package org.elasticsearch.xpack.security.authc.support;

// Copyright (c) 2006 Damien Miller <djm@mindrot.org>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

import org.elasticsearch.common.settings.SecureString;

import java.security.SecureRandom;

/**
 * BCrypt implements OpenBSD-style Blowfish password hashing using
 * the scheme described in "A Future-Adaptable Password Scheme" by
 * Niels Provos and David Mazieres.
 * <p>
 * This password hashing system tries to thwart off-line password
 * cracking using a computationally-intensive hashing algorithm,
 * based on Bruce Schneier's Blowfish cipher. The work factor of
 * the algorithm is parameterised, so it can be increased as
 * computers get faster.
 * <p>
 * Usage is really simple. To hash a password for the first time,
 * call the hashpw method with a random salt, like this:
 * <p>
 * <code>
 * String pw_hash = BCrypt.hashpw(plain_password, BCrypt.gensalt()); <br>
 * </code>
 * <p>
 * To check whether a plaintext password matches one that has been
 * hashed previously, use the checkpw method:
 * <p>
 * <code>
 * if (BCrypt.checkpw(candidate_password, stored_hash))<br>
 * &nbsp;&nbsp;&nbsp;&nbsp;System.out.println("It matches");<br>
 * else<br>
 * &nbsp;&nbsp;&nbsp;&nbsp;System.out.println("It does not match");<br>
 * </code>
 * <p>
 * The gensalt() method takes an optional parameter (log_rounds)
 * that determines the computational complexity of the hashing:
 * <p>
 * <code>
 * String strong_salt = BCrypt.gensalt(10)<br>
 * String stronger_salt = BCrypt.gensalt(12)<br>
 * </code>
 * <p>
 * The amount of work increases exponentially (2**log_rounds), so 
 * each increment is twice as much work. The default log_rounds is
 * 10, and the valid range is 4 to 30.
 *
 * @author Damien Miller
 * @version 0.2
 */
public class BCrypt {
    // BCrypt parameters
    private static final int GENSALT_DEFAULT_LOG2_ROUNDS = 10;
    private static final int BCRYPT_SALT_LEN = 16;

    // Blowfish parameters
    private static final int BLOWFISH_NUM_ROUNDS = 16;

