draft-ietf-dnsop-nsec-aggressiveuse-08.txt   draft-ietf-dnsop-nsec-aggressiveuse-09.txt 
Network Working Group K. Fujiwara Network Working Group K. Fujiwara
Internet-Draft JPRS Internet-Draft JPRS
Updates: 4035 (if approved) A. Kato Updates: 4035 (if approved) A. Kato
Intended status: Standards Track Keio/WIDE Intended status: Standards Track Keio/WIDE
Expires: July 16, 2017 W. Kumari Expires: October 1, 2017 W. Kumari
Google Google
January 12, 2017 March 30, 2017
Aggressive use of DNSSEC-validated Cache Aggressive use of DNSSEC-validated Cache
draft-ietf-dnsop-nsec-aggressiveuse-08 draft-ietf-dnsop-nsec-aggressiveuse-09
Abstract Abstract
The DNS relies upon caching to scale; however, the cache lookup The DNS relies upon caching to scale; however, the cache lookup
generally requires an exact match. This document specifies the use generally requires an exact match. This document specifies the use
of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers of NSEC/NSEC3 resource records to allow DNSSEC validating resolvers
to generate negative answers within a range, and positive answers to generate negative answers within a range, and positive answers
from wildcards. This increases performance / decreases latency, from wildcards. This increases performance / decreases latency,
decreases resource utilization on both authoritative and recursive decreases resource utilization on both authoritative and recursive
servers, and also increases privacy. It may also help increase servers, and also increases privacy. It may also help increase
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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 July 16, 2017. This Internet-Draft will expire on October 1, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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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5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 6
5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7 5.4. Consideration on TTL . . . . . . . . . . . . . . . . . . 7
6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8 7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Change History . . . . . . . . . . . . . . . . . . . . . 10 11.1. Change History . . . . . . . . . . . . . . . . . . . . . 9
11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 13 11.1.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . 13
11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 13 11.1.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . 13
11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13 11.1.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . 13
11.2. new section . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . 13 12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 14 12.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Detailed implementation notes . . . . . . . . . . . 14 Appendix A. Detailed implementation notes . . . . . . . . . . . 15
Appendix B. Procedure for determining ENT vs NXDOMAN with NSEC . 15 Appendix B. Procedure for determining ENT vs NXDOMAN with NSEC . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
A DNS negative cache exists, and is used to cache the fact that an A DNS negative cache exists, and is used to cache the fact that an
RRset does not exist. This method of negative caching requires exact RRset does not exist. This method of negative caching requires exact
matching; this leads to unnecessary additional lookups, increases matching; this leads to unnecessary additional lookups, increases
latency, leads to extra resource utilization on both authoritative latency, leads to extra resource utilization on both authoritative
and recursive servers, and decreases privacy by leaking queries. and recursive servers, and decreases privacy by leaking queries.
This document updates RFC 4035 to allow recursive resolvers to use This document updates RFC 4035 to allow resolvers to use NSEC/NSEC3
NSEC/NSEC3 resource records to synthesize negative answers from the resource records to synthesize negative answers from the information
information they have in the cache. This allows validating resolvers they have in the cache. This allows validating resolvers to respond
to respond with a negative answer immediately if the name in question with a negative answer immediately if the name in question falls into
falls into a range expressed by a NSEC/NSEC3 resource record already a range expressed by a NSEC/NSEC3 resource record already in the
in the cache. It also allows the synthesis of positive answers in cache. It also allows the synthesis of positive answers in the
the presence of wildcard records. presence of wildcard records.
Aggressive Negative Caching was first proposed in Section 6 of DNSSEC Aggressive Negative Caching was first proposed in Section 6 of DNSSEC
Lookaside Validation (DLV) [RFC5074] in order to find covering NSEC Lookaside Validation (DLV) [RFC5074] in order to find covering NSEC
records efficiently. records efficiently.
