DNSEXT Working Group David C Lawrence INTERNET-DRAFT Nominum
<draft-ietf-dnsext-obsolete-iquery-01.txt> June<draft-ietf-dnsext-obsolete-iquery-02.txt> December 2001 Updates: RFC 1035 Obsoleting IQUERY 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 Comments should be sent to the authors or the DNSEXT WG mailing list firstname.lastname@example.org. This draft expires on December 20, 2001.14 June 2002. Copyright Notice Copyright (C) The Internet Society (2001). All rights reserved. Abstract Based on a lack of working implementations of the IQUERY method of performing inverse DNS lookups, and because an alternative mechanism for doing inverse queries of address records has been successfully used operationally for well over a decade, this draft proposes that the IQUERY operation be entirely obsoleted. 1 - Introduction As specified in RFC 1035 (section 6.4), the IQUERY operation for DNS queries is used to look up the name(s) which are associated with the given value. The value being sought is provided in the query's answer section and the response fills in the question section with one or more 3-tuples of type, name and class. As noted in [RFC1035], section 6.4.3, inverse query processing can put quite an onerous burden on a server. A server would need to perform either an exhaustive search of its database or maintain a separate database that is keyed by the values of the primary database. Both of these approaches could strain system resource use, particularly for servers that are authoritative for millions of names. Response packet from these megaservers could be exceptionally large, and easily run into megabyte sizes. For example, using IQUERY to find every domain that is delegated to one of the nameservers of a large ISP could return tens of thousands of 3-tuples in the question section. This could easily be used to launch denial of service attacks. Operators of servers that do support IQUERY in some form (such as very old BIND 4 servers) generally opt to disable it. This is largely due to bugs in insufficiently-exercised code, or concerns about exposure of large blocks of names in their zones by probes such as inverse MX queries. IQUERY is also somewhat inherently crippled by being unable to tell a requestor where it needs to go to get the information that was requested. The answer is very specific to the single server that was queried. This is sometimes a handy diagnostic tool, but apparently not enough so that server operators like to enable it, or request implementation where it's lacking. No known clients use IQUERY to provide any meaningful service. The only common reverse mapping support on the Internet, mapping address records to names, is provided through the use of PTR records in the in-addr.arpa tree and has served the community well for many years. Based on all of these factors, this draft proposes that the IQUERY operation for DNS servers be officially obsoleted. 1.1 - Requirements The key words "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in this document are to be interpreted as described in RFC2119. 1.2 - Updated documents and sections In RFC 10351035, sections 4.1.1 is updated in part and section 6.4 are changed.is entirely superseded. 2 - New text for RFC 1035. Section 4.1.1 has the following text to describe opcode 1: "1 an inverse query (IQUERY)" IsIt is amendednow considered to read:read as follows: "1 an inverse query (IQUERY) (obsolete)" Section 6.4, including all subsections, of RFC 1035 should be considered obsolete and not to be implemented. It is changed to readThe section effectively now reads as follows: "Inverse queries using the IQUERY opcode were originally described as the ability to look up the names that are associated with a particular RR. Their implementation was optional and never achieved widespread use. Therefore IQUERY is now obsolete, and name servers SHOULD return a "Not Implemented" error when an IQUERY request is received." 4 - Security Considerations: Since this document obsoletes an operation that was once available, it is conceivable that someone was using it as the basis of a security policy. However, since the most logical course for such a policy to take in the face of a lack of positive response from a server is to deny authentication/authorization, it is highly unlikely that removing support for IQUERY will open any new security holes. Note that if IQUERY is not obsoleted, securing the responses with DNSSEC is extremely difficult without out-on-the-fly digital signing. 5 - IANA Considerations: The IQUERY opcode of 1 should be permanently retired, not to be assigned to any future opcode. 6 - Acknowledgments: Olafur Gudmundsson was the instigator for this action. Matt Crawford contributed some improved wording to the Introduction.wording. References: [RFC1035] P. Mockapetris, ``Domain Names - Implementation and Specification'', STD 13, RFC 1035, November 1987. 7 - Author's Address David Lawrence Nominum, Inc. 950 Charter St Redwood City CA 94063 USA Phone: +1.650.779.6042 EMail: email@example.com Full Copyright Statement Copyright (C) The Internet Society (2001). 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."