[master] Port Same-Site Cookies to master

Fixes https://github.com/nextcloud/server/issues/50

8 files changed, 198 insertions, 1 deletions

diff --git a/lib/base.php b/lib/base.php
index be9de93f73f..afa13cd1047 100644
--- a/lib/base.php
+++ b/lib/base.php
@@ -469,6 +469,84 @@ class OC {
 		@ini_set('gd.jpeg_ignore_warning', 1);
 	}
 
+	/**
+	 * Send the same site cookies
+	 */
+	private static function sendSameSiteCookies() {
+		$cookieParams = session_get_cookie_params();
+		$secureCookie = ($cookieParams['secure'] === true) ? 'secure; ' : '';
+		$policies = [
+			'lax',
+			'strict',
+		];
+		foreach($policies as $policy) {
+			header(
+				sprintf(
+					'Set-Cookie: nc_sameSiteCookie%s=true; path=%s; httponly;' . $secureCookie . 'expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=%s',
+					$policy,
+					$cookieParams['path'],
+					$policy
+				),
+				false
+			);
+		}
+	}
+
+	/**
+	 * Same Site cookie to further mitigate CSRF attacks. This cookie has to
+	 * be set in every request if cookies are sent to add a second level of
+	 * defense against CSRF.
+	 *
+	 * If the cookie is not sent this will set the cookie and reload the page.
+	 * We use an additional cookie since we want to protect logout CSRF and
+	 * also we can't directly interfere with PHP's session mechanism.
+	 */
+	private static function performSameSiteCookieProtection() {
+		if(count($_COOKIE) > 0) {
+			$request = \OC::$server->getRequest();
+			$requestUri = $request->getScriptName();
+			$processingScript = explode('/', $requestUri);
+			$processingScript = $processingScript[count($processingScript)-1];
+			// FIXME: In a SAML scenario we don't get any strict or lax cookie
+			// send for the ACS endpoint. Since we have some legacy code in Nextcloud
+			// (direct PHP files) the enforcement of lax cookies is performed here
+			// instead of the middleware.
+			//
+			// This means we cannot exclude some routes from the cookie validation,
+			// which normally is not a problem but is a little bit cumbersome for
+			// this use-case.
+			// Once the old legacy PHP endpoints have been removed we can move
+			// the verification into a middleware and also adds some exemptions.
+			//
+			// Questions about this code? Ask Lukas ;-)
+			$currentUrl = substr(explode('?',$request->getRequestUri(), 2)[0], strlen(\OC::$WEBROOT));
+			if($currentUrl === '/index.php/apps/user_saml/saml/acs') {
+				return;
+			}
+			// For the "index.php" endpoint only a lax cookie is required.
+			if($processingScript === 'index.php') {
+				if(!$request->passesLaxCookieCheck()) {
+					self::sendSameSiteCookies();
+					header('Location: '.$_SERVER['REQUEST_URI']);
+					exit();
+				}
+			} else {
+				// All other endpoints require the lax and the strict cookie
+				if(!$request->passesStrictCookieCheck()) {
+					self::sendSameSiteCookies();
+					// Debug mode gets access to the resources without strict cookie
+					// due to the fact that the SabreDAV browser also lives there.
+					if(!\OC::$server->getConfig()->getSystemValue('debug', false)) {
+						http_response_code(\OCP\AppFramework\Http::STATUS_SERVICE_UNAVAILABLE);
+						exit();
+					}
+				}
+			}
+		} elseif(!isset($_COOKIE['nc_sameSiteCookielax']) || !isset($_COOKIE['nc_sameSiteCookiestrict'])) {
+			self::sendSameSiteCookies();
+		}
+	}
+
 	public static function init() {
 		// calculate the root directories
 		OC::$SERVERROOT = str_replace("\\", '/', substr(__DIR__, 0, -4));
@@ -572,6 +650,8 @@ class OC {
 			ini_set('session.cookie_secure', true);
 		}
 
