Add support for CSP nonces

CSP nonces are a feature available with CSP v2. Basically instead of saying "JS resources from the same domain are ok to be served" we now say "Ressources from everywhere are allowed as long as they add a `nonce` attribute to the script tag with the right nonce.

At the moment the nonce is basically just a `<?php p(base64_encode($_['requesttoken'])) ?>`, we have to decode the requesttoken since `:` is not an allowed value in the nonce. So if somebody does on their own include JS files (instead of using the `addScript` public API, they now must also include that attribute.)

IE does currently not implement CSP v2, thus there is a whitelist included that delivers the new CSP v2 policy to newer browsers. Check http://caniuse.com/#feat=contentsecuritypolicy2 for the current browser support list. An alternative approach would be to just add `'unsafe-inline'` as well as `'unsafe-inline'` is ignored by CSPv2 when a nonce is set. But this would make this security feature unusable at all in IE. Not worth it at the moment IMO.

Implementing this offers the following advantages:

1. **Security:** As we host resources from the same domain by design we don't have to worry about 'self' anymore being in the whitelist
2. **Performance:** We can move oc.js again to inline JS. This makes the loading way quicker as we don't have to load on every load of a new web page a blocking dynamically non-cached JavaScript file.

If you want to toy with CSP see also https://csp-evaluator.withgoogle.com/

Signed-off-by: Lukas Reschke <lukas@statuscode.ch>

14 files changed, 176 insertions, 12 deletions

diff --git a/apps/theming/appinfo/app.php b/apps/theming/appinfo/app.php
index e67092b642f..03fdbc9d002 100644
--- a/apps/theming/appinfo/app.php
+++ b/apps/theming/appinfo/app.php
@@ -47,6 +47,7 @@ $linkToJs = \OC::$server->getURLGenerator()->linkToRoute(
 	'script',
 	[
 		'src' => $linkToJs,
+		'nonce' => base64_encode(\OC::$server->getCsrfTokenManager()->getToken()->getEncryptedValue())
 	], ''
 );
 
diff --git a/core/templates/layout.base.php b/core/templates/layout.base.php
index 7301ae690cc..d6fda96dd68 100644
--- a/core/templates/layout.base.php
+++ b/core/templates/layout.base.php
@@ -19,7 +19,7 @@
 			<link rel="stylesheet" href="<?php print_unescaped($cssfile); ?>" media="print">
 		<?php endforeach; ?>
 		<?php foreach ($_['jsfiles'] as $jsfile): ?>
-			<script src="<?php print_unescaped($jsfile); ?>"></script>
+			<script src="<?php print_unescaped($jsfile); ?>" nonce="<?php p(base64_encode($_['requesttoken'])) ?>"></script>
 		<?php endforeach; ?>
 		<?php print_unescaped($_['headers']); ?>
 	</head>
diff --git a/core/templates/layout.guest.php b/core/templates/layout.guest.php
index 58506353158..a93224af5cc 100644
--- a/core/templates/layout.guest.php
+++ b/core/templates/layout.guest.php
@@ -20,7 +20,7 @@
 			<link rel="stylesheet" href="<?php print_unescaped($cssfile); ?>" media="print">
 		<?php endforeach; ?>
 		<?php foreach($_['jsfiles'] as $jsfile): ?>
-			<script src="<?php print_unescaped($jsfile); ?>"></script>
+			<script nonce="<?php p(base64_encode($_['requesttoken'])) ?>" src="<?php print_unescaped($jsfile); ?>"></script>
 		<?php endforeach; ?>
 		<?php print_unescaped($_['headers']); ?>
 	</head>
diff --git a/core/templates/layout.user.php b/core/templates/layout.user.php
index 285eb3ab5f3..d3dcd979d38 100644
--- a/core/templates/layout.user.php
+++ b/core/templates/layout.user.php
@@ -27,7 +27,7 @@
 			<link rel="stylesheet" href="<?php print_unescaped($cssfile); ?>" media="print">
 		<?php endforeach; ?>
 		<?php foreach($_['jsfiles'] as $jsfile): ?>
-			<script src="<?php print_unescaped($jsfile); ?>"></script>
+			<script nonce="<?php p(base64_encode($_['requesttoken'])) ?>" src="<?php print_unescaped($jsfile); ?>"></script>
 		<?php endforeach; ?>
 		<?php print_unescaped($_['headers']); ?>
 	</head>
diff --git a/lib/private/AppFramework/DependencyInjection/DIContainer.php b/lib/private/AppFramework/DependencyInjection/DIContainer.php
index 21d5eaa9503..97faa0edf49 100644
--- a/lib/private/AppFramework/DependencyInjection/DIContainer.php
+++ b/lib/private/AppFramework/DependencyInjection/DIContainer.php
@@ -379,7 +379,8 @@ class DIContainer extends SimpleContainer implements IAppContainer {
 				$c['AppName'],
 				$app->isLoggedIn(),
 				$app->isAdminUser(),
-				$app->getServer()->getContentSecurityPolicyManager()
+				$app->getServer()->getContentSecurityPolicyManager(),
+				$app->getServer()->getCsrfTokenManager()
 			);
 		});
 
