DNSEXT Working Group David C Lawrence INTERNET-DRAFT Nominum
<draft-ietf-dnsext-obsolete-iquery-03.txt> January<draft-ietf-dnsext-obsolete-iquery-04.txt> July 2002 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.RFC 2026. 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 email@example.com. This draft expires on 14 July 2002.January 2003. Copyright Notice Copyright (C) The Internet Society (2002). All rights reserved. Abstract The IQUERY method of performing inverse DNS lookups, specified in RFC 1035, has not been generally implemented and has usually been operationally disabled where it has been implemented. Both reflect a general view in the community that the concept was unwise and that the widely-used alternate approach of using PTR queries and reverse-mapping records is preferable. Consequently, this document deprecates the IQUERY operation and updates RFC 1035 to declare it entirely obsolete. 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. 1.12 - Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"word "SHOULD" in this document areis to be interpreted as described in RFC 2119. 1.2 - Updated documents2119, namely that there may exit valid reasons to ignore a particular item, but the full implications must be understood and sections Incarefully weighed before choosing a different course. 3 - Effect on RFC 1035, sections 4.1.11035 The effect of this document is updatedto change the definition of opcode 1 from that originally defined in partsection 4.1.1 of RFC 1035, and to entirely supersede section 6.4 is entirely superseded. 2 - New text for(including subsections) of RFC 1035. Section 4.1.1 has the following text to describeThe definition of opcode 1: "1 an inverse query (IQUERY)" It1 is now considered to read as follows:hereby changed to: "1 an inverse query (IQUERY) (obsolete)" Section 6.4, including all subsections,The text in section 6.4 of RFC 1035 should beis now considered obsolete and not to be implemented.obsolete. The section effectively now reads as follows: "Inversefollowing is an applicability statement regarding the IQUERY opcode: 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."received. 4 - Security Considerations: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:Considerations The IQUERY opcode of 1 should be permanently retired, not to be assigned to any future opcode. 6 - Acknowledgments:Acknowledgments Olafur Gudmundsson was the instigator for this action. Matt Crawford, John Klensin andKlensin, Erik Nordmark and Keith Moore contributed some improved wording. References:wording as the matter of how to handle obsoleting functionality described by an Internet Standard. 7 - References [RFC1035] P. Mockapetris, ``Domain Names - Implementation and Specification'', STD 13, RFC 1035, November 1987. [RFC2026] S. Bradner, ``The Internet Standards Process -- Revision 3'', BCP 9, RFC 2026, October 1996. [RFC2119] S. Bradner, ``Key Words for Use in RFCs to Indicate Requirement Levels'', BCP 14, RFC 2119, March 1997. 78 - Author's Address David C Lawrence Nominum, Inc. 950 Charter St2385 Bay Rd Redwood City CA 94063 USA Phone: +1.650.779.6042 EMail: firstname.lastname@example.org 9 - Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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