draft-ietf-dnsext-dnssec-algo-signal-10.txt   rfc6975.txt 
DNS Extensions Working Group S. Crocker Internet Engineering Task Force (IETF) S. Crocker
Internet-Draft Shinkuro Inc. Request for Comments: 6975 Shinkuro Inc.
Intended status: Standards Track S. Rose Category: Standards Track S. Rose
Expires: October 10, 2013 NIST ISSN: 2070-1721 NIST
April 08, 2013 July 2013
Signaling Cryptographic Algorithm Understanding in DNSSEC Signaling Cryptographic Algorithm Understanding in
draft-ietf-dnsext-dnssec-algo-signal-10 DNS Security Extensions (DNSSEC)
Abstract Abstract
The DNS Security Extensions (DNSSEC) were developed to provide origin The DNS Security Extensions (DNSSEC) were developed to provide origin
authentication and integrity protection for DNS data by using digital authentication and integrity protection for DNS data by using digital
signatures. These digital signatures can be generated using signatures. These digital signatures can be generated using
different algorithms. This draft sets out to specify a way for different algorithms. This document specifies a way for validating
validating end-system resolvers to signal to a server which digital end-system resolvers to signal to a server which digital signature
signature and hash algorithms they support. The proposed extensions and hash algorithms they support. The extensions allow the signaling
allow the signaling of new algorithm uptake in client code to allow of new algorithm uptake in client code to allow zone administrators
zone administrators to know when it is possible to complete an to know when it is possible to complete an algorithm rollover in a
algorithm rollover in a DNSSEC signed zone. DNSSEC-signed zone.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on October 10, 2013. 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/rfc6975.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
skipping to change at page 2, line 19 skipping to change at page 2, line 22
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash 2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 4
Understood (DHU) and NSEC3 Hash Understood (N3U) Using EDNS . 3 3. Signaling DNSSEC Algorithm Understood (DAU), DS Hash
3. Client Considerations . . . . . . . . . . . . . . . . . . . . 4 Understood (DHU), and NSEC3 Hash Understood (N3U) Using EDNS . 4
3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . 5 4. Client Considerations . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Validating Stub Resolvers . . . . . . . . . . . . . . 5 4.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . . 5
3.1.2. Non-Validating Stub Resolvers . . . . . . . . . . . . 5 4.1.1. Validating Stub Resolvers . . . . . . . . . . . . . . . 5
3.2. Recursive Resolvers . . . . . . . . . . . . . . . . . . . 5 4.1.2. Non-validating Stub Resolvers . . . . . . . . . . . . . 6
3.2.1. Validating Recursive Resolvers . . . . . . . . . . . 5 4.2. Recursive Resolvers . . . . . . . . . . . . . . . . . . . . 6
3.2.2. Non-validating Recursive Resolvers . . . . . . . . . 6 4.2.1. Validating Recursive Resolvers . . . . . . . . . . . . 6
4. Intermediate System Considerations . . . . . . . . . . . . . 6 4.2.2. Non-validating Recursive Resolvers . . . . . . . . . . 6
5. Server Considerations . . . . . . . . . . . . . . . . . . . . 6 5. Intermediate System Considerations . . . . . . . . . . . . . . 6
6. Traffic Analysis Considerations . . . . . . . . . . . . . . . 6 6. Server Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Traffic Analysis Considerations . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8 9. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 10. Normative References . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The DNS Security Extensions (DNSSEC) [RFC4033], [RFC4034] and The DNS Security Extensions (DNSSEC), [RFC4033], [RFC4034], and
[RFC4035] were developed to provide origin authentication and [RFC4035], were developed to provide origin authentication and
integrity protection for DNS data by using digital signatures. Each integrity protection for DNS data by using digital signatures. Each
digital signature RR (RRSIG) contains an algorithm code number. digital signature (RRSIG) Resource Record (RR) contains an algorithm
code number that corresponds to a DNSSEC public key (DNSKEY) RR.
These algorithm codes tell validators which cryptographic algorithm These algorithm codes tell validators which cryptographic algorithm
was used to generate the digital signature. was used to generate the digital signature.
Likewise, Delegation Signer (DS) RRs and NSEC3 RRs use a hashed value Likewise, the Delegation Signer (DS) RRs and Hashed Authenticated
as part of their RDATA and, like digital signature algorithms, these Denial of Existence (NSEC3) RRs use a hashed value as part of their
hash algorithms have code numbers. All three algorithm codes (RRSIG/ resource record data (RDATA) and, like digital signature algorithms,
DNSKEY, DS and NSEC3) are maintained in unique IANA registries. these hash algorithms have code numbers. All three algorithm codes
(RRSIG/DNSKEY, DS, and NSEC3) are maintained in unique IANA
registries.
