< draft-ietf-dnsop-nsec-aggressiveuse-01.txt   draft-ietf-dnsop-nsec-aggressiveuse-02.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: February 3, 2017 W. Kumari Expires: March 17, 2017 W. Kumari
Google Google
August 02, 2016 September 13, 2016
Aggressive use of NSEC/NSEC3 Aggressive use of NSEC/NSEC3
draft-ietf-dnsop-nsec-aggressiveuse-01 draft-ietf-dnsop-nsec-aggressiveuse-02
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 generate negative answers within a of NSEC/NSEC3 resource records to generate negative answers within a
range. This increases resilience to DoS attacks, increases range. This increases performance / decreases latency, decreases
performance / decreases latency, decreases resource utilization on resource utilization on both authoritative and recursive servers, and
both authoritative and recursive servers, and also increases privacy. also increases privacy. It may also help increase resilience to
certain DoS attacks in some circumstances.
This document updates RFC4035 by allowing resolvers to generate This document updates RFC4035 by allowing resolvers to generate
negative answers based upon NSEC/NSEC3 records. negative answers based upon NSEC/NSEC3 records.
[ Ed note: Text inside square brackets ([]) is additional background [ Ed note: Text inside square brackets ([]) is additional background
information, answers to frequently asked questions, general musings, information, answers to frequently asked questions, general musings,
etc. They will be removed before publication.This document is being etc. They will be removed before publication.This document is being
collaborated on in Github at: https://github.com/wkumari/draft-ietf- collaborated on in Github at: https://github.com/wkumari/draft-ietf-
dnsop-nsec-aggressiveuse. The most recent version of the document, dnsop-nsec-aggressiveuse. The most recent version of the document,
open issues, etc should all be available here. The authors open issues, etc should all be available here. The authors
skipping to change at page 2, line 12 skipping to change at page 2, line 15
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 February 3, 2017. This Internet-Draft will expire on March 17, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 5 5. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Aggressive Negative Caching . . . . . . . . . . . . . . . 5 5.1. Aggressive Negative Caching . . . . . . . . . . . . . . . 5
5.2. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. NSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.3. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. NSEC3 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.4. Wildcard . . . . . . . . . . . . . . . . . . . . . . . . 6 5.4. Wildcard . . . . . . . . . . . . . . . . . . . . . . . . 6
5.5. Consideration on TTL . . . . . . . . . . . . . . . . . . 7 5.5. Consideration on TTL . . . . . . . . . . . . . . . . . . 7
6. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 7 6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Update to RFC 4035 . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 8 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 10. Implementation Status . . . . . . . . . . . . . . . . . . . . 9
11. Change History . . . . . . . . . . . . . . . . . . . . . . . 8 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . . . 9 12. Change History . . . . . . . . . . . . . . . . . . . . . . . 9
11.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . . . 9 12.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 . . . 11
11.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . . . 9 12.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 . . . 11
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 12.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 . . . 11
12.1. Normative References . . . . . . . . . . . . . . . . . . 10 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
12.2. Informative References . . . . . . . . . . . . . . . . . 10 13.1. Normative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Detailed implementation idea . . . . . . . . . . . . 11 13.2. Informative References . . . . . . . . . . . . . . . . . 12
Appendix B. Side effect: mitigation of random subdomain attacks 11 Appendix A. Detailed implementation notes . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
A DNS negative cache currently exists, and is used to cache the fact A DNS negative cache currently exists, and is used to cache the fact
that a name does not exist. This method of negative caching requires that a name does not exist. This method of negative caching requires
exact matching; this leads to unnecessary additional lookups, which exact matching; this leads to unnecessary additional lookups,
have negative implications for DoS survivability, increases latency, increases latency, leads to extra resource utilization on both
leads to extra resource utilization on both authoritative and authoritative and recursive servers, and decreases privacy by leaking
recursive servers, and decreases privacy by leaking queries. queries.
This document updates RFC 4035 to allow recursive resolvers to use This document updates RFC 4035 to allow recursive resolvers to use
NSEC/NSEC3 resource records to aggressively cache negative answers. NSEC/NSEC3 resource records to aggressively cache negative answers.
This would allow such resolvers to respond with NXDOMAIN immediately This would allow such resolvers to respond with NXDOMAIN immediately
if the name in question falls into a range expressed by a NSEC/NSEC3 if the name in question falls into a range expressed by a NSEC/NSEC3
resource record already in the cache. resource record already in the cache.