    // Initial contents of key schedule
    private static final int P_orig[] = {
        0x243f6a88, 0x85a308d3, 0x13198a2e, 0x03707344,
        0xa4093822, 0x299f31d0, 0x082efa98, 0xec4e6c89,
        0x452821e6, 0x38d01377, 0xbe5466cf, 0x34e90c6c,
        0xc0ac29b7, 0xc97c50dd, 0x3f84d5b5, 0xb5470917,
        0x9216d5d9, 0x8979fb1b
    };
    private static final int S_orig[] = {
        0xd1310ba6, 0x98dfb5ac, 0x2ffd72db, 0xd01adfb7,
        0xb8e1afed, 0x6a267e96, 0xba7c9045, 0xf12c7f99,
        0x24a19947, 0xb3916cf7, 0x0801f2e2, 0x858efc16,
        0x636920d8, 0x71574e69, 0xa458fea3, 0xf4933d7e,
        0x0d95748f, 0x728eb658, 0x718bcd58, 0x82154aee,
        0x7b54a41d, 0xc25a59b5, 0x9c30d539, 0x2af26013,
        0xc5d1b023, 0x286085f0, 0xca417918, 0xb8db38ef,
        0x8e79dcb0, 0x603a180e, 0x6c9e0e8b, 0xb01e8a3e,
        0xd71577c1, 0xbd314b27, 0x78af2fda, 0x55605c60,
        0xe65525f3, 0xaa55ab94, 0x57489862, 0x63e81440,
        0x55ca396a, 0x2aab10b6, 0xb4cc5c34, 0x1141e8ce,
        0xa15486af, 0x7c72e993, 0xb3ee1411, 0x636fbc2a,
        0x2ba9c55d, 0x741831f6, 0xce5c3e16, 0x9b87931e,
        0xafd6ba33, 0x6c24cf5c, 0x7a325381, 0x28958677,
        0x3b8f4898, 0x6b4bb9af, 0xc4bfe81b, 0x66282193,
        0x61d809cc, 0xfb21a991, 0x487cac60, 0x5dec8032,
        0xef845d5d, 0xe98575b1, 0xdc262302, 0xeb651b88,
        0x23893e81, 0xd396acc5, 0x0f6d6ff3, 0x83f44239,
        0x2e0b4482, 0xa4842004, 0x69c8f04a, 0x9e1f9b5e,
        0x21c66842, 0xf6e96c9a, 0x670c9c61, 0xabd388f0,
        0x6a51a0d2, 0xd8542f68, 0x960fa728, 0xab5133a3,
        0x6eef0b6c, 0x137a3be4, 0xba3bf050, 0x7efb2a98,
        0xa1f1651d, 0x39af0176, 0x66ca593e, 0x82430e88,
        0x8cee8619, 0x456f9fb4, 0x7d84a5c3, 0x3b8b5ebe,
        0xe06f75d8, 0x85c12073, 0x401a449f, 0x56c16aa6,
        0x4ed3aa62, 0x363f7706, 0x1bfedf72, 0x429b023d,
        0x37d0d724, 0xd00a1248, 0xdb0fead3, 0x49f1c09b,
        0x075372c9, 0x80991b7b, 0x25d479d8, 0xf6e8def7,
        0xe3fe501a, 0xb6794c3b, 0x976ce0bd, 0x04c006ba,
        0xc1a94fb6, 0x409f60c4, 0x5e5c9ec2, 0x196a2463,
        0x68fb6faf, 0x3e6c53b5, 0x1339b2eb, 0x3b52ec6f,
        0x6dfc511f, 0x9b30952c, 0xcc814544, 0xaf5ebd09,
        0xbee3d004, 0xde334afd, 0x660f2807, 0x192e4bb3,
        0xc0cba857, 0x45c8740f, 0xd20b5f39, 0xb9d3fbdb,
        0x5579c0bd, 0x1a60320a, 0xd6a100c6, 0x402c7279,
        0x679f25fe, 0xfb1fa3cc, 0x8ea5e9f8, 0xdb3222f8,
        0x3c7516df, 0xfd616b15, 0x2f501ec8, 0xad0552ab,
        0x323db5fa, 0xfd238760, 0x53317b48, 0x3e00df82,
        0x9e5c57bb, 0xca6f8ca0, 0x1a87562e, 0xdf1769db,
        0xd542a8f6, 0x287effc3, 0xac6732c6, 0x8c4f5573,
        0x695b27b0, 0xbbca58c8, 0xe1ffa35d, 0xb8f011a0,
        0x10fa3d98, 0xfd2183b8, 0x4afcb56c, 0x2dd1d35b,
        0x9a53e479, 0xb6f84565, 0xd28e49bc, 0x4bfb9790,
        0xe1ddf2da, 0xa4cb7e33, 0x62fb1341, 0xcee4c6e8,
        0xef20cada, 0x36774c01, 0xd07e9efe, 0x2bf11fb4,
        0x95dbda4d, 0xae909198, 0xeaad8e71, 0x6b93d5a0,
        0xd08ed1d0, 0xafc725e0, 0x8e3c5b2f, 0x8e7594b7,
        0x8ff6e2fb, 0xf2122b64, 0x8888b812, 0x900df01c,
        0x4fad5ea0, 0x688fc31c, 0xd1cff191, 0xb3a8c1ad,
        0x2f2f2218, 0xbe0e1777, 0xea752dfe, 0x8b021fa1,
        0xe5a0cc0f, 0xb56f74e8, 0x18acf3d6, 0xce89e299,
        0xb4a84fe0, 0xfd13e0b7, 0x7cc43b81, 0xd2ada8d9,
        0x165fa266, 0x80957705, 0x93cc7314, 0x211a1477,
        0xe6ad2065, 0x77b5fa86, 0xc75442f5, 0xfb9d35cf,
        0xebcdaf0c, 0x7b3e89a0, 0xd6411bd3, 0xae1e7e49,
        0x00250e2d, 0x2071b35e, 0x226800bb, 0x57b8e0af,
        0x2464369b, 0xf009b91e, 0x5563911d, 0x59dfa6aa,
        0x78c14389, 0xd95a537f, 0x207d5ba2, 0x02e5b9c5,
        0x83260376, 0x6295cfa9, 0x11c81968, 0x4e734a41,