+		self::performSameSiteCookieProtection();
+
 		if (!defined('OC_CONSOLE')) {
 			$errors = OC_Util::checkServer(\OC::$server->getConfig());
 			if (count($errors) > 0) {
diff --git a/lib/private/AppFramework/Http/Request.php b/lib/private/AppFramework/Http/Request.php
index d9cf1919252..8fc99f125b2 100644
--- a/lib/private/AppFramework/Http/Request.php
+++ b/lib/private/AppFramework/Http/Request.php
@@ -465,6 +465,10 @@ class Request implements \ArrayAccess, \Countable, IRequest {
 			return false;
 		}
 
+		if(!$this->passesStrictCookieCheck()) {
+			return false;
+		}
+
 		if (isset($this->items['get']['requesttoken'])) {
 			$token = $this->items['get']['requesttoken'];
 		} elseif (isset($this->items['post']['requesttoken'])) {
@@ -481,6 +485,42 @@ class Request implements \ArrayAccess, \Countable, IRequest {
 	}
 
 	/**
+	 * Checks if the strict cookie has been sent with the request if the request
+	 * is including any cookies.
+	 *
+	 * @return bool
+	 * @since 9.1.0
+	 */
+	public function passesStrictCookieCheck() {
+		if(count($this->cookies) === 0) {
+			return true;
+		}
+		if($this->getCookie('nc_sameSiteCookiestrict') === 'true'
+			&& $this->passesLaxCookieCheck()) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Checks if the lax cookie has been sent with the request if the request
+	 * is including any cookies.
+	 *
+	 * @return bool
+	 * @since 9.1.0
+	 */
+	public function passesLaxCookieCheck() {
+		if(count($this->cookies) === 0) {
+			return true;
+		}
+		if($this->getCookie('nc_sameSiteCookielax') === 'true') {
+			return true;
+		}
+		return false;
+	}
+
+
+	/**
 	 * Returns an ID for the request, value is not guaranteed to be unique and is mostly meant for logging
 	 * If `mod_unique_id` is installed this value will be taken.
 	 * @return string
diff --git a/lib/private/AppFramework/Middleware/Security/Exceptions/StrictCookieMissingException.php b/lib/private/AppFramework/Middleware/Security/Exceptions/StrictCookieMissingException.php
new file mode 100644
index 00000000000..9ccaed4566f
--- /dev/null
+++ b/lib/private/AppFramework/Middleware/Security/Exceptions/StrictCookieMissingException.php
@@ -0,0 +1,36 @@
+<?php
+/**
+ * @author 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\AppFramework\Middleware\Security\Exceptions;
+
+use OCP\AppFramework\Http;
+
+/**
+ * Class StrictCookieMissingException is thrown when the strict cookie has not
+ * been sent with the request but is required.
+ *
+ * @package OC\AppFramework\Middleware\Security\Exceptions
+ */
+class StrictCookieMissingException extends SecurityException {
+	public function __construct() {
+		parent::__construct('Strict Cookie has not been found in request.', Http::STATUS_PRECONDITION_FAILED);
+	}
+}
diff --git a/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php b/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php
index a3ece262e10..98117751e21 100644
--- a/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php
+++ b/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php
@@ -32,6 +32,7 @@ use OC\AppFramework\Middleware\Security\Exceptions\AppNotEnabledException;
 use OC\AppFramework\Middleware\Security\Exceptions\CrossSiteRequestForgeryException;
 use OC\AppFramework\Middleware\Security\Exceptions\NotAdminException;
 use OC\AppFramework\Middleware\Security\Exceptions\NotLoggedInException;
+use OC\AppFramework\Middleware\Security\Exceptions\StrictCookieMissingException;
 use OC\AppFramework\Utility\ControllerMethodReflector;
 use OC\Security\CSP\ContentSecurityPolicyManager;
 use OCP\AppFramework\Http\ContentSecurityPolicy;
@@ -134,6 +135,12 @@ class SecurityMiddleware extends Middleware {
 			}
 		}
 
