draft-ietf-dnsop-server-cookies-03.txt   draft-ietf-dnsop-server-cookies-04.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: November 21, 2020 D. Eastlake 3rd Expires: 23 May 2021 D. Eastlake 3rd
Futurewei Technologies Futurewei Technologies
M. Andrews M. Andrews
Internet Systems Consortium Internet Systems Consortium
May 20, 2020 19 November 2020
Interoperable Domain Name System (DNS) Server Cookies Interoperable Domain Name System (DNS) Server Cookies
draft-ietf-dnsop-server-cookies-03 draft-ietf-dnsop-server-cookies-04
Abstract Abstract
DNS cookies, as specified in RFC 7873, 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 provide limited protection to DNS
DNS servers and clients against a variety of denial-of-service and 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
so that an anycast server set including diverse implementations will so that an anycast server set including diverse implementations will
interoperate with standard clients. interoperate with standard clients.
This document updates [RFC7873] This document updates [RFC7873] with
* suggestions for constructing Client Cookies in a privacy
preserving fashion,
* precise instructions for constructing Server Cookies deprecating
the methods described in [RFC7873], and
* suggestions on how to update a server secret.
An IANA registry listing the methods and associated pseudo random
function suitable for creating DNS Server cookies is created, with
the method described in this document as the first and as of yet only
entry.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 November 21, 2020. This Internet-Draft will expire on 23 May 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Contents of this document . . . . . . . . . . . . . . . . 3 1.1. Contents of this document . . . . . . . . . . . . . . . . 3
1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology and 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 . . . . . . . . . . . . . . . . . . 6 4.1. The Version Sub-Field . . . . . . . . . . . . . . . . . . 6
4.2. The Reserved Sub-Field . . . . . . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . . . . . . 7
5. Updating the Server Secret . . . . . . . . . . . . . . . . . 7 5. Updating the Server Secret . . . . . . . . . . . . . . . . . 7
6. Cookie Algorithms . . . . . . . . . . . . . . . . . . . . . . 8 6. Cookie Algorithms . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security and Privacy Considerations . . . . . . . . . . . . . 9 8. Security and Privacy Considerations . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10 10. Normative References . . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10 11. Informative References . . . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11 Appendix A. Test vectors . . . . . . . . . . . . . . . . . . . . 11
Appendix B. Test vectors . . . . . . . . . . . . . . . . . . . . 11 A.1. Learning a new Server Cookie . . . . . . . . . . . . . . 11
B.1. Learning a new Server Cookie . . . . . . . . . . . . . . 11 A.2. The same client learning a renewed (fresh) Server
B.2. The same client learning a renewed (fresh) Server Cookie 12 Cookie . . . . . . . . . . . . . . . . . . . . . . . . . 12
B.3. Another client learning a renewed Server Cookie . . . . . 13 A.3. Another client learning a renewed Server Cookie . . . . . 13
B.4. IPv6 query with rolled over secret . . . . . . . . . . . 14 A.4. IPv6 query with rolled over secret . . . . . . . . . . . 14
Appendix C. Implementation status . . . . . . . . . . . . . . . 15 Appendix B. Implementation status . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
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 provide limited protection to DNS
DNS servers and clients against a variety of denial-of-service and 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
standard clients. standard clients.
The threats considered for DNS Cookies and the properties of the DNS The threats considered for DNS Cookies and the properties of the DNS
Security features other than DNS Cookies are discussed in [RFC7873]. Security features other than DNS Cookies are discussed in [RFC7873].
In [RFC7873] in Section 6 it is "RECOMMENDED for simplicity that the In [RFC7873] in Section 6 it is "RECOMMENDED for simplicity that the
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by one implementation cannot generally be validated by another. by one implementation cannot generally be validated by another.
There is no need for DNS client (resolver) Cookies to be There is no need for DNS client (resolver) Cookies to be
interoperable across different implementations. Each client need interoperable across different implementations. Each client need
only be able to recognize its own cookies. However, this document only be able to recognize its own cookies. However, this document
does contain recommendations for constructing Client Cookies in a does contain recommendations for constructing Client Cookies in a
Client protecting fashion. Client protecting fashion.
1.1. Contents of this document 1.1. Contents of this document
Section Section 2 summarises the changes to [RFC7873]. Section 2 summarises the changes to [RFC7873].
In Section Section 3 suggestions for constructing a Client Cookie are In Section 3 suggestions for constructing a Client Cookie are given.
given.
In Section Section 4 instructions for constructing a Server Cookie In Section 4 instructions for constructing a Server Cookie are given.
are given.
