APR1-MD5 encryption method (windows compatible) for Apache .htpasswd

crypt_apr1_md5.php

<?php
// APR1-MD5 encryption method (windows compatible)
// https://gist.github.com/BlaM/f3a9d535963900d1fbddc890c66f3891
//
// 2019-04-09 - https://github.com/BlaM - $salt
// 2022-03-04 - https://github.com/BlaM - fix php7 deprecation warning
// 2023-01-11 - https://github.com/BlaM and https://github.com/alecos71 - prepare for php8 sunset of str_shuffle
function crypt_apr1_md5($plainpasswd, $salt = null) {
    if (empty($salt)) {
        $chars = 'abcdefghijklmnopqrstuvwxyz012345689';
        $length = 8;
        if (function_exists('random_int')) {
            // PHP 7+
            $salt = '';
            for ($i = 0; $i < $length; $i++) {
                $pos = random_int(0, strlen($chars) -1);
                $salt .= substr($chars, $pos, 1);
            }
        } else if (function_exists('str_shuffle')) {
            // PHP 4-8
            $salt = substr(str_shuffle($chars), 0, $length);
        } else {
            throw new Exception('Not implemented');
        }
    } elseif (substr($salt, 0, 6) == '$apr1$') {
        $salt = explode('$', $salt);
        $salt = $salt[2];
    }
    $tmp = "";
    $len = strlen($plainpasswd);
    $text = $plainpasswd . '$apr1$' . $salt;
    $bin = pack("H32", md5($plainpasswd . $salt . $plainpasswd));
    for ($i = $len; $i > 0; $i -= 16) { $text .= substr($bin, 0, min(16, $i)); }
    for ($i = $len; $i > 0; $i >>= 1) { $text .= ($i & 1) ? chr(0) : substr($plainpasswd, 0, 0); }
    $bin = pack("H32", md5($text));
    for ($i = 0; $i < 1000; $i++) {
        $new = ($i & 1) ? $plainpasswd : $bin;
        if ($i % 3) $new .= $salt;
        if ($i % 7) $new .= $plainpasswd;
        $new .= ($i & 1) ? $bin : $plainpasswd;
        $bin = pack("H32", md5($new));
    }
    for ($i = 0; $i < 5; $i++) {
        $k = $i + 6;
        $j = $i + 12;
        if ($j == 16) $j = 5;
        $tmp = $bin[$i].$bin[$k].$bin[$j].$tmp;
    }
    $tmp = chr(0).chr(0).$bin[11].$tmp;
    $tmp = strtr(strrev(substr(base64_encode($tmp), 2)),
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
    "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");

    return "$"."apr1"."$".$salt."$".$tmp;
}

https://wiki.php.net/rfc/deprecations_php_8_3

The following functions will be deprecated in Php 8.3 and removed in Php 9.0.

• mt_rand
• mt_srand
• mt_getrandmax
• rand
• srand
• getrandmax
• array_rand
• shuffle
• str_shuffle

random_int() instead is safe and not deprecated.

str_shuffle is the one inside your script. Please fix it!

Here is my proposal to fix:

  function crypt_apr1_md5($plainpasswd, $salt = null) {
    if (empty($salt)) {
      $chars = 'abcdefghijklmnopqrstuvwxyz012345689';
      $length = 35;
      $random = '';
      for ($i = 0; $i < $length; $i++) {
        $pos = random_int(0, strlen($chars) -1);
        $random .= substr($chars, $pos, 1);
       }
       $salt = substr($random, 0, 8);
       // $salt = substr(str_shuffle("abcdefghijklmnopqrstuvwxyz0123456789"), 0, 8);  /* Deprecated */
    } elseif (substr($salt, 0, 6) == '$apr1$') {
        $salt = explode('$', $salt);
        $salt = $salt[2];
    }
    $tmp = "";
    $len = strlen($plainpasswd);
    $text = $plainpasswd.'$apr1$'.$salt;
    $bin = pack("H32", md5($plainpasswd.$salt.$plainpasswd));
    for ($i = $len; $i > 0; $i -= 16) { $text .= substr($bin, 0, min(16, $i)); }
    for ($i = $len; $i > 0; $i >>= 1) { $text .= ($i & 1) ? chr(0) : substr($plainpasswd, 0, 0); }
    $bin = pack("H32", md5($text));
    for ($i = 0; $i < 1000; $i++) {
        $new = ($i & 1) ? $plainpasswd : $bin;
        if ($i % 3) $new .= $salt;
        if ($i % 7) $new .= $plainpasswd;
        $new .= ($i & 1) ? $bin : $plainpasswd;
        $bin = pack("H32", md5($new));
    }
    for ($i = 0; $i < 5; $i++) {
        $k = $i + 6;
        $j = $i + 12;
        if ($j == 16) $j = 5;
        $tmp = $bin[$i].$bin[$k].$bin[$j].$tmp;
    }
    $tmp = chr(0).chr(0).$bin[11].$tmp;
    $tmp = strtr(strrev(substr(base64_encode($tmp), 2)),
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
    "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
    return "$"."apr1"."$".$salt."$".$tmp;
}

What do you think? Is quite safe?

Thank you for the heads up. Your suggestion is probably even more cryptographically safe than the old str_shuffle approach. I'll base my update on your suggestion, but I'll "optimize" it a bit (there is no need to randomize 35 characters and then throw everything after character 8 away - randomizing just 8 is enough ;) )

Well done!

Please, pay attention to this:

Apache in Windows requires the salt, without fails to authenticate. The rest is OK.