draft-ietf-dnssec-secext2-03.txt   draft-ietf-dnssec-secext2-04.txt 
DNS Security Working Group Donald E. Eastlake 3rd DNS Security Working Group Donald E. Eastlake 3rd
INTERNET-DRAFT CyberCash INTERNET-DRAFT CyberCash
OBSOLETES RFC 2065 OBSOLETES RFC 2065
UPDATES RFC 1034, 1035 UPDATES RFC 1034, 1035
Expires: July 1998 January 1998
Domain Name System Security Extensions Domain Name System Security Extensions
------ ---- ------ -------- ---------- ------ ---- ------ -------- ----------
Status of This Document Status of This Document
This draft, file name draft-ietf-dnssec-secext2-03.txt, is intended This draft, file name draft-ietf-dnssec-secext2-04.txt, is intended
to become a Proposed Standard RFC obsoleting Proposed Standard RFC to become a Proposed Standard RFC obsoleting Proposed Standard RFC
2065. Distribution of this document is unlimited. Comments should be 2065. Distribution of this document is unlimited. Comments should be
sent to the DNS Security Working Group mailing list <dns- sent to the DNS Security Working Group mailing list <dns-
security@tis.com> or to the author. security@tis.com> or to the author.
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
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Abstract Abstract
Extensions to the Domain Name System (DNS) are described that provide Extensions to the Domain Name System (DNS) are described that provide
data integrity and authentication to security aware resolvers or data integrity and authentication to security aware resolvers and
applications through the use of cryptographic digital signatures. applications through the use of cryptographic digital signatures.
These digital signatures are included in secured zones as resource These digital signatures are included in secured zones as resource
records. Security can also be provided through non-security aware records. Security can also be provided through non-security aware
DNS servers in some cases. DNS servers in some cases.
The extensions provide for the storage of authenticated public keys The extensions provide for the storage of authenticated public keys
in the DNS. This storage of keys can support general public key in the DNS. This storage of keys can support general public key
distribution services as well as DNS security. The stored keys distribution services as well as DNS security. The stored keys
enable security aware resolvers to learn the authenticating key of enable security aware resolvers to learn the authenticating key of
zones in addition to those for which they are initially configured. zones in addition to those for which they are initially configured.
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3. The KEY Resource Record................................12 3. The KEY Resource Record................................12
3.1 KEY RDATA format......................................12 3.1 KEY RDATA format......................................12
3.1.1 Object Types, DNS Names, and Keys...................12 3.1.1 Object Types, DNS Names, and Keys...................12
3.1.2 The KEY RR Flag Field...............................13 3.1.2 The KEY RR Flag Field...............................13
3.1.3 The Protocol Octet..................................14 3.1.3 The Protocol Octet..................................14
3.2 The KEY Algorithm Number Specification................15 3.2 The KEY Algorithm Number Specification................15
3.3 Interaction of Flags, Algorithm, and Protocol Bytes...16 3.3 Interaction of Flags, Algorithm, and Protocol Bytes...16
3.4 Determination of Zone Secure/Unsecured Status.........17 3.4 Determination of Zone Secure/Unsecured Status.........17
3.5 KEY RRs in the Construction of Responses..............18 3.5 KEY RRs in the Construction of Responses..............18
4. The SIG Resource Record................................19 4. The SIG Resource Record................................20
4.1 SIG RDATA Format......................................19 4.1 SIG RDATA Format......................................20
4.1.1 ....................................................19 4.1.1 ....................................................20
4.1.2 Algorithm Number Field..............................20 4.1.2 Algorithm Number Field..............................21
4.1.3 Labels Field........................................20 4.1.3 Labels Field........................................21
4.1.4 Original TTL Field..................................20 4.1.4 Original TTL Field..................................21
4.1.5 Signature Expiration and Inception Fields...........21 4.1.5 Signature Expiration and Inception Fields...........22
4.1.6 Key Tag Field.......................................21 4.1.6 Key Tag Field.......................................22
4.1.7 Signer's Name Field.................................21 4.1.7 Signer's Name Field.................................22
4.1.8 Signature Field.....................................22 4.1.8 Signature Field.....................................23
4.1.8.1 Calculating Transaction and Request SIGs..........22 4.1.8.1 Calculating Transaction and Request SIGs..........23
4.2 SIG RRs in the Construction of Responses..............23 4.2 SIG RRs in the Construction of Responses..............24
4.3 Processing Responses and SIG RRs......................24 4.3 Processing Responses and SIG RRs......................25
4.4 Signature Lifetime, Expiration, TTLs, and Validity....25 4.4 Signature Lifetime, Expiration, TTLs, and Validity....26
4.5 SIG Under The Meta-Root Key and The Root Zone.........25
5. Non-existent Names and Types...........................27 5. Non-existent Names and Types...........................27
5.1 The NXT Resource Record...............................27 5.1 The NXT Resource Record...............................27
5.2 NXT RDATA Format......................................28 5.2 NXT RDATA Format......................................28
5.3 Additional Complexity Due to Wildcards................28 5.3 Additional Complexity Due to Wildcards................28
5.4 Example...............................................29 5.4 Example...............................................29
5.5 Special Considerations at Delegation Points...........30 5.5 Special Considerations at Delegation Points...........30
5.6 Zone Transfers........................................30 5.6 Zone Transfers........................................30
5.6.1 Incremental Zone Transfers..........................30 5.6.1 Full Zone Transfers.................................30
5.6.2 Incremental Zone Transfers..........................31
6. How to Resolve Securely and the AD and CD Bits.........32 6. How to Resolve Securely and the AD and CD Bits.........32
6.1 The AD and CD Header Bits.............................32 6.1 The AD and CD Header Bits.............................32
6.2 Staticly Configured Keys..............................33 6.2 Staticly Configured Keys..............................33
6.3 Chaining Through The DNS..............................34 6.3 Chaining Through The DNS..............................34
6.3.1 Chaining Through KEYs...............................34 6.3.1 Chaining Through KEYs...............................34
6.3.2 Conflicting Data....................................36 6.3.2 Conflicting Data....................................36
6.4 Secure Time...........................................36 6.4 Secure Time...........................................36
7. ASCII Representation of Security RRs...................37 7. ASCII Representation of Security RRs...................38
7.1 Presentation of KEY RRs...............................37 7.1 Presentation of KEY RRs...............................38
7.2 Presentation of SIG RRs...............................38 7.2 Presentation of SIG RRs...............................39
7.3 Presentation of NXT RRs...............................39 7.3 Presentation of NXT RRs...............................40
8. Canonical Form and Order of Resource Records...........40 8. Canonical Form and Order of Resource Records...........41
8.1 Canonical RR Form.....................................40 8.1 Canonical RR Form.....................................41
8.2 Canonical DNS Name Order..............................40 8.2 Canonical DNS Name Order..............................41
8.3 Canonical RR Ordering Within An RRset.................41 8.3 Canonical RR Ordering Within An RRset.................42
8.4 Canonical Ordering of RR Types........................41 8.4 Canonical Ordering of RR Types........................42
9. Conformance............................................42 9. Conformance............................................43
9.1 Server Conformance....................................42 9.1 Server Conformance....................................43
9.2 Resolver Conformance..................................42 9.2 Resolver Conformance..................................43
10. Security Considerations...............................43 10. Security Considerations...............................44
References................................................44 References................................................45
Author's Address..........................................46 Author's Address..........................................47
Expiration and File Name..................................46 Expiration and File Name..................................47
Appendix A: Base 64 Encoding..............................47 Appendix A: Base 64 Encoding..............................48
Appendix B: Changes from RFC 2065.........................49 Appendix B: Changes from RFC 2065.........................50
Appendix C: Key Tag Calculation...........................51 Appendix C: Key Tag Calculation...........................52
1. Overview of Contents 1. Overview of Contents
This document standardizes extensions of the Domain Name System (DNS) This document standardizes extensions of the Domain Name System (DNS)
protocol to support DNS security and public key distribution. It protocol to support DNS security and public key distribution. It
assumes that the reader is familiar with the Domain Name System, assumes that the reader is familiar with the Domain Name System,
particularly as described in RFCs 1033, 1034, 1035 and later RFCs. particularly as described in RFCs 1033, 1034, 1035 and later RFCs. An
An earlier version of these extensions appears in RFC 2065. This earlier version of these extensions appears in RFC 2065. This
replacement for that RFC incorporates early implementation experience replacement for that RFC incorporates early implementation experience
and requests from potential users. and requests from potential users.
Section 2 provides an overview of the extensions and the key Section 2 provides an overview of the extensions and the key
distribution, data origin authentication, and transaction and request distribution, data origin authentication, and transaction and request
security they provide. security they provide.
Section 3 discusses the KEY resource record, its structure, and use Section 3 discusses the KEY resource record, its structure, and use
in DNS responses. These resource records represent the public keys in DNS responses. These resource records represent the public keys
of entities named in the DNS and are used for key distribution. of entities named in the DNS and are used for key distribution.
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is no key associated with that entity. is no key associated with that entity.
Under conditions described in Section 3.5, security aware DNS servers Under conditions described in Section 3.5, security aware DNS servers
will automatically attempt to return KEY resources as additional will automatically attempt to return KEY resources as additional
information, along with those resource records actually requested, to information, along with those resource records actually requested, to
minimize the number of queries needed. minimize the number of queries needed.
2.3 Data Origin Authentication and Integrity 2.3 Data Origin Authentication and Integrity
Authentication is provided by associating with resource record sets Authentication is provided by associating with resource record sets
(RRsets) in the DNS cryptographically generated digital signatures. (RRsets [RFC 2181]) in the DNS cryptographically generated digital
Commonly, there will be a single private key that authenticates an signatures. Commonly, there will be a single private key that
entire zone but there might be multiple keys for different authenticates an entire zone but there might be multiple keys for
algorithms, signers, etc. If a security aware resolver reliably different algorithms, signers, etc. If a security aware resolver
learns a public key of the zone, it can authenticate, for signed data reliably learns a public key of the zone, it can authenticate, for
read from that zone, that it was properly authorized and is current. signed data read from that zone, that it was properly authorized and
The most secure implementation is for the zone private key(s) to be is current. The most secure implementation is for the zone private
kept off-line and used to re-sign all of the records in the zone key(s) to be kept off-line and used to re-sign all of the records in
periodically. However, there are cases, for example dynamic update the zone periodically. However, there are cases, for example dynamic
[RFCs 2136, 2137], where DNS private keys need to be on-line. update [RFCs 2136, 2137], where DNS private keys need to be on-line.
[draft-ietf-dnssec-secops-*.txt]
This data origin authentication key(s) are associated with the zone This data origin authentication key(s) are associated with the zone
and not to the servers that store copies of the data. That means and not with the servers that store copies of the data. That means
compromise of a secondary server or, if the key(s) are kept off line, compromise of a secondary server or, if the key(s) are kept off line,
even the primary server for a zone, will not necessarily affect the even the primary server for a zone, will not necessarily affect the
degree of assurance that a resolver has that it can determine whether degree of assurance that a resolver has that it can determine whether
data is genuine. data is genuine.
A resolver could learn a public key of a zone either by reading it A resolver could learn a public key of a zone either by reading it
from the DNS or by having it or a key which authenticates it staticly from the DNS or by having it or a key which authenticates it staticly
configured. To reliably learn a public key by reading it from the configured. To reliably learn a public key by reading it from the
DNS, the key itself must be signed with a key the resolver trusts. DNS, the key itself must be signed with a key the resolver trusts.
The resolver must be configured with at least a public key which The resolver must be configured with at least a public key which
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time-to-live (TTL) field of resource records tick down while they are time-to-live (TTL) field of resource records tick down while they are
cached. cached.
This could be avoided by leaving the time-to-live out of the digital This could be avoided by leaving the time-to-live out of the digital
signature, but that would allow unscrupulous servers to set signature, but that would allow unscrupulous servers to set
arbitrarily long TTL values undetected. Instead, we include the arbitrarily long TTL values undetected. Instead, we include the
"original" TTL in the signature and communicate that data along with "original" TTL in the signature and communicate that data along with
the current TTL. Unscrupulous servers under this scheme can the current TTL. Unscrupulous servers under this scheme can
manipulate the TTL but a security aware resolver will bound the TTL manipulate the TTL but a security aware resolver will bound the TTL
value it uses at the original signed value. Separately, signatures value it uses at the original signed value. Separately, signatures
include a signature inception time and a signature expiration time. include a signature inception time and a signature expiration time. A
A resolver that knows the absolute time can determine securely resolver that knows the absolute time can determine securely whether
whether a signature is in effect. It is not possible to rely solely a signature is in effect. It is not possible to rely solely on the
on the signature expiration as a substitute for the TTL, however, signature expiration as a substitute for the TTL, however, since the
since the TTL is primarily a database consistency mechanism and non- TTL is primarily a database consistency mechanism and non-security
security aware servers that depend on TTL must still be supported. aware servers that depend on TTL must still be supported.