        0xb3472dca, 0x7b14a94a, 0x1b510052, 0x9a532915,
        0xd60f573f, 0xbc9bc6e4, 0x2b60a476, 0x81e67400,
        0x08ba6fb5, 0x571be91f, 0xf296ec6b, 0x2a0dd915,
        0xb6636521, 0xe7b9f9b6, 0xff34052e, 0xc5855664,
        0x53b02d5d, 0xa99f8fa1, 0x08ba4799, 0x6e85076a,
        0x4b7a70e9, 0xb5b32944, 0xdb75092e, 0xc4192623,
        0xad6ea6b0, 0x49a7df7d, 0x9cee60b8, 0x8fedb266,
        0xecaa8c71, 0x699a17ff, 0x5664526c, 0xc2b19ee1,
        0x193602a5, 0x75094c29, 0xa0591340, 0xe4183a3e,
        0x3f54989a, 0x5b429d65, 0x6b8fe4d6, 0x99f73fd6,
        0xa1d29c07, 0xefe830f5, 0x4d2d38e6, 0xf0255dc1,
        0x4cdd2086, 0x8470eb26, 0x6382e9c6, 0x021ecc5e,
        0x09686b3f, 0x3ebaefc9, 0x3c971814, 0x6b6a70a1,
        0x687f3584, 0x52a0e286, 0xb79c5305, 0xaa500737,
        0x3e07841c, 0x7fdeae5c, 0x8e7d44ec, 0x5716f2b8,
        0xb03ada37, 0xf0500c0d, 0xf01c1f04, 0x0200b3ff,
        0xae0cf51a, 0x3cb574b2, 0x25837a58, 0xdc0921bd,
        0xd19113f9, 0x7ca92ff6, 0x94324773, 0x22f54701,
        0x3ae5e581, 0x37c2dadc, 0xc8b57634, 0x9af3dda7,
        0xa9446146, 0x0fd0030e, 0xecc8c73e, 0xa4751e41,
        0xe238cd99, 0x3bea0e2f, 0x3280bba1, 0x183eb331,
        0x4e548b38, 0x4f6db908, 0x6f420d03, 0xf60a04bf,
        0x2cb81290, 0x24977c79, 0x5679b072, 0xbcaf89af,
        0xde9a771f, 0xd9930810, 0xb38bae12, 0xdccf3f2e,
        0x5512721f, 0x2e6b7124, 0x501adde6, 0x9f84cd87,
        0x7a584718, 0x7408da17, 0xbc9f9abc, 0xe94b7d8c,
        0xec7aec3a, 0xdb851dfa, 0x63094366, 0xc464c3d2,
        0xef1c1847, 0x3215d908, 0xdd433b37, 0x24c2ba16,
        0x12a14d43, 0x2a65c451, 0x50940002, 0x133ae4dd,
        0x71dff89e, 0x10314e55, 0x81ac77d6, 0x5f11199b,
        0x043556f1, 0xd7a3c76b, 0x3c11183b, 0x5924a509,
        0xf28fe6ed, 0x97f1fbfa, 0x9ebabf2c, 0x1e153c6e,
        0x86e34570, 0xeae96fb1, 0x860e5e0a, 0x5a3e2ab3,
        0x771fe71c, 0x4e3d06fa, 0x2965dcb9, 0x99e71d0f,
        0x803e89d6, 0x5266c825, 0x2e4cc978, 0x9c10b36a,
        0xc6150eba, 0x94e2ea78, 0xa5fc3c53, 0x1e0a2df4,
        0xf2f74ea7, 0x361d2b3d, 0x1939260f, 0x19c27960,
        0x5223a708, 0xf71312b6, 0xebadfe6e, 0xeac31f66,
        0xe3bc4595, 0xa67bc883, 0xb17f37d1, 0x018cff28,
        0xc332ddef, 0xbe6c5aa5, 0x65582185, 0x68ab9802,
        0xeecea50f, 0xdb2f953b, 0x2aef7dad, 0x5b6e2f84,
        0x1521b628, 0x29076170, 0xecdd4775, 0x619f1510,
        0x13cca830, 0xeb61bd96, 0x0334fe1e, 0xaa0363cf,
        0xb5735c90, 0x4c70a239, 0xd59e9e0b, 0xcbaade14,
        0xeecc86bc, 0x60622ca7, 0x9cab5cab, 0xb2f3846e,
        0x648b1eaf, 0x19bdf0ca, 0xa02369b9, 0x655abb50,
        0x40685a32, 0x3c2ab4b3, 0x319ee9d5, 0xc021b8f7,
        0x9b540b19, 0x875fa099, 0x95f7997e, 0x623d7da8,
        0xf837889a, 0x97e32d77, 0x11ed935f, 0x16681281,
        0x0e358829, 0xc7e61fd6, 0x96dedfa1, 0x7858ba99,
        0x57f584a5, 0x1b227263, 0x9b83c3ff, 0x1ac24696,
        0xcdb30aeb, 0x532e3054, 0x8fd948e4, 0x6dbc3128,
        0x58ebf2ef, 0x34c6ffea, 0xfe28ed61, 0xee7c3c73,
        0x5d4a14d9, 0xe864b7e3, 0x42105d14, 0x203e13e0,
        0x45eee2b6, 0xa3aaabea, 0xdb6c4f15, 0xfacb4fd0,
        0xc742f442, 0xef6abbb5, 0x654f3b1d, 0x41cd2105,
        0xd81e799e, 0x86854dc7, 0xe44b476a, 0x3d816250,
        0xcf62a1f2, 0x5b8d2646, 0xfc8883a0, 0xc1c7b6a3,
        0x7f1524c3, 0x69cb7492, 0x47848a0b, 0x5692b285,
        0x095bbf00, 0xad19489d, 0x1462b174, 0x23820e00,
        0x58428d2a, 0x0c55f5ea, 0x1dadf43e, 0x233f7061,
        0x3372f092, 0x8d937e41, 0xd65fecf1, 0x6c223bdb,
        0x7cde3759, 0xcbee7460, 0x4085f2a7, 0xce77326e,
        0xa6078084, 0x19f8509e, 0xe8efd855, 0x61d99735,
        0xa969a7aa, 0xc50c06c2, 0x5a04abfc, 0x800bcadc,
        0x9e447a2e, 0xc3453484, 0xfdd56705, 0x0e1e9ec9,
