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<?php

/*

 * ViaThinkSoft Modular Crypt Format 1.0 and vts_password_*() functions

 * Copyright 2023 Daniel Marschall, ViaThinkSoft

 * Revision 2023-03-03

 *

 * 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.

 */

/*

The function vts_password_hash() replaces password_hash()

and adds the ViaThinkSoft Modular Crypt Format 1.0 hash as well as

all hashes from password_hash() and crypt().

The function vts_password_verify() replaces password_verify().

ViaThinkSoft Modular Crypt Format 1.0 performs a simple hash or HMAC operation.

No key derivation function or iterations are performed.

Format:

        $1.3.6.1.4.1.37476.3.0.1.1$a=<algo>,m=<mode>[,i=<iterations>]$<salt>$<hash>

where <algo> is any valid hash algorithm (name scheme of PHP hash_algos() preferred), e.g.

        sha3-512

        sha3-384

        sha3-256

        sha3-224

        sha512

        sha512/256

        sha512/224

        sha384

        sha256

        sha224

        sha1

        md5

Not supported are these hashes (because they have a special salt-handling and output their own crypt format):

        bcrypt [Standardized crypt identifier 2, 2a, 2x, 2y]

        argon2i [Crypt identifier argon2i, not standardized]

        argon2id [Crypt identifier argon2i, not standardized]

Valid <mode> :

        sp = salt + password

        ps = password + salt

        sps = salt + password + salt

        hmac = HMAC (salt is the key)

        pbkdf2 = PBKDF2-HMAC (Additional param i= contains the number of iterations)

<iterations> can be omitted if 0. It is required for mode=pbkdf2. For sp/ps/sps/hmac, it is optional.

Like most Crypt-hashes, <salt> and <hash> are Radix64 coded

with alphabet './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz' and no padding.

Link to the online specification:

        https://oidplus.viathinksoft.com/oidplus/?goto=oid%3A1.3.6.1.4.1.37476.3.0.1.1

Reference implementation in PHP:

        https://github.com/danielmarschall/php_utils/blob/master/vts_crypt.inc.php

*/

require_once __DIR__ . '/misc_functions.inc.php';

define('OID_MCF_VTS_V1',     '1.3.6.1.4.1.37476.3.0.1.1'); // { iso(1) identified-organization(3) dod(6) internet(1) private(4) enterprise(1) 37476 specifications(3) misc(0) modular-crypt-format(1) vts-crypt-v1(1) }

// Valid algorithms for vts_password_hash():

define('PASSWORD_STD_DES',   'std-des');       // Algorithm from crypt()

define('PASSWORD_EXT_DES',   'ext-des');       // Algorithm from crypt()

define('PASSWORD_MD5',       'md5');           // Algorithm from crypt()

define('PASSWORD_BLOWFISH',  'blowfish');      // Algorithm from crypt()

define('PASSWORD_SHA256',    'sha256');        // Algorithm from crypt()

define('PASSWORD_SHA512',    'sha512');        // Algorithm from crypt()

define('PASSWORD_VTS_MCF1',  OID_MCF_VTS_V1);  // Algorithm by ViaThinkSoft

// Other valid values (already defined in PHP):

// - PASSWORD_DEFAULT

// - PASSWORD_BCRYPT

// - PASSWORD_ARGON2I

// - PASSWORD_ARGON2ID

define('PASSWORD_VTS_MCF1_MODE_SP',             'sp');     // Salt+Password

define('PASSWORD_VTS_MCF1_MODE_PS',             'ps');     // Password+Salt

define('PASSWORD_VTS_MCF1_MODE_SPS',            'sps');    // Salt+Password+Salt

define('PASSWORD_VTS_MCF1_MODE_HMAC',           'hmac');   // HMAC

define('PASSWORD_VTS_MCF1_MODE_PBKDF2',         'pbkdf2'); // PBKDF2-HMAC

define('PASSWORD_EXT_DES_DEFAULT_ITERATIONS',   725);

define('PASSWORD_BLOWFISH_DEFAULT_COST',        10);

define('PASSWORD_SHA256_DEFAULT_ROUNDS',        5000);

define('PASSWORD_SHA512_DEFAULT_ROUNDS',        5000);

define('PASSWORD_VTS_MCF1_DEFAULT_ALGO',        'sha3-512'); // any value in hash_algos(), NOT vts_hash_algos()

define('PASSWORD_VTS_MCF1_DEFAULT_MODE',        PASSWORD_VTS_MCF1_MODE_PS);

define('PASSWORD_VTS_MCF1_DEFAULT_ITERATIONS',  0); // For PBKDF2, iterations=0 means: Default, depending on the algo

