feat: Provide CSP nonce as <meta> element

This way we use the CSP nonce for dynamically loaded scripts.
Important to notice: The CSP nonce must NOT be injected in `content` as
this can lead to value exfiltration using e.g. side-channel attacts (CSS selectors).

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

core/templates/layout.base.php

@@ -14,6 +14,7 @@
 		</title>
 		<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
 		<meta name="theme-color" content="<?php p($theme->getColorPrimary()); ?>">
+		<meta name="csp-nonce" nonce="<?php p($_['cspNonce']); /* Do not pass into "content" to prevent exfiltration */ ?>">
 		<link rel="icon" href="<?php print_unescaped(image_path('core', 'favicon.ico')); /* IE11+ supports png */ ?>">
 		<link rel="apple-touch-icon" href="<?php print_unescaped(image_path('core', 'favicon-touch.png')); ?>">
 		<link rel="mask-icon" sizes="any" href="<?php print_unescaped(image_path('core', 'favicon-mask.svg')); ?>" color="<?php p($theme->getColorPrimary()); ?>">

core/templates/layout.guest.php

@@ -19,6 +19,7 @@
 p($theme->getTitle());
 ?>
 		</title>
+		<meta name="csp-nonce" nonce="<?php p($_['cspNonce']); /* Do not pass into "content" to prevent exfiltration */ ?>">
 		<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
 		<?php if ($theme->getiTunesAppId() !== '') { ?>
 		<meta name="apple-itunes-app" content="app-id=<?php p($theme->getiTunesAppId()); ?>">

core/templates/layout.initial-state.php

@@ -5,7 +5,7 @@
  */
 ?>
 <div id="initial-state-container" style="display: none;">
-    <?php foreach ($_['initialStates'] as $app => $initialState) { ?>
-        <input type="hidden" id="initial-state-<?php p($app); ?>" value="<?php p(base64_encode($initialState)); ?>">
-    <?php }?>
+	<?php foreach ($_['initialStates'] as $app => $initialState) { ?>
+		<input type="hidden" id="initial-state-<?php p($app); ?>" value="<?php p(base64_encode($initialState)); ?>">
+	<?php }?>
 </div>

core/templates/layout.public.php

@@ -14,6 +14,7 @@
 p($theme->getTitle());
 ?>
 	</title>
+	<meta name="csp-nonce" nonce="<?php p($_['cspNonce']); /* Do not pass into "content" to prevent exfiltration */ ?>">
 	<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
 	<?php if ($theme->getiTunesAppId() !== '') { ?>
 	<meta name="apple-itunes-app" content="app-id=<?php p($theme->getiTunesAppId()); ?>">

core/templates/layout.user.php

@@ -29,6 +29,7 @@
 p($theme->getTitle());
 ?>
 		</title>
+		<meta name="csp-nonce" nonce="<?php p($_['cspNonce']); /* Do not pass into "content" to prevent exfiltration */ ?>">
 		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
 
 		<?php if ($theme->getiTunesAppId() !== '') { ?>

lib/private/Security/CSP/ContentSecurityPolicyNonceManager.php

@@ -33,7 +33,8 @@ public function getNonce(): string {
 				// Get the token from the CSRF token, we only use the "shared secret" part
 				// as the first part does not add any security / entropy to the token
 				// so it can be ignored to keep the nonce short while keeping the same randomness
-				$this->nonce = end(explode(':', ($this->csrfTokenManager->getToken()->getEncryptedValue())));
+				$csrfSecret = explode(':', ($this->csrfTokenManager->getToken()->getEncryptedValue()));
+				$this->nonce = end($csrfSecret);
 			} else {
 				$this->nonce = $this->request->server['CSP_NONCE'];
 			}

lib/private/Template/Base.php

@@ -24,11 +24,14 @@ class Base {
 	 * @param string $template
 	 * @param string $requestToken
 	 * @param \OCP\IL10N $l10n
+	 * @param string $cspNonce
 	 * @param Defaults $theme
 	 */
-	public function __construct($template, $requestToken, $l10n, $theme) {
-		$this->vars = [];
-		$this->vars['requesttoken'] = $requestToken;
+	public function __construct($template, $requestToken, $l10n, $theme, $cspNonce) {
+		$this->vars = [
+			'cspNonce' => $cspNonce,
+			'requesttoken' => $requestToken,
+		];
 		$this->l10n = $l10n;
 		$this->template = $template;
 		$this->theme = $theme;

lib/private/legacy/OC_Template.php

@@ -43,6 +43,7 @@ public function __construct($app, $name, $renderAs = TemplateResponse::RENDER_AS
 		$theme = OC_Util::getTheme();
 
 		$requestToken = (OC::$server->getSession() && $registerCall) ? \OCP\Util::callRegister() : '';
+		$cspNonce = \OCP\Server::get(\OC\Security\CSP\ContentSecurityPolicyNonceManager::class)->getNonce();
 
 		$parts = explode('/', $app); // fix translation when app is something like core/lostpassword
 		$l10n = \OC::$server->getL10N($parts[0]);
@@ -56,7 +57,13 @@ public function __construct($app, $name, $renderAs = TemplateResponse::RENDER_AS
 		$this->path = $path;
 		$this->app = $app;
 
-		parent::__construct($template, $requestToken, $l10n, $themeDefaults);
+		parent::__construct(
+			$template,
+			$requestToken,
+			$l10n,
+			$themeDefaults,
+			$cspNonce,
+		);
 	}