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)

6 files changed, 278 insertions, 21 deletions

diff --git a/lib/private/AppFramework/DependencyInjection/DIContainer.php b/lib/private/AppFramework/DependencyInjection/DIContainer.php
index f21b34a6b4a..1684ff8027b 100644
--- a/lib/private/AppFramework/DependencyInjection/DIContainer.php
+++ b/lib/private/AppFramework/DependencyInjection/DIContainer.php
@@ -351,7 +351,8 @@ class DIContainer extends SimpleContainer implements IAppContainer {
 			return new CORSMiddleware(
 				$c['Request'],
 				$c['ControllerMethodReflector'],
-				$c['OCP\IUserSession']
+				$c['OCP\IUserSession'],
+				$c->getServer()->getBruteForceThrottler()
 			);
 		});
 
diff --git a/lib/private/AppFramework/Middleware/Security/CORSMiddleware.php b/lib/private/AppFramework/Middleware/Security/CORSMiddleware.php
index 32a507623e3..04de4bc92d3 100644
--- a/lib/private/AppFramework/Middleware/Security/CORSMiddleware.php
+++ b/lib/private/AppFramework/Middleware/Security/CORSMiddleware.php
@@ -27,6 +27,7 @@ namespace OC\AppFramework\Middleware\Security;
 use OC\AppFramework\Middleware\Security\Exceptions\SecurityException;
 use OC\AppFramework\Utility\ControllerMethodReflector;
 use OC\Authentication\Exceptions\PasswordLoginForbiddenException;
+use OC\Security\Bruteforce\Throttler;
 use OC\User\Session;
 use OCP\AppFramework\Controller;
 use OCP\AppFramework\Http;
@@ -42,33 +43,29 @@ use OCP\IRequest;
  * https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS
  */
 class CORSMiddleware extends Middleware {
-
-	/**
-	 * @var IRequest
-	 */
+	/** @var IRequest  */
 	private $request;
-
-	/**
-	 * @var ControllerMethodReflector
-	 */
+	/** @var ControllerMethodReflector */
 	private $reflector;
-
-	/**
-	 * @var Session
-	 */
+	/** @var Session */
 	private $session;
+	/** @var Throttler */
+	private $throttler;
 
 	/**
 	 * @param IRequest $request
 	 * @param ControllerMethodReflector $reflector
 	 * @param Session $session
+	 * @param Throttler $throttler
 	 */
 	public function __construct(IRequest $request,
 								ControllerMethodReflector $reflector,
-								Session $session) {
+								Session $session,
+								Throttler $throttler) {
 		$this->request = $request;
 		$this->reflector = $reflector;
 		$this->session = $session;
+		$this->throttler = $throttler;
 	}
 
 	/**
@@ -91,7 +88,7 @@ class CORSMiddleware extends Middleware {
 
 			$this->session->logout();
 			try {
-				if (!$this->session->logClientIn($user, $pass, $this->request)) {
+				if (!$this->session->logClientIn($user, $pass, $this->request, $this->throttler)) {
 					throw new SecurityException('CORS requires basic auth', Http::STATUS_UNAUTHORIZED);
 				}
 			} catch (PasswordLoginForbiddenException $ex) {
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);
+	}
+}
diff --git a/lib/private/Server.php b/lib/private/Server.php
index eb2c26415bc..6ffdeb9211e 100644
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@@ -66,6 +66,7 @@ use OC\Lock\NoopLockingProvider;
 use OC\Mail\Mailer;
 use OC\Memcache\ArrayCache;
 use OC\Notification\Manager;
+use OC\Security\Bruteforce\Throttler;
 use OC\Security\CertificateManager;
 use OC\Security\CSP\ContentSecurityPolicyManager;
 use OC\Security\Crypto;
@@ -503,6 +504,14 @@ class Server extends ServerContainer implements IServerContainer {
 		$this->registerService('TrustedDomainHelper', function ($c) {
 			return new TrustedDomainHelper($this->getConfig());
 		});
+		$this->registerService('Throttler', function(Server $c) {
+			return new Throttler(
+				$c->getDatabaseConnection(),
+				new TimeFactory(),
+				$c->getLogger(),
+				$c->getConfig()
+			);
+		});
 		$this->registerService('IntegrityCodeChecker', function (Server $c) {
 			// IConfig and IAppManager requires a working database. This code
 			// might however be called when ownCloud is not yet setup.
@@ -1331,6 +1340,13 @@ class Server extends ServerContainer implements IServerContainer {
 	}
 
