Internet DRAFT - draft-wisser-dnssec-automation
draft-wisser-dnssec-automation
Domain Name System Operations (dnsop) U. Wisser
Internet-Draft The Swedish Internet Foundation
Intended status: Standards Track S. Huque
Expires: 7 September 2022 Salesforce
6 March 2022
DNSSEC automation
draft-wisser-dnssec-automation-03
Abstract
This document describes an algorithm and a protocol to automate
DNSSEC Multi-Signer [RFC8901] "Multi-Signer DNSSEC Models" setup,
operations and decomissioning. Using Model 2 of the Multi-Signer
specification, where each operator has their own distinct KSK and ZSK
sets (or CSK sets), [RFC8078] "Managing DS Records from the Parent
via CDS/CDNSKEY" and [RFC7477] "Child-to-Parent Synchronization in
DNS" to accomplish this.
Status of This Memo
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This Internet-Draft will expire on 7 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Out-Of-Scope . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Maintaining a Multi-Signer group . . . . . . . . . . . . 4
2.2. Secure Nameserver Operator Transition . . . . . . . . . . 4
3. Automation Models . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Centralized . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Decentralized . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Capabilities . . . . . . . . . . . . . . . . . . . . . . 5
4. Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Prerequisites . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5
4.2.1. DS Waiting Time . . . . . . . . . . . . . . . . . . . 5
4.2.2. DNSKEY Waiting Time . . . . . . . . . . . . . . . . . 6
4.2.3. NS Waiting Time . . . . . . . . . . . . . . . . . . . 6
4.3. Setting up a new Multi-Signer group . . . . . . . . . . . 6
4.4. A Signer joins the Multi-Signer group . . . . . . . . . . 6
4.5. A signer leaves the Multi-Signer group . . . . . . . . . 7
4.6. A Signer performs a ZSK rollover . . . . . . . . . . . . 7
4.7. A Signer performs a CSK or KSK rollover . . . . . . . . . 8
4.8. Algorithm rollover for the whole Multi-Signer group. . . 8
5. Signers with different algorithms in one Multi-Signer
group . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 10
9. Security Considerations . . . . . . . . . . . . . . . . . . . 10
10. Normative References . . . . . . . . . . . . . . . . . . . . 10
11. Informative References . . . . . . . . . . . . . . . . . . . 11
Appendix A. Change History . . . . . . . . . . . . . . . . . . . 11
A.1. Change from 01 to 02 . . . . . . . . . . . . . . . . . . 11
A.2. Change from 02 to 03 . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
[RFC8901] describes the necessary steps and API for a Multi-Signer
DNSSEC configuration. In this document we will combine [RFC8901]
with [RFC8078] and [RFC7477] to define an automatable algorithm for
setting up, operating and decomissioning of a Multi-Signer DNSSEC
configuration.
One of the special cases of Multi-Signer DNSSEC is the secure change
of DNS operator. Using Multi-Signer Model 2 the secure change of DNS
operator can be accomplished.
1.1. Out-Of-Scope
In order for any Multi-Signer group to give consistent answers across
all nameservers, the data contents of the zone also have to be
synchronized (in addition to infrastructure records like NS, DNSKEY,
CDS etc). This content synchronization is out-of-scope for this
document (although there are a number of methods that can be used,
such as making the the same updates to each operator using their
respective APIs, using zone transfer in conjunction with "inline
signing" at each operator, etc.)
1.2. Notation
Short definitions of expressions used in this document
*Signer*
An entity signing a zone
*Multi-Signer Group*
A group of signers that sign the same zone
*Controller*
An entity controlling the multi-signer group. Used in the
decentralized model.
1.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Use Cases
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2.1. Maintaining a Multi-Signer group
As described in [RFC8901] a Multi-Signer DNSSEC configuration has
some challenges that can be overcome with the right infrastructure
and following a number of steps for setup and operation.
In this document we describe, except for the initial trust, how the
steps in the Multi-Signer DNSSEC setup can be automated.
2.2. Secure Nameserver Operator Transition
Changing the nameserver operator of a DNSSEC signed zone can be
challenging. Currently the most common method is temporarily "going
insecure". This is poor for security, and for users relying on the
security of the zone. Furthermore, when DNSSEC is being used for
application security functions like DANE [RFC6698], it is critical
that the DNSSEC chain of trust remain unbroken during the transfer.
Multi-Signer DNSSEC Model 2 provides a mechanism for transitioning
from one nameserver operator to another without "going insecure". A
new operator joins the current operator in a temporary Multi-Signer
group. Once that is accomplished and stable the old operator leaves
the Multi-Signer group completing the transition.
3. Automation Models
Automation of the necessary steps can be categorized into two main
models, centralized and decentralized. Both have pros and cons, and
a zone operator should carefully choose the model that works best.
3.1. Centralized
In a centralized model the zone operator will run controller that
executes all steps necessary and controls all signers.
A centralized controller needs to have authorized access to all
signers. This can be achieved in a variety of different ways. For
example will many service providers offer access through a REST API.
Another possibility is access through Dynamic Update [RFC2136] with
TSIG authentication.
