Internet DRAFT - draft-dickson-dnsop-glueless
draft-dickson-dnsop-glueless
Network Working Group B. Dickson
Internet-Draft GoDaddy
Intended status: Informational 22 September 2021
Expires: 26 March 2022
Operating a Glueless DNS Authority Server
draft-dickson-dnsop-glueless-02
Abstract
This Internet Draft proposes a method for protecting authority
servers against MITM and poisoning attacks, using a domain naming
strategy to not require glue A/AAAA records and use of DNSSEC.
This technique assumes the use of validating resolvers.
MITM and poisoning attacks should only be effective/possible against
unsigned domains.
However, until all domains are signed, this guidance is relevant, in
that it can limit the attack surface of unsigned domains.
This guidance should be combined with [I-D.dickson-dnsop-ds-hack]
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 March 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
Dickson Expires 26 March 2022 [Page 1]
Internet-Draft Glueless DNS September 2021
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Proposed Solutions . . . . . . . . . . . . . . . . . . . . . 3
5. Terminology: . . . . . . . . . . . . . . . . . . . . . . . . 3
6. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8
10. Informative References . . . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
DNS Security Extensions (DNSSEC) are additions to the DNS protocol
which provide data integrity and authenticity protections, but do not
provide privacy.
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Background
Use of DNSSEC requires upgrades to software for authorative servers,
resolvers, and optionally clients, in order to benefit from these
protections. It also requires that DNS operators actually sign their
zones and secure the corresponding delegations at the parent.
When a given domain is unsigned or not securely delegated, those
protections to the zone contents are not available.
Dickson Expires 26 March 2022 [Page 2]
Internet-Draft Glueless DNS September 2021
Any such insecure domain is trivially able to be altered by an on-
path attacker.
An off-path attacker is limited to use of cache poisoning attacks.
However, some class of cache poisoning attacks target unsigned
delegation data. These records consist of the necessary NS records,
and when necessary, "glue" records for IP addresses corresponding to
these NS records.
The impact to successful cache poisoning of delegation records is
that the attacker may substitute their own name servers for the
legitimate name server. In other words, the attacker is able to
promote itself to being effectively on-path, and trivially modify
unsigned domain results.
4. Proposed Solutions
This work does not propose any protocol changes. It provides
guidance on strategies and techniques for name server naming.
There are two kinds of delegation records that require protection
against off-path attackers, for unsigned domains.
For protecting NS records used in delegations, there is a new
proposal for use of a new DS record. See [I-D.dickson-dnsop-ds-hack]
for details.
The present draft addresses the "glue" records, by recommending
methods to make them mostly unnecessary. If there is no delegation
glue data, an attacker cannot poison that data. The resolver cache
would contain only authoritative address records associated with NS
names. Authoritative data cannot be pre-empted by such poisoning
attacks, since those are only able to replace less trusted glue
records.
Additional recommendations are made to reduce the chances for errors
caused by DNS operators when changing delegation records, by avoiding
re-use of name server names which require glue address records.
5. Terminology:
The following terms are used to disambiguate domains and server
names:
* Registered domain - end-user (registrant) domain
Dickson Expires 26 March 2022 [Page 3]
Internet-Draft Glueless DNS September 2021
- In the parent zone, the registered domain is the left-hand side
of the NS record
* Registered domain name server - the name of the name server
serving the registered domain
- In the parent zone, the registered domain name server is the
right-hand side of the NS record
6. Recommendations
The following practice is RECOMMENDED for unsigned domains:
* Do not use in-bailiwick registered domain name servers for
unsigned domains.
* Instead, use out-of-zone names for the registered domain name
servers of unsigned domains.
Example:
Dickson Expires 26 March 2022 [Page 4]
Internet-Draft Glueless DNS September 2021
Do NOT do the following (delegations requiring glue):
$ORIGIN example.
// Records in example TLD, with relative names
unsigned-domain NS ns1.unsigned-domain
unsigned-domain NS ns2.unsigned-domain
// glue
// "strictly necessary glue"
// always required for successful resolution
ns1.unsigned-domain A (IP address)
ns1.unsigned-domain AAAA (IP address)
ns2.unsigned-domain A (IP address)
ns2.unsigned-domain AAAA (IP address)
Instead, do the following (glueless delegations):
$ORIGIN example.