In Section Section 5 instructions on updating Server Secrets are In Section 5 instructions on updating Server Secrets are given.
given.
In Section Section 6 the different hash functions usable for DNS In Section 6 the different hash functions usable for DNS Cookie
Cookie construction are listed. [FNV] and HMAC-SHA-256-64 [RFC6234] construction are listed. [FNV] and HMAC-SHA-256-64 [RFC6234] are
are deprecated and [SipHash-2.4] is introduced as a REQUIRED hash deprecated and [SipHash-2.4] is introduced as a REQUIRED hash
function for server side DNS Cookie implementations. function for server side DNS Cookie implementations.
IANA considerations are in Section 7. IANA considerations are in Section 7.
Privacy and Security Considerations in Section 8. Privacy and Security Considerations in Section 8.
Acknowledgements are in Appendix A. Acknowledgements are in Section 9.
Test vectors are in Appendix B. Test vectors are in Appendix A.
1.2. Definitions 1.2. Terminology and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "*NOT RECOMMENDED*", "MAY", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
and "OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in BCP
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
o "IP Address" is used herein as a length independent term covering * "IP Address" is used herein as a length independent term covering
both IPv4 and IPv6 addresses. both IPv4 and IPv6 addresses.
2. Changes to [RFC7873] 2. Changes to [RFC7873]
In its Appendices A.1 and B.1, [RFC7873] provides example "simple" In its Appendices A.1 and B.1, [RFC7873] provides example "simple"
algorithms for computing Client and Server Cookies, respectively. algorithms for computing Client and Server Cookies, respectively.
These algorithms MUST NOT be used as the resulting cookies are too These algorithms MUST NOT be used as the resulting cookies are too
weak when evaluated against modern security standards. weak when evaluated against modern security standards.
In its Appendix B.2, [RFC7873] provides an example "more complex" In its Appendix B.2, [RFC7873] provides an example "more complex"
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3. Constructing a Client Cookie 3. Constructing a Client Cookie
The Client Cookie is a cryptographic nonce and should be treated as The Client Cookie is a cryptographic nonce and should be treated as
such. It is RECOMMENDED to create a new Client Cookie for each new such. It is RECOMMENDED to create a new Client Cookie for each new
upstream server a Client connects to. The Client Cookie SHOULD have upstream server a Client connects to. The Client Cookie SHOULD have
64-bits of entropy. 64-bits of entropy.
When a Server does not support DNS Cookies, the Client MUST NOT send When a Server does not support DNS Cookies, the Client MUST NOT send
the same Client Cookie to that same Server again. Instead, it is the same Client Cookie to that same Server again. Instead, it is
recommended that the Client does not send a Client Cookie to that recommended that the Client does not send a Client Cookie to that
Server for a certain period, like for example five minutes, before it Server for a certain period, for example five minutes, before it
retries with a new Client Cookie. retries with a new Client Cookie.
When a Server does support DNS Cookies, the Client should store the When a Server does support DNS Cookies, the Client should store the
Client Cookie alongside the Server Cookie it registered for that Client Cookie alongside the Server Cookie it registered for that
Server. Server.
Except for when the Client IP address changes, there is no need to Except for when the Client IP address changes, there is no need to
change the Client Cookie often. It is reasonable to change the change the Client Cookie often. It is reasonable to change the
Client Cookie then only if it has been compromised or after a Client Cookie then only if it has been compromised or after a
relatively long period of time such as no longer than a year. Client relatively long period of time such as no longer than a year. Client
Cookies are not expected to survive a program restart. Cookies are not expected to survive a program restart.
Client-Cookie = 64 bits of entropy Client-Cookie = 64 bits of entropy
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 a hashing function. included Client IP Address as an input to a hashing function.
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 was removed. the requirement to put Client IP address as input was removed.
However, for privacy reasons, in order to prevent tracking of devices However, for privacy reasons, in order to prevent tracking of devices
across links and to not circumvent IPv6 Privacy Extensions [RFC4941], across links and to not circumvent IPv6 Privacy Extensions [RFC4941],
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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
secure pseudorandom function is used, it need not be changed too secure pseudorandom function is used, it need not be changed too
frequent. For example once a month would be adequate. See Section 5 frequently. For example once a month would be adequate. See
on operator and implementation guidelines for updating a Server Section 5 on operator and implementation guidelines for updating a
Secret. Server Secret.