diff --git a/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php b/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php
index 5e253d0954a..6c33c0023ea 100644
--- a/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php
+++ b/lib/private/AppFramework/Middleware/Security/SecurityMiddleware.php
@@ -36,6 +36,7 @@ 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 OC\Security\CSRF\CsrfTokenManager;
 use OCP\AppFramework\Http\ContentSecurityPolicy;
 use OCP\AppFramework\Http\EmptyContentSecurityPolicy;
 use OCP\AppFramework\Http\RedirectResponse;
@@ -77,6 +78,8 @@ class SecurityMiddleware extends Middleware {
 	private $isAdminUser;
 	/** @var ContentSecurityPolicyManager */
 	private $contentSecurityPolicyManager;
+	/** @var CsrfTokenManager */
+	private $csrfTokenManager;
 
 	/**
 	 * @param IRequest $request
@@ -88,6 +91,7 @@ class SecurityMiddleware extends Middleware {
 	 * @param bool $isLoggedIn
 	 * @param bool $isAdminUser
 	 * @param ContentSecurityPolicyManager $contentSecurityPolicyManager
+	 * @param CSRFTokenManager $csrfTokenManager
 	 */
 	public function __construct(IRequest $request,
 								ControllerMethodReflector $reflector,
@@ -97,7 +101,8 @@ class SecurityMiddleware extends Middleware {
 								$appName,
 								$isLoggedIn,
 								$isAdminUser,
-								ContentSecurityPolicyManager $contentSecurityPolicyManager) {
+								ContentSecurityPolicyManager $contentSecurityPolicyManager,
+								CsrfTokenManager $csrfTokenManager) {
 		$this->navigationManager = $navigationManager;
 		$this->request = $request;
 		$this->reflector = $reflector;
@@ -107,6 +112,7 @@ class SecurityMiddleware extends Middleware {
 		$this->isLoggedIn = $isLoggedIn;
 		$this->isAdminUser = $isAdminUser;
 		$this->contentSecurityPolicyManager = $contentSecurityPolicyManager;
+		$this->csrfTokenManager = $csrfTokenManager;
 	}
 
 
@@ -171,6 +177,23 @@ class SecurityMiddleware extends Middleware {
 
 	}
 
+	private function browserSupportsCspV3() {
+		$browserWhitelist = [
+			// Chrome 40+
+			'/^Mozilla\/5\.0 \([^)]+\) AppleWebKit\/[0-9.]+ \(KHTML, like Gecko\) Chrome\/[4-9][0-9].[0-9.]+ (Mobile Safari|Safari)\/[0-9.]+$/',
+			// Firefox 45+
+			'/^Mozilla\/5\.0 \([^)]+\) Gecko\/[0-9.]+ Firefox\/(4[5-9]|[5-9][0-9])\.[0-9.]+$/',
+			// Safari 10+
+			'/^Mozilla\/5\.0 \([^)]+\) AppleWebKit\/[0-9.]+ \(KHTML, like Gecko\) Version\/1[0-9.]+ Safari\/[0-9.A-Z]+$/',
+		];
+
+		if($this->request->isUserAgent($browserWhitelist)) {
+			return true;
+		}
+
+		return false;
+	}
+
 	/**
 	 * Performs the default CSP modifications that may be injected by other
 	 * applications
@@ -190,6 +213,10 @@ class SecurityMiddleware extends Middleware {
 		$defaultPolicy = $this->contentSecurityPolicyManager->getDefaultPolicy();
 		$defaultPolicy = $this->contentSecurityPolicyManager->mergePolicies($defaultPolicy, $policy);
 
