--- 1/draft-ietf-dprive-phase2-requirements-01.txt 2020-11-02 15:13:59.034111833 -0800 +++ 2/draft-ietf-dprive-phase2-requirements-02.txt 2020-11-02 15:13:59.050112058 -0800 @@ -1,44 +1,48 @@ DPRIVE J. Livingood Internet-Draft Comcast Intended status: Informational A. Mayrhofer -Expires: December 18, 2020 nic.at GmbH +Expires: May 6, 2021 nic.at GmbH B. Overeinder NLnet Labs - June 16, 2020 + November 02, 2020 DNS Privacy Requirements for Exchanges between Recursive Resolvers and Authoritative Servers - draft-ietf-dprive-phase2-requirements-01 + draft-ietf-dprive-phase2-requirements-02 Abstract - This document provides requirements for adding confidentiality to DNS - exchanges between recursive resolvers and authoritative servers. + This document describes requirements and considerations for adding + confidentiality to DNS exchanges between recursive resolvers and + authoritative servers. The intent of this document is to guide + Internet Drafts in the DNS Private Exchange (DPRIVE) Working Group + pertaining to recursive to authorized name servers, with the stated + requirements and considerations. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on December 18, 2020. + This Internet-Draft will expire on May 6, 2021. Copyright Notice Copyright (c) 2020 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 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -47,43 +51,43 @@ 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. Table of Contents 1. Introduction & Scope . . . . . . . . . . . . . . . . . . . . 2 2. Document Work Via GitHub . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Threat Model and Problem Statement . . . . . . . . . . . . . 3 - 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4 - 5.1. Mandatory Requirements . . . . . . . . . . . . . . . . . 4 - 5.2. Optional Requirements . . . . . . . . . . . . . . . . . . 5 + 5. Features to Provide Confidentiality . . . . . . . . . . . . . 4 + 5.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 4 + 5.2. Optional Features . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 - 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 9. APPENDIX: Perspectives and Use Cases . . . . . . . . . . . . 5 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 + 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 9. APPENDIX: Perspectives and Use Cases . . . . . . . . . . . . 6 9.1. The User Perspective and Use Cases . . . . . . . . . . . 6 - 9.2. The Operator Perspective and Use Cases . . . . . . . . . 6 + 9.2. The Operator Perspective and Use Cases . . . . . . . . . 7 9.3. The Implementor / Software Vendor Perspective and Use - Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 8 + Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 10.2. Informative References . . . . . . . . . . . . . . . . . 9 - 10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction & Scope The 2018 approved charter of the IETF DPRIVE Working Group [1] contains milestones related to confidentiality aspects of DNS - transactions between the iterative resolver and authoritative name + transactions between the recursive resolver and authoritative name servers. This is also reflected in the DPRIVE milestones [2], which (as of October 2019) contains two relevant milestones: Develop requirements for adding confidentiality to DNS exchanges between recursive resolvers and authoritative servers (unpublished document). Investigate potential solutions for adding confidentiality to DNS @@ -133,106 +137,124 @@ are still possible when performed by the recursive resolver, which decrypts queries, serves a response from cache or performs recursion to obtain a response (or synthesizes a response), and then encrypts the response and sends it back to the user's stub resolver. But observation and modification threats still exist when a recursive resolver must perform DNS recursion, from the root to TLD to authoritative servers. This document specifies requirements for filling those gaps. -5. Requirements +5. Features to Provide Confidentiality - The requirements of different interested stakeholders are outlined - below. + Confidentialty can be provided using a combination of techniques. + This section describes the protocol implementation requirements and + optional features that can be used to provide confidentiality. -5.1. Mandatory Requirements +5.1. Requirements - 1. Each implementing party should be able to independently take + 1. Each implementing party MUST be able to independently take incremental steps to meet requirements without the need for close coordination (e.g. loosely coupled) - 2. Use a secure transport protocol between a recursive resolver and - authoritative servers + 2. A recursive resolver that supports recursive-to-authoritative + DNS encryption MUST be able to determine whether or not a given + authoritative name server to which it intends to connect also + supports recursive-to-authoritative DNS encryption. - 3. Use a secure transport protocol between a recursive resolver and - TLD servers + 3. An authoritative name server that supports recursive-to- + authoritative DNS encryption MUST be able to indicate that it + supports recursive-to-authoritative DNS encryption in a way that + facilitates (2). - 4. Use a secure transport protocol between a recursive resolver and - the root servers + 4. An authoritative name server that does not support recursive-to- + authoritative MUST NOT have to make any changes to facilitate + (2). 