The 128-bit Server Cookie consists of Sub-Fields: a 1 octet Version The 128-bit Server Cookie consists of Sub-Fields: a 1 octet Version
Sub-Field, a 3 octet Reserved Sub-Field, a 4 octet Timestamp Sub- Sub-Field, a 3 octet Reserved Sub-Field, a 4 octet Timestamp Sub-
Field and an 8 octet Hash Sub-Field. Field and an 8 octet Hash Sub-Field.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved | | Version | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp | | Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hash | | Hash |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1. The Version Sub-Field 4.1. The Version Sub-Field
The Version Sub-Field prescribes the structure and Hash calculation The Version Sub-Field prescribes the structure and Hash calculation
formula. This document defines Version 1 to be the structure and way formula. This document defines Version 1 to be the structure and way
to calculate the Hash Sub-Field as defined in this Section. to calculate the Hash Sub-Field as defined in this Section.
4.2. The Reserved Sub-Field 4.2. The Reserved Sub-Field
The value of the Reserved Sub-Field is reserved for future versions The value of the Reserved Sub-Field is reserved for future versions
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to zero octets. On Server Cookie verification the server MUST NOT to zero octets. On Server Cookie verification the server MUST NOT
enforce those fields to be zero and the Hash should be computed with enforce those fields to be zero and the Hash should be computed with
the received value as described in Section 4.4. the received value as described in Section 4.4.
4.3. The Timestamp Sub-Field 4.3. The Timestamp Sub-Field
The Timestamp value prevents Replay Attacks and MUST be checked by The Timestamp value prevents Replay Attacks and MUST be checked by
the server to be within a defined period of time. The DNS Server the server to be within a defined period of time. The DNS Server
SHOULD allow Cookies within 1 hour period in the past and 5 minutes SHOULD allow Cookies within 1 hour period in the past and 5 minutes
into the future to allow operation of low volume clients and some into the future to allow operation of low volume clients and some
limited time skew between the DNS servers in the anycast. limited time skew between the DNS servers in the anycast set.
The Timestamp value specifies a date and time in the form of a 32-bit The Timestamp value specifies a date and time in the form of a 32-bit
unsigned number of seconds elapsed since 1 January 1970 00:00:00 UTC, unsigned number of seconds elapsed since 1 January 1970 00:00:00 UTC,
ignoring leap seconds, in network byte order. All comparisons ignoring leap seconds, in network byte order. All comparisons
involving these fields MUST use "Serial number arithmetic", as involving these fields MUST use "Serial number arithmetic", as
defined in [RFC1982] defined in [RFC1982]
The DNS Server SHOULD generate a new Server Cookie at least if the The DNS Server SHOULD generate a new Server Cookie at least if the
received Server Cookie from the Client is more than half an hour old. received Server Cookie from the Client is more than half an hour old.
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. 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 set must be able to verify the Server
Cookies constructed by all other servers in that anycast set at all Cookies constructed by all other servers in that anycast set at all
times. Therefore it is vital that the Server Secret is shared among times. Therefore it is vital that the Server Secret is shared among
all servers before it us used to generate Server Cookies. all servers before it is used to generate Server Cookies.
Also, to maximize maintaining established relationships between Also, to maximize maintaining established relationships between
clients and servers, an old Server Secret should be valid for clients and servers, an old Server Secret should be valid for
verification purposes for a specific period. verification purposes for a specific period.
To facilitate this, deployment of a new Server Secret MUST be done in To facilitate this, deployment of a new Server Secret MUST be done in
three stages: three stages:
Stage 1 Stage 1 The new Server Secret is deployed on all the servers in an
The new Server Secret is deployed on all the servers in an anycast anycast set by the operator.
set by the operator.
Each server learns the new Server Secret, but keeps using the
previous Server Secret to generate Server Cookies.
Server Cookies constructed with the both the new Server Secret and
with the previous Server Secret are considered valid when
verifying.
After stage 1 completed, all the servers in the anycast set have
learned the new Server Secret, and can verify Server Cookies
constructed with it, but keep generating Server Cookies with the
old Server Secret.
Stage 2
This stage is initiated by the operator after the Server Cookie is
present on all members in the anycast set.
When entering Stage 2, servers start generating Server Cookies
with the new Server Secret. The previous Server Secret is not yet
removed/forgotten about.
Server Cookies constructed with the both the new Server Secret and | Each server learns the new Server Secret, but keeps using the
with the previous Server Secret are considered valid when | previous Server Secret to generate Server Cookies.
verifying. |
| Server Cookies constructed with the both the new Server Secret and
| with the previous Server Secret are considered valid when
| verifying.
|
| After stage 1 completed, all the servers in the anycast set have
| learned the new Server Secret, and can verify Server Cookies
| constructed with it, but keep generating Server Cookies with the
| old Server Secret.