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.
skipping to change at page 3, line 39 skipping to change at page 3, line 41
Search on NXDOMAIN" and [I-D.ietf-dnsop-nxdomain-cut] proposed Search on NXDOMAIN" and [I-D.ietf-dnsop-nxdomain-cut] proposed
another approach to use NXDOMAIN information effectively. another approach to use NXDOMAIN information effectively.
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]. In this document we are using the terms
"recursive resolver" or "recursive server" as a more readable
alternative to the more formal[RFC7719] "full-service resolver"
The key words "Closest Encloser" and "Source of Synthesis" in this The key words "Closest Encloser" and "Source of Synthesis" in this
document are to be interpreted as described in[RFC4592]. document are to be interpreted as described in[RFC4592].
"Closest Encloser" is also defined in NSEC3 [RFC5155], as is "Next "Closest Encloser" is also defined in NSEC3 [RFC5155], as is "Next
closer name". closer name".
3. Problem Statement 3. Problem Statement
The current DNS negative cache caches negative (non-existent) The current DNS negative cache caches negative (non-existent)
skipping to change at page 5, line 32 skipping to change at page 5, line 37
wildcards or NSEC RRs to generate positive and negative responses wildcards or NSEC RRs to generate positive and negative responses
(respectively) until the TTL or signatures on the records in question (respectively) until the TTL or signatures on the records in question
expire. However, it seems prudent for resolvers to avoid blocking expire. However, it seems prudent for resolvers to avoid blocking
new authoritative data or synthesizing new data on their own. new authoritative data or synthesizing new data on their own.
Resolvers that follow this recommendation will have a more consistent Resolvers that follow this recommendation will have a more consistent
view of the namespace". view of the namespace".
This document relaxes this this restriction, as follows: This document relaxes this this restriction, as follows:
+--------------------------------------------------------------+ +--------------------------------------------------------------+
| Once the records are validated, DNSSEC enabled full-service | | Once the records are validated, DNSSEC enabled validating |
| resolvers MAY use NSEC/NSEC3 resource records to generate | | resolvers MAY use NSEC/NSEC3 resource records to generate |
| negative responses until their effective TTLs or signatures | | negative responses until their effective TTLs or signatures |
| for those records expire. | | for those records expire. |
+--------------------------------------------------------------+ +--------------------------------------------------------------+
If the full-service resolver's cache has sufficient information to If the validating resolver's cache has sufficient information to
validate the query, the full-service resolver MAY use NSEC/NSEC3/ validate the query, the resolver SHOULD use NSEC/NSEC3/wildcard
wildcard records aggressively. Otherwise, the full-service resolver records aggressively. Otherwise, it MUST fall back to send the query
MUST fall back to send the query to the authoritative DNS servers. to the authoritative DNS servers.
If the query name has the matching NSEC/NSEC3 RR proving the If the query name has the matching NSEC/NSEC3 RR proving the
information requested does not exist, the full-service resolver may information requested does not exist, the resolver may respond with a
respond with a NODATA (empty) answer. NODATA (empty) answer.
5.2. NSEC 5.2. NSEC
If a full-service resolver implementation supports aggressive Implementations SHOULD enable aggressive use of NSEC by default.
negative caching, then it SHOULD support aggressive use of NSEC and Implementations SHOULD provide a configuration switch to disable
enable it by default. It SHOULD provide a configuration switch to aggressive use of NSEC and allow it to be enabled or disabled per
disable aggressive use of NSEC and allow it to be enabled or disabled domain.
for specific zones.
The validating resolver needs to check the existence of an NSEC RR The validating resolver needs to check the existence of an NSEC RR
matching/covering the source of synthesis and an NSEC RR covering the matching/covering the source of synthesis and an NSEC RR covering the
query name. query name.
If the full-service resolver's cache contains an NSEC RR covering the If the validating resolver's cache contains an NSEC RR covering the
source of synthesis and the covering NSEC RR of the query name, the source of synthesis and the covering NSEC RR of the query name, the
full-service resolver may respond with NXDOMAIN error immediately. resolver may respond with NXDOMAIN error immediately.
