to 31 or 63) bytes use the first N
    325        // bytes of digest DP
    326        /*
    327         * Create byte sequence P.
    328         */
    329        final byte[] pBytes = new byte[keyLen];
    330        int cp = 0;
    331        while (cp < keyLen - blocksize) {
    332            System.arraycopy(tempResult, 0, pBytes, cp, blocksize);
    333            cp += blocksize;
    334        }
    335        System.arraycopy(tempResult, 0, pBytes, cp, keyLen - cp);
    336
    337        // 17. start digest DS
    338        /*
    339         * Start computation of S byte sequence.
    340         */
    341        altCtx = DigestUtils.getDigest(algorithm);
    342
    343        // 18. repeast the following 16+A[0] times, where A[0] represents the first
    344        // byte in digest A interpreted as an 8-bit unsigned value
    345        //
    346        // add the salt to digest DS
    347        /*
    348         * For every character in the password add the entire password.
    349         */
    350        for (int i = 1; i <= 16 + (altResult[0] & 0xff); i++) {
    351            altCtx.update(saltBytes);
    352        }
    353
    354        // 19. finish digest DS
    355        /*
    356         * Finish the digest.
    357         */
    358        tempResult = altCtx.digest();
    359
    360        // 20. produce byte sequence S of the same length as the salt string where
    361        //
    362        // a) for each block of 32 or 64 bytes of length of the salt string
    363        // the entire digest DS is used
    364        //
    365        // b) for the remaining N (up to 31 or 63) bytes use the first N
    366        // bytes of digest DS
    367        /*
    368         * Create byte sequence S.
    369         */
    370        // Remark: The salt is limited to 16 chars, how does this make sense?
    371        final byte[] sBytes = new byte[saltLen];
    372        cp = 0;
    373        while (cp < saltLen - blocksize) {
    374            System.arraycopy(tempResult, 0, sBytes, cp, blocksize);
    375            cp += blocksize;
    376        }
    377        System.arraycopy(tempResult, 0, sBytes, cp, saltLen - cp);
    378
    379        // 21. repeat a loop according to the number specified in the rounds=<N>
    380        // specification in the salt (or the default value if none is
    381        // present). Each round is numbered, starting with 0 and up to N-1.
    382        //
    383        // The loop uses a digest as input. In the first round it is the
    384        // digest produced in step 12. In the latter steps it is the digest
    385        // produced in step 21.h. The following text uses the notation
    386        // "digest A/C" to describe this behavior.
    387        /*
    388         * Repeatedly run the collected hash value through sha512 to burn CPU cycles.
    389         */
    390        for (int i = 0; i <= rounds - 1; i++) {
    391            // a) start digest C
    392            /*
    393             * New context.
    394             */
    395            ctx = DigestUtils.getDigest(algorithm);
    396
    397            // b) for odd round numbers add the byte sequense P to digest C
    398            // c) for even round numbers add digest A/C
    399            /*
    400             * Add key or last result.
    401             */
    402            if ((i & 1) != 0) {
    403                ctx.update(pBytes, 0, keyLen);
    404            } else {
    405                ctx.update(altResult, 0, blocksize);
    406            }
    407
    408            // d) for all round numbers not divisible by 3 add the byte sequence S
    409            /*
    410             * Add salt for numbers not divisible by 3.
    411             */
    412            if (i % 3 != 0) {
    413                ctx.update(sBytes, 0, saltLen);
    414            }
    415
    416            // e) for all round numbers not divisible by 7 add the byte sequence P
    417            /*
    418             * Add key for numbers not divisible by 7.
    419             */
    420            if (i % 7 != 0) {
    421                ctx.update(pBytes, 0, keyLen);
    422            }
    423
    424            // f) for odd round numbers add digest A/C
    425            // g) for even round numbers add the byte sequence P
    426            /*
    427             * Add key or last result.
    428             */
    429            if ((i & 1) != 0) {
    430                ctx.update(altResult, 0, blocksize);
    431            } else {
    432                ctx.update(pBytes, 0, keyLen);
    433            }
    434
    435            // h) finish digest C.
    436            /*
    437             * Create intermediate result.
    438             */
    439            altResult = ctx.digest();
    440        }
    441
    442        // 22. Produce the output string. This is an ASCII string of the maximum
    443        // size specified above, consisting of multiple pieces:
    444        //
    445        // a) the salt salt_prefix, $5$ or $6$ respectively
    446        //
    447        // b) the rounds=<N> specification, if one was present in the input
    448        // salt string. A trailing '$' is added in this case to separate
    449        // the rounds specification from the following text.