This draft sets out to specify a way for validating end-system This document sets specifies a way for validating end-system
resolvers to tell a server in a DNS query which digital signature and resolvers to tell a server in a DNS query which digital signature
/or hash algorithms they support. This is done using the new EDNS and/or hash algorithms they support. This is done using the new
options specified below in Section 2 for use in the OPT meta-RR Extension Mechanisms for DNS (EDNS0) options specified below in
[I-D.ietf-dnsext-rfc2671bis-edns0]. These three new EDNS option Section 2 for use in the OPT meta-RR [RFC6891]. These three new
codes are all OPTIONAL to implement and use. EDNS0 option codes are all OPTIONAL to implement and use.
These proposed EDNS options serve to measure the acceptance and use These proposed EDNS0 options serve to measure the acceptance and use
of new digital signing algorithms. These signaling options can be of new digital signing algorithms. These signaling options can be
used by zone administrators as a gauge to measure the successful used by zone administrators as a gauge to measure the successful
deployment of code that implements newly deployed digital signature deployment of code that implements the newly deployed digital
algorithm, DS hash and NSEC3 hash algorithm used with DNSSEC. A zone signature algorithm, DS hash, and the NSEC3 hash algorithm used with
administrator is able to determine when to stop signing with a DNSSEC. A zone administrator is able to determine when to stop
superseded algorithm when the server sees that a significant number signing with a superseded algorithm when the server sees that a
of its clients signal that they are able to accept the new algorithm. significant number of its clients signal that they are able to accept
Note that this survey may be conducted over the period of years the new algorithm. Note that this survey may be conducted over a
before a tipping point is seen. period of years before a tipping point is seen.
This draft does not seek to introduce another process for including This document does not seek to introduce another process for
new algorithms for use with DNSSEC. It also does not address the including new algorithms for use with DNSSEC. It also does not
question of which algorithms are to be included in any official list address the question of which algorithms are to be included in any
of mandatory or recommended cryptographic algorithms for use with official list of mandatory or recommended cryptographic algorithms
DNSSEC. Rather, this document specifies a means by which a client for use with DNSSEC. Rather, this document specifies a means by
query can signal the set of algorithms and hashes which it which a client query can signal the set of algorithms and hashes that
implements. it implements.
2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood 2. Requirements Language
(DHU) and NSEC3 Hash Understood (N3U) Using EDNS
The EDNS0 specification outlined in The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
[I-D.ietf-dnsext-rfc2671bis-edns0] defines a way to include new "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
options using a standardized mechanism. These options are contained "OPTIONAL" in this document are to be interpreted as described in RFC
in the RDATA of the OPT meta-RR. This document defines three new 2119 [RFC2119].
EDNS options for a client to signal which digital signature and/or
hash algorithms the client supports. These options can be used 3. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood
independently of each other and MAY appear in any order in the OPT (DHU), and NSEC3 Hash Understood (N3U) Using EDNS
RR. Each option code can appear only once in an OPT RR.
The EDNS0 specification outlined in [RFC6891] defines a way to
include new options using a standardized mechanism. These options
are contained in the RDATA of the OPT meta-RR. This document defines
three new EDNS0 options for a client to signal which digital
signature and/or hash algorithms the client supports. These options
can be used independently of each other and MAY appear in any order
in the OPT RR. Each option code can appear only once in an OPT RR.
The figure below shows how each option is defined in the RDATA of the The figure below shows how each option is defined in the RDATA of the
OPT RR specified in [I-D.ietf-dnsext-rfc2671bis-edns0]: OPT RR specified in [RFC6891]:
0 8 16 0 8 16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-CODE (TBD) | | OPTION-CODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| LIST-LENGTH | | LIST-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ALG-CODE | ... \ | ALG-CODE | ... /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
OPTION-CODE is the code for the given signaling option. They are: OPTION-CODE is the code for the given signaling option. The options
are:
o DNSSEC Algorithm Understood (DAU) option for DNSSEC digital o DNSSEC Algorithm Understood (DAU) option for DNSSEC digital
signing algorithms. Its value is fixed at TBD1. signing algorithms. Its value is fixed at 5.
o DS Hash Understood (DHU) option for DS RR hash algorithms. Its o DS Hash Understood (DHU) option for DS RR hash algorithms. Its
value is fixed at TBD2. value is fixed at 6.
o NSEC3 Hash Understood (N3U) option for NSEC3 hash algorithms. Its o NSEC3 Hash Understood (N3U) option for NSEC3 hash algorithms. Its
value is fixed at TBD3. value is fixed at 7.