Stage 3 Stage 2 This stage is initiated by the operator after the Server
This stage is initiated by the operator when it can be assumed Cookie is present on all members in the anycast set.
that most clients have learned the new Server Secret.
With this stage, the previous Server Secret can be removed and | When entering Stage 2, servers start generating Server Cookies
MUST NOT be used anymore for verifying. | with the new Server Secret. The previous Server Secret is not yet
| removed/forgotten about.
|
| Server Cookies constructed with the both the new Server Secret and
| with the previous Server Secret are considered valid when
| verifying.
We RECOMMEND the operator to wait at least a period to be the Stage 3 This stage is initiated by the operator when it can be
longest TTL in the zones served by the server plus half an hour assumed that most clients have learned the new Server Secret.
after it initiated Stage 2, before initiating Stage 3.
The operator SHOULD wait at least longer than the period clients | With this stage, the previous Server Secret can be removed and
are allowed to use the same Server Cookie, which SHOULD be half an | MUST NOT be used anymore for verifying.
hour, see Section 4.3. |
| We RECOMMEND the operator to wait at least a period to be the
| longest TTL in the zones served by the server plus half an hour
| after it initiated Stage 2, before initiating Stage 3.
|
| The operator SHOULD wait at least longer than the period clients
| are allowed to use the same Server Cookie, which SHOULD be half an
| hour, see Section 4.3.
6. Cookie Algorithms 6. Cookie Algorithms
[SipHash-2.4] is a pseudorandom function suitable as Message [SipHash-2.4] is a pseudorandom function suitable as Message
Authentication Code. This document REQUIRES compliant DNS Server to Authentication Code. This document REQUIRES compliant DNS Server to
use SipHash-2.4 as a mandatory and default algorithm for DNS Cookies use SipHash-2.4 as a mandatory and default algorithm for DNS Cookies
to ensure interoperability between the DNS Implementations. to ensure interoperability between the DNS Implementations.
The construction method and pseudorandom function used in calculating The construction method and pseudorandom function used in calculating
and verifying the Server Cookies are determined by the initial and verifying the Server Cookies are determined by the initial
version byte and by the length of the Server Cookie. Additional version byte and by the length of the Server Cookie. Additional
pseudorandom or construction algorithms for Server Cookies might be pseudorandom or construction algorithms for Server Cookies might be
added in the future. added in the future.
7. IANA Considerations 7. IANA Considerations
IANA is requested to create a registry on the "Domain Name System IANA is requested to create a registry on the "Domain Name System
(DNS) Parameters" IANA web page as follows: (DNS) Parameters" IANA web page as follows:
Registry Name: DNS Server Cookie Methods Registry Name: DNS Server Cookie Methods\ Assignment Policy: Expert
Assignment Policy: Expert Review Review\ Reference: [this document], [RFC7873]\ Note: Server Cookie
Reference: [this document], [RFC7873] method (construction and pseudorandom algorithm) are determined by
Note: Server Cookie method (construction and pseudorandom algorithm) the Version in the first byte of the Cookie and by the Cookie size.
are determined by the Version in the first byte of the Cookie and by Server Cookie size is limited to the inclusive range of 8 to 32
the Cookie size. Server Cookie size is limited to the inclusive bytes.
range of 8 to 32 bytes.
Implementation recommendations for Cookie Algorithms [DNSCOOKIE-
IANA]:
+---------+-------+---------------------------------------+ +=========+=======+=======================================+
| Version | Size | Method | | Version | Size | Method |
+---------+-------+---------------------------------------+ +=========+=======+=======================================+
| 0 | 8-32 | reserved | | 0 | 8-32 | reserved |
| 1 | 8-15 | unassiged | +---------+-------+---------------------------------------+
| 1 | 8-15 | unassigned |
+---------+-------+---------------------------------------+
| 1 | 16 | SipHash-2.4 [this document] Section 4 | | 1 | 16 | SipHash-2.4 [this document] Section 4 |
+---------+-------+---------------------------------------+
| 1 | 17-32 | unassigned | | 1 | 17-32 | unassigned |
+---------+-------+---------------------------------------+
| 2-239 | 8-32 | unassigned | | 2-239 | 8-32 | unassigned |
+---------+-------+---------------------------------------+
| 240-254 | 8-32 | private use | | 240-254 | 8-32 | private use |
+---------+-------+---------------------------------------+
| 255 | 8-32 | reserved | | 255 | 8-32 | reserved |
+---------+-------+---------------------------------------+ +---------+-------+---------------------------------------+
Table 1
8. Security and Privacy Considerations 8. Security and Privacy Considerations
DNS Cookies provides limited protection to DNS servers and clients DNS Cookies provide limited protection to DNS servers and clients
against a variety of denial-of-service and amplification/forgery or against a variety of denial-of-service and amplification/forgery or
cache poisoning attacks by off-path attackers. They provide no cache poisoning attacks by off-path attackers. They provide no
protection against on-path adversaries that can observe the plaintext protection against on-path adversaries that can observe the plaintext
DNS traffic. An on-path adversary that can observe a Server Cookie DNS traffic. An on-path adversary that can observe a Server Cookie
for a client and server interaction, can use that Server Cookie for for a client and server interaction, can use that Server Cookie for
amplification and denial-of-service forgery attacks for the lifetime amplification and denial-of-service forgery attacks for the lifetime
of the Server Cookie. of the Server Cookie.