        0xdb73dbd3, 0x105588cd, 0x675fda79, 0xe3674340,
        0xc5c43465, 0x713e38d8, 0x3d28f89e, 0xf16dff20,
        0x153e21e7, 0x8fb03d4a, 0xe6e39f2b, 0xdb83adf7,
        0xe93d5a68, 0x948140f7, 0xf64c261c, 0x94692934,
        0x411520f7, 0x7602d4f7, 0xbcf46b2e, 0xd4a20068,
        0xd4082471, 0x3320f46a, 0x43b7d4b7, 0x500061af,
        0x1e39f62e, 0x97244546, 0x14214f74, 0xbf8b8840,
        0x4d95fc1d, 0x96b591af, 0x70f4ddd3, 0x66a02f45,
        0xbfbc09ec, 0x03bd9785, 0x7fac6dd0, 0x31cb8504,
        0x96eb27b3, 0x55fd3941, 0xda2547e6, 0xabca0a9a,
        0x28507825, 0x530429f4, 0x0a2c86da, 0xe9b66dfb,
        0x68dc1462, 0xd7486900, 0x680ec0a4, 0x27a18dee,
        0x4f3ffea2, 0xe887ad8c, 0xb58ce006, 0x7af4d6b6,
        0xaace1e7c, 0xd3375fec, 0xce78a399, 0x406b2a42,
        0x20fe9e35, 0xd9f385b9, 0xee39d7ab, 0x3b124e8b,
        0x1dc9faf7, 0x4b6d1856, 0x26a36631, 0xeae397b2,
        0x3a6efa74, 0xdd5b4332, 0x6841e7f7, 0xca7820fb,
        0xfb0af54e, 0xd8feb397, 0x454056ac, 0xba489527,
        0x55533a3a, 0x20838d87, 0xfe6ba9b7, 0xd096954b,
        0x55a867bc, 0xa1159a58, 0xcca92963, 0x99e1db33,
        0xa62a4a56, 0x3f3125f9, 0x5ef47e1c, 0x9029317c,
        0xfdf8e802, 0x04272f70, 0x80bb155c, 0x05282ce3,
        0x95c11548, 0xe4c66d22, 0x48c1133f, 0xc70f86dc,
        0x07f9c9ee, 0x41041f0f, 0x404779a4, 0x5d886e17,
        0x325f51eb, 0xd59bc0d1, 0xf2bcc18f, 0x41113564,
        0x257b7834, 0x602a9c60, 0xdff8e8a3, 0x1f636c1b,
        0x0e12b4c2, 0x02e1329e, 0xaf664fd1, 0xcad18115,
        0x6b2395e0, 0x333e92e1, 0x3b240b62, 0xeebeb922,
        0x85b2a20e, 0xe6ba0d99, 0xde720c8c, 0x2da2f728,
        0xd0127845, 0x95b794fd, 0x647d0862, 0xe7ccf5f0,
        0x5449a36f, 0x877d48fa, 0xc39dfd27, 0xf33e8d1e,
        0x0a476341, 0x992eff74, 0x3a6f6eab, 0xf4f8fd37,
        0xa812dc60, 0xa1ebddf8, 0x991be14c, 0xdb6e6b0d,
        0xc67b5510, 0x6d672c37, 0x2765d43b, 0xdcd0e804,
        0xf1290dc7, 0xcc00ffa3, 0xb5390f92, 0x690fed0b,
        0x667b9ffb, 0xcedb7d9c, 0xa091cf0b, 0xd9155ea3,
        0xbb132f88, 0x515bad24, 0x7b9479bf, 0x763bd6eb,
        0x37392eb3, 0xcc115979, 0x8026e297, 0xf42e312d,
        0x6842ada7, 0xc66a2b3b, 0x12754ccc, 0x782ef11c,
        0x6a124237, 0xb79251e7, 0x06a1bbe6, 0x4bfb6350,
        0x1a6b1018, 0x11caedfa, 0x3d25bdd8, 0xe2e1c3c9,
        0x44421659, 0x0a121386, 0xd90cec6e, 0xd5abea2a,
        0x64af674e, 0xda86a85f, 0xbebfe988, 0x64e4c3fe,
        0x9dbc8057, 0xf0f7c086, 0x60787bf8, 0x6003604d,
        0xd1fd8346, 0xf6381fb0, 0x7745ae04, 0xd736fccc,
        0x83426b33, 0xf01eab71, 0xb0804187, 0x3c005e5f,
        0x77a057be, 0xbde8ae24, 0x55464299, 0xbf582e61,
        0x4e58f48f, 0xf2ddfda2, 0xf474ef38, 0x8789bdc2,
        0x5366f9c3, 0xc8b38e74, 0xb475f255, 0x46fcd9b9,
        0x7aeb2661, 0x8b1ddf84, 0x846a0e79, 0x915f95e2,
        0x466e598e, 0x20b45770, 0x8cd55591, 0xc902de4c,
        0xb90bace1, 0xbb8205d0, 0x11a86248, 0x7574a99e,
        0xb77f19b6, 0xe0a9dc09, 0x662d09a1, 0xc4324633,
        0xe85a1f02, 0x09f0be8c, 0x4a99a025, 0x1d6efe10,
        0x1ab93d1d, 0x0ba5a4df, 0xa186f20f, 0x2868f169,
        0xdcb7da83, 0x573906fe, 0xa1e2ce9b, 0x4fcd7f52,
        0x50115e01, 0xa70683fa, 0xa002b5c4, 0x0de6d027,
        0x9af88c27, 0x773f8641, 0xc3604c06, 0x61a806b5,
        0xf0177a28, 0xc0f586e0, 0x006058aa, 0x30dc7d62,
        0x11e69ed7, 0x2338ea63, 0x53c2dd94, 0xc2c21634,
        0xbbcbee56, 0x90bcb6de, 0xebfc7da1, 0xce591d76,
        0x6f05e409, 0x4b7c0188, 0x39720a3d, 0x7c927c24,
        0x86e3725f, 0x724d9db9, 0x1ac15bb4, 0xd39eb8fc,
        0xed545578, 0x08fca5b5, 0xd83d7cd3, 0x4dad0fc4,
        0x1e50ef5e, 0xb161e6f8, 0xa28514d9, 0x6c51133c,
