X-Frame-Options: ALLOW-FROM in firefox and chrome

I'm implementing a "pass-through" for X-Frame-Options to let a partner site wrap my employer's site in an iframe, as per this article:

(splitting up URLS to post)

In a nutshell, our partner's page has an iframe with an URL against our domain. For any page in our domain, they'll add a special url argument like &@mykey=topleveldomain.com, telling us what the page's top level domain is.

Our filters pick up the partner TLD, if provided, from the URL, and validate it against a whitelist. If it's on the list, we ship the X-Frame-Options header with value ALLOW-FROM topleveldomain.com (and add a cookie for future clicks). If it's not on our whitelist, we ship SAMEORIGIN or DENY.

The problem is it looks like sending ALLOW-FROM domain results in a no-op overall for the latest Firefox and Google Chrome. IE8, at least, seems to be correctly implementing ALLOW-FROM.

Check out this page: . Right after the 5th (of 5) boxes that "should be showing content", is a box that should NOT be showing content, but which is. In this case, the page in the iframe is sending X-Frame-Options: ALLOW-FROM , a decidedly different TLD than . Yet, the frame still displays content.

Any insight as to whether X-Frame-Options is truly implemented with ALLOW-FROM across relevant (desktop) browsers? Perhaps the syntax has changed?

Some links of interest:

• Draft rfc on x-frame-options:
• developer.mozilla article discussing the header as a 2-option header (sameorigin or deny).
• msdn blog that initiated the whole thing:
• msdn blog that talks about 3 values: adding allow-from origin

3 Answers

ALLOW-FROM is not supported in Chrome or Safari. See MDN article:

You are already doing the work to make a custom header and send it with the correct data, can you not just exclude the header when you detect it is from a valid partner and add DENY to every other request? I don't see the benefit of AllowFrom when you are already dynamically building the logic up?

I posted this question and never saw the feedback (which came in several months after, it seems :).

As Kinlan mentioned, ALLOW-FROM is not supported in all browsers as an X-Frame-Options value.

The solution was to branch based on browser type. For IE, ship X-Frame-Options. For everyone else, ship X-Content-Security-Policy.

Hope this helps, and sorry for taking so long to close the loop!

For Chrome, instead of

response.AppendHeader("X-Frame-Options", "ALLOW-FROM " + host);

you need to add Content-Security-Policy

string selfAuth = System.Web.HttpContext.Current.Request.Url.Authority;
string refAuth = System.Web.HttpContext.Current.Request.UrlReferrer.Authority;
response.AppendHeader("Content-Security-Policy", "default-src 'self' 'unsafe-inline' 'unsafe-eval' data: *.msecnd.net vortex.data.microsoft.com " + selfAuth + " " + refAuth);

to the HTTP-response-headers.
Note that this assumes you checked on the server whether or not refAuth is allowed.
And also, note that you need to do browser-detection in order to avoid adding the allow-from header for Chrome (outputs error on console).

For details, see my answer here.