In [RFC7873] it was RECOMMENDED to construct a Client Cookie by using In [RFC7873] it was RECOMMENDED to construct a Client Cookie by using
a pseudorandom function of the Client IP Address, the Server IP a pseudorandom function of the Client IP Address, the Server IP
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prevent tracking of clients. To prevent tracking, a new Client prevent tracking of clients. To prevent tracking, a new Client
Cookie for a server MUST be created whenever the Client IP Address Cookie for a server MUST be created whenever the Client IP Address
changes. changes.
Unfortunately, tracking Client IP Address Changes is impractical with Unfortunately, tracking Client IP Address Changes is impractical with
servers that do not support DNS Cookies. To prevent tracking of servers that do not support DNS Cookies. To prevent tracking of
clients with non DNS Cookie supporting servers, a client MUST NOT clients with non DNS Cookie supporting servers, a client MUST NOT
send a previously sent Client Cookie. To prevent the creation of a send a previously sent Client Cookie. To prevent the creation of a
new Client Cookie for each query to an non DNS Cookies supporting new Client Cookie for each query to an non DNS Cookies supporting
server, it is RECOMMENDED to not send a Client Cookie to that server server, it is RECOMMENDED to not send a Client Cookie to that server
for a certain period, like for example five minute. for a certain period, for example five minute.
Summarizing: Summarizing:
o In order to provide minimal authentication, a client MUST use a * In order to provide minimal authentication, a client MUST use a
different Client Cookie for each different Server IP Address. different Client Cookie for each different Server IP Address.
o To prevent tracking of clients, a new Client Cookie MUST be * To prevent tracking of clients, a new Client Cookie MUST be
created when the Client IP Address changes. created when the Client IP Address changes.
o To prevent tracking of clients for a non DNS Cookie supporting * To prevent tracking of clients for a non DNS Cookie supporting
server, a client MUST NOT send a previously sent Client Cookie to server, a client MUST NOT send a previously sent Client Cookie to
that server, unless it can track Client IP Address changes for that server, unless it can track Client IP Address changes for
those servers too. those servers too.
Besides the Client Cookie construction, this update on [RFC7873] does Besides the Client Cookie construction, this update on [RFC7873] does
not introduce any new characteristics to DNS Cookies operations and not introduce any new characteristics to DNS Cookies operations and
the Security Considerations section of [RFC7873] still applies. the Security Considerations section of [RFC7873] still applies.
9. References 9. Acknowledgements
9.1. Normative References Thanks to Witold Krecicki and Pieter Lexis for valuable input,
suggestions and text and above all for implementing a prototype of an
interoperable DNS Cookie in Bind9, Knot and PowerDNS during the
hackathon of IETF104 in Prague. Thanks for valuable input and
suggestions go to Ralph Dolmans, Bob Harold, Daniel Salzman, Martin
Hoffmann, Mukund Sivaraman, Petr Spacek, Loganaden Velvindron, Bob
Harold, Philip Homburg, Tim Wicinski and Brian Dickson.
10. Normative References
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
DOI 10.17487/RFC1982, August 1996, DOI 10.17487/RFC1982, August 1996,
<https://www.rfc-editor.org/info/rfc1982>. <https://www.rfc-editor.org/info/rfc1982>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS) [RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)
Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016, Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,
<https://www.rfc-editor.org/info/rfc7873>. <https://www.rfc-editor.org/info/rfc7873>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SipHash-2.4] [SipHash-2.4]
Aumasson, J. and D. Bernstein, "SipHash: a fast short- Aumasson, J. and D. J. Bernstein, "SipHash: a fast short-
input PRF", 2012, <https://131002.net/siphash/>. input PRF", 2012, <https://131002.net/siphash/>.
