PHP Decoding MySQL's .mylogin.cnf

decode.php

<?php // tested with PHP 7.1.7
$start = microtime(true);

const LOGIN_KEY_LEN = 20;
const MY_LOGIN_HEADER_LEN = 24;
const MAX_CIPHER_STORE_LEN = 4;

$raw = file_get_contents(__DIR__ . '/mylogin.cnf');
$fp = 4; // skip null bytes

$b = substr($raw, $fp, LOGIN_KEY_LEN);
$fp = MY_LOGIN_HEADER_LEN;

// extract key
$key = array_pad([], 16, 0);
for ($i = 0; $i < LOGIN_KEY_LEN; $i++) {
    $key[$i % 16] ^= ord($b[$i]);
}
$key = pack('C*', $key[0], $key[1], $key[2], $key[3],
                  $key[4], $key[5], $key[6], $key[7],
                  $key[8], $key[9], $key[10], $key[11],
                  $key[12], $key[13], $key[14], $key[15]);

$settings = [];

while ($fp < strlen($raw)) {
    $b = substr($raw, $fp, MAX_CIPHER_STORE_LEN);
    $fp += MAX_CIPHER_STORE_LEN;
    $cipher_len = unpack('V', $b);
  
    $b = substr($raw, $fp, $cipher_len[1]);
    $fp += $cipher_len[1];  
    $plain = trim(openssl_decrypt($b, 'aes-128-ecb', $key, OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING));

    if (preg_match('/^(\w+) = (.*)/', $plain, $matches)) {
        $settings[$matches[1]] = $matches[2];
    }
}

// in my VM, this took about 1/10th of a millisecond, float(0.00011301040649414)  
$end = microtime(true);
var_dump($end - $start);

var_dump($settings);

Generate the .cnf file using mysql_config_editor and copy to the current folder.