Add public API to give developers the possibility to adjust the global CSP defaults

Allows to inject something into the default content policy. This is for
example useful when you're injecting Javascript code into a view belonging
to another controller and cannot modify its Content-Security-Policy itself.
Note that the adjustment is only applied to applications that use AppFramework
controllers.

To use this from your `app.php` use `\OC::$server->getContentSecurityPolicyManager()->addDefaultPolicy($policy)`,
$policy has to be of type `\OCP\AppFramework\Http\ContentSecurityPolicy`.

To test this add something like the following into an `app.php` of any enabled app:
```
$manager = \OC::$server->getContentSecurityPolicyManager();
$policy = new \OCP\AppFramework\Http\ContentSecurityPolicy(false);
$policy->addAllowedFrameDomain('asdf');
$policy->addAllowedScriptDomain('yolo.com');

$policy->allowInlineScript(false);
$manager->addDefaultPolicy($policy);
$policy = new \OCP\AppFramework\Http\ContentSecurityPolicy(false);
$policy->addAllowedFontDomain('yolo.com');
$manager->addDefaultPolicy($policy);

$policy = new \OCP\AppFramework\Http\ContentSecurityPolicy(false);
$policy->addAllowedFrameDomain('banana.com');
$manager->addDefaultPolicy($policy);
```

If you now open the files app the policy should be:

```
Content-Security-Policy:default-src 'none';script-src yolo.com 'self' 'unsafe-eval';style-src 'self' 'unsafe-inline';img-src 'self' data: blob:;font-src yolo.com 'self';connect-src 'self';media-src 'self';frame-src asdf banana.com 'self'
```

3 files changed, 401 insertions, 323 deletions

diff --git a/lib/public/appframework/controller.php b/lib/public/appframework/controller.php
index 973c9044684..c3744683300 100644
--- a/lib/public/appframework/controller.php
+++ b/lib/public/appframework/controller.php
@@ -72,7 +72,7 @@ abstract class Controller {
 	 * @since 6.0.0 - parameter $appName was added in 7.0.0 - parameter $app was removed in 7.0.0
 	 */
 	public function __construct($appName,
-	                            IRequest $request){
+	                            IRequest $request) {
 		$this->appName = $appName;
 		$this->request = $request;
 
