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>

2 files changed, 24 insertions, 2 deletions

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);
 			}