First-Party Sets and SameSite Cookies
draft-west-cookie-samesite-firstparty-01

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Network Working Group                                            M. West
Internet-Draft                                                    Google
Intended status: Standards Track                            May 10, 2019
Expires: November 11, 2019

                 First-Party Sets and SameSite Cookies
                draft-west-cookie-samesite-firstparty-01

Abstract

   This document proposes the addition of two new values to the
   "SameSite" cookie attribute defined in RFC6265bis
   [I-D.ietf-httpbis-rfc6265bis]: "FirstPartyLax" and
   "FirstPartyStrict".  These values are conceptually similar to the
   existing "Lax" and "Strict" values, but base the delivery checks on
   the First-Party Sets [first-party-set] of a request's initiator and
   target, rather than on their respective registrable domains.  This
   widens the scope of a given cookie's applicability, enabling entities
   that have sharded themselves across multiple registrable domains to
   maintain HTTP state without exposing themselves to the risks of
   "SameSite=None".

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 https://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 November 11, 2019.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
     2.1.  Conformance . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Terms . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The "FirstParty" value of the "SameSite" attribute  . . . . .   4
   4.  Security and Privacy Considerations . . . . . . . . . . . . .   7
     4.1.  CSRF  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Secure Transport  . . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Changes  . . . . . . . . . . . . . . . . . . . . . .   9
     A.1.  Since draft-west-cookie-samesite-firstparty-00  . . . . .   9
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The "SameSite" attribute enables developers to limit the scope of a
   given cookie's delivery, mitigating the risks of some classes of
   cross-site request forgery (CSRF) attack by preventing certain
   cookies from being delivered along with requests that are initiated
   from a cross-site context.

   For example, consider the exciting and dynamic "https://internet-
   bookstore.example/", which uses "SameSite=Lax" cookies as one layer
   in its defense against CSRF attack.  If "https://example.com"
   includes resources from "https://internet-bookstore.example/", the
   request will be considered cross-site, and the authentication cookies
   will not be delivered.  Without that state, CSRF attacks will be
   significantly less effective.

   When the site expands into new locations, it may wish to register a
   domain under a localized TLD, perhaps "https://internet-
   bookstore.测试/".  Likewise, it may decide to shard itself into
   distinct brands, like "https://internet-things-other-than-books-
   store.example/".  Though the same entity controls each of

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