3.2. Decentralized
In the decentralized models all signers will communicate with each
other and execute the necessary steps on their instance only. For
this signers need a specialized protocol to communicate configuration
details that are not part of the zone data.
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3.3. Capabilities
In order for any of the models to work the signer must support the
following capabilities.
1. Add DNSKEY records (without the private key)
2. Remove (previously added) DNSKEY record(s)
3. Add CDS and CDNSKEY records for keys not in the DNSKEY set
4. Remove (previously added) CDS and CDNSKEY records
5. Add CSYNC record
6. Remove CSYNC record
4. Algorithms
4.1. Prerequisites
Each Signer to be added, including the initial Signer, must meet the
following prerequisites before joining the Multi-Signer Group
1. A working setup of the zone, including DNSSEC signing.
2. Uses the same algorithm for DNSSEC signing as the Multi-Signer
group uses or will use.
3. Signer or controller must be able to differentiate between its
own keys and keys from others signers
4. Signer controller must be able to differentiate between NS
records that are updated by itself and NS records that receive
updates from other signers.
5. The domain must be covered by a CDS/CDNSKEY scanner and a CSYNC
scanner. Otherwise updates to the parent zone have to be made
manually.
4.2. Definitions
4.2.1. DS Waiting Time
Once the parent has picked up and published the new DS record set,
the any further changes MUST to be delayed until the new DS set has
propagated.
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The minimum DS Waiting Time is the TTL of the DS RRset.
4.2.2. DNSKEY Waiting Time
Once the DNSKEY sets of all signers are updated, any further changes
MUST to be delayed until the new DNSKEY set has propagated.
The minimum DNSKEY Waiting Time is the maximum of all DNSKEYS TTL
values from all signers plus the time it takes to publish the zone on
all secondaries.
4.2.3. NS Waiting Time
Once the parent has picked up and published the new NS record set,
any further changes MUST be delayed until the new NS set has
propagated.
The minimum NS Waiting Time is the maximum of the TTL value of the NS
set in the parent zone and all NS sets from all signers.
4.3. Setting up a new Multi-Signer group
The zone is already authoritatively served by one DNS operator and is
DNSSEC signed. For full automation both the KSK and ZSK or CSK must
be online.
This would be a special case, a Multi-Signer group with only one
signer.
4.4. A Signer joins the Multi-Signer group
1. Confirm that the incoming Signer meets the prerequisites.
2. Establish a trust mechanism between the Multi-Signer group and
the Signer.
3. Add ZSK for each signer to all other Signers.
4. Calculate CDS/CDNSKEY Records for all KSKs/CSKs represented in
the Multi-Signer group.
5. Configure all Signers with the compiled CDS/CDNSKEY RRSET.
6. Wait for Parent to publish the combined DS RRset.
7. Remove CDS/CDNSKEY Records from all Signers. (optional)
8. Wait maximum of DS-Wait-Time and DNSKEY-Wait-Time
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9. Compile NS RRSET including all NS records from all Signers.
10. Configure all Signers with the compiled NS RRSET.
11. Compare NS RRSET of the Signers to the Parent, if there is a
difference publish CSYNC record with NS and A and AAAA bit set
on all signers.
12. Wait for Parent to publish NS.
13. Remove CSYNC record from all signers. (optional)
4.5. A signer leaves the Multi-Signer group
1. Remove exiting Signer's NS records from remaining Signers
2. Compare NS RRSET of the Signers to the Parent, if there is a
difference publish CSYNC record with NS and A and AAAA bit set
on remaining signers.
3. Wait for Parent to publish NS RRSET.
4. Remove CSYNC record from all signers. (optional)
5. Wait NS-Wait-Time
6. Stop the exiting Signer from answering queries.
7. Calculate CDS/CDNSKEY Records for KSKs/CSKs published by the
remaining Signers.
8. Configure remaining Signers with the compiled CDS/CDNSKEY RRSET.
9. Remove ZSK of the exiting Signer from remaining Signers.
10. Wait for Parent to publish the updated DS RRset.
11. Remove CDS/CDNSKEY set from all signers. (Optional)
4.6. A Signer performs a ZSK rollover
1. The signer introduces the new ZSK in its own DNSKEY RRset.
2. Update all signers with the new ZSK.
3. Wait DNSKEY-Wait-Time
4. Signer can start using the new ZSK.
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5. When the old ZSK is not used in any signatures by the signer, the
signer can remove the old ZSK from its DNSKEY RRset.
6. Remove ZSK from DNSKEY RRset of all signers.
4.7. A Signer performs a CSK or KSK rollover
1. Signer publishes new CSK / KSK in its own DNSKEY RRset.
2. In case of CSK, add CSK to DNSKEY set of all other Signers.
3. Signer signs DNSKEY RRset with old and new CSK / KSK.
4. Calculate new CDS/CDNSKEY RRset and publish on all signers.
5. Wait for parent to pickup and publish new DS RR set.
6. Wait DS-Wait-Time + DNSKEY-Wait-Time
7. Signer removes old CSK/KSK from its DNSKEY RR set. And removes
all signatures done with this key.
8. In case of CSK, remove old CSK from DNSKEY set of all other
signers.
