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diff --git a/doc/draft/draft-ietf-dnsext-dhcid-rr-12.txt b/doc/draft/draft-ietf-dnsext-dhcid-rr-12.txt new file mode 100644 index 0000000..07749d9 --- /dev/null +++ b/doc/draft/draft-ietf-dnsext-dhcid-rr-12.txt @@ -0,0 +1,674 @@ + + + + +DNSEXT M. Stapp +Internet-Draft Cisco Systems, Inc. +Expires: September 1, 2006 T. Lemon + Nominum, Inc. + A. Gustafsson + Araneus Information Systems Oy + February 28, 2006 + + + A DNS RR for Encoding DHCP Information (DHCID RR) + <draft-ietf-dnsext-dhcid-rr-12.txt> + +Status of this Memo + + By submitting this Internet-Draft, each author represents that any + applicable patent or other IPR claims of which he or she is aware + have been or will be disclosed, and any of which he or she becomes + aware will be disclosed, in accordance with Section 6 of BCP 79. + + 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 September 1, 2006. + +Copyright Notice + + Copyright (C) The Internet Society (2006). + +Abstract + + It is possible for DHCP clients to attempt to update the same DNS + FQDN or attempt to update a DNS FQDN that has been added to the DNS + for another purpose as they obtain DHCP leases. Whether the DHCP + server or the clients themselves perform the DNS updates, conflicts + can arise. To resolve such conflicts, "Resolution of DNS Name + + + +Stapp, et al. Expires September 1, 2006 [Page 1] + +Internet-Draft The DHCID RR February 2006 + + + Conflicts" [1] proposes storing client identifiers in the DNS to + unambiguously associate domain names with the DHCP clients to which + they refer. This memo defines a distinct RR type for this purpose + for use by DHCP clients and servers, the "DHCID" RR. + + +Table of Contents + + 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 3.1. DHCID RDATA format . . . . . . . . . . . . . . . . . . . . 3 + 3.2. DHCID Presentation Format . . . . . . . . . . . . . . . . 4 + 3.3. The DHCID RR Identifier Type Codes . . . . . . . . . . . . 4 + 3.4. The DHCID RR Digest Type Code . . . . . . . . . . . . . . 4 + 3.5. Computation of the RDATA . . . . . . . . . . . . . . . . . 5 + 3.5.1. Using the Client's DUID . . . . . . . . . . . . . . . 5 + 3.5.2. Using the Client Identifier Option . . . . . . . . . . 5 + 3.5.3. Using the Client's htype and chaddr . . . . . . . . . 6 + 3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 3.6.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 6 + 3.6.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 6 + 3.6.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . 7 + 4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . . 7 + 5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . . 8 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 + 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 + 9.2. Informative References . . . . . . . . . . . . . . . . . . 10 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 + Intellectual Property and Copyright Statements . . . . . . . . . . 12 + + + + + + + + + + + + + + + + + + +Stapp, et al. Expires September 1, 2006 [Page 2] + +Internet-Draft The DHCID RR February 2006 + + +1. Terminology + + 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 [2]. + + +2. Introduction + + A set of procedures to allow DHCP [6] [10] clients and servers to + automatically update the DNS (RFC 1034 [3], RFC 1035 [4]) is proposed + in "Resolution of DNS Name Conflicts" [1]. + + Conflicts can arise if multiple DHCP clients wish to use the same DNS + name or a DHCP client attempts to use a name added for another + purpose. To resolve such conflicts, "Resolution of DNS Name + Conflicts" [1] proposes storing client identifiers in the DNS to + unambiguously associate domain names with the DHCP clients using + them. In the interest of clarity, it is preferable for this DHCP + information to use a distinct RR type. This memo defines a distinct + RR for this purpose for use by DHCP clients or servers, the "DHCID" + RR. + + In order to obscure potentially sensitive client identifying + information, the data stored is the result of a one-way SHA-256 hash + computation. The