// --- Part 1: Modular Crypt Format encode/decode

function crypt_modular_format_encode($id, $bin_salt, $bin_hash, $params=null) {

        // $<id>[$<param>=<value>(,<param>=<value>)*][$<salt>[$<hash>]]

        $out = '$'.$id;

        if (!is_null($params)) {

                $ary_params = array();

                foreach ($params as $name => $value) {

                        $ary_params[] = "$name=$value";

                }

                $out .= '$'.implode(',',$ary_params);

        }

        $out .= '$'.crypt_radix64_encode($bin_salt);

        $out .= '$'.crypt_radix64_encode($bin_hash);

        return $out;

}

function crypt_modular_format_decode($mcf) {

        $ary = explode('$', $mcf);

        $dummy = array_shift($ary);

        if ($dummy !== '') return false;

        $dummy = array_shift($ary);

        $id = $dummy;

        $params = array();

        $dummy = array_shift($ary);

        if (strpos($dummy, '=') !== false) {

                $params_ary = explode(',',$dummy);

                foreach ($params_ary as $param) {

                        $bry = explode('=', $param, 2);

                        if (count($bry) > 1) {

                                $params[$bry[0]] = $bry[1];

                        }

                }

        } else {

                array_unshift($ary, $dummy);

        }

        if (count($ary) > 1) {

                $dummy = array_shift($ary);

                $bin_salt = crypt_radix64_decode($dummy);

        } else {

                $bin_salt = '';

        }

        $dummy = array_shift($ary);

        $bin_hash = crypt_radix64_decode($dummy);

        return array('id'     => $id,

                     'salt'   => $bin_salt,

                     'hash'   => $bin_hash,

                     'params' => $params);

}

// --- Part 2: ViaThinkSoft Modular Crypt Format 1.0

function vts_crypt_version($hash) {

        if (str_starts_with($hash, '$'.OID_MCF_VTS_V1.'$')) {

                return '1';

        } else {

                return '0';

        }

}

function vts_crypt_hash($algo, $str_password, $str_salt, $ver='1', $mode=PASSWORD_VTS_MCF1_DEFAULT_MODE, $iterations=PASSWORD_VTS_MCF1_DEFAULT_ITERATIONS) {

        if ($ver == '1') {

                if ($mode == PASSWORD_VTS_MCF1_MODE_SP) {

                        $bin_hash = hash_ex($algo, $str_salt.$str_password, true);

                        for ($i=0; $i<$iterations; $i++) {

                                $bin_hash = hash_ex($algo, $str_salt.$bin_hash.$i, true);

                        }

                } else if ($mode == PASSWORD_VTS_MCF1_MODE_PS) {

                        $bin_hash = hash_ex($algo, $str_password.$str_salt, true);

                        for ($i=0; $i<$iterations; $i++) {

                                $bin_hash = hash_ex($algo, $bin_hash.$i.$str_salt, true);

                        }

                } else if ($mode == PASSWORD_VTS_MCF1_MODE_SPS) {

                        $bin_hash = hash_ex($algo, $str_salt.$str_password.$str_salt, true);

                        for ($i=0; $i<$iterations; $i++) {

                                $bin_hash = hash_ex($algo, $str_salt.$bin_hash.$i.$str_salt, true);

                        }

                } else if ($mode == PASSWORD_VTS_MCF1_MODE_HMAC) {

                        $bin_hash = hash_hmac_ex($algo, $str_password, $str_salt, true);

                        for ($i=0; $i<$iterations; $i++) {

                                // https://security.stackexchange.com/questions/149299/rounds-in-a-hashing-function

                                $bin_hash = hash_hmac_ex($algo, $str_password, $bin_hash.$i, true);

                        }

                } else if ($mode == PASSWORD_VTS_MCF1_MODE_PBKDF2) {

                        // Note: If $iterations=0, then hash_pbkdf2_ex() will correct it to the best value depending on $algo, see _vts_password_default_iterations().

