Network Working Group R. Droms Internet-Draft Cisco Systems Expires: April 24, 2003 October 24, 2002 Use of IPsec for Securing DHCPv4 Messages Exchanged Between Relay Agents and Servers draft-droms-dhcp-relay-agent-ipsec-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 24, 2003. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract "DHCP Relay Agent Information Option" (RFC 3046) assumes that DHCP messages exchanged between relay agents and servers are not subject to attack. This document describes how IPsec can be used to protect messages exchanged between relay agents and servers. 1. Introduction "DHCP Relay Agent Information Option" (RFC 3046 [1]) assumes that DHCP [6] messages exchanged between relay agents and servers are not subject to attack. IPsec [7] can be used by DHCP relay agents and server to protect messages they exchange. Droms Expires April 24, 2003 [Page 1] Internet-Draft Use of IPsec for DHCPv4 Messages October 2002 2. Terminology This document uses the DHCP terminology from RFC 2131 and the relay agent terminology from RFC 3046. 3. Requirements The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in RFC 2119 [4]. 4. Use of IPsec to secure DHCP messages Relay agents and servers that exchange messages securely can use IPsec mechanisms as described in this section. Relay agents and servers MUST support manual configuration and installation of static keys. If a client message is relayed through multiple relay agents, each of the relay agents must have established independent, pairwise trust relationships. That is, if messages from client C will be relayed by relay agent A to relay agent B and then to the server, relay agents A and B must be configured to use IPSec for the messages they exchange, and relay agent B and the server must be configured to use IPSec for the messages they exchange. Relay agents and servers that support secure relay agent to server or relay agent to relay agent communication, MUST include an IPsec implementation with the following restrictions: o The IPsec implementation MUST use ESP o Packet authentication MUST be applied o Encryption MAY be applied (i.e., NULL encryption can be used) 5. Security considerations Relay agent options are used by DHCP relay agents to provide additional information about DHCP clients to servers. An attacker that can modify the contents of relay agent options may be able to spoof the identity of a DHCP client or mount a denial of service attack. "Authentication for DHCP Messages" (RFC 3118 [3]) defines a mechanism through which messages exchanged between DHCP clients and servers can be secured. However, the mechanism in RFC 3118 does not provide any protection for relay agent options. "The Authentication Suboption for the DHCP Relay Agent Option" [2] defines an alternative to the Droms Expires April 24, 2003 [Page 2] Internet-Draft Use of IPsec for DHCPv4 Messages October 2002 use of IPsec for securing relay agent options. The use of IPsec for securing relay agent options in DHCP messages requires the existence of an IPsec implementation available to the relay agents and DHCP servers. It also requires manual configuration of the participants, including manual distribution of keys. References [1] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, January 2001. [2] Lemon, T. and M. Stapp, "The Authentication Suboption for the DHCP Relay Agent Option", draft-ietf-dhc-auth-suboption-00 (work in progress), June 2002. [3] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC 3118, June 2001. [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [5] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [7] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. Author's Address Ralph Droms Cisco Systems 300 Apollo Drive Chelmsford, MA 01824 USA Phone: +1 978 497 4733 EMail: rdroms@cisco.com Droms Expires April 24, 2003 [Page 3] Internet-Draft Use of IPsec for DHCPv4 Messages October 2002 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Droms Expires April 24, 2003 [Page 4]