hash includes information from the DHCP client's + message as well as the domain name itself, so that the data stored in + the DHCID RR will be dependent on both the client identification used + in the DHCP protocol interaction and the domain name. This means + that the DHCID RDATA will vary if a single client is associated over + time with more than one name. This makes it difficult to 'track' a + client as it is associated with various domain names. + + +3. The DHCID RR + + The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The + DHCID RR is only defined in the IN class. DHCID RRs cause no + additional section processing. The DHCID RR is not a singleton type. + +3.1. DHCID RDATA format + + The RDATA section of a DHCID RR in transmission contains RDLENGTH + octets of binary data. The format of this data and its + interpretation by DHCP servers and clients are described below. + + DNS software should consider the RDATA section to be opaque. DHCP + clients or servers use the DHCID RR to associate a DHCP client's + + + +Stapp, et al. Expires September 1, 2006 [Page 3] + +Internet-Draft The DHCID RR February 2006 + + + identity with a DNS name, so that multiple DHCP clients and servers + may deterministically perform dynamic DNS updates to the same zone. + From the updater's perspective, the DHCID resource record RDATA + consists of a 2-octet identifier type, in network byte order, + followed by a 1-octet digest type, followed by one or more octets + representing the actual identifier: + + < 2 octets > Identifier type code + < 1 octet > Digest type code + < n octets > Digest (length depends on digest type) + +3.2. DHCID Presentation Format + + In DNS master files, the RDATA is represented as a single block in + base 64 encoding identical to that used for representing binary data + in RFC 3548 [7]. The data may be divided up into any number of white + space separated substrings, down to single base 64 digits, which are + concatenated to form the complete RDATA. These substrings can span + lines using the standard parentheses. + +3.3. The DHCID RR Identifier Type Codes + + The DHCID RR Identifier Type Code specifies what data from the DHCP + client's request was used as input into the hash function. The + identifier type codes are defined in a registry maintained by IANA, + as specified in Section 7. The initial list of assigned values for + the identifier type code is: + + 0x0000 = htype, chaddr from a DHCPv4 client's DHCPREQUEST [6]. + 0x0001 = The data octets (i.e., the Type and Client-Identifier + fields) from a DHCPv4 client's Client Identifier option [9]. + 0x0002 = The client's DUID (i.e., the data octets of a DHCPv6 + client's Client Identifier option [10] or the DUID field from a + DHCPv4 client's Client Identifier option [12]). + + 0x0003 - 0xfffe = Available to be assigned by IANA. + + 0xffff = RESERVED + +3.4. The DHCID RR Digest Type Code + + The DHCID RR Digest Type Code is an identifier for the digest + algorithm used. The digest is calculated over an identifier and the + canonical FQDN as described in the next section. + + The digest type codes are defined in a registry maintained by IANA, + as specified in Section 7. The initial list of assigned values for + the digest type codes is: value 0 is reserved and value 1 is SHA-256. + + + +Stapp, et al. Expires September 1, 2006 [Page 4] + +Internet-Draft The DHCID RR February 2006 + + + Reserving other types requires IETF standards action. Defining new + values will also require IETF standards action to document how DNS + updaters are to deal with multiple digest types. + +3.5. Computation of the RDATA + + The DHCID RDATA is formed by concatenating the 2-octet identifier + type code with variable-length data. + + The RDATA for all type codes other than 0xffff, which is reserved for + future expansion, is formed by concatenating the 2-octet identifier + type code, the 1-octet digest type code, and the digest value (32 + octets for SHA-256). + + < identifier-type > < digest-type > < digest > + + The input to the digest hash function is defined to be: + + digest = SHA-256(< identifier > < FQDN >) + + The FQDN is represented in the buffer in unambiguous canonical form + as described in RFC 4034 [8], section 6.1. The identifier type code + and the identifier are related as specified in Section 3.3: the + identifier type code describes the source of the identifier. + + A DHCPv4 updater uses the 0x0002 type code if a Client Identifier + option is present in the DHCPv4 messages and it is encoded as + specified in [12]. Otherwise, the updater uses 0x0001 if a Client + Identifier option is present and 0x0000 if not. + + A DHCPv6 updater always uses the 0x0002 type code. + +3.5.1. Using the Client's DUID + + When the updater is using the Client's DUID (either from a DHCPv6 + Client Identifier option or from a portion of the DHCPv4 Client + Identifier option encoded as specified in [12]), the first two octets + of the DHCID RR MUST be 0x0002, in network byte order. The third + octet is the digest type code (1 for SHA-256). The rest of the DHCID + RR MUST contain the results of computing the SHA-256 hash across the + octets of the DUID followed by the FQDN. + +3.5.2. Using the Client Identifier Option + + When the updater is using the DHCPv4 Client Identifier option sent by + the client in its DHCPREQUEST message, the first two octets of the + DHCID RR MUST be 0x0001, in network byte order. The third octet is + the digest type code (1 for SHA-256). The rest of the DHCID RR MUST + + + +Stapp, et al. Expires September 1, 2006 [Page 5] + +Internet-Draft The DHCID RR February 2006 + + + contain the results of computing the SHA-256 hash across the data + octets (i.e., the Type and Client-Identifier fields) of the option, + followed by the FQDN. + +3.5.3. Using the Client's htype and chaddr + + When the updater is using the client's link-layer address as the + identifier, the first two octets of the DHCID RDATA MUST be zero. + The third octet is the digest type code (1 for SHA-256). To generate + the rest of the resource record, the updater computes a one-way hash + using the SHA-256 algorithm across a buffer containing the client's + network hardware type, link-layer address, and the FQDN data. + Specifically, the first octet of the buffer contains the network + hardware type as it appeared in the DHCP 'htype' field of the + client's DHCPREQUEST message. All of the significant octets of the + 'chaddr' field in the client's DHCPREQUEST message follow, in the + same order in which the octets appear in the DHCPREQUEST message. + The number of significant octets in the 'chaddr' field is specified + in the 'hlen' field of the DHCPREQUEST message. The FQDN data, as + specified above, follows. + +3.6. Examples + +3.6.1. Example 1 + + A DHCP server allocating the IPv4 address 10.0.0.1 to a client with + Ethernet MAC address 01:02:03:04:05:06 using domain name + "client.example.com" uses the client's link-layer address to identify + the client. The DHCID RDATA is composed by setting the two type + octets to zero, the 1-octet digest type to 1 for SHA-256, and + performing an SHA-256 hash computation across a buffer containing the + Ethernet MAC type octet, 0x01, the six octets of MAC address, and the + domain name (represented as specified in Section 3.5). + + client.example.com. A 10.0.0.1 + client.example.com. DHCID ( AAABxLmlskllE0MVjd57zHcWmEH3pCQ6V + ytcKD//7es/deY= ) + + If the DHCID RR type is not supported, the RDATA would be encoded + [13] as: + + \# 35 ( 000001c4b9a5b249651343158dde7bcc77169841f7a4243a572b5c283 + fffedeb3f75e6 ) + +3.6.2. Example 2 + + A DHCP server allocates the IPv4 address 10.0.12.99 to a client which + included the DHCP client-identifier option data 01:07:08:09:0a:0b:0c + + + +Stapp, et al. Expires September 1, 2006 [Page 6] + +Internet-Draft The DHCID RR February 2006 + + + in its DHCP request. The server updates the name "chi.example.com" + on the client's behalf, and uses the DHCP client identifier option + data as input in forming a DHCID RR. The DHCID RDATA is formed by + setting the two type octets to the value 0x0001, the 1-octet digest + type to 1 for SHA-256, and performing a SHA-256 hash computation + across a buffer containing the