Network Working Group C. Donley Internet-Draft M. Kloberdans Intended status: Informational CableLabs Expires: August 18, 2014 J. Brzozowski Comcast C. Grundemann ISOC February 14, 2014 Customer Edge Router Identification Option draft-donley-dhc-cer-id-option-03 Abstract Addressing mechanisms supporting DHCPv6 Prefix Delegation in home networks such as those described in CableLabs' eRouter specification and the HIPnet Internet-Draft require identification of the customer edge router (CER) as the demarcation between the customer network and the service provider network. This document reserves a DHCPv6 option to identify the CER. 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 18, 2014. Copyright Notice Copyright (c) 2014 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 Donley, et al. Expires August 18, 2014 [Page 1] Internet-Draft cer-id-option February 2014 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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. CER Identification Option . . . . . . . . . . . . . . . . . . 2 3. Authentication . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Null Authentication . . . . . . . . . . . . . . . . . . . 4 3.2. Simple Password Authentication . . . . . . . . . . . . . 4 3.3. Cryptographic Authentication . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Some addressing mechanisms supporting DHCPv6 Prefix Delegation in home networks such as those described in [I-D.grundemann-hipnet] and [EROUTER] require identification of the customer edge router as the demarcation between the customer network and the service provider network. For prefix delegation purposes, it is desirable for other routers within the home to know which device is the CER so that the customer nome network only requests a single prefix from the ISP DHCPv6 server, and efficiently distributes this prefix within the home. This document reserves a DHCPv6 option to be used to identify the CER. 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. CER Identification Option A Customer Edge Router (CER) sets the CER_ID to the IPv6 address of its LAN interface. If it has more than one LAN IPv6 address, it selects one of its LAN or loopback IPv6 addresses to be used in the CER_ID. An ISP server does not respond with the CER_ID or sets the Donley, et al. Expires August 18, 2014 [Page 2] Internet-Draft cer-id-option February 2014 CER_ID to ::. Such a response or lack of response indicates to the DHCPv6 client that it is the CER. The format of the CER Identification option is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reserved | Auth type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Authentication | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | CER_ID | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_CER_ID (TBD). option-len 36 reserved 16-bit set to 0 Auth Type see section 3 Authentication see section 3 CER_ID value IPv6 address of CER or :: Figure 1. A DHCPv6 client SHOULD include the CER Identification option code in an Option Request option [RFC3315] in its DHCP Solicit messages. The DHCPv6 server MAY include the CER Identification option in any response it sends to a client that has included the CER Identification option code in an Option Request option. The CER Identification option is sent in the main body of the message to client, not as a sub-option in, e.g., an IA_NA, IA_TA [RFC3315]option. When sending the CER Identification option, the DHCPv6 server MUST set the CER_ID value to either one of its IPv6 addresses or ::. If a device does not receive the CER Identification Option or receives a CER ID of :: from the DHCPv6 server, it MUST include one of its Globally Unique IPv6 address(es) in the CER_ID value in response to DHCPv6 messages received by its DHCPv6 server that contains the CER Identification option code in an Option Request option. If the Donley, et al. Expires August 18, 2014 [Page 3] Internet-Draft cer-id-option February 2014 device has only one LAN interface, it SHOULD use its LAN IPv6 address as the CER_ID value. If the device has more than one LAN interface, it SHOULD use the lowest Globally Unique address not assigned to its WAN interface. 3. Authentication All CER-ID messages are authenticated. The CER-ID option header includes an authentication type field, and 128 bits of data for use by the appropriate authentication scheme (determined by the type field). The authentication type is configurable on a per-DHCP-scope basis. Additional authentication data is also configurable on a per-scope basis. Authentication types 0, 1 and 2 are defined by this document. All other authentication types are reserved for definition by the IANA (iana@ISI.EDU). The current list of authentication types is described below. Authentication Type | Description -------------------------------+-------------------------------- 0 Null Authentication 1 Simple Password 2 Cryptographic authentication All Others Reserved for assignment by IANA Authentication Type Description ___________________________________________ 0 Null authentication 1 Simple password 2 Cryptographic authentication All others Reserved for assignment by the IANA (iana@ISI.EDU) D.1 Null authentication D.2 Simple password authentication D.3 Cryptographic authentication 3.1. Null Authentication Use of this authentication type means that the CER-ID option exchange is not authenticated. The 128-bit authentication field in the option header can contain anything; it is not examined on packet reception. 