[RFC8020], and [I-D.vixie-dnsext-resimprove] proposes first steps to [RFC8020] and [I-D.vixie-dnsext-resimprove] propose steps to using
using NXDOMAIN information for more effective caching. This takes NXDOMAIN information for more effective caching. This document takes
this technique further. this technique further.
2. Terminology 2. Terminology
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].
Many of the specialized terms used in this document are defined in Many of the specialized terms used in this document are defined in
DNS Terminology [RFC7719]. DNS Terminology [RFC7719].
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attackers to cause a DoS (see additional resources), and also has attackers to cause a DoS (see additional resources), and also has
privacy implications (e.g: typos leak out further than necessary). privacy implications (e.g: typos leak out further than necessary).
Another example: assume that the (DNSSEC signed) "example.org" zone Another example: assume that the (DNSSEC signed) "example.org" zone
contains: contains:
avocado.example.org IN A 192.0.2.1 avocado.example.org IN A 192.0.2.1
*.example.org IN A 192.0.2.2 *.example.org IN A 192.0.2.2
zucchini.example.org IN A 192.0.2.3 zucchini.example.org IN A 192.0.2.3
If a query is received for leek.example.org, it contacts its resolver If a query is received for leek.example.org, the system contacts its
(which may be itself) to query the example.org servers and will get resolver (which may be itself) to query the example.org servers and
back an NSEC record stating that there are no records will get back an NSEC record stating that there are no records
(alphabetically) between avocado and zucchini (or an NSEC3 record (alphabetically) between avocado and zucchini (or an NSEC3 record
stating there is nothing between two hashed names), as well as an stating there is nothing between two hashed names), as well as an
answer for leek.example.org, with the label count of the signature answer for leek.example.org, with the label count of the signature
set to two (see [RFC7129], section 5.3 for more details). set to two (see [RFC7129], section 5.3 for more details).
If the validating resolver gets a query for banana.example.org it If the validating resolver gets a query for banana.example.org it
will once again go off and query the example.org servers for will once again go off and query the example.org servers for
banana.example.org (even though it already has proof that there is a banana.example.org (even though it already has proof that there is a
wildcard record) - just like above, this has privacy implications, wildcard record) - just like above, this has privacy implications,
wastes resources, can be used to contribute to a DoS, etc. wastes resources, can be used to contribute to a DoS, etc.
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that name using the cached deduced wildcard. If the corresponding that name using the cached deduced wildcard. If the corresponding
wildcard record is not in the cache, it MUST fall back to send the wildcard record is not in the cache, it MUST fall back to send the
query to the authoritative DNS servers. query to the authoritative DNS servers.
5.4. Consideration on TTL 5.4. Consideration on TTL
The TTL value of negative information is especially important, The TTL value of negative information is especially important,
because newly added domain names cannot be used while the negative because newly added domain names cannot be used while the negative
information is effective. information is effective.
Section 5 of [RFC2308] states that the maximum number of negative Section 5 of [RFC2308] suggests a maximum default negative cache TTL
cache TTL value is 3 hours (10800). It is RECOMMENDED that value of 3 hours (10800). It is RECOMMENDED that validating
validating resolvers limit the maximum effective TTL value of resolvers limit the maximum effective TTL value of negative responses
negative responses (NSEC/NSEC3 RRs) to this same value. (NSEC/NSEC3 RRs) to this same value.
Section 5 of [RFC2308] also states that a negative cache entry TTL is Section 5 of [RFC2308] also states that a negative cache entry TTL is
taken from the minimum of the SOA.MINIMUM field and SOA's TTL. This taken from the minimum of the SOA.MINIMUM field and SOA's TTL. This
can be less than the TTL of an NSEC or NSEC3 record, since their TTL can be less than the TTL of an NSEC or NSEC3 record, since their TTL
is equal to the SOA.MINIMUM field (see [RFC4035]section 2.3 and is equal to the SOA.MINIMUM field (see [RFC4035]section 2.3 and
[RFC5155] section 3.) [RFC5155] section 3.)
