draft-ietf-dnsop-server-cookies-00.txt		draft-ietf-dnsop-server-cookies-01.txt
	DNSOP Working Group O. Sury		DNSOP Working Group O. Sury
	Internet-Draft Internet Systems Consortium		Internet-Draft Internet Systems Consortium
	Updates: 7873 (if approved) W. Toorop		Updates: 7873 (if approved) W. Toorop
	Intended status: Standards Track NLnet Labs		Intended status: Standards Track NLnet Labs
	Expires: March 12, 2020 D. Eastlake 3rd		Expires: May 7, 2020 D. Eastlake 3rd
	Futurewei Technologies		Futurewei Technologies
	M. Andrews		M. Andrews
	Internet Systems Consortium		Internet Systems Consortium
	September 9, 2019		November 4, 2019
	Interoperable Domain Name System (DNS) Server Cookies		Interoperable Domain Name System (DNS) Server Cookies
	draft-ietf-dnsop-server-cookies-00		draft-ietf-dnsop-server-cookies-01
	Abstract		Abstract
	DNS cookies, as specified in RFC 7873, are a lightweight DNS		DNS cookies, as specified in RFC 7873, are a lightweight DNS
	transaction security mechanism that provides limited protection to		transaction security mechanism that provides limited protection to
	DNS servers and clients against a variety of denial-of-service and		DNS servers and clients against a variety of denial-of-service and
	amplification, forgery, or cache poisoning attacks by off-path		amplification, forgery, or cache poisoning attacks by off-path
	attackers.		attackers.
	This document provides precise directions for creating Server Cookies		This document provides precise directions for creating Server Cookies
	skipping to change at page 1, line 45 ¶		skipping to change at page 1, line 45 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on March 12, 2020.		This Internet-Draft will expire on May 7, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 28 ¶		skipping to change at page 2, line 28 ¶
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Contents of this document . . . . . . . . . . . . . . . . 3		1.1. Contents of this document . . . . . . . . . . . . . . . . 3
	1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4		1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Changes to [RFC7873] . . . . . . . . . . . . . . . . . . . . 4		2. Changes to [RFC7873] . . . . . . . . . . . . . . . . . . . . 4
	3. Constructing a Client Cookie . . . . . . . . . . . . . . . . 4		3. Constructing a Client Cookie . . . . . . . . . . . . . . . . 4
	4. Constructing a Server Cookie . . . . . . . . . . . . . . . . 5		4. Constructing a Server Cookie . . . . . . . . . . . . . . . . 5
	4.1. The Version Sub-Field . . . . . . . . . . . . . . . . . . 5		4.1. The Version Sub-Field . . . . . . . . . . . . . . . . . . 6
	4.2. The Reserved Sub-Field . . . . . . . . . . . . . . . . . 5		4.2. The Reserved Sub-Field . . . . . . . . . . . . . . . . . 6
	4.3. The Timestamp Sub-Field . . . . . . . . . . . . . . . . . 6		4.3. The Timestamp Sub-Field . . . . . . . . . . . . . . . . . 6
	4.4. The Hash Sub-Field . . . . . . . . . . . . . . . . . . . 6		4.4. The Hash Sub-Field . . . . . . . . . . . . . . . . . . . 6
	5. Updating the Server Secret . . . . . . . . . . . . . . . . . 6		5. Updating the Server Secret . . . . . . . . . . . . . . . . . 7
	6. Cookie Algorithms . . . . . . . . . . . . . . . . . . . . . . 8		6. Cookie Algorithms . . . . . . . . . . . . . . . . . . . . . . 8
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
	8.1. Normative References . . . . . . . . . . . . . . . . . . 8		8.1. Normative References . . . . . . . . . . . . . . . . . . 9
	8.2. Informative References . . . . . . . . . . . . . . . . . 9		8.2. Informative References . . . . . . . . . . . . . . . . . 9
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9		Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 10
	Appendix B. Test vectors . . . . . . . . . . . . . . . . . . . . 9		Appendix B. Test vectors . . . . . . . . . . . . . . . . . . . . 10
	B.1. Learning a new Server Cookie . . . . . . . . . . . . . . 9		B.1. Learning a new Server Cookie . . . . . . . . . . . . . . 10
	B.2. The same client learning a renewed (fresh) Server Cookie 10		B.2. The same client learning a renewed (fresh) Server Cookie 11
	B.3. Another client learning a renewed Server Cookie . . . . . 11		B.3. Another client learning a renewed Server Cookie . . . . . 12
	B.4. IPv6 query with rolled over secret . . . . . . . . . . . 12		B.4. IPv6 query with rolled over secret . . . . . . . . . . . 13
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