5.3. NSEC3 5.3. NSEC3
NSEC3 aggressive negative caching is more difficult. If the zone is NSEC3 aggressive negative caching is more difficult. If the zone is
signed with NSEC3, the validating resolver needs to check the signed with NSEC3, the validating resolver needs to check the
existence of non-terminals and wildcards which derive from query existence of non-terminals and wildcards which derive from query
names. names.
If the full-service resolver's cache contains an NSEC3 RR matching If the validating resolver's cache contains an NSEC3 RR matching the
the closest encloser, an NSEC3 RR covering the next closer name, and closest encloser, an NSEC3 RR covering the next closer name, and an
an NSEC3 RR covering the source of synthesis, it is possible for the NSEC3 RR covering the source of synthesis, it is possible for the
full-service resolver to respond with NXDOMAIN immediately. resolver to respond with NXDOMAIN immediately.
If a covering NSEC3 RR has Opt-Out flag, the covering NSEC3 RR does If a covering NSEC3 RR has Opt-Out flag, the covering NSEC3 RR does
not prove the non-existence of the domain name and the aggressive not prove the non-existence of the domain name and the aggressive
negative caching is not possible for the domain name. negative caching is not possible for the domain name.
A full-service resolver implementation MAY support aggressive use of A validating resolver implementation MAY support aggressive use of
NSEC3. If it does aggressive use of NSEC3, it SHOULD provide a NSEC3. If it does aggressive use of NSEC3, it SHOULD provide a
configuration switch to disable aggressive use of NSEC3 and allow it configuration switch to disable aggressive use of NSEC3 and allow it
to be enabled or disabled for specific zones. to be enabled or disabled for specific zones.
5.4. Wildcard 5.4. Wildcard
The last paragraph of RFC 4035 Section 4.5 discusses aggressive use The last paragraph of RFC 4035 Section 4.5 discusses aggressive use
of a cached deduced wildcard (as well as aggressive use of NSEC) and of a cached deduced wildcard (as well as aggressive use of NSEC) and
recommends that it is not relied upon. recommends that it is not relied upon.
Just like the case for the aggressive use of NSEC discussed in this Just like the case for the aggressive use of NSEC discussed in this
draft, we revise this recommendation. As long as the full-service draft, we revise this recommendation. As long as the resolver knows
resolver knows a name would not exist without the wildcard match, it a name would not exist without the wildcard match, it can answer a
can answer a query for that name using the cached deduced wildcard, query for that name using the cached deduced wildcard, and it may be
and it may be justified for performance and other benefits. (Note justified for performance and other benefits.
that, so far, this is orthogonal to "when aggressive use (of NSEC) is
enabled"). Such aggressive use of cached deduced wildcard can be employed
independently from aggressive use of NSEC. But, it will be more
effective when both are enabled since the resolver can determine the
name subject to wildcard would not otherwise exist more efficiently.
Furthermore, when aggressive use of NSEC is enabled, the aggressive Furthermore, when aggressive use of NSEC is enabled, the aggressive
use of cached deduced wildcard will be more effective. use of cached deduced wildcard will be more effective.
A full-service resolver implementation MAY support aggressive use of An implementation MAY support aggressive use of wildcards. It SHOULD
wildcards. It SHOULD provide a configuration switch to disable provide a configuration switch to disable aggressive use of
aggressive use of wildcards. wildcards.
5.5. Consideration on TTL 5.5. 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. Section 5 of RFC 2308 states that the information is effective. Section 5 of RFC 2308 states that the
maximum number of negative cache TTL value is 3 hours (10800). It is maximum number of negative cache TTL value is 3 hours (10800). It is
RECOMMENDED that full-service resolvers limit the maximum effective RECOMMENDED that resolvers limit the maximum effective TTL value of
TTL value of negative responses (NSEC/NSEC3 RRs) to this same value. negative responses (NSEC/NSEC3 RRs) to this same value.
6. Update to RFC 4035 6. Benefits
The techniques described in this document provide a number of
benefits, including (in no specific order):
Latency By answering directly from cache, recursive resolvers can
immediately inform clients that the name they are looking for does
not exist, improving the user experience.
Decreased recursive server load By answering negative queries from
the cache, recursive servers avoid having send a query and wait
for a response. In addition to decreasing the bandwidth used, it
also means that the server does not need to allocate and maintain
state, thereby decreasing memory and CPU load.