2.3.4 Special Considerations at Delegation Points 2.3.4 Special Considerations at Delegation Points
DNS security would like to view each zone as a unit of data DNS security would like to view each zone as a unit of data
completely under the control of the zone owner with each entry completely under the control of the zone owner with each entry
(RRset) signed by a special private key held by the zone. But the (RRset) signed by a special private key held by the zone manager.
DNS protocol views the leaf nodes in a zone, which are also the apex But the DNS protocol views the leaf nodes in a zone, which are also
nodes of a subzone (i.e., delegation points), as "really" belonging the apex nodes of a subzone (i.e., delegation points), as "really"
to the subzone. These nodes occur in two master files and might have belonging to the subzone. These nodes occur in two master files and
RRs signed by both the upper and lower zone's keys. A retrieval might have RRs signed by both the upper and lower zone's keys. A
could get a mixture of these RRs and SIGs, especially since one retrieval could get a mixture of these RRs and SIGs, especially since
server could be serving both the zone above and below a delegation one server could be serving both the zone above and below a
point. [RFC 2181] delegation point. [RFC 2181]
There MUST be a zone KEY RR, signed by its superzone, for every There MUST be a zone KEY RR, signed by its superzone, for every
subzone if the superzone is secure. In the case of an unsecured subzone if the superzone is secure. In the case of an unsecured
subzone which can not or will not be modified to add any security subzone which can not or will not be modified to add any security
RRs, a KEY declaring the subzone to be unsecured MUST appear in and RRs, a KEY declaring the subzone to be unsecured MUST appear in and
be signed by the superzone, if the superzone is secure. For all but be signed by the superzone, if the superzone is secure. For all but
one other RR type the data from the subzone is more authoritative so one other RR type the data from the subzone is more authoritative so
only the KEY RR in the superzone should be signed. The NS and any only the KEY RR in the superzone should be signed. The NS and any
glue address RRs should only be signed in the subzone. The SOA and glue address RRs should only be signed in the subzone. The SOA and
any other RRs that have the zone name as owner should appear only in any other RRs that have the zone name as owner should appear only in
the subzone and thus are signed only there. The NXT RR type is the the subzone and thus are signed only there. The NXT RR type is the
exceptional case that will always appear differently and exceptional case that will always appear differently and
authoritatively in both the superzone and subzone, if both are authoritatively in both the superzone and subzone, if both are
secure, as described in Section 5. secure, as described in Section 5.
2.3.5 Special Considerations with CNAME 2.3.5 Special Considerations with CNAME
There is a problem when security related RRs with the same owner name There is a problem when security related RRs with the same owner name
as a CNAME RR are retrieved from a non-security-aware server. In as a CNAME RR are retrieved from a non-security-aware server. In
particular, an initial retrieval for the CNAME or any other type may particular, an initial retrieval for the CNAME or any other type may
not retrieve any associated signature, KEY, or NXT RR. For retrieved not retrieve any associated SIG, KEY, or NXT RR. For retrieved types
types other than CNAME, it will retrieve that type at the target name other than CNAME, it will retrieve that type at the target name of
of the CNAME (or chain of CNAMEs) and will also return the CNAME. In the CNAME (or chain of CNAMEs) and will also return the CNAME. In
particular, a specific retrieval for type SIG will not get the SIG, particular, a specific retrieval for type SIG will not get the SIG,
if any, at the original CNAME domain name but rather a SIG at the if any, at the original CNAME domain name but rather a SIG at the
target name. target name.
Security aware servers must be used to securely CNAME in DNS. Security aware servers must be used to securely CNAME in DNS.
Security aware servers MUST (1) allow KEY, SIG, and NXT RRs along Security aware servers MUST (1) allow KEY, SIG, and NXT RRs along
with CNAME RRs, (2) suppress CNAME processing on retrieval of these with CNAME RRs, (2) suppress CNAME processing on retrieval of these
types as well as on retrieval of the type CNAME, and (3) types as well as on retrieval of the type CNAME, and (3)
automatically return SIG RRs authenticating the CNAME or CNAMEs automatically return SIG RRs authenticating the CNAME or CNAMEs
encountered in resolving a query. This is a change from the previous encountered in resolving a query. This is a change from the previous
DNS standard [RFCs 1034/1035] which prohibited any other RR type at a DNS standard [RFCs 1034/1035] which prohibited any other RR type at a
node where a CNAME RR was present. node where a CNAME RR was present.
2.3.6 Signers Other Than The Zone 2.3.6 Signers Other Than The Zone
There are cases where a SIG resource record is signed by other than a There are cases where a SIG resource record is signed by other than
private key used to authenticate a zone. one of the private key(s) used to authenticate a zone.
One is for support of dynamic update [RFC 2136] (or future requests One is for support of dynamic update [RFC 2136] (or future requests
which require secure authentication) where an entity is permitted to which require secure authentication) where an entity is permitted to
authenticate/update its records [RFC 2137]. The public key of the authenticate/update its records [RFC 2137]. The public key of the
entity must be present in the DNS and be appropriately signed but the entity must be present in the DNS and be appropriately signed but the
other RR(s) may be signed with the entity's key. other RR(s) may be signed with the entity's key.
The second case is support of transaction and request authentication A second case is support of transaction and request authentication as
as described in Section 2.4. described in Section 2.4.
In additions, signatures can be included on resource records within
the DNS for use by applications other than DNS. DNS related
signatures authenticate that data originated with the zone owner or
that a request or transaction originated with the relevant host.
Other signatures can provide other types of assurances.
2.4 DNS Transaction and Request Authentication 2.4 DNS Transaction and Request Authentication
The data origin authentication service described above protects The data origin authentication service described above protects
retrieved resource records but provides no protection for DNS retrieved resource records and the non-existence of resource records
requests or for message headers. but provides no protection for DNS requests or for message headers.
If header bits are falsely set by a bad server, there is little that If header bits are falsely set by a bad server, there is little that
can be done. However, it is possible to add transaction can be done. However, it is possible to add transaction
authentication. Such authentication means that a resolver can be authentication. Such authentication means that a resolver can be
sure it is at least getting messages from the server it thinks it sure it is at least getting messages from the server it thinks it
queried and that the response is from the query it sent (i.e., that queried and that the response is from the query it sent (i.e., that
these messages have not been diddled in transit). This is these messages have not been diddled in transit). This is
accomplished by optionally adding a special SIG resource record at accomplished by optionally adding a special SIG resource record at
the end of the reply which digitally signs the concatenation of the the end of the reply which digitally signs the concatenation of the
server's response and the resolver's query. server's response and the resolver's query.
Requests can also be authenticated by including a special SIG RR at Requests can also be authenticated by including a special SIG RR at
the end of the request. Authenticating requests serves no function the end of the request. Authenticating requests serves no function
in older DNS servers and requests with a non-empty additional in older DNS servers and requests with a non-empty additional
information section are ignored by many DNS servers. However, this information section are ignored by many of them. However, this
syntax for signing requests is defined in connection with syntax for signing requests is defined in connection with
authenticating secure dynamic update requests [RFC 2137] or future authenticating secure dynamic update requests [RFC 2137] or future
requests requiring authentication. requests requiring authentication.
The private keys used in transaction and request security belong to The private keys used in transaction security belong to the host
the host composing the request or reply, not to the zone involved. composing the reply, not to the zone involved. Request
The corresponding public key is normally stored in and retrieved from authentication may also involve the private key of the host composing
the DNS for verification. the request or other private keys depending on request authority it
is sought to establish. The corresponding public key(s) are normally
stored in and retrieved from the DNS for verification.
Because requests and replies are highly variable, message Because requests and replies are highly variable, message
authentication SIGs can not be pre-calculated. Thus it will be authentication SIGs can not be pre-calculated. Thus it will be
necessary to keep the private key on-line, for example in software or necessary to keep the private key on-line, for example in software or
in a directly connected piece of hardware. in a directly connected piece of hardware.
3. The KEY Resource Record 3. The KEY Resource Record
The KEY resource record (RR) is used to store a public key that is The KEY resource record (RR) is used to store a public key that is
associated with a Domain Name System (DNS) name. This can be the associated with a Domain Name System (DNS) name. This can be the
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RR is, like any other RR, authenticated by a SIG RR. Security aware RR is, like any other RR, authenticated by a SIG RR. Security aware
DNS implementations MUST be designed to handle at least two DNS implementations MUST be designed to handle at least two
simultaneously valid keys of the same type associated with the same simultaneously valid keys of the same type associated with the same
name. name.
The type number for the KEY RR is 25. The type number for the KEY RR is 25.
3.1 KEY RDATA format 3.1 KEY RDATA format
The RDATA for a KEY RR consists of flags, a protocol octet, the The RDATA for a KEY RR consists of flags, a protocol octet, the
algorithm number, and the public key itself. The format is as algorithm number octet, and the public key itself. The format is as
follows: follows:
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 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 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 | | flags | protocol | algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| / | /
/ public key / / public key /
/ | / /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
The KEY RR is not intended for storage of certificates and a separate The KEY RR is not intended for storage of certificates and a separate
certificate RR is being developed, to be defined in a separate certificate RR has been developed for that purpose, defined in
document. [draft-ietf-dnssec-certs-*.txt].
The meaning of the KEY RR owner name, flags, and protocol octet are The meaning of the KEY RR owner name, flags, and protocol octet are
described in Sections 3.1.1 through 3.1.5 below. The flags and described in Sections 3.1.1 through 3.1.5 below. The flags and
algorithm must be examined before any data following the algorithm algorithm must be examined before any data following the algorithm
octet as they control the existence and format of any following data. octet as they control the existence and format of any following data.
The algorithm and public key fields are described in Section 3.2. The algorithm and public key fields are described in Section 3.2.
The format of the public key is algorithm dependent. The format of the public key is algorithm dependent.
KEY RRs do not specify their validity period but their authenticating KEY RRs do not specify their validity period but their authenticating
SIG RR does as described in Section 4 below. SIG RR(s) do as described in Section 4 below.
3.1.1 Object Types, DNS Names, and Keys 3.1.1 Object Types, DNS Names, and Keys
The public key in a KEY RR is for the object named in the owner name. The public key in a KEY RR is for the object named in the owner name.
This DNS name may refer to up to three different categories of This DNS name may refer to up to three different categories of
things. For example, foo.host.example could be (1) a zone, (2) a things. For example, foo.host.example could be (1) a zone, (2) a
host or other end entity , or (3) the mapping into a DNS name of the host or other end entity , or (3) the mapping into a DNS name of the
user or account foo@host.example. Thus, there are flag bits, as user or account foo@host.example. Thus, there are flag bits, as
described below, in the KEY RR to indicate with which of these roles described below, in the KEY RR to indicate with which of these roles
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3.1.2 The KEY RR Flag Field 3.1.2 The KEY RR Flag Field
In the "flags" field: In the "flags" field:
1 1 1 1 1 1 1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| A/C | Z | XT| Z | Z | NAMTYP| Z | Z | Z | Z | SIG | | A/C | Z | XT| Z | Z | NAMTYP| Z | Z | Z | Z | SIG |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Bit 0 and 1 are the key "type" bits. Bit 0 and 1 are the key "type" bits whose values have the following
meanings:
10: Bit 0 a one indicates that use of the key is prohibited 10: Bit 0 a one indicates that use of the key is prohibited
for authentication. for authentication.
01: Bit 1 a one indicates that use of the key is prohibited 01: Bit 1 a one indicates that use of the key is prohibited
for confidentiality. for confidentiality.
00: If this field is zero, then use of the key for 00: If the bits are zero, then use of the key for
authentication and/or confidentiality is permitted. Note that DNS authentication and/or confidentiality is permitted. Note that DNS
security makes use of keys for authentication only. security makes use of keys for authentication only.
Confidentiality use flagging is provided for use of keys in other Confidentiality use flagging is provided for use of keys in other
protocols. Implementations not intended to support key protocols. Implementations not intended to support key
distribution for confidentiality MAY require that the distribution for confidentiality MAY require that the
confidentiality use prohibited bit be on for keys they serve. confidentiality use prohibited bit be on for keys they serve.
11: If both bits are one, the "no key" value, there is no key 11: If both bits are one, the "no key" value, there is no key
information and the RR stops after the algorithm octet. By the information and the RR stops after the algorithm octet. By the
use of this "no key" value, a signed KEY RR can authenticatably use of this "no key" value, a signed KEY RR can authenticatably
assert that, for example, a zone is not secured. See section 3.4 assert that, for example, a zone is not secured. See section 3.4
skipping to change at page 13, line 51 skipping to change at page 13, line 52
Bits 2 is reserved and must be zero. Bits 2 is reserved and must be zero.
Bits 3 is reserved as a flag extension bit. If it is a one, a second Bits 3 is reserved as a flag extension bit. If it is a one, a second
16 bit flag field is added after the algorithm octet and before 16 bit flag field is added after the algorithm octet and before
the key data. This bit MUST NOT be set unless one or more such the key data. This bit MUST NOT be set unless one or more such
additional bits have been defined and are non-zero. additional bits have been defined and are non-zero.
Bits 4-5 are reserved and must be zero. Bits 4-5 are reserved and must be zero.