// Records in example TLD, with relative names
// This is the minimum "glueless" set-up
// NS target name is not a "registered" host
// NS target is not used for glue for any domains
unsigned-domain NS ns1.nameserver-signed-domain
unsigned-domain NS ns2.nameserver-signed-domain
//
// Delegation to signed domain containing name server names
// (This domain serves the address records of name servers
// such as the glueless example above)
nameserver-signed-domain NS ns1.nameserver-signed-domain
nameserver-signed-domain NS ns2.nameserver-signed-domain
nameserver-signed-domain DS (DS record data)
// However, this domain needs to be resolvable, and needs glue
// glue records for this delegation
ns1.nameserver-signed-domain A (IP address)
ns1.nameserver-signed-domain A (IP address)
ns2.nameserver-signed-domain AAAA (IP address)
ns2.nameserver-signed-domain AAAA (IP address)
The following practice is RECOMMENDED:
* For any name server domain (domain containing addresses and
related data for name servers used by registered domains), use
distinct dedicated name servers for the domain itself
- I.e. avoid sharing name servers between the name server domain
and any registered domains
* Consider making the name server domain itself fully glueless, with
an out-of-zone name server (using a tertiary domain)
Dickson Expires 26 March 2022 [Page 5]
Internet-Draft Glueless DNS September 2021
* For this tertiary domain, also consider using separating the in-
bailiwick name servers, from the names used for serving the name
server domain
- Limiting the in-bailiwick NS names ensures that changes and
updates to the tertiary domain don't affect any other domains
- Depending on parent zone policy (e.g. TLD database policy),
renaming or renumbering name servers may affect delegations
using them (NS entries)
- A single domain with non-reused NS names guarantees side
effects of this sort are not possible
* Overhead of tertiary domain and not re-using (or sharing) name
server names in the tertiary domain:
- Additional lookups are required on the initial reference to get
the addresses of name servers for the main glueless domain
- Subsequent (new) queries for the IP addresses of glueless name
servers only require single queries
Example:
Entries in the example TLD
$ORIGIN example.
//
// Same unsigned domain uses the same name servers
// However, the name server is in its own glueless domain
unsigned-registrant-domain NS ns1.signed-nameserver-domain
unsigned-registrant-domain NS ns2.signed-nameserver-domain
//
signed-nameserver-domain NS ns1.tertiary-domain
signed-nameserver-domain NS ns2.tertiary-domain
signed-nameserver-domain DS (DS record data)
//
tertiary-domain NS special-ns1.tertiary-domain
tertiary-domain NS special-ns2.tertiary-domain
tertiary-domain DS (DS record data)
// glue for special-ns1 and -2
// special-ns1 and -2 are used only for/by tertiary-domain
special-ns1.tertiary-domain A (IP address)
special-ns1.tertiary-domain AAAA (IP address)
special-ns2.tertiary-domain A (IP address)
special-ns2.tertiary-domain AAAA (IP address)
Zone file for signed-nameserver-domain.example:
Dickson Expires 26 March 2022 [Page 6]
Internet-Draft Glueless DNS September 2021
$ORIGIN signed-nameserver-domain.example.
@ SOA (soa record data)
// glueless NS are used
@ NS ns1.tertiary-domain
@ NS ns2.tertiary-domain
// actual glueless address records for "real" name server names
ns1 A (IP address)
ns1 AAAA (IP address)
ns2 A (IP address)
ns2 AAAA (IP address)
// etc etc etc
Zone file for tertiary-domain.example:
$ORIGIN tertiary-domain.example.
@ SOA (soa record data)
//
// This is the only non-glueless NS in use
// (NB: matches glue address records in the parent)
@ NS special-ns1
@ NS special-ns2
special-ns1 A (IP address)
special-ns1 AAAA (IP address)
special-ns2 A (IP address)
special-ns2 AAAA (IP address)
//
// actual address records for "real" name server name
// (only used by signed-nameserver-domain)
// (These match glue records in the parent zone)
ns1 A (IP address)
ns1 AAAA (IP address)
ns2 A (IP address)
ns2 AAAA (IP address)
7. Security Considerations
This guidance is useful in preventing off-path attackers from
poisoning DNS cache entries necessary for delegations.
However, an on-path attacker is still able to manipulate DNS
responses sent over UDP or unencrypted TCP.
This guidance is not a substitute for use of DNSSEC for DNS domains.
The only mechanism that can protect against on-path attackers is
cryptographic protection DNSSEC signing of domains is both necessary
and sufficient to provide data integrity protection.
Dickson Expires 26 March 2022 [Page 7]
Internet-Draft Glueless DNS September 2021
Use of an encrypted transport is may be effective at preventing MITM
attacks (i.e. DNS over TLS from resolver to authoritative server,
aka ADoT), but does not provide provable data integrity.
Encrypted transport may be used in combination with DNSSEC signed
zones and glueless name server domains.
Encrypted transport does not incrementally improve the data integrity
or protection against MITM. DNSSEC is sufficient alone for this
purpose. However, encrypted transport does add privacy protection
against passive observers.
8. IANA Considerations
This document has no IANA actions.
9. Normative References
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10. Informative References
[I-D.dickson-dnsop-ds-hack]
Dickson, B., "DS Algorithms for Securing NS and Glue",
Work in Progress, Internet-Draft, draft-dickson-dnsop-ds-
hack-00, 11 August 2021,
<https://datatracker.ietf.org/doc/html/draft-dickson-
dnsop-ds-hack-00>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Appendix A. Acknowledgments
Thanks to everyone who helped create the tools that let everyone use
Markdown to create Internet Drafts, and the RFC Editor for xml2rfc.
Thanks to Dan York for his Tutorial on using Markdown (specifically
mmark) for writing IETF drafts.
Thanks to YOUR NAME HERE for contributions, reviews, etc.
Author's Address
Dickson Expires 26 March 2022 [Page 8]
Internet-Draft Glueless DNS September 2021
Brian Dickson
GoDaddy
Email: brian.peter.dickson@gmail.com
Dickson Expires 26 March 2022 [Page 9]