Decreased authorative server load Because recursive servers can
answer (negative) queries without asking the authoritative server,
the authoritative servers receive less queries. This decreases
the authoritative server bandwidth, queries per second and CPU
utilization.
The scale of the benefit depends upon multiple factors, including the
query distribution. For example, currently around 65% of queries to
Root Name servers result in NXDOMAIN responses; this technique will
eliminate a sizable quantity of these.
[ Editor note: There has been some discussion on if this document
should discuss this attack and mitigation. The authors think that
this is useful / important, but some participants feel that it
oversells the DoS mitigation benefit. Please let us know if the
below is helpful. Also, the below description is not as clear as it
could be - it's been tricky to balance readability, correctness and
conciseness. Text gratefully accepted... ]
The technique described in this document may also mitigate so-called
"random QNAME attacks", in which attackers send many queries for
random sub-domains to recursive resolvers. As the recursive server
will not have the answers cached it has to ask the authoritative
servers for each random query, leading to a DoS on the authoritative
(and often recursive) servers. Aggressive NSEC may help mitigate
these attacks by allowing the recursive to answer directly from cache
for any random queries which fall within already requested ranges.
The effectiveness of this depends upon a number of factors, including
if the attacker is making his queries through recursive resolvers
(e.g to hide his source), the number of entries in the zone, the TTL,
if the zone is using NSEC, if the attacker is setting the CD bit,
etc. In the ideal case, authoritative servers under attack will need
to answer somewhere between number_of_entries_in_zone queries and 2 *
number_of_entries_in_zone queries from each recursive server. This
is because there are as many "holes" between labels as there are
labels in a zone. If the random query falls in range for which
recursive server does not have an NSEC record cached, it will send a
query to the authoritative server, and so it will send approximately
the same number of queries as there are "holes" between entries. If
the random queries happen to be for names which exist in the zone,
the recursive will send those as well.
7. Update to RFC 4035
Section 4.5 of [RFC4035] shows that "In theory, a resolver could use Section 4.5 of [RFC4035] shows that "In theory, a resolver could use
wildcards or NSEC RRs to generate positive and negative responses wildcards or NSEC RRs to generate positive and negative responses
(respectively) until the TTL or signatures on the records in question (respectively) until the TTL or signatures on the records in question
expire. However, it seems prudent for resolvers to avoid blocking expire. However, it seems prudent for resolvers to avoid blocking
new authoritative data or synthesizing new data on their own. new authoritative data or synthesizing new data on their own.
Resolvers that follow this recommendation will have a more consistent Resolvers that follow this recommendation will have a more consistent
view of the namespace". view of the namespace".
(If approved, ) The paragraph is updated as follows: The paragraph is updated as follows:
+--------------------------------------------------------------+ +--------------------------------------------------------------+
| Once the records are validated, DNSSEC enabled full-service | | Once the records are validated, DNSSEC enabled recursive |
| resolvers MAY use wildcards and NSEC/NSEC3 resource records | | resolvers MAY use wildcards and NSEC/NSEC3 resource records |
| to generate (positive and) negative responses until their | | to generate (positive and) negative responses until their |
| effective TTLs or signatures for those records expire. | | effective TTLs or signatures for those records expire. |
+--------------------------------------------------------------+ +--------------------------------------------------------------+
7. IANA Considerations 8. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
8. Security Considerations 9. Security Considerations
Newly registered resource records may not be used immediately. Newly registered resource records may not be used immediately.
However, choosing suitable TTL value and negative cache TTL value However, choosing suitable TTL value and negative cache TTL value
(SOA MINIMUM field) will mitigate the delay concern, and it is not a (SOA MINIMUM field) will mitigate the delay concern, and it is not a
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. Implementations which comply with (3hrs), to mitigate this issue. Implementations which comply with
this proposal are recommended to have a configurable maximum value of this proposal are recommended to have a configurable maximum value of
NSEC RRs in the negative cache. NSEC RRs in the negative cache.
Aggressive use of NSEC / NSEC3 resource records without DNSSEC Aggressive use of NSEC / NSEC3 resource records without DNSSEC
validation may cause security problems. It is highly recommended to validation may cause security problems. It is highly recommended to
apply DNSSEC validation. apply DNSSEC validation.
9. Implementation Status 10. Implementation Status
Unbound has aggressive negative caching code in its DLV validator. Unbound supports aggressive negative caching.