Bits 6 and 7 form a field that encodes the name type. Bits 6 and 7 form a field that encodes the name type. Field values
have the following meanings:
0 - indicates that this is a key associated with a "user" or 0 - indicates that this is a key associated with a "user" or
"account" at an end entity, usually a host. The coding of the "account" at an end entity, usually a host. The coding of the
owner name is that used for the responsible individual mailbox in owner name is that used for the responsible individual mailbox in
the SOA and RP RRs: The owner name is the user name as the name of the SOA and RP RRs: The owner name is the user name as the name of
a node under the entity name. For example, "j_random_user" on a node under the entity name. For example, "j_random_user" on
host.subdomain.example could have a public key associated through host.subdomain.example could have a public key associated through
a KEY RR with name j_random_user.host.subdomain.example. It could a KEY RR with name j_random_user.host.subdomain.example. It could
be used in a security protocol where authentication of a user was be used in a security protocol where authentication of a user was
desired. This key might be useful in IP or other security for a desired. This key might be useful in IP or other security for a
user level service such a telnet, ftp, rlogin, etc. user level service such a telnet, ftp, rlogin, etc.
skipping to change at page 14, line 31 skipping to change at page 14, line 33
address. This is the public key used in connection with DNS address. This is the public key used in connection with DNS
request and transaction authentication services if the owner name request and transaction authentication services if the owner name
designates a DNS resolver or server host. It could also be used designates a DNS resolver or server host. It could also be used
in an IP-security protocol where authentication at the host, in an IP-security protocol where authentication at the host,
rather than user, level was desired, such as routing, NTP, etc. rather than user, level was desired, such as routing, NTP, etc.
3 - reserved. 3 - reserved.
Bits 8-11 are reserved and must be zero. Bits 8-11 are reserved and must be zero.
Bits 12-15 are the "signatory" field. If non-zero, they indicate Bits 12-15 are the "signatory" field. If non-zero, they indicate
that the key can validly sign RRs or updates of the same name in that the key can validly sign things as specified in DNS dynamic
connection with DNS dynamic update [RFC 2137]. If the owner name update [RFC 2137]. Note that zone keys (see bits 6 and 7 above)
is a wildcard, then RRs or updates with any name which is in the always have authority to sign any RRs in the zone regardless of
wildcard's scope can, in some cases, be signed. Fifteen different the value of the signatory field.
non-zero values are possible for this field and any differences in
their meaning are reserved for definition with DNS dynamic update.
Note that zone keys (see bits 6 and 7 above) always have authority
to sign any RRs in the zone regardless of the value of the
signatory field. The signatory field, like all other aspects of
the KEY RR, is only effective if the KEY RR is appropriately
signed by a SIG RR.
3.1.3 The Protocol Octet 3.1.3 The Protocol Octet
It is anticipated that keys stored in DNS will be used in conjunction It is anticipated that keys stored in DNS will be used in conjunction
with a variety of Internet protocols. It is intended that the with a variety of Internet protocols. It is intended that the
protocol octet and possibly some of the currently unused (must be protocol octet and possibly some of the currently unused (must be
zero) bits in the KEY RR flags as specified in the future will be zero) bits in the KEY RR flags as specified in the future will be
used to indicate a key's validity for different protocols. used to indicate a key's validity for different protocols.
The following values of the Protocol Octet are reserved as indicated: The following values of the Protocol Octet are reserved as indicated:
skipping to change at page 15, line 16 skipping to change at page 15, line 16
0 -reserved 0 -reserved
1 TLS 1 TLS
2 email 2 email
3 dnssec 3 dnssec
4 IPSEC 4 IPSEC
5-254 -available for assignment by IANA 5-254 -available for assignment by IANA
255 All 255 All
In more detail: In more detail:
1 is reserved to refer to the TLS standard being developed by 1 is reserved to refer to the TLS standard. The presence of a
the tls working group. The presence of a KEY resource with this KEY resource with this protocol value is an assertion that the host
protocol value is an assertion that the host speaks TLS. speaks TLS.
2 is reserved for use in connection with email. 2 is reserved for use in connection with email.
3 is used for DNS security. The protocol field should be set to 3 is used for DNS security. The protocol field should be set to
this value for zone keys and other keys used in DNS security. this value for zone keys and other keys used in DNS security.
Implementations that can determine that a key is a DNS security key Implementations that can determine that a key is a DNS security key
by the fact that flags label it a zone key or the signatory flag by the fact that flags label it a zone key or the signatory flag
field is non-zero are not required to check the protocol field. field is non-zero are NOT REQUIRED to check the protocol field.
4 is reserved to refer to the Oakley/IPSEC [RFC 1825] protocol 4 is reserved to refer to the Oakley/IPSEC [RFC 1825] protocol
and indicates that this key is valid for use in conjunction with that and indicates that this key is valid for use in conjunction with that
security standard. This key could be used in connection with secured security standard. This key could be used in connection with secured
communication on behalf of an end entity or user whose name is the communication on behalf of an end entity or user whose name is the
owner name of the KEY RR if the entity or user bits are on. The owner name of the KEY RR if the entity or user bits are on. The
presence of a KEY resource with this protocol value is an assertion presence of a KEY resource with this protocol value is an assertion
that the host speaks Oakley/IPSEC. that the host speaks Oakley/IPSEC.
255 indicates that the key can be used in connection with any 255 indicates that the key can be used in connection with any
protocol for which KEY RR protocol octet values have been defined. protocol for which KEY RR protocol octet values have been defined.
The use of this value is discouraged and the use of different keys The use of this value is discouraged and the use of different keys
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3.2 The KEY Algorithm Number Specification 3.2 The KEY Algorithm Number Specification
This octet is the key algorithm parallel to the same field for the This octet is the key algorithm parallel to the same field for the
SIG resource as described in Section 4.1. The following values are SIG resource as described in Section 4.1. The following values are
assigned: assigned:
VALUE Protocol VALUE Protocol
0 - reserved 0 - reserved
1 RSA/MD5 [RFC xxx1] - recommended 1 RSA/MD5 [draft-ietf-dnssec-rsa-*.txt] - recommended
2 Diffie-Hellman [RFC xxx2] - key only 2 Diffie-Hellman [draft-ietf-dnssec-dhk-*.txt] - key only
3 DSA [RFC xxx3] - MANDATORY 3 DSA [draft-ietf-dnssec-dss-*.txt] - MANDATORY
4 reserved for elliptic curve 4 reserved for elliptic curve
5-251 - available (see below) 5-251 - available (see below)
252 indirect keys [RFC xxx4] 252 reserved for indirect keys
253 - available (but was "null" [RFC 2065]) 253 - available (but was "null" [RFC 2065])
254 private (see below) 254 private (see below)
255 - reserved 255 - reserved
Algorithm specific formats and procedures are given in separate Algorithm specific formats and procedures are given in separate
documents. The mandatory to implement for interoperability algorithm documents. The mandatory to implement for interoperability algorithm
is number 3, DSA. It is recommended that the RSA/MD5 algorithm, is number 3, DSA. It is recommended that the RSA/MD5 algorithm,
number 1, also be implemented. Algorithm 2 is used to indicate number 1, also be implemented. Algorithm 2 is used to indicate
Diffie-Hellman keys and algorithm 4 is reserved for elliptic curve. Diffie-Hellman keys and algorithm 4 is reserved for elliptic curve.
Numbers 5 through 251 and 253 are available for assignment should Numbers 5 through 251 and 253 are available for assignment should
sufficient reason arise. However, the designation of a new algorithm sufficient reason arise. However, the designation of a new algorithm
could have a major impact on interoperability and requires an IETF could have a major impact on interoperability and requires an IETF
standards action. standards action.
Number 252 is reserved for the definition of an indirect key format
where they actual key material is elsewhere.
Number 254 is reserved for private use and will never be assigned a Number 254 is reserved for private use and will never be assigned a
specific algorithm. For number 254, the public key area for the KEY specific algorithm. For number 254, the public key area for the KEY
RR and the signature will actually begin with a length byte followed RR and the signature will actually begin with a length byte followed
by an Object Identifier (ISO OID) of that length. The OID indicates by an Object Identifier (ISO OID) of that length. The OID indicates
the private algorithm in use and the remainder of the area is the private algorithm in use and the remainder of the area is
whatever is required by that algorithm. whatever is required by that algorithm.
Values 0 and 255 are reserved but the value 0 is used in the Values 0 and 255 are reserved but the value 0 is used in the
algorithm field when that field is not used. An example is in a KEY algorithm field when that field is not used. An example is in a KEY
RR with the top two flag bits on, the "no-key" value, where no key is RR with the top two flag bits on, the "no-key" value, where no key is
present. Such a KEY RR should have an algorithm field of zero. present.
3.3 Interaction of Flags, Algorithm, and Protocol Bytes 3.3 Interaction of Flags, Algorithm, and Protocol Bytes
Various combinations of the no-key type flags, algorithm byte, Various combinations of the no-key type flags, algorithm byte,
protocol byte, and any future assigned protocol indicating flags are protocol byte, and any future assigned protocol indicating flags are
possible. The meaning of these combinations is indicated below: possible. The meaning of these combinations is indicated below:
NK = no key type flags (bits 0 and 1 on) NK = no key type (flags bits 0 and 1 on)
AL = algorithm byte AL = algorithm byte
PR = protocols indicated by protocol byte or future assigned flags PR = protocols indicated by protocol byte or future assigned flags
x represents any valid non-zero value(s). x represents any valid non-zero value(s).
AL PR NK Meaning AL PR NK Meaning
0 0 0 Illegal, claims key but has bad algorithm field. 0 0 0 Illegal, claims key but has bad algorithm field.
0 0 1 Specifies total lack of security for owner zone. 0 0 1 Specifies total lack of security for owner zone.
0 x 0 Illegal, claims key but has bad algorithm field. 0 x 0 Illegal, claims key but has bad algorithm field.
0 x 1 Specified protocols unsecured, others may be secure. 0 x 1 Specified protocols unsecured, others may be secure.
x 0 0 Useless. Gives key but no protocols to use it. x 0 0 Gives key but no protocols to use it.
x 0 1 Useless. Denies key but for no protocols. x 0 1 Denies key for specific algorithm.
x x 0 Specifies key for protocols. x x 0 Specifies key for protocols.
x x 1 Algorithm not understood for protocol. x x 1 Algorithm not understood for protocol.
3.4 Determination of Zone Secure/Unsecured Status 3.4 Determination of Zone Secure/Unsecured Status
A zone KEY RR with the "no-key" type field value (both bits 0 and 1 A zone KEY RR with the "no-key" type field value (both key type flag
on) indicates that the zone named is unsecured while a zone KEY RR bits 0 and 1 on) indicates that the zone named is unsecured while a
with a key present indicates that the zone named is secure. It is zone KEY RR with a key present indicates that the zone named is
possible for conflicting zone KEY RRs to be present. secure. The secured versus unsecured status of a zone may vary with
different cryptographic algorithms. Even for the same algorithm,
conflicting zone KEY RRs may be present.
Zone KEY RRs, like all RRs, are only trusted if they are Zone KEY RRs, like all RRs, are only trusted if they are
authenticated by a SIG RR whose signer field is a signer for which authenticated by a SIG RR whose signer field is a signer for which
the resolver has a public key they trust and where resolver policy the resolver has a public key they trust and where resolver policy
permits that signer to sign for the KEY owner name. Untrusted zone permits that signer to sign for the KEY owner name. Untrusted zone
KEY RRs MUST be ignored in determining the security status of the KEY RRs MUST be ignored in determining the security status of the
zone. However, there can be multiple sets of trusted zone KEY RRs zone. However, there can be multiple sets of trusted zone KEY RRs
for a zone with different algorithms, signers, etc. for a zone with different algorithms, signers, etc.
Zones can be (1) secure, indicating that any retrieved RR must be For any particular algorithm, zones can be (1) secure, indicating
authenticated by a SIG RR or it will be discarded as bogus, (2) that any retrieved RR must be authenticated by a SIG RR or it will be
unsecured, indicating that SIG RRs are not expected or required for discarded as bogus, (2) unsecured, indicating that SIG RRs are not
RRs retrieved from the zone, or (3) experimentally secure, which expected or required for RRs retrieved from the zone, or (3)
indicates that SIG RRs might or might not be present but must be experimentally secure, which indicates that SIG RRs might or might
checked if found. The status of a zone is determined as follows: not be present but must be checked if found. The status of a zone is
determined as follows:
1. If, for a zone, every trusted zone KEY RR for the zone says there 1. If, for a zone and algorithm, every trusted zone KEY RR for the
is no key for that zone, it is unsecured. zone says there is no key for that zone, it is unsecured for that
algorithm.
2. If, there is at least one trusted no-key zone KEY RR and one 2. If, there is at least one trusted no-key zone KEY RR and one
trusted key specifying zone KEY RR, then that zone is only trusted key specifying zone KEY RR, then that zone is only
experimentally secure. Both authenticated and non-authenticated experimentally secure for the algorithm. Both authenticated and
RRs for it should be accepted by the resolver. non-authenticated RRs for it should be accepted by the resolver.