9.2. Informative References 11. Informative References
[FNV] Fowler, G., Noll, L., Vo, K., Eastlake, D., and T. Hansen, [FNV] Fowler, G., Noll, L., Vo, K., Eastlake, D., and T. Hansen,
"The FNV Non-Cryptographic Hash Algorithm", "The FNV Non-Cryptographic Hash Algorithm",
<https://datatracker.ietf.org/doc/draft-eastlake-fnv>. <https://datatracker.ietf.org/doc/draft-eastlake-fnv>.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
<https://www.rfc-editor.org/info/rfc4941>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, (SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011, DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>. <https://www.rfc-editor.org/info/rfc6234>.
Appendix A. Acknowledgements Appendix A. Test vectors
Thanks to Witold Krecicki and Pieter Lexis for valuable input,
suggestions and text and above all for implementing a prototype of an
interoperable DNS Cookie in Bind9, Knot and PowerDNS during the
hackathon of IETF104 in Prague. Thanks for valuable input and
suggestions go to Ralph Dolmans, Bob Harold, Daniel Salzman, Martin
Hoffmann, Mukund Sivaraman, Petr Spacek, Loganaden Velvindron, Bob
Harold and Philip Homburg
Appendix B. Test vectors
B.1. Learning a new Server Cookie A.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"
like format. The content of the DNS COOKIE Option is shown in like format. The content of the DNS COOKIE Option is shown in
hexadecimal format after "; COOKIE:". hexadecimal format after "; COOKIE:".
;; Sending: ;; Sending:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57406 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57406
;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 2464c4abcf10c957 ; COOKIE: 2464c4abcf10c957
;; QUESTION SECTION: ;; QUESTION SECTION:
;example.com. IN A ;example.com. IN A
;; QUERY SIZE: 52 ;; QUERY SIZE: 52
The authoritative nameserver (server) is configured with the The authoritative nameserver (server) is configured with the
following secret: e5e973e5a6b2a43f48e7dc849e37bfcf (as hex data). following secret: e5e973e5a6b2a43f48e7dc849e37bfcf (as hex data).
It receives the query at Wed Jun 5 10:53:05 UTC 2019. It receives the query at Wed Jun 5 10:53:05 UTC 2019.
The content of the DNS COOKIE Option that the server will return is The content of the DNS COOKIE Option that the server will return is
shown below in hexadecimal format after "; COOKIE:" shown below in hexadecimal format after "; COOKIE:"
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57406
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; Got answer:
; EDNS: version: 0, flags:; udp: 4096 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57406
; COOKIE: 2464c4abcf10c957010000005cf79f111f8130c3eee29480 (good) ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; QUESTION SECTION:
;example.com. IN A
;; ANSWER SECTION: ;; OPT PSEUDOSECTION:
example.com. 86400 IN A 192.0.2.34 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 2464c4abcf10c957010000005cf79f111f8130c3eee29480 (good)
;; QUESTION SECTION:
;example.com. IN A
;; Query time: 6 msec ;; ANSWER SECTION:
;; SERVER: 192.0.2.53#53(192.0.2.53) example.com. 86400 IN A 192.0.2.34
;; WHEN: Wed Jun 5 10:53:05 UTC 2019
;; MSD SIZE rcvd: 84
B.2. The same client learning a renewed (fresh) Server Cookie ;; Query time: 6 msec
;; SERVER: 192.0.2.53#53(192.0.2.53)
;; WHEN: Wed Jun 5 10:53:05 UTC 2019
;; MSD SIZE rcvd: 84
A.2. The same client learning a renewed (fresh) Server Cookie
40 minutes later, the same resolver (client) queries the same server 40 minutes later, the same resolver (client) queries the same server
for for "example.org" : for for "example.org" :
;; Sending: ;; Sending:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50939 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50939
;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 2464c4abcf10c957010000005cf79f111f8130c3eee29480 ; COOKIE: 2464c4abcf10c957010000005cf79f111f8130c3eee29480
;; QUESTION SECTION: ;; QUESTION SECTION:
;example.org. IN A ;example.org. IN A
;; QUERY SIZE: 52 ;; QUERY SIZE: 52
The authoritative nameserver (server) now generates a new Server The authoritative nameserver (server) now generates a new Server
Cookie. The server SHOULD do this because it can see the Server Cookie. The server SHOULD do this because it can see the Server
Cookie send by the client is older than half an hour Section 4.3, but Cookie send by the client is older than half an hour Section 4.3, but
it is also fine for a server to generate a new Server Cookie sooner, it is also fine for a server to generate a new Server Cookie sooner,
or even for every answer. or even for every answer.