+		if($this->browserSupportsCspV3()) {
+			$defaultPolicy->useJsNonce($this->csrfTokenManager->getToken()->getEncryptedValue());
+		}
+
 		$response->setContentSecurityPolicy($defaultPolicy);
 
 		return $response;
diff --git a/lib/private/Security/CSRF/CsrfToken.php b/lib/private/Security/CSRF/CsrfToken.php
index bf61e339f77..dce9a83b727 100644
--- a/lib/private/Security/CSRF/CsrfToken.php
+++ b/lib/private/Security/CSRF/CsrfToken.php
@@ -33,6 +33,8 @@ namespace OC\Security\CSRF;
 class CsrfToken {
 	/** @var string */
 	private $value;
+	/** @var string */
+	private $encryptedValue = '';
 
 	/**
 	 * @param string $value Value of the token. Can be encrypted or not encrypted.
@@ -48,8 +50,12 @@ class CsrfToken {
 	 * @return string
 	 */
 	public function getEncryptedValue() {
-		$sharedSecret = base64_encode(random_bytes(strlen($this->value)));
-		return base64_encode($this->value ^ $sharedSecret) .':'.$sharedSecret;
+		if($this->encryptedValue === '') {
+			$sharedSecret = base64_encode(random_bytes(strlen($this->value)));
+			$this->encryptedValue = base64_encode($this->value ^ $sharedSecret) . ':' . $sharedSecret;
+		}
+
+		return $this->encryptedValue;
 	}
 
 	/**
diff --git a/lib/private/Security/CSRF/CsrfTokenManager.php b/lib/private/Security/CSRF/CsrfTokenManager.php
index d621cc2c29f..b43ca3d3679 100644
--- a/lib/private/Security/CSRF/CsrfTokenManager.php
+++ b/lib/private/Security/CSRF/CsrfTokenManager.php
@@ -34,6 +34,8 @@ class CsrfTokenManager {
 	private $tokenGenerator;
 	/** @var SessionStorage */
 	private $sessionStorage;
+	/** @var CsrfToken|null */
+	private $csrfToken = null;
 
 	/**
 	 * @param CsrfTokenGenerator $tokenGenerator
@@ -51,6 +53,10 @@ class CsrfTokenManager {
 	 * @return CsrfToken
 	 */
 	public function getToken() {
+		if(!is_null($this->csrfToken)) {
+			return $this->csrfToken;
+		}
+
 		if($this->sessionStorage->hasToken()) {
 			$value = $this->sessionStorage->getToken();
 		} else {
@@ -58,7 +64,8 @@ class CsrfTokenManager {
 			$this->sessionStorage->setToken($value);
 		}
 
-		return new CsrfToken($value);
+		$this->csrfToken = new CsrfToken($value);
+		return $this->csrfToken;
 	}
 
 	/**
@@ -69,13 +76,15 @@ class CsrfTokenManager {
 	public function refreshToken() {
 		$value = $this->tokenGenerator->generateToken();
 		$this->sessionStorage->setToken($value);
-		return new CsrfToken($value);
+		$this->csrfToken = new CsrfToken($value);
+		return $this->csrfToken;
 	}
 
 	/**
 	 * Remove the current token from the storage.
 	 */
 	public function removeToken() {
+		$this->csrfToken = null;
 		$this->sessionStorage->removeToken();
 	}
 
diff --git a/lib/public/AppFramework/Http/ContentSecurityPolicy.php b/lib/public/AppFramework/Http/ContentSecurityPolicy.php
index 082aa0206c7..17844497f94 100644
--- a/lib/public/AppFramework/Http/ContentSecurityPolicy.php
+++ b/lib/public/AppFramework/Http/ContentSecurityPolicy.php
@@ -24,8 +24,6 @@
 
 namespace OCP\AppFramework\Http;
 