3. If every trusted zone KEY RR for the zone has is key specifying, 3. If every trusted zone KEY RR that the zone and algorithm has is
then it is secure and only authenticated RRs from it will be key specifying, then it is secure for that algorithm and only
accepted. authenticated RRs from it will be accepted.
Examples: Examples:
(1) A resolver only trusts signatures by the superzone within the (1) A resolver only trusts signatures by the superzone within the
DNS hierarchy so it will look only at the KEY RRs that are signed by DNS hierarchy so it will look only at the KEY RRs that are signed by
the superzone. If it finds only no-key KEY RRs, it will assume the the superzone. If it finds only no-key KEY RRs, it will assume the
zone is not secure. If it finds only key specifying KEY RRs, it will zone is not secure. If it finds only key specifying KEY RRs, it will
assume the zone is secure and reject any unsigned responses. If it assume the zone is secure and reject any unsigned responses. If it
finds both, it will assume the zone is experimentally secure finds both, it will assume the zone is experimentally secure
(2) A resolver trusts the superzone of zone Z (to which it got (2) A resolver trusts the superzone of zone Z (to which it got
securely from its local zone) and a third party, cert-auth.xy. When securely from its local zone) and a third party, cert-auth.xy. When
considering data from zone Z, it may be signed by the superzone of Z, considering data from zone Z, it may be signed by the superzone of Z,
by cert-auth.xy, by both, or by neither. The following table by cert-auth.xy, by both, or by neither. The following table
indicates whether zone Z will be considered secure, experimentally indicates whether zone Z will be considered secure, experimentally
secure, or unsecured, depending on the signed zone KEY RRs for Z; secure, or unsecured, depending on the signed zone KEY RRs for Z;
c e r t - a u t h . x y c e r t - a u t h . x y
| None | NoKeys | Mixed | Keys | KEY RRs| None | NoKeys | Mixed | Keys |
S --+-----------+-----------+----------+----------+ S --+-----------+-----------+----------+----------+
u None | illegal | unsecured | experim. | secure | u None | illegal | unsecured | experim. | secure |
p +-----------+-----------+----------+----------+ p --+-----------+-----------+----------+----------+
e NoKeys | unsecured | unsecured | experim. | secure | e NoKeys | unsecured | unsecured | experim. | secure |
r +-----------+-----------+----------+----------+ r --+-----------+-----------+----------+----------+
Z Mixed | experim. | experim. | experim. | secure | Z Mixed | experim. | experim. | experim. | secure |
o +-----------+-----------+----------+----------+ o --+-----------+-----------+----------+----------+
n Keys | secure | secure | secure | secure | n Keys | secure | secure | secure | secure |
e +-----------+-----------+----------+----------+ e +-----------+-----------+----------+----------+
3.5 KEY RRs in the Construction of Responses 3.5 KEY RRs in the Construction of Responses
An explicit request for KEY RRs does not cause any special additional An explicit request for KEY RRs does not cause any special additional
information processing except, of course, for the corresponding SIG information processing except, of course, for the corresponding SIG
RR from a security aware server (see Section 4.2). RR from a security aware server (see Section 4.2).
Security aware DNS servers include KEY RRs as additional information Security aware DNS servers include KEY RRs as additional information
in responses, where a KEY is available, in the following cases: in responses, where a KEY is available, in the following cases:
(1) On the retrieval of SOA or NS RRs, the KEY RRset with the same (1) On the retrieval of SOA or NS RRs, the KEY RRset with the same
name (usually just a zone key) SHOULD be included as additional name (usually just a zone key) SHOULD be included as additional
information if space is available. There will always be at least one information if space is available. There will always be at least one
such KEY RR in a secure zone in connection with a subzone delegation such KEY RR in a secure zone in connection with each subzone
point, even if it has the no-key type value to indicate that the delegation point, even if it has the no-key type value to indicate
subzone is unsecured. If not all additional information will fit, that the subzone is unsecured. If not all additional information
type A and AAAA glue RRs have higher priority than KEY RR(s). will fit, type A and AAAA glue RRs have higher priority than KEY
RR(s).
(2) On retrieval of type A or AAAA RRs, the KEY RRset with the same (2) On retrieval of type A or AAAA RRs, the KEY RRset with the same
name (usually just a host RR and NOT the zone key which usually would name (usually just a host RR and NOT the zone key which usually would
have a different name) SHOULD be included if space is available. On have a different name) SHOULD be included if space is available. On
inclusion of A or AAAA RRs as additional information, the KEY RRset inclusion of A or AAAA RRs as additional information, the KEY RRset
with the same name should also be included but with lower priority with the same name should also be included but with lower priority
than the A or AAAA RRs. than the A or AAAA RRs.
4. The SIG Resource Record 4. The SIG Resource Record
The SIG or "signature" resource record (RR) is the fundamental way The SIG or "signature" resource record (RR) is the fundamental way
that data is authenticated in the secure Domain Name System (DNS). As that data is authenticated in the secure Domain Name System (DNS). As
such it is the heart of the security provided. such it is the heart of the security provided.
The SIG RR unforgably authenticates an RRset of a particular type, The SIG RR unforgably authenticates an RRset [RFC 2181] of a
class, and name and binds it to a time interval and the signer's particular type, class, and name and binds it to a time interval and
domain name. This is done using cryptographic techniques and the the signer's domain name. This is done using cryptographic
signer's private key. The signer is frequently the owner of the zone techniques and the signer's private key. The signer is frequently
from which the RR originated. The SIG RR is only intended to be the owner of the zone from which the RR originated.
meaningful to DNS security.
The type number for the SIG RR type is 24. The type number for the SIG RR type is 24.
4.1 SIG RDATA Format 4.1 SIG RDATA Format
The RDATA portion of a SIG RR is as shown below. The integrity of The RDATA portion of a SIG RR is as shown below. The integrity of
the RDATA information is protected by the signature field. the RDATA information is protected by the signature field.
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 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 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
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The "original TTL" field is included in the RDATA portion to avoid The "original TTL" field is included in the RDATA portion to avoid
(1) authentication problems that caching servers would otherwise (1) authentication problems that caching servers would otherwise
cause by decrementing the real TTL field and (2) security problems cause by decrementing the real TTL field and (2) security problems
that unscrupulous servers could otherwise cause by manipulating the that unscrupulous servers could otherwise cause by manipulating the
real TTL field. This original TTL is protected by the signature real TTL field. This original TTL is protected by the signature
while the current TTL field is not. while the current TTL field is not.
NOTE: The "original TTL" must be restored into the covered RRs when NOTE: The "original TTL" must be restored into the covered RRs when
the signature is verified (see Section 8). This implies that all RRs the signature is verified (see Section 8). This implies that all RRs
for a particular type, name, and class must have the same TTL to for a particular type, name, and class, that is, all the RRs in any
start with. particular RRset, must have the same TTL to start with.
4.1.5 Signature Expiration and Inception Fields 4.1.5 Signature Expiration and Inception Fields
The SIG is valid from the "signature inception" time until the The SIG is valid from the "signature inception" time until the
"signature expiration" time. Both are unsigned numbers of seconds "signature expiration" time. Both are unsigned numbers of seconds
since the start of 1 January 1970, GMT, ignoring leap seconds. (See since the start of 1 January 1970, GMT, ignoring leap seconds. (See
also Section 4.4.) Ring arithmetic is used as for DNS SOA serial also Section 4.4.) Ring arithmetic is used as for DNS SOA serial
numbers [RFC 1982] which means that these times can never be more numbers [RFC 1982] which means that these times can never be more
than about 136.09 years in the future. than about 136.09 years in the future. A SIG RR may have an
expiration time numerically less than the inception time if the
expiration time is near the 32 bit wrap around point and/or the
signature is long lived.
(To prevent misordering of network requests to update a zone (To prevent misordering of network requests to update a zone
dynamically, monotonically increasing "signature inception" times may dynamically, monotonically increasing "signature inception" times may
be necessary. [RFC 2137]) be necessary. [RFC 2137])
SOA serial numbers for secure zones MUST not only be advanced when SOA serial numbers for secure zones MUST not only be advanced when
their data is updated but also when new SIG RRs are inserted (ie, the their data is updated but also when new SIG RRs are inserted (ie, the
zone or any part of it is re-signed). zone or any part of it is re-signed).
A SIG RR may have an expiration time numerically less than the time
signed if time is near the 32 bit wrap around point and/or the
signature is long lived.
4.1.6 Key Tag Field 4.1.6 Key Tag Field
The "key Tag" is a two octet quantity that is used to efficiently The "key Tag" is a two octet quantity that is used to efficiently
select between multiple keys which may be applicable and thus check select between multiple keys which may be applicable and thus check
that a public key about to be used for the computationally expensive that a public key about to be used for the computationally expensive
effort to check the signature is possibly valid. For algorithm 1 effort to check the signature is possibly valid. For algorithm 1
(MD5/RSA) as defined in [RFC xxx1], it is the next to the bottom two (MD5/RSA) as defined in [draft-ietf-dnssec-rsa-*.txt], it is the next
octets of the public key modulus needed to decode the signature to the bottom two octets of the public key modulus needed to decode
field. That is to say, the most significant 16 of the lest the signature field. That is to say, the most significant 16 of the
significant 24 bits of the modulus in network (big endian) order. least significant 24 bits of the modulus in network (big endian)
For all other algorithms, including private algorithms, it is order. For all other algorithms, including private algorithms, it is
calculated as a simple checksum of the KEY RR as described in calculated as a simple checksum of the KEY RR as described in
Appendix C. Appendix C.
4.1.7 Signer's Name Field 4.1.7 Signer's Name Field
The "signer's name" field is the domain name of the signer generating The "signer's name" field is the domain name of the signer generating
the SIG RR. This is the owner of the public KEY RR that can be used the SIG RR. This is the owner name of the public KEY RR that can be
to verify the signature. It is frequently the zone which contained used to verify the signature. It is frequently the zone which
the RRset being authenticated. Which signers should be authorized to contained the RRset being authenticated. Which signers should be
sign what is a significant resolver policy question as discussed in authorized to sign what is a significant resolver policy question as
Section 6. The signer's name may be compressed with standard DNS name discussed in Section 6. The signer's name may be compressed with
compression when being transmitted over the network. standard DNS name compression when being transmitted over the
network.
4.1.8 Signature Field 4.1.8 Signature Field
The structure of the "signature" field is described below. The structure of the "signature" field is described below.
The actual signature portion of the SIG RR binds the other RDATA The actual signature portion of the SIG RR binds the other RDATA
fields to the RRset of the "type covered" RRs with that owner name fields to the RRset of the "type covered" RRs with that owner name
and class. This covered RRset is thereby authenticated. To and class. This covered RRset is thereby authenticated. To
accomplish this, a data sequence is constructed as follows: accomplish this, a data sequence is constructed as follows:
data = RDATA | RR(s)... data = RDATA | RR(s)...
where "|" is concatenation, RDATA is wire format of all the RDATA where "|" is concatenation,
fields in the SIG RR itself including the canonical form of the
signers name before but not including the signature, and RR(s) is the RDATA is the wire format of all the RDATA fields in the SIG RR itself
RRset of the RR(s) of the type covered with the same owner name and (including the canonical form of the signer's name) before but not
class as the SIG RR in canonical form and order as defined in Section including the signature, and
8. How this data sequence is processed into the signature is
algorithm dependent. These algorithm dependent formats and RR(s) is the RRset of the RR(s) of the type covered with the same
procedures are described in separate documents (Section 3.2). owner name and class as the SIG RR in canonical form and order as
defined in Section 8.
How this data sequence is processed into the signature is algorithm
dependent. These algorithm dependent formats and procedures are
described in separate documents (Section 3.2).
SIGs SHOULD NOT be included in a zone for any "meta-type" such as SIGs SHOULD NOT be included in a zone for any "meta-type" such as
ANY, AXFR, etc. ANY, AXFR, etc. (but see section 5.6.2 with regard to IXFR).
4.1.8.1 Calculating Transaction and Request SIGs 4.1.8.1 Calculating Transaction and Request SIGs
A response message from a security aware server may optionally A response message from a security aware server may optionally
contain a special SIG at the end of the additional information contain a special SIG at the end of the additional information
section to authenticate the transaction. section to authenticate the transaction.
This SIG has a "type covered" field of zero, which is not a valid RR This SIG has a "type covered" field of zero, which is not a valid RR
type. It is calculated by using a "data" (see Section 4.1.8) of the type. It is calculated by using a "data" (see Section 4.1.8) of the
entire preceding DNS reply message, including DNS header but not the entire preceding DNS reply message, including DNS header but not the
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Security aware DNS servers SHOULD, for every authenticated RR the Security aware DNS servers SHOULD, for every authenticated RR the
query will return, attempt to send the available SIG RRs which query will return, attempt to send the available SIG RRs which
authenticate the requested RR. The following rules apply to the authenticate the requested RR. The following rules apply to the
inclusion of SIG RRs in responses: inclusion of SIG RRs in responses:
1. when an RRset is placed in a response, its SIG RR has a higher 1. when an RRset is placed in a response, its SIG RR has a higher
priority for inclusion than additional RRs that may need to be priority for inclusion than additional RRs that may need to be
included. If space does not permit its inclusion, the response included. If space does not permit its inclusion, the response
MUST be considered truncated except as provided in 2 below. MUST be considered truncated except as provided in 2 below.