        0x6fd5c7e7, 0x56e14ec4, 0x362abfce, 0xddc6c837,
        0xd79a3234, 0x92638212, 0x670efa8e, 0x406000e0,
        0x3a39ce37, 0xd3faf5cf, 0xabc27737, 0x5ac52d1b,
        0x5cb0679e, 0x4fa33742, 0xd3822740, 0x99bc9bbe,
        0xd5118e9d, 0xbf0f7315, 0xd62d1c7e, 0xc700c47b,
        0xb78c1b6b, 0x21a19045, 0xb26eb1be, 0x6a366eb4,
        0x5748ab2f, 0xbc946e79, 0xc6a376d2, 0x6549c2c8,
        0x530ff8ee, 0x468dde7d, 0xd5730a1d, 0x4cd04dc6,
        0x2939bbdb, 0xa9ba4650, 0xac9526e8, 0xbe5ee304,
        0xa1fad5f0, 0x6a2d519a, 0x63ef8ce2, 0x9a86ee22,
        0xc089c2b8, 0x43242ef6, 0xa51e03aa, 0x9cf2d0a4,
        0x83c061ba, 0x9be96a4d, 0x8fe51550, 0xba645bd6,
        0x2826a2f9, 0xa73a3ae1, 0x4ba99586, 0xef5562e9,
        0xc72fefd3, 0xf752f7da, 0x3f046f69, 0x77fa0a59,
        0x80e4a915, 0x87b08601, 0x9b09e6ad, 0x3b3ee593,
        0xe990fd5a, 0x9e34d797, 0x2cf0b7d9, 0x022b8b51,
        0x96d5ac3a, 0x017da67d, 0xd1cf3ed6, 0x7c7d2d28,
        0x1f9f25cf, 0xadf2b89b, 0x5ad6b472, 0x5a88f54c,
        0xe029ac71, 0xe019a5e6, 0x47b0acfd, 0xed93fa9b,
        0xe8d3c48d, 0x283b57cc, 0xf8d56629, 0x79132e28,
        0x785f0191, 0xed756055, 0xf7960e44, 0xe3d35e8c,
        0x15056dd4, 0x88f46dba, 0x03a16125, 0x0564f0bd,
        0xc3eb9e15, 0x3c9057a2, 0x97271aec, 0xa93a072a,
        0x1b3f6d9b, 0x1e6321f5, 0xf59c66fb, 0x26dcf319,
        0x7533d928, 0xb155fdf5, 0x03563482, 0x8aba3cbb,
        0x28517711, 0xc20ad9f8, 0xabcc5167, 0xccad925f,
        0x4de81751, 0x3830dc8e, 0x379d5862, 0x9320f991,
        0xea7a90c2, 0xfb3e7bce, 0x5121ce64, 0x774fbe32,
        0xa8b6e37e, 0xc3293d46, 0x48de5369, 0x6413e680,
        0xa2ae0810, 0xdd6db224, 0x69852dfd, 0x09072166,
        0xb39a460a, 0x6445c0dd, 0x586cdecf, 0x1c20c8ae,
        0x5bbef7dd, 0x1b588d40, 0xccd2017f, 0x6bb4e3bb,
        0xdda26a7e, 0x3a59ff45, 0x3e350a44, 0xbcb4cdd5,
        0x72eacea8, 0xfa6484bb, 0x8d6612ae, 0xbf3c6f47,
        0xd29be463, 0x542f5d9e, 0xaec2771b, 0xf64e6370,
        0x740e0d8d, 0xe75b1357, 0xf8721671, 0xaf537d5d,
        0x4040cb08, 0x4eb4e2cc, 0x34d2466a, 0x0115af84,
        0xe1b00428, 0x95983a1d, 0x06b89fb4, 0xce6ea048,
        0x6f3f3b82, 0x3520ab82, 0x011a1d4b, 0x277227f8,
        0x611560b1, 0xe7933fdc, 0xbb3a792b, 0x344525bd,
        0xa08839e1, 0x51ce794b, 0x2f32c9b7, 0xa01fbac9,
        0xe01cc87e, 0xbcc7d1f6, 0xcf0111c3, 0xa1e8aac7,
        0x1a908749, 0xd44fbd9a, 0xd0dadecb, 0xd50ada38,
        0x0339c32a, 0xc6913667, 0x8df9317c, 0xe0b12b4f,
        0xf79e59b7, 0x43f5bb3a, 0xf2d519ff, 0x27d9459c,
        0xbf97222c, 0x15e6fc2a, 0x0f91fc71, 0x9b941525,
        0xfae59361, 0xceb69ceb, 0xc2a86459, 0x12baa8d1,
        0xb6c1075e, 0xe3056a0c, 0x10d25065, 0xcb03a442,
        0xe0ec6e0e, 0x1698db3b, 0x4c98a0be, 0x3278e964,
        0x9f1f9532, 0xe0d392df, 0xd3a0342b, 0x8971f21e,
        0x1b0a7441, 0x4ba3348c, 0xc5be7120, 0xc37632d8,
        0xdf359f8d, 0x9b992f2e, 0xe60b6f47, 0x0fe3f11d,
        0xe54cda54, 0x1edad891, 0xce6279cf, 0xcd3e7e6f,
        0x1618b166, 0xfd2c1d05, 0x848fd2c5, 0xf6fb2299,
        0xf523f357, 0xa6327623, 0x93a83531, 0x56cccd02,
        0xacf08162, 0x5a75ebb5, 0x6e163697, 0x88d273cc,
        0xde966292, 0x81b949d0, 0x4c50901b, 0x71c65614,
        0xe6c6c7bd, 0x327a140a, 0x45e1d006, 0xc3f27b9a,
        0xc9aa53fd, 0x62a80f00, 0xbb25bfe2, 0x35bdd2f6,
        0x71126905, 0xb2040222, 0xb6cbcf7c, 0xcd769c2b,
        0x53113ec0, 0x1640e3d3, 0x38abbd60, 0x2547adf0,
        0xba38209c, 0xf746ce76, 0x77afa1c5, 0x20756060,
        0x85cbfe4e, 0x8ae88dd8, 0x7aaaf9b0, 0x4cf9aa7e,
        0x1948c25c, 0x02fb8a8c, 0x01c36ae4, 0xd6ebe1f9,
        0x90d4f869, 0xa65cdea0, 0x3f09252d, 0xc208e69f,
        0xb74e6132, 0xce77e25b, 0x578fdfe3, 0x3ac372e6
    };

