draft-ietf-dnsext-trustupdate-timers-01.txt   draft-ietf-dnsext-trustupdate-timers-02.txt 
Network Working Group M. StJohns Network Working Group M. StJohns
Internet-Draft Nominum, Inc. Internet-Draft Nominum, Inc.
Expires: February 16, 2006 August 15, 2005 Expires: July 14, 2006 January 10, 2006
Automated Updates of DNSSEC Trust Anchors Automated Updates of DNSSEC Trust Anchors
draft-ietf-dnsext-trustupdate-timers-01 draft-ietf-dnsext-trustupdate-timers-02
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
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have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
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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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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on February 16, 2006. This Internet-Draft will expire on July 14, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document describes a means for automated, authenticated and This document describes a means for automated, authenticated and
authorized updating of DNSSEC "trust anchors". The method provides authorized updating of DNSSEC "trust anchors". The method provides
protection against single key compromise of a key in the trust point protection against single key compromise of a key in the trust point
key set. Based on the trust established by the presence of a current key set. Based on the trust established by the presence of a current
anchor, other anchors may be added at the same place in the anchor, other anchors may be added at the same place in the
hierarchy, and, ultimately, supplant the existing anchor. hierarchy, and, ultimately, supplant the existing anchor.
This mechanism, if adopted, will require changes to resolver This mechanism, if adopted, will require changes to resolver
management behavior (but not resolver resolution behavior), and the management behavior (but not resolver resolution behavior), and the
addition of a single flag bit to the DNSKEY record. addition of a single flag bit to the DNSKEY record.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Compliance Nomenclature . . . . . . . . . . . . . . . . . 3 1.1. Compliance Nomenclature . . . . . . . . . . . . . . . . . 3
1.2 Changes since -00 . . . . . . . . . . . . . . . . . . . . 3 1.2. Changes since -00 . . . . . . . . . . . . . . . . . . . . 3
2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4 2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
2.1 Revocation . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Revocation . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Add Hold-Down . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Add Hold-Down . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Remove Hold-down . . . . . . . . . . . . . . . . . . . . . 5 2.3. Remove Hold-down . . . . . . . . . . . . . . . . . . . . . 5
2.4 Active Refresh . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Active Refresh . . . . . . . . . . . . . . . . . . . . . . 6
2.5 Resolver Parameters . . . . . . . . . . . . . . . . . . . 6 2.5. Resolver Parameters . . . . . . . . . . . . . . . . . . . 6
2.5.1 Add Hold-Down Time . . . . . . . . . . . . . . . . . . 6 2.5.1. Add Hold-Down Time . . . . . . . . . . . . . . . . . . 6
2.5.2 Remove Hold-Down Time . . . . . . . . . . . . . . . . 6 2.5.2. Remove Hold-Down Time . . . . . . . . . . . . . . . . 6
2.5.3 Minimum Trust Anchors per Trust Point . . . . . . . . 6 2.5.3. Minimum Trust Anchors per Trust Point . . . . . . . . 6
3. Changes to DNSKEY RDATA Wire Format . . . . . . . . . . . . . 6 3. Changes to DNSKEY RDATA Wire Format . . . . . . . . . . . . . 6
4. State Table . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. State Table . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Events . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Events . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2 States . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. States . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Trust Point Deletion . . . . . . . . . . . . . . . . . . . 8
5. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Adding A Trust Anchor . . . . . . . . . . . . . . . . . . 8 5.1. Adding A Trust Anchor . . . . . . . . . . . . . . . . . . 9
5.2 Deleting a Trust Anchor . . . . . . . . . . . . . . . . . 9 5.2. Deleting a Trust Anchor . . . . . . . . . . . . . . . . . 9
5.3 Key Roll-Over . . . . . . . . . . . . . . . . . . . . . . 9 5.3. Key Roll-Over . . . . . . . . . . . . . . . . . . . . . . 9
5.4 Active Key Compromised . . . . . . . . . . . . . . . . . . 9 5.4. Active Key Compromised . . . . . . . . . . . . . . . . . . 9
5.5 Stand-by Key Compromised . . . . . . . . . . . . . . . . . 9 5.5. Stand-by Key Compromised . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6.1 Key Ownership vs Acceptance Policy . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6.2 Multiple Key Compromise . . . . . . . . . . . . . . . . . 10 7.1. Key Ownership vs Acceptance Policy . . . . . . . . . . . . 10
6.3 Dynamic Updates . . . . . . . . . . . . . . . . . . . . . 10 7.2. Multiple Key Compromise . . . . . . . . . . . . . . . . . 10
7. Normative References . . . . . . . . . . . . . . . . . . . . . 10 7.3. Dynamic Updates . . . . . . . . . . . . . . . . . . . . . 11
Editorial Comments . . . . . . . . . . . . . . . . . . . . . . 11 8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11 Editorial Comments . . . . . . . . . . . . . . . . . . . . . . . .
