draft-ietf-dnsext-dnssec-algo-signal-03.txt   draft-ietf-dnsext-dnssec-algo-signal-04.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: July 6, 2012 NIST Expires: September 7, 2012 NIST
January 3, 2012 March 6, 2012
Signaling Cryptographic Algorithm Understanding in DNSSEC Signaling Cryptographic Algorithm Understanding in DNSSEC
draft-ietf-dnsext-dnssec-algo-signal-03 draft-ietf-dnsext-dnssec-algo-signal-04
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
cryptographic algorithms they support. cryptographic algorithms 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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. 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
skipping to change at page 1, line 42 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on July 6, 2012. This Internet-Draft will expire on September 7, 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
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publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Signaling DNSSEC Algorithm Understood (DAU) Using EDNS . . . . 3 2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash
Understood (DHU) and NSEC3 Hash Understood (N3U) Using EDNS . . 3
3. Client Considerations . . . . . . . . . . . . . . . . . . . . . 4 3. Client Considerations . . . . . . . . . . . . . . . . . . . . . 5
3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Validating Stub Resolvers . . . . . . . . . . . . . . . . . 5 3.2. Validating Stub Resolvers . . . . . . . . . . . . . . . . . 5
3.3. Non-Validating Stub Resolvers . . . . . . . . . . . . . . . 5 3.3. Non-Validating Stub Resolvers . . . . . . . . . . . . . . . 5
3.4. Recursive Resolvers . . . . . . . . . . . . . . . . . . . . 5 3.4. Recursive Resolvers . . . . . . . . . . . . . . . . . . . . 5
3.4.1. Validating Recursive Resolvers . . . . . . . . . . . . 5 3.4.1. Validating Recursive Resolvers . . . . . . . . . . . . 5
3.4.2. Non-validating Recursive Resolvers . . . . . . . . . . 5 3.4.2. Non-validating Recursive Resolvers . . . . . . . . . . 6
4. Intermediate System Considerations . . . . . . . . . . . . . . 6 4. Intermediate System Considerations . . . . . . . . . . . . . . 6
5. Server Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. Server Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Traffic Analysis Considerations . . . . . . . . . . . . . . . . 6 6. Traffic Analysis Considerations . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
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 tells validators which cryptographic algorithm
was used to generate the digital signature. was used to generate the digital signature.
Likewise, Delegated Signer (DS) RR's and NSEC3 RR's use a hashed
value as part of their RDATA and like digital signature algorithms,
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 draft sets out to specify a way for validating end-system
resolvers to tell a server which cryptographic algorithms they resolvers to tell a server which cryptographic and/or hash algorithms
support in a DNS query. This is done using the EDNS attribute values they support in a DNS query. This is done using the EDNS attribute
in the OPT meta-RR [RFC2671]. values in the OPT meta-RR [RFC2671].
This proposed EDNS option serves to measure the acceptance and use of These proposed EDNS options serve to measure the acceptance and use
new digital signing algorithms. This algorithm signaling option can of new digital signing algorithms. These signaling options can be
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 a newly deployed digital signature
algorithm used with DNSSEC. A zone administrator may be able to and hash algorithm, DS hash and NSEC3 hash algorithm used with
determine when to stop serving the old algorithm when the server sees DNSSEC. A zone administrator may be able to determine when to stop
that a significant number of its clients signal that they are able to signing with the old algorithm(s) when the server sees that a
accept the new algorithm. Note that this survey may be conducted significant number of its clients signal that they are able to accept
over the period of years before a tipping point is seen. the new algorithm. Note that this survey may be conducted over the
period of years before a tipping point is seen.
This draft does not seek to include another process for including new This draft does not seek to introduce another process for including
algorithms for use with DNSSEC (see . 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 it implements. query can signal a set of algorithms and hashes it implements.
2. Signaling DNSSEC Algorithm Understood (DAU) Using EDNS 2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood
(DHU) and NSEC3 Hash Understood (N3U) Using EDNS
The ENDS0 specification outlined in [RFC2671] defines a way to The ENDS0 specification outlined in [RFC2671] defines a way to
include new options using a standardized mechanism. These options include new options using a standardized mechanism. These options
are contained in the RDATA of the OPT meta-RR. This document defines are contained in the RDATA of the OPT meta-RR. This document defines
a new EDNS0 option for a client to signal which algorithms the client three new EDNS0 options for a client to signal which digital
supports. signature and/or hash algorithms the client supports. These options
can be used independly of each other and MAY appear in any order in
the OPT RR.
