How to override X-Frame-Options for a controller or action in Rails 4

Question

Rails 4 appears to set a default value of SAMEORIGIN for the X-Frame-Options HTTP response header. This is great for security, but it does not allow for parts of your app to be available in an iframe on a different domain.

You can override the value of X-Frame-Options globally using the config.action_dispatch.default_headers setting:

config.action_dispatch.default_headers['X-Frame-Options'] = "ALLOW-FROM https://apps.facebook.com"

But how do you override it for just a single controller or action?

Molnar

Answer 1

If you want to remove the header completely, you can create an after_action filter:

class FilesController < ApplicationController
  after_action :allow_iframe, only: :embed

  def embed
  end

private

  def allow_iframe
    response.headers.except! 'X-Frame-Options'
  end
end

Or, of course, you can code the after_action to set the value to something different:

class FacebookController < ApplicationController
  after_action :allow_facebook_iframe

private

  def allow_facebook_iframe
    response.headers['X-Frame-Options'] = 'ALLOW-FROM https://apps.facebook.com'
  end
end

Note that you need to clear your cache in certain browsers (Chrome for me) while debugging this.

Molnar

How would you get this to work on a redirect_to? (Am trying right now with my Angular app and it is not working) – Depurative

I'd assume that both the action containing the redirect_to and the action that it redirects to would need this to be applied. Are you getting a particular error? Sounds like a good new question on Stack Overflow! – Molnar

I realized I had the after_action before it was redirected to the final controller action that redirects to the Angular routes. Thank you! – Depurative

It is not required to do this in an after_action, though it is handy to do so e.g. in a Frontend::BaseController where it applies to the whole frontend. You may as well run response.headers.except! ... within an action. – Perineum

As of now, not working in Chrome. Console error is "Invalid 'X-Frame-Options' header encountered when loading 'child': 'ALLOW-FROM parent' is not a recognized directive. The header will be ignored." Marked as won't fix in Chromium, with an alternative: "'frame-ancestors' is shipping in both Chrome and Firefox, and is the right way to support this functionality." bugs.chromium.org/p/chromium/issues/detail?id=129139 – Warhead

Answer 2

I just wanted to include an updated answer here for anyone who finds this link when trying to figure out how to allow your Rails app to be embedded in an I-Frame and running into issues.

As of writing this, May 28th 2020, the X-Frame-Options changes are probably not your best solution to your problem. The "ALLOW-FROM" option has been totally disallowed by all major browsers.

The modern solution is to implement a Content-Security-Policy and set a 'frame_ancestors' policy. The 'frame_ancestors' key designates what domains can embed your app as an iframe. Its currently supported by major browsers and overrides your X-Frame-Options. This will allow you to prevent Clickjacking (which the X-Frame-Options was originally intended to help with before it largely became deprecated) and lock down your app in a modern environment.

You can set up a Content-Security-Policy with Rails 5.2 in an initializer (example below), and for Rails < 5.2 you can use a gem like the Secure Headers gem: https://github.com/github/secure_headers

You can also override the policy specifications on a controller/action basis if you'd like.

Content-Security-Policies are great for advanced security protections. Check out all the things you can configure in the Rails docs: https://edgeguides.rubyonrails.org/security.html

A Rails 5.2 example for a Content-Security-Policy:

# config/initializers/content_security_policy.rb    
    Rails.application.config.content_security_policy do |policy|
      policy.frame_ancestors :self, 'some_website_that_embeds_your_app.com'
    end

An example of a controller specific change to a policy:

# Override policy inline
class PostsController < ApplicationController
  content_security_policy do |p|
    p.frame_ancestors :self, 'some_other_website_that_can_embed_posts.com'
  end
end

Maddy

Can also use a lambda for dynamic values: p.frame_ancestors :self, -> { company&.allowed_domain || 'none' } – Windowlight

I'm using frame_ancestors and it works in every browser, but Safari. Any insight? – Photoelectric

@Photoelectric - I believe Safari currently prevents 3rd party iframes from storing cookies - this is a major limitation of using iframes in Safari and may be the cause of your issue. As far as I know there are no good work-arounds. Check this stack overflow for more information: #59723556 – Maddy

Guys, what is the way to allow to be embedded for any domain using the 'content security policy'? #71115547 – Troy

Answer 3

The answers above really helped me, but in 2021 using a Rails 4.2 app I needed to turn off X-Frame-Options and specify a Content-Security-Policy for only a couple URLs.

Specifically I am using 2checkout as a payment provider and they open up some URLs in iframes....

This is how I did it

class HomeController < ApplicationController
    after_action :allow_2checkout_iframe, only: [:privacy, :terms_of_service]

    def privacy
    end

    def terms_of_service
    end

    private
        def allow_2checkout_iframe
            response.headers.except! 'X-Frame-Options'
            response.headers['Content-Security-Policy'] = "frame-ancestors 'self' https://secure.2checkout.com"
        end
end

Ignaz

Answer 4

For Rails 5+, use response.set_header('X-Frame-Options', 'ALLOW-FROM https://apps.facebook.com') instead. Or if ALLOW-FROM doesn't work and you need a quick fix, you can set it to ALLOWALL

Tav

Both these options (ALLOW-FROM and ALLOWALL) are not valid anymore: developer.mozilla.org/en-US/docs/Web/HTTP/Headers/… – Dunton