IPv6 maintenance Working Group F. Gont (6man) UTN/FRH Internet-Draft R. Broersma Updates: 4861 (if approved) DREN Intended status: Standards Track March 12, 2011 Expires: September 13, 2011 Managing the Use of Privacy Extensions for Stateless Address Autoconfiguration in IPv6 draft-gont-6man-managing-privacy-extensions-01 Abstract This document describes an operational problem that arises due to the impossibility of managing the use of "Privacy Extensions" for IPv6 Stateless Address Autoconfiguration (SLAAC) in network scenarios that employ SLAAC. Additionally, this document specifies new flag in the Prefix Information option of Router Advertisement messages, such that routers can advertise, for each network prefix to be used for SLAAC, whether the aforementioned "Privacy Extensions" should be used. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, and it may not be published except as an Internet-Draft. 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 13, 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 Gont & Broersma Expires September 13, 2011 [Page 1]

Internet-Draft Managing Privacy Addresses March 2011 (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 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Updating the Prefix Information option . . . . . . . . . . . . 4 2.1. Router specification . . . . . . . . . . . . . . . . . . . 5 2.2. Host specification . . . . . . . . . . . . . . . . . . . . 5 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9 Appendix A. Possible alternatives . . . . . . . . . . . . . . . . 11 A.1. Specifying a 'hardware-addresses' bit . . . . . . . . . . 11 A.2. Specifying a 'privacy-addresses' bit . . . . . . . . . . . 12 Appendix B. Changes from previous versions of the draft (to be removed by the RFC Editor before publication of this document as a RFC . . . . . . . . . . . . . . 14 B.1. Changes from draft-gont-6man-managing-privacy-extensions-00 . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Gont & Broersma Expires September 13, 2011 [Page 2]

Internet-Draft Managing Privacy Addresses March 2011 1 . Introduction RFC4862] specifies the Stateless Address Autoconfiguration (SLAAC) for IPv6, which typically results in hosts configuring one or more addresses composed of a network prefix advertised by a local router, and an Interface Identifier (IID) derived from a hardware address (such as an Ethernet MAC address). Since e.g. Ethernet MAC addresses are typically globally unique, IPv6 addresses generated as specified in [RFC4862] could possibly be levareged to track and correlate the activity of a node, thus negatively affecting the privacy of users. The "Privacy Extensions for Stateless Address Autoconfiguration in IPv6" [RFC4941] were introduced difficult the task of eavesdroppers and other information collectors to correlate the activities of a node, and basically result in random Interface Identifiers which may be more difficult to leverage than their hardware-derived counterpart. These "Privacy Extensions" have been implemented in a variety of systems, some of which (notably that in Microsoft Windows Vista and Microsoft Windows 7) enable them by default. The imposibility of managing the use of "Privacy Extensions" poses poses a problem when a site has a specific policy for the generation of IPv6 Interface Identifiers. For example, if hosts that enable "Privacy Extensions" (by default) need to be deployed on sites that require the use of hardware-derived Interface Identifiers, an administrator may need to manually disable the use of "Privacy Extensions" in each of the attached nodes. This not only may result in a lot of work on the side of the administrator, but may also be difficult to implement (particularly when considering mobile computers such as laptops) [Broersma]. On the other hand, in some environments (e.g., a typical home network) the use of "Privacy Extensions" might be desirable. However, the imposibility to automatically enable "Privacy Extensions" may preclude their use (unless they are manually enabled by the administrator). This document specifies a new flag in the Prefix Information option of Router Advertisement messages, such that routers can advertise, for each network prefix to be used for SLAAC, whether the aforementioned "Privacy Extensions" should be used. 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]. Gont & Broersma Expires September 13, 2011 [Page 3]

Internet-Draft Managing Privacy Addresses March 2011 2 . Updating the Prefix Information option Gont & Broersma Expires September 13, 2011 [Page 4]