Intellectual Property and Copyright Statements . . . . . . . . 12 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
1. Introduction 1. Introduction
As part of the reality of fielding DNSSEC (Domain Name System As part of the reality of fielding DNSSEC (Domain Name System
Security Extensions) [RFC2535] [RFC4033][RFC4034][RFC4035], the Security Extensions) [RFC2535] [RFC4033][RFC4034][RFC4035], the
community has come to the realization that there will not be one community has come to the realization that there will not be one
signed name space, but rather islands of signed name space each signed name space, but rather islands of signed name space each
originating from specific points (i.e. 'trust points') in the DNS originating from specific points (i.e. 'trust points') in the DNS
tree. Each of those islands will be identified by the trust point tree. Each of those islands will be identified by the trust point
name, and validated by at least one associated public key. For the name, and validated by at least one associated public key. For the
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rollover more viable. rollover more viable.
As mentioned above, this document describes a mechanism whereby a As mentioned above, this document describes a mechanism whereby a
resolver can update the trust anchors for a given trust point, mainly resolver can update the trust anchors for a given trust point, mainly
without human intervention at the resolver. There are some corner without human intervention at the resolver. There are some corner
cases discussed (e.g. multiple key compromise) that may require cases discussed (e.g. multiple key compromise) that may require
manual intervention, but they should be few and far between. This manual intervention, but they should be few and far between. This
document DOES NOT discuss the general problem of the initial document DOES NOT discuss the general problem of the initial
configuration of trust anchors for the resolver. configuration of trust anchors for the resolver.
1.1 Compliance Nomenclature 1.1. Compliance Nomenclature
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 BCP 14, [RFC2119]. document are to be interpreted as described in BCP 14, [RFC2119].
1.2 Changes since -00 1.2. Changes since -00
Added the concept of timer triggered resolver queries to refresh the Added the concept of timer triggered resolver queries to refresh the
resolvers view of the trust anchor key RRSet. resolvers view of the trust anchor key RRSet.
Re-submitted expired draft as -01. Updated DNSSEC RFC References. Re-submitted expired draft as -01. Updated DNSSEC RFC References.
Draft -02. Added the IANA Considerations section. Added text to
describe what happens if all trust anchors at a trust point are
deleted.
2. Theory of Operation 2. Theory of Operation
The general concept of this mechanism is that existing trust anchors The general concept of this mechanism is that existing trust anchors
can be used to authenticate new trust anchors at the same point in can be used to authenticate new trust anchors at the same point in
the DNS hierarchy. When a new SEP key is added to a trust point the DNS hierarchy. When a new SEP key is added to a trust point
DNSKEY RRSet, and when that RRSet is validated by an existing trust DNSKEY RRSet, and when that RRSet is validated by an existing trust
anchor, then the new key can be added to the set of trust anchors. anchor, then the new key can be added to the set of trust anchors.
There are some issues with this approach which need to be mitigated. There are some issues with this approach which need to be mitigated.
For example, a compromise of one of the existing keys could allow an For example, a compromise of one of the existing keys could allow an
attacker to add their own 'valid' data. This implies a need for a attacker to add their own 'valid' data. This implies a need for a
method to revoke an existing key regardless of whether or not that method to revoke an existing key regardless of whether or not that
key is compromised. As another example assuming a single key key is compromised. As another example assuming a single key
compromise, an attacker could add a new key and revoke all the other compromise, an attacker could add a new key and revoke all the other
old keys. old keys.