	1. Introduction		1. Introduction
	DNS cookies, as specified in [RFC7873], are a lightweight DNS		DNS cookies, as specified in [RFC7873], are a lightweight DNS
	transaction security mechanism that provides limited protection to		transaction security mechanism that provides limited protection to
	DNS servers and clients against a variety of denial-of-service and		DNS servers and clients against a variety of denial-of-service and
	amplification, forgery, or cache poisoning attacks by off-path		amplification, forgery, or cache poisoning attacks by off-path
	attackers. This document specifies a means of producing		attackers. This document specifies a means of producing
	interoperable strong cookies so that an anycast server set including		interoperable strong cookies so that an anycast server set including
	diverse implementations can be easily configured to interoperate with		diverse implementations can be easily configured to interoperate with
	skipping to change at page 4, line 34 ¶		skipping to change at page 4, line 34 ¶
	server algorithm. This algorithm is replaced by the interoperable		server algorithm. This algorithm is replaced by the interoperable
	specification in Section 4 of this document, which MUST be used by		specification in Section 4 of this document, which MUST be used by
	Server Cookie implementations.		Server Cookie implementations.
	This document has suggestions on Client Cookie construction in		This document has suggestions on Client Cookie construction in
	Section 3. The previous example in Appendix A.2 of [RFC7873] is NOT		Section 3. The previous example in Appendix A.2 of [RFC7873] is NOT
	RECOMMENDED.		RECOMMENDED.
	3. Constructing a Client Cookie		3. Constructing a Client Cookie
	The Client Cookie is a nonce and should be treated as such. For		The Client Cookie is a cryptographic nonce and should be treated as
	simplicity, it can be calculated from Server IP Address, and a secret		such. For simplicity, it can be calculated from Server IP Address,
	known only to the Client. The Client Cookie SHOULD have at least		and a Client Secret known only to the Client that is changed whenever
	64-bits of entropy. If a secure pseudorandom function (like		an IP address previously used by the Client is no longer available.
	[SipHash-2.4]) is used, there's no need to change Client secret		The Client Cookie SHOULD have at least 64-bits of entropy.
	often. It is reasonable to change the Client secret only if it has
	been compromised or after a relatively long period of time such as no		Except for when the Client IP address changes, there is no need to
	longer than a year.		change the Client Secret often if a secure pseudorandom function
			(like [SipHash-2.4]) is used. It is reasonable to change the Client
			secret then only if it has been compromised or after a relatively
			long period of time such as no longer than a year.
	It is RECOMMENDED but not required that the following pseudorandom		It is RECOMMENDED but not required that the following pseudorandom
	function be used to construct the Client Cookie:		function be used to construct the Client Cookie:
	Client-Cookie = MAC_Algorithm(		Client-Cookie = MAC_Algorithm(
	Server IP Address, Client Secret )		Server IP Address, Client Secret )
	where "|" indicates concatenation.
	Previously, the recommended algorithm to compute the Client Cookie		Previously, the recommended algorithm to compute the Client Cookie
	included Client IP Address as an input to the MAC_Algorithm.		included Client IP Address as an input to the MAC_Algorithm.
	However, when implementing the DNS Cookies, several DNS vendors found		However, when implementing the DNS Cookies, several DNS vendors found
	impractical to include the Client IP as the Client Cookie is		impractical to include the Client IP as the Client Cookie is
	typically computed before the Client IP address is known. Therefore,		typically computed before the Client IP address is known. Therefore,
	the requirement to put Client IP address as input to was removed, and		the requirement to put Client IP address as input was removed.
	it simply RECOMMENDED to disable the DNS Cookies when privacy is
	required.		However, for privacy reasons, in order to prevent tracking of devices
			across links and to not circumvent IPv6 Privacy Extensions [RFC4941],
			Clients MUST NOT re-use a Client or Server Cookie after the Client IP
			address has changed.