diff --git a/lib/public/appframework/http/contentsecuritypolicy.php b/lib/public/appframework/http/contentsecuritypolicy.php
index 35da4f05e80..7762ca809a2 100644
--- a/lib/public/appframework/http/contentsecuritypolicy.php
+++ b/lib/public/appframework/http/contentsecuritypolicy.php
@@ -38,17 +38,17 @@ use OCP\AppFramework\Http;
  * @package OCP\AppFramework\Http
  * @since 8.1.0
  */
-class ContentSecurityPolicy {
+class ContentSecurityPolicy extends EmptyContentSecurityPolicy {
 	/** @var bool Whether inline JS snippets are allowed */
-	private $inlineScriptAllowed = false;
+	protected $inlineScriptAllowed = false;
 	/**
 	 * @var bool Whether eval in JS scripts is allowed
 	 * TODO: Disallow per default
 	 * @link https://github.com/owncloud/core/issues/11925
 	 */
-	private $evalScriptAllowed = true;
+	protected $evalScriptAllowed = true;
 	/** @var array Domains from which scripts can get loaded */
-	private $allowedScriptDomains = [
+	protected $allowedScriptDomains = [
 		'\'self\'',
 	];
 	/**
@@ -56,342 +56,33 @@ class ContentSecurityPolicy {
 	 * TODO: Disallow per default
 	 * @link https://github.com/owncloud/core/issues/13458
 	 */
-	private $inlineStyleAllowed = true;
+	protected $inlineStyleAllowed = true;
 	/** @var array Domains from which CSS can get loaded */
-	private $allowedStyleDomains = [
+	protected $allowedStyleDomains = [
 		'\'self\'',
 	];
 	/** @var array Domains from which images can get loaded */
-	private $allowedImageDomains = [
+	protected $allowedImageDomains = [
 		'\'self\'',
 		'data:',
 		'blob:',
 	];
 	/** @var array Domains to which connections can be done */
-	private $allowedConnectDomains = [
+	protected $allowedConnectDomains = [
 		'\'self\'',
 	];
 	/** @var array Domains from which media elements can be loaded */
-	private $allowedMediaDomains = [
+	protected $allowedMediaDomains = [
 		'\'self\'',
 	];
 	/** @var array Domains from which object elements can be loaded */
-	private $allowedObjectDomains = [];
+	protected $allowedObjectDomains = [];
 	/** @var array Domains from which iframes can be loaded */
-	private $allowedFrameDomains = [];
+	protected $allowedFrameDomains = [];
 	/** @var array Domains from which fonts can be loaded */
-	private $allowedFontDomains = [
+	protected $allowedFontDomains = [
 		'\'self\'',
 	];
 	/** @var array Domains from which web-workers and nested browsing content can load elements */
-	private $allowedChildSrcDomains = [];
-
-	/**
-	 * Whether inline JavaScript snippets are allowed or forbidden
-	 * @param bool $state
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function allowInlineScript($state = false) {
-		$this->inlineScriptAllowed = $state;
-		return $this;
-	}
-
-	/**
-	 * Whether eval in JavaScript is allowed or forbidden
-	 * @param bool $state
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function allowEvalScript($state = true) {
-		$this->evalScriptAllowed = $state;
-		return $this;
-	}
-
-	/**
-	 * Allows to execute JavaScript files from a specific domain. Use * to
-	 * allow JavaScript from all domains.
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedScriptDomain($domain) {
-		$this->allowedScriptDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed script domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowScriptDomain($domain) {
-		$this->allowedScriptDomains = array_diff($this->allowedScriptDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * Whether inline CSS snippets are allowed or forbidden
-	 * @param bool $state
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function allowInlineStyle($state = true) {
-		$this->inlineStyleAllowed = $state;
-		return $this;
-	}
-
-	/**
-	 * Allows to execute CSS files from a specific domain. Use * to allow
-	 * CSS from all domains.
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedStyleDomain($domain) {
-		$this->allowedStyleDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed style domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowStyleDomain($domain) {
-		$this->allowedStyleDomains = array_diff($this->allowedStyleDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * Allows using fonts from a specific domain. Use * to allow
-	 * fonts from all domains.
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedFontDomain($domain) {
-		$this->allowedFontDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed font domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowFontDomain($domain) {
-		$this->allowedFontDomains = array_diff($this->allowedFontDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * Allows embedding images from a specific domain. Use * to allow
-	 * images from all domains.
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedImageDomain($domain) {
-		$this->allowedImageDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed image domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowImageDomain($domain) {
-		$this->allowedImageDomains = array_diff($this->allowedImageDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * To which remote domains the JS connect to.
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedConnectDomain($domain) {
-		$this->allowedConnectDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed connect domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowConnectDomain($domain) {
-		$this->allowedConnectDomains = array_diff($this->allowedConnectDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * From which domains media elements can be embedded.
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedMediaDomain($domain) {
-		$this->allowedMediaDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed media domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowMediaDomain($domain) {
-		$this->allowedMediaDomains = array_diff($this->allowedMediaDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * From which domains objects such as <object>, <embed> or <applet> are executed
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedObjectDomain($domain) {
-		$this->allowedObjectDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed object domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowObjectDomain($domain) {