2. when a SIG RR is present in the zone for an additional 2. When a SIG RR is present in the zone for an additional
information section RR, the response MUST NOT be considered information section RR, the response MUST NOT be considered
truncated merely because space does not permit the inclusion of truncated merely because space does not permit the inclusion of
its SIG RR. the SIG RR with the additional information.
3. SIGs to authenticate non-authoritative data (glue records and NS 3. SIGs to authenticate non-authoritative data (glue records and NS
RRs for subzones) are unnecessary and MUST NOT be sent. (Note RRs for subzones) are unnecessary and MUST NOT be sent. (Note
that KEYs given for a subzone in that subzone's superzone are that KEYs given for a subzone in that subzone's superzone are
controlling so the superzone's signature on the KEY MUST be controlling so the superzone's signature on the KEY MUST be
included (unless the KEY was additional information and the SIG included (unless the KEY was additional information and the SIG
did not fit).) did not fit).)
4. If a SIG covers any RR that would be in the answer section of 4. If a SIG covers any RR that would be in the answer section of
the response, its automatic inclusion MUST be in the answer the response, its automatic inclusion MUST be in the answer
skipping to change at page 24, line 5 skipping to change at page 25, line 10
section, its automatic inclusion MUST be in the authority section, its automatic inclusion MUST be in the authority
section. If it covers an RR that would appear in the additional section. If it covers an RR that would appear in the additional
information section it MUST appear in the additional information information section it MUST appear in the additional information
section. This is a change in the existing standard [RFCs 1034, section. This is a change in the existing standard [RFCs 1034,
1035] which contemplates only NS and SOA RRs in the authority 1035] which contemplates only NS and SOA RRs in the authority
section. section.
5. Optionally, DNS transactions may be authenticated by a SIG RR at 5. Optionally, DNS transactions may be authenticated by a SIG RR at
the end of the response in the additional information section the end of the response in the additional information section
(Section 4.1.8.1). Such SIG RRs are signed by the DNS server (Section 4.1.8.1). Such SIG RRs are signed by the DNS server
originating the response. Although the signer field MUST be the originating the response. Although the signer field MUST be a
name of the originating server host, the owner name, class, TTL, name of the originating server host, the owner name, class, TTL,
and original TTL, are meaningless. The class and TTL fields and original TTL, are meaningless. The class and TTL fields
SHOULD be zero. To conserve space, the owner name SHOULD be SHOULD be zero. To conserve space, the owner name SHOULD be
root (a single zero octet). If transaction authentication is root (a single zero octet). If transaction authentication is
desired, that SIG RR must be considered the highest priority for desired, that SIG RR must be considered the highest priority for
inclusion. inclusion.
4.3 Processing Responses and SIG RRs 4.3 Processing Responses and SIG RRs
The following rules apply to the processing of SIG RRs included in a The following rules apply to the processing of SIG RRs included in a
response: response:
1. a security aware resolver that receives a response from a 1. A security aware resolver that receives a response from a
security aware server via a secure communication with the AD bit security aware server via a secure communication with the AD bit
(see Section 6.1) set, MAY choose to accept the RRs as received (see Section 6.1) set, MAY choose to accept the RRs as received
without verifying the zone SIG RRs. without verifying the zone SIG RRs.
2. in other cases, a security aware resolver SHOULD verify the SIG 2. In other cases, a security aware resolver SHOULD verify the SIG
RRs for the RRs of interest. This may involve initiating RRs for the RRs of interest. This may involve initiating
additional queries for SIG or KEY RRs, especially in the case of additional queries for SIG or KEY RRs, especially in the case of
getting a response from an server that does not implement getting a response from an server that does not implement
security. (As explained in 2.3.5 above, it will not be possible security. (As explained in 2.3.5 above, it will not be possible
to secure CNAMEs being served up by non-secure resolvers.) to secure CNAMEs being served up by non-secure resolvers.)
NOTE: Implementers might expect the above SHOULD to be a MUST. NOTE: Implementers might expect the above SHOULD to be a MUST.
However, local policy or the calling application may not require However, local policy or the calling application may not require
the security services. the security services.
skipping to change at page 24, line 47 skipping to change at page 26, line 4
If the message does not pass integrity checks or the SIG does not If the message does not pass integrity checks or the SIG does not
check against the signed RRs, the SIG RR is invalid and should be check against the signed RRs, the SIG RR is invalid and should be
ignored. If all of the SIG RR(s) purporting to authenticate an RRset ignored. If all of the SIG RR(s) purporting to authenticate an RRset
are invalid, then the RRset is not authenticated. are invalid, then the RRset is not authenticated.
If the SIG RR is the last RR in a response in the additional If the SIG RR is the last RR in a response in the additional
information section and has a type covered of zero, it is a information section and has a type covered of zero, it is a
transaction signature of the response and the query that produced the transaction signature of the response and the query that produced the
response. It MAY be optionally checked and the message rejected if response. It MAY be optionally checked and the message rejected if
the checks fail. But even if the checks succeed, such a transaction the checks fail. But even if the checks succeed, such a transaction
authentication SIG does NOT authenticate any RRs in the message. authentication SIG does NOT directly authenticate any RRs in the
Only a proper SIG RR signed by the zone or a key tracing its message. Only a proper SIG RR signed by the zone or a key tracing
authority to the zone or to static resolver configuration can its authority to the zone or to static resolver configuration can
authenticate RRs depending on resolver policy (see Section 6). If a directly authenticate RRs, depending on resolver policy (see Section
resolver does not implement transaction and/or request SIGs, it MUST 6). If a resolver does not implement transaction and/or request
ignore them without error. SIGs, it MUST ignore them without error.
If all checks indicate that the SIG RR is valid then RRs verified by If all checks indicate that the SIG RR is valid then RRs verified by
it should be considered authenticated. it should be considered authenticated.
4.4 Signature Lifetime, Expiration, TTLs, and Validity 4.4 Signature Lifetime, Expiration, TTLs, and Validity
Security aware servers MUST NOT consider SIG RRs to authenticate Security aware servers MUST NOT consider SIG RRs to authenticate
anything before their signature inception or after its expiration anything before their signature inception or after its expiration
time. (Actually after the authentication chain expiration time, see time (see also Section 6). Security aware servers MUST NOT consider
Section 6.) Security aware servers MUST NOT consider any RR to be any RR to be authenticated after all its signatures have expired.
authenticated after all its signatures have expired. When a secure When a secure server caches authenticated data, if the TTL would
server caches authenticated data, if the TTL would expire at a time expire at a time further in the future than the authentication
further in the future than the authentication expiration time, the expiration time, the server SHOULD trim the TTL in the cache entry
server SHOULD trim the TTL in the cache entry not to extent beyond not to extent beyond the authentication expiration time. Within
the authentication expiration time. Within these constraint, servers these constraints, servers should continue to follow DNS TTL aging.
should continue to follow DNS TTL aging. Thus authoritative servers Thus authoritative servers should continue to follow the zone refresh
should continue to follow the zone refresh and expire parameters and and expire parameters and a non-authoritative server should count
a non-authoritative server should count down the TTL and discard RRs down the TTL and discard RRs when the TTL is zero (even for a SIG
when the TTL is zero (even for a SIG that has not yet reached its that has not yet reached its authentication expiration time). In
authentication expiration time). In addition, when RRs are addition, when RRs are transmitted in a query response, the TTL
transmitted in a query response, the TTL should be trimmed so that should be trimmed so that current time plus the TTL does not extend
current time plus the TTL does not extend beyond the authentication beyond the authentication expiration time. Thus, in general, the TTL
expiration time. Thus, in general, the TTL on a transmitted RR would on a transmitted RR would be
be
min(authExpTim,max(zoneMinTTL,min(originalTTL,currentTTL))) min(authExpTim,max(zoneMinTTL,min(originalTTL,currentTTL)))
When signatures are generated, signature expiration times should be When signatures are generated, signature expiration times should be
set far enough in the future that it is quite certain that new set far enough in the future that it is quite certain that new
signatures can be generated before the old ones expire. However, signatures can be generated before the old ones expire. However,
setting expiration too far into the future could, if bad data or setting expiration too far into the future could mean a long time to
signatures were ever generated, mean a long time to flush such flush any bad data or signatures that may have been generated.
badness.
It is recommended that signature lifetime be a small multiple of the It is recommended that signature lifetime be a small multiple of the
TTL (ie, 4 to 16 times the TTL) but not less than a reasonable TTL (ie, 4 to 16 times the TTL) but not less than a reasonable
maximum re-signing interval and not less than the zone expiry time. maximum re-signing interval and not less than the zone expiry time.
4.5 SIG Under The Meta-Root Key and The Root Zone
To minimize exposure of the ultimate key of the DNS tree, there will
be a "meta-root" key used rarely and then only to sign a sequence of
regular root key RRsets with overlapping time validity periods that
are to be rolled out. The root zone contains the meta-root and
current regular root KEY RR(s) signed by SIG RRs under both the
meta-root and other root key(s) themselves.
For example, assume that the regular root key is to be changed once a
month. If the meta-root key were to be exposed only once a year,
then for each exposure you might use the meta-key to sign twenty four
key RRsets as follows:
one with a date signed of the middle of January and expiring the
middle of February with the January and Jan/Feb root keys,
one with a date signed of the beginning of February and expiring
the end of February with the Jan/Feb and February root keys,
one with a date signed of the middle of February and expiring
the middle of March with the February and Feb/Mar root keys,
one with the data signed of the beginning of March and expiring
the end of March with with Feb/Mar and March root keys,
etc.
During the first half of January, the data in the root zone with the
above hypothetical key policy would be signed with the Dec/Jan and
January keys. During the second half of January, it would be signed
with the January and Jan/Feb keys. During the first half of
February, it would be signed with the Jan/Feb and February keys. Etc.
Security in the storage and use of the meta-root key should be
maximized. The particular techniques are precautions to be used are
an operational matter beyond the scope of this document.
It should also be noted that in DNS the root is a single level zone
unto itself. Thus the root zone key should only be seen signing
itself or signing RRs with names one level below root, such as .aq,
.com, or signature of records with a name more than one level below
root.
5. Non-existent Names and Types 5. Non-existent Names and Types
The SIG RR mechanism described in Section 4 above provides strong The SIG RR mechanism described in Section 4 above provides strong
authentication of RRs that exist in a zone. But is it not clear authentication of RRs that exist in a zone. But is it not clear
above how to verifiably deny the existence of a name in a zone or a above how to verifiably deny the existence of a name in a zone or a
type for an existent name. type for an existent name.
The nonexistence of a name in a zone is indicated by the NXT ("next") The nonexistence of a name in a zone is indicated by the NXT ("next")
RR for a name interval containing the nonexistent name. An NXT RR or RR for a name interval containing the nonexistent name. An NXT RR or
RRs and its or their SIG(s) are returned in the authority section, RRs and its or their SIG(s) are returned in the authority section,
skipping to change at page 27, line 36 skipping to change at page 27, line 36
signed RR unless it is a query for delegation point NS or glue A or signed RR unless it is a query for delegation point NS or glue A or
AAAA RRs. AAAA RRs.
5.1 The NXT Resource Record 5.1 The NXT Resource Record
The NXT resource record is used to securely indicate that RRs with an The NXT resource record is used to securely indicate that RRs with an
owner name in a certain name interval do not exist in a zone and to owner name in a certain name interval do not exist in a zone and to
indicate what RR types are present for an existing name. indicate what RR types are present for an existing name.
The owner name of the NXT RR is an existing name in the zone. It's The owner name of the NXT RR is an existing name in the zone. It's
RDATA is a "next" name and a type bit map. The presence of the NXT RR RDATA is a "next" name and a type bit map. Thus the NXT RRs in a zone
means that no name between its owner name and the name in its RDATA create a chain of all of the literal owner names in that zone,
area exists and that no other types exist under its owner name. This including unexpanded wildcard but omitting the owner name of glue
implies a canonical ordering of all domain names in a zone as address records unless they would otherwise be included. This implies
described in Section 8. a canonical ordering of all domain names in a zone as described in
Section 8. The presence of the NXT RR means that no name between its
owner name and the name in its RDATA area exists and that no other
types exist under its owner name.
There is a potential problem with the last NXT in a zone as it wants There is a potential problem with the last NXT in a zone as it wants
to have an owner name which is the last existing name in canonical to have an owner name which is the last existing name in canonical
order, which is easy, but it is not obvious what name to put in its order, which is easy, but it is not obvious what name to put in its
RDATA to indicate the entire remainder of the name space. This is RDATA to indicate the entire remainder of the name space. This is
handled by treating the name space as circular and putting the zone handled by treating the name space as circular and putting the zone
name in the RDATA of the last NXT in a zone. name in the RDATA of the last NXT in a zone.