2.1 Revocation 2.1. Revocation
Assume two trust anchor keys A and B. Assume that B has been Assume two trust anchor keys A and B. Assume that B has been
compromised. Without a specific revocation bit, B could invalidate A compromised. Without a specific revocation bit, B could invalidate A
simply by sending out a signed trust point key set which didn't simply by sending out a signed trust point key set which didn't
contain A. To fix this, we add a mechanism which requires knowledge contain A. To fix this, we add a mechanism which requires knowledge
of the private key of a DNSKEY to revoke that DNSKEY. of the private key of a DNSKEY to revoke that DNSKEY.
A key is considered revoked when the resolver sees the key in a self- A key is considered revoked when the resolver sees the key in a self-
signed RRSet and the key has the REVOKE bit set to '1'. Once the signed RRSet and the key has the REVOKE bit (see Section 6 below) set
resolver sees the REVOKE bit, it MUST NOT use this key as a trust to '1'. Once the resolver sees the REVOKE bit, it MUST NOT use this
anchor or for any other purposes except validating the RRSIG over the key as a trust anchor or for any other purposes except validating the
DNSKEY RRSet specifically for the purpose of validating the RRSIG over the DNSKEY RRSet specifically for the purpose of
revocation. Unlike the 'Add' operation below, revocation is validating the revocation. Unlike the 'Add' operation below,
immediate and permanent upon receipt of a valid revocation at the revocation is immediate and permanent upon receipt of a valid
resolver. revocation at the resolver.
N.B. A DNSKEY with the REVOKE bit set has a different fingerprint N.B. A DNSKEY with the REVOKE bit set has a different fingerprint
than one without the bit set. This affects the matching of a DNSKEY than one without the bit set. This affects the matching of a DNSKEY
to DS records in the parent, or the fingerprint stored at a resolver to DS records in the parent, or the fingerprint stored at a resolver
used to configure a trust point. [msj3] used to configure a trust point. [msj3]
In the given example, the attacker could revoke B because it has In the given example, the attacker could revoke B because it has
knowledge of B's private key, but could not revoke A. knowledge of B's private key, but could not revoke A.
2.2 Add Hold-Down 2.2. Add Hold-Down
Assume two trust point keys A and B. Assume that B has been Assume two trust point keys A and B. Assume that B has been
compromised. An attacker could generate and add a new trust anchor compromised. An attacker could generate and add a new trust anchor
key - C (by adding C to the DNSKEY RRSet and signing it with B), and key - C (by adding C to the DNSKEY RRSet and signing it with B), and
then invalidate the compromised key. This would result in the both then invalidate the compromised key. This would result in the both
the attacker and owner being able to sign data in the zone and have the attacker and owner being able to sign data in the zone and have
it accepted as valid by resolvers. it accepted as valid by resolvers.
To mitigate, but not completely solve, this problem, we add a hold- To mitigate, but not completely solve, this problem, we add a hold-
down time to the addition of the trust anchor. When the resolver down time to the addition of the trust anchor. When the resolver
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both A and B. both A and B.
The reason this does not completely solve the problem has to do with The reason this does not completely solve the problem has to do with
the distributed nature of DNS. The resolver only knows what it sees. the distributed nature of DNS. The resolver only knows what it sees.
A determined attacker who holds one compromised key could keep a A determined attacker who holds one compromised key could keep a
single resolver from realizing that key had been compromised by single resolver from realizing that key had been compromised by
intercepting 'real' data from the originating zone and substituting intercepting 'real' data from the originating zone and substituting
their own (e.g. using the example, signed only by B). This is no their own (e.g. using the example, signed only by B). This is no
worse than the current situation assuming a compromised key. worse than the current situation assuming a compromised key.
2.3 Remove Hold-down 2.3. Remove Hold-down
A new key which has been seen by the resolver, but hasn't reached A new key which has been seen by the resolver, but hasn't reached
it's add hold-down time, MAY be removed from the DNSKEY RRSet by the it's add hold-down time, MAY be removed from the DNSKEY RRSet by the
zone owner. If the resolver sees a validated DNSKEY RRSet without zone owner. If the resolver sees a validated DNSKEY RRSet without
this key, it waits for the remove hold-down time and then, if the key this key, it waits for the remove hold-down time and then, if the key
hasn't reappeared, SHOULD discard any information about the key. hasn't reappeared, SHOULD discard any information about the key.