                        $bin_hash = hash_pbkdf2_ex($algo, $str_password, $str_salt, $iterations, 0, true);

                } else {

                        throw new Exception("Invalid VTS crypt version 1 mode. Expect sp, ps, sps, hmac, or pbkdf2.");

                }

                $bin_salt = $str_salt;

                $params = array();

                $params['a'] = $algo;

                $params['m'] = $mode;

                if ($iterations != 0) $params['i'] = $iterations; // i can be omitted if it is 0.

                return crypt_modular_format_encode(OID_MCF_VTS_V1, $bin_salt, $bin_hash, $params);

        } else {

                throw new Exception("Invalid VTS crypt version, expect 1.");

        }

}

function vts_crypt_verify($password, $hash): bool {

        $ver = vts_crypt_version($hash);

        if ($ver == '1') {

                // Decode the MCF hash parameters

                $data = crypt_modular_format_decode($hash);

                if ($data === false) throw new Exception('Invalid auth key');

                $id = $data['id'];

                $bin_salt = $data['salt'];

                $bin_hash = $data['hash'];

                $params = $data['params'];

                if (!isset($params['a'])) throw new Exception('Param "a" (algo) missing');

                $algo = $params['a'];

                if (!isset($params['m'])) throw new Exception('Param "m" (mode) missing');

                $mode = $params['m'];

                if ($mode == PASSWORD_VTS_MCF1_MODE_PBKDF2) {

                        if (!isset($params['i'])) throw new Exception('Param "i" (iterations) missing');

                        $iterations = $params['i'];

                } else {

                        $iterations = isset($params['i']) ? $params['i'] : 0;

                }

                // Create a VTS MCF 1.0 hash based on the parameters of $hash and the password $password

                $calc_authkey_1 = vts_crypt_hash($algo, $password, $bin_salt, $ver, $mode, $iterations);

                // We rewrite the MCF to make sure that they match (if params have the wrong order)

                $calc_authkey_2 = crypt_modular_format_encode($id, $bin_salt, $bin_hash, $params);

                return hash_equals($calc_authkey_1, $calc_authkey_2);

        } else {

                throw new Exception("Invalid VTS crypt version, expect 1.");

        }

}

// --- Part 3: Replacement of vts_password_*() functions

/**

 * This function replaces password_algos() by extending it with

 * password hashes that are implemented in vts_password_hash().

 * @return array of hashes that can be used in vts_password_hash().

 */

function vts_password_algos() {

        $hashes = password_algos();

        $hashes[] = PASSWORD_STD_DES;   // Algorithm from crypt()

        $hashes[] = PASSWORD_EXT_DES;   // Algorithm from crypt()

        $hashes[] = PASSWORD_MD5;       // Algorithm from crypt()

        $hashes[] = PASSWORD_BLOWFISH;  // Algorithm from crypt()

        $hashes[] = PASSWORD_SHA256;    // Algorithm from crypt()

        $hashes[] = PASSWORD_SHA512;    // Algorithm from crypt()

        $hashes[] = PASSWORD_VTS_MCF1;  // Algorithm by ViaThinkSoft

        return $hashes;

}

/** vts_password_get_info() is the same as password_get_info(),

 * but it adds the crypt() and ViaThinkSoft MCF 1.0 algos which can be

 * produced by vts_password_hash()

 * @param string $hash Hash created by vts_password_hash(), password_hash(), or crypt().

 * @return array Same output like password_get_info().

