Network Working Group J. Bound Internet-Draft Compaq Computer Corporation Expires: July 2, 2002 M. Carney Sun Microsystems, Inc. C. Perkins Nokia Research Center T. Lemon Nominum B. Volz Ericsson R. Droms Cisco Systems Jan 2002 DNS Configuration Options for DHCPv6 draft-ietf-dhc-dhcpv6-opt-dnsconfig-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 July 2, 2002. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This document describes three options for DNS-related configuration information in DHCPv6: DNS Servers, Domain Name, Domain Search list. Bound, et al. Expires July 2, 2002 [Page 1] Internet-Draft DNS Configuration Options for DHCPv6 Jan 2002 1. Introduction This document describes three options for configuration information related to Domain Name Service (DNS) [1, 2] in DHCPv6 [5]. 2. 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 [1] 3. Terminology This document uses terminology specific to IPv6 and DHCPv6 as defined in section "Terminology" of the DHCP specification. 4. Domain Name Server option The Domain Name Server option provides a list of one or more IP addresses of DNS servers to which a client's DNS resolver MAY send DNS queries [3]. The DNS servers SHOULD be listed in the order of preference for use by the client resolver. The format of the Domain Name Server 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_DNS_SERVERS | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | DNS server (IP address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | DNS server (IP address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_DNS_SERVERS option-length: Length of the 'options' field in octets; must be a Bound, et al. Expires July 2, 2002 [Page 2] Internet-Draft DNS Configuration Options for DHCPv6 Jan 2002 multiple of 16 DNS server: IP address of DNS server 5. Domain Name option The Domain Name option is used by the server to inform the client of the domain name the client should append to its host name to form the client's fully qualified domain name (FQDN). The format of the Domain Name 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_DOMAIN_NAME | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | domain-name | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_DOMAIN_NAME (tbd) option-length: Length of the 'domain-name' field in octets domain-name: Domain name for client The 'domain-name' MUST be encoded as specified in section "Representation and use of domain names" of the DHCPv6 specification [5]. Local client policy MAY choose to override the domain-name supplied in the Domain-Name option with a locally configured value. 6. Domain Search List option In some circumstances, it is useful for the DHCP client to be configured with list of domain names to be appended to a host name when resolving DNS name. This document defines a new DHCP option which is passed from the DHCP server to the DHCP client to specify the domain search list used when resolving hostnames with DNS. This option does not apply to other name resolution mechanisms. Bound, et al. Expires July 2, 2002 [Page 3] Internet-Draft DNS Configuration Options for DHCPv6 Jan 2002 The format of the Domain Search 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_DOMAIN_LIST | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | searchstring | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_DOMAIN_LIST (tbd) option-length: Length of the 'searchstring' field in octets searchstring: The specification of the list of domain names in the Domain Search List The list of domain names in the 'searchstring' MUST be encoded as specified in section "Representation and use of domain names" of the DHCPv6 specification [5]. Local client policy MAY choose to override the domain search list supplied in the Domain Search List option with a locally configured value. 7. Appearance of these option The Domain Name Server option MUST appear only in the following messages: Solicit, Advertise, Request, Confirm, Renew, Rebind, Information-Request, Reply. The Domain Name option MUST appear only in the following messages: Solicit, Advertise, Request, Confirm, Renew, Rebind, Information- Request, Reply. The Domain Search List option MUST appear only in the following messages: Solicit, Advertise, Request, Confirm, Renew, Rebind, Information-Request, Reply. Note that the Domain Search List option will only appear in a Solicit message if the client has a preferred search list that it is supplying to the server as a hint. 8. Security Considerations The Domain Name Server option may be used by an intruder DHCP server to cause DHCP clients to send DNS queries to an intruder DNS server. Bound, et al. Expires July 2, 2002 [Page 4] Internet-Draft DNS Configuration Options for DHCPv6 Jan 2002 The results of these misdirected DNS queries may be used to spoof DNS names. The Domain Name option may be used by an intruder DHCP server to configure a DHCP client with an invalid domain name, which could be used as a denial of service attack. The Domain Search List option may be used by an intruder DHCP server to cause DHCP clients to search through invalid domains for incompletely specified domain names. The results of these misdirected searches may be used to spoof DNS names. To avoid attacks through the Domain Name Server option and the Domain Name option, the DHCP client SHOULD use authenticated DHCP (see section "Authentication of DHCP messages" in the DHCPv6 specification [5]. Because the Domain Search List option may be used to spoof DNS name resolution in a way that cannot be detected by DNS security mechanisms like DNSSEC [4], DHCP clients and servers MUST use authenticated DHCP when a Domain Search List option is included in a DHCP message. 9. IANA Considerations IANA is requested to assign an option code to these options from the option-code space defined in section "DHCPv6 Options" of the DHCPv6 specification [5]. References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [3] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [4] Eastlake, D., "Domain Name System Security Extensions", RFC 2535, March 1999. [5] Bound, J., Carney, M., Perkins, C., Lemon, T., Volz, B. and R. Droms (ed.), "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", draft-ietf-dhc-dhcpv6-23 (work in progress), February 2002. Bound, et al. Expires July 2, 2002 [Page 5] Internet-Draft DNS Configuration Options for DHCPv6 Jan 2002 Authors' Addresses Jim Bound Compaq Computer Corporation ZK3-3/W20 110 Spit Brook Road Nashua, NH 03062-2698 USA Phone: +1 603 884 0062 EMail: Jim.Bound@compaq.com Mike Carney Sun Microsystems, Inc. Mail Stop: UMPK17-202 901 San Antonio Road Palo Alto, CA 94303-4900 USA> Phone: +1 650 786 4171 EMail: mwc@eng.sun.com Charlie Perkins Nokia Research Center Communications Systems Lab 313 Fairchild Drive Mountain View, CA 94043 USA Phone: +1 650 625 2503 EMail: charliep@iprg.nokia.com Nominum EMail: mellon@nominum.com Bernie Volz Ericsson 959 Concord Street Framingham, MA 01701 USA Phone: +1 508 875 3162 EMail: bernie.volz@ericsson.com Bound, et al. Expires July 2, 2002 [Page 6] Internet-Draft DNS Configuration Options for DHCPv6 Jan 2002 Ralph Droms Cisco Systems 250 Apollo Drive Chelmsford, MA 01824 USA Phone: +1 978 497 4733 EMail: rdroms@cisco.com Bound, et al. Expires July 2, 2002 [Page 7] Internet-Draft DNS Configuration Options for DHCPv6 Jan 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. Bound, et al. Expires July 2, 2002 [Page 8]