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INTERNET-DRAFT 31 January 2002
D. Massey
USC/ISI
S. Rose
NIST
Limiting the Scope of the KEY Resource Record
draft-ietf-dnsext-restrict-key-for-dnssec-01.txt
Status of this Document
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Distribution of this document
is unlimited. Comments regarding this document should be sent to
the author.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document limits the KEY resource record to only DNSSEC
keys. The original KEY resource record used sub-typing
to store both DNSSEC keys and arbitrary application keys.
Storing both DNSSEC and application keys in one record was
a mistake. This document removes application keys from
the KEY record by redefining the Protocol Octet field in
the KEY RDATA. As a result of removing application keys,
all but one of the flags in the KEY record become unnecessary
and are removed. Three existing application key sub-types
are changed to historic, but the format of the KEY record
is not changed. This document updates RFC 2535.
Massey/Rose Page 1
INTERNET-DRAFT 31 January 2002
1 Introduction
This document limits the scope the KEY resource record. The KEY
resource record was defined in [DNSSEC] and used resource record
sub-typing to hold arbitrary public keys such as Email, IPSEC, DNSSEC,
and TLS keys. This document eliminates the existing Email, IPSEC,
and TLS sub-types and prohibits the introduction of new sub-types.
DNSSEC will be the only allowable sub-type for the KEY record (hence
sub-typing is essentially eliminated) and all but one of the KEY
record flags are also eliminated.
Section 2 presents the motivation for restricting the KEY record
and Section ?? defines the revised KEY record. Section 4 and 5 summarize
the changes from RFC 2535 and discuss backwards compatibility. It
is important to note that this document restricts the use of the
KEY record and simplifies the flabs, does not change DNSSEC keys.
2 Motivation for Restricting the KEY Record
The KEY record RDATA [DNSSEC] consists of flags, a Protocol Octet,
an Algorithm type, and a public key. The Protocol Octet identifies
the KEY record sub-type. DNSSEC public keys are stored in the KEY
using a Protocol Octet value of 3. Email, IPSEC, and TLS keys are
also stored in the KEY resource record and using Protocol Octet values
of 1,2, and 4 (respectively). Protocol Octet values 5-254 are available
for assignment by IANA and values have been requested (but not assigned)
for applications such as SSH.
Any use of sub-typing has inherent limitations. A resolver can not
specify the desired sub-type in a DNS query and most DNS operations
apply only to resource records sets. For a example, a resolver can
not directly request KEY records with a particular sub-type. Instead,
the resolver must request all KEY records associated with a DNS name
and then search the set for the desired sub-type. DNSSEC signatures
also apply to the set of all KEY resource records associated with
the DNS name, regardless of sub-type.
In the case of the KEY record, the inherent sub-type limitations
are exacerbated since the sub-type is used to distinguish between
DNSSEC keys and application keys. DNSSEC keys and application keys
differ in virtually every respect and Section 2.1 discusses these
differences in more detail. Combining these very different types
of keys into a single sub-typed resource record adds unnecessary
complexity and increases the potential for implementation and deployment
Massey/Rose Page 2
INTERNET-DRAFT 31 January 2002
errors. Limited experimental deployment has shown that application
keys stored in KEY records are problematic.
This document addresses these issues by removing all application keys
from the KEY resource record. Note that the scope of this document
is strictly limited to the KEY record and this document does not
endorse or restrict the storage of application keys in other resource
records.
2.1 Differences Between DNSSEC and Application Keys
DNSSEC keys are an essential part of the DNSSEC protocol and are
used by both name servers and resolvers in order to perform DNS tasks.
A DNS zone, used to sign and authenticate RR sets, is most common
example of a DNSSEC key. SIG(0) and TKEY also use DNSSEC keys.
Application keys such as Email keys, IPSEC keys, and TLS keys and
are simply another type data. These keys have no special meaning
to a name server or resolver.
o They serve different purposes.
o They are managed by different administrators.
o They are authenticated according to different rules.
o Nameservers use different rules when including them in responses.
o Resolvers process them in different ways.
o Faults/key compromises have different consequences.
The purpose of a DNSSEC key is to sign resource records associated
with a DNS zone (or generate DNS transaction signatures in the case
of SIG(0)/TKEY). But the purpose of an application key is specific
to the application. Application keys, such as PGP/email, IPSEC, TLS,
and SSH keys, are not a mandatory part of any zone and the purpose
and proper use of application keys is outside the scope of DNS.