 */

function vts_password_get_info($hash) {

        if (vts_crypt_version($hash) == '1') {

                // OID_MCF_VTS_V1

                $mcf = crypt_modular_format_decode($hash);

                //$options['salt_length'] = strlen($mcf['salt']);  // Note: salt_length is not an MCF option! It's just a hint for vts_password_hash()

                if (!isset($mcf['params']['a'])) throw new Exception('Param "a" (algo) missing');

                $options['algo'] = $mcf['params']['a'];

                if (!isset($mcf['params']['m'])) throw new Exception('Param "m" (mode) missing');

                $options['mode'] = $mcf['params']['m'];

                if ($options['mode'] == PASSWORD_VTS_MCF1_MODE_PBKDF2) {

                        if (!isset($mcf['params']['i'])) throw new Exception('Param "i" (iterations) missing');

                        $options['iterations'] = (int)$mcf['params']['i'];

                } else {

                        $options['iterations'] = isset($mcf['params']['i']) ? (int)$mcf['params']['i'] : 0;

                }

                return array(

                        "algo" => PASSWORD_VTS_MCF1,

                        "algoName" => "vts-mcf-v1",

                        "options" => $options

                );

        } else if (!str_starts_with($hash, '$') && (strlen($hash) == 13)) {

                // PASSWORD_STD_DES

                return array(

                        "algo" => PASSWORD_STD_DES,

                        "algoName" => "std-des",

                        "options" => array(

                                // None

                        )

                );

        } else if (str_starts_with($hash, '_') && (strlen($hash) == 20)) {

                // PASSWORD_EXT_DES

                return array(

                        "algo" => PASSWORD_EXT_DES,

                        "algoName" => "ext-des",

                        "options" => array(

                                "iterations" => (int)base64_int_decode(substr($hash,1,4))

                        )

                );

        } else if (str_starts_with($hash, '$1$')) {

                // PASSWORD_MD5

                return array(

                        "algo" => PASSWORD_MD5,

                        "algoName" => "md5",

                        "options" => array(

                                // None

                        )

                );

        } else if (str_starts_with($hash, '$2$')  || str_starts_with($hash, '$2a$') ||

                   str_starts_with($hash, '$2x$') || str_starts_with($hash, '$2y$')) {

                // PASSWORD_BLOWFISH

                return array(

                        "algo" => PASSWORD_BLOWFISH,

                        "algoName" => "blowfish",

                        "options" => array(

                                "cost" => (int)ltrim(explode('$',$hash)[2],'0')

                        )

                );

        } else if (str_starts_with($hash, '$5$')) {

                // PASSWORD_SHA256

                return array(

                        "algo" => PASSWORD_SHA256,

                        "algoName" => "sha256",

                        "options" => array(

                                'rounds' => (int)str_replace('rounds=','',explode('$',$hash)[2])

                        )

                );

        } else if (str_starts_with($hash, '$6$')) {

                // PASSWORD_SHA512

                return array(

                        "algo" => PASSWORD_SHA512,

                        "algoName" => "sha512",

                        "options" => array(

                                'rounds' => (int)str_replace('rounds=','',explode('$',$hash)[2])

                        )

                );

        } else {

                // PASSWORD_DEFAULT

                // PASSWORD_BCRYPT

                // PASSWORD_ARGON2I

                // PASSWORD_ARGON2ID

                return password_get_info($hash);

        }

}

/** This function extends password_hash() with the algorithms supported by crypt().

 * It also adds vts_crypt_hash() which implements the ViaThinkSoft Modular Crypt Format 1.0.

 * The result can be verified using vts_password_verify().

 * @param string $password to be hashed

 * @param mixed $algo algorithm

 * @param array $options options for the hashing algorithm

 * @return string Crypt style password hash

 */

function vts_password_hash($password, $algo, $options=array()): string {

        $options = vts_password_fill_default_options($algo, $options);

        $crypt_salt = null;

        if (($algo === PASSWORD_STD_DES) && defined('CRYPT_STD_DES')) {

                // Standard DES-based hash with a two character salt from the alphabet "./0-9A-Za-z". Using invalid characters in the salt will cause crypt() to fail.

                $crypt_salt = des_compat_salt(2);

        } else if (($algo === PASSWORD_EXT_DES) && defined('CRYPT_EXT_DES')) {

                // Extended DES-based hash. The "salt" is a 9-character string consisting of an underscore followed by 4 characters of iteration count and 4 characters of salt. Each of these 4-character strings encode 24 bits, least significant character first. The values 0 to 63 are encoded as ./0-9A-Za-z. Using invalid characters in the salt will cause crypt() to fail.

