draft-ietf-dnsext-dnssec-algo-signal-06.txt   draft-ietf-dnsext-dnssec-algo-signal-07.txt 
DNS Extensions Working Group S. Crocker DNS Extensions Working Group S. Crocker
Internet-Draft Shinkuro Inc. Internet-Draft Shinkuro Inc.
Intended status: Standards Track S. Rose Intended status: Standards Track S. Rose
Expires: November 2, 2012 NIST Expires: December 16, 2012 NIST
May 1, 2012 June 14, 2012
Signaling Cryptographic Algorithm Understanding in DNSSEC Signaling Cryptographic Algorithm Understanding in DNSSEC
draft-ietf-dnsext-dnssec-algo-signal-06 draft-ietf-dnsext-dnssec-algo-signal-07
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 draft sets out to specify a way for
validating end-system resolvers to signal to a server which validating end-system resolvers to signal to a server which digital
cryptographic algorithms and hash algorithms they support. signature and hash algorithms they support.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [RFC2119]. "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 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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 2, 2012. This Internet-Draft will expire on December 16, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 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
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8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . . 7 9. Normative References . . . . . . . . . . . . . . . . . . . . . 7
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 RR (RRSIG) contains an algorithm code number.
These algorithm codes tells 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) RR's and NSEC3 RR's use a hashed Likewise, Delegation Signer (DS) RRs and NSEC3 RRs use a hashed value
value as part of their RDATA and, like digital signature algorithms, as part of their RDATA and, like digital signature algorithms, these
these hash algorithms have code numbers. All three algorithm codes hash algorithms have code numbers. All three algorithm codes (RRSIG/
(RRSIG/DNSKEY, DS and NSEC3) are maintained in unique IANA DNSKEY, DS and NSEC3) are maintained in unique IANA registries.
registries.
This draft sets out to specify a way for validating end-system This draft sets out to specify a way for validating end-system
resolvers to tell a server in a DNS query which digital signature resolvers to tell a server in a DNS query which digital signature
and/or hash algorithms they support. This is done using the new EDNS and/or hash algorithms they support. This is done using the new EDNS
options specified below in Section 2 for use in the OPT meta-RR options specified below in Section 2 for use in the OPT meta-RR
[I-D.ietf-dnsext-rfc2671bis-edns0]. [I-D.ietf-dnsext-rfc2671bis-edns0].
These proposed EDNS options serve to measure the acceptance and use These proposed EDNS 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 a newly deployed digital signature deployment of code that implements newly deployed digital signature
algorithm, DS hash and NSEC3 hash algorithm used with DNSSEC. A zone algorithm, DS hash and NSEC3 hash algorithm used with DNSSEC. A zone
administrator may be able to determine when to stop signing with a administrator is able to determine when to stop signing with a
superseded algorithm when the server sees that a significant number superseded algorithm when the server sees that a significant number
of its clients signal that they are able to accept the new algorithm. of its clients signal that they are able to accept the new algorithm.
Note that this survey may be conducted over the period of years Note that this survey may be conducted over the period of years
before a tipping point is seen. before a tipping point is seen.
This draft does not seek to introduce another process for including This draft does not seek to introduce another process for including
new algorithms for use with DNSSEC. It also does not address the new algorithms for use with DNSSEC. It also does not address the
question of which algorithms are to be included in any official list question of which algorithms are to be included in any official list
of mandatory or recommended cryptographic algorithms for use with of mandatory or recommended cryptographic algorithms for use with
DNSSEC. Rather, this document specifies a means by which a client DNSSEC. Rather, this document specifies a means by which a client
query can signal a set of algorithms and hashes it implements. query can signal the set of algorithms and hashes which it
implements.
