Clickjacking Defense Cheat Sheet

= Clickjacking Defense Introduction =

This cheat sheet is focused on providing developer guidance on Clickjack/UI Redress attack prevention. For more information on the risk of Clickjacking, please visit this page. Additional references on Clickjacking can be found here.

The most popular way to defend against Clickjacking is to include some sort of "frame-breaking" functionality which prevents other web pages from framing the site you wish to defend. This cheat sheet will discuss two methods of implementing frame-breaking: first is X-Frame-Options headers (used if the browser supports the functionality); and second is javascript frame-breaking code.

= Defending with X-Frame-Options response headers =

The X-Frame-Options HTTP response header can be used to indicate whether or not a browser should be allowed to render a page in a &lt;frame&gt; or &lt;iframe&gt;. Sites can use this to avoid Clickjacking attacks, by ensuring that their content is not embedded into other sites.

X-Frame-Options Header Types
There are three possible values for the X-Frame-Options headers:
 * DENY, which prevents any domain from framing the content.
 * SAMEORIGIN, which only allows the current site to frame the content.
 * ALLOW-FROM uri, which permits the specified 'uri' to frame this page. (e.g., ALLOW-FROM http&#58;//www.example.com) The ALLOW-FROM option is a relatively recent addition (circa 2012) and may not be supported by all browsers yet.

Browser Support
The following browsers support X-Frame-Options headers.

References:
 * Mozilla Developer Network
 * IETF Draft

Implementation
To implement this protection, you need to add the header to any page that you want to protect from being clickjacked. One way to do this is to add the header manually to every page. A possibly simpler way is to implement a filter that automatically adds the header to every page.

OWASP has an article and some code that provides all the details for implementing this in the Java EE environment.

The SDL blog has posted an article covering how to implement this in a .NET environment.

Limitations
The policy needs to be specified for every page, which can complicate deployment. Providing the ability to enforce it for the entire site, at login time for instance, could simplify adoption.
 * Per-page policy specification

The current implementation does not allow the webmaster to provide a whitelist of domains that are allowed to frame the page. While whitelisting can be dangerous, in some cases a webmaster might have no choice but to use more than one hostname.
 * Problems with multi-domain sites

Web proxies are notorious for adding and stripping headers. If a web proxy strips the X-Frame-Options header then the site loses its framing protection.
 * Proxies

= Clickjacking defense for legacy browsers =

The following methodology will prevent a webpage from being framed even in legacy browsers.

In the document HEAD element, add the following:

First apply an ID to the style element itself:

&lt;style id=&quot;antiClickjack&quot;&gt;body{display:none !important;}&lt;/style&gt;

And then delete that style by its ID immediately after in the script:

&lt;script type=&quot;text/javascript&quot;&gt; if (self === top) { var antiClickjack = document.getElementById(&quot;antiClickjack&quot;); antiClickjack.parentNode.removeChild(antiClickjack); } else { top.location = self.location; } &lt;/script&gt;

This way, everything can be in the document HEAD and you only need one method/taglib in your API.

Reference: https://www.codemagi.com/blog/post/194

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