The NXT RRs for a zone SHOULD be automatically calculated and added The NXT RRs for a zone SHOULD be automatically calculated and added
to the zone when SIGs are added. The NXT RR's TTL SHOULD NOT exceed to the zone when SIGs are added. The NXT RR's TTL SHOULD NOT exceed
skipping to change at page 28, line 29 skipping to change at page 28, line 31
The NXT RR type bit map format currently defined is one bit per RR The NXT RR type bit map format currently defined is one bit per RR
type present for the owner name similar to the WKS RR socket bit map. type present for the owner name similar to the WKS RR socket bit map.
A one bit indicates that at least one RR of that type is present for A one bit indicates that at least one RR of that type is present for
the owner name. A zero indicates that no such RR is present. All the owner name. A zero indicates that no such RR is present. All
bits not specified because they are beyond the end of the bit map are bits not specified because they are beyond the end of the bit map are
assumed to be zero. Note that bit 30, for NXT, will always be on so assumed to be zero. Note that bit 30, for NXT, will always be on so
the minimum bit map length is actually four octets. Trailing zero the minimum bit map length is actually four octets. Trailing zero
octets are prohibited in this format. The first bit represents RR octets are prohibited in this format. The first bit represents RR
type zero (an illegal type which can not be present) and so will be type zero (an illegal type which can not be present) and so will be
zero in this format. This format must be used unless there are RRs zero in this format. This format is not used if there exists an RR
with a type number greater than 127. If the zero bit of the type bit with a type number greater than 127. If the zero bit of the type bit
map is a one, it indicates that there exists at least on RR with a map is a one, it indicates that a different format is being used
type number greater than 127 and a different format is in use which which will always be the case if a type number greater than 127 is
is to be defined. present.
The NXT bit map should be printed as a list of RR type mnemonics or
decimal numbers similar to the WKS RR.
The domain name may be compressed with standard DNS name compression The domain name may be compressed with standard DNS name compression
when being transmitted over the network. The size of the bit map can when being transmitted over the network. The size of the bit map can
be inferred from the RDLENGTH and the length of the next domain name. be inferred from the RDLENGTH and the length of the next domain name.
5.3 Additional Complexity Due to Wildcards 5.3 Additional Complexity Due to Wildcards
Proving that a non-existent name response is correct or that a Proving that a non-existent name response is correct or that a
wildcard expansion response is correct makes things a little more wildcard expansion response is correct makes things a little more
complex. complex.
skipping to change at page 29, line 27 skipping to change at page 29, line 27
big.foo.nil, big.foo.nil,
medium.foo.nil. medium.foo.nil.
small.foo.nil. small.foo.nil.
tiny.foo.nil. tiny.foo.nil.
Then a query to a security aware server for huge.foo.nil would Then a query to a security aware server for huge.foo.nil would
produce an error reply with an RCODE of NXDOMAIN and the authority produce an error reply with an RCODE of NXDOMAIN and the authority
section data including something like the following: section data including something like the following:
foo.nil NXT big.foo.nil NS KEY SOA NXT ;prove no *.foo.nil foo.nil. NXT big.foo.nil NS KEY SOA NXT ;prove no *.foo.nil
foo.nil SIG NXT 1 2 ( ;type-cov=NXT, alg=1, labels=2 foo.nil. SIG NXT 1 2 ( ;type-cov=NXT, alg=1, labels=2
19970102030405 ;signature expiration 19970102030405 ;signature expiration
19961211100908 ;time signed 19961211100908 ;time signed
2143 ;key identifier 2143 ;key identifier
foo.nil. ;signer foo.nil. ;signer
AIYADP8d3zYNyQwW2EM4wXVFdslEJcUx/fxkfBeH1El4ixPFhpfHFElxbvKoWmvjDTCm AIYADP8d3zYNyQwW2EM4wXVFdslEJcUx/fxkfBeH1El4ixPFhpfHFElxbvKoWmvjDTCm
fiYy2X+8XpFjwICHc398kzWsTMKlxovpz2FnCTM= ;signature (640 bits) fiYy2X+8XpFjwICHc398kzWsTMKlxovpz2FnCTM= ;signature (640 bits)
) )
big.foo.nil. NXT medium.foo.nil. A MX SIG NXT ;prove no huge.foo.nil big.foo.nil. NXT medium.foo.nil. A MX SIG NXT ;prove no huge.foo.nil
big.foo.nil. SIG NXT 1 3 ( ;type-cov=NXT, alg=1, labels=3 big.foo.nil. SIG NXT 1 3 ( ;type-cov=NXT, alg=1, labels=3
19970102030405 ;signature expiration 19970102030405 ;signature expiration
skipping to change at page 30, line 9 skipping to change at page 30, line 9
Note that this response implies that big.foo.nil is an existing name Note that this response implies that big.foo.nil is an existing name
in the zone and thus has other RR types associated with it than NXT. in the zone and thus has other RR types associated with it than NXT.
However, only the NXT (and its SIG) RR appear in the response to this However, only the NXT (and its SIG) RR appear in the response to this
query for huge.foo.nil, which is a non-existent name. query for huge.foo.nil, which is a non-existent name.
5.5 Special Considerations at Delegation Points 5.5 Special Considerations at Delegation Points
A name (other than root) which is the head of a zone also appears as A name (other than root) which is the head of a zone also appears as
the leaf in a superzone. If both are secure, there will always be the leaf in a superzone. If both are secure, there will always be
two different NXT RRs with the same name. They can be distinguished two different NXT RRs with the same name. They can be easily
by their signers, the next domain name fields, the presence of the distinguished by their signers, the next domain name fields, the
SOA type bit, etc. Security aware servers should return the correct presence of the SOA type bit, etc. Security aware servers should
NXT automatically when required to authenticate the non-existence of return the correct NXT automatically when required to authenticate
a name and both NXTs, if available, on explicit query for type NXT. the non-existence of a name and both NXTs, if available, on explicit
query for type NXT.
Non-security aware servers will never automatically return an NXT and Non-security aware servers will never automatically return an NXT and
some old implementations may only return the NXT from the subzone on some old implementations may only return the NXT from the subzone on
explicit queries. explicit queries.
5.6 Zone Transfers 5.6 Zone Transfers
The sections below describe how full and incremental zone transfers The subsections below describe how full and incremental zone
are secured. transfers are secured.
SIG RRs secure all authoritative RRs transferred for both full and SIG RRs secure all authoritative RRs transferred for both full and
incremental [RFC 1995] zone transfers. NXT RRs are an essential incremental [RFC 1995] zone transfers. NXT RRs are an essential
elements in secure zone transfers and assure that every authoritative elements in secure zone transfers and assure that every authoritative
name and type will be present; however, if there are multiple SIGs name and type will be present; however, if there are multiple SIGs
with the same name and type covered a subset of the SIGs could be with the same name and type covered, a subset of the SIGs could be
sent as long as at least one is present and, in the case of unsigned sent as long as at least one is present and, in the case of unsigned
delegation point NS or glue A or AAAA RRs a subset of these RRs could delegation point NS or glue A or AAAA RRs a subset of these RRs or
be sent as long as at least one of each type is included. simply a modified set could be sent as long as at least one of each
type is included.
To provide server authentication that a complete transfer has
occurred, transaction authentication SHOULD be used on all full zone
transfers. This provides strong server based protection for the
entire zone in transit.
When an incremental or full zone transfer request is received with When an incremental or full zone transfer request is received with
the same or newer version number than that of the server's copy of the same or newer version number than that of the server's copy of
the zone, it is replied to with just the SOA RR of the server's the zone, it is replied to with just the SOA RR of the server's
current version and the SIG RRset verifying that SOA RR. current version and the SIG RRset verifying that SOA RR.
5.6.1 Incremental Zone Transfers The complete NXT chaims specified in this document enable a resolver
to obtain, by successive queries chaining through NXTs, all of the
names in a zone even if zone transfers are prohibited. Different
format NXTs may be specified in the future to avoid this.
5.6.1 Full Zone Transfers
To provide server authentication that a complete transfer has
occurred, transaction authentication SHOULD be used on all full zone
transfers. This provides strong server based protection for the
entire zone in transit.
5.6.2 Incremental Zone Transfers
Individual RRs in an incremental (IXFR) transfer [RFC 1995] can be Individual RRs in an incremental (IXFR) transfer [RFC 1995] can be
verified in the same way as for a full zone transfer and the verified in the same way as for a full zone transfer and the
integrity of the NXT name chain and correctness of the NXT type bits integrity of the NXT name chain and correctness of the NXT type bits
for the zone after the incremental RR deletes and adds can check each for the zone after the incremental RR deletes and adds can check each
disjoint area of the zone updated. But the completeness of an disjoint area of the zone updated. But the completeness of an
incremental transfer can not be confirmed because usually neither the incremental transfer can not be confirmed because usually neither the
deleted RR section nor the added RR section has a compete NXT chain. deleted RR section nor the added RR section has a compete NXT chain.
As a result, a server which securely supports IXFR must handle IXFR As a result, a server which securely supports IXFR must handle IXFR
SIG RRs for each incremental transfer set that it maintains. SIG RRs for each incremental transfer set that it maintains.
skipping to change at page 31, line 23 skipping to change at page 31, line 31
adjacent incremental update sets is done by the zone owner, the adjacent incremental update sets is done by the zone owner, the
original IXFR SIG for each set included in the condensation must be original IXFR SIG for each set included in the condensation must be
discarded and a new on IXFR SIG calculated to cover the resulting discarded and a new on IXFR SIG calculated to cover the resulting
condensed set. condensed set.
The IXFR SIG really belongs to the zone as a whole, not to the zone The IXFR SIG really belongs to the zone as a whole, not to the zone
name. Although it should be correct for the zone name, the labels name. Although it should be correct for the zone name, the labels
field of an IXFR SIG is otherwise meaningless. The IXFR SIG is only field of an IXFR SIG is otherwise meaningless. The IXFR SIG is only
sent as part of an incremental zone transfer. After validation of sent as part of an incremental zone transfer. After validation of
the IXFR SIG, the transferred RRs MAY be considered valid without the IXFR SIG, the transferred RRs MAY be considered valid without
verification of the internal SIGs. verification of the internal SIGs if such trust in the server
conforms to local policy.
6. How to Resolve Securely and the AD and CD Bits 6. How to Resolve Securely and the AD and CD Bits
Retrieving or resolving secure data from the Domain Name System (DNS) Retrieving or resolving secure data from the Domain Name System (DNS)
involves starting with one or more trusted public keys that have been involves starting with one or more trusted public keys that have been
staticly configured at the resolver. With starting trusted keys, a staticly configured at the resolver. With starting trusted keys, a
resolver willing to perform cryptography can progress securely resolver willing to perform cryptography can progress securely
through the secure DNS structure to the zone of interest as described through the secure DNS structure to the zone of interest as described
in Section 6.3. Such trusted public keys would normally be configured in Section 6.3. Such trusted public keys would normally be configured
in a manner similar to that described in Section 6.2. However, as a in a manner similar to that described in Section 6.2. However, as a
skipping to change at page 32, line 43 skipping to change at page 32, line 43
described in Section 6.1. described in Section 6.1.
The proper validation of signatures requires a reasonably secure The proper validation of signatures requires a reasonably secure
shared opinion of the absolute time between resolvers and servers as shared opinion of the absolute time between resolvers and servers as
described in Section 6.4. described in Section 6.4.
6.1 The AD and CD Header Bits 6.1 The AD and CD Header Bits
Two previously unused bits are allocated out of the DNS Two previously unused bits are allocated out of the DNS
query/response format header. The AD (authentic data) bit indicates query/response format header. The AD (authentic data) bit indicates
in a response that the data included in the answer and authority in a response that all the data included in the response is answer
sections has been authenticated by the server according to the and authority data that has been authenticated by the server
policies of that server or is accompanying glue address or delegation according to the policies of that server or is accompanying
point NS data. The CD (checking disabled) bit indicates in a query additional information section data. The CD (checking disabled) bit
that Pending (non-authenticated) data is acceptable to the resolver indicates in a query that Pending (non-authenticated) data is
sending the query. acceptable to the resolver sending the query.
These bits are allocated from the previously must-be-zero Z field as These bits are allocated from the previously must-be-zero Z field as
follows: follows:
1 1 1 1 1 1 1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID | | ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z|AD|CD| RCODE | |QR| Opcode |AA|TC|RD|RA| Z|AD|CD| RCODE |
skipping to change at page 33, line 41 skipping to change at page 33, line 41
the CD bit on all queries to permit it to impose its own policies and the CD bit on all queries to permit it to impose its own policies and
to reduce DNS latency time by allowing security aware servers to to reduce DNS latency time by allowing security aware servers to
answer with Pending data. answer with Pending data.