2.4 Active Refresh 2.4. Active Refresh
A resolver which has been configured for automatic update of keys A resolver which has been configured for automatic update of keys
from a particular trust point MUST query that trust point (e.g. do a from a particular trust point MUST query that trust point (e.g. do a
lookup for the DNSKEY RRSet and related RRSIG records) no less often lookup for the DNSKEY RRSet and related RRSIG records) no less often
than the lesser of 15 days or half the original TTL for the DNSKEY than the lesser of 15 days or half the original TTL for the DNSKEY
RRSet or half the RRSIG expiration interval. The expiration interval RRSet or half the RRSIG expiration interval. The expiration interval
is the amount of time from when the RRSIG was last retrieved until is the amount of time from when the RRSIG was last retrieved until
the expiration time in the RRSIG. the expiration time in the RRSIG.
If the query fails, the resolver MUST repeat the query until If the query fails, the resolver MUST repeat the query until
satisfied no more often than once an hour and no less often than the satisfied no more often than once an hour and no less often than the
lesser of 1 day or 10% of the original TTL or 10% of the original lesser of 1 day or 10% of the original TTL or 10% of the original
expiration interval. expiration interval.
2.5 Resolver Parameters 2.5. Resolver Parameters
2.5.1 Add Hold-Down Time 2.5.1. Add Hold-Down Time
The add hold-down time is 30 days or the expiration time of the TTL The add hold-down time is 30 days or the expiration time of the TTL
of the first trust point DNSKEY RRSet which contained the key, of the first trust point DNSKEY RRSet which contained the key,
whichever is greater. This ensures that at least two validated whichever is greater. This ensures that at least two validated
DNSKEY RRSets which contain the new key MUST be seen by the resolver DNSKEY RRSets which contain the new key MUST be seen by the resolver
prior to the key's acceptance. prior to the key's acceptance.
2.5.2 Remove Hold-Down Time 2.5.2. Remove Hold-Down Time
The remove hold-down time is 30 days. The remove hold-down time is 30 days.
2.5.3 Minimum Trust Anchors per Trust Point 2.5.3. Minimum Trust Anchors per Trust Point
A compliant resolver MUST be able to manage at least five SEP keys A compliant resolver MUST be able to manage at least five SEP keys
per trust point. per trust point.
3. Changes to DNSKEY RDATA Wire Format 3. Changes to DNSKEY RDATA Wire Format
Bit n [msj2] of the DNSKEY Flags field is designated as the 'REVOKE' Bit n [msj2] of the DNSKEY Flags field is designated as the 'REVOKE'
flag. If this bit is set to '1', AND the resolver sees an flag. If this bit is set to '1', AND the resolver sees an
RRSIG(DNSKEY) signed by the associated key, then the resolver MUST RRSIG(DNSKEY) signed by the associated key, then the resolver MUST
consider this key permanently invalid for all purposes except for consider this key permanently invalid for all purposes except for
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---------------------------------------------------------- ----------------------------------------------------------
Valid | | | |KeyRem |Revbit | | Valid | | | |KeyRem |Revbit | |
---------------------------------------------------------- ----------------------------------------------------------
Missing | | |KeyPres| |Revbit | | Missing | | |KeyPres| |Revbit | |
---------------------------------------------------------- ----------------------------------------------------------
Revoked | | | | | |RemTime| Revoked | | | | | |RemTime|
---------------------------------------------------------- ----------------------------------------------------------
Removed | | | | | | | Removed | | | | | | |
---------------------------------------------------------- ----------------------------------------------------------
4.1 Events 4.1. Events
NewKey The resolver sees a valid DNSKEY RRSet with a new SEP key. NewKey The resolver sees a valid DNSKEY RRSet with a new SEP key.
That key will become a new trust anchor for the named trust point That key will become a new trust anchor for the named trust point
after its been present in the RRSet for at least 'add time'. after its been present in the RRSet for at least 'add time'.
KeyPres The key has returned to the valid DNSKEY RRSet. KeyPres The key has returned to the valid DNSKEY RRSet.
KeyRem The resolver sees a valid DNSKEY RRSet that does not contain KeyRem The resolver sees a valid DNSKEY RRSet that does not contain
this key. this key.
AddTime The key has been in every valid DNSKEY RRSet seen for at AddTime The key has been in every valid DNSKEY RRSet seen for at
least the 'add time'. least the 'add time'.
RemTime A revoked key has been missing from the trust point DNSKEY RemTime A revoked key has been missing from the trust point DNSKEY
RRSet for sufficient time to be removed from the trust set. RRSet for sufficient time to be removed from the trust set.
