我想知道这个功能（部分取自大约 2 岁的 phpBB 版本）是否足够好。
如果不是，为什么？
你将如何改变它（使现有用户无缝过渡）？
hash_pwd() 的结果将保存在数据库中。
function hash_pwd($password)
{
$itoa64 = './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
$random_state = $this->unique_id();
$random = '';
$count = 6;
if (($fh = @fopen('/dev/urandom', 'rb')))
{
$random = fread($fh, $count);
fclose($fh);
}
if (strlen($random) < $count)
{
$random = '';
for ($i = 0; $i < $count; $i += 16)
{
$random_state = md5($this->unique_id() . $random_state);
$random .= pack('H*', md5($random_state));
}
$random = substr($random, 0, $count);
}
$hash = $this->_hash_crypt_private($password, $this->_hash_gensalt_private($random, $itoa64), $itoa64);
if (strlen($hash) == 34)
{
return $hash;
}
return false;
}
function unique_id()
{
$val = microtime();
$val = md5($val);
return substr($val, 4, 16);
}
function _hash_crypt_private($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 .= $this->_hash_encode64($hash, 16, $itoa64);
return $output;
}
function _hash_gensalt_private($input, &$itoa64, $iteration_count_log2 = 6)
{
if ($iteration_count_log2 < 4 || $iteration_count_log2 > 31)
{
$iteration_count_log2 = 8;
}
$output = '$H$';
$output .= $itoa64[min($iteration_count_log2 + ((PHP_VERSION >= 5) ? 5 : 3), 30)];
$output .= $this->_hash_encode64($input, 6, $itoa64);
return $output;
}
function _hash_encode64($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;
}