                $iterations = $options['iterations'];

                $crypt_salt = '_' . base64_int_encode($iterations,4) . des_compat_salt(4);

        } else if (($algo === PASSWORD_MD5) && defined('CRYPT_MD5')) {

                // MD5 hashing with a twelve character salt starting with $1$

                $crypt_salt = '$1$'.des_compat_salt(12).'$';

        } else if (($algo === PASSWORD_BLOWFISH) && defined('CRYPT_BLOWFISH')) {

                // Blowfish hashing with a salt as follows: "$2a$", "$2x$" or "$2y$", a two digit cost parameter, "$", and 22 characters from the alphabet "./0-9A-Za-z". Using characters outside of this range in the salt will cause crypt() to return a zero-length string. The two digit cost parameter is the base-2 logarithm of the iteration count for the underlying Blowfish-based hashing algorithm and must be in range 04-31, values outside this range will cause crypt() to fail. "$2x$" hashes are potentially weak; "$2a$" hashes are compatible and mitigate this weakness. For new hashes, "$2y$" should be used.

                $algo = '$2y$'; // most secure

                $cost = $options['cost'];

                $crypt_salt = $algo.str_pad($cost,2,'0',STR_PAD_LEFT).'$'.des_compat_salt(22).'$';

        } else if (($algo === PASSWORD_SHA256) && defined('CRYPT_SHA256')) {

                // SHA-256 hash with a sixteen character salt prefixed with $5$. If the salt string starts with 'rounds=<N>$', the numeric value of N is used to indicate how many times the hashing loop should be executed, much like the cost parameter on Blowfish. The default number of rounds is 5000, there is a minimum of 1000 and a maximum of 999,999,999. Any selection of N outside this range will be truncated to the nearest limit.

                $algo = '$5$';

                $rounds = $options['rounds'];

                $crypt_salt = $algo.'rounds='.$rounds.'$'.des_compat_salt(16).'$';

        } else if (($algo === PASSWORD_SHA512) && defined('CRYPT_SHA512')) {

                // SHA-512 hash with a sixteen character salt prefixed with $6$. If the salt string starts with 'rounds=<N>$', the numeric value of N is used to indicate how many times the hashing loop should be executed, much like the cost parameter on Blowfish. The default number of rounds is 5000, there is a minimum of 1000 and a maximum of 999,999,999. Any selection of N outside this range will be truncated to the nearest limit.

                $algo = '$6$';

                $rounds = $options['rounds'];

                $crypt_salt = $algo.'rounds='.$rounds.'$'.des_compat_salt(16).'$';

        }

        if (!is_null($crypt_salt)) {

                // Algorithms: PASSWORD_STD_DES

                //             PASSWORD_EXT_DES

                //             PASSWORD_MD5

                //             PASSWORD_BLOWFISH

                //             PASSWORD_SHA256

                //             PASSWORD_SHA512

                $out = crypt($password, $crypt_salt);

                if (strlen($out) < 13) throw new Exception("crypt() failed");

                return $out;

        } else if ($algo === PASSWORD_VTS_MCF1) {

                // Algorithms: PASSWORD_VTS_MCF1

                $ver  = '1';

                $algo = $options['algo'];

                $mode = $options['mode'];

                $iterations = $options['iterations'];

                $salt_len = isset($options['salt_length']) ? $options['salt_length'] : 32; // Note: salt_length is not an MCF option! It's just a hint for vts_password_hash()

                $salt = random_bytes_ex($salt_len, true, true);

                return vts_crypt_hash($algo, $password, $salt, $ver, $mode, $iterations);

        } else {

                // Algorithms: PASSWORD_DEFAULT

                //             PASSWORD_BCRYPT

                //             PASSWORD_ARGON2I

                //             PASSWORD_ARGON2ID

                return password_hash($password, $algo, $options);

        }

}

/** This function replaces password_needs_rehash() by adding additional algorithms

 * supported by vts_password_hash().

 * @param string $hash The current hash

 * @param string|int|null $algo Desired new default algo

 * @param array $options Desired new default options

 * @return bool True if algo or options of the current hash don't match the current desired values ($algo and $options), otherwise false.

