draft-ietf-dnsext-dnssec-algo-signal-00.txt   draft-ietf-dnsext-dnssec-algo-signal-01.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: May 13, 2011 NIST Expires: October 1, 2011 NIST
November 9, 2010 March 30, 2011
Signaling Cryptographic Algorithm Understanding in DNSSEC Signaling Cryptographic Algorithm Understanding in DNSSEC
draft-ietf-dnsext-dnssec-algo-signal-00 draft-ietf-dnsext-dnssec-algo-signal-01
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 they support.
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 May 13, 2011. This Internet-Draft will expire on October 1, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Signaling Algorithm Understood (AU) Using EDNS . . . . . . . . 3 2. Signaling DNSSEC Algorithm Understood (DAU) Using EDNS . . . . 3
3. Client Considerations . . . . . . . . . . . . . . . . . . . . . 4 3. Client Considerations . . . . . . . . . . . . . . . . . . . . . 4
3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . . 5 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 . . . . . . . . . . 6 3.4.2. Non-validating Recursive Resolvers . . . . . . . . . . 6
4. Intermediate Middlebox Considerations . . . . . . . . . . . . . 6 4. Intermediate Middlebox 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. Authentication across was used to generate the digital signature. Authentication across
delegation boundries is maintained by storing a hash of a subzone's delegation boundaries is maintained by storing a hash of a subzone's
key in the parent zone stored in a Delegation Signer (DS) RR. These key in the parent zone stored in a Delegation Signer (DS) RR. These
DS RR's contain a second code number to identify the hash algorithm DS RR's contain a second code number to identify the hash algorithm
used to contruct the DS RR. used to construct the DS RR.
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 and/or hash algorithms resolvers to tell a server which cryptographic and/or hash algorithms
they support in a DNS query. This is done using the EDNS attribute they support in a DNS query. This is done using the EDNS attribute
values 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 This proposed EDNS option serves to measure the acceptance and use of
new digital signing and hash algorithms. This algorithm signaling new digital signing and hash algorithms. This algorithm signaling
option can be used by zone administrators as a gauge to measure the option can be used by zone administrators as a gauge to measure the
successful deployment of code that implements a newly deployed successful deployment of code that implements a newly deployed
digital signature or hash algorithm used with DNSSEC. A zone digital signature or hash algorithm used with DNSSEC. A zone
administrator may be able to determine when to stop serving the old administrator may be able to determine when to stop serving the old
algorithm when the server sees that all or almost all of its clients algorithm when the server sees that a significant number of its
signal that they are able to accept the new algorithm. clients signal that they are able to accept 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 include another process for including new
algorithms for use with DNSSEC (see . It also does not address the 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 it implements.
2. Signaling Algorithm Understood (AU) Using EDNS 2. Signaling DNSSEC Algorithm Understood (DAU) 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 a new EDNS0 option for a client to signal which algorithms the client
supports. supports.
The figure below shows how the signally attribute is defined in the The figure below shows how the signaling attribute is defined in the
RDATA of the OPT RR specified in [RFC2671]: RDATA of the OPT RR specified in [RFC2671]:
0 8 16 0 8 16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-CODE (TBD) | | OPTION-CODE (TBD) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| DIGITAL-SIG-LIST-LENGTH | | DIGITAL-SIG-LIST-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ALG-CODE | ... \ | ALG-CODE | ... \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| DS-HASH-LIST-LENGTH | | DS-HASH-LIST-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| HASH-CODE | ... \ | HASH-CODE | ... \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
OPTION-CODE is the code for the Algorithm Understood (AU) option. OPTION-CODE is the code for the DNSSEC Algorithm Understood (DAU)
Its value is fixed at TBD. option. Its value is fixed at TBD.
