DNS Privacy Considerations

RFC 7626

Internet Engineering Task Force (IETF) S. Bortzmeyer Request for Comments: 7626 AFNIC Category: Informational August 2015 ISSN: 2070-1721 DNS Privacy Considerations Abstract This document describes the privacy issues associated with the use of the DNS by Internet users. It is intended to be an analysis of the present situation and does not prescribe solutions. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7626. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Bortzmeyer Informational [Page 1] RFC 7626 DNS Privacy August 2015 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. The Alleged Public Nature of DNS Data . . . . . . . . . . 4 2.2. Data in the DNS Request . . . . . . . . . . . . . . . . . 5 2.3. Cache Snooping . . . . . . . . . . . . . . . . . . . . . 6 2.4. On the Wire . . . . . . . . . . . . . . . . . . . . . . . 7 2.5. In the Servers . . . . . . . . . . . . . . . . . . . . . 8 2.5.1. In the Recursive Resolvers . . . . . . . . . . . . . 8 2.5.2. In the Authoritative Name Servers . . . . . . . . . . 9 2.5.3. Rogue Servers . . . . . . . . . . . . . . . . . . . . 10 2.6. Re-identification and Other Inferences . . . . . . . . . 11 2.7. More Information . . . . . . . . . . . . . . . . . . . . 11 3. Actual "Attacks" . . . . . . . . . . . . . . . . . . . . . . 11 4. Legalities . . . . . . . . . . . . . . . . . . . . . . . . . 12 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.1. Normative References . . . . . . . . . . . . . . . . . . 12 6.2. Informative References . . . . . . . . . . . . . . . . . 13 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 1. Introduction This document is an analysis of the DNS privacy issues, in the spirit of Section 8 of [RFC6973]. The Domain Name System is specified in [RFC1034], [RFC1035], and many later RFCs, which have never been consolidated. It is one of the most important infrastructure components of the Internet and often ignored or misunderstood by Internet users (and even by many professionals). Almost every activity on the Internet starts with a DNS query (and often several). Its use has many privacy implications and this is an attempt at a comprehensive and accurate list. Let us begin with a simplified reminder of how the DNS works. (See also [DNS-TERMS].) A client, the stub resolver, issues a DNS query to a server, called the recursive resolver (also called caching resolver or full resolver or recursive name server). Let's use the query "What are the AAAA records for www.example.com?" as an example. AAAA is the QTYPE (Query Type), and www.example.com is the QNAME (Query Name). (The description that follows assumes a cold cache, for instance, because the server just started.) The recursive resolver will first query the root name servers. In most cases, the root name servers will send a referral. In this example, the referral will be to the .com name servers. The resolver repeats the query to one of the .com name servers. The .com name servers, in Bortzmeyer Informational [Page 2]