    450        //
    451        // c) the salt string truncated to 16 characters
    452        //
    453        // d) a '$' character
    454        /*
    455         * Now we can construct the result string. It consists of three parts.
    456         */
    457        final StringBuilder buffer = new StringBuilder(saltPrefix);
    458        if (roundsCustom) {
    459            buffer.append(ROUNDS_PREFIX);
    460            buffer.append(rounds);
    461            buffer.append("$");
    462        }
    463        buffer.append(saltString);
    464        buffer.append("$");
    465
    466        // e) the base-64 encoded final C digest. The encoding used is as
    467        // follows:
    468        // [...]
    469        //
    470        // Each group of three bytes from the digest produces four
    471        // characters as output:
    472        //
    473        // 1. character: the six low bits of the first byte
    474        // 2. character: the two high bits of the first byte and the
    475        // four low bytes from the second byte
    476        // 3. character: the four high bytes from the second byte and
    477        // the two low bits from the third byte
    478        // 4. character: the six high bits from the third byte
    479        //
    480        // The groups of three bytes are as follows (in this sequence).
    481        // These are the indices into the byte array containing the
    482        // digest, starting with index 0. For the last group there are
    483        // not enough bytes left in the digest and the value zero is used
    484        // in its place. This group also produces only three or two
    485        // characters as output for SHA-512 and SHA-512 respectively.
    486
    487        // This was just a safeguard in the C implementation:
    488        // int buflen = salt_prefix.length() - 1 + ROUNDS_PREFIX.length() + 9 + 1 + salt_string.length() + 1 + 86 + 1;
    489
    490        if (blocksize == 32) {
    491            B64.b64from24bit(altResult[0], altResult[10], altResult[20], 4, buffer);
    492            B64.b64from24bit(altResult[21], altResult[1], altResult[11], 4, buffer);
    493            B64.b64from24bit(altResult[12], altResult[22], altResult[2], 4, buffer);
    494            B64.b64from24bit(altResult[3], altResult[13], altResult[23], 4, buffer);
    495            B64.b64from24bit(altResult[24], altResult[4], altResult[14], 4, buffer);
    496            B64.b64from24bit(altResult[15], altResult[25], altResult[5], 4, buffer);
    497            B64.b64from24bit(altResult[6], altResult[16], altResult[26], 4, buffer);
    498            B64.b64from24bit(altResult[27], altResult[7], altResult[17], 4, buffer);
    499            B64.b64from24bit(altResult[18], altResult[28], altResult[8], 4, buffer);
    500            B64.b64from24bit(altResult[9], altResult[19], altResult[29], 4, buffer);
    501            B64.b64from24bit((byte) 0, altResult[31], altResult[30], 3, buffer);
    502        } else {
    503            B64.b64from24bit(altResult[0], altResult[21], altResult[42], 4, buffer);
    504            B64.b64from24bit(altResult[22], altResult[43], altResult[1], 4, buffer);
    505            B64.b64from24bit(altResult[44], altResult[2], altResult[23], 4, buffer);
    506            B64.b64from24bit(altResult[3], altResult[24], altResult[45], 4, buffer);
    507            B64.b64from24bit(altResult[25], altResult[46], altResult[4], 4, buffer);
    508            B64.b64from24bit(altResult[47], altResult[5], altResult[26], 4, buffer);
    509            B64.b64from24bit(altResult[6], altResult[27], altResult[48], 4, buffer);
    510            B64.b64from24bit(altResult[28], altResult[49], altResult[7], 4, buffer);
    511            B64.b64from24bit(altResult[50], altResult[8], altResult[29], 4, buffer);
    512            B64.b64from24bit(altResult[9], altResult[30], altResult[51], 4, buffer);
    513            B64.b64from24bit(altResult[31], altResult[52], altResult[10], 4, buffer);
    514            B64.b64from24bit(altResult[53], altResult[11], altResult[32], 4, buffer);
    515            B64.b64from24bit(altResult[12], altResult[33], altResult[54], 4, buffer);
    516            B64.b64from24bit(altResult[34], altResult[55], altResult[13], 4, buffer);
    517            B64.b64from24bit(altResult[56], altResult[14], altResult[35], 4, buffer);
    518            B64.b64from24bit(altResult[15], altResult[36], altResult[57], 4, buffer);
    519            B64.b64from24bit(altResult[37], altResult[58], altResult[16], 4, buffer);
    520            B64.b64from24bit(altResult[59], altResult[17], altResult[38], 4, buffer);
    521            B64.b64from24bit(altResult[18], altResult[39], altResult[60], 4, buffer);
    522            B64.b64from24bit(altResult[40], altResult[61], altResult[19], 4, buffer);
    523            B64.b64from24bit(altResult[62], altResult[20], altResult[41], 4, buffer);
    524            B64.b64from24bit((byte) 0, (byte) 0, altResult[63], 2, buffer);
    525        }
    526
    527        /*
    528         * Clear the buffer for the intermediate result so that people attaching to processes or reading core dumps
    529         * cannot get any information.
