Network Working Group Y. Nir, Ed. Internet-Draft Check Point Updates: 6454 (if approved) February 2, 2012 Intended status: Standards Track Expires: August 5, 2012 A More Granular Web Origin Concept draft-nir-websec-extended-origin-00 Abstract This document defines an HTTP header that allows to partition a single origin as defined in RFC 6454 into multiple origins, so that the same origin policy applies among them. The header introduced in this document allows the portal to specify that resources that appear to be from the same origin should, in fact, be treated as though they are from different origins, by extending the 3-tuple of the origin to a 4-tuple. The user agent is expected to apply the same-origin policy according to the 4-tuple rather than the 3-tuple. 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 August 5, 2012. Copyright Notice Copyright (c) 2012 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 Nir Expires August 5, 2012 [Page 1] Internet-Draft Extended Origin February 2012 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 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . . 3 2. The Extended-Origin Header . . . . . . . . . . . . . . . . . . 3 2.1. Header Format . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Update to the Serialization Requirements . . . . . . . . . 4 3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. CORS interaction . . . . . . . . . . . . . . . . . . . . . . . 6 5. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. Other Methods of Encoding Server Identity . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 9. Changes from Previous Versions . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Nir Expires August 5, 2012 [Page 2] Internet-Draft Extended Origin February 2012 1. Introduction Web portals such as SSL VPNs "flatten" the Web by providing access to multiple web sites through a single host. For example, a company portal may be located at https://sslvpn.example.com, and allow remote access to several websites that form the corporate intranet as well as webified access to the mail server. The different services are distinguised by implementation-specific manipulation of the URL. For example, the following three URLs may be respectively for the internal mail server, for the internal wiki, and for Wikipedia: 1. https://sslvpn.example.com/link/my_web_mail/inbox/index.html 2. https://sslvpn.example.com/link/the_wiki/index.html 3. https://sslvpn.example.com/ext/wikipedia.org The problem here is that although there are separate servers, they all map to the same origin as defined in [RFC6454]. Scripts from any of these sites can affect others. In fact, the Origin header as defined in section 7 of RFC 6454 can leak information to the real web server that it is located within the same flattened domain. The HTTP header introduced in this document allows the portal to specify that URLs that appear to be from the same origin are, in fact, from different origins, by extending the 3-tuple of the origin to a 4-tuple. The user agent would be expected to apply the same- origin policy according to the 4-tuple rather than the 3-tuple. 1.1. Conventions Used in This Document 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 [RFC2119]. 2. The Extended-Origin Header When a web portal hides multiple actual web sites behind its own origin, it MUST add the new Extended-Origin header defined in the next section. The name field need not be related to the actual web origin, and is not meant for human consumption. The requirement is only that different origins MUST have different names in the header. If the response from the original web site already contains one or more Extended-Origin headers, then the portal adds its own header after the rest. Nir Expires August 5, 2012 [Page 3] Internet-Draft Extended Origin February 2012 2.1. Header Format The ABNF is to be added. The header includes a name, which is not necessarily meant for human consumption, and an optional path parameter. The general format is Extended-Origin: name[; path=/something] This means that all requests of the format "GET /something/..." will be considered as going to the origin defined by the combination of the RFC 6454 origin and the name. As such, cookies from the portal MUST not be returned in requests to the extended origin, and vice versa. Scripts from inside the extended origin MUST be prevented from executing requests against the main portal and against other extended origins within the same portal. 