DNSSEC keys are managed by DNS administrators, but application keys
are managed by application administrators. The DNS zone administrator
determines the key lifetime, handles any suspected key compromises,
and manages any DNSSEC key changes. Likewise, the application administrator
is responsible for the same functions for the application keys related
to the application. For example, a user typically manages her own
PGP key and a server manages its own TLS key. Application key management
tasks are outside the scope of DNS administration.
Massey/Rose Page 3
INTERNET-DRAFT 31 January 2002
DNSSEC zone keys are used to authenticate application keys, but application
keys MUST NOT be used to authenticate DNS zone keys. A DNS zone
key is either configured as trusted key or authenticated by constructing
a chain of trust in the DNS hierarchy. To participate in the chain
of trust, a DNS zone must exchange zone key information with its
parent zone [DNSSEC]. Application keys are not configured as trusted
keys in the DNS and are never part of any DNS chain of trust. Application
key data should not be exchanged with the parent zone. A resolver
considers an application key authenticated if it has a valid signature
from the local DNS zone keys, but applications may impose additional
requirements before the application key is accepted as authentic.
It MAY be useful for nameservers to include DNS zone keys in the
additional section of a response, but application keys are typically
not useful unless they have been specifically requested. For example,
it may be useful to include the isi.edu zone key along with a response
that contain the www.isi.edu A record and SIG record. A secure resolver
will need the isi.edu zone key in order to check the SIG and authenticate
the www.isi.edu A record. It is typical not useful to include the
IPSEC, email, and TLS keys along with the A record. Note that by
placing application keys in the KEY record, a resolver will need
the IPSEC, email, TLS, and other key associated with isi.edu if the
resolver intends to authenticate the isi.edu zone key (since signatures
only apply to the entire KEY set).
DNS zone keys require special handling by resolvers, but application
keys should be treated the same as any other type of DNS data. The
DNSSEC keys are of no value to end applications, unless the applications
plan to do their own DNS authentication. Secure resolvers MUST NOT
use application keys as part of the authentication process. Application
keys have no unique value to resolvers and are only useful to the
application requesting the key. Note that if sub-types are used
to identify the application key, then either the interface to the
resolver must specify the sub-type or the application must be able
to accept all KEY records and pick out the desired the sub-type.
A fault or compromise of DNS zone key can lead to invalid or forged
DNS data, but a fault or compromise of an application key should
have no impact on other DNS data. Incorrectly adding or changing
a DNS zone key can invalidate all of the DNS data in zone and in
all of its subzones. By using a compromised key, an attacker can
forge data from the effected zone and any for any of its sub-zones.
A fault or compromise of an application key has implications for
that application, but it should not have an impact on the DNS. Note
that application key faults and key compromises can have an impact
on the entire DNS if the application key and DNS zone keys are both
stored in the KEY record.
Massey/Rose Page 4
INTERNET-DRAFT 31 January 2002
In summary, DNSSEC keys and application keys differ in most every
respect. DNSSEC keys are an essential part of the DNS infrastructure
and require special handling by DNS administrators and DNS resolvers.
Application keys are simply another type of data and have no special
meaning to DNS administrators or resolvers. These two different types
of data do not belong in the same resource record.
3 Definition of the KEY Resource Record
The KEY record uses type 25 and is used as resource record for storing
DNSSEC keys. The RDATA for a KEY RR consists of flags, a protocol
octet, the algorithm number octet, and the public key itself. The
format is as follows:
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags | protocol | algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ public key /
/ /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
In the flags field, all bits except bit 7 are reserved should be
zero. If Bit 7 (Zone bit) is set to 1, then the KEY is a DNS Zone
key. If Bit 7 is set to 0, the KEY is not a zone key. SIG(0)/TKEY
are examples of DNSSEC keys that are not zone keys.
The protocol field must be set to 3.
The algorithm and public key fields are not changed.
4 Changes from RFC 2535 KEY Record
The KEY RDATA format is not changed.
All flags except for the zone key flag are eliminated:
o The A/C bits (bits 0 and 1) are eliminated and must be 0.
o The extended flags bit (bit 3) is eliminated and must be 0.
o The host/user bit (bit 6) is eliminated and must be 0.
Massey/Rose Page 5
INTERNET-DRAFT 31 January 2002
o The zone bit (bit 7) remains unchanged.
o The signatory field (bits 12-15) are eliminated by [SDU] and
must be 0.
o Bits 2,4,5,8,9,10,11 remain unchanged. They are reserved and
must be zero.