    // bcrypt IV: "OrpheanBeholderScryDoubt". The C implementation calls
    // this "ciphertext", but it is really plaintext or an IV. We keep
    // the name to make code comparison easier.
    private static final int bf_crypt_ciphertext[] = {
        0x4f727068, 0x65616e42, 0x65686f6c,
        0x64657253, 0x63727944, 0x6f756274
    };

    // Table for Base64 encoding
    private static final char base64_code[] = {
        '.', '/', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
        'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
        'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
        'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
        '6', '7', '8', '9'
    };

    // Table for Base64 decoding
    private static final byte index_64[] = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, 0, 1, 54, 55,
        56, 57, 58, 59, 60, 61, 62, 63, -1, -1,
        -1, -1, -1, -1, -1, 2, 3, 4, 5, 6,
        7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
        17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
        -1, -1, -1, -1, -1, -1, 28, 29, 30,
        31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
        41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
        51, 52, 53, -1, -1, -1, -1, -1
    };

    // Expanded Blowfish key
    private int P[];
    private int S[];

    /**
     * Encode a byte array using bcrypt's slightly-modified base64
     * encoding scheme. Note that this is *not* compatible with
     * the standard MIME-base64 encoding.
     *
     * @param d   the byte array to encode
     * @param len the number of bytes to encode
     * @return    base64-encoded string
     * @exception IllegalArgumentException if the length is invalid
     */
    private static String encode_base64(byte d[], int len)
            throws IllegalArgumentException {
        int off = 0;
        StringBuffer rs = new StringBuffer();
        int c1, c2;

        if (len <= 0 || len > d.length)
            throw new IllegalArgumentException ("Invalid len");

        while (off < len) {
            c1 = d[off++] & 0xff;
            rs.append(base64_code[(c1 >> 2) & 0x3f]);
            c1 = (c1 & 0x03) << 4;
            if (off >= len) {
                rs.append(base64_code[c1 & 0x3f]);
                break;
            }
            c2 = d[off++] & 0xff;
            c1 |= (c2 >> 4) & 0x0f;
            rs.append(base64_code[c1 & 0x3f]);
            c1 = (c2 & 0x0f) << 2;
            if (off >= len) {
                rs.append(base64_code[c1 & 0x3f]);
                break;
            }
            c2 = d[off++] & 0xff;
            c1 |= (c2 >> 6) & 0x03;
            rs.append(base64_code[c1 & 0x3f]);
            rs.append(base64_code[c2 & 0x3f]);
        }
        return rs.toString();
    }

    /**
     * Look up the 3 bits base64-encoded by the specified character,
     * range-checking againt conversion table
     * @param x the base64-encoded value
     * @return  the decoded value of x
     */
    private static byte char64(char x) {
        if ((int)x < 0 || (int)x > index_64.length)
            return -1;
        return index_64[(int)x];
    }

    /**
     * Decode a string encoded using bcrypt's base64 scheme to a
     * byte array. Note that this is *not* compatible with
     * the standard MIME-base64 encoding.
     * @param s         the string to decode
     * @param maxolen   the maximum number of bytes to decode
     * @return          an array containing the decoded bytes
     * @throws          IllegalArgumentException if maxolen is invalid
     */
    private static byte[] decode_base64(String s, int maxolen)
            throws IllegalArgumentException {
        StringBuffer rs = new StringBuffer();
        int off = 0, slen = s.length(), olen = 0;
        byte ret[];
        byte c1, c2, c3, c4, o;

        if (maxolen <= 0)
            throw new IllegalArgumentException ("Invalid maxolen");

        while (off < slen - 1 && olen < maxolen) {
            c1 = char64(s.charAt(off++));
            c2 = char64(s.charAt(off++));
            if (c1 == -1 || c2 == -1)
                break;
            o = (byte)(c1 << 2);
            o |= (c2 & 0x30) >> 4;
            rs.append((char)o);
            if (++olen >= maxolen || off >= slen)
                break;
            c3 = char64(s.charAt(off++));
            if (c3 == -1)
                break;
            o = (byte)((c2 & 0x0f) << 4);
            o |= (c3 & 0x3c) >> 2;
            rs.append((char)o);
            if (++olen >= maxolen || off >= slen)
                break;
            c4 = char64(s.charAt(off++));
            o = (byte)((c3 & 0x03) << 6);
            o |= c4;
            rs.append((char)o);
            ++olen;
        }

        ret = new byte[olen];
        for (off = 0; off < olen; off++)
            ret[off] = (byte)rs.charAt(off);
        return ret;
    }

