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<?php
declare(strict_types=1);
/*
* @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
*
* @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
*
* @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\Mail\Service;
use OCA\Mail\AppInfo\Application;
use OCA\Mail\Model\NewMessageData;
use OCP\AppFramework\Utility\ITimeFactory;
use OCP\ICacheFactory;
use OCP\IConfig;
use OCP\IMemcache;
use OCP\IUser;
use Psr\Log\LoggerInterface;
use function implode;
class AntiAbuseService {
/** @var IConfig */
private $config;
/** @var ICacheFactory */
private $cacheFactory;
/** @var ITimeFactory */
private $timeFactory;
/** @var LoggerInterface */
private $logger;
public function __construct(IConfig $config,
ICacheFactory $cacheFactory,
ITimeFactory $timeFactory,
LoggerInterface $logger) {
$this->config = $config;
$this->cacheFactory = $cacheFactory;
$this->timeFactory = $timeFactory;
$this->logger = $logger;
}
public function onBeforeMessageSent(IUser $user,
NewMessageData $messageData): void {
$abuseDetection = $this->config->getAppValue(
Application::APP_ID,
'abuse_detection',
'off'
);
if ($abuseDetection !== 'on') {
$this->logger->debug('Anti abuse detection is off');
return;
}
$this->checkNumberOfRecipients($user, $messageData);
$this->checkRateLimits($user, $messageData);
}
private function checkNumberOfRecipients(IUser $user,
NewMessageData $messageData): void {
$numberOfRecipientsThreshold = (int)$this->config->getAppValue(
Application::APP_ID,
'abuse_number_of_recipients_per_message_threshold',
'0',
);
if ($numberOfRecipientsThreshold <= 1) {
return;
}
$actualNumberOfRecipients = count($messageData->getTo())
+ count($messageData->getCc())
+ count($messageData->getBcc());
if ($actualNumberOfRecipients >= $numberOfRecipientsThreshold) {
$this->logger->alert('User {user} sends to a suspicious number of recipients. {expected} are allowed. {actual} are used', [
'user' => $user->getUID(),
'expected' => $numberOfRecipientsThreshold,
'actual' => $actualNumberOfRecipients,
]);
}
}
private function checkRateLimits(IUser $user,
NewMessageData $messageData): void {
if (!$this->cacheFactory->isAvailable()) {
// No cache, no rate limits
return;
}
$cache = $this->cacheFactory->createDistributed('mail_anti_abuse');
if (!($cache instanceof IMemcache)) {
// This integration only works with caches that support inc and dec
return;
}
$this->checkRateLimitsForPeriod($user, $messageData, $cache, '15m', 15 * 60);
$this->checkRateLimitsForPeriod($user, $messageData, $cache, '1h', 60 * 60);
$this->checkRateLimitsForPeriod($user, $messageData, $cache, '1d', 24 * 60 * 60);
}
private function checkRateLimitsForPeriod(IUser $user,
NewMessageData $messageData,
IMemcache $cache,
string $id,
int $period): void {
$maxNumberOfMessages = (int)$this->config->getAppValue(
Application::APP_ID,
'abuse_number_of_messages_per_' . $id,
'0',
);
if ($maxNumberOfMessages === 0) {
// No limit set
return;
}
$now = $this->timeFactory->getTime();
// Build blocks of periods per period size
$periodStart = ((int)($now / $period)) * $period;
$cacheKey = implode('_', ['counter', $id, $periodStart]);
$cache->add($cacheKey, 0);
$counter = $cache->inc($cacheKey, count($messageData->getTo()) + count($messageData->getCc()) + count($messageData->getBcc()));
if ($counter >= $maxNumberOfMessages) {
$this->logger->alert('User {user} sends a supcious number of messages within {period}. {expected} are allowed. {actual} have been sent', [
'user' => $user->getUID(),
'period' => $id,
'expected' => $maxNumberOfMessages,
'actual' => $counter,
]);
}
}
}
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