All Protocol Octet values except DNSSEC (3) are eliminated:
o Value 1 (Email) is renamed to reserved.
o Value 2 (IPSEC) is renamed to reserved.
o Value 3 (DNSSEC) is unchanged.
o Value 4 (TLS) is renamed to reserved.
o Value 5-254 remains unchanged (reserved).
o Value 255 (ANY) is renamed to reserved.
Name servers and resolvers SHOULD reject any KEY with a Protocol
other than 3.
The algorithm and public key fields are not changed.
5 Backward Compatibility
No backwards compatibility is provided for application keys. Any
Email, IPSEC, or TLS keys are now deprecated and SHOULD be rejected
by name servers and resolvers. However, problems with applications
keys (such as keys at the apex and large RR sets) and have already
been identified some change in the definition and/or usage of the
KEY record would be required even if the approach described here
were not required.
DNSSEC zone KEY records are not change and remain backwards compatible.
A properly formatted RFC 2535 zone KEY would have all flag bits,
other than the Zone Bit (Bit 7), set to 0 and would have the Protocol
Octet set to 3. This remains true under the restricted KEY.
DNSSEC non-zone KEY records (SIG(0)/TKEY keys) are backwards compatible,
but the distinction between host and user keys (flag bit 6) is lost.
Overall, existing nameservers and resolvers will continue to correctly
process KEY records with a sub-type of DNSSEC keys.
Massey/Rose Page 6
INTERNET-DRAFT 31 January 2002
6 Storing Application Keys in the DNS
The scope of this document is strictly limited to the KEY record.
This document prohibits storing application keys in the KEY record,
but it does not endorse or restrict the storing application keys
in other record types. Other documents should describe how DNS handles
application keys.
7 IANA Consideration
KEY record Protocol Octet values 1,2,4, and 255 should be changed
to reserved.
Assignment of any future KEY record Protocol Octet values requires
a standards action.
8 Security Consideration
This document eliminates potential security problems that could arise
due to the coupling of DNS zone keys and application keys. Prior
to the change described in the document, a correctly authenticated
KEY set could include both application keys and DNSSEC keys. If
one of the application keys is compromised, it could be used as a
false zone key to create phony DNS signatures (SIG records). Resolvers
that do not carefully check the KEY sub-type may believe these false
signatures and incorrectly authenticate DNS data. With this change,
application keys cannot appear in an authenticated KEY set and this
vulnerability is eliminated.
The format and correct usage of DNSSEC keys is not changed by this
document and no new security considerations are introduced.
9 Intellectual Property
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to pertain
to the implementation or use of the technology described in this
document or the extent to which any license under such rights might
or might not be available; neither does it represent that it has
made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and standards-
related documentation can be found in BCP-11.
Massey/Rose Page 7
INTERNET-DRAFT 31 January 2002
Copies of claims of rights made available for publication and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementors or users of this specification
can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary rights
which may cover technology that may be required to practice this
standard. Please address the information to the IETF Executive Director.
10 References
[DNSSEC] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[SDU] Wellington, B., "Secure Domain Name System (DNS) Dynamic Update",
RFC 3007, November 2000.
11 Author Information
Daniel Massey <masseyd@isi.edu>
USC Information Sciences Institute
3811 North Fairfax Drive, Suite 200
Arlington, VA 22203
Scott Rose <scott.rose@nist.gov>
National Institute for Standards and Technology
Gaithersburg, MD
Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished
to others, and derivative works that comment on or otherwise explain
it or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copy- right notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of developing
Massey/Rose Page 8
INTERNET-DRAFT 31 January 2002
Internet standards in which case the procedures for copyrights defined
in the Internet Standards process must be followed, or as required
to translate it into languages other than English.
The limited permissions granted above are perpetual and will not
be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN
WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE."
Massey/Rose Page 9

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DNS Extensions D. Massey
Internet-Draft USC/ISI
Expires: March 11, 2003 S. Rose
NIST
September 10, 2002
Limiting the Scope of the KEY Resource Record
out
draft-ietf-dnsext-restrict-key-for-dnssec-04.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on March 11, 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document limits the Domain Name System KEY resource record to
only keys used by the Domain Name System Security Extensions
(DNSSEC). The original KEY resource record used sub-typing to store
both DNSSEC keys and arbitrary application keys. Storing both DNSSEC
and application keys with the same record type is a mistake. This
document removes application keys from the KEY record by redefining
the Protocol Octet field in the KEY Resource Record Data. As a
result of removing application keys, all but one of the flags in the
KEY record become unnecessary and are redefined. Three existing
application key sub-types are changed to reserved, but the format of
Massey & Rose Expires March 11, 2003 [Page 1]
Internet-Draft Limiting the Scope of the KEY Resource Record September 2002
the KEY record is not changed. This document updates RFC 2535.
