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<?php
/*
* @copyright Copyright (c) 2022 Vitor Mattos <vitor@php.rio>
*
* @author Vitor Mattos <vitor@php.rio>
*
* @license GNU AGPL version 3 or any later version
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
namespace OCA\Talk\Service;
use OCA\Talk\Exceptions\UnauthorizedException;
class SIPBridgeService {
/**
* Check if the current request is coming from an allowed backend.
*
* The SIP bridge is sending the custom header "Talk-SIPBridge-Random"
* containing at least 32 bytes random data, and the header
* "Talk-SIPBridge-Checksum", which is the SHA256-HMAC of the random data
* and the body of the request, calculated with the shared secret from the
* configuration.
*
* @param string $random
* @param string $checksum
* @param string $secret
* @param string $token
* @return bool True if the request is from the SIP bridge and valid, false if not from SIP bridge
* @throws UnauthorizedException when the request tried to sign as SIP bridge but is not valid
*/
public function validateSIPBridgeRequest(string $random, string $checksum, string $secret, string $token): bool {
if ($random === '' && $checksum === '') {
return false;
}
if (strlen($random) < 32) {
throw new UnauthorizedException('Invalid random provided');
}
if (empty($checksum)) {
throw new UnauthorizedException('Invalid checksum provided');
}
if (empty($secret)) {
throw new UnauthorizedException('No shared SIP secret provided');
}
$hash = hash_hmac('sha256', $random . $token, $secret);
if (hash_equals($hash, strtolower($checksum))) {
return true;
}
throw new UnauthorizedException('Invalid HMAC provided');
}
}