-use OCP\AppFramework\Http;
-
 /**
  * Class ContentSecurityPolicy is a simple helper which allows applications to
  * modify the Content-Security-Policy sent by ownCloud. Per default only JavaScript,
diff --git a/lib/public/AppFramework/Http/EmptyContentSecurityPolicy.php b/lib/public/AppFramework/Http/EmptyContentSecurityPolicy.php
index 4fca1588e7f..ae4ceef1923 100644
--- a/lib/public/AppFramework/Http/EmptyContentSecurityPolicy.php
+++ b/lib/public/AppFramework/Http/EmptyContentSecurityPolicy.php
@@ -38,6 +38,8 @@ use OCP\AppFramework\Http;
 class EmptyContentSecurityPolicy {
 	/** @var bool Whether inline JS snippets are allowed */
 	protected $inlineScriptAllowed = null;
+	/** @var string Whether JS nonces should be used */
+	protected $useJsNonce = null;
 	/**
 	 * @var bool Whether eval in JS scripts is allowed
 	 * TODO: Disallow per default
@@ -74,6 +76,7 @@ class EmptyContentSecurityPolicy {
 	 * @param bool $state
 	 * @return $this
 	 * @since 8.1.0
+	 * @deprecated 10.0 CSP tokens are now used
 	 */
 	public function allowInlineScript($state = false) {
 		$this->inlineScriptAllowed = $state;
@@ -81,6 +84,18 @@ class EmptyContentSecurityPolicy {
 	}
 
 	/**
+	 * Use the according JS nonce
+	 *
+	 * @param string $nonce
+	 * @return $this
+	 * @since 9.2.0
+	 */
+	public function useJsNonce($nonce) {
+		$this->useJsNonce = $nonce;
+		return $this;
+	}
+
+	/**
 	 * Whether eval in JavaScript is allowed or forbidden
 	 * @param bool $state
 	 * @return $this
@@ -323,6 +338,15 @@ class EmptyContentSecurityPolicy {
 