The author implemented NSEC aggressive caching using Unbound and its
DLV validator code.
10. Acknowledgments 11. Acknowledgments
The authors gratefully acknowledge DLV [RFC5074] author Samuel Weiler The authors gratefully acknowledge DLV [RFC5074] author Samuel Weiler
and Unbound developers. Valuable comments were provided by Alexander and the Unbound developers.
Dupuy, Olafur Gudmundsson, Pieter Lexis, Bob Harold, Tatuya JINMEI,
Shumon Huque, Mark Andrews, Casey Deccio, Bob Harold, Stephane
Bortzmeyer and Matthijs Mekking.
11. Change History The authors would like to specifically thank Tatuya JINMEI for
extensive review and comments, and also Mark Andrews, Stephane
Bortzmeyer, Casey Deccio, Alexander Dupuy, Olafur Gudmundsson, Bob
Harold, Shumon Huque, Pieter Lexis and Matthijs Mekking.
12. Change History
RFC Editor: Please remove this section prior to publication. RFC Editor: Please remove this section prior to publication.
-01 to -02:
o Added Section 6 - Benefits (as suggested by Jinmei).
o Removed Appendix B (Jinmei)
o Replaced "full-service" with "validating" (where applicable)
o Integrated other comments from Jinmei from https://www.ietf.org/
mail-archive/web/dnsop/current/msg17875.html
o Integrated comment from co-authors, including re-adding parts of
Appendix B, terminology, typos.
o Tried to explain under what conditions this may actually mitigate
attacks.
-00 to -01: -00 to -01:
o Comments from DNSOP meeting in Berlin. o Comments from DNSOP meeting in Berlin.
o Changed intended status to Standards Track (updates RFC 4035) o Changed intended status to Standards Track (updates RFC 4035)
o Added a section "Updates to RFC 4035" o Added a section "Updates to RFC 4035"
o Some language clarification / typo / cleanup o Some language clarification / typo / cleanup
o Cleaned up the TTL section a bit. o Cleaned up the TTL section a bit.
o Removed Effects section, Additional proposal section, and pseudo o Removed Effects section, Additional proposal section, and pseudo
code. code.
o Moved "mitigaton of random subdomain attacks" to Appendix. o Moved "mitigation of random subdomain attacks" to Appendix.
From draft-fujiwara-dnsop-nsec-aggressiveuse-03 -> draft-ietf-dnsop- From draft-fujiwara-dnsop-nsec-aggressiveuse-03 -> draft-ietf-dnsop-
nsec-aggressiveuse nsec-aggressiveuse
o Document adopted by DNSOP WG. o Document adopted by DNSOP WG.
o Adoption comments o Adoption comments
o Changed main purpose to performance o Changed main purpose to performance
o Use NSEC3/Wildcard keywords o Use NSEC3/Wildcard keywords
o Improved wordings (from good comments) o Improved wordings (from good comments)
o Simplified pseudo code for NSEC3 o Simplified pseudo code for NSEC3
o Added Warren as co-author. o Added Warren as co-author.
o Reworded much of the problem statement o Reworded much of the problem statement
o Reworked examples to better explain the problem / solution. o Reworked examples to better explain the problem / solution.
11.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01 12.1. Version draft-fujiwara-dnsop-nsec-aggressiveuse-01
o Added reference to DLV [RFC5074] and imported some sentences. o Added reference to DLV [RFC5074] and imported some sentences.
o Added Aggressive Negative Caching Flag idea. o Added Aggressive Negative Caching Flag idea.
o Added detailed algorithms. o Added detailed algorithms.
11.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02 12.2. Version draft-fujiwara-dnsop-nsec-aggressiveuse-02
o Added reference to [I-D.vixie-dnsext-resimprove] o Added reference to [I-D.vixie-dnsext-resimprove]
o Added considerations for the CD bit o Added considerations for the CD bit
o Updated detailed algorithms. o Updated detailed algorithms.
o Moved Aggressive Negative Caching Flag idea into Additional o Moved Aggressive Negative Caching Flag idea into Additional
Proposals Proposals
11.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03 12.3. Version draft-fujiwara-dnsop-nsec-aggressiveuse-03
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
12. References 13. References
12.1. Normative References
13.1. 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, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, 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>.
skipping to change at page 10, line 37 skipping to change at page 12, line 27
[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>.