Security aware servers MUST NOT return Bad data. For non-security Security aware servers MUST NOT return Bad data. For non-security
aware resolvers or security aware resolvers requesting service by aware resolvers or security aware resolvers requesting service by
having the CD bit clear, security aware servers MUST return only having the CD bit clear, security aware servers MUST return only
Authenticated or Insecure data in the answer and authority sections Authenticated or Insecure data in the answer and authority sections
with the AD bit set in the response. Security aware servers SHOULD with the AD bit set in the response. Security aware servers SHOULD
return Pending data, with the AD bit clear in the response, to return Pending data, with the AD bit clear in the response, to
security aware resolvers requesting the service by asserting the CD security aware resolvers requesting this service by asserting the CD
bit in their request. The AD bit MUST NOT be set on a response bit in their request. The AD bit MUST NOT be set on a response
unless all of the RRs in the answer and authority sections of the unless all of the RRs in the answer and authority sections of the
response are either Authenticated or Insecure. response are either Authenticated or Insecure. The AD bit does not
cover the additional information section.
6.2 Staticly Configured Keys 6.2 Staticly Configured Keys
The public key to authenticate a zone SHOULD be defined in local The public key to authenticate a zone SHOULD be defined in local
configuration files before that zone is loaded at the primary server configuration files before that zone is loaded at the primary server
so the zone can be authenticated. so the zone can be authenticated.
While it might seem logical for everyone to start with the meta-root While it might seem logical for everyone to start with a public key
public key and staticly configure this in every resolver, this has associated with the root zone and staticly configure this in every
problems. The logistics of updating every DNS resolver in the world resolver, this has problems. The logistics of updating every DNS
should this key ever change would be severe. Furthermore, many resolver in the world should this key ever change would be severe.
organizations will explicitly wish their "interior" DNS Furthermore, many organizations will explicitly wish their "interior"
implementations to completely trust only their own DNS servers. DNS implementations to completely trust only their own DNS servers.
Interior resolvers of such organizations can then go through the Interior resolvers of such organizations can then go through the
organization's zone servers to access data outsize the organization's organization's zone servers to access data outsize the organization's
domain and should not be configured with keys above the domain and should not be configured with keys above the
organization's DNS apex. organization's DNS apex.
Host resolvers that are not part of a larger organization may be Host resolvers that are not part of a larger organization may be
configured with a key for the domain of their local ISP whose configured with a key for the domain of their local ISP whose
recursive secure DNS caching server they use. recursive secure DNS caching server they use.
6.3 Chaining Through The DNS 6.3 Chaining Through The DNS
skipping to change at page 34, line 43 skipping to change at page 34, line 45
6.3.1 Chaining Through KEYs 6.3.1 Chaining Through KEYs
In general, some RRset that you wish to validate in the secure DNS In general, some RRset that you wish to validate in the secure DNS
will be signed by one or more SIG RRs. Each of these SIG RRs has a will be signed by one or more SIG RRs. Each of these SIG RRs has a
signer under whose name is stored the public KEY to use in signer under whose name is stored the public KEY to use in
authenticating the SIG. Each of those KEYs will, generally, also be authenticating the SIG. Each of those KEYs will, generally, also be
signed with a SIG. And those SIGs will have signer names also signed with a SIG. And those SIGs will have signer names also
referring to KEYs. And so on. As a result, authentication leads to referring to KEYs. And so on. As a result, authentication leads to
chains of alternating SIG and KEY RRs with the first SIG signing the chains of alternating SIG and KEY RRs with the first SIG signing the
original data whose authenticity is to be shown and the final KEY original data whose authenticity is to be shown and the final KEY
being some key staticly configured at the resolver performing the being some trusted key staticly configured at the resolver performing
authentication. the authentication.
In testing such a chain, the validity periods of the SIGs encountered In testing such a chain, the validity periods of the SIGs encountered
must be intersected to determine the validity period of the must be intersected to determine the validity period of the
authentication of the data, a purely algorithm process. In addition, authentication of the data, a purely algorithmic process. In
the validation of each SIG over the data with reference to a KEY must addition, the validation of each SIG over the data with reference to
meet the objective cryptographic test implied by the cryptographic a KEY must meet the objective cryptographic test implied by the
algorithm used, although even here the resolver may have policies as cryptographic algorithm used, although even here the resolver may
to trusted algorithms and key lengths. In addition, The judgement have policies as to trusted algorithms and key lengths. Finally, the
that a SIG with a particular signer name can authenticate data judgement that a SIG with a particular signer name can authenticate
(possibly a KEY RRset) with a particular owner name, however, is data (possibly a KEY RRset) with a particular owner name, is
primarily a policy question. Ultimately, this is a policy local to primarily a policy question. Ultimately, this is a policy local to
the resolver and any clients that depend on that resolver's the resolver and any clients that depend on that resolver's
decisions. It is, however, strongly recommended, that the following decisions. It is, however, recommended, that the following policy be
policy be adopted: adopted:
Let A < B mean that A is a shorter domain name than B formed by Let A < B mean that A is a shorter domain name than B formed by
dropping one or more whole labels from the left end of B, i.e., dropping one or more whole labels from the left end of B, i.e.,
A is a direct or indirect superdomain of B. Let A = B mean that A is a direct or indirect superdomain of B. Let A = B mean that
A and B are the same domain name (i.e., are identical after A and B are the same domain name (i.e., are identical after
letter case canonicalization). Let A > B mean that A is a letter case canonicalization). Let A > B mean that A is a
longer domain name than B formed by adding one or more whole longer domain name than B formed by adding one or more whole
labels on the left end of B, i.e., A is a direct or indirect labels on the left end of B, i.e., A is a direct or indirect
subdomain of B subdomain of B
Let Static be the owner names of the set of staticly configured Let Static be the owner names of the set of staticly configured
trusted keys at a resolver. trusted keys at a resolver.
Then Signer is a valid signer name for a SIG authenticating data Then Signer is a valid signer name for a SIG authenticating an
(possibly a KEY RRset) with owner name Owner at a resolver if RRset (possibly a KEY RRset) with owner name Owner at a resolver
any of the following three rules apply: if any of the following three rules apply:
(1) Owner > or = Signer (except that if Signer is root, Owner (1) Owner > or = Signer (except that if Signer is root, Owner
must be root or a top level domain name). must be root or a top level domain name). That is, Owner is the
same as or a subdomain of Signer.
(2) ( Owner < or = Signer ) and ( Signer > some Static ). (2) ( Owner < Signer ) and ( Signer > or = some Static ). That
is, Owner is a superdomain of Signer and Signer is staticly
configured or a subdomain of a staticly configured key.
(3) Signer = some Static. (3) Signer = some Static. That is, the signer is exactly some
staticly configured key.
Rule 1 is the rule for descending the DNS tree and includes a special Rule 1 is the rule for descending the DNS tree and includes a special
prohibition on the root zone key due to the restriction that the root prohibition on the root zone key due to the restriction that the root
zone be only one label deep. This is the most fundamental rule. zone be only one label deep. This is the most fundamental rule.
Rule 2 is the rule for ascending the DNS tree from one or more Rule 2 is the rule for ascending the DNS tree from one or more
staticly configured keys. Rule 2 has no effect if only root keys or staticly configured keys. Rule 2 has no effect if only root zone
the meta-root key are staticly configured. keys are staticly configured.
Rule 3 is a rule permitting direct cross certification. Rule 3 has Rule 3 is a rule permitting direct cross certification. Rule 3 has
no effect if only root keys or the meta-root key are staticly no effect if only root zone keys are staticly configured.
configured.
Great care should be taken that the consequences have been fully Great care should be taken that the consequences have been fully
considered before making any local policy adjustments to these rules considered before making any local policy adjustments to these rules
(other than dispensing with rules 2 and 3 if only root keys or the (other than dispensing with rules 2 and 3 if only root zone keys are
meta-root key are staticly configured). staticly configured).
6.3.2 Conflicting Data 6.3.2 Conflicting Data
It is possible that there will be multiple SIG-KEY chains that appear It is possible that there will be multiple SIG-KEY chains that appear
to authenticate conflicting RRset answers to the same query. A to authenticate conflicting RRset answers to the same query. A
resolver should choose only the most reliable answer to return and resolver should choose only the most reliable answer to return and
discard other data. This choice of most reliable is a matter of discard other data. This choice of most reliable is a matter of
local policy which could take into account differing trust in local policy which could take into account differing trust in
algorithms, key sizes, staticly configured keys, zones traversed, algorithms, key sizes, staticly configured keys, zones traversed,
etc. The technique given below is recommended for taking into etc. The technique given below is recommended for taking into
skipping to change at page 36, line 46 skipping to change at page 36, line 49
via such zones could be set to 256 or more as this exceeds the via such zones could be set to 256 or more as this exceeds the
largest possible distance through secure zones in the DNS. largest possible distance through secure zones in the DNS.
6.4 Secure Time 6.4 Secure Time
Coordinated interpretation of the time fields in SIG RRs requires Coordinated interpretation of the time fields in SIG RRs requires
that reasonably consistent time be available to the hosts that reasonably consistent time be available to the hosts
implementing the DNS security extensions. implementing the DNS security extensions.
A variety of time synchronization protocols exist including the A variety of time synchronization protocols exist including the
Network Time Protocol (NTP [RFC 1305]). If such protocols are used, Network Time Protocol (NTP [RFC 1305, 2030]). If such protocols are
they MUST be used securely so that time can not be spoofed. used, they MUST be used securely so that time can not be spoofed.
Otherwise, for example, a host could get its clock turned back and Otherwise, for example, a host could get its clock turned back and
might then believe old SIG RRs, and the data they authenticate, which might then believe old SIG RRs, and the data they authenticate, which
were valid but are no longer. were valid but are no longer.
7. ASCII Representation of Security RRs 7. ASCII Representation of Security RRs
This section discusses the format for master file and other ASCII This section discusses the format for master file and other ASCII
presentation of the three DNS security resource records. presentation of the three DNS security resource records.
The algorithm field in KEY and SIG RRs can be represented as either The algorithm field in KEY and SIG RRs can be represented as either
skipping to change at page 38, line 14 skipping to change at page 39, line 14
The protocol octet can be represented as either an unsigned integer The protocol octet can be represented as either an unsigned integer
or symbolicly. The following initial symbols are defined: or symbolicly. The following initial symbols are defined:
000 NONE 000 NONE
001 TLS 001 TLS
002 EMAIL 002 EMAIL
003 DNSSEC 003 DNSSEC
004 IPSEC 004 IPSEC
255 ALL 255 ALL
Note that if the type field has the NOKEY value, nothing appears Note that if the type flags field has the NOKEY value, nothing
after the algorithm octet. appears after the algorithm octet.
The remaining public key portion is represented in base 64 (see The remaining public key portion is represented in base 64 (see
Appendix A) and may be divided up into any number of white space Appendix A) and may be divided up into any number of white space
separated substrings, down to single base 64 digits, which are separated substrings, down to single base 64 digits, which are
concatenated to obtain the full signature. These substrings can span concatenated to obtain the full signature. These substrings can span
lines using the standard parenthesis. lines using the standard parenthesis.
Note that the public key may have internal sub-fields but these do Note that the public key may have internal sub-fields but these do
not appear in the master file representation. For example, with not appear in the master file representation. For example, with
algorithm 1 there is a public exponent size, then a public exponent, algorithm 1 there is a public exponent size, then a public exponent,
skipping to change at page 40, line 13 skipping to change at page 41, line 13
RR type present bits in the same format as the WKS RR. RR type present bits in the same format as the WKS RR.
8. Canonical Form and Order of Resource Records 8. Canonical Form and Order of Resource Records
This section describes the canonical form of resource records (RRs), This section describes the canonical form of resource records (RRs),
their default name order, and their order, for purposes of domain their default name order, and their order, for purposes of domain
name system (DNS) security. A canonical name order is necessary to name system (DNS) security. A canonical name order is necessary to
construct the NXT name chain. A canonical form and ordering within construct the NXT name chain. A canonical form and ordering within
an RRset is necessary in constructing SIG RRs. A canonical ordering an RRset is necessary in constructing SIG RRs. A canonical ordering
of types within a name is required in connection with incremental of types within a name is required in connection with incremental
transfer (Section 5.6.1). transfer (Section 5.6.2).
8.1 Canonical RR Form 8.1 Canonical RR Form
For purposes of DNS security, the canonical form for an RR is the For purposes of DNS security, the canonical form for an RR is the
wire format of the RR with domain names (1) fully expanded (no name wire format of the RR with domain names (1) fully expanded (no name
compression via pointers), (2) all domain name letters set to lower compression via pointers), (2) all domain name letters set to lower
case, (3) owner name wild cards in master file form (no substitution case, (3) owner name wild cards in master file form (no substitution
made for *), and (4) the original TTL substituted for the current made for *), and (4) the original TTL substituted for the current
TTL. TTL.
skipping to change at page 41, line 16 skipping to change at page 42, line 16
Within any particular owner name and type, RRs are sorted by RDATA as Within any particular owner name and type, RRs are sorted by RDATA as
a left justified unsigned octet sequence where the absence of an a left justified unsigned octet sequence where the absence of an
octet sorts before the zero octet. octet sorts before the zero octet.
8.4 Canonical Ordering of RR Types 8.4 Canonical Ordering of RR Types
When RRs of the same name but different types must be ordered, they When RRs of the same name but different types must be ordered, they
are ordered by type, considering the type to be an unsigned integer, are ordered by type, considering the type to be an unsigned integer,
except that SIG RRs are placed immediately after the type they cover. except that SIG RRs are placed immediately after the type they cover.