The figure below shows how the digital signature signaling attribute The figure below shows how each option is defined in the RDATA of the
is defined in the RDATA of the OPT RR specified in [RFC2671]: OPT RR specified in [RFC2671]:
0 8 16 0 8 16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-CODE (TBD) | | OPTION-CODE (TBD) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| DIGITAL-SIG-LIST-LENGTH | | LIST-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ALG-CODE | ... \ | ALG-CODE | ... \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
OPTION-CODE is the code for the DNSSEC Algorithm Understood (DAU) OPTION-CODE is the code for the given signaling option. They are:
option. Its value is fixed at TBD.
DIGITAL-SIG-LIST-LENGTH is the length of the list of digital o DNSSEC Algorithm Understood (DAU) option for DNSSEC digital
signature algorithms in octets. DNSSEC algorithm codes are 1 octet signing algorithms. Its value is fixed at TBD1.
long so this value is the number of octets.
o DS Hash Understood (DHU) option for DS RR hash algorithms. Its
value is fixed at TBD2.
o NSEC3 Hash Understood (N3U) option for NSEC3 hash algorithms. Its
value is fixed at TBD3.
LIST-LENGTH is the length of the list of digital signature or hash
algorithms in octets. Since each algorithm and hash codes are 1
octet long so this value is the number of octets.
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 that the client indicates as understood. The values algorithms, DS hash algorithms, or NSEC3 hash algorithms (depending
SHOULD be in descending order of preference, with the most preferred on the OPTION-CODE in use) that the client indicates as understood.
algorithm first. For example, if a validating client implements RSA/ The values SHOULD be in descending order of preference, with the most
SHA-1, RSA/SHA-256 and prefers the latter, the value of ALG-CODE preferred algorithm first. For example, if a validating client
would be: 8 (RSA/SHA-256), 5 (RSA/SHA-1). 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/
SHA-1).
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.
However, in practical terms including all three options are likely to
take up 16-24 octets (average of 6-10 digital signature algorithms,
3-5 DS hash algorithms and 1-5 NSEC3 hash algorithms) including the
EDNS option codes and option lengths in a reasonable potential future
example.
3. Client Considerations 3. Client Considerations
A validating end-system resolver sets the DAU option in the OPT A validating end-system resolver sets the DAU, DHU and/or N3U option,
meta-RR when sending a query. The validating end-system resolver or combination thereof in the OPT meta-RR when sending a query. The
sets the value(s) in the order of preference, with the most preferred validating end-system resolver sets the value(s) in the order of
algorithm(s) first as described in section 2. The end-system preference, with the most preferred algorithm(s) first as described
resolver SHOULD also set the DNSSEC-OK bit [RFC4035] to indicate that in section 2. The end-system resolver SHOULD also set the DNSSEC-OK
it wishes to receive DNSSEC RRs in the response. bit [RFC4035] to indicate that it wishes to receive DNSSEC RRs in the
response.
Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) codes Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) digital
cover a potentially wide range of algorithms and are likely not signature codes for cover a potentially wide range of algorithms and
useful to a server. There is no compelling reason for a client to are likely not useful to a server. There is no compelling reason for
include these codes in its list of understood algorithms. a client to include these codes in its list of the DAU. Likewise,
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 option cache) to provide a response. So optimal setting of the DAU, DSU and
depends on whether the stub resolver performs its own DNSSEC N3U options depends on whether the stub resolver performs its own
validation or doesn't perform its own validation. DNSSEC validation or doesn't perform its own validation.
3.2. Validating Stub Resolvers 3.2. 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 RR's) in the response. Such validating resolvers SHOULD
include the DAU option in the OPT RR when sending a query. This way include the DAU, DHU and/or the N3U option(s) in the OPT RR when
thee validating stub resolver indicates which cryptographic sending a query. This way thee validating stub resolver indicates
algorithm(s) it supports by setting the values(s) in the order of which cryptographic algorithm(s) it supports by setting the values(s)
preference, with the most preferred algorithm(s) first as described in the order of preference, with the most preferred algorithm(s)
in Section 2. first as described in Section 2.
3.3. Non-Validating Stub Resolvers 3.3. Non-Validating Stub Resolvers
The DAU EDNS option is NOT RECOMMENDED for non-validating stub The DAU, DHU and N3U EDNS options are NOT RECOMMENDED for non-
resolvers. validating stub resolvers.
3.4. Recursive Resolvers 3.4. Recursive Resolvers
3.4.1. Validating Recursive Resolvers 3.4.1. Validating Recursive Resolvers
A validating recursive resolver sets the DAU option when performing A validating recursive resolver sets the DAU, DHU and/or N3U
recursion based on the DO and CD flags in the client request option(s) when performing recursion based on the DO and CD flags in
[RFC4035]. If the client of the recursive resolver did not include the client request [RFC4035]. If the client of the recursive
the DO bit in the query the recursive resolver SHOULD include the DAU resolver did not include the DO bit in the query the recursive
option according to its own local policy. resolver SHOULD include the option(s) according to its own local
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 option in the query, the validating recursive resolver SHOULD NOT DAU, DHU and/or N3U option(s) in the query, the validating recursive
include the DAU option to avoid conflicts. resolver SHOULD NOT include the option(s) to avoid conflicts.
