socialbox-php/src/Socialbox/Classes/OtpCryptography.php

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<?php
namespace Socialbox\Classes;
use Random\RandomException;
use Socialbox\Exceptions\CryptographyException;
class OtpCryptography
{
/**
* Generates a random secret key of the specified length.
*
* @param int $length The length of the secret key in bytes. Default is 32.
* @return string Returns the generated secret key as a hexadecimal string.
* @throws CryptographyException
* @throws RandomException
*/
public static function generateSecretKey(int $length = 32): string
{
if($length <= 0)
{
throw new CryptographyException("Invalid secret key length: must be greater than 0.");
}
return bin2hex(random_bytes($length));
}
/**
* Generates a one-time password (OTP) based on the provided parameters.
*
* @param string $secretKey The secret key used to generate the OTP.
* @param int $timeStep The time step in seconds used for OTP generation. Default is 30 seconds.
* @param int $digits The number of digits in the OTP. Default is 6.
* @param int|null $counter Optional counter value. If not provided, it is calculated based on the current time and time step.
* @param string $hashAlgorithm The hash algorithm used for OTP generation. Default is 'sha1'.
* @return string Returns the generated OTP as a string with the specified number of digits.
* @throws CryptographyException If the generated hash length is less than 20 bytes.
*/
public static function generateOTP(string $secretKey, int $timeStep=30, int $digits=6, int $counter=null, string $hashAlgorithm='sha1'): string
{
if ($counter === null)
{
$counter = floor(time() / $timeStep);
}
$hash = self::hashHmac($hashAlgorithm, pack('J', $counter), $secretKey);
if (strlen($hash) < 20)
{
throw new CryptographyException("Invalid hash length: must be at least 20 bytes.");
}
// Validate the $secretKey
if (!ctype_xdigit($secretKey))
{
throw new CryptographyException("Invalid secret key: must be a hexadecimal string.");
}
$offset = ord($hash[strlen($hash) - 1]) & 0x0F;
$binary = unpack('N', substr($hash, $offset, 4))[1] & 0x7FFFFFFF;
$otp = $binary % (10 ** $digits);
return str_pad((string)$otp, $digits, '0', STR_PAD_LEFT);
}
/**
* Verifies a one-time password (OTP) based on the provided parameters.
*
* @param string $secretKey The secret key used to generate the OTP.
* @param string $otp The one-time password to verify.
* @param int $timeStep The time step in seconds used for OTP generation. Default is 30 seconds.
* @param int $window The allowed window of time steps for verification. Default is 1.
* @param int $digits The number of digits in the OTP. Default is 6.
* @param string $hashAlgorithm The hash algorithm used for OTP generation. Default is 'sha512'.
* @return bool Returns true if the OTP is valid within the provided parameters, otherwise false.
*/
public static function verifyOTP(string $secretKey, string $otp, int $timeStep=30, int $window=1, int $digits=6, string $hashAlgorithm='sha512'): bool
{
$currentTime = time();
$counter = floor($currentTime / $timeStep);
for ($i = -$window; $i <= $window; $i++)
{
$testCounter = $counter + $i;
$expectedOtp = self::generateOTP($secretKey, $timeStep, $digits, $testCounter, $hashAlgorithm);
if (hash_equals($expectedOtp, $otp))
{
return true;
}
}
return false;
}
/**
* Generates a QR code payload for a TOTP-based authentication system.
*
* The method constructs a URI in the format compatible with TOTP applications.
*
* @param string $account The account name or identifier associated with the QR code.
* @param string $secretKey The secret key to be included in the payload.
* @param string $issuer The issuer name to identify the organization or service.
*
* @return string A formatted string representing the QR code payload.
*
* @throws CryptographyException If the domain configuration is missing.
*/
public static function generateQrPayload(string $account, string $secretKey, string $issuer): string
{
$domain = Configuration::getInstanceConfiguration()->getDomain();
if (!$domain)
{
throw new CryptographyException("Domain configuration is missing.");
}
return sprintf("otpauth://totp/%s:%s?secret=%s&issuer=%s", rawurlencode($domain), rawurlencode($account), rawurlencode($secretKey), rawurlencode($issuer));
}
/**
* Computes a hash-based message authentication code (HMAC) using the specified algorithm.
*
* @param string $algorithm The hashing algorithm to be used (e.g., 'sha1', 'sha256', 'sha384', 'sha512').
* @param string $data The data to be hashed.
* @param string $key The secret key used for the HMAC generation.
*
* @return string The generated HMAC as a raw binary string.
*
* @*/
private static function hashHmac(string $algorithm, string $data, string $key): string
{
return match($algorithm)
{
'sha1', 'sha256', 'sha384', 'sha512' => hash_hmac($algorithm, $data, $key, true),
default => throw new CryptographyException('Algorithm not supported')
};
}
}