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 RFC 2119 [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation for Restricting the KEY RR . . . . . . . . . . . . 4
2.1 Differences Between DNSSEC and Application Keys . . . . . . . 4
3. Definition of the KEY Resource Record . . . . . . . . . . . . 7
4. Changes from RFC 2535 KEY RR . . . . . . . . . . . . . . . . . 8
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 10
6. Storing Application Keys in the DNS . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15
Massey & Rose Expires March 11, 2003 [Page 2]
Internet-Draft Limiting the Scope of the KEY Resource Record September 2002
1. Introduction
This document limits the scope of the KEY resource record. The KEY
resource record was defined in [3] and used resource record sub-
typing to hold arbitrary public keys such as Email, IPSEC, DNSSEC,
and TLS keys. This document eliminates the existing Email, IPSEC,
and TLS sub-types and prohibits the introduction of new sub-types.
DNSSEC will be the only allowable sub-type for the KEY RR (hence sub-
typing is essentially eliminated) and all but one of the KEY RR flags
are also eliminated.
Section 2 presents the motivation for restricting the KEY record and
Section 3 defines the revised KEY RR. Sections 4 and 5 summarize the
changes from RFC 2535 and discuss backwards compatibility. It is
important to note that this document restricts the use of the KEY RR
and simplifies the flags, but does not change the definition or use
of DNSSEC keys.
Massey & Rose Expires March 11, 2003 [Page 3]
Internet-Draft Limiting the Scope of the KEY Resource Record September 2002
2. Motivation for Restricting the KEY RR
The KEY RR RDATA [3] consists of Flags, a Protocol Octet, an
Algorithm type, and a Public Key. The Protocol Octet identifies the
KEY RR sub-type. DNSSEC public keys are stored in the KEY RR using a
Protocol Octet value of 3. Email, IPSEC, and TLS keys were also
stored in the KEY RR and used Protocol Octet values of 1,2, and 4
(respectively). Protocol Octet values 5-254 were available for
assignment by IANA and values were requested (but not assigned) for
applications such as SSH.
Any use of sub-typing has inherent limitations. A resolver can not
specify the desired sub-type in a DNS query and most DNS operations
apply only to resource records sets. For example, a resolver can not
directly request the DNSSEC subtype KEY RRs. Instead, the resolver
has to request all KEY RRs associated with a DNS name and then search
the set for the desired DNSSEC sub-type. DNSSEC signatures also
apply to the set of all KEY resource records associated with the DNS
name, regardless of sub-type.
In the case of the KEY RR, the inherent sub-type limitations are
exacerbated since the sub-type is used to distinguish between DNSSEC
keys and application keys. DNSSEC keys and application keys differ
in virtually every respect and Section 2.1 discusses these
differences in more detail. Combining these very different types of
keys into a single sub-typed resource record adds unnecessary
complexity and increases the potential for implementation and
deployment errors. Limited experimental deployment has shown that
application keys stored in KEY RRs are problematic.
This document addresses these issues by removing all application keys
from the KEY resource record. Note that the scope of this document
is strictly limited to the KEY RR and this document does not endorse
or restrict the storage of application keys in other, yet undefined,
resource records.
2.1 Differences Between DNSSEC and Application Keys
DNSSEC keys are an essential part of the DNSSEC protocol and are used
by both name servers and resolvers in order to perform DNS tasks. A
DNS zone key, used to sign and authenticate RR sets, is the most
common example of a DNSSEC key. SIG(0) [4] and TKEY [3] also use
DNSSEC keys.
Application keys such as Email keys, IPSEC keys, and TLS keys are
simply another type data. These keys have no special meaning to a
name server or resolver.
Massey & Rose Expires March 11, 2003 [Page 4]
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The following table summarizes some of the differences between DNSSEC
keys and application keys:
1. They serve different purposes.
2. They are managed by different administrators.
3. They are authenticated according to different rules.
4. Nameservers use different rules when including them in responses.
5. Resolvers process them in different ways.
6. Faults/key compromises have different consequences.
1. The purpose of a DNSSEC key is to sign resource records
associated with a DNS zone (or generate DNS transaction signatures
in the case of SIG(0)/TKEY). But the purpose of an application key
is specific to the application. Application keys, such as PGP/email,
IPSEC, TLS, and SSH keys, are not a mandatory part of any zone and
the purpose and proper use of application keys is outside the scope
of DNS.