-		$this->allowedObjectDomains = array_diff($this->allowedObjectDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * Which domains can be embedded in an iframe
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedFrameDomain($domain) {
-		$this->allowedFrameDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed frame domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowFrameDomain($domain) {
-		$this->allowedFrameDomains = array_diff($this->allowedFrameDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * Domains from which web-workers and nested browsing content can load elements
-	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function addAllowedChildSrcDomain($domain) {
-		$this->allowedChildSrcDomains[] = $domain;
-		return $this;
-	}
-
-	/**
-	 * Remove the specified allowed child src domain from the allowed domains.
-	 *
-	 * @param string $domain
-	 * @return $this
-	 * @since 8.1.0
-	 */
-	public function disallowChildSrcDomain($domain) {
-		$this->allowedChildSrcDomains = array_diff($this->allowedChildSrcDomains, [$domain]);
-		return $this;
-	}
-
-	/**
-	 * Get the generated Content-Security-Policy as a string
-	 * @return string
-	 * @since 8.1.0
-	 */
-	public function buildPolicy() {
-		$policy = "default-src 'none';";
-
-		if(!empty($this->allowedScriptDomains)) {
-			$policy .= 'script-src ' . implode(' ', $this->allowedScriptDomains);
-			if($this->inlineScriptAllowed) {
-				$policy .= ' \'unsafe-inline\'';
-			}
-			if($this->evalScriptAllowed) {
-				$policy .= ' \'unsafe-eval\'';
-			}
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedStyleDomains)) {
-			$policy .= 'style-src ' . implode(' ', $this->allowedStyleDomains);
-			if($this->inlineStyleAllowed) {
-				$policy .= ' \'unsafe-inline\'';
-			}
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedImageDomains)) {
-			$policy .= 'img-src ' . implode(' ', $this->allowedImageDomains);
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedFontDomains)) {
-			$policy .= 'font-src ' . implode(' ', $this->allowedFontDomains);
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedConnectDomains)) {
-			$policy .= 'connect-src ' . implode(' ', $this->allowedConnectDomains);
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedMediaDomains)) {
-			$policy .= 'media-src ' . implode(' ', $this->allowedMediaDomains);
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedObjectDomains)) {
-			$policy .= 'object-src ' . implode(' ', $this->allowedObjectDomains);
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedFrameDomains)) {
-			$policy .= 'frame-src ' . implode(' ', $this->allowedFrameDomains);
-			$policy .= ';';
-		}
-
-		if(!empty($this->allowedChildSrcDomains)) {
-			$policy .= 'child-src ' . implode(' ', $this->allowedChildSrcDomains);
-			$policy .= ';';
-		}
-
-		return rtrim($policy, ';');
-	}
+	protected $allowedChildSrcDomains = [];
 }
diff --git a/lib/public/appframework/http/emptycontentsecuritypolicy.php b/lib/public/appframework/http/emptycontentsecuritypolicy.php
new file mode 100644
index 00000000000..33860dcdb0f
--- /dev/null
+++ b/lib/public/appframework/http/emptycontentsecuritypolicy.php
@@ -0,0 +1,387 @@
+<?php
+/**
+ * @author Lukas Reschke <lukas@owncloud.com>
+ * @author Morris Jobke <hey@morrisjobke.de>
+ * @author sualko <klaus@jsxc.org>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * 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, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCP\AppFramework\Http;
+
+use OCP\AppFramework\Http;
+
+/**
+ * Class EmptyContentSecurityPolicy is a simple helper which allows applications
+ * to modify the Content-Security-Policy sent by ownCloud. Per default the policy
+ * is forbidding everything.
+ *
+ * As alternative with sane exemptions look at ContentSecurityPolicy
+ *
+ * @see \OCP\AppFramework\Http\ContentSecurityPolicy
+ * @package OCP\AppFramework\Http
+ * @since 9.0.0
+ */
+class EmptyContentSecurityPolicy {
+	/** @var bool Whether inline JS snippets are allowed */
+	protected $inlineScriptAllowed = null;
+	/**
+	 * @var bool Whether eval in JS scripts is allowed
+	 * TODO: Disallow per default
+	 * @link https://github.com/owncloud/core/issues/11925
+	 */
+	protected $evalScriptAllowed = null;
+	/** @var array Domains from which scripts can get loaded */
+	protected $allowedScriptDomains = null;
+	/**
+	 * @var bool Whether inline CSS is allowed
+	 * TODO: Disallow per default
+	 * @link https://github.com/owncloud/core/issues/13458
+	 */
+	protected $inlineStyleAllowed = null;
+	/** @var array Domains from which CSS can get loaded */
+	protected $allowedStyleDomains = null;
+	/** @var array Domains from which images can get loaded */
+	protected $allowedImageDomains = null;
+	/** @var array Domains to which connections can be done */
+	protected $allowedConnectDomains = null;
+	/** @var array Domains from which media elements can be loaded */
+	protected $allowedMediaDomains = null;
+	/** @var array Domains from which object elements can be loaded */
+	protected $allowedObjectDomains = null;
+	/** @var array Domains from which iframes can be loaded */
+	protected $allowedFrameDomains = null;
+	/** @var array Domains from which fonts can be loaded */
+	protected $allowedFontDomains = null;
+	/** @var array Domains from which web-workers and nested browsing content can load elements */
+	protected $allowedChildSrcDomains = null;
+
+	/**
+	 * Whether inline JavaScript snippets are allowed or forbidden
+	 * @param bool $state
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function allowInlineScript($state = false) {
+		$this->inlineScriptAllowed = $state;
+		return $this;
+	}
+
+	/**
+	 * Whether eval in JavaScript is allowed or forbidden
+	 * @param bool $state
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function allowEvalScript($state = true) {
+		$this->evalScriptAllowed = $state;
+		return $this;
+	}
+
+	/**
+	 * Allows to execute JavaScript files from a specific domain. Use * to
+	 * allow JavaScript from all domains.
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedScriptDomain($domain) {