    530         */
    531        // Is there a better way to do this with the JVM?
    532        Arrays.fill(tempResult, (byte) 0);
    533        Arrays.fill(pBytes, (byte) 0);
    534        Arrays.fill(sBytes, (byte) 0);
    535        ctx.reset();
    536        altCtx.reset();
    537        Arrays.fill(keyBytes, (byte) 0);
    538        Arrays.fill(saltBytes, (byte) 0);
    539
    540        return buffer.toString();
    541    }
    542
    543    /**
    544     * Generates a libc crypt() compatible "$6$" hash value with random salt.
    545     * <p>
    546     * See {@link Crypt#crypt(String, String)} for details.
    547     * </p>
    548     * <p>
    549     * A salt is generated for you using {@link ThreadLocalRandom}; for more secure salts consider using
    550     * {@link SecureRandom} to generate your own salts and calling {@link #sha512Crypt(byte[], String)}.
    551     * </p>
    552     *
    553     * @param keyBytes
    554     *            plaintext to hash
    555     * @return complete hash value
    556     * @throws IllegalArgumentException
    557     *             when a {@link java.security.NoSuchAlgorithmException} is caught.
    558     */
    559    public static String sha512Crypt(final byte[] keyBytes) {
    560        return sha512Crypt(keyBytes, null);
    561    }
    562
    563    /**
    564     * Generates a libc6 crypt() compatible "$6$" hash value.
    565     * <p>
    566     * See {@link Crypt#crypt(String, String)} for details.
    567     * </p>
    568     * @param keyBytes
    569     *            plaintext to hash
    570     * @param salt
    571     *            real salt value without prefix or "rounds=". The salt may be null, in which case a salt is generated
    572     *            for you using {@link SecureRandom}; if you want to use a {@link Random} object other than
    573     *            {@link SecureRandom} then we suggest you provide it using
    574     *            {@link #sha512Crypt(byte[], String, Random)}.
    575     * @return complete hash value including salt
    576     * @throws IllegalArgumentException
    577     *             if the salt does not match the allowed pattern
    578     * @throws IllegalArgumentException
    579     *             when a {@link java.security.NoSuchAlgorithmException} is caught.
    580     */
    581    public static String sha512Crypt(final byte[] keyBytes, String salt) {
    582        if (salt == null) {
    583            salt = SHA512_PREFIX + B64.getRandomSalt(8);
    584        }
    585        return sha2Crypt(keyBytes, salt, SHA512_PREFIX, SHA512_BLOCKSIZE, MessageDigestAlgorithms.SHA_512);
    586    }
    587
    588
    589
    590    /**
    591     * Generates a libc6 crypt() compatible "$6$" hash value.
    592     * <p>
    593     * See {@link Crypt#crypt(String, String)} for details.
    594     * </p>
    595     * @param keyBytes
    596     *            plaintext to hash
    597     * @param salt
    598     *            real salt value without prefix or "rounds=". The salt may be null, in which case a salt
    599     *            is generated for you using {@link ThreadLocalRandom}; for more secure salts consider using
    600     *            {@link SecureRandom} to generate your own salts.
    601     * @param random
    602     *            the instance of {@link Random} to use for generating the salt. Consider using {@link SecureRandom}
    603     *            or {@link ThreadLocalRandom}.
    604     * @return complete hash value including salt
    605     * @throws IllegalArgumentException
    606     *             if the salt does not match the allowed pattern
    607     * @throws IllegalArgumentException
    608     *             when a {@link java.security.NoSuchAlgorithmException} is caught.
    609     * @since 1.12
    610     */
    611    public static String sha512Crypt(final byte[] keyBytes, String salt, final Random random) {
    612        if (salt == null) {
    613            salt = SHA512_PREFIX + B64.getRandomSalt(8, random);
    614        }
    615        return sha2Crypt(keyBytes, salt, SHA512_PREFIX, SHA512_BLOCKSIZE, MessageDigestAlgorithms.SHA_512);
    616    }
    617}