Implement brute force protection

Class Throttler implements the bruteforce protection for security actions in
Nextcloud.

It is working by logging invalid login attempts to the database and slowing
down all login attempts from the same subnet. The max delay is 30 seconds and
the starting delay are 200 milliseconds. (after the first failed login)

1 files changed, 230 insertions, 0 deletions

diff --git a/lib/private/Security/Bruteforce/Throttler.php b/lib/private/Security/Bruteforce/Throttler.php
new file mode 100644
index 00000000000..5a964dfbaf4
--- /dev/null
+++ b/lib/private/Security/Bruteforce/Throttler.php
@@ -0,0 +1,230 @@
+<?php
+/**
+ * @copyright Copyright (c) 2016 Lukas Reschke <lukas@statuscode.ch>
+ *
+ * @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 OC\Security\Bruteforce;
+
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\ILogger;
+
+/**
+ * Class Throttler implements the bruteforce protection for security actions in
+ * Nextcloud.
+ *
+ * It is working by logging invalid login attempts to the database and slowing
+ * down all login attempts from the same subnet. The max delay is 30 seconds and
+ * the starting delay are 200 milliseconds. (after the first failed login)
+ *
+ * This is based on Paragonie's AirBrake for Airship CMS. You can find the original
+ * code at https://github.com/paragonie/airship/blob/7e5bad7e3c0fbbf324c11f963fd1f80e59762606/src/Engine/Security/AirBrake.php
+ *
+ * @package OC\Security\Bruteforce
+ */
+class Throttler {
+	const LOGIN_ACTION = 'login';
+
+	/** @var IDBConnection */
+	private $db;
+	/** @var ITimeFactory */
+	private $timeFactory;
+	/** @var ILogger */
+	private $logger;
+	/** @var IConfig */
+	private $config;
+
+	/**
+	 * @param IDBConnection $db
+	 * @param ITimeFactory $timeFactory
+	 * @param ILogger $logger
+	 * @param IConfig $config
+	 */
+	public function __construct(IDBConnection $db,
+								ITimeFactory $timeFactory,
+								ILogger $logger,
+								IConfig $config) {
+		$this->db = $db;
+		$this->timeFactory = $timeFactory;
+		$this->logger = $logger;
+		$this->config = $config;
+	}
+
+	/**
+	 * Convert a number of seconds into the appropriate DateInterval
+	 *
+	 * @param int $expire
+	 * @return \DateInterval
+	 */
+	private function getCutoff($expire) {
+		$d1 = new \DateTime();
+		$d2 = clone $d1;
+		$d2->sub(new \DateInterval('PT' . $expire . 'S'));
+		return $d2->diff($d1);
+	}
+
+	/**
+	 * Return the given subnet for an IPv4 address and mask bits
+	 *
+	 * @param string $ip
+	 * @param int $maskBits
+	 * @return string
+	 */
+	private function getIPv4Subnet($ip,
+								  $maskBits = 32) {
+		$binary = \inet_pton($ip);
+		for ($i = 32; $i > $maskBits; $i -= 8) {
+			$j = \intdiv($i, 8) - 1;
+			$k = (int) \min(8, $i - $maskBits);
+			$mask = (0xff - ((pow(2, $k)) - 1));
+			$int = \unpack('C', $binary[$j]);
+			$binary[$j] = \pack('C', $int[1] & $mask);
+		}
+		return \inet_ntop($binary).'/'.$maskBits;
+	}
+
+	/**
+	 * Return the given subnet for an IPv6 address and mask bits
+	 *
+	 * @param string $ip
+	 * @param int $maskBits
+	 * @return string
+	 */
+	private function getIPv6Subnet($ip, $maskBits = 48) {
+		$binary = \inet_pton($ip);
+		for ($i = 128; $i > $maskBits; $i -= 8) {
+			$j = \intdiv($i, 8) - 1;
+			$k = (int) \min(8, $i - $maskBits);
+			$mask = (0xff - ((pow(2, $k)) - 1));
+			$int = \unpack('C', $binary[$j]);
+			$binary[$j] = \pack('C', $int[1] & $mask);
+		}
+		return \inet_ntop($binary).'/'.$maskBits;
+	}
+
+	/**
+	 * Return the given subnet for an IP and the configured mask bits
+	 *
+	 * Determine if the IP is an IPv4 or IPv6 address, then pass to the correct
+	 * method for handling that specific type.
+	 *
+	 * @param string $ip
+	 * @return string
+	 */
+	private function getSubnet($ip) {
+		if (\preg_match('/^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$/', $ip)) {
+			return $this->getIPv4Subnet(
+				$ip,
+				32
+			);
+		}
+		return $this->getIPv6Subnet(
+			$ip,
+			128
+		);
+	}
+
+	/**
+	 * Register a failed attempt to bruteforce a security control
+	 *
+	 * @param string $action
+	 * @param string $ip
+	 * @param array $metadata Optional metadata logged to the database
+	 */
+	public function registerAttempt($action,
+									$ip,
+									array $metadata = []) {
+		// No need to log if the bruteforce protection is disabled
+		if($this->config->getSystemValue('auth.bruteforce.protection.enabled', true) === false) {
+			return;
+		}
+
+		$values = [
+			'action' => $action,
+			'occurred' => $this->timeFactory->getTime(),
+			'ip' => $ip,
+			'subnet' => $this->getSubnet($ip),
+			'metadata' => $metadata,
+		];
+
+		$this->logger->notice(
+			sprintf(
+				'Bruteforce attempt from "%s" detected for action "%s".',
+				$ip,
+				$action
+			),
+			[
+				'app' => 'core',
+			]
+		);
+
+		$qb = $this->db->getQueryBuilder();
+		$qb->insert('bruteforce_attempts');
+		foreach($values as $column => $value) {
+			$qb->setValue($column, $qb->createNamedParameter($value));
+		}
+		$qb->execute();
+	}
+
+	/**
+	 * Get the throttling delay (in milliseconds)
+	 *
+	 * @param string $ip
+	 * @return int
+	 */
+	public function getDelay($ip) {
+		$cutoffTime = (new \DateTime())
+			->sub($this->getCutoff(43200))
+			->getTimestamp();
+
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')
+			->from('bruteforce_attempts')
+			->where($qb->expr()->gt('occurred', $qb->createNamedParameter($cutoffTime)))
+			->andWhere($qb->expr()->eq('subnet', $qb->createNamedParameter($this->getSubnet($ip))));
+		$attempts = count($qb->execute()->fetchAll());
+
+		if ($attempts === 0) {
+			return 0;
+		}
+
+		$maxDelay = 30;
+		$firstDelay = 0.1;
+		if ($attempts > (8 * PHP_INT_SIZE - 1))  {
+			// Don't ever overflow. Just assume the maxDelay time:s
+			$firstDelay = $maxDelay;
+		} else {
+			$firstDelay *= pow(2, $attempts);
+			if ($firstDelay > $maxDelay) {
+				$firstDelay = $maxDelay;
+			}
+		}
+		return (int) \ceil($firstDelay * 1000);
+	}
+
+	/**
+	 * Will sleep for the defined amount of time
+	 *
+	 * @param string $ip
+	 */
+	public function sleepDelay($ip) {
+		usleep($this->getDelay($ip) * 1000);
+	}
+}