A resolver that supports aggressive use of NSEC and NSEC3 SHOULD A resolver that supports aggressive use of NSEC and NSEC3 SHOULD
reduce the TTL of NSEC and NSEC3 records to match the SOA.MINIMUM reduce the TTL of NSEC and NSEC3 records to match the SOA.MINIMUM
field in the authority section of a negative response, if SOA.MINIMUM field in the authority section of a negative response, if SOA.MINIMUM
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security problem. security problem.
It is also suggested to limit the maximum TTL value of NSEC / NSEC3 It is also suggested to limit the maximum TTL value of NSEC / NSEC3
resource records in the negative cache to, for example, 10800 seconds resource records in the negative cache to, for example, 10800 seconds
(3hrs), to mitigate this issue. (3hrs), to mitigate this issue.
Although the TTL of NSEC/NSEC3 records is typically fairly short Although the TTL of NSEC/NSEC3 records is typically fairly short
(minutes or hours), their RRSIG expiration time can be much further (minutes or hours), their RRSIG expiration time can be much further
in the future (weeks). An attacker who is able to successfully spoof in the future (weeks). An attacker who is able to successfully spoof
responses might poison a cache with old NSEC/NSEC3 records. If the responses might poison a cache with old NSEC/NSEC3 records. If the
resolver is NOT making aggressive use of NSEC/NSEC3, the attacker has resolver is not making aggressive use of NSEC/NSEC3, the attacker has
to repeat the attack for every query. If the resolver IS making to repeat the attack for every query. If the resolver is making
aggressive use of NSEC/NSEC3, one successful attack would be able to aggressive use of NSEC/NSEC3, one successful attack would be able to
suppress many queries for new names, up to the negative TTL. suppress many queries for new names, up to the negative TTL.
10. Implementation Status 10. Implementation Status
[ Editor note: RFC Editor, please remove this entire section. [ Editor note: RFC Editor, please remove this entire section.
RFC6982 says: "Since this information is necessarily time dependent, RFC6982 says: "Since this information is necessarily time dependent,
it is inappropriate for inclusion in a published RFC." ] it is inappropriate for inclusion in a published RFC." ]
Unbound currently implements aggressive negative caching, as does Unbound currently implements aggressive negative caching, as does
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and the Unbound developers. and the Unbound developers.
Thanks to Mark Andrews for providing the helpful notes for Thanks to Mark Andrews for providing the helpful notes for
implementors provided in Appendix B. implementors provided in Appendix B.
The authors would like to specifically thank Stephane Bortzmeyer (for The authors would like to specifically thank Stephane Bortzmeyer (for
standing next to and helping edit), Ralph Dolmans, Tony Finch, Tatuya standing next to and helping edit), Ralph Dolmans, Tony Finch, Tatuya
JINMEI for extensive review and comments, and also Mark Andrews, JINMEI for extensive review and comments, and also Mark Andrews,
Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob Harold, Shumon Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob Harold, Shumon
Huque, John Levine, Pieter Lexis, Matthijs Mekking (who even sent Huque, John Levine, Pieter Lexis, Matthijs Mekking (who even sent
pull requests!) and Ondrej Sury. Mark Andrews also provided the pull requests!) and Ondrej Sury.
helpful notes for implementors (https://www.ietf.org/mail-
archive/web/dnsop/current/msg18332.html) which we made into
Appendix B.
11.1. Change History 11.1. Change History
RFC Editor: Please remove this section prior to publication. RFC Editor: Please remove this section prior to publication.
-08 to -09:
o Made RFC5074 Informative (after discussions with chairs.
o Addressed SecDir comments.
o Addressed OpsDir comments.
-06 to -08:
o Largely editorial, but please see the diffs (editors forgot to
update change log when editing, backfilling change log.)
o Changed "replacement" text to be "DNSSEC enabled validating
resolvers SHOULD use wildcards ..." to align with text in doc.
o "A resolver that supports aggressive use of NSEC and NSEC3 SHOULD"
(should -> SHOULD) - to align with rest of text.