2. DNSSEC keys are managed by DNS administrators, but application
keys are managed by application administrators. The DNS zone
administrator determines the key lifetime, handles any suspected key
compromises, and manages any DNSSEC key changes. Likewise, the
application administrator is responsible for the same functions for
the application keys related to the application. For example, a user
typically manages her own PGP key and a server manages its own TLS
key. Application key management tasks are outside the scope of DNS
administration.
3. DNSSEC zone keys are used to authenticate application keys, but
by definition application keys are not allowed to authenticate DNS
zone keys. A DNS zone key is either configured as trusted key or
authenticated by constructing a chain of trust in the DNS hierarchy.
To participate in the chain of trust, a DNS zone needs to exchange
zone key information with its parent zone [3]. Application keys are
not configured as trusted keys in the DNS and are never part of any
DNS chain of trust. Application key data is not needed by the parent
and does not need to be exchanged with the parent zone for secure DNS
resolution to work. A resolver considers an application key RRset as
authenticated DNS information if it has a valid signature from the
local DNS zone keys, but applications could impose additional
security requirements before the application key is accepted as
authentic for use with the application.
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4. It may be useful for nameservers to include DNS zone keys in the
additional section of a response, but application keys are typically
not useful unless they have been specifically requested. For
example, it could be useful to include the example.com zone key along
with a response that contains the www.example.com A record and SIG
record. A secure resolver will need the example.com zone key in
order to check the SIG and authenticate the www.example.com A record.
It is typically not useful to include the IPSEC, email, and TLS keys
along with the A record. Note that by placing application keys in
the KEY record, a resolver would need the IPSEC, email, TLS, and
other key associated with example.com if the resolver intends to
authenticate the example.com zone key (since signatures only apply to
the entire KEY RR set). Depending on the number of protocols
involved, the KEY RR set could grow unwieldy for resolvers, and DNS
administrators to manage.
5. DNS zone keys require special handling by resolvers, but
application keys are treated the same as any other type of DNS data.
The DNSSEC keys are of no value to end applications, unless the
applications plan to do their own DNS authentication. By definition,
secure resolvers are not allowed to use application keys as part of
the authentication process. Application keys have no unique meaning
to resolvers and are only useful to the application requesting the
key. Note that if sub-types are used to identify the application
key, then either the interface to the resolver needs to specify the
sub-type or the application needs to be able to accept all KEY RRs
and pick out the desired the sub-type.
6. A fault or compromise of a DNS zone key can lead to invalid or
forged DNS data, but a fault or compromise of an application key
should have no impact on other DNS data. Incorrectly adding or
changing a DNS zone key can invalidate all of the DNS data in zone
and in all of its subzones. By using a compromised key, an attacker
can forge data from the effected zone and any for any of its sub-
zones. A fault or compromise of an application key has implications
for that application, but it should not have an impact on the DNS.
Note that application key faults and key compromises can have an
impact on the entire DNS if the application key and DNS zone keys are
both stored in the KEY RR.
In summary, DNSSEC keys and application keys differ in most every
respect. DNSSEC keys are an essential part of the DNS infrastructure
and require special handling by DNS administrators and DNS resolvers.
Application keys are simply another type of data and have no special
meaning to DNS administrators or resolvers. These two different
types of data do not belong in the same resource record.
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Internet-Draft Limiting the Scope of the KEY Resource Record September 2002
3. Definition of the KEY Resource Record
The KEY RR uses type 25 and is used as resource record for storing
DNSSEC keys. The RDATA for a KEY RR consists of flags, a protocol
octet, the algorithm number octet, and the public key itself. The
format is as follows:
---------------------------------------------------------------------
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags | protocol | algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /
/ public key /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
KEY RR Format
---------------------------------------------------------------------
In the flags field, all bits except bit 7 are reserved and MUST be
zero. If Bit 7 (Zone bit) is set to 1, then the KEY is a DNS Zone
key. If Bit 7 is set to 0, the KEY is not a zone key. SIG(0)/TKEY
are examples of DNSSEC keys that are not zone keys.
The protocol field MUST be set to 3.
The algorithm and public key fields are not changed.
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4. Changes from RFC 2535 KEY RR
The KEY RDATA format is not changed.
All flags except for the zone key flag are eliminated:
The A/C bits (bits 0 and 1) are eliminated. They MUST be set to 0
and MUST be ignored by the receiver.