 */

function vts_password_needs_rehash($hash, $algo, $options=array()) {

        $options = vts_password_fill_default_options($algo, $options);

        $info = vts_password_get_info($hash);

        $algo2 = $info['algo'];

        $options2 = $info['options'];

        // Check if algorithm matches

        if ($algo !== $algo2) return true;

        if (vts_crypt_version($hash) == '1') {

                if (isset($options['salt_length'])) {

                        // For VTS MCF 1.0, salt_length is a valid option for vts_password_hash(),

                        // but it is not a valid option inside the MCF options

                        // and it is not a valid option for vts_password_get_info().

                        unset($options['salt_length']);

                }

                // For PBKDF2, iterations=0 means: Default, depending on the algo

                if (($options['iterations'] == 0/*default*/) && ($options2['mode'] == PASSWORD_VTS_MCF1_MODE_PBKDF2)) {

                        $algo = $options2['algo'];

                        $userland = !hash_pbkdf2_supported_natively($algo) && str_starts_with($algo, 'sha3-') && method_exists('\bb\Sha3\Sha3', 'hash_pbkdf2');

                        $options['iterations'] = _vts_password_default_iterations($algo, $userland);

                }

        }

        // Check if options match

        if (count($options) !== count($options2)) return true;

        foreach ($options as $name => $val) {

                if ($options2[$name] != $val) return true;

        }

        return false;

}

/** This function extends password_verify() by adding ViaThinkSoft Modular Crypt Format 1.0.

 * @param string $password to be checked

 * @param string $hash Hash created by crypt(), password_hash(), or vts_password_hash().

 * @return bool true if password is valid

 */

function vts_password_verify($password, $hash): bool {

        if (vts_crypt_version($hash) != '0') {

                // Hash created by vts_password_hash(), or vts_crypt_hash()

                return vts_crypt_verify($password, $hash);

        } else {

                // Hash created by vts_password_hash(), password_hash(), or crypt()

                return password_verify($password, $hash);

        }

}

// --- Part 4: Functions which include a fallback to a pure-PHP sha3 implementation (requires https://github.com/danielmarschall/php-sha3 )

function hash_ex($algo, $data, $binary=false, $options=array()) {

        if (!hash_supported_natively($algo) && str_starts_with($algo, 'sha3-') && method_exists('\bb\Sha3\Sha3', 'hash')) {

                $bits = (int)explode('-',$algo)[1];

                $hash = \bb\Sha3\Sha3::hash($data, $bits, $binary);

        } else {

                $hash = hash($algo, $data, $binary);

        }

        return $hash;

}

function hash_hmac_ex($algo, $data, $key, $binary=false) {

        if (!hash_hmac_supported_natively($algo) && str_starts_with($algo, 'sha3-') && method_exists('\bb\Sha3\Sha3', 'hash_hmac')) {

                $bits = (int)explode('-',$algo)[1];

                $hash = \bb\Sha3\Sha3::hash_hmac($data, $key, $bits, $binary);

        } else {

                $hash = hash_hmac($algo, $data, $key, $binary);

        }

        return $hash;

}

function hash_pbkdf2_ex($algo, $password, $salt, &$iterations=0, $length=0, $binary=false) {

        if (!hash_pbkdf2_supported_natively($algo) && str_starts_with($algo, 'sha3-') && method_exists('\bb\Sha3\Sha3', 'hash_pbkdf2')) {

                if ($iterations == 0/*default*/) {

                        $iterations = _vts_password_default_iterations($algo, true);

                }

                $bits = (int)explode('-',$algo)[1];

                $hash = \bb\Sha3\Sha3::hash_pbkdf2($password, $salt, $iterations, $bits, $length, $binary);

        } else {

                if ($iterations == 0/*default*/) {

                        $iterations = _vts_password_default_iterations($algo, false);

                }

                $hash = hash_pbkdf2($algo, $password, $salt, $iterations, $length, $binary);

        }

        return $hash;

}

// --- Part 5: Useful functions required by the crypt-functions

define('BASE64_RFC4648_ALPHABET', '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/');

define('BASE64_CRYPT_ALPHABET',   './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz');

function des_compat_salt($salt_len) {

        if ($salt_len <= 0) return '';