RevBit The key has appeared in the trust anchor DNSKEY RRSet with its RevBit The key has appeared in the trust anchor DNSKEY RRSet with its
"REVOKED" bit set, and there is an RRSig over the DNSKEY RRSet "REVOKED" bit set, and there is an RRSig over the DNSKEY RRSet
signed by this key. signed by this key.
4.2 States 4.2. States
Start The key doesn't yet exist as a trust anchor at the resolver. Start The key doesn't yet exist as a trust anchor at the resolver.
It may or may not exist at the zone server, but hasn't yet been It may or may not exist at the zone server, but hasn't yet been
seen at the resolver. seen at the resolver.
AddPend The key has been seen at the resolver, has its 'SEP' bit set, AddPend The key has been seen at the resolver, has its 'SEP' bit set,
and has been included in a validated DNSKEY RRSet. There is a and has been included in a validated DNSKEY RRSet. There is a
hold-down time for the key before it can be used as a trust hold-down time for the key before it can be used as a trust
anchor. anchor.
Valid The key has been seen at the resolver and has been included in Valid The key has been seen at the resolver and has been included in
all validated DNSKEY RRSets from the time it was first seen up all validated DNSKEY RRSets from the time it was first seen up
through the hold-down time. It is now valid for verifying RRSets through the hold-down time. It is now valid for verifying RRSets
that arrive after the hold down time. Clarification: The DNSKEY that arrive after the hold down time. Clarification: The DNSKEY
RRSet does not need to be continuously present at the resolver RRSet does not need to be continuously present at the resolver
(e.g. its TTL might expire). If the RRSet is seen, and is (e.g. its TTL might expire). If the RRSet is seen, and is
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through the hold-down time. It is now valid for verifying RRSets through the hold-down time. It is now valid for verifying RRSets
that arrive after the hold down time. Clarification: The DNSKEY that arrive after the hold down time. Clarification: The DNSKEY
RRSet does not need to be continuously present at the resolver RRSet does not need to be continuously present at the resolver
(e.g. its TTL might expire). If the RRSet is seen, and is (e.g. its TTL might expire). If the RRSet is seen, and is
validated (i.e. verifies against an existing trust anchor), this validated (i.e. verifies against an existing trust anchor), this
key MUST be in the RRSet otherwise a 'KeyRem' event is triggered. key MUST be in the RRSet otherwise a 'KeyRem' event is triggered.
Missing This is an abnormal state. The key remains as a valid trust Missing This is an abnormal state. The key remains as a valid trust
point key, but was not seen at the resolver in the last validated point key, but was not seen at the resolver in the last validated
DNSKEY RRSet. This is an abnormal state because the zone operator DNSKEY RRSet. This is an abnormal state because the zone operator
should be using the REVOKE bit prior to removal. [Discussion should be using the REVOKE bit prior to removal. [Discussion
item: Should a missing key be considered revoked after some item: Should a missing key be considered revoked after some period
period of time?] of time?]
Revoked This is the state a key moves to once the resolver sees an Revoked This is the state a key moves to once the resolver sees an
RRSIG(DNSKEY) signed by this key where that DNSKEY RRSet contains RRSIG(DNSKEY) signed by this key where that DNSKEY RRSet contains
this key with its REVOKE bit set to '1'. Once in this state, this this key with its REVOKE bit set to '1'. Once in this state, this
key MUST permanently be considered invalid as a trust anchor. key MUST permanently be considered invalid as a trust anchor.
Removed After a fairly long hold-down time, information about this Removed After a fairly long hold-down time, information about this
key may be purged from the resolver. A key in the removed state key may be purged from the resolver. A key in the removed state
MUST NOT be considered a valid trust anchor. MUST NOT be considered a valid trust anchor.
4.3. Trust Point Deletion
A trust point which has all of its trust anchors revoked is
considered deleted and is treated as if the trust point was never
configured. If there are no superior trust points, data at and below
the deleted trust point are considered insecure. If there there ARE
superior trust points, data at and below the deleted trust point are
evaluated with respect to the superior trust point.