2.2. Update to the Serialization Requirements Section 6 of RFC 6454 defines how to serialize an origin for inclusion in the "Origin" header defined in section 7 of that RFC. For serializing an extended origin, follow steps 1-5 of section 6.1 or 6.2 of RFC 6454. To the result, append a U+0023 code point (number sign - #) and the content of the Extended-Origin header. Return the result If the response contains more than one Extended-Origin header, then the user agent MUST append the content of all, separated by number symbols, in reverse order. For example, if the server response looks like this: HTTP/1.1 200 OK Content-Type: application/octet-stream Extended-Origin: webmail Extended-Origin: some_other_portal Then the origin should be as follows: https://sslvpn.example.com#some_other_portal#webmail 3. Examples Here's an example of a connection with both the Extended-Origin and the Origin headers. Nir Expires August 5, 2012 [Page 4] Internet-Draft Extended Origin February 2012 CONNECT https://sslvpn.example.com GET / HTTP/1.1 HTTP/1.1 200 OK Content-Type: application/octet-stream Set-Cookie: session=1234 Welcome, you can read your mail here GET /link/my_web_mail/inbox/index.html HTTP/1.1 Referer: https://sslvpn.example.com/ Cookie: session=1234 HTTP/1.1 200 OK Content-Type: application/octet-stream Extended-Origin: my_web_mail; path=/link/my_web_mail Set-Cookie: mailsession=5678 You have unread message. Jumping there in 5 seconds. GET /link/my_web_mail/inbox/msg0945.html HTTP/1.1 Referer: https://sslvpn.example.com/link/my_web_mail/inbox/index.htm Origin: https://sslvpn.example.com#my_web_mail Cookie: mailsession=5678 In this example, the first GET was the result of the user typing in an address, or following a link. Therefore it has no Origin header. It goes to the main page of the portal, so the response contains no Extended-Origin. The second GET also happened because of clicking a link, not by any action of the page, so there's no need to send an Origin header. If there had been such a header, it would be just as defined in RFC 6454: https://sslvpn.example.com The third GET is caused by a script running on the mail page. This Nir Expires August 5, 2012 [Page 5] Internet-Draft Extended Origin February 2012 page came with an Extended-Origin header, and so the user agent constructs the Origin header in the request according to the new rules in Section 2.2. Note that the cookie set by the main portal was not sent in the third request, because it the second reply belongs to a different origin, and the request URL matches the path parameter of the Extended-Origin header. A more complex example is when the portal hides another portal, resulting in two Extended-Origin headers. Shown here: CONNECT https://sslvpn.example.com GET /link/someotherportal/mail/index.html HTTP/1.1 Referer: https://sslvpn.example.com/mainpage.html Origin: https://sslvpn.example.com HTTP/1.1 200 OK Content-Type: application/octet-stream Extended-Origin: webmail; path=/link/someotherportal/mail Extended-Origin: some_other_portal; path=/link/webmail Set-Cookie: session=90ab You have unread message. Jumping there in 5 seconds. GET /link/someotherportal/my_web_mail/inbox/msg0945.html HTTP/1.1 Origin: https://sslvpn.example.com#some_other_portal#webmail Cookie: session-90ab In this example we see that only the first path parameter is considered. The cookies are sent whenever the link matches the first path parameter. 4. CORS interaction The interaction between this draft and CORS ([CORS]) is to be added. Nir Expires August 5, 2012 [Page 6] Internet-Draft Extended Origin February 2012 5. Open Issues 5.1. Other Methods of Encoding Server Identity Some SSL-VPN products and configurations do not encode the server identity using a prefix in the URL, as shown in the example in Section 3. One such Method is this: https://sslvpn.example.com/p/inb/msg0945.html,HOST=mail.example.com The issue here is that the way the path parameter is defined, you cannot use it to define what URLs belong to the extended origin. We could replace it with a parameter that accepts a regular expression, but that seems overly complex: Extended-Origin: webmail; expr=/p/*,HOST=mail.example.com 6. Acknowledgements Oren Souroujon contributed some of the text in this document, and also came up with the original idea. Yehezkel Horowitz helped with reviewing the draft and pointing out the issues with cookies and paths. 7. Security Considerations This document causes compliant clients to disallow certain actions that are allowed today. In that sense, it reduces the attack surface. More to be added. 8. IANA Considerations The permanent message header field registry (see [RFC3864]) should be updated with the following registration: o Header field name: Extended-Origin o Applicable protocol: http o Status: Standard o Author/Change controller: IETF o Specification document: this specification Nir Expires August 5, 2012 [Page 7] Internet-Draft Extended Origin February 2012 9. Changes from Previous Versions First version 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, December 2011. 10.2. Informative References [CORS] van Kesteren, A., "Cross-Origin Resource Sharing", W3C Working Draft WD-cors-20100727, July 2010. [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", RFC 3864, BCP 90, September 2004. Author's Address Yoav Nir (editor) Check Point Software Technologies Ltd. 5 Hasolelim st. Tel Aviv 67897 Israel Email: ynir@checkpoint.com Nir Expires August 5, 2012 [Page 8]