        $characters = BASE64_CRYPT_ALPHABET;

        $salt = '';

        $bytes = random_bytes_ex($salt_len, true, true);

        for ($i=0; $i<$salt_len; $i++) {

                $salt .= $characters[ord($bytes[$i]) % strlen($characters)];

        }

        return $salt;

}

function base64_int_encode($num, $len) {

        // https://stackoverflow.com/questions/15534982/which-iteration-rules-apply-on-crypt-using-crypt-ext-des

        $alphabet_raw = BASE64_CRYPT_ALPHABET;

        $alphabet = str_split($alphabet_raw);

        $arr = array();

        $base = sizeof($alphabet);

        while ($num) {

                $rem = $num % $base;

                $num = (int)($num / $base);

                $arr[] = $alphabet[$rem];

        }

        $string = implode($arr);

        return str_pad($string, $len, '.', STR_PAD_RIGHT);

}

function base64_int_decode($base64) {

        $num = 0;

        for ($i=strlen($base64)-1;$i>=0;$i--) {

                $num += strpos(BASE64_CRYPT_ALPHABET, $base64[$i])*pow(strlen(BASE64_CRYPT_ALPHABET),$i);

        }

        return $num;

}

function crypt_radix64_encode($str) {

        $x = $str;

        $x = base64_encode($x);

        $x = rtrim($x, '='); // remove padding

        $x = strtr($x, BASE64_RFC4648_ALPHABET, BASE64_CRYPT_ALPHABET);

        return $x;

}

function crypt_radix64_decode($str) {

        $x = $str;

        $x = strtr($x, BASE64_CRYPT_ALPHABET, BASE64_RFC4648_ALPHABET);

        $x = base64_decode($x);

        return $x;

}

function hash_supported_natively($algo) {

        if (version_compare(PHP_VERSION, '5.1.2') >= 0) {

                return in_array($algo, hash_algos());

        } else {

                return false;

        }

}

function hash_hmac_supported_natively($algo): bool {

        if (version_compare(PHP_VERSION, '7.2.0') >= 0) {

                return in_array($algo, hash_hmac_algos());

        } else if (version_compare(PHP_VERSION, '5.1.2') >= 0) {

                return in_array($algo, hash_algos());

        } else {

                return false;

        }

}

function hash_pbkdf2_supported_natively($algo) {

        return hash_supported_natively($algo);

}

function vts_password_fill_default_options($algo, $options) {

        if ($algo === PASSWORD_STD_DES) {

                // No options

        } else if ($algo === PASSWORD_EXT_DES) {

                if (!isset($options['iterations'])) {

                        $options['iterations'] = PASSWORD_EXT_DES_DEFAULT_ITERATIONS;

                }

        } else if ($algo === PASSWORD_MD5) {

                // No options

        } else if ($algo === PASSWORD_BLOWFISH) {

                if (!isset($options['cost'])) {

                        $options['cost'] = PASSWORD_BLOWFISH_DEFAULT_COST;

                }

        } else if ($algo === PASSWORD_SHA256) {

                if (!isset($options['rounds'])) {

                        $options['rounds'] = PASSWORD_SHA256_DEFAULT_ROUNDS;

                }

        } else if ($algo === PASSWORD_SHA512) {

                if (!isset($options['rounds'])) {

                        $options['rounds'] = PASSWORD_SHA512_DEFAULT_ROUNDS;

                }

        } else if ($algo === PASSWORD_VTS_MCF1) {

                if (!isset($options['algo'])) {

                        $options['algo'] = PASSWORD_VTS_MCF1_DEFAULT_ALGO;

                }

                if (!isset($options['mode'])) {

                        $options['mode'] = PASSWORD_VTS_MCF1_DEFAULT_MODE;

                }

                if ($options['mode'] == PASSWORD_VTS_MCF1_MODE_PBKDF2) {

                        if (!isset($options['iterations'])) {

                                $options['iterations'] = PASSWORD_VTS_MCF1_DEFAULT_ITERATIONS;

                        }

                } else {

                        $options['iterations'] = isset($options['iterations']) ? $options['iterations'] : 0;

                }

        }

        return $options;

}