5. Scenarios 5. Scenarios
The suggested model for operation is to have one active key and one The suggested model for operation is to have one active key and one
stand-by key at each trust point. The active key will be used to stand-by key at each trust point. The active key will be used to
sign the DNSKEY RRSet. The stand-by key will not normally sign this sign the DNSKEY RRSet. The stand-by key will not normally sign this
RRSet, but the resolver will accept it as a trust anchor if/when it RRSet, but the resolver will accept it as a trust anchor if/when it
sees the signature on the trust point DNSKEY RRSet. sees the signature on the trust point DNSKEY RRSet.
Since the stand-by key is not in active signing use, the associated Since the stand-by key is not in active signing use, the associated
private key may (and SHOULD) be provided with additional protections private key may (and SHOULD) be provided with additional protections
not normally available to a key that must be used frequently. E.g. not normally available to a key that must be used frequently. E.g.
locked in a safe, split among many parties, etc. Notionally, the locked in a safe, split among many parties, etc. Notionally, the
stand-by key should be less subject to compromise than an active key, stand-by key should be less subject to compromise than an active key,
but that will be dependent on operational concerns not addressed but that will be dependent on operational concerns not addressed
here. here.
5.1 Adding A Trust Anchor 5.1. Adding A Trust Anchor
Assume an existing trust anchor key 'A'. Assume an existing trust anchor key 'A'.
1. Generate a new key pair. 1. Generate a new key pair.
2. Create a DNSKEY record from the key pair and set the SEP and Zone 2. Create a DNSKEY record from the key pair and set the SEP and Zone
Key bits. Key bits.
3. Add the DNSKEY to the RRSet. 3. Add the DNSKEY to the RRSet.
4. Sign the DNSKEY RRSet ONLY with the existing trust anchor key - 4. Sign the DNSKEY RRSet ONLY with the existing trust anchor key -
'A'. 'A'.
5. Wait a while. 5. Wait a while.
5.2 Deleting a Trust Anchor 5.2. Deleting a Trust Anchor
Assume existing trust anchors 'A' and 'B' and that you want to revoke Assume existing trust anchors 'A' and 'B' and that you want to revoke
and delete 'A'. and delete 'A'.
1. Set the revolcation bit on key 'A'. 1. Set the revolcation bit on key 'A'.
2. Sign the DNSKEY RRSet with both 'A' and 'B'. 2. Sign the DNSKEY RRSet with both 'A' and 'B'.
'A' is now revoked. The operator SHOULD include the revoked 'A' in 'A' is now revoked. The operator SHOULD include the revoked 'A' in
the RRSet for at least the remove hold-down time, but then may remove the RRSet for at least the remove hold-down time, but then may remove
it from the DNSKEY RRSet. it from the DNSKEY RRSet.
5.3 Key Roll-Over 5.3. Key Roll-Over
Assume existing keys A and B. 'A' is actively in use (i.e. has been Assume existing keys A and B. 'A' is actively in use (i.e. has been
signing the DNSKEY RRSet.) 'B' was the stand-by key. (i.e. has been signing the DNSKEY RRSet.) 'B' was the stand-by key. (i.e. has been
in the DNSKEY RRSet and is a valid trust anchor, but wasn't being in the DNSKEY RRSet and is a valid trust anchor, but wasn't being
used to sign the RRSet.) used to sign the RRSet.)
1. Generate a new key pair 'C'. 1. Generate a new key pair 'C'.
2. Add 'C' to the DNSKEY RRSet. 2. Add 'C' to the DNSKEY RRSet.
3. Set the revocation bit on key 'A'. 3. Set the revocation bit on key 'A'.
4. Sign the RRSet with 'A' and 'B'. 4. Sign the RRSet with 'A' and 'B'.
'A' is now revoked, 'B' is now the active key, and 'C' will be the 'A' is now revoked, 'B' is now the active key, and 'C' will be the
stand-by key once the hold-down expires. The operator SHOULD include stand-by key once the hold-down expires. The operator SHOULD include
the revoked 'A' in the RRSet for at least the remove hold-down time, the revoked 'A' in the RRSet for at least the remove hold-down time,
but may then remove it from the DNSKEY RRSet. but may then remove it from the DNSKEY RRSet.
5.4 Active Key Compromised 5.4. Active Key Compromised
This is the same as the mechanism for Key Roll-Over (Section 5.3) This is the same as the mechanism for Key Roll-Over (Section 5.3)
above assuming 'A' is the active key. above assuming 'A' is the active key.