    /**
     * Blowfish encipher a single 64-bit block encoded as
     * two 32-bit halves
     * @param lr    an array containing the two 32-bit half blocks
     * @param off   the position in the array of the blocks
     */
    private void encipher(int lr[], int off) {
        int i, n, l = lr[off], r = lr[off + 1];

        l ^= P[0];
        for (i = 0; i <= BLOWFISH_NUM_ROUNDS - 2;) {
            // Feistel substitution on left word
            n = S[(l >> 24) & 0xff];
            n += S[0x100 | ((l >> 16) & 0xff)];
            n ^= S[0x200 | ((l >> 8) & 0xff)];
            n += S[0x300 | (l & 0xff)];
            r ^= n ^ P[++i];

            // Feistel substitution on right word
            n = S[(r >> 24) & 0xff];
            n += S[0x100 | ((r >> 16) & 0xff)];
            n ^= S[0x200 | ((r >> 8) & 0xff)];
            n += S[0x300 | (r & 0xff)];
            l ^= n ^ P[++i];
        }
        lr[off] = r ^ P[BLOWFISH_NUM_ROUNDS + 1];
        lr[off + 1] = l;
    }

    /**
     * Cycically extract a word of key material
     * @param data  the string to extract the data from
     * @param offp  a "pointer" (as a one-entry array) to the
     *              current offset into data
     * @return      the next word of material from data
     */
    private static int streamtoword(byte data[], int offp[]) {
        int i;
        int word = 0;
        int off = offp[0];

        for (i = 0; i < 4; i++) {
            word = (word << 8) | (data[off] & 0xff);
            off = (off + 1) % data.length;
        }

        offp[0] = off;
        return word;
    }

    /**
     * Initialise the Blowfish key schedule
     */
    private void init_key() {
        P = P_orig.clone();
        S = S_orig.clone();
    }

    /**
     * Key the Blowfish cipher
     * @param key  an array containing the key
     */
    private void key(byte key[]) {
        int i;
        int koffp[] = { 0 };
        int lr[] = { 0, 0 };
        int plen = P.length, slen = S.length;

        for (i = 0; i < plen; i++)
            P[i] = P[i] ^ streamtoword(key, koffp);

        for (i = 0; i < plen; i += 2) {
            encipher(lr, 0);
            P[i] = lr[0];
            P[i + 1] = lr[1];
        }

        for (i = 0; i < slen; i += 2) {
            encipher(lr, 0);
            S[i] = lr[0];
            S[i + 1] = lr[1];
        }
    }

    /**
     * Perform the "enhanced key schedule" step described by
     * Provos and Mazieres in "A Future-Adaptable Password Scheme"
     * http://www.openbsd.org/papers/bcrypt-paper.ps
     * @param data  salt information
     * @param key   password information
     */
    private void ekskey(byte data[], byte key[]) {
        int i;
        int koffp[] = { 0 }, doffp[] = { 0 };
        int lr[] = { 0, 0 };
        int plen = P.length, slen = S.length;

        for (i = 0; i < plen; i++)
            P[i] = P[i] ^ streamtoword(key, koffp);

        for (i = 0; i < plen; i += 2) {
            lr[0] ^= streamtoword(data, doffp);
            lr[1] ^= streamtoword(data, doffp);
            encipher(lr, 0);
            P[i] = lr[0];
            P[i + 1] = lr[1];
        }

        for (i = 0; i < slen; i += 2) {
            lr[0] ^= streamtoword(data, doffp);
            lr[1] ^= streamtoword(data, doffp);
            encipher(lr, 0);
            S[i] = lr[0];
            S[i + 1] = lr[1];
        }
    }

    /**
     * Perform the central password hashing step in the
     * bcrypt scheme
     * @param password      the password to hash
     * @param salt          the binary salt to hash with the password
     * @param log_rounds    the binary logarithm of the number
     *                      of rounds of hashing to apply
     * @param cdata         the plaintext to encrypt
     * @return  an array containing the binary hashed password
     */
    public byte[] crypt_raw(byte password[], byte salt[], int log_rounds,
        int cdata[]) {
        int rounds, i, j;
        int clen = cdata.length;
        byte ret[];

        if (log_rounds < 4 || log_rounds > 30)
            throw new IllegalArgumentException ("Bad number of rounds");
        rounds = 1 << log_rounds;
        if (salt.length != BCRYPT_SALT_LEN)
            throw new IllegalArgumentException ("Bad salt length");

        init_key();
        ekskey(salt, password);
        for (i = 0; i != rounds; i++) {
            key(password);
            key(salt);
        }

        for (i = 0; i < 64; i++) {
            for (j = 0; j < (clen >> 1); j++)
                encipher(cdata, j << 1);
        }

        ret = new byte[clen * 4];
        for (i = 0, j = 0; i < clen; i++) {
            ret[j++] = (byte)((cdata[i] >> 24) & 0xff);
            ret[j++] = (byte)((cdata[i] >> 16) & 0xff);
            ret[j++] = (byte)((cdata[i] >> 8) & 0xff);
            ret[j++] = (byte)(cdata[i] & 0xff);
        }
        return ret;
    }

