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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* This files exposes functions for LTI 1.3 Key Management.
*
* @package mod_lti
* @copyright 2020 Claude Vervoort (Cengage)
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace mod_lti\local\ltiopenid;
/**
* This class exposes functions for LTI 1.3 Key Management.
*
* @package mod_lti
* @copyright 2020 Claude Vervoort (Cengage)
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class jwks_helper {
/**
* Returns the private key to use to sign outgoing JWT.
*
* @return array keys are kid and key in PEM format.
*/
public static function get_private_key() {
$privatekey = get_config('mod_lti', 'privatekey');
$kid = get_config('mod_lti', 'kid');
return [
"key" => $privatekey,
"kid" => $kid
];
}
/**
* Returns the JWK Key Set for this site.
* @return array keyset exposting the site public key.
*/
public static function get_jwks() {
$jwks = array('keys' => array());
$privatekey = self::get_private_key();
$res = openssl_pkey_get_private($privatekey['key']);
$details = openssl_pkey_get_details($res);
$jwk = array();
$jwk['kty'] = 'RSA';
$jwk['alg'] = 'RS256';
$jwk['kid'] = $privatekey['kid'];
$jwk['e'] = rtrim(strtr(base64_encode($details['rsa']['e']), '+/', '-_'), '=');
$jwk['n'] = rtrim(strtr(base64_encode($details['rsa']['n']), '+/', '-_'), '=');
$jwk['use'] = 'sig';
$jwks['keys'][] = $jwk;
return $jwks;
}
}