5.5 Stand-by Key Compromised 5.5. Stand-by Key Compromised
Using the same assumptions and naming conventions as Key Roll-Over Using the same assumptions and naming conventions as Key Roll-Over
(Section 5.3) above: (Section 5.3) above:
1. Generate a new key pair 'C'. 1. Generate a new key pair 'C'.
2. Add 'C' to the DNSKEY RRSet. 2. Add 'C' to the DNSKEY RRSet.
3. Set the revocation bit on key 'B'. 3. Set the revocation bit on key 'B'.
4. Sign the RRSet with 'A' and 'B'. 4. Sign the RRSet with 'A' and 'B'.
'B' is now revoked, 'A' remains the active key, and 'C' will be the 'B' is now revoked, 'A' remains the active key, and 'C' will be the
stand-by key once the hold-down expires. 'B' SHOULD continue to be stand-by key once the hold-down expires. 'B' SHOULD continue to be
included in the RRSet for the remove hold-down time. included in the RRSet for the remove hold-down time.
6. Security Considerations 6. IANA Considerations
6.1 Key Ownership vs Acceptance Policy The IANA will need to assign a bit in the DNSKEY flags field (see
section 4.3 of [RFC3755]) for the REVOKE bit. There are no other
IANA actions required.
7. Security Considerations
7.1. Key Ownership vs Acceptance Policy
The reader should note that, while the zone owner is responsible The reader should note that, while the zone owner is responsible
creating and distributing keys, it's wholly the decision of the creating and distributing keys, it's wholly the decision of the
resolver owner as to whether to accept such keys for the resolver owner as to whether to accept such keys for the
authentication of the zone information. This implies the decision authentication of the zone information. This implies the decision
update trust anchor keys based on trust for a current trust anchor update trust anchor keys based on trust for a current trust anchor
key is also the resolver owner's decision. key is also the resolver owner's decision.
The resolver owner (and resolver implementers) MAY choose to permit The resolver owner (and resolver implementers) MAY choose to permit
or prevent key status updates based on this mechanism for specific or prevent key status updates based on this mechanism for specific
trust points. If they choose to prevent the automated updates, they trust points. If they choose to prevent the automated updates, they
will need to establish a mechanism for manual or other out-of-band will need to establish a mechanism for manual or other out-of-band
updates outside the scope of this document. updates outside the scope of this document.
6.2 Multiple Key Compromise 7.2. Multiple Key Compromise
This scheme permits recovery as long as at least one valid trust This scheme permits recovery as long as at least one valid trust
anchor key remains uncompromised. E.g. if there are three keys, you anchor key remains uncompromised. E.g. if there are three keys, you
can recover if two of them are compromised. The zone owner should can recover if two of them are compromised. The zone owner should
determine their own level of comfort with respect to the number of determine their own level of comfort with respect to the number of
active valid trust anchors in a zone and should be prepared to active valid trust anchors in a zone and should be prepared to
implement recovery procedures once they detect a compromise. A implement recovery procedures once they detect a compromise. A
manual or other out-of-band update of all resolvers will be required manual or other out-of-band update of all resolvers will be required
if all trust anchor keys at a trust point are compromised. if all trust anchor keys at a trust point are compromised.
6.3 Dynamic Updates 7.3. Dynamic Updates
Allowing a resolver to update its trust anchor set based in-band key Allowing a resolver to update its trust anchor set based in-band key
information is potentially less secure than a manual process. information is potentially less secure than a manual process.
However, given the nature of the DNS, the number of resolvers that However, given the nature of the DNS, the number of resolvers that
would require update if a trust anchor key were compromised, and the would require update if a trust anchor key were compromised, and the
lack of a standard management framework for DNS, this approach is no lack of a standard management framework for DNS, this approach is no
worse than the existing situation. worse than the existing situation.
7. Normative References 8. 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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2535] Eastlake, D., "Domain Name System Security Extensions", [RFC2535] Eastlake, D., "Domain Name System Security Extensions",
RFC 2535, March 1999. RFC 2535, March 1999.
[RFC3755] Weiler, S., "Legacy Resolver Compatibility for Delegation
Signer (DS)", RFC 3755, May 2004.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005. RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005. RFC 4034, March 2005.
[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
skipping to change at page 12, line 29 skipping to change at page 13, line 29
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