 	/**
+	 * @return Throttler
+	 */
+	public function getBruteForceThrottler() {
+		return $this->query('Throttler');
+	}
+
+	/**
 	 * @return IContentSecurityPolicyManager
 	 */
 	public function getContentSecurityPolicyManager() {
diff --git a/lib/private/User/Session.php b/lib/private/User/Session.php
index dcc2e66c6c3..79bd7c22848 100644
--- a/lib/private/User/Session.php
+++ b/lib/private/User/Session.php
@@ -95,7 +95,11 @@ class Session implements IUserSession, Emitter {
 	 * @param IProvider $tokenProvider
 	 * @param IConfig $config
 	 */
-	public function __construct(IUserManager $manager, ISession $session, ITimeFactory $timeFacory, $tokenProvider, IConfig $config) {
+	public function __construct(IUserManager $manager,
+								ISession $session,
+								ITimeFactory $timeFacory,
+								$tokenProvider,
+								IConfig $config) {
 		$this->manager = $manager;
 		$this->session = $session;
 		$this->timeFacory = $timeFacory;
@@ -280,7 +284,6 @@ class Session implements IUserSession, Emitter {
 	 */
 	public function login($uid, $password) {
 		$this->session->regenerateId();
-
 		if ($this->validateToken($password, $uid)) {
 			return $this->loginWithToken($password);
 		} else {
@@ -298,11 +301,17 @@ class Session implements IUserSession, Emitter {
 	 * @param string $user
 	 * @param string $password
 	 * @param IRequest $request
+	 * @param OC\Security\Bruteforce\Throttler $throttler
 	 * @throws LoginException
 	 * @throws PasswordLoginForbiddenException
 	 * @return boolean
 	 */
-	public function logClientIn($user, $password, IRequest $request) {
+	public function logClientIn($user,
+								$password,
+								IRequest $request,
+								OC\Security\Bruteforce\Throttler $throttler) {
+		$throttler->sleepDelay($request->getRemoteAddress());
+
 		$isTokenPassword = $this->isTokenPassword($password);
 		if (!$isTokenPassword && $this->isTokenAuthEnforced()) {
 			throw new PasswordLoginForbiddenException();
@@ -315,6 +324,8 @@ class Session implements IUserSession, Emitter {
 			if (count($users) === 1) {
 				return $this->login($users[0]->getUID(), $password);
 			}
+
+			$throttler->registerAttempt('login', $request->getRemoteAddress(), ['uid' => $user]);
 			return false;
 		}
 
@@ -391,10 +402,12 @@ class Session implements IUserSession, Emitter {
 	 * @param IRequest $request
 	 * @return boolean if the login was successful
 	 */
-	public function tryBasicAuthLogin(IRequest $request) {
+	public function tryBasicAuthLogin(IRequest $request,
+									  OC\Security\Bruteforce\Throttler $throttler) {
 		if (!empty($request->server['PHP_AUTH_USER']) && !empty($request->server['PHP_AUTH_PW'])) {
+			$throttler->sleepDelay(\OC::$server->getRequest()->getRemoteAddress());
 			try {
-				if ($this->logClientIn($request->server['PHP_AUTH_USER'], $request->server['PHP_AUTH_PW'], $request)) {
+				if ($this->logClientIn($request->server['PHP_AUTH_USER'], $request->server['PHP_AUTH_PW'], $request, $throttler)) {
 					/**
 					 * Add DAV authenticated. This should in an ideal world not be
 					 * necessary but the iOS App reads cookies from anywhere instead
diff --git a/lib/private/legacy/api.php b/lib/private/legacy/api.php
index 024f3c0fb63..88eb7b09a78 100644
--- a/lib/private/legacy/api.php
+++ b/lib/private/legacy/api.php
@@ -364,7 +364,7 @@ class OC_API {
 		try {
 			$loginSuccess = $userSession->tryTokenLogin($request);
 			if (!$loginSuccess) {
-				$loginSuccess = $userSession->tryBasicAuthLogin($request);
+				$loginSuccess = $userSession->tryBasicAuthLogin($request, \OC::$server->getBruteForceThrottler());
 			}
 		} catch (\OC\User\LoginException $e) {
 			return false;