WEBSEC D. Ross Internet-Draft Microsoft Intended status: Informational T. Gondrom Expires: January 16, 2014 Thames Stanley July 15, 2013 HTTP Header Field X-Frame-Options draft-ietf-websec-x-frame-options-05 Abstract To improve the protection of web applications against Clickjacking, this specification describes the X-Frame-Options HTTP response header field that declares a policy communicated from the server to the client browser on whether the browser may display the transmitted content in frames that are part of other web pages. This informational document serves to document the existing use and specification of this X-Frame-Options HTTP response header field. 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. 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Code Components extracted from this document must Ross & Gondrom Expires January 16, 2014 [Page 1] Internet-Draft X-Frame-Options July 2013 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. X-Frame-Options Header . . . . . . . . . . . . . . . . . . . 3 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Augmented Backus-Naur Form (ABNF) . . . . . . . . . . . 4 2.2.1. Examples of X-Frame-Options . . . . . . . . . . . . . 5 2.3. Design Issues . . . . . . . . . . . . . . . . . . . . . . 5 2.3.1. Enable HTML content from other domains . . . . . . . 5 2.3.2. Browser Behaviour and Processing . . . . . . . . . . 5 2.3.2.1. Violation of X-Frame-Options . . . . . . . . . . 5 2.3.2.2. Variation in current browser behaviour . . . . . 6 2.3.2.3. Usage design pattern and example scenario for the ALLOW-FROM parameter . . . . . . . . . . . . . . 6 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4.1. Registration Template . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5.1. Privacy Considreations . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.1. Normative References . . . . . . . . . . . . . . . . . . 8 6.2. Informative References . . . . . . . . . . . . . . . . . 9 Appendix A. Browsers that support X-Frame-Options . . . . . . . 10 Appendix B. Description of a Clickjacking attack . . . . . . . . 10 B.1. Shop . . . . . . . . . . . . . . . . . . . . . . . . . . 10 B.2. Online Shop Confirm Purchase Page . . . . . . . . . . . . 10 B.3. Flash Configuration . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction In 2009 and 2010 many browser vendors ([Microsoft-X-Frame-Options], [CLICK-DEFENSE-BLOG], [Mozilla-X-Frame-Options]) introduced the use of a non-standard HTTP [RFC2616] header field "X-Frame-Options" to protect against Clickjacking [Clickjacking]. HTML-based web applications can embed or "frame" other web pages. Clickjacking is a type of attack that occurs when an attacker uses multiple transparent or opaque layers in the user interface to trick a user into clicking on a button or link on another page from server B when they were intending to click on the same place of the overlaying page from server A. Thus, the attacker is "hijacking" clicks meant for their page A and routing them to another page B, possibly belonging to another domain and thereby triggering actions on the second server B Ross & Gondrom Expires January 16, 2014 [Page 2] Internet-Draft X-Frame-Options July 2013 without the knowledge nor intention of the user and potentially using an existing session context and login in that step. This specification provides informational documentation about the current use and definition of the X-Frame-Options HTTP header field. Given that the "X-" construction is deprecated [RFC6648], the X -Frame-Options header field will in the future be replaced by the Frame-Options directive in the Content Security Policy Version 1.1 [CSP-1-1]. Existing anti-ClickJacking measures, e.g. Frame-breaking Javascript, have weaknesses so that their protection can be circumvented as a study [FRAME-BUSTING] demonstrated. Short of configuring the browser to disable frames and script entirely, which massively impairs browser utility, browser users are vulnerable to this type of attack. "X-Frame-Options" allows 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 ( or