seven octets from the client-id option + and the FQDN (represented as specified in Section 3.5). + + chi.example.com. A 10.0.12.99 + chi.example.com. DHCID ( AAEBOSD+XR3Os/0LozeXVqcNc7FwCfQdW + L3b/NaiUDlW2No= ) + + If the DHCID RR type is not supported, the RDATA would be encoded + [13] as: + + \# 35 ( 0001013920fe5d1dceb3fd0ba3379756a70d73b17009f41d58bddbfcd + 6a2503956d8da ) + +3.6.3. Example 3 + + A DHCP server allocates the IPv6 address 2000::1234:5678 to a client + which included the DHCPv6 client-identifier option data 00:01:00:06: + 41:2d:f1:66:01:02:03:04:05:06 in its DHCPv6 request. The server + updates the name "chi6.example.com" on the client's behalf, and uses + the DHCP client identifier option data as input in forming a DHCID + RR. The DHCID RDATA is formed by setting the two type octets to the + value 0x0002, the 1-octet digest type to 1 for SHA-256, and + performing a SHA-256 hash computation across a buffer containing the + 14 octets from the client-id option and the FQDN (represented as + specified in Section 3.5). + + chi6.example.com. AAAA 2000::1234:5678 + chi6.example.com. DHCID ( AAIBY2/AuCccgoJbsaxcQc9TUapptP69l + OjxfNuVAA2kjEA= ) + + If the DHCID RR type is not supported, the RDATA would be encoded + [13] as: + + \# 35 ( 000201636fc0b8271c82825bb1ac5c41cf5351aa69b4febd94e8f17cd + b95000da48c40 ) + + +4. Use of the DHCID RR + + This RR MUST NOT be used for any purpose other than that detailed in + "Resolution of DNS Name Conflicts" [1]. Although this RR contains + data that is opaque to DNS servers, the data must be consistent + across all entities that update and interpret this record. + + + +Stapp, et al. Expires September 1, 2006 [Page 7] + +Internet-Draft The DHCID RR February 2006 + + + Therefore, new data formats may only be defined through actions of + the DHC Working Group, as a result of revising [1]. + + +5. Updater Behavior + + The data in the DHCID RR allows updaters to determine whether more + than one DHCP client desires to use a particular FQDN. This allows + site administrators to establish policy about DNS updates. The DHCID + RR does not establish any policy itself. + + Updaters use data from a DHCP client's request and the domain name + that the client desires to use to compute a client identity hash, and + then compare that hash to the data in any DHCID RRs on the name that + they wish to associate with the client's IP address. If an updater + discovers DHCID RRs whose RDATA does not match the client identity + that they have computed, the updater SHOULD conclude that a different + client is currently associated with the name in question. The + updater SHOULD then proceed according to the site's administrative + policy. That policy might dictate that a different name be selected, + or it might permit the updater to continue. + + +6. Security Considerations + + The DHCID record as such does not introduce any new security problems + into the DNS. In order to obscure the client's identity information, + a one-way hash is used. And, in order to make it difficult to + 'track' a client by examining the names associated with a particular + hash value, the FQDN is included in the hash computation. Thus, the + RDATA is dependent on both the DHCP client identification data and on + each FQDN associated with the client. + + However, it should be noted that an attacker that has some knowledge, + such as of MAC addresses commonly used in DHCP client identification + data, may be able to discover the client's DHCP identify by using a + brute-force attack. Even without any additional knowledge, the + number of unknown bits used in computing the hash is typically only + 48 to 80. + + Administrators should be wary of permitting unsecured DNS updates to + zones, whether or not they are exposed to the global Internet. Both + DHCP clients and servers SHOULD use some form of update + authentication (e.g., TSIG [11]) when performing DNS updates. + + +7. IANA Considerations + + + + +Stapp, et al. Expires September 1, 2006 [Page 8] + +Internet-Draft The DHCID RR February 2006 + + + IANA is requested to allocate a DNS RR type number