The extended flags bit (bit 3) is eliminated. It MUST be set to 0
and MUST be ignored by the receiver.
The host/user bit (bit 6) is eliminated. It MUST be set to 0 and
MUST be ignored by the receiver.
The zone bit (bit 7) remains unchanged.
The signatory field (bits 12-15) are eliminated by [5]. They MUST
be set to 0 and MUST be ignored by the receiver.
Bits 2,4,5,8,9,10,11 remain unchanged. They are reserved, MUST be
set to zero and MUST be ignored by the receiver.
Assignment of any future KEY RR Flag values requires a standards
action.
All Protocol Octet values except DNSSEC (3) are eliminated:
Value 1 (Email) is renamed to RESERVED.
Value 2 (IPSEC) is renamed to RESERVED.
Value 3 (DNSSEC) is unchanged.
Value 4 (TLS) is renamed to RESERVED.
Value 5-254 remains unchanged (reserved).
Value 255 (ANY) is renamed to RESERVED.
The authoritative data for a zone MUST NOT include any KEY records
with a protocol octet other than 3. The registry maintained by IANA
for protocol values is closed for new assignemnts.
Name servers and resolvers SHOULD accept KEY RR sets that contain KEY
RRs with a value other than 3. If out of date DNS zones contain
deprecated KEY RRs with a protocol octet value other than 3, then
simply dropping the deprecated KEY RRs from the KEY RR set would
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invalidate any associated SIG record(s) and could create caching
consistency problems. Note that KEY RRs with a protocol octet value
other than 3 MUST NOT be used to authenticate DNS data.
The algorithm and public key fields are not changed.
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5. Backward Compatibility
DNSSEC zone KEY RRs are not changed and remain backwards compatible.
A properly formatted RFC 2535 zone KEY would have all flag bits,
other than the Zone Bit (Bit 7), set to 0 and would have the Protocol
Octet set to 3. This remains true under the restricted KEY.
DNSSEC non-zone KEY RRs (SIG(0)/TKEY keys) are backwards compatible,
but the distinction between host and user keys (flag bit 6) is lost.
No backwards compatibility is provided for application keys. Any
Email, IPSEC, or TLS keys are now deprecated. Storing application
keys in the KEY RR created problems such as keys at the apex and
large RR sets and some change in the definition and/or usage of the
KEY RR would have been required even if the approach described here
were not adopted.
Overall, existing nameservers and resolvers will continue to
correctly process KEY RRs with a sub-type of DNSSEC keys.
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6. Storing Application Keys in the DNS
The scope of this document is strictly limited to the KEY record.
This document prohibits storing application keys in the KEY record,
but it does not endorse or restrict the storing application keys in
other record types. Other documents can describe how DNS handles
application keys.
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7. IANA Considerations
RFC 2535 created an IANA registry for DNS KEY Resource Record
Protocol Octet values. Values to 1,2,3, 4, and 255 were assigned by
RFC 2535 and values 5-254 were made available for assignment by IANA.
This document makes two sets of changes to this registry.
First, this document re-assigns DNS KEY Resource Record Protocol
Octet values 1, 2, 4, and 255 to ``reserved''. DNS Key Resource
Record Protocol Octet Value 3 remains unchanged as ``DNSSEC''.
Second, new values are no longer available for assignment by IANA and
this document closes the IANA registry for DNS KEY Resource Record
Protocol Octet Values. Assignment of any future KEY Resource Record
Protocol Octet values requires a standards action.
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8. Security Considerations
This document eliminates potential security problems that could arise
due to the coupling of DNS zone keys and application keys. Prior to
the change described in this document, a correctly authenticated KEY
set could include both application keys and DNSSEC keys. This draft
restricts the KEY RR to DNS security usage only. This is an attempt
to simplify the security model and make it less user-error prone. If
one of the application keys is compromised, it could be used as a
false zone key to create false DNS signatures (SIG records).
Resolvers that do not carefully check the KEY sub-type could believe
these false signatures and incorrectly authenticate DNS data. With
this change, application keys cannot appear in an authenticated KEY
set and this vulnerability is eliminated.
The format and correct usage of DNSSEC keys is not changed by this
document and no new security considerations are introduced.
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References (Normative)
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[3] Eastlake, D., "Secret Key Establishment for DNS (TKEY RR)", RFC
2930, September 2000.
[4] Eastlake, D., "DNS Request and Transaction Signatures (
SIG(0)s)", RFC 2931, September 2000.
[5] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, November 2000.