9. Calculate new CDS/CDNSKEY RRset and publish on all signers.
10. Wait for parent to pickup and publish new DS RR set.
11. Remove CDS/CDNSKEY RR sets from all signers.
4.8. Algorithm rollover for the whole Multi-Signer group.
1. All signers publish KSK and ZSK or CSK using the new algorithm.
2. All signers sign all zone data with the new keys.
3. Wait until all signers have signed all data with the new key(s).
4. Add new ZSK of each signer to all other Signers.
5. Calculate new CDS/CDNSKEY RRset and publish on all signers.
6. Wait for parent to pickup and publish new DS RR set.
7. Wait DS-Wait-Time + DNSKEY-Wait-Time
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8. Removes all keys and signatures which are using the old
algorithm.
9. Calculate new CDS/CDNSKEY RRset and publish on all signers.
10. Wait for parent to pickup and publish new DS RR set.
11. Remove CDS/CDNSKEY RR sets from all signers.
5. Signers with different algorithms in one Multi-Signer group
Section 2.2 of [RFC4035] states that a signed zone MUST include a
DNSKEY for each algorithm present in the zone's DS RRset and expected
trust anchors for the zone.
A setup where different signers use different key algorithms
therefore violates [RFC4035].
According to Section 5.11 of [RFC6840] validators SHOULD NOT insist
that all algorithms signaled in the DS RRset work, and they MUST NOT
insist that all algorithms signaled in the DNSKEY RRset work.
So a Multi-Signer setup where different signers use different key
algorithms should still validate.
This could be an acceptable risk in a situation where going insecure
is not desirable or impossible and name servers have to be changed
between operators which only support distinct set of key algorithms.
We have to consider the following scenarios
*Validator supports both algorithms*
Validation should be stable through all stages of the multi-signer
algorithms.
*Validator supports none of the algorithms*
The validator will treat the zone as unsigned. Resolution should
work through all stages of the multi-signer algorithms.
*Validator supports only one of the algorithms*
The validator will not be able to validate the DNSKEY RR set or any
data from one of the signers. So in some cases the validator will
consider the zone bogus and reply with a SERVFAIL response code.
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The later scenario can be mitigated, but not fully eliminated, by
selecting two well supported algorithms.
6. Acknowledgements
The authors would like to thank the following for their review of
this work and their valuable comments: Steve Crocker, Eric Osterweil,
Roger Murray, Jonas Andersson, Peter Thomassen.
7. IANA Considerations
8. Implementation Status
One implementation of a centralized controller which supports updates
through Dynamic DNS or REST API's of several vendors has been
implemented by the Swedish Internet Foundation.
The code can be found as part of the Multi-Signer project on Github
https://github.com/DNSSEC-Provisioning/multi-signer-controller
9. Security Considerations
Every step of the multi-signer algorithms has to be carefully
executed at the right time and date. Any failure could resolve in
the loss of resolution for the domain.
Independently of the chosen model, it is crucial that only authorized
entities will be able to change the zone data. Some providers or
software installation allow to make more specific configuration on
the allowed changes. All extra steps to allows as little access to
change zone data as possible should be taken.
If used correctly the multi-signer algorithm will strengthen the DNS
security by avoiding "going insecure" at any stage of the domain life
cycle.
10. Normative References
[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>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>.
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[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
<https://www.rfc-editor.org/info/rfc4035>.
[RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
DOI 10.17487/RFC6840, February 2013,
<https://www.rfc-editor.org/info/rfc6840>.
[RFC7477] Hardaker, W., "Child-to-Parent Synchronization in DNS",
RFC 7477, DOI 10.17487/RFC7477, March 2015,
<https://www.rfc-editor.org/info/rfc7477>.
[RFC8078] Gudmundsson, O. and P. Wouters, "Managing DS Records from
the Parent via CDS/CDNSKEY", RFC 8078,
DOI 10.17487/RFC8078, March 2017,
<https://www.rfc-editor.org/info/rfc8078>.
11. Informative References
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
2012, <https://www.rfc-editor.org/info/rfc6698>.
[RFC8901] Huque, S., Aras, P., Dickinson, J., Vcelak, J., and D.
Blacka, "Multi-Signer DNSSEC Models", RFC 8901,
DOI 10.17487/RFC8901, September 2020,
<https://www.rfc-editor.org/info/rfc8901>.
Appendix A. Change History
A.1. Change from 01 to 02
1. Trying to fix wording to be more precise
2. Added algorithm for ZSK rollover
3. Added algorithm for KSK rollover
4. Added algorithm for algorithm rollover
A.2. Change from 02 to 03
1. Fix sequnce of steps in the joining procedure
2. Excplicit handling of CSK cases in CSK/ KSK rollover
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Authors' Addresses
Ulrich Wisser
The Swedish Internet Foundation
Box 92073
SE-12007 Stockholm
Sweden
Email: ulrich@wisser.se
URI: https://www.internetstiftelsen.se
Shumon Huque
Salesforce
415 Mission Street, 3rd Floor
San Francisco, CA 94105
United States of America
Email: shuque@gmail.com
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