LIST-LENGTH is the length of the list of digital signature or hash LIST-LENGTH is the length of the list of digital signatures or hash
algorithm codes in octets. Each algorithm code occupies a single algorithm codes in octets. Each algorithm code occupies a single
octet. octet.
ALG-CODE is the list of assigned values of DNSSEC zone signing ALG-CODE is the list of assigned values of DNSSEC zone signing
algorithms, DS hash algorithms, or NSEC3 hash algorithms (depending algorithms, DS hash algorithms, or NSEC3 hash algorithms (depending
on the OPTION-CODE in use) that the client declares to be supported. on the OPTION-CODE in use) that the client declares to be supported.
The order of the code values can be arbitrary and MUST NOT be used to The order of the code values can be arbitrary and MUST NOT be used to
infer preference. infer preference.
If all three options are included in the OPT RR, there is a potential If all three options are included in the OPT RR, there is a potential
for the OPT RR to take up considerable size in the DNS message. for the OPT RR to take up considerable size in the DNS message.
However, in practical terms, including all three options is likely to However, in practical terms, including all three options is likely to
take up 22-32 octets (average of 6-10 digital signature algorithms, take up 22-32 octets (average of 6-10 digital signature algorithms,
3-5 DS hash algorithms and 1-5 NSEC3 hash algorithms) including the 3-5 DS hash algorithms, and 1-5 NSEC3 hash algorithms) including the
EDNS option codes and option lengths in potential future examples. EDNS0 option codes and option lengths in potential future examples.
3. Client Considerations 4. Client Considerations
A validating end-system resolver sets the DAU, DHU and/or N3U option, A validating end-system resolver sets the DAU, DHU, and/or N3U
or combination thereof in the OPT meta-RR when sending a query. The option, or combination thereof, in the OPT meta-RR when sending a
validating end-system resolver MUST also set the DNSSEC-OK bit query. The validating end-system resolver MUST also set the DNSSEC
[RFC4035] to indicate that it wishes to receive DNSSEC RRs in the OK bit [RFC4035] to indicate that it wishes to receive DNSSEC RRs in
response. the response.
Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) digital Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) digital
signature codes both cover a potentially wide range of algorithms and signature codes both cover a potentially wide range of algorithms and
are likely not useful to a server. There is no compelling reason for are likely not useful to a server. There is no compelling reason for
a client to include these codes in its list of the DAU. Likewise, a client to include these codes in its list of the DAU. Likewise,
clients MUST NOT include RESERVED codes in any of the options. clients MUST NOT include RESERVED codes in any of the options.
Likewise, a client is under no obligation to list every algorithm it Additionally, a client is under no obligation to list every algorithm
implements and MAY choose to only list algorithms the client wishes it implements and MAY choose to only list algorithms the client
to signal as understood. wishes to signal as understood.
Since the DAU, DHU and/or N3U options are only set in the query, if a Since the DAU, DHU, and/or N3U options are only set in the query, if
client sees these options in the response, no action needs to be a client sees these options in the response, no action needs to be
taken and the client MUST ignore the option values. taken and the client MUST ignore the option values.
3.1. Stub Resolvers 4.1. Stub Resolvers
Typically, stub resolvers rely on an upstream recursive server (or Typically, stub resolvers rely on an upstream recursive server (or
cache) to provide a response. So optimal setting of the DAU, DSU and cache) to provide a response. So optimal setting of the DAU, DSU,
N3U options depends on whether the stub resolver elects to perform and N3U options depends on whether the stub resolver elects to
its own validation. perform its own validation.
3.1.1. Validating Stub Resolvers 4.1.1. Validating Stub Resolvers
A validating stub resolver already (usually) sets the DO bit A validating stub resolver sets the DNSSEC OK (DO) bit [RFC4035] to
[RFC4035] to indicate that it wishes to receive additional DNSSEC RRs indicate that it wishes to receive additional DNSSEC RRs (i.e., RRSIG
(i.e. RRSIG RRs) in the response. Such validating resolvers SHOULD RRs) in the response. Such validating resolvers SHOULD include the
include the DAU, DHU and/or the N3U option(s) in the OPT RR when DAU, DHU, and/or the N3U option(s) in the OPT RR when sending a
sending a query. query.
3.1.2. Non-Validating Stub Resolvers 4.1.2. Non-validating Stub Resolvers
The DAU, DHU and N3U EDNS options MUST NOT be included by non- The DAU, DHU, and N3U EDNS0 options MUST NOT be included by
validating stub resolvers. non-validating stub resolvers.
