/**
* 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);
}
/**
* Decrypt cyphertext
*
* @param string $cyphertext Cyphertext to decrypt
* @param string $password Password that should be used to decrypt input data
* @param int $cost Number of HMAC iterations to perform on key
*
* @return string
*/
public static function decrypt($cyphertext, $password, $cost = 0)
{
// Find the IV at the beginning of the cypher text
$iv = Str::substr($cyphertext, 0, self::IVSIZE);
// Gather the checksum portion of the cypher text
$chksum = Str::substr($cyphertext, self::IVSIZE, self::CKSIZE);
// Gather message portion of cyphertext after iv and checksum
$message = Str::substr($cyphertext, self::IVSIZE + self::CKSIZE);
// Derive key from password
$key = self::key($password, $iv, $cost, self::RIJNDA, self::mode());
// Calculate verification checksum
$verify = self::checksum($message, $iv, $key, self::RIJNDA, self::mode());
// Verify HMAC before decrypting
self::checksumVerify($verify, $chksum);
// Decrypt message and return
return \openssl_decrypt($message, static::CIPHER, $key, 1, $iv);
}
/**
* Decrypt cyphertext
*
* @param string $cyphertext Cypher text to decrypt
* @param string $password Password that should be used to decrypt input data
* @param int $cost Number of HMAC iterations to perform on key
* @param string $cipher Mcrypt cipher
* @param string $mode Mcrypt mode
* @param string $algo Hashing algorithm to use for internal operations
*
* @return string|boolean Returns false on checksum validation failure
*/
public static function decrypt($cyphertext, $password, $cost = 0, $cipher = MCRYPT_RIJNDAEL_128, $mode = MCRYPT_MODE_CBC, $algo = 'sha256')
{
// Determine that size of the IV in bytes
$ivsize = \mcrypt_get_iv_size($cipher, $mode);
// Find the IV at the beginning of the cypher text
$iv = Str::substr($cyphertext, 0, $ivsize);
// Gather the checksum portion of the cypher text
$chksum = Str::substr($cyphertext, $ivsize, Str::hashSize($algo));
// Gather message portion of cyphertext after iv and checksum
$message = Str::substr($cyphertext, $ivsize + Str::hashSize($algo));
// Derive key from password
$key = self::key($password, $iv, $cost, $cipher, $mode, $algo);
// Calculate verification checksum
$verify = self::checksum($message, $iv, $key, $cipher, $mode, $algo);
// If checksum could not be verified return false
self::checksumVerify($verify, $chksum);
// Decrypt unpad return
return Pkcs7::unpad(\mcrypt_decrypt($cipher, $key, $message, $mode, $iv));
}
/**
* Check the validity of a hash.
*
* @param string $input Input to test.
* @param string $hash Known hash to validate against.
* @param string $password HMAC password to use during iterative hash.
*
* @return boolean
*/
public static function verify($input, $hash, $password)
{
// Get the salt value from the decrypted prefix
$salt = Str::substr($hash, 0, 16);
// Get the encrypted cost bytes
$cost = self::bin2dec(Otp::crypt(Str::substr($hash, 28, 4), $password));
// Get the entire cost+hash blob for comparison
$blob = Str::substr($hash, 16, 16);
if (!Str::equal(self::costHash($cost, $salt, $password), $blob)) {
return false;
}
// Return the boolean equivalence
return Str::equal($hash, self::build($input, $password, $cost, $salt));
}