DIGITAL-SIG-LIST-LENGTH is the length of the list of digital DIGITAL-SIG-LIST-LENGTH is the length of the list of digital
signature algorithms in octets. DNSSEC algorithm codes are 1 octet signature algorithms in octets. DNSSEC algorithm codes are 1 octet
long so this value is the number of octets. 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 that the client indicates it understands. The values
SHOULD be in descending order of preference, with the most preferred SHOULD be in descending order of preference, with the most preferred
algorithm first. For example, if a validating client implements RSA/ algorithm first. For example, if a validating client implements RSA/
SHA-1, RSA/SHA-256 and prefers the latter, the value of ALG-CODE SHA-1, RSA/SHA-256 and prefers the latter, the value of ALG-CODE
would be: 8 (RSA/SHA-256), 5 (RSA/SHA-1). would be: 8 (RSA/SHA-256), 5 (RSA/SHA-1).
DS-HASH-LIST-LENGTH is the length of the list of hash algorithms in DS-HASH-LIST-LENGTH is the length of the list of hash algorithms in
octets. DNSSEC DS hash codes are 1 octet long so this value is the octets. DNSSEC DS hash codes are 1 octet long so this value is the
number of octets. number of octets.
HASH-CODE is the list of assigned values of DNSSEC DS hash algorithms HASH-CODE is the list of assigned values of DNSSEC DS hash algorithms
that the client indicates as understood. Like the ALG-CODE above, that the client indicates as understood. Like the ALG-CODE above,
the values SHOULD be in descending order of preference, with the most the values SHOULD be in descending order of preference, with the most
preferred algorithm first. preferred algorithm first.
3. Client Considerations 3. Client Considerations
A validating end-system resolver sets the AU option in the OPT A validating end-system resolver sets the DAU option in the OPT
meta-RR when sending a query. The validating end-system resolver meta-RR when sending a query. The validating end-system resolver
sets the value(s) in the order of preference, with the most preferred sets the value(s) in the order of preference, with the most preferred
algorithm(s) first as described in section 2. The end-system algorithm(s) first as described in section 2. The end-system
resolver MUST also set the DNSSEC-OK bit [RFC4035] to indicate that resolver SHOULD also set the DNSSEC-OK bit [RFC4035] to indicate that
it wishes to receive DNSSEC RRs in the response. it wishes to receive DNSSEC RRs in the response.
Note that when including the PRIVATEDNS (253) and/or the PRIVATEOID Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) codes
(254) codes, the client only indicates that it understands one or cover a potentially wide range of algorithms and are likely not
more private algorithms but does not indicate which algorithms. useful to a server. There is no compelling reason for a client to
include these codes in its list of understood algorithms.
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; any algorithm support on the stub cache) to provide a response; any algorithm support on the stub
resolver's side could be overruled by the upstream recursive server. resolver's side SHOULD be honored (if possible) by an upstream
recursive cache.
3.2. Validating Stub Resolvers 3.2. Validating Stub Resolvers
A validating stub resolver MUST set the DO bit [RFC4035] to indicate A validating stub resolver MUST set the DO bit [RFC4035] to indicate
that it wishes to receive DNSSEC RRs in the response. Such that it wishes to receive DNSSEC RRs in the response. Such
validating resolvers MAY include the AU option in the OPT RR when validating resolvers SHOULD include the DAU option in the OPT RR when
sending a query. The validating resolver that way indicates which sending a query. This way the validating stub resolver indicates
cryptographic algorithm(s) in supports by setting the values(s) in which cryptographic algorithm(s) it supports by setting the values(s)
the order of preference, with the most preferred algorithm(s) first in the order of preference, with the most preferred algorithm(s)
as described in Section 2. first as described in Section 2.
3.3. Non-Validating Stub Resolvers 3.3. Non-Validating Stub Resolvers
The AU EDNS option is NOT RECOMMENDED for non-validating stub The DAU EDNS option is NOT RECOMMENDED for non-validating stub
resolvers. 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 MUST set the DO bit [RFC4035] to A validating recursive resolver MUST set the DO bit [RFC4035] to
indicate that is wishes to receive DNSSEC RRs in the response. If indicate that it wishes to receive DNSSEC RRs in the response. If
the client the recursive resolver did not include the DO bit in the the client of the recursive resolver did not include the DO bit in
query the recursive resolver MAY include the AU option according to the query the recursive resolver SHOULD include the DAU option
its own local policy. 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
AU option in the query, the validating recursive resolver SHOULD NOT DAU option in the query, the validating recursive resolver SHOULD NOT
include the AU option to avoid conflicts. include the DAU option to avoid conflicts.
