Merge pull request #18254 from owncloud/mitigate-breach

Add mitigation against BREACH

4 files changed, 29 insertions, 15 deletions

diff --git a/lib/base.php b/lib/base.php
index 42e1d7f8586..1f921b13e67 100644
--- a/lib/base.php
+++ b/lib/base.php
@@ -134,18 +134,7 @@ class OC {
 		OC_Config::$object = new \OC\Config(self::$configDir);
 
 		OC::$SUBURI = str_replace("\\", "/", substr(realpath($_SERVER["SCRIPT_FILENAME"]), strlen(OC::$SERVERROOT)));
-		/**
-		 * FIXME: The following line is required because of a cyclic dependency
-		 *        on IRequest.
-		 */
-		$params = [
-			'server' => [
-				'SCRIPT_NAME' => $_SERVER['SCRIPT_NAME'],
-				'SCRIPT_FILENAME' => $_SERVER['SCRIPT_FILENAME'],
-			],
-		];
-		$fakeRequest = new \OC\AppFramework\Http\Request($params, null, new \OC\AllConfig(new \OC\SystemConfig()));
-		$scriptName = $fakeRequest->getScriptName();
+		$scriptName = $_SERVER['SCRIPT_NAME'];
 		if (substr($scriptName, -1) == '/') {
 			$scriptName .= 'index.php';
 			//make sure suburi follows the same rules as scriptName
diff --git a/lib/private/appframework/http/request.php b/lib/private/appframework/http/request.php
index aaad286e843..a2109439177 100644
--- a/lib/private/appframework/http/request.php
+++ b/lib/private/appframework/http/request.php
@@ -32,6 +32,7 @@ namespace OC\AppFramework\Http;
 use OC\Security\TrustedDomainHelper;
 use OCP\IConfig;
 use OCP\IRequest;
+use OCP\Security\ICrypto;
 use OCP\Security\ISecureRandom;
 
 /**
@@ -67,6 +68,8 @@ class Request implements \ArrayAccess, \Countable, IRequest {
 	protected $config;
 	/** @var string */
 	protected $requestId = '';
+	/** @var ICrypto */
+	protected $crypto;
 
 	/**
 	 * @param array $vars An associative array with the following optional values:
@@ -80,17 +83,20 @@ class Request implements \ArrayAccess, \Countable, IRequest {
 	 *        - string 'method' the request method (GET, POST etc)
 	 *        - string|false 'requesttoken' the requesttoken or false when not available
 	 * @param ISecureRandom $secureRandom
+	 * @param ICrypto $crypto
 	 * @param IConfig $config
 	 * @param string $stream
 	 * @see http://www.php.net/manual/en/reserved.variables.php
 	 */
 	public function __construct(array $vars=array(),
 								ISecureRandom $secureRandom = null,
+								ICrypto $crypto,
 								IConfig $config,
 								$stream='php://input') {
 		$this->inputStream = $stream;
 		$this->items['params'] = array();
 		$this->secureRandom = $secureRandom;
+		$this->crypto = $crypto;
 		$this->config = $config;
 
 		if(!array_key_exists('method', $vars)) {
@@ -415,8 +421,22 @@ class Request implements \ArrayAccess, \Countable, IRequest {
 			return false;
 		}
 
+		// Decrypt token to prevent BREACH like attacks
+		$token = explode(':', $token);
+		if (count($token) !== 2) {
+			return false;
+		}
+
+		$encryptedToken = $token[0];
+		$secret = $token[1];
+		try {
+			$decryptedToken = $this->crypto->decrypt($encryptedToken, $secret);
+		} catch (\Exception $e) {
+			return false;
+		}
+
 		// Check if the token is valid
-		if(\OCP\Security\StringUtils::equals($token, $this->items['requesttoken'])) {
+		if(\OCP\Security\StringUtils::equals($decryptedToken, $this->items['requesttoken'])) {
 			return true;
 		} else {
 			return false;
diff --git a/lib/private/server.php b/lib/private/server.php
index 89001567219..ff78536cec0 100644
--- a/lib/private/server.php
+++ b/lib/private/server.php
@@ -410,6 +410,7 @@ class Server extends SimpleContainer implements IServerContainer {
 					'requesttoken' => $requestToken,
 				],
 				$this->getSecureRandom(),
+				$this->getCrypto(),
 				$this->getConfig(),
 				$stream
 			);
diff --git a/lib/private/util.php b/lib/private/util.php
index 501dbf5c4c5..edd375b5c36 100644
--- a/lib/private/util.php
+++ b/lib/private/util.php
@@ -1057,7 +1057,8 @@ class OC_Util {
 	/**
 	 * Register an get/post call. Important to prevent CSRF attacks.
 	 *
-	 * @return string Generated token.
+	 * @return string The encrypted CSRF token, the shared secret is appended after the `:`.
+	 *
 	 * @description
 	 * Creates a 'request token' (random) and stores it inside the session.
 	 * Ever subsequent (ajax) request must use such a valid token to succeed,
@@ -1074,7 +1075,10 @@ class OC_Util {
 			// Valid token already exists, send it
 			$requestToken = \OC::$server->getSession()->get('requesttoken');
 		}
-		return ($requestToken);
+
+		// Encrypt the token to mitigate breach-like attacks
+		$sharedSecret = \OC::$server->getSecureRandom()->getMediumStrengthGenerator()->generate(10);
+		return \OC::$server->getCrypto()->encrypt($requestToken, $sharedSecret) . ':' . $sharedSecret;
 	}
 
 	/**