<?php
# Functions copied from phpbb's functions.php

function crypt_private($pasw, $hash) {
  $itoa64 = './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  return _hash_crypt_private($pasw, $hash, $itoa64);
}


/**
* Encode hash
*/
function _hash_encode64($input, $count, &$itoa64)
{
  $output = '';
  $i = 0;

  do
  {
    $value = ord($input[$i++]);
    $output .= $itoa64[$value & 0x3f];

    if ($i < $count)
    {
      $value |= ord($input[$i]) << 8;
    }

    $output .= $itoa64[($value >> 6) & 0x3f];

    if ($i++ >= $count)
    {
      break;
    }

    if ($i < $count)
    {
      $value |= ord($input[$i]) << 16;
    }

    $output .= $itoa64[($value >> 12) & 0x3f];

    if ($i++ >= $count)
    {
      break;
    }

    $output .= $itoa64[($value >> 18) & 0x3f];
  }
  while ($i < $count);

  return $output;
}

/**
* The crypt function/replacement
*/
function _hash_crypt_private($password, $setting, &$itoa64)
{
  $output = '*';

  // Check for correct hash
  if (substr($setting, 0, 3) != '$H$')
  {
    return $output;
  }

  $count_log2 = strpos($itoa64, $setting[3]);

  if ($count_log2 < 7 || $count_log2 > 30)
  {
    return $output;
  }

  $count = 1 << $count_log2;
  $salt = substr($setting, 4, 8);

  if (strlen($salt) != 8)
  {
    return $output;
  }

  /**
  * We're kind of forced to use MD5 here since it's the only
  * cryptographic primitive available in all versions of PHP
  * currently in use.  To implement our own low-level crypto
  * in PHP would result in much worse performance and
  * consequently in lower iteration counts and hashes that are
  * quicker to crack (by non-PHP code).
  */
  if (PHP_VERSION >= 5)
  {
    $hash = md5($salt . $password, true);
    do
    {
      $hash = md5($hash . $password, true);
    }
    while (--$count);
  }
  else
  {
    $hash = pack('H*', md5($salt . $password));
    do
    {
      $hash = pack('H*', md5($hash . $password));
    }
    while (--$count);
  }

  $output = substr($setting, 0, 12);
  $output .= _hash_encode64($hash, 16, $itoa64);

  return $output;
}