			The Client IP address is available on the UDP socket when it receives
			the Server Cookie and should be registered alongside the Server
			Cookie. In subsequent queries to the Server with that Server Cookie,
			the socket MUST be bound to the Client IP address that was also used
			(and registered) when it received the Server Cookie. Failure to bind
			must result in a new Client Cookie, which, for the method described
			in this section means a new Client Secret.
	4. Constructing a Server Cookie		4. Constructing a Server Cookie
	The Server Cookie is effectively a Message Authentication Code (MAC)		The Server Cookie is effectively a Message Authentication Code (MAC)
	and should be treated as such. The Server Cookie is calculated from		and should be treated as such. The Server Cookie is calculated from
	the Client Cookie, a series of Sub-Fields specified below, the Client		the Client Cookie, a series of Sub-Fields specified below, the Client
	IP address, and a Server Secret known only to the servers responding		IP address, and a Server Secret known only to the servers responding
	on the same address in an anycast set.		on the same address in an anycast set.
	Changing the Server Secret regularly is RECOMMENDED but, when a		Changing the Server Secret regularly is RECOMMENDED but, when a
	skipping to change at page 6, line 34 ¶		skipping to change at page 6, line 46 ¶
	4.4. The Hash Sub-Field		4.4. The Hash Sub-Field
	It's important that all the DNS servers use the same algorithm for		It's important that all the DNS servers use the same algorithm for
	computing the Server Cookie. This document defines the Version 1 of		computing the Server Cookie. This document defines the Version 1 of
	the Server Side algorithm to be:		the Server Side algorithm to be:
	Hash = SipHash2.4(		Hash = SipHash2.4(
	Client Cookie | Version | Reserved | Timestamp | Client-IP,		Client Cookie | Version | Reserved | Timestamp | Client-IP,
	Server Secret )		Server Secret )
			where "|" indicates concatenation.
	Notice that Client-IP is used for hash generation even though it's		Notice that Client-IP is used for hash generation even though it's
	not included in the cookie value itself. Client-IP can be either 4		not included in the cookie value itself. Client-IP can be either 4
	bytes for IPv4 or 16 bytes for IPv6.		bytes for IPv4 or 16 bytes for IPv6.
	The Server Secret MUST be configurable to make sure that servers in		The Server Secret MUST be configurable to make sure that servers in
	an anycast network return consistent results.		an anycast network return consistent results.
	5. Updating the Server Secret		5. Updating the Server Secret
	All servers in an anycast group must be able to verify the Server		All servers in an anycast group must be able to verify the Server
	skipping to change at page 9, line 41 ¶		skipping to change at page 10, line 13 ¶
	<https://www.rfc-editor.org/info/rfc6234>.		<https://www.rfc-editor.org/info/rfc6234>.
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	Thanks to Witold Krecicki and Pieter Lexis for valuable input,		Thanks to Witold Krecicki and Pieter Lexis for valuable input,
	suggestions and text and above all for implementing a prototype of an		suggestions and text and above all for implementing a prototype of an
	interoperable DNS Cookie in Bind9, Knot and PowerDNS during the		interoperable DNS Cookie in Bind9, Knot and PowerDNS during the
	hackathon of IETF104 in Prague. Thanks for valuable input and		hackathon of IETF104 in Prague. Thanks for valuable input and
	suggestions go to Ralph Dolmans, Bob Harold, Daniel Salzman, Martin		suggestions go to Ralph Dolmans, Bob Harold, Daniel Salzman, Martin
	Hoffmann, Mukund Sivaraman, Petr Spacek, Loganaden Velvindron, Bob		Hoffmann, Mukund Sivaraman, Petr Spacek, Loganaden Velvindron, Bob
	Harold		Harold and Philip Homburg
	Appendix B. Test vectors		Appendix B. Test vectors
	B.1. Learning a new Server Cookie		B.1. Learning a new Server Cookie
	A resolver (client) sending from IPv4 address 198.51.100.100, sends a		A resolver (client) sending from IPv4 address 198.51.100.100, sends a
	query for "example.com" to an authoritative server listening on		query for "example.com" to an authoritative server listening on
	192.0.2.53 from which it has not yet learned the server cookie.		192.0.2.53 from which it has not yet learned the server cookie.
	The DNS requests and replies shown in this Appendix, are in a "dig"		The DNS requests and replies shown in this Appendix, are in a "dig"
End of changes. 14 change blocks.
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