/**
* PKCS #7 unpadding function.
*
* @param string $input Padded string to unpad
*
* @return string
*/
public static function unpad($input)
{
// Determine the padding size by converting the final byte of the
// input to its decimal value
$padsize = \ord(Str::substr($input, -1));
// Return string minus the padding amount
return Str::substr($input, 0, Str::strlen($input) - $padsize);
}
/**
* This will normalize a hash to a certain length by extending it if
* too short and truncating it if too long. This ensures that any
* hash algo will work with any combination of other settings. However,
* it is probably best to make sure that the keysize and algo size
* are identical so that the input hash passes through unchanged.
*
* @param string $hash Hash to be normalized
* @param int $size Size of the desired output hash, in bytes
* @param string $algo Hashing algorithm to use for internal operations
*
* @return string
*/
private static function hashNormalize($hash, $size, $algo)
{
// Extend hash if too short
while (Str::strlen($hash) < $size) {
$hash .= \hash($algo, $hash, true);
}
// Truncate to specified number of bytes (if needed) and return
return Str::substr($hash, 0, $size);
}
/**
* Create the initial byte matrix that will be used for swaps. This code
* is identical between RC4 and Spritz.
*
* @param string $key
*
* @return array
*/
protected static function initializeState($key)
{
$s = \range(0, 255);
$j = 0;
foreach (\range(0, 255) as $i) {
$j = ($j + $s[$i] + \ord($key[$i % Str::strlen($key)])) % 256;
$x = $s[$i];
$s[$i] = $s[$j];
$s[$j] = $x;
}
return $s;
}
/**
* Perform (en/de)cryption
*
* @param string $str String to be encrypted
* @param string $key Key to use for encryption
*
* @return string
*/
public static function crypt($str, $key)
{
$s = self::initializeState($key);
$i = $j = $k = $z = 0;
$w = 1;
$res = '';
$size = Str::strlen($str);
for ($y = 0; $y < $size; $y++) {
$i = ($i + $w) % 256;
$j = ($k + $s[($j + $s[$i]) % 256]) % 256;
$k = ($i + $k + $s[$j]) % 256;
$x = $s[$i];
$s[$i] = $s[$j];
$s[$j] = $x;
$z = $s[($j + $s[($i + $s[($z + $k) % 256]) % 256]) % 256];
$res .= $str[$y] ^ \chr($z);
}
return $res;
}