;; Got answer: ;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50939 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50939
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 2464c4abcf10c957010000005cf7a871d4a564a1442aca77 (good) ; COOKIE: 2464c4abcf10c957010000005cf7a871d4a564a1442aca77 (good)
;; QUESTION SECTION: ;; QUESTION SECTION:
;example.org. IN A ;example.org. IN A
;; ANSWER SECTION: ;; ANSWER SECTION:
example.org. 86400 IN A 192.0.2.34 example.org. 86400 IN A 192.0.2.34
;; Query time: 6 msec ;; Query time: 6 msec
;; SERVER: 192.0.2.53#53(192.0.2.53) ;; SERVER: 192.0.2.53#53(192.0.2.53)
;; WHEN: Wed Jun 5 11:33:05 UTC 2019 ;; WHEN: Wed Jun 5 11:33:05 UTC 2019
;; MSD SIZE rcvd: 84 ;; MSD SIZE rcvd: 84
B.3. Another client learning a renewed Server Cookie A.3. Another client learning a renewed Server Cookie
Another resolver (client) with IPv4 address 203.0.113.203 sends a Another resolver (client) with IPv4 address 203.0.113.203 sends a
request to the same server with a valid Server Cookie that it learned request to the same server with a valid Server Cookie that it learned
before (at Wed Jun 5 09:46:25 UTC 2019). Note that the Server Cookie before (at Wed Jun 5 09:46:25 UTC 2019). Note that the Server Cookie
has Reserved bytes set, but is still valid with the configured has Reserved bytes set, but is still valid with the configured
secret; the Hash part is calculated taking along the Reserved bytes. secret; the Hash part is calculated taking along the Reserved bytes.
;; Sending: ;; Sending:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34736 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34736
;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: fc93fc62807ddb8601abcdef5cf78f71a314227b6679ebf5 ; COOKIE: fc93fc62807ddb8601abcdef5cf78f71a314227b6679ebf5
;; QUESTION SECTION: ;; QUESTION SECTION:
;example.com. IN A ;example.com. IN A
;; QUERY SIZE: 52 ;; QUERY SIZE: 52
The authoritative nameserver (server) replies with a freshly The authoritative nameserver (server) replies with a freshly
generated Server Cookie for this client conformant with this generated Server Cookie for this client conformant with this
specification; so with the Reserved bits set to zero. specification; so with the Reserved bits set to zero.
;; Got answer: ;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34736 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34736
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: fc93fc62807ddb86010000005cf7a9acf73a7810aca2381e (good) ; COOKIE: fc93fc62807ddb86010000005cf7a9acf73a7810aca2381e (good)
;; QUESTION SECTION: ;; QUESTION SECTION:
;example.com. IN A ;example.com. IN A
;; ANSWER SECTION: ;; ANSWER SECTION:
example.com. 86400 IN A 192.0.2.34 example.com. 86400 IN A 192.0.2.34
;; Query time: 6 msec ;; Query time: 6 msec
;; SERVER: 192.0.2.53#53(192.0.2.53) ;; SERVER: 192.0.2.53#53(192.0.2.53)
;; WHEN: Wed Jun 5 11:38:20 UTC 2019 ;; WHEN: Wed Jun 5 11:38:20 UTC 2019
;; MSD SIZE rcvd: 84 ;; MSD SIZE rcvd: 84
B.4. IPv6 query with rolled over secret A.4. IPv6 query with rolled over secret
The query below is from a client with IPv6 address The query below is from a client with IPv6 address
2001:db8:220:1:59de:d0f4:8769:82b8 to a server with IPv6 address 2001:db8:220:1:59de:d0f4:8769:82b8 to a server with IPv6 address
2001:db8:8f::53. The client has learned a valid Server Cookie before 2001:db8:8f::53. The client has learned a valid Server Cookie before
when the Server had secret: dd3bdf9344b678b185a6f5cb60fca715. The when the Server had the secret: dd3bdf9344b678b185a6f5cb60fca715.
server now uses a new secret, but it can still validate the Server The server now uses a new secret, but it can still validate the
Cookie provided by the client as the old secret has not expired yet. Server Cookie provided by the client as the old secret has not
expired yet.
