draft-ietf-dnsext-dnssec-algo-signal-09.txt   draft-ietf-dnsext-dnssec-algo-signal-10.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: March 28, 2013 NIST Expires: October 10, 2013 NIST
September 24, 2012 April 08, 2013
Signaling Cryptographic Algorithm Understanding in DNSSEC Signaling Cryptographic Algorithm Understanding in DNSSEC
draft-ietf-dnsext-dnssec-algo-signal-09 draft-ietf-dnsext-dnssec-algo-signal-10
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 digital validating end-system resolvers to signal to a server which digital
signature and hash algorithms they support. signature and hash algorithms they support. The proposed extensions
allow the signaling of new algorithm uptake in client code to allow
zone administrators to know when it is possible to complete an
algorithm rollover in a DNSSEC signed zone.
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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC "OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119]. 2119 [RFC2119].
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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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 March 28, 2013. This Internet-Draft will expire on October 10, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2013 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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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash 2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash
Understood (DHU) and NSEC3 Hash Understood (N3U) Using EDNS . . 3 Understood (DHU) and NSEC3 Hash Understood (N3U) Using EDNS . 3
3. Client Considerations . . . . . . . . . . . . . . . . . . . . 4
3. Client Considerations . . . . . . . . . . . . . . . . . . . . . 5 3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . 5
3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . . 5 3.1.1. Validating Stub Resolvers . . . . . . . . . . . . . . 5
3.1.1. Validating Stub Resolvers . . . . . . . . . . . . . . . 5 3.1.2. Non-Validating Stub Resolvers . . . . . . . . . . . . 5
3.1.2. Non-Validating Stub Resolvers . . . . . . . . . . . . . 5 3.2. Recursive Resolvers . . . . . . . . . . . . . . . . . . . 5
3.2. Recursive Resolvers . . . . . . . . . . . . . . . . . . . . 5 3.2.1. Validating Recursive Resolvers . . . . . . . . . . . 5
3.2.1. Validating Recursive Resolvers . . . . . . . . . . . . 5 3.2.2. Non-validating Recursive Resolvers . . . . . . . . . 6
3.2.2. Non-validating Recursive Resolvers . . . . . . . . . . 6 4. Intermediate System Considerations . . . . . . . . . . . . . 6
5. Server Considerations . . . . . . . . . . . . . . . . . . . . 6
4. Intermediate System Considerations . . . . . . . . . . . . . . 6 6. Traffic Analysis Considerations . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Server Considerations . . . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . 8
6. Traffic Analysis Considerations . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 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 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, Delegation Signer (DS) RRs and NSEC3 RRs use a hashed value
as part of their RDATA and, like digital signature algorithms, these as part of their RDATA and, like digital signature algorithms, these
hash algorithms have code numbers. All three algorithm codes (RRSIG/ hash algorithms have code numbers. All three algorithm codes (RRSIG/
DNSKEY, DS and NSEC3) are maintained in unique IANA registries. 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 in a DNS query which digital signature resolvers to tell a server in a DNS query which digital signature and
and/or hash algorithms they support. This is done using the new EDNS /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]. These three new EDNS option [I-D.ietf-dnsext-rfc2671bis-edns0]. These three new EDNS option
codes are all OPTIONAL to implement and use. codes are all OPTIONAL to implement and use.
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 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 is able to determine when to stop signing with a administrator is able to determine when to stop signing with a
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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 a potential future example. EDNS option codes and option lengths in potential future examples.
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 MUST also set the DNSSEC-OK bit validating end-system resolver MUST also set the DNSSEC-OK bit
[RFC4035] to indicate that it wishes to receive DNSSEC RRs in the [RFC4035] to indicate that it wishes to receive DNSSEC RRs in the
response. 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
implements and MAY choose to only list algorithms the client wishes
to signal as understood.
Since the DAU, DHU and/or N3U options are only set in the query, if a
client sees these options in the response, no action needs to be
taken and the client MUST ignore the option values.
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
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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 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 to a options set, the recursive server MUST set the algorithm list for any
union of the stub client's list and the validating recursive outgoing iterative queries for that resolution chain to a union of
resolver's list. For example, if the recursive resolver's algorithm the stub client's list and the validating recursive resolver's list.
list for the DAU option is (3, 5, 7) and the stub's algorithm list is For example, if the recursive resolver's algorithm list for the DAU
(7, 8), the final DAU algorithm list would be (3, 5, 7, 8). 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).
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 MAY include the option(s) with its own list in full. If one resolver MAY include the option(s) with its own list in full. If one
or more of the options are missing, the validating recursive resolver or more of the options are missing, the validating recursive resolver
MAY include the missing options with its own list in full. MAY include the missing options with its own list in full.
Validating recursive resolvers MUST NOT set the DAU, DHU and/or N3U
option(s) in the final response to the stub client.
3.2.2. Non-validating Recursive Resolvers 3.2.2. 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 4. Intermediate System Considerations
Intermediate proxies [RFC5625] that understand DNS are RECOMMENDED to Intermediate proxies [RFC5625] (Section 4.4.2) that understand DNS
behave like a comparable recursive resolver when dealing with the are RECOMMENDED to behave like a comparable recursive resolver when
DAU, DHU and N3U options. dealing with the 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
the option(s). the option(s).
6. Traffic Analysis Considerations If the server sees one (or more) of the options set with RESERVED
values, the server MAY ignore recoding of those values.
Authoritative servers MUST NOT set the DAU, DHU and/or N3U option(s)
on any responses. These values are only set in queries.
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 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. 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
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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 9. Normative References
[I-D.ietf-dnsext-rfc2671bis-edns0] Damas, J., Graff, M., and P. [I-D.ietf-dnsext-rfc2671bis-edns0]
Vixie, "Extension Mechanisms for Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
DNS (EDNS0)", draft-ietf-dnsext- for DNS (EDNS(0))", draft-ietf-dnsext-rfc2671bis-edns0-10
rfc2671bis-edns0-09 (work in (work in progress), December 2012.
progress), August 2012.
[RFC2119] Bradner, S., "Key words for use [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
in RFCs to Indicate Requirement Requirement Levels", BCP 14, RFC 2119, March 1997.
Levels", BCP 14, RFC 2119,
March 1997.
[RFC4033] Arends, R., Austein, R., Larson, [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
M., Massey, D., and S. Rose, "DNS Rose, "DNS Security Introduction and Requirements", RFC
Security Introduction and 4033, March 2005.
Requirements", RFC 4033,
March 2005.
[RFC4034] Arends, R., Austein, R., Larson, [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
M., Massey, D., and S. Rose, Rose, "Resource Records for the DNS Security Extensions",
"Resource Records for the DNS RFC 4034, March 2005.
Security Extensions", RFC 4034,
March 2005.
[RFC4035] Arends, R., Austein, R., Larson, [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
M., Massey, D., and S. Rose, Rose, "Protocol Modifications for the DNS Security
"Protocol Modifications for the Extensions", RFC 4035, March 2005.
DNS Security Extensions",
RFC 4035, March 2005.
[RFC5625] Bellis, R., "DNS Proxy [RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", BCP
Implementation Guidelines", 152, RFC 5625, August 2009.
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
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