+		$this->allowedScriptDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed script domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowScriptDomain($domain) {
+		$this->allowedScriptDomains = array_diff($this->allowedScriptDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * Whether inline CSS snippets are allowed or forbidden
+	 * @param bool $state
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function allowInlineStyle($state = true) {
+		$this->inlineStyleAllowed = $state;
+		return $this;
+	}
+
+	/**
+	 * Allows to execute CSS files from a specific domain. Use * to allow
+	 * CSS from all domains.
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedStyleDomain($domain) {
+		$this->allowedStyleDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed style domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowStyleDomain($domain) {
+		$this->allowedStyleDomains = array_diff($this->allowedStyleDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * Allows using fonts from a specific domain. Use * to allow
+	 * fonts from all domains.
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedFontDomain($domain) {
+		$this->allowedFontDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed font domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowFontDomain($domain) {
+		$this->allowedFontDomains = array_diff($this->allowedFontDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * Allows embedding images from a specific domain. Use * to allow
+	 * images from all domains.
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedImageDomain($domain) {
+		$this->allowedImageDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed image domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowImageDomain($domain) {
+		$this->allowedImageDomains = array_diff($this->allowedImageDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * To which remote domains the JS connect to.
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedConnectDomain($domain) {
+		$this->allowedConnectDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed connect domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowConnectDomain($domain) {
+		$this->allowedConnectDomains = array_diff($this->allowedConnectDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * From which domains media elements can be embedded.
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedMediaDomain($domain) {
+		$this->allowedMediaDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed media domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowMediaDomain($domain) {
+		$this->allowedMediaDomains = array_diff($this->allowedMediaDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * From which domains objects such as <object>, <embed> or <applet> are executed
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedObjectDomain($domain) {
+		$this->allowedObjectDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed object domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowObjectDomain($domain) {
+		$this->allowedObjectDomains = array_diff($this->allowedObjectDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * Which domains can be embedded in an iframe
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedFrameDomain($domain) {
+		$this->allowedFrameDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed frame domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowFrameDomain($domain) {
+		$this->allowedFrameDomains = array_diff($this->allowedFrameDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * Domains from which web-workers and nested browsing content can load elements
+	 * @param string $domain Domain to whitelist. Any passed value needs to be properly sanitized.
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function addAllowedChildSrcDomain($domain) {
+		$this->allowedChildSrcDomains[] = $domain;
+		return $this;
+	}
+
+	/**
+	 * Remove the specified allowed child src domain from the allowed domains.
+	 *
+	 * @param string $domain
+	 * @return $this
+	 * @since 8.1.0
+	 */
+	public function disallowChildSrcDomain($domain) {
+		$this->allowedChildSrcDomains = array_diff($this->allowedChildSrcDomains, [$domain]);
+		return $this;
+	}
+
+	/**
+	 * Get the generated Content-Security-Policy as a string
+	 * @return string
+	 * @since 8.1.0
+	 */
+	public function buildPolicy() {
+		$policy = "default-src 'none';";
+
+		if(!empty($this->allowedScriptDomains) || $this->inlineScriptAllowed || $this->evalScriptAllowed) {
+			$policy .= 'script-src ';
+			if(is_array($this->allowedScriptDomains)) {
+				$policy .= implode(' ', $this->allowedScriptDomains);
+			}
+			if($this->inlineScriptAllowed) {
+				$policy .= ' \'unsafe-inline\'';
+			}
+			if($this->evalScriptAllowed) {
+				$policy .= ' \'unsafe-eval\'';
+			}
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedStyleDomains) || $this->inlineStyleAllowed) {
+			$policy .= 'style-src ';
+			if(is_array($this->allowedStyleDomains)) {
+				$policy .= implode(' ', $this->allowedStyleDomains);
+			}
+			if($this->inlineStyleAllowed) {
+				$policy .= ' \'unsafe-inline\'';
+			}
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedImageDomains)) {
+			$policy .= 'img-src ' . implode(' ', $this->allowedImageDomains);
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedFontDomains)) {
+			$policy .= 'font-src ' . implode(' ', $this->allowedFontDomains);
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedConnectDomains)) {
+			$policy .= 'connect-src ' . implode(' ', $this->allowedConnectDomains);
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedMediaDomains)) {
+			$policy .= 'media-src ' . implode(' ', $this->allowedMediaDomains);
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedObjectDomains)) {
+			$policy .= 'object-src ' . implode(' ', $this->allowedObjectDomains);
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedFrameDomains)) {
+			$policy .= 'frame-src ' . implode(' ', $this->allowedFrameDomains);
+			$policy .= ';';
+		}
+
+		if(!empty($this->allowedChildSrcDomains)) {
+			$policy .= 'child-src ' . implode(' ', $this->allowedChildSrcDomains);
+			$policy .= ';';
+		}
+
+		return rtrim($policy, ';');
+	}
+}