Authors' Addresses
Dan Massey
USC Information Sciences Institute
3811 N. Fairfax Drive
Arlington, VA 22203
USA
EMail: masseyd@isi.edu
Scott Rose
National Institute for Standards and Technology
100 Bureau Drive
Gaithersburg, MD 20899-3460
USA
EMail: scott.rose@nist.gov
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Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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Internet Engineering Task Force S. Thomson, Cisco
INTERNET-DRAFT C. Huitema, Microsoft
September 11, 2002 V. Ksinant, 6WIND
Expires March 11, 2003 M. Souissi, AFNIC
DNS Extensions to support IP version 6
<draft-ietf-dnsext-rfc1886bis-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC2026].
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html.
This Internet Draft expires March 11, 2003.
Abstract
This document defines the changes that need to be made to the Domain
Name System to support hosts running IP version 6 (IPv6). The
changes include a new resource record type to store an IPv6 address,
a new domain to support lookups based on an IPv6 address, and updated
definitions of existing query types that return Internet addresses as
part of additional section processing. The extensions are designed
to be compatible with existing applications and, in particular, DNS
implementations themselves.
This document updates RFC 1886 [5]. Changes mainly consist in
replacing the IP6.INT domain by IP6.ARPA as defined in RFC 3152 [6].
draft-ietf-dnsext-rfc1886bis-00.txt [Page 1]
INTERNET-DRAFT DNS Extensions to support IP version 6 September 2002
Table of Contents
1. Introduction............................................. 2
2. New resource record definition and domain................ 2
2.1. AAAA record type.................................... 3
2.2. AAAA data format.................................... 3
2.3. AAAA query.......................................... 3
2.4. Textual format of AAAA records...................... 3
2.5. IP6.ARPA domain..................................... 3
3. Modifications to existing query types.................... 4
4. Security Considerations.................................. 4
APPENDIX A: Changes from RFC-1886............................ 4
Acknowledgments.............................................. 5
References................................................... 5
Authors' Addresses........................................... 6
Full Copyright Statement..................................... 7
1. INTRODUCTION
Current support for the storage of Internet addresses in the Domain
Name System (DNS)[1,2] cannot easily be extended to support IPv6
addresses[3] since applications assume that address queries return
32-bit IPv4 addresses only.
To support the storage of IPv6 addresses we define the following
extensions:
o A new resource record type is defined to map a domain name to an
IPv6 address.
o A new domain is defined to support lookups based on address.
o Existing queries that perform additional section processing to
locate IPv4 addresses are redefined to perform additional
section processing on both IPv4 and IPv6 addresses.
The changes are designed to be compatible with existing software. The
existing support for IPv4 addresses is retained. Transition issues
related to the co-existence of both IPv4 and IPv6 addresses in DNS
are discussed in [4].
2. NEW RESOURCE RECORD DEFINITION AND DOMAIN
A new record type is defined to store a host's IPv6 address. A host
that has more than one IPv6 address must have more than one such
record.
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2.1 AAAA record type
The AAAA resource record type is a new record specific to the
Internet class that stores a single IPv6 address.
The value of the type is 28 (decimal).
2.2 AAAA data format
A 128 bit IPv6 address is encoded in the data portion of an AAAA
resource record in network byte order (high-order byte first).
2.3 AAAA query
An AAAA query for a specified domain name in the Internet class
returns all associated AAAA resource records in the answer section of
a response.
A type AAAA query does not perform additional section processing.
2.4 Textual format of AAAA records
The textual representation of the data portion of the AAAA resource
record used in a master database file is the textual representation
of a IPv6 address as defined in [3].
2.5 IP6.ARPA Domain
A special domain is defined to look up a record given an address. The
intent of this domain is to provide a way of mapping an IPv6 address
to a host name, although it may be used for other purposes as well.
The domain is rooted at IP6.ARPA.
An IPv6 address is represented as a name in the IP6.ARPA domain by a
sequence of nibbles separated by dots with the suffix ".IP6.ARPA".
The sequence of nibbles is encoded in reverse order, i.e. the
low-order nibble is encoded first, followed by the next low-order
nibble and so on. Each nibble is represented by a hexadecimal digit.
For example, the inverse lookup domain name corresponding to the
address
4321:0:1:2:3:4:567:89ab
would be
b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.0.1.2.3.4.IP6.
ARPA.
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3. MODIFICATIONS TO EXISTING QUERY TYPES
All existing query types that perform type A additional section
processing, i.e. name server (NS), mail exchange (MX) and mailbox
(MB) query types, must be redefined to perform both type A and type
AAAA additional section processing. These new definitions mean that a
name server must add any relevant IPv4 addresses and any relevant
IPv6 addresses available locally to the additional section of a
response when processing any one of the above queries.