Internet-Draft Managing Privacy Addresses March 2011 The "R" bit was specified by [RFC3775]. The Rsvd1 field corresponds to the remaining reserved bits, and thus MUST be set to zero by the sender of this option, and ignored by the receiver. Since the "SAG" bits correspond to a previously "reserved" field, implementations that predate this specification should be setting the SAG field to "00" when sending the option, and ignoring the SAG bits upon receipt. 2.1 . Router specification 2.2 . Host specification Gont & Broersma Expires September 13, 2011 [Page 5]

Internet-Draft Managing Privacy Addresses March 2011 3 . Security Considerations I-D.ietf-v6ops-ra-guard]. SEND (SEcure Neighbor Discovery) [RFC3971] could be pontentially deployed to mitigate most Neighbor Discovery attacks. However, a number of issues (such as the requirement for Public Key Infrastructure) preclude the deployment of SEND in most general network scenarions. [CPNI-IPv6] Finally, we note that while the value and effectiveness of privacy addreses have been questioned in a number of studies [I-D.dupont-ipv6-rfc3041harmful] [Escudero] [CPNI-IPv6], this document does not take a stance about their value and effectiveness: it limits itself to discussing the operational problem that arises due to the impossibility of managing the use of "Privacy Extensions", and updating the "Prefix Information" option such that "Privacy Extensions" can be more easily managed when IPv6 Stateless Address Autoconfiguration (SLAAC) is employed. Gont & Broersma Expires September 13, 2011 [Page 6]

Internet-Draft Managing Privacy Addresses March 2011 4 . IANA Considerations Gont & Broersma Expires September 13, 2011 [Page 7]

Internet-Draft Managing Privacy Addresses March 2011 5 . Acknowledgements http://www.cpni.gov.uk) for their continued support. Gont & Broersma Expires September 13, 2011 [Page 8]

Internet-Draft Managing Privacy Addresses March 2011 AUTOCONFIGURATION IN IPV6 - "REQUIREMENTS FOR UNOBSERVABILITY", RVK02, Stockholm, 2002, <http://web.it.kth.se/~aep/PhD/docs/paper3-rvk2002.pdf>. [CPNI-IPv6] Gont, F., "Security Assessment of the Internet Protocol version 6 (IPv6)", UK Centre for the Protection of National Infrastructure, (to be published). Gont & Broersma Expires September 13, 2011 [Page 10]

Internet-Draft Managing Privacy Addresses March 2011 Appendix A . Possible alternatives A.1 . Specifying a 'hardware-addresses' bit Gont & Broersma Expires September 13, 2011 [Page 11]

Internet-Draft Managing Privacy Addresses March 2011 The "R" bit was specified by [RFC3775]. The Rsvd1 field corresponds to the remaining reserved bits, and thus MUST be set to zero by the sender of this option, and ignored by the receiver. Since the "H" bit was a previously reserved field, implementations that predate this specification should be setting this bit to zero when sending the option, and ignoring this bit upon receipt. The following table illustrates the result of SLAAC depending on whether this specification is supported by the router and/or the host participanting in SLAAC. +---------------+--------------------------+------------------------+ | Router / Host | Supported | Not Supported | +---------------+--------------------------+------------------------+ | Supported | As indicated by the "H" | As in current | | | bit | scenarios | +---------------+--------------------------+------------------------+ | Not Supported | Privacy Addresses | As in current | | | | scenarios | +---------------+--------------------------+------------------------+ Table 1: Possible results of SLAAC scenarios A.2 . Specifying a 'privacy-addresses' bit Gont & Broersma Expires September 13, 2011 [Page 12]

Internet-Draft Managing Privacy Addresses March 2011 hardware addresses are used. This would mean that if e.g. MS were to implement this spec before e.g. Cisco, Privacy Addresses would be disabled. Clearly, there's a tradeoff here. Gont & Broersma Expires September 13, 2011 [Page 13]

Internet-Draft Managing Privacy Addresses March 2011 Authors' Addresses Fernando Gont Universidad Tecnologica Nacional / Facultad Regional Haedo Evaristo Carriego 2644 Haedo, Provincia de Buenos Aires 1706 Argentina Phone: +54 11 4650 8472 Email: fernando@gont.com.ar Ron Broersma Defense Research and Engineering Network Email: ron@spawar.navy.mil Gont & Broersma Expires September 13, 2011 [Page 15]