3.2. Recursive Resolvers 4.2. Recursive Resolvers
3.2.1. Validating Recursive Resolvers 4.2.1. Validating Recursive Resolvers
A validating recursive resolver sets the DAU, DHU and/or N3U A validating recursive resolver sets the DAU, DHU, and/or N3U
option(s) when performing recursion based on its list of algorithms option(s) when performing recursion based on its list of algorithms
and any DAU, DHU and/or N3U option lists in the stub client query. and any DAU, DHU, and/or N3U option lists in the stub client query.
When the recursive server receives a query with one or more of the When the recursive server receives a query with one or more of the
options set, the recursive server MUST set the algorithm list for any options set, the recursive server MUST set the algorithm list for any
outgoing iterative queries for that resolution chain to a union of outgoing iterative queries for that resolution chain to a union of
the stub client's list and the validating recursive resolver's list. the stub client's list and the validating recursive resolver's list.
For example, if the recursive resolver's algorithm list for the DAU For example, if the recursive resolver's algorithm list for the DAU
option is (3, 5, 7) and the stub's algorithm list is (7, 8), the option is (3, 5, 7) and the stub's algorithm list is (7, 8), the
final DAU algorithm list would be (3, 5, 7, 8). final DAU algorithm list would be (3, 5, 7, 8).
If the client did include the DO and CD bits, but did not include the If the client included the DO and Checking Disabled (CD) bits, but
DAU, DHU and/or N3U option(s) in the query, the validating recursive did not include the DAU, DHU, and/or N3U option(s) in the query, the
resolver MAY include the option(s) with its own list in full. If one validating recursive resolver MAY include the option(s) with its own
or more of the options are missing, the validating recursive resolver list in full. If one or more of the options are missing, the
MAY include the missing options with its own list in full. validating recursive resolver MAY include the missing options with
its own list in full.
Validating recursive resolvers MUST NOT set the DAU, DHU and/or N3U Validating recursive resolvers MUST NOT set the DAU, DHU, and/or N3U
option(s) in the final response to the stub client. option(s) in the final response to the stub client.
3.2.2. Non-validating Recursive Resolvers 4.2.2. Non-validating Recursive Resolvers
Recursive resolvers that do not do validation MUST copy the DAU, DHU Recursive resolvers that do not do validation MUST copy the DAU, DHU,
and/or N3U option(s) seen in received queries as they represent the and/or N3U option(s) seen in received queries as they represent the
wishes of the validating downstream resolver that issued the original wishes of the validating downstream resolver that issued the original
query. query.
4. Intermediate System Considerations 5. Intermediate System Considerations
Intermediate proxies [RFC5625] (Section 4.4.2) that understand DNS Intermediate proxies (see Section 4.4.2 of [RFC5625]) that understand
are RECOMMENDED to behave like a comparable recursive resolver when DNS are RECOMMENDED to behave like a comparable recursive resolver
dealing with the DAU, DHU and N3U options. when dealing with the DAU, DHU, and N3U options.
5. Server Considerations 6. Server Considerations
When an authoritative server sees the DAU, DHU and/or N3U option(s) When an authoritative server sees the DAU, DHU, and/or N3U option(s)
in the OPT meta-RR in a request the normal algorithm for servicing in the OPT meta-RR in a request, the normal algorithm for servicing
requests is followed. The options MUST NOT trigger any special requests is followed. The options MUST NOT trigger any special
processing (e.g. RRSIG filtering in responses) on the server side. processing (e.g., RRSIG filtering in responses) on the server side.
If the options are present but the DNSSEC-OK (OK) bit is not set, the If the options are present but the DO bit is not set, the server does
server does not do any DNSSEC processing, including any recording of not do any DNSSEC processing, which includes any recording of the
the option(s). option(s).
If the server sees one (or more) of the options set with RESERVED If the server sees one (or more) of the options set with RESERVED
values, the server MAY ignore recoding of those values. values, the server MAY ignore recoding of those values.
Authoritative servers MUST NOT set the DAU, DHU and/or N3U option(s) Authoritative servers MUST NOT set the DAU, DHU, and/or N3U option(s)
on any responses. These values are only set in queries. on any responses. These values are only set in queries.
6. Traffic Analysis Considerations 7. Traffic Analysis Considerations
Zone administrators that are planning or are in the process of a Zone administrators that are planning or are in the process of a
cryptographic algorithm rollover operation should monitor DNS query cryptographic algorithm rollover operation should monitor DNS query
traffic and record the number of queries, the presence of the OPT RR traffic and record the number of queries, the presence of the OPT RR
in queries and the values of the DAU/DHU/N3U option(s) (if present). in queries, and the values of the DAU/DHU/N3U option(s) (if present).