+		// Check for strict cookie requirement
+		if($this->reflector->hasAnnotation('StrictCookieRequired') || !$this->reflector->hasAnnotation('NoCSRFRequired')) {
+			if(!$this->request->passesStrictCookieCheck()) {
+				throw new StrictCookieMissingException();
+			}
+		}
 		// CSRF check - also registers the CSRF token since the session may be closed later
 		Util::callRegister();
 		if(!$this->reflector->hasAnnotation('NoCSRFRequired')) {
@@ -186,7 +193,9 @@ class SecurityMiddleware extends Middleware {
 	 */
 	public function afterException($controller, $methodName, \Exception $exception) {
 		if($exception instanceof SecurityException) {
-
+			if($exception instanceof StrictCookieMissingException) {
+				return new RedirectResponse(\OC::$WEBROOT);
+ 			}
 			if (stripos($this->request->getHeader('Accept'),'html') === false) {
 				$response = new JSONResponse(
 					array('message' => $exception->getMessage()),
diff --git a/lib/private/legacy/eventsource.php b/lib/private/legacy/eventsource.php
index 51040e7be7d..70e9847d237 100644
--- a/lib/private/legacy/eventsource.php
+++ b/lib/private/legacy/eventsource.php
@@ -76,6 +76,10 @@ class OC_EventSource implements \OCP\IEventSource {
 		} else {
 			header("Content-Type: text/event-stream");
 		}
+		if(!\OC::$server->getRequest()->passesStrictCookieCheck()) {
+			header('Location: '.\OC::$WEBROOT);
+			exit();
+		}
 		if (!(\OC::$server->getRequest()->passesCSRFCheck())) {
 			$this->send('error', 'Possible CSRF attack. Connection will be closed.');
 			$this->close();
diff --git a/lib/private/legacy/json.php b/lib/private/legacy/json.php
index 1dde63602b1..557e1d77012 100644
--- a/lib/private/legacy/json.php
+++ b/lib/private/legacy/json.php
@@ -79,6 +79,11 @@ class OC_JSON{
 	 * @deprecated Use annotation based CSRF checks from the AppFramework instead
 	 */
 	public static function callCheck() {
+		if(!\OC::$server->getRequest()->passesStrictCookieCheck()) {
+			header('Location: '.\OC::$WEBROOT);
+			exit();
+		}
+
 		if( !(\OC::$server->getRequest()->passesCSRFCheck())) {
 			$l = \OC::$server->getL10N('lib');
 			self::error(array( 'data' => array( 'message' => $l->t('Token expired. Please reload page.'), 'error' => 'token_expired' )));
diff --git a/lib/public/IRequest.php b/lib/public/IRequest.php
index 4db1c18b9c1..46e67d1415f 100644
--- a/lib/public/IRequest.php
+++ b/lib/public/IRequest.php
@@ -158,6 +158,24 @@ interface IRequest {
 	public function passesCSRFCheck();
 
 	/**
+	 * Checks if the strict cookie has been sent with the request if the request
+	 * is including any cookies.
+	 *
+	 * @return bool
+	 * @since 9.0.0
+	 */
+	public function passesStrictCookieCheck();
+
+	/**
+	 * Checks if the lax cookie has been sent with the request if the request
+	 * is including any cookies.
+	 *
+	 * @return bool
+	 * @since 9.0.0
+	 */
+	public function passesLaxCookieCheck();
+
+	/**
 	 * Returns an ID for the request, value is not guaranteed to be unique and is mostly meant for logging
 	 * If `mod_unique_id` is installed this value will be taken.
 	 *
diff --git a/lib/public/Util.php b/lib/public/Util.php
index 687f4e78f69..9422dbac66a 100644
--- a/lib/public/Util.php
+++ b/lib/public/Util.php
@@ -513,6 +513,11 @@ class Util {
 	 * @deprecated 9.0.0 Use annotations based on the app framework.
 	 */
 	public static function callCheck() {
+		if(!\OC::$server->getRequest()->passesStrictCookieCheck()) {
+			header('Location: '.\OC::$WEBROOT);
+			exit();
+		}
+
 		if (!(\OC::$server->getRequest()->passesCSRFCheck())) {
 			exit();
 		}