2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood 2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood
(DHU) and NSEC3 Hash Understood (N3U) Using EDNS (DHU) and NSEC3 Hash Understood (N3U) Using EDNS
The ENDS0 specification outlined in The EDNS0 specification outlined in
[I-D.ietf-dnsext-rfc2671bis-edns0] defines a way to include new [I-D.ietf-dnsext-rfc2671bis-edns0] defines a way to include new
options using a standardized mechanism. These options are contained options using a standardized mechanism. These options are contained
in the RDATA of the OPT meta-RR. This document defines three new in the RDATA of the OPT meta-RR. This document defines three new
EDNS options for a client to signal which digital signature and/or EDNS options for a client to signal which digital signature and/or
hash algorithms the client supports. These options can be used hash algorithms the client supports. These options can be used
independently of each other and MAY appear in any order in the OPT independently of each other and MAY appear in any order in the OPT
RR. 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 [I-D.ietf-dnsext-rfc2671bis-edns0]:
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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 TBD3.
LIST-LENGTH is the length of the list of digital signature or hash LIST-LENGTH is the length of the list of digital signature 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 values SHOULD be in descending order of preference, with the most The values are listed in descending order of preference, with the
preferred algorithm first. For example, if a validating client most preferred algorithm first. For example, if a validating client
signals the DAU option and RSA/SHA-1, RSA/SHA-256 and prefers the signals the DAU option and RSA/SHA-1, RSA/SHA-256 and prefers the
latter, the values of ALG-CODE would be: 8 (RSA/SHA-256), 5 (RSA/ latter, the values of ALG-CODE would be: 8 (RSA/SHA-256), 5 (RSA/
SHA-1). SHA-1).
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 22-34 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 a reasonable potential future EDNS option codes and option lengths in a potential future example.
example.
3. Client Considerations 3. 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 option,
or combination thereof in the OPT meta-RR when sending a query. The or combination thereof in the OPT meta-RR when sending a query. The
validating end-system resolver sets the value(s) in the order of validating end-system resolver sets the value(s) in the order of
preference, with the most preferred algorithm(s) first as described preference, with the most preferred algorithm(s) first as described
in section 2. The end-system resolver SHOULD also set the DNSSEC-OK in section 2. The validating end-system resolver MUST also set the
bit [RFC4035] to indicate that it wishes to receive DNSSEC RRs in the DNSSEC-OK bit [RFC4035] to indicate that it wishes to receive DNSSEC
response. RRs in 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.
3.1. Stub Resolvers 3.1. 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 and
N3U options depends on whether the stub resolver elects to perform N3U options depends on whether the stub resolver elects to perform
its own validation. its own validation.
3.1.1. Validating Stub Resolvers 3.1.1. Validating Stub Resolvers
A validating stub resolver already (usually) sets the DO bit A validating stub resolver already (usually) sets the DO bit
[RFC4035] to indicate that it wishes to receive additional DNSSEC RRs [RFC4035] to indicate that it wishes to receive additional DNSSEC RRs
(i.e. RRSIG RR's) in the response. Such validating resolvers SHOULD (i.e. RRSIG RRs) in the response. Such validating resolvers SHOULD
include the DAU, DHU and/or the N3U option(s) in the OPT RR when include the DAU, DHU and/or the N3U option(s) in the OPT RR when
sending a query. This way the validating stub resolver indicates sending a query. The way the validating stub resolver indicates
which cryptographic algorithm(s) it supports by setting the values in which cryptographic algorithm(s) it supports by setting the values in
the order of preference, with the most preferred algorithm first as the order of preference, with the most preferred algorithm first as
described in Section 2. described in Section 2.
3.1.2. Non-Validating Stub Resolvers 3.1.2. Non-Validating Stub Resolvers
The DAU, DHU and N3U EDNS options are NOT RECOMMENDED for non- The DAU, DHU and N3U EDNS options are NOT RECOMMENDED for non-
validating stub resolvers. validating stub resolvers.
3.2. Recursive Resolvers 3.2. Recursive Resolvers
3.2.1. Validating Recursive Resolvers 3.2.1. 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 the DO and CD flags in option(s) when performing recursion based on the DO and CD flags in
the client request [RFC4035]. If the client of the recursive the client request [RFC4035]. If the client of the recursive
resolver did not include the DO bit in the query the recursive resolver did not include the DO bit in the query the recursive
resolver SHOULD include the option(s) according to its own local resolver MAY include the option(s) according to its own local policy.
policy.