3.2. Simple Password Authentication Using this authentication type, a 128-bit field is configured on a per-network basis. All packets sent by DHCP servers on a particular home network will have this configured value in their CER-ID option 128-bit authentication field. This essentially serves as a "clear" 128-bit password. Simple password authentication guards against home routers inadvertently joining the home IP network (HIPnet); each Donley, et al. Expires August 18, 2014 [Page 4] Internet-Draft cer-id-option February 2014 router must first be configured with its attached networks' passwords before it can participate in the hipnet (e.g., by extending trust to the CER for prefix delegation, service discovery, and firewall services). However, simple password authentication is vulnerable to passive attacks widespread on the Internet. Anyone with physical access to the network can learn the password and compromise the security of the hipnet. 3.3. Cryptographic Authentication Using this authentication type, a shared secret key is configured in all routers within the hipnet. For each CER-ID option, the key is used to generate/verify a MD5 "message digest" that is inserted into the authentication field. The message digest is a one-way function of the 128-bit CER ID and the secret key. Since the secret key is never sent over the network in the clear, protection is provided against passive attacks. 4. IANA Considerations IANA is requested to assign an option code from the "DHCP Option Codes" Registry for OPTION_CER_ID. IANA is also requested to maintain a list of authentication options. 5. Security Considerations The security of a home network is an important consideration. Both the HIPNet [I-D.grundemann-hipnet] and Homenet [I-D.ietf-homenet-arch] approaches change the operational model of the home network vs. today's IPv4-only paradigm. Specifically, these networks eliminate NAT inside the home network (and only enable it for IPv4 at the edge router, if required), support global addressability of devices, and thus need to consider firewall and/or filter support in various home routers. As the security profile of these home routers can shift based on their position in the network (e.g., edge vs. internal), security can be severely compromised if routers misidentify their border and mistakenly reduce or eliminate firewall rules. If the CER-ID option is used as part of the border detection algorithm, a malicious actor with network access to a home router could trick the router into lowering its security perimeter by providing DHCP prefix delegation and adding its address in the CER-ID option. However, this risk could be mitigated by adding simple password authentication or cryptographic authentication. However, as home router devices auto-provision out of the box, and are often not configured directly by customers, the possibility exists that these routers come pre-configured for null authentication, which lessens the security. This is equivalent to routing protocol options such as RIP(v2) or OSPF, which can be run with comparable authentication Donley, et al. Expires August 18, 2014 [Page 5] Internet-Draft cer-id-option February 2014 options and often default to null authentication. Customers interested in security should ensure that they enable stronger authentication during initial provisioning. 6. Acknowledgements 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. 7.2. Informative References [EROUTER] CableLabs, "CableLabs IPv4 and IPv6 eRouter Specification (CM-SP-eRouter-I11-131120)", November 2013. [I-D.grundemann-hipnet] Grundemann, C., Donley, C., Brzozowski, J., Howard, L., and V. Kuarsingh, "A Near Term Solution for Home IP Networking (HIPnet)", draft-grundemann-hipnet-00 (work in progress), July 2013. [I-D.ietf-homenet-arch] Chown, T., Arkko, J., Brandt, A., Troan, O., and J. Weil, "IPv6 Home Networking Architecture Principles", draft- ietf-homenet-arch-11 (work in progress), October 2013. Authors' Addresses Chris Donley CableLabs 858 Coal Creek Cir. Louisville, CO 80027 US Email: c.donley@cablelabs.com Donley, et al. Expires August 18, 2014 [Page 6] Internet-Draft cer-id-option February 2014 Michael Kloberdans CableLabs 858 Coal Creek Cir Louisville, CO 80027 US Email: m.kloberdans@cablelabs.com John Brzozowski Comcast 1306 Goshen Parkway West Chester, PA 19380 US Email: john_brzozowski@cable.comcast.com Chris Grundemann ISOC Denver CO Email: cgrundemann@gmail.com Donley, et al. Expires August 18, 2014 [Page 7]