 		if(!empty($this->allowedScriptDomains) || $this->inlineScriptAllowed || $this->evalScriptAllowed) {
 			$policy .= 'script-src ';
+			if(is_string($this->useJsNonce)) {
+				$policy .= '\'nonce-'.base64_encode($this->useJsNonce).'\'';
+				$allowedScriptDomains = array_flip($this->allowedScriptDomains);
+				unset($allowedScriptDomains['\'self\'']);
+				$this->allowedScriptDomains = array_flip($allowedScriptDomains);
+				if(count($allowedScriptDomains) !== 0) {
+					$policy .= ' ';
+				}
+			}
 			if(is_array($this->allowedScriptDomains)) {
 				$policy .= implode(' ', $this->allowedScriptDomains);
 			}
diff --git a/tests/lib/AppFramework/Http/EmptyContentSecurityPolicyTest.php b/tests/lib/AppFramework/Http/EmptyContentSecurityPolicyTest.php
index 248c3d808d2..33e2315ed89 100644
--- a/tests/lib/AppFramework/Http/EmptyContentSecurityPolicyTest.php
+++ b/tests/lib/AppFramework/Http/EmptyContentSecurityPolicyTest.php
@@ -427,4 +427,28 @@ class EmptyContentSecurityPolicyTest extends \Test\TestCase {
 		$this->contentSecurityPolicy->disallowChildSrcDomain('www.owncloud.org')->disallowChildSrcDomain('www.owncloud.com');
 		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
 	}
+
+	public function testGetPolicyWithJsNonceAndScriptDomains() {
+		$expectedPolicy = "default-src 'none';script-src 'nonce-TXlKc05vbmNl' www.nextcloud.com www.nextcloud.org";
+
+		$this->contentSecurityPolicy->addAllowedScriptDomain('www.nextcloud.com');
+		$this->contentSecurityPolicy->useJsNonce('MyJsNonce');
+		$this->contentSecurityPolicy->addAllowedScriptDomain('www.nextcloud.org');
+		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
+	}
+
+	public function testGetPolicyWithJsNonceAndSelfScriptDomain() {
+		$expectedPolicy = "default-src 'none';script-src 'nonce-TXlKc05vbmNl'";
+
+		$this->contentSecurityPolicy->useJsNonce('MyJsNonce');
+		$this->contentSecurityPolicy->addAllowedScriptDomain("'self'");
+		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
+	}
+
+	public function testGetPolicyWithoutJsNonceAndSelfScriptDomain() {
+		$expectedPolicy = "default-src 'none';script-src 'self'";
+
+		$this->contentSecurityPolicy->addAllowedScriptDomain("'self'");
+		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
+	}
 }
diff --git a/tests/lib/AppFramework/Middleware/Security/SecurityMiddlewareTest.php b/tests/lib/AppFramework/Middleware/Security/SecurityMiddlewareTest.php
index 55bf3e46e07..b597317fca4 100644
--- a/tests/lib/AppFramework/Middleware/Security/SecurityMiddlewareTest.php
+++ b/tests/lib/AppFramework/Middleware/Security/SecurityMiddlewareTest.php
@@ -36,6 +36,8 @@ use OC\AppFramework\Middleware\Security\SecurityMiddleware;
 use OC\AppFramework\Utility\ControllerMethodReflector;
 use OC\Security\CSP\ContentSecurityPolicy;
 use OC\Security\CSP\ContentSecurityPolicyManager;
+use OC\Security\CSRF\CsrfToken;
+use OC\Security\CSRF\CsrfTokenManager;
 use OCP\AppFramework\Controller;
 use OCP\AppFramework\Http\EmptyContentSecurityPolicy;
 use OCP\AppFramework\Http\RedirectResponse;
@@ -72,6 +74,8 @@ class SecurityMiddlewareTest extends \Test\TestCase {
 	private $urlGenerator;
 	/** @var ContentSecurityPolicyManager|\PHPUnit_Framework_MockObject_MockObject */
 	private $contentSecurityPolicyManager;
+	/** @var CsrfTokenManager|\PHPUnit_Framework_MockObject_MockObject */
+	private $csrfTokenManager;
 
 	protected function setUp() {
 		parent::setUp();
@@ -83,6 +87,7 @@ class SecurityMiddlewareTest extends \Test\TestCase {
 		$this->urlGenerator = $this->createMock(IURLGenerator::class);
 		$this->request = $this->createMock(IRequest::class);
 		$this->contentSecurityPolicyManager = $this->createMock(ContentSecurityPolicyManager::class);
+		$this->csrfTokenManager = $this->createMock(CsrfTokenManager::class);
 		$this->middleware = $this->getMiddleware(true, true);
 		$this->secException = new SecurityException('hey', false);
 		$this->secAjaxException = new SecurityException('hey', true);
@@ -103,7 +108,8 @@ class SecurityMiddlewareTest extends \Test\TestCase {
 			'files',
 			$isLoggedIn,
 			$isAdminUser,
-			$this->contentSecurityPolicyManager
+			$this->contentSecurityPolicyManager,
+			$this->csrfTokenManager
 		);
 	}
 
@@ -553,6 +559,10 @@ class SecurityMiddlewareTest extends \Test\TestCase {
 	}
 
 	public function testAfterController() {
+		$this->request
+			->expects($this->once())
+			->method('isUserAgent')
+			->willReturn(false);
 		$response = $this->createMock(Response::class);
 		$defaultPolicy = new ContentSecurityPolicy();
 		$defaultPolicy->addAllowedImageDomain('defaultpolicy');
@@ -591,4 +601,45 @@ class SecurityMiddlewareTest extends \Test\TestCase {
 
