[websec] comments on -frame-options and -x-frame-options drafts

Chris Weber <chris@lookout.net> Thu, 19 April 2012 00:27 UTC

Return-Path: <chris@lookout.net>
X-Original-To: websec@ietfa.amsl.com
Delivered-To: websec@ietfa.amsl.com
Received: from localhost (localhost []) by ietfa.amsl.com (Postfix) with ESMTP id 2053B21F8460 for <websec@ietfa.amsl.com>; Wed, 18 Apr 2012 17:27:50 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.235
X-Spam-Status: No, score=-2.235 tagged_above=-999 required=5 tests=[AWL=0.365, BAYES_00=-2.599]
Received: from mail.ietf.org ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id 77fX2WA51fiQ for <websec@ietfa.amsl.com>; Wed, 18 Apr 2012 17:27:49 -0700 (PDT)
Received: from n06.mail01.mtsvc.net (mailout08.mail01.mtsvc.net []) by ietfa.amsl.com (Postfix) with ESMTP id 989D121F845C for <websec@ietf.org>; Wed, 18 Apr 2012 17:27:49 -0700 (PDT)
Received: from [] (port=53328 helo=[]) by n06.mail01.mtsvc.net with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.63) (envelope-from <chris@lookout.net>) id 1SKfDw-0006uK-Fk for websec@ietf.org; Wed, 18 Apr 2012 20:27:48 -0400
Message-ID: <4F8F5C05.8010904@lookout.net>
Date: Wed, 18 Apr 2012 17:27:49 -0700
From: Chris Weber <chris@lookout.net>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0) Gecko/20120327 Thunderbird/11.0.1
MIME-Version: 1.0
To: websec <websec@ietf.org>
X-Enigmail-Version: 1.4
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Authenticated-User: 882879 chris@lookout.net
Subject: [websec] comments on -frame-options and -x-frame-options drafts
X-BeenThere: websec@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Web Application Security Minus Authentication and Transport <websec.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/websec>, <mailto:websec-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/websec>
List-Post: <mailto:websec@ietf.org>
List-Help: <mailto:websec-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/websec>, <mailto:websec-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 19 Apr 2012 00:27:50 -0000

Sending this with a new subject as I think my comments could have been
better placed.

I have one nit with these documents - the way they bring Cross Site
Request Forgery (CSRF) into the discussion and positions X-Frame-Options
as a "sometimes" mitigation for CSRF.  We could probably agree that
wording such as "In some forms of Clickjacking and CSRF an attacker
tricks a user into clicking..." sufficiently limits the scope of the
context.  However I feel that CSRF in general is just completely out of
scope - there are many attacks that might leverage framing after all.  I
also worry that some people may be led to believe that the
X-Frame-Options header provides general protection from CSRF when that's
absolutely not the case.

When Microsoft released this functionality with IE8, it was positioned
as a protection against framing attacks, or Clickjacking, and not CSRF.
 I believe that's how many of us in the security community still view it
- it's only a protection against CSRF in cases where framing is required
to execute the CSRF attack.  The two (Clickjacking and CSRF) can only be
linked in that and similar contexts.

I suggest that references to CSRF protection be removed to avoid
confusion or that the wording reflect this narrow scope of the
CSRF-protection (preferably the former).  After all, CSRF is just one
example of many other attacks that could leverage framing - e.g. we
could include answering CAPTCHAs, certain forms of self-side XSS, and
even information disclosure as equivalent forms of attack (like CSRF)
that might leverage framing.

Can we keep the documents focused on the primary design goal -
controlling/preventing framing - and avoid lumping in other forms of
attack that might piggyback on such framing?

Best regards,
Chris Weber