WEBSEC D. Ross Internet-Draft Microsoft Intended status: Standards Track T. Gondrom Expires: September 8, 2011 March 7, 2011 HTTP Header Frame Options draft-gondrom-frame-options-00 Abstract To improve the protection of web applications against Cross Site Request Forgery (CSRF) and Clickjacking this standards defines a http response header that declares a policy communicated from a host to the client browser whether the transmitted content MUST NOT be displayed in frames of other pages from different origins or a list of trusted origins which are allowed to frame the content. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 8, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Ross & Gondrom Expires September 8, 2011 [Page 1] Internet-Draft Frame-Options March 2011 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 2. Frame-Options Header . . . . . . . . . . . . . . . . . . . . . 3 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Backus-Naur Form (BNF) . . . . . . . . . . . . . . . . . . 4 2.3. Examples of Frame-Options Headers . . . . . . . . . . . . . 4 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Registration Template . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5 6.2. Informative References . . . . . . . . . . . . . . . . . . 5 Appendix A. Description of a Clickjacking attack . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Ross & Gondrom Expires September 8, 2011 [Page 2] Internet-Draft Frame-Options March 2011 1. Introduction In 2009 and 2010 many browser vendors introduced the use of a non- standard http header RFC 2616 [RFC2616] "X-Frame-Options" to protect against Clickjacking [Clickjacking] and Cross Site Request Forgery (CSRF) [CSRF]. This standard is to replace the non-standard header. With Clickjacking and CSRF an attacker tricks a user into clicking on a button or link to another page and by thus executing an unintended command in the context of a different web application. For example with Clickjacking the attacker might use transparent or opaque layers to integrate and obscure a button to another page so that the user may click on it in the expectation of a different action. So, in this way the attacker is "hijacking" the "Click" on a button meant by the user to be sent to host A, while clicking the button in effect sends a message to host B. If the user does for example also have an open session with host B this can lead to a CSRF attack and executing a command in the session context of the user (using the user's authentication and authorization) on host B without his intention or knowledge. The by "Frame-Options" provided defense mechanism against Clickjacking is to allow a secure web page from host B to declare that its content (for example a button, links, text, etc.) must not be displayed in a frame of another page (e.g. from host A). In principle this is done by a policy declared in the HTTP header and obeyed by conform browser implementations. 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. Frame-Options Header The Frame-Options HTTP response header indicates a policy whether a browser MUST NOT allow to render a page in a or