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<?php |
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/** |
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* Linna Cross-site Request Forgery Guard |
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* |
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* @author Sebastian Rapetti <[email protected]> |
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* @copyright (c) 2017, Sebastian Rapetti |
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* @license http://opensource.org/licenses/MIT MIT License |
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*/ |
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declare(strict_types=1); |
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namespace Linna; |
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/** |
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* Cross-site Request Forgery Guard |
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*/ |
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class CsrfGuard |
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{ |
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/** |
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* @var Session The session class. |
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*/ |
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private $session; |
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/** |
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* @var int Max number of tokens stored in session. |
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*/ |
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private $maxStorage; |
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/** |
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* @var int Rapresent the lenght of the token in bytes. |
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*/ |
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private $tokenStrength; |
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/** |
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* Constructor. |
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* |
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* @param int $maxStorage Max number of tokens stored in session, work as |
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* FIFO data structure, when maximun capacity is |
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* reached, oldest token be dequeued from storage. |
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* @param int $tokenStrength Rapresent the lenght of the token in bytes. |
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*/ |
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public function __construct(int $maxStorage, int $tokenStrength) |
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{ |
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//if csrf array doesn't exist inside session, initialize it. |
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//for code shortness: Null coalescing operator |
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//http://php.net/manual/en/migration70.new-features.php |
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$_SESSION['CSRF'] = $_SESSION['CSRF'] ?? []; |
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$this->session = &$_SESSION; |
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$this->maxStorage = $maxStorage; |
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$this->tokenStrength = $tokenStrength; |
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} |
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/** |
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* Limit number of token stored in session. |
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*/ |
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private function dequeue(array &$array) |
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{ |
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$size = count($array); |
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while ($size > $this->maxStorage){ |
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array_shift($array); |
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$size--; |
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} |
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} |
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/** |
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* Return csrf token as array. |
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* |
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* @return array |
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*/ |
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public function getToken() : array |
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{ |
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$tokenName = 'csrf_'.bin2hex(random_bytes(8)); |
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$token = bin2hex(random_bytes($this->tokenStrength)); |
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$this->session['CSRF'][$tokenName] = $token; |
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//storage cleaning! |
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//warning!! if you get in a page more token of maximun storage, |
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//will there a leak of token, the firsts generated |
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//in future I think throw and exception. |
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$this->dequeue($this->session['CSRF']); |
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return ['name' => $tokenName, 'token' => $token]; |
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} |
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/** |
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* Return csrf token as hidden input form. |
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* |
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* @return string |
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*/ |
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1 |
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public function getHiddenInput() : string |
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{ |
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$token = $this->getToken(); |
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return '<input type="hidden" name="'.$token['name'].'" value="'.$token['token'].'" />'; |
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} |
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/** |
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* Validate a csrf token. |
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* |
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* @param array $requestData From request or from superglobal variables $_POST, |
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* $_GET, $_REQUEST and $_COOKIE. |
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* |
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* @return bool |
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*/ |
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public function validate(array $requestData) : bool |
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{ |
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$arrayToken = $this->session['CSRF']; |
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foreach ($requestData as $key => $value){ |
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if (isset($arrayToken[$key]) && hash_equals($arrayToken[$key], $value)){ |
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return true; |
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} |
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} |
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return false; |
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} |
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} |
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linna /
csrf-guard
