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<?php |
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declare(strict_types=1); |
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/** |
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* This file is part of the Linna Csrf Guard. |
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* |
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* @author Sebastian Rapetti <[email protected]> |
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* @copyright (c) 2020, Sebastian Rapetti |
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* @license http://opensource.org/licenses/MIT MIT License |
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*/ |
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namespace Linna\CsrfGuard\Provider; |
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use Linna\CsrfGuard\Exception\BadExpireException; |
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use Linna\CsrfGuard\Exception\BadExpireTrait; |
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/** |
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* Csrf HMAC Based Token Pattern Provider. |
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* |
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* <p>It uses hash_hmac with sha3-384 algorithm and doesn't need storage to work.</p> |
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*/ |
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class HmacTokenProvider implements TokenProviderInterface |
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{ |
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use BadExpireTrait; |
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/** |
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* Class constructor. |
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* |
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* @param string $value Value will be hashed inside token. |
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* @param string $key Secret key for the hmac. |
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* @param int $expire Token validity in seconds, default 600 -> 10 minutes. |
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* |
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* @throws BadExpireException If <code>$expire</code> is less than 0 and greater than 86400. |
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*/ |
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public function __construct( |
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/** @var string $key Secret key for the hmac. */ |
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private string $value, |
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/** @var string $value Value will be hashed inside token. */ |
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private string $key, |
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/** @var int $expire Token validity in seconds, default 600 -> 10 minutes. */ |
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private int $expire = 600 |
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) { |
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// from BadExpireTrait |
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/** @throws BadExpireException */ |
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$this->checkBadExpire($expire); |
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$this->key = $key; |
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$this->value = $value; |
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$this->expire = $expire; |
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} |
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/** |
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* Return new Hmac Token. |
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* |
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* @return string The token in hex format. |
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*/ |
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public function getToken(): string |
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{ |
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//get the time for the token |
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$time = \dechex(\time()); |
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//random bytes for avoid to wait one second to get a different token |
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$random = \bin2hex(\random_bytes(2)); |
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//return the token |
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return \hash_hmac('sha3-384', $this->value.$time.$random, $this->key).$time.$random; |
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} |
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/** |
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* Validate Hmac Token. |
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* |
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* @param string $token Token must be validated. |
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* |
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* @return bool True if the token is valid, false otherwise. |
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*/ |
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public function validate(string $token): bool |
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{ |
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//check for void token |
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if ($token === "") { |
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return false; |
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} |
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//hmac present in token |
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$hmac_token = \substr($token, 0, 96); |
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//token time |
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$time = \substr($token, 96, 8); |
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//random value |
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$random = \substr($token, 104); |
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//hmac generate locally with token time |
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$hmac_local = \hash_hmac('sha3-384', $this->value.$time.$random, $this->key); |
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//hmac check in constant time |
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if (!\hash_equals($hmac_local, $hmac_token)) { |
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return false; |
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} |
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//timestamp from token time |
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$timestamp = \hexdec($time); |
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//token expiration check |
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if ($timestamp + $this->expire < \time()) { |
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return false; |
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} |
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return true; |
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} |
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} |
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