If the client did set the DO bit and the DAU option 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 DAU option based on validating recursive resolver SHOULD include the option(s) based on
the setting of the CD bit. If the CD bit is set, the validating the setting of the CD bit. If the CD bit is set, the validating
recursive resolver SHOULD include the DAU option based on the client recursive resolver SHOULD include the option(s) based on the client
query or a superset of the client DAU option 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 DAU option or substitute its recursive resolver MAY copy the client option(s) or substitute its
own DAU option list. own option list.
3.4.2. Non-validating Recursive Resolvers 3.4.2. Non-validating Recursive Resolvers
Recursive resolvers that do not do validation or caching SHOULD copy Recursive resolvers that do not do validation SHOULD copy the DAU,
the DAU option seen in received queries as they represent the wishes DHU and/or N3U option(s) seen in received queries as they represent
of the validating downstream resolver that issued the original query. the wishes of the validating downstream resolver that issued the
original query.
4. Intermediate System Considerations 4. Intermediate System Considerations
Intermediate proxies [RFC5625] that understand DNS SHOULD behave like Intermediate proxies [RFC5625] that understand DNS SHOULD behave like
a comparable recursive resolver when dealing with the DAU option. a comparable recursive resolver when dealing with the DAU, DHU and
N3U options.
5. Server Considerations 5. Server Considerations
When an authoritative server sees the DAU option in the OPT meta-RR When an authoritative server sees the DAU, DHU and/or N3U option(s)
in a request the normal algorithm for servicing requests is followed. in the OPT meta-RR in a request the normal algorithm for servicing
The DAU option does not trigger any special processing on the server requests is followed. The options does not trigger any special
side. processing on the server side.
If the DAU option is present but the DNSSEC-OK (OK) bit is not set, If the options are present but the DNSSEC-OK (OK) bit is not set, the
the server does not do any DNSSEC processing, including any recording server does not do any DNSSEC processing, including any recording of
of the DAU option. the option(s).
6. Traffic Analysis Considerations 6. 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 values of the DAU option in queries. This traffic and record the values of the DAU/DHU/N3U option(s) in
monitoring can measure the deployment of client code that implements queries. This monitoring can measure the deployment of client code
(and signals) certain algorithms. Exactly how to capture DNS traffic that implements (and signals) certain algorithms. Exactly how to
and measure new algorithm adoption is beyond the scope of this capture DNS traffic and measure new algorithm adoption is beyond the
document. scope of this document.
Zone administrators can use this data to set plans for starting an Zone administrators can use this data to set plans for starting an
algorithm rollover and determine when older algorithms can be phased algorithm rollover and determine when older algorithms can be phased
out without disrupting a significant number of clients. In order to out without disrupting a significant number of clients. In order to
keep this disruption to a minimum, zone administrators should wait to keep 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 understand the new algorithm. This may be in the signal that they understand the new algorithm. This may be in the
order of years rather than months. Note that clients that do not order of years rather than months. Note that clients that do not
implement the DAU option are likely to be older implementations which implement these options are likely to be older implementations which
would also not implement any newly deployed algorithm. would also not implement any newly deployed algorithm.
7. IANA Considerations 7. IANA Considerations
The algorithm codes used to identify DNSSEC algorithms has already The algorithm codes used to identify DNSSEC algorithms, DS RR hash
been established by IANA. This document does not seek to alter that algorithms and NSEC3 hash algorithms have already been established by
registry in any way. IANA. This document does not seek to alter that registry in any way.
This draft seeks to update the "DNS EDNS0 Options" registry by adding This draft seeks to update the "DNS EDNS0 Options" registry by adding
the DAU option and referencing this document. The code for the the DAU, DHU and N3U options and referencing this document. The code
option should be TBD. 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 digital This document specifies a way for a client to signal its
signature algorithm preference to a cache or server. It is not meant cryptographic and hash algorithm knowledge to a cache or server. It
to be a discussion on algorithm superiority. The signal is an is not meant to be a discussion on algorithm superiority. The
optional code contained in the OPT meta-RR used with EDNS0. The goal signals are optional codes contained in the OPT meta-RR used with
of this option is to signal new algorithm uptake in client code to EDNS0. The goal of these options are to signal new algorithm uptake
allow zone administrators to know when it is possible to complete an in client code to allow zone administrators to know when it is
algorithm rollover in a DNSSEC signed zone. possible to complete an algorithm rollover in a DNSSEC signed zone.
9. Normative References 9. Normative References
[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.
[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
RFC 2671, August 1999. RFC 2671, August 1999.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
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