-05 to -06: -05 to -06:
o Moved some dangling text around - when the examples were added o Moved some dangling text around - when the examples were added
some text added in the wrong place. some text added in the wrong place.
o There were some bits which mentioned "negative" in the title. o There were some bits which mentioned "negative" in the title.
o We had the cut-and-paste of what changed in 4035 twice. o We had the cut-and-paste of what changed in 4035 twice.
o Clarified that this also allows NODATA responses to be o Clarified that this also allows NODATA responses to be
skipping to change at page 13, line 36 skipping to change at page 13, line 41
o Added "Partial implementation" o Added "Partial implementation"
o Section 4,5,6 reorganized for better representation o Section 4,5,6 reorganized for better representation
o Added NODATA answer in Section 4 o Added NODATA answer in Section 4
o Trivial updates o Trivial updates
o Updated pseudo code o Updated pseudo code
11.2. new section
12. References 12. References
12.1. Normative References 12.1. 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, Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
DOI 10.17487/RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
<http://www.rfc-editor.org/info/rfc2308>. <http://www.rfc-editor.org/info/rfc2308>.
[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, DOI 10.17487/RFC4035, March 2005, Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
<http://www.rfc-editor.org/info/rfc4035>. <http://www.rfc-editor.org/info/rfc4035>.
[RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name
System", RFC 4592, DOI 10.17487/RFC4592, July 2006, System", RFC 4592, DOI 10.17487/RFC4592, July 2006,
<http://www.rfc-editor.org/info/rfc4592>. <http://www.rfc-editor.org/info/rfc4592>.
[RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
DOI 10.17487/RFC5074, November 2007,
<http://www.rfc-editor.org/info/rfc5074>.
[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
<http://www.rfc-editor.org/info/rfc5155>. <http://www.rfc-editor.org/info/rfc5155>.
[RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of [RFC7129] Gieben, R. and W. Mekking, "Authenticated Denial of
Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129, Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129,
February 2014, <http://www.rfc-editor.org/info/rfc7129>. February 2014, <http://www.rfc-editor.org/info/rfc7129>.
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
skipping to change at page 14, line 39 skipping to change at page 14, line 39
2015, <http://www.rfc-editor.org/info/rfc7719>. 2015, <http://www.rfc-editor.org/info/rfc7719>.
12.2. Informative References 12.2. Informative References
[I-D.vixie-dnsext-resimprove] [I-D.vixie-dnsext-resimprove]
Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS Vixie, P., Joffe, R., and F. Neves, "Improvements to DNS
Resolvers for Resiliency, Robustness, and Responsiveness", Resolvers for Resiliency, Robustness, and Responsiveness",
draft-vixie-dnsext-resimprove-00 (work in progress), June draft-vixie-dnsext-resimprove-00 (work in progress), June
2010. 2010.
[RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
DOI 10.17487/RFC5074, November 2007,
<http://www.rfc-editor.org/info/rfc5074>.
[RFC8020] Bortzmeyer, S. and S. Huque, "NXDOMAIN: There Really Is [RFC8020] Bortzmeyer, S. and S. Huque, "NXDOMAIN: There Really Is
Nothing Underneath", RFC 8020, DOI 10.17487/RFC8020, Nothing Underneath", RFC 8020, DOI 10.17487/RFC8020,
November 2016, <http://www.rfc-editor.org/info/rfc8020>. November 2016, <http://www.rfc-editor.org/info/rfc8020>.
[root-servers.org] [root-servers.org]
IANA, "Root Server Technical Operations Assn", IANA, "Root Server Technical Operations Assn",
<http://www.root-servers.org/>. <http://www.root-servers.org/>.
Appendix A. Detailed implementation notes Appendix A. Detailed implementation notes
 End of changes. 18 change blocks. 
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