4. SECURITY CONSIDERATIONS
Any information obtained from the DNS must be regarded as unsafe
unless techniques specified in [7] or [8] are used. The definitions
of the AAAA record type and of the IP6.ARPA domain do not change the
model for use of these techniques.
So, this specification is not believed to cause any new security
problems, nor to solve any existing ones.
APPENDIX A: Changes from RFC 1886
The following changes were made from RFC 1886 "DNS Extensions to
support IP version 6":
- Replaced the "IP6.INT" domain by "IP6.ARPA".
- Added security considerations.
- Updated references :
* From RFC 1884 to RFC 2373 (IP Version 6 Addressing
Architecture).
* From "work in progress" to RFC 2893 (Transition Mechanisms for
IPv6 Hosts and Routers).
* Added reference to RFC 1886, RFC 3152, RFC 2535 and RFC 2845.
- Updated document abstract
- Added table of contents
- Added full copyright statement
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Acknowledgements
Vladimir Ksinant and Mohsen Souissi would like to thank Sebastien
Barbin (IRISA), Luc Beloeil (France Telecom R&D), Jean-Mickael
Guerin (6WIND), Vincent Levigneron (AFNIC), Alain Ritoux (6WIND),
Frederic Roudaut (IRISA) and G6 group for their help during the RFC
1886 Interop tests sessions.
Many thanks to Alain Durand and Olafur Gudmundsson for their support.
REFERENCES
[1] Mockapetris, P., "Domain Names - Concepts and Facilities", STD
13, RFC 1034, USC/Information Sciences Institute, November 1987.
[2] Mockapetris, P., "Domain Names - Implementation and Specifica-
tion", STD 13, RFC 1035, USC/Information Sciences Institute,
November 1987.
[3] Hinden, R., and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, Nokia, Cisco, July 1998.
This RFC is being updated. The current draft is
"draft-ietf-ipngwg-addr-arch-v3-09.txt", Hinden, R., and
S. Deering, August 26, 2002
[4] Gilligan, R., and E. Nordmark, "Transition Mechanisms for IPv6
Hosts and Routers", RFC 2893, FreeGate Corp., Sun Microsystems
Inc., August 2000.
This RFC is being updated. The current draft is
"draft-ietf-ngtrans-mech-v2-00.txt", Gilligan, R., and
E. Nordmark, July 17, 2002
[5] Thomson, S., and C. Huitema, "DNS Extensions to support IP
version 6", RFC 1886, Bellcore, INRIA, December 1995.
[6] Bush, R., "Delegation of IP6.ARPA", RFC 3152, RGnet, August
2001.
[7] Eastlake, D., "Domain Name System Security Extensions",
RFC 2535, IBM, March 1999
[8] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)",
RFC 2845, ISC, NAI Labs, Motorola, Nominum, May 2000.
draft-ietf-dnsext-rfc1886bis-00.txt [Page 5]
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Authors' Addresses
Susan Thomson
Cisco Systems
499 Thornall Street, 8th floor
Edison, NJ 08837
Telephone: 732-635-3086
Email: sethomso@cisco.com
Christian Huitema
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
Email: huitema@microsoft.com
Vladimir Ksinant
6WIND S.A.
Immeuble Central Gare - Bat.C
1, place Charles de Gaulle
78180, Montigny-Le-Bretonneux - France
Phone: +33 1 39 30 92 36
Email: vladimir.ksinant@6wind.com
Mohsen Souissi
AFNIC
Immeuble International
2, rue Stephenson,
78181, Saint-Quentin en Yvelines Cedex - France
Phone: +33 1 39 30 83 40
Email: Mohsen.Souissi@nic.fr
draft-ietf-dnsext-rfc1886bis-00.txt [Page 6]
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Full Copyright Statement
Copyright (C) The Internet Society (date). All Rights
Reserved.
This document and translations of it may be copied and
furnished to others, and derivative works that comment on or
otherwise explain it or assist in its implmentation may be
prepared, copied, published and distributed, in whole or in
part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such
copies and derivative works. However, this document itself may
not be modified in any way, such as by removing the copyright
notice or references to the Internet Society or other Internet
organizations, except as needed for the purpose of developing
Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or
as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or
assigns.
This document and the information contained herein is provided
on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE
OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE."
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draft-ietf-dnsext-rfc1886bis-00.txt [Page 7]