for the DHCID + record type. + + This specification defines a new number-space for the 2-octet + identifier type codes associated with the DHCID RR. IANA is + requested to establish a registry of the values for this number- + space. Three initial values are assigned in Section 3.3, and the + value 0xFFFF is reserved for future use. New DHCID RR identifier + type codes are assigned through Standards Action, as defined in RFC + 2434 [5]. + + This specification defines a new number-space for the 1-octet digest + type codes associated with the DHCID RR. IANA is requested to + establish a registry of the values for this number-space. Two + initial values are assigned in Section 3.4. New DHCID RR digest type + codes are assigned through Standards Action, as defined in RFC 2434 + [5]. + + +8. Acknowledgements + + Many thanks to Harald Alvestrand, Ralph Droms, Olafur Gudmundsson, + Sam Hartman, Josh Littlefield, Pekka Savola, and especially Bernie + Volz for their review and suggestions. + + +9. References + +9.1. Normative References + + [1] Stapp, M. and B. Volz, "Resolution of DNS Name Conflicts Among + DHCP Clients (draft-ietf-dhc-dns-resolution-*)", February 2006. + + [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement + Levels", BCP 14, RFC 2119, March 1997. + + [3] Mockapetris, P., "Domain names - concepts and facilities", + STD 13, RFC 1034, November 1987. + + [4] Mockapetris, P., "Domain names - implementation and + specification", STD 13, RFC 1035, November 1987. + + [5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA + Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. + + + + + + + +Stapp, et al. Expires September 1, 2006 [Page 9] + +Internet-Draft The DHCID RR February 2006 + + +9.2. Informative References + + [6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, + March 1997. + + [7] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", + RFC 3548, July 2003. + + [8] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, + "Resource Records for the DNS Security Extensions", RFC 4034, + March 2005. + + [9] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor + Extensions", RFC 2132, March 1997. + + [10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. + Carney, "Dynamic Host Configuration Protocol for IPv6 + (DHCPv6)", RFC 3315, July 2003. + + [11] Vixie, P., Gudmundsson, O., Eastlake, D., and B. Wellington, + "Secret Key Transaction Authentication for DNS (TSIG)", + RFC 2845, May 2000. + + [12] Lemon, T. and B. Sommerfeld, "Node-specific Client Identifiers + for Dynamic Host Configuration Protocol Version Four (DHCPv4)", + RFC 4361, February 2006. + + [13] Gustafsson, A., "Handling of Unknown DNS Resource Record (RR) + Types", RFC 3597, September 2003. + + + + + + + + + + + + + + + + + + + + + + +Stapp, et al. Expires September 1, 2006 [Page 10] + +Internet-Draft The DHCID RR February 2006 + + +Authors' Addresses + + Mark Stapp + Cisco Systems, Inc. + 1414 Massachusetts Ave. + Boxborough, MA 01719 + USA + + Phone: 978.936.1535 + Email: mjs@cisco.com + + + Ted Lemon + Nominum, Inc. + 950 Charter St. + Redwood City, CA 94063 + USA + + Email: mellon@nominum.com + + + Andreas Gustafsson + Araneus Information Systems Oy + Ulappakatu 1 + 02320 Espoo + Finland + + Email: gson@araneus.fi + + + + + + + + + + + + + + + + + + + + + + + +Stapp, et al. Expires September 1, 2006 [Page 11] + +Internet-Draft The DHCID RR February 2006 + + +Intellectual Property Statement + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. 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Please address the information to the IETF at + ietf-ipr@ietf.org. + + +Disclaimer of Validity + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM 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. + + +Copyright Statement + + Copyright (C) The Internet Society (2006). This document is subject + to the rights, licenses and restrictions contained in BCP 78, and + except as set forth therein, the authors retain all their rights. + + +Acknowledgment + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + +Stapp, et al. Expires September 1, 2006 [Page 12] + + |