;; Sending: ;; Sending:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6774 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6774
;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; flags:; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 22681ab97d52c298010000005cf7c57926556bd0934c72f8 ; COOKIE: 22681ab97d52c298010000005cf7c57926556bd0934c72f8
;; QUESTION SECTION: ;; QUESTION SECTION:
;example.net. IN A ;example.net. IN A
;; QUERY SIZE: 52 ;; QUERY SIZE: 52
The authoritative nameserver (server) replies with a freshly The authoritative nameserver (server) replies with a freshly
generated server cookie for this client with its new secret: generated server cookie for this client with its new secret:
445536bcd2513298075a5d379663c962 445536bcd2513298075a5d379663c962
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6774
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION: ;; Got answer:
; EDNS: version: 0, flags:; udp: 4096 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6774
; COOKIE: 22681ab97d52c298010000005cf7c609a6bb79d16625507a (good) ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; QUESTION SECTION:
;example.net. IN A
;; ANSWER SECTION: ;; OPT PSEUDOSECTION:
example.net. 86400 IN A 192.0.2.34 ; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 22681ab97d52c298010000005cf7c609a6bb79d16625507a (good)
;; QUESTION SECTION:
;example.net. IN A
;; Query time: 6 msec ;; ANSWER SECTION:
;; SERVER: 2001:db8:8f::53#53(2001:db8:8f::53) example.net. 86400 IN A 192.0.2.34
;; WHEN: Wed Jun 5 13:36:57 UTC 2019
;; MSD SIZE rcvd: 84
Appendix C. Implementation status ;; Query time: 6 msec
;; SERVER: 2001:db8:8f::53#53(2001:db8:8f::53)
;; WHEN: Wed Jun 5 13:36:57 UTC 2019
;; MSD SIZE rcvd: 84
Appendix B. Implementation status
At the time of writing, BIND from version 9.16 and Knot DNS from At the time of writing, BIND from version 9.16 and Knot DNS from
version 2.9.0 create Server Cookies according to the recipe described version 2.9.0 create Server Cookies according to the recipe described
in this draft. Unbound and NSD have an Proof of Concept in this draft. Unbound and NSD have an Proof of Concept
implementation that has been tested for interoperability during the implementation that has been tested for interoperability during the
hackathon at the IETF104 in Prague. Construction of privacy hackathon at the IETF104 in Prague. Construction of privacy
maintaining Client Cookies according to the directions in this draft maintaining Client Cookies according to the directions in this draft
have been implemented in the getdns library and will be in the have been implemented in the getdns library and will be in the
upcoming getdns-1.6.1 release and in Stubby version 0.3.1. upcoming getdns-1.6.1 release and in Stubby version 0.3.1.
skipping to change at page 15, line 34 skipping to change at page 16, line 4
At the time of writing, BIND from version 9.16 and Knot DNS from At the time of writing, BIND from version 9.16 and Knot DNS from
version 2.9.0 create Server Cookies according to the recipe described version 2.9.0 create Server Cookies according to the recipe described
in this draft. Unbound and NSD have an Proof of Concept in this draft. Unbound and NSD have an Proof of Concept
implementation that has been tested for interoperability during the implementation that has been tested for interoperability during the
hackathon at the IETF104 in Prague. Construction of privacy hackathon at the IETF104 in Prague. Construction of privacy
maintaining Client Cookies according to the directions in this draft maintaining Client Cookies according to the directions in this draft
have been implemented in the getdns library and will be in the have been implemented in the getdns library and will be in the
upcoming getdns-1.6.1 release and in Stubby version 0.3.1. upcoming getdns-1.6.1 release and in Stubby version 0.3.1.
Authors' Addresses Authors' Addresses
Ondrej Sury Ondrej Sury
Internet Systems Consortium Internet Systems Consortium
CZ Czechia
Email: ondrej@isc.org Email: ondrej@isc.org
Willem Toorop Willem Toorop
NLnet Labs NLnet Labs
Science Park 400 Science Park 400
Amsterdam 1098 XH 1098 XH Amsterdam
Netherlands Netherlands
Email: willem@nlnetlabs.nl Email: willem@nlnetlabs.nl
Donald E. Eastlake 3rd Donald E. Eastlake 3rd
Futurewei Technologies Futurewei Technologies
1424 Pro Shop Court 1424 Pro Shop Court
Davenport FL 33896 Davenport, FL 33896
USA United States of America
Phone: +1-508-333-2270 Phone: +1-508-333-2270
Email: d3e3e3@gmail.com Email: d3e3e3@gmail.com
Mark Andrews Mark Andrews
Internet Systems Consortium Internet Systems Consortium
950 Charter Street 950 Charter Street
Redwood City CA 94063 Redwood City, CA 94063
USA United States of America
Email: marka@isc.org Email: marka@isc.org
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