    /**
     * Hash a password using the OpenBSD bcrypt scheme.
     *
     * Modified from the original to take a SecureString instead of the original
     *
     * @param password  the password to hash
     * @param salt      the salt to hash with (perhaps generated
     *                  using BCrypt.gensalt)
     * @return          the hashed password
     */
    public static String hashpw(SecureString password, String salt) {
        BCrypt B;
        String real_salt;
        byte passwordb[], saltb[], hashed[];
        char minor = (char)0;
        int rounds, off = 0;
        StringBuffer rs = new StringBuffer();

        if (salt.charAt(0) != '$' || salt.charAt(1) != '2')
            throw new IllegalArgumentException ("Invalid salt version");
        if (salt.charAt(2) == '$')
            off = 3;
        else {
            minor = salt.charAt(2);
            if (minor != 'a' || salt.charAt(3) != '$')
                throw new IllegalArgumentException ("Invalid salt revision");
            off = 4;
        }

        // Extract number of rounds
        if (salt.charAt(off + 2) > '$')
            throw new IllegalArgumentException ("Missing salt rounds");
        rounds = Integer.parseInt(salt.substring(off, off + 2));

        real_salt = salt.substring(off + 3, off + 25);

        /*************************** ES CHANGE START *************************/
        /* original code before introducing SecureString
        try {
          passwordb = (password + (minor >= 'a' ? "\000" : "")).getBytes("UTF-8");
        } catch (UnsupportedEncodingException uee) {
          throw new AssertionError("UTF-8 is not supported");
        }

         */

        // the next lines are the SecureString replacement for the above commented-out section
        if (minor >= 'a') {
            try (SecureString secureString = new SecureString(CharArrays.concat(password.getChars(), "\000".toCharArray()))) {
                passwordb = CharArrays.toUtf8Bytes(secureString.getChars());
            }
        } else {
            passwordb = CharArrays.toUtf8Bytes(password.getChars());
        }
        /*************************** ES CHANGE END *************************/

        saltb = decode_base64(real_salt, BCRYPT_SALT_LEN);

        B = new BCrypt();
        hashed = B.crypt_raw(passwordb, saltb, rounds,
            bf_crypt_ciphertext.clone());

        rs.append("$2");
        if (minor >= 'a')
            rs.append(minor);
        rs.append("$");
        if (rounds < 10)
            rs.append("0");
        if (rounds > 30) {
            throw new IllegalArgumentException(
                    "rounds exceeds maximum (30)");
        }
        rs.append(Integer.toString(rounds));
        rs.append("$");
        rs.append(encode_base64(saltb, saltb.length));
        rs.append(encode_base64(hashed,
                bf_crypt_ciphertext.length * 4 - 1));
        return rs.toString();
    }

    /**
     * Generate a salt for use with the BCrypt.hashpw() method
     * @param log_rounds  the log2 of the number of rounds of
     *                    hashing to apply - the work factor therefore increases as
     *                    2**log_rounds.
     * @param random      an instance of SecureRandom to use
     * @return            an encoded salt value
     */
    public static String gensalt(int log_rounds, SecureRandom random) {
        StringBuffer rs = new StringBuffer();
        byte rnd[] = new byte[BCRYPT_SALT_LEN];

        random.nextBytes(rnd);

        rs.append("$2a$");
        if (log_rounds < 10)
            rs.append("0");
        if (log_rounds > 30) {
            throw new IllegalArgumentException(
                    "log_rounds exceeds maximum (30)");
        }
        rs.append(Integer.toString(log_rounds));
        rs.append("$");
        rs.append(encode_base64(rnd, rnd.length));
        return rs.toString();
    }

    /**
     * Generate a salt for use with the BCrypt.hashpw() method
     * @param log_rounds  the log2 of the number of rounds of
     *                    hashing to apply - the work factor therefore increases as
     *                    2**log_rounds.
     * @return            an encoded salt value
     */
    public static String gensalt(int log_rounds) {
        return gensalt(log_rounds, new SecureRandom());
    }

    /**
     * Generate a salt for use with the BCrypt.hashpw() method,
     * selecting a reasonable default for the number of hashing
     * rounds to apply
     * @return  an encoded salt value
     */
    public static String gensalt() {
        return gensalt(GENSALT_DEFAULT_LOG2_ROUNDS);
    }

    /**
     * Check that a plaintext password matches a previously hashed
     * one.
     *
     * Modified from the original to take a SecureString plaintext and use a constant time comparison
     * @param plaintext  the plaintext password to verify
     * @param hashed     the previously-hashed password
     * @return           true if the passwords match, false otherwise
     */
    public static boolean checkpw(SecureString plaintext, String hashed) {
        /*************************** ES CHANGE START *************************/
        // this method previously took a string and did its own constant time comparison
        return CharArrays.constantTimeEquals(hashed, hashpw(plaintext, hashed));
        /*************************** ES CHANGE END *************************/
    }
}