 		$this->middleware->afterController($this->controller, 'test', $response);
 	}
+
+	public function testAfterControllerWithContentSecurityPolicy3Support() {
+		$this->request
+			->expects($this->once())
+			->method('isUserAgent')
+			->willReturn(true);
+		$token = $this->createMock(CsrfToken::class);
+		$token
+			->expects($this->once())
+			->method('getEncryptedValue')
+			->willReturn('MyEncryptedToken');
+		$this->csrfTokenManager
+			->expects($this->once())
+			->method('getToken')
+			->willReturn($token);
+		$response = $this->createMock(Response::class);
+		$defaultPolicy = new ContentSecurityPolicy();
+		$defaultPolicy->addAllowedImageDomain('defaultpolicy');
+		$currentPolicy = new ContentSecurityPolicy();
+		$currentPolicy->addAllowedConnectDomain('currentPolicy');
+		$mergedPolicy = new ContentSecurityPolicy();
+		$mergedPolicy->addAllowedMediaDomain('mergedPolicy');
+		$response
+			->expects($this->exactly(2))
+			->method('getContentSecurityPolicy')
+			->willReturn($currentPolicy);
+		$this->contentSecurityPolicyManager
+			->expects($this->once())
+			->method('getDefaultPolicy')
+			->willReturn($defaultPolicy);
+		$this->contentSecurityPolicyManager
+			->expects($this->once())
+			->method('mergePolicies')
+			->with($defaultPolicy, $currentPolicy)
+			->willReturn($mergedPolicy);
+		$response->expects($this->once())
+			->method('setContentSecurityPolicy')
+			->with($mergedPolicy);
+
+		$this->assertEquals($response, $this->middleware->afterController($this->controller, 'test', $response));
+	}
 }
diff --git a/tests/lib/Security/CSRF/CsrfTokenManagerTest.php b/tests/lib/Security/CSRF/CsrfTokenManagerTest.php
index ab19a43e91e..6f7842fdfd9 100644
--- a/tests/lib/Security/CSRF/CsrfTokenManagerTest.php
+++ b/tests/lib/Security/CSRF/CsrfTokenManagerTest.php
@@ -56,6 +56,22 @@ class CsrfTokenManagerTest extends \Test\TestCase {
 		$this->assertEquals($expected, $this->csrfTokenManager->getToken());
 	}
 
+	public function testGetTokenWithExistingTokenKeepsOnSecondRequest() {
+		$this->storageInterface
+			->expects($this->once())
+			->method('hasToken')
+			->willReturn(true);
+		$this->storageInterface
+			->expects($this->once())
+			->method('getToken')
+			->willReturn('MyExistingToken');
+
+		$expected = new \OC\Security\CSRF\CsrfToken('MyExistingToken');
+		$token = $this->csrfTokenManager->getToken();
+		$this->assertSame($token, $this->csrfTokenManager->getToken());
+		$this->assertSame($token, $this->csrfTokenManager->getToken());
+	}
+
 	public function testGetTokenWithoutExistingToken() {
 		$this->storageInterface
 			->expects($this->once())
diff --git a/tests/lib/Security/CSRF/CsrfTokenTest.php b/tests/lib/Security/CSRF/CsrfTokenTest.php
index da640ce5052..d19d1de916c 100644
--- a/tests/lib/Security/CSRF/CsrfTokenTest.php
+++ b/tests/lib/Security/CSRF/CsrfTokenTest.php
@@ -28,6 +28,13 @@ class CsrfTokenTest extends \Test\TestCase {
 		$this->assertSame(':', $csrfToken->getEncryptedValue()[16]);
 	}
 
+	public function testGetEncryptedValueStaysSameOnSecondRequest() {
+		$csrfToken = new \OC\Security\CSRF\CsrfToken('MyCsrfToken');
+		$tokenValue = $csrfToken->getEncryptedValue();
+		$this->assertSame($tokenValue, $csrfToken->getEncryptedValue());
+		$this->assertSame($tokenValue, $csrfToken->getEncryptedValue());
+	}
+
 	public function testGetDecryptedValue() {
 		$csrfToken = new \OC\Security\CSRF\CsrfToken('XlQhHjgWCgBXAEI0Khl+IQEiCXN2LUcDHAQTQAc1HQs=:qgkUlg8l3m8WnkOG4XM9Az33pAt1vSVMx4hcJFsxdqc=');
 		$this->assertSame('/3JKTq2ldmzcDr1f5zDJ7Wt0lEgqqfKF', $csrfToken->getDecryptedValue());