5. The secure transport MUST only be established when referential integrity can be verified, MUST NOT have circular dependencies, and MUST be easily analyzed for diagnostic purposes. - 6. Use a secure transport protocol or other DNS privacy protections - in a manner that enables operators to perform appropriate - performance and security monitoring, conduct relevant research, - etc. + 6. Each implementing party MUST be able to negotiate use of a + secure transport protocol or other DNS privacy protections in a + manner that enables operators to perform appropriate performance + and security monitoring, conduct relevant research, etc. 7. The authoritative domain owner or their administrator MUST have the option to specify their secure transport preferences (e.g. what specific protocols are supported). This SHALL include a method to publish a list of secure transport protocols (e.g. DoH, DoT and other future protocols not yet developed). In addition this SHALL include whether a secure transport protocol MUST always be used (non-downgradable) or whether a secure transport protocol MAY be used on an opportunistic (not strict) - basis. + basis in recognition that some servers for a domain might use a + secure transport protocol and others might not. 8. The authoritative domain owner or their administrator MUST have the option to vary their preferences on an authoritative nameserver to nameserver basis, due to the fact that administration of a particular DNS zone may be delegated to multiple parties (such as several CDNs), each of which may have - different technical capabilities. + different technical capabilities. This includes that some + servers for a domain may use secure transport and others may + not, as it is common for a given name server to be authoritative + for multiple zones. - 9. The specification of secure transport preferences MUST be + 9. A given name server may be authoritative for multiple zones. As + such, a name server MAY support use of a secure transport + protocol for one zone, but not for another. + + 10. The specification of secure transport preferences MUST be performed using the DNS and MUST NOT depend on non-DNS protocols. - 10. For the secure transport, TLS 1.3 (or later versions) MUST be - supported and downgrades from TLS 1.3 to prior versions MUST not - occur. + 11. For secure transports using TLS, TLS 1.3 (or later versions) + MUST be supported and downgrades from TLS 1.3 to prior versions + MUST not occur. -5.2. Optional Requirements +5.2. Optional Features 1. QNAME minimisation SHOULD be implemented in all steps of recursion 2. DNSSEC validation SHOULD be performed 3. If an authoritative domain owner or their administrator indicates - that (1) multiple secure transport protocols are available or + that (1) multiple secure transport protocols are available, or that (2) a secure transport and insecure transport are available, - then per the recommendations in [RFC8305] (aka Happy Eyeballs) a - recursive server SHOULD initiate concurrent connections to - available protocols. Consistent with Section 2 of [RFC8305] this - would be: (1) Initiation of asynchronous DNS queries to determine - what transport protocols are supported, (2) Sorting of resolved - destination transport protocols, (3) Initiation of asynchronous - connection attempts, and (4) Establishment of one connection, - which cancels all other attempts. + or that (3) no secure transport is available, then a recursive + server SHOULD negotiate selection of an available transport + protocol. 6. Security Considerations - This entire document concerns the security of DNS traffic, so a - specific section on security is superfluous. + Authoritative name servers will need to perform additional processing + steps, such as completing key exchanges and maintaining persistent + connections, when responding to queries from a recursive resolver + that requests use of a secure transport protocol. These additional + processing steps can have an impact on server availability if they + are abused. As such, negotiation and use of a secure transport + protocol should be done in a manner that does not increase the risk + of an authoritative name server outage or lead a recursive server to + fail to communicate with an authoritative name server. 7. IANA Considerations This document has no actions for IANA. 8. Changelog Version 00: Updated prior individual draft following IETF-106 - feedback + feedback Version 01: Small editorial changes Version 02: Incorporate + feedback and suggestions from Scott Hollenbeck, Duane Wessels and + email discussions. 9. APPENDIX: Perspectives and Use Cases The DNS resolving process involves several entities. These entities have different interests/requirements, and hence it does make sense to examine the interests of those entities separately - though in many cases their interests are aligned. Four different entities can be identified, and their interests are described in the following sections: @@ -405,34 +427,32 @@ 2012, . [RFC7816] Bortzmeyer, S., "DNS Query Name Minimisation to Improve Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016, . [RFC8198] Fujiwara, K., Kato, A., and W. Kumari, "Aggressive Use of DNSSEC-Validated Cache", RFC 8198, DOI 10.17487/RFC8198, July 2017, . - [RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2: - Better Connectivity Using Concurrency", RFC 8305, - DOI 10.17487/RFC8305, December 2017, - . - 10.3. URIs [1] https://datatracker.ietf.org/doc/charter-ietf-dprive/ [2] https://datatracker.ietf.org/wg/dprive/about/ Acknowledgments - TODO + The authors would like to thank Scott Hollenbeck for his early + feedback and providing text for the Internet Draft. We would also + like to thank Duane Wessels for the feedback on the mailing list, and + Peter van Dijk for his comments in personal conversations. Authors' Addresses Jason Livingood Comcast Email: Jason_Livingood@comcast.com Alexander Mayrhofer nic.at GmbH