This monitoring can be used to measure the deployment of client code This monitoring can be used to measure the deployment of client code
that implements (and signals) specific algorithms. Description of that implements (and signals) specific algorithms. A description of
the techniques used to capture DNS traffic and measure new algorithm the techniques used to capture DNS traffic and measure new algorithm
adoption is beyond the scope of this document. adoption is beyond the scope of this document.
Zone administrators that need to comply with changes to their Zone administrators that need to comply with changes to their
organization's security policy (with regards to cryptographic organization's security policy (with regards to cryptographic
algorithm use) can use this data to set milestone dates for algorithm use) can use this data to set milestone dates for
performing an algorithm rollover. For example, zone administrators performing an algorithm rollover. For example, zone administrators
can use the data to determine when older algorithms can be phased out can use the data to determine when older algorithms can be phased out
without disrupting a significant number of clients. In order to keep without disrupting a significant number of clients. In order to keep
this disruption to a minimum, zone administrators should wait to this disruption to a minimum, zone administrators should wait to
complete an algorithm rollover until a large majority of clients complete an algorithm rollover until a large majority of clients
signal that they recognize the new algorithm. This may be in the signal that they recognize the new algorithm. This may be in the
order of years rather than months. order of years rather than months.
Note that clients that do not implement these options are likely to Note that clients that do not implement these options are likely to
be older implementations which would also not implement any newly be older implementations that would also not implement any newly
deployed algorithm. deployed algorithm.
7. IANA Considerations 8. IANA Considerations
The algorithm codes used to identify DNSSEC algorithms, DS RR hash The algorithm codes used to identify DNSSEC algorithms, DS RR hash
algorithms and NSEC3 hash algorithms have already been established by algorithms, and NSEC3 hash algorithms have already been established
IANA. This document does not seek to alter that registry in any way. by IANA. This document does not seek to alter that registry in any
way.
This draft seeks to update the "DNS EDNS Options" registry by adding IANA has allocated option codes 5, 6, and 7 for the DAU, DHU, and N3U
the DAU, DHU and N3U options and referencing this document. The code options, respectively, in the "DNS EDNS0 Option Codes (OPT)"
for these options are TBD1, TBD2 and TBD3 respectively. registry. The three options have a status of "standard".
8. Security Considerations 9. Security Considerations
This document specifies a way for a client to signal its digital This document specifies a way for a client to signal its digital
signature and hash algorithm knowledge to a cache or server. It is signature and hash algorithm knowledge to a cache or server. It is
not meant to be a discussion on algorithm superiority. The signals not meant to be a discussion on algorithm superiority. The signals
are optional codes contained in the OPT meta-RR used with EDNS. The are optional codes contained in the OPT meta-RR used with EDNS. The
goal of these options are to signal new algorithm uptake in client goal of these options is to signal new algorithm uptake in client
code to allow zone administrators to know when it is possible to code to allow zone administrators to know when it is possible to
complete an algorithm rollover in a DNSSEC signed zone. complete an algorithm rollover in a DNSSEC-signed zone.
There is a possibility that an eavesdropper or server could infer the There is a possibility that an eavesdropper or server could infer the
validator in use by a client by the presence of the AU options and/or validator in use by a client by the presence of the AU options and/or
algorithm code list. This information leakage in itself is not very algorithm code list. This information leakage in itself is not very
useful to a potential attacker but it could be used to identify the useful to a potential attacker, but it could be used to identify the
validator or narrow down the possible validator implementations in validator or narrow down the possible validator implementations in
use by a client, which could have a known vulnerability that could be use by a client, which could have a known vulnerability that could be
exploited by the attacker. exploited by the attacker.
9. Normative References 10. Normative References
[I-D.ietf-dnsext-rfc2671bis-edns0]
Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", draft-ietf-dnsext-rfc2671bis-edns0-10
(work in progress), December 2012.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC Rose, "DNS Security Introduction and Requirements",
4033, March 2005. RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005. RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005. Extensions", RFC 4035, March 2005.
[RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", BCP [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines",
152, RFC 5625, August 2009. BCP 152, RFC 5625, August 2009.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, April 2013.
Authors' Addresses Authors' Addresses
Steve Crocker Steve Crocker
Shinkuro Inc. Shinkuro Inc.
5110 Edgemoor Lane 5110 Edgemoor Lane
Bethesda, MD 20814 Bethesda, MD 20814
USA USA
EMail: steve@shinkuro.com EMail: steve@shinkuro.com
 End of changes. 65 change blocks. 
169 lines changed or deleted 171 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/