If the client did set the DO bit and the AU option in the query, the If the client did set the DO bit and the DAU option in the query, the
validating recursive resolver MAY include the AU option based on its validating recursive resolver SHOULD include the DAU option based on
own local policy if it does validation. If not, the recursive the setting of the CD bit. If the CD bit is set, the validating
resolver SHOULD copy the value of the AU option in the client query. recursive resolver SHOULD include the DAU option based on the client
query or a superset of the client DAU option list and the validator's
own list (if different). If the CD bit is not set, the validating
recursive resolver MAY copy the client DAU option or substitute its
own DAU 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 or caching SHOULD copy
the AU option seen in received queries as they represent the wishes the DAU option seen in received queries as they represent the wishes
of the validating downstream resolver that issued the original query. of the validating downstream resolver that issued the original query.
4. Intermediate Middlebox Considerations 4. Intermediate Middlebox Considerations
Intermediate middleboxes SHOULD behave like a comperable recursive Intermediate middleboxes SHOULD behave like a comparable recursive
resolver when dealing with the AU option. resolver when dealing with the DAU option [RFC5625].
5. Server Considerations 5. Server Considerations
When an authoritative server sees the AU option in the OPT meta-RR in When an authoritative server sees the DAU option in the OPT meta-RR
a request the normal algorithm for servicing requests is followed. in a request the normal algorithm for servicing requests is followed.
The DAU option does not trigger any special processing on the server
side.
If the AU option is present but the DNSSEC-OK bit is not set, then If the DAU option is present but the DNSSEC-OK (OK) bit is not set,
the authoritative server ignores the ALG-CODE list and does not the server does not do any DNSSEC processing, including any recording
include any additional DNSSEC RRs in the response. of the DAU option.
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 AU option in queries. This traffic and record the values of the DAU option in queries. This
monitoring can measure the deployment of client code that implements monitoring can measure the deployment of client code that implements
(and signals) certain algorithms. Exactly how to capture DNS traffic (and signals) certain algorithms. Exactly how to capture DNS traffic
and measure new algorithm adoption is beyond the scope of this and measure new algorithm adoption is beyond the scope of this
document. 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 when older algorithms can be phased out algorithm rollover and determine when older algorithms can be phased
without disrupting the majority of clients. In order to keep this out without disrupting a significant number of clients. In order to
disruption to a minimum, zone administrators should wait to complete keep this disruption to a minimum, zone administrators should wait to
an algorithm rollover until a large majority of clients signal that complete an algorithm rollover until a large majority of clients
they understand the new algorithm. Note that clients that do not signal that they understand the new algorithm. This may be in the
implement the AU option may be older implementations which would also order of years rather than months. Note that clients that do not
not implement any newly deployed algorithm. implement the DAU option are likely to be older implementations which
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 has already
been established by IANA. This document does not seek to alter that been established by IANA. This document does not seek to alter that
registry in any way. 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 AU option and referencing this document. The code for the option the DAU option and referencing this document. The code for the
should be TBD. option should be TBD.
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 digital
signature algorithm preference to a cache or server. It is not meant signature algorithm preference to a cache or server. It is not meant
to be a discussion on algorithm superiority. The signal is an to be a discussion on algorithm superiority. The signal is an
optional code contained in the OPT meta-RR used with EDNS0. The goal optional code contained in the OPT meta-RR used with EDNS0. The goal
of this option is to signal new algorithm uptake in client code to of this option is to signal new algorithm uptake in client code to
allow zone administrators to know when it is possible to complete an allow zone administrators to know when it is possible to complete an
algorithm rollover in a DNSSEC signed zone. algorithm rollover in a DNSSEC signed zone.
skipping to change at page 7, line 35 skipping to change at page 7, line 45
RFC 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 152, RFC 5625, August 2009.
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
Scott Rose Scott Rose
NIST NIST
100 Bureau Dr. 100 Bureau Dr.
Gaithersburg, MD 20899 Gaithersburg, MD 20899
USA USA
Phone: +1-301-975-8439 Phone: +1-301-975-8439
EMail: scottr.nist@gmail.com EMail: scottr.nist@gmail.com
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