If the client did include the DO and CD bits, but did not include the If the client did include the DO and CD bits, but did not include the
DAU, DHU and/or N3U option(s) in the query, the validating recursive DAU, DHU and/or N3U option(s) in the query, the validating recursive
resolver SHOULD NOT include the option(s) to avoid conflicts. resolver MUST NOT include the option(s) to avoid conflicts.
If the client did set the DO bit and the option(s) in the query, the If the client did set the DO bit and the option(s) in the query, the
validating recursive resolver SHOULD include the option(s) based on validating recursive resolver MUST include the option(s) based on the
the setting of the CD bit. If the CD bit is set, the validating setting of the CD bit. If the CD bit is set, the validating
recursive resolver SHOULD include the option(s) based on the client recursive resolver MUST include the option(s) based on the client
query or a superset of the client option(s) list and the validator's query or a superset of the client option(s) list and the validator's
own list (if different). If the CD bit is not set, the validating own list (if different). If the CD bit is not set, the validating
recursive resolver MAY copy the client option(s) or substitute its recursive resolver MAY copy the client option(s) or substitute its
own option list. own option list.
3.2.2. Non-validating Recursive Resolvers 3.2.2. Non-validating Recursive Resolvers
Recursive resolvers that do not do validation SHOULD copy the DAU, Recursive resolvers that do not do validation MUST copy the DAU, DHU
DHU and/or N3U option(s) seen in received queries as they represent and/or N3U option(s) seen in received queries as they represent the
the wishes of the validating downstream resolver that issued the wishes of the validating downstream resolver that issued the original
original query. query.
4. Intermediate System Considerations 4. Intermediate System Considerations
Intermediate proxies [RFC5625] that understand DNS SHOULD behave like Intermediate proxies [RFC5625] that understand DNS are RECOMMENDED to
a comparable recursive resolver when dealing with the DAU, DHU and behave like a comparable recursive resolver when dealing with the
N3U options. DAU, DHU and N3U options.
5. Server Considerations 5. 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 DNSSEC-OK (OK) bit is not set, the
server does not do any DNSSEC processing, including any recording of server does not do any DNSSEC processing, including any recording of
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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 by
IANA. This document does not seek to alter that registry in any way. 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 This draft seeks to update the "DNS EDNS Options" registry by adding
the DAU, DHU and N3U options and referencing this document. The code the DAU, DHU and N3U options and referencing this document. The code
for these options are TBD1, TBD2 and TBD3 respectively. for these options are TBD1, TBD2 and TBD3 respectively.
8. Security Considerations 8. Security Considerations
This document specifies a way for a client to signal its This document specifies a way for a client to signal its digital
cryptographic and hash algorithm knowledge to a cache or server. It signature and hash algorithm knowledge to a cache or server. It is
is not meant to be a discussion on algorithm superiority. The not meant to be a discussion on algorithm superiority. The signals
signals are optional codes contained in the OPT meta-RR used with are optional codes contained in the OPT meta-RR used with EDNS. The
EDNS. The goal of these options are to signal new algorithm uptake goal of these options are to signal new algorithm uptake in client
in client code to allow zone administrators to know when it is code to allow zone administrators to know when it is possible to
possible to complete an algorithm rollover in a DNSSEC signed zone. complete an algorithm rollover in a DNSSEC signed zone.
9. Normative References 9. Normative References
[I-D.ietf-dnsext-rfc2671bis-edns0] Damas, J., Graff, M., and P. [I-D.ietf-dnsext-rfc2671bis-edns0] Damas, J., Graff, M., and P.
Vixie, "Extension Mechanisms for Vixie, "Extension Mechanisms for
DNS (EDNS0)", draft-ietf-dnsext- DNS (EDNS0)", draft-ietf-dnsext-
rfc2671bis-edns0-08 (work in rfc2671bis-edns0-08 (work in
progress), February 2012. progress), February 2012.
[RFC2119] Bradner, S., "Key words for use [RFC2119] Bradner, S., "Key words for use
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