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <http://www.rfc-editor.org/info/rfc7719>. 2015, <http://www.rfc-editor.org/info/rfc7719>.
12.2. Informative References 13.2. Informative References
[I-D.ietf-dnsop-nxdomain-cut] [I-D.ietf-dnsop-nxdomain-cut]
Bortzmeyer, S. and S. Huque, "NXDOMAIN really means there Bortzmeyer, S. and S. Huque, "NXDOMAIN really means there
is nothing underneath", draft-ietf-dnsop-nxdomain-cut-03 is nothing underneath", draft-ietf-dnsop-nxdomain-cut-03
(work in progress), May 2016. (work in progress), May 2016.
[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.
Appendix A. Detailed implementation idea Appendix A. Detailed implementation notes
o Previously, cached negative responses were indexed by QNAME, o Previously, cached negative responses were indexed by QNAME,
QCLASS, QTYPE, and the setting of the CD bit (see RFC 4035, QCLASS, QTYPE, and the setting of the CD bit (see RFC 4035,
Section 4.7), and only queries matching the index key would be Section 4.7), and only queries matching the index key would be
answered from the cache. With aggressive negative caching, the answered from the cache. With aggressive negative caching, the
validator, in addition to checking to see if the answer is in its validator, in addition to checking to see if the answer is in its
cache before sending a query, checks to see whether any cached and cache before sending a query, checks to see whether any cached and
validated NSEC record denies the existence of the sought validated NSEC record denies the existence of the sought
record(s). Using aggressive negative caching, a validator will record(s). Using aggressive negative caching, a validator will
not make queries for any name covered by a cached and validated not make queries for any name covered by a cached and validated
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on the incoming query. (Imported from Section 6 of [RFC5074]). on the incoming query. (Imported from Section 6 of [RFC5074]).
o Implementing aggressive negative caching suggests that a validator o Implementing aggressive negative caching suggests that a validator
will need to build an ordered data structure of NSEC and NSEC3 will need to build an ordered data structure of NSEC and NSEC3
records for each signer domain name of NSEC / NSEC3 records in records for each signer domain name of NSEC / NSEC3 records in
order to efficiently find covering NSEC / NSEC3 records. Call the order to efficiently find covering NSEC / NSEC3 records. Call the
table as NSEC_TABLE. (Imported from Section 6.1 of [RFC5074] and table as NSEC_TABLE. (Imported from Section 6.1 of [RFC5074] and
expanded.) expanded.)
o The aggressive negative caching may be inserted at the cache o The aggressive negative caching may be inserted at the cache
lookup part of the full-service resolvers. lookup part of the recursive resolvers.
o If errors happen in aggressive negative caching algorithm, o If errors happen in aggressive negative caching algorithm,
resolvers MUST fall back to resolve the query as usual. "Resolve resolvers MUST fall back to resolve the query as usual. "Resolve
the query as usual" means that the full-resolver resolve the query the query as usual" means that the resolver must process the query
in Recursive-mode as if the full-service resolver does not as though it does not implement aggressive negative caching.
implement aggressive negative caching.
Appendix B. Side effect: mitigation of random subdomain attacks
Random sub-domain attacks (referred to as "Water Torture" attacks or
NXDomain attacks) send many queries for non-existent information to
full-service resolvers. Their query names consist of random prefixes
and a target domain name. The negative cache does not work well, and
thus targeted full-service resolvers end up sending queries to
authoritative DNS servers of the target domain name.
The aggressive negative caching is one of possible countermeasures to
random subdomain attacks. If the full-service resolver supports
aggressive negative caching and the target domain name is signed with
NSEC/NSEC3 (without Opt-Out), the aggressive negative caching is one
of countermeasures of random subdomain attacks.
However, attackers can set the CD bit to their attack queries. The
CD bit disables signature validation and the aggressive negative
caching will be of no use.
Authors' Addresses Authors' Addresses
Kazunori Fujiwara Kazunori Fujiwara
Japan Registry Services Co., Ltd. Japan Registry Services Co., Ltd.
Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda
Chiyoda-ku, Tokyo 101-0065 Chiyoda-ku, Tokyo 101-0065
Japan Japan
Phone: +81 3 5215 8451 Phone: +81 3 5215 8451
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