Thus, for example, an A record would be put before an MX record but Thus, for example, an A record would be put before an MX record
if both were signed, the order would be A < SIG(A) < MX < SIG(MX). because A is type 1 and MX is type 15 but if both were signed, the
order would be A < SIG(A) < MX < SIG(MX).
9. Conformance 9. Conformance
Levels of server and resolver conformance are defined below. Levels of server and resolver conformance are defined below.
9.1 Server Conformance 9.1 Server Conformance
Two levels of server conformance for DNS security are defined as Two levels of server conformance for DNS security are defined as
follows: follows:
skipping to change at page 42, line 46 skipping to change at page 43, line 46
a server) are defined for DNS Security: a server) are defined for DNS Security:
BASIC: A basic compliance resolver can handle SIG, KEY, and NXT RRs BASIC: A basic compliance resolver can handle SIG, KEY, and NXT RRs
when they are explicitly requested. when they are explicitly requested.
FULL: A fully compliant resolver (1) understands KEY, SIG, and NXT FULL: A fully compliant resolver (1) understands KEY, SIG, and NXT
RRs including verification of SIGs, (2) maintains appropriate RRs including verification of SIGs, (2) maintains appropriate
information in its local caches and database to indicate which RRs information in its local caches and database to indicate which RRs
have been authenticated and to what extent they have been have been authenticated and to what extent they have been
authenticated, (3) performs additional queries as necessary to authenticated, (3) performs additional queries as necessary to
attempt to obtain KEY, SIG, or NXT RRs from non-security aware attempt to obtain KEY, SIG, or NXT RRs when needed, (4) normally sets
servers, (4) normally sets the CD query header bit on its queries. the CD query header bit on its queries.
10. Security Considerations 10. Security Considerations
This document specifies extensions to the Domain Name System (DNS) This document specifies extensions to the Domain Name System (DNS)
protocol to provide data integrity and origin authentication, public protocol to provide data integrity and origin authentication, public
key distribution, and optional transaction and request security. key distribution, and optional transaction and request security.
It should be noted that, at most, these extensions guarantee the It should be noted that, at most, these extensions guarantee the
validity of resource records, including KEY resource records, validity of resource records, including KEY resource records,
retrieved from the DNS. They do not magically solve other security retrieved from the DNS. They do not magically solve other security
problems. For example, using secure DNS you can have high confidence problems. For example, using secure DNS you can have high confidence
in the IP address you retrieve for a host name; however, this does in the IP address you retrieve for a host name; however, this does
not stop someone for substituting an unauthorized host at that not stop someone for substituting an unauthorized host at that
address or capturing packets sent to that address and falsely address or capturing packets sent to that address and falsely
responding with packets apparently from that address. Any reasonably responding with packets apparently from that address. Any reasonably
complete security system will require the protection of many complete security system will require the protection of many
additional facets of the Internet. additional facets of the Internet beyond DNS.
The implementation of NXT RRs as described herein enables a resolver
to determine all the names in a zone even if zone transfers are
prohibited (section 5.6). This is an active area of work and may
change.
A number of precautions in DNS implementation have evolved over the A number of precautions in DNS implementation have evolved over the
years to provide maximum resisitence of the insecure DNS against years to harden the insecure DNS against spoofing. These precautions
spoofing. These precautions should not be abandoned but should be should not generally be abandoned but should be considered to provide
considered to provide minor additional protection in case of key additional protection in case of key compromise in secure DNS.
compromise in secure DNS.
References References
[RFC 1032] - M. Stahl, "Domain Administrators Guide", November 1987. [RFC 1032] - M. Stahl, "Domain Administrators Guide", November 1987.
[RFC 1033] - M. Lottor, "Domain Administrators Operations Guide", [RFC 1033] - M. Lottor, "Domain Administrators Operations Guide",
November 1987. November 1987.
[RFC 1034] - P. Mockapetris, "Domain Names - Concepts and [RFC 1034] - P. Mockapetris, "Domain Names - Concepts and
Facilities", STD 13, November 1987. Facilities", STD 13, November 1987.
skipping to change at page 44, line 35 skipping to change at page 45, line 35
[RFC 1825] - Ran Atkinson, "Security Architecture for the Internet [RFC 1825] - Ran Atkinson, "Security Architecture for the Internet
Protocol", August 1995. Protocol", August 1995.
[RFC 1982] - Robert Elz, Rrandy Bush, "Serial Number Arithmetic", [RFC 1982] - Robert Elz, Rrandy Bush, "Serial Number Arithmetic",
09/03/1996. 09/03/1996.
[RFC 1995] - Masatka Ohta, "Incremental Zone Transfer in DNS", August [RFC 1995] - Masatka Ohta, "Incremental Zone Transfer in DNS", August
1996. 1996.
[RFC 2030] - D. Mills, "Simple Network Time Protocol (SNTP) Version 4
for IPv4, IPv6 and OSI", October 1996.
[RFC 2045] - N. Freed & N. Borenstein, "Multipurpose Internet Mail [RFC 2045] - N. Freed & N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies", Extensions (MIME) Part One: Format of Internet Message Bodies",
November 1996. November 1996.
[RFC 2065] - Donald Eastlake, Charles Kaufman, "Domain Name System [RFC 2065] - Donald Eastlake, Charles Kaufman, "Domain Name System
Security Extensions", 01/03/1997. Security Extensions", 01/03/1997.
[RFC 2136] - P. Vixie, S. Thomson, Y. Rekhter, J. Bound, "Dynamic [RFC 2136] - P. Vixie, S. Thomson, Y. Rekhter, J. Bound, "Dynamic
Updates in the Domain Name System (DNS UPDATE)", 04/21/1997. Updates in the Domain Name System (DNS UPDATE)", 04/21/1997.
[RFC 2137] - Donald Eastlake, "Secure Domain Name System Dynamic [RFC 2137] - Donald Eastlake, "Secure Domain Name System Dynamic
Update", 04/21/1997. Update", 04/21/1997.
[RFC 2181] - Robert Elz, Randy Bush, "Clarifications to the DNS [RFC 2181] - Robert Elz, Randy Bush, "Clarifications to the DNS
Specification", July 1997. Specification", July 1997.
[RFC xxx1] - draft-ietf-dnssec-rsa-*, "RSA/MD5 KEYs and SIGs in the draft-ietf-dnssec-rsa-*.txt, D. Eastlake, "RSA/MD5 KEYs and SIGs in
Domain Name System (DNS)". the Domain Name System (DNS)".
[RFC xxx2] - draft-ietf-dnssec-dhk-*, "Storage of Diffie-Hellman Keys draft-ietf-dnssec-dhk-*.txt, D. Eastlake, "Storage of Diffie-Hellman
in the Domain Name System (DNS)". Keys in the Domain Name System (DNS)".
[RFC xxx3] - draft-ietf-dnssec-dss-*, "DSA KEYs and SIGs in the draft-ietf-dnssec-dss-*.txt, D. Eastlake, "DSA KEYs and SIGs in the
Domain Name System (DNS)". Domain Name System (DNS)".
[RFC xxx4] - draft-ietf-dnssec-indirect-key-*, "Indirect KEY RRs in draft-ietf-dsnssec-certs-*.txt, D. Eastlake, O. Gudmundsson, "Storing
the Domain Name System (DNS)". Certificates in the Domain Name System".
[RSA FAQ] - RSADSI Frequently Asked Questions periodic posting. draft-ietf-dnssec-secops-*.txt, D. Eastlake, "DNS Operational
Security Considerations".
draft-ietf-tls-*.txt draft-ietf-tls-*.txt,
[RSA FAQ] - RSADSI Frequently Asked Questions periodic posting.
Author's Address Author's Address
Donald E. Eastlake 3rd Donald E. Eastlake 3rd
CyberCash, Inc. CyberCash, Inc.
318 Acton Street 318 Acton Street
Carlisle, MA 01741 USA Carlisle, MA 01741 USA
Telephone: +1 978-287-4877 Telephone: +1 978-287-4877
+1 978-371-7148 (fax)
+1 703-620-4200 (main office, Reston, Virginia, USA) +1 703-620-4200 (main office, Reston, Virginia, USA)
fax: +1 978-371-7148
email: dee@cybercash.com email: dee@cybercash.com
Expiration and File Name Expiration and File Name
This draft expires July 1998. This draft expires September 1998.
Its file name is draft-ietf-dnssec-secext2-03.txt. Its file name is draft-ietf-dnssec-secext2-04.txt.
Appendix A: Base 64 Encoding Appendix A: Base 64 Encoding
The following encoding technique is taken from [RFC 2045] by N. The following encoding technique is taken from [RFC 2045] by N.
Borenstein and N. Freed. It is reproduced here in an edited form for Borenstein and N. Freed. It is reproduced here in an edited form for
convenience. convenience.
A 65-character subset of US-ASCII is used, enabling 6 bits to be A 65-character subset of US-ASCII is used, enabling 6 bits to be
represented per printable character. (The extra 65th character, "=", represented per printable character. (The extra 65th character, "=",
is used to signify a special processing function.) is used to signify a special processing function.)
skipping to change at page 49, line 12 skipping to change at page 50, line 12
exactly 16 bits; here, the final unit of encoded output will be three exactly 16 bits; here, the final unit of encoded output will be three
characters followed by one "=" padding character. characters followed by one "=" padding character.
Appendix B: Changes from RFC 2065 Appendix B: Changes from RFC 2065
This section summarizes the most important changes that have been This section summarizes the most important changes that have been
made since RFC 2065. made since RFC 2065.
1. Most of Section 7 of [RFC 2065] called "Operational 1. Most of Section 7 of [RFC 2065] called "Operational
Considerations", has been removed and may be made into a separate Considerations", has been removed and may be made into a separate
document. document [draft-ietf-dnssec-secops-*.txt].
2. The KEY RR has been changed by (2a) eliminating the "experimental" 2. The KEY RR has been changed by (2a) eliminating the "experimental"
flag as unnecessary, (2b) reserving a flag bit for flags flag as unnecessary, (2b) reserving a flag bit for flags
expansion, (2c) more compactly encoding a number of bit fields in expansion, (2c) more compactly encoding a number of bit fields in
such a way as to leave unchanged bits actually used by the limited such a way as to leave unchanged bits actually used by the limited
code currently deployed, (2d) eliminating the IPSEC and email flag code currently deployed, (2d) eliminating the IPSEC and email flag
bits which are replaced by values of the protocol field and adding bits which are replaced by values of the protocol field and adding
a protocol field value for dnssec, (2e) adding material to a protocol field value for DNS security itself, (2e) adding
indicate that zone KEY RRs occur only at delegation points, and material to indicate that zone KEY RRs occur only at delegation
(2f) removing the description of the RSA/MD5 algorithm to a points, and (2f) removing the description of the RSA/MD5 algorithm
separate document. Section 3.4 describing the meaning of various to a separate document [draft-ietf-dnssec-rsa-*.txt]. Section 3.4
combinations of "no-key" and key present KEY RRs has been added. describing the meaning of various combinations of "no-key" and key
present KEY RRs has been added and the secure / unsecure status of
a zone has been clarified as being per algorithm.
3. The SIG RR has been changed by (3a) renaming the "time signed" 3. The SIG RR has been changed by (3a) renaming the "time signed"
field to be the "signature inception" field, (3b) clarifying that field to be the "signature inception" field, (3b) clarifying that
signature expiration and inception used serial number ring signature expiration and inception use serial number ring
arithmetic, (3c) changing the definition of the key footprint/tag arithmetic, (3c) changing the definition of the key footprint/tag
for algorithms other than 1 (i.e., algorithms to be defined in the for algorithms other than 1 and adding Appendix C to specify its
future) and adding Appendix C to document its calculation. In calculation. In addition, the SIG covering type AXFR has been
addition, the SIG covering type AXFR has been eliminated while one eliminated while one covering IXFR [RFC 1995] has been added (see
covering IXFR has been added. section 5.6).
4. Algorithm 3, the DSA algorithm, is designated as the mandatory to 4. Algorithm 3, the DSA algorithm, is now designated as the mandatory
implement algorithm. Algorithm 1, the RSA/MD5 algorithm, is now a to implement algorithm. Algorithm 1, the RSA/MD5 algorithm, is
recommended option. Both the KEY and SIG RR definitions have been now a recommended option. Algorithm 2 and 4 are designated as the
simplified by eliminating the "null" algorithm 253 as defined in Diffie-Hellman key and elliptic cryptography algorithms
[RFC 2065]. That algorithm had been included because at the time respectively, all to be defined in separate documents. Algorithm
it was thought it might be useful in DNS dynamic update [RFC code point 252 is designated to indicate "indirect" keys, to be
2136]. It was in fact not so used and it is dropped to simplify defined in a separate document, where the actual key is elsewhere.
DNS security. Both the KEY and SIG RR definitions have been simplified by
eliminating the "null" algorithm 253 as defined in [RFC 2065].
That algorithm had been included because at the time it was
thought it might be useful in DNS dynamic update [RFC 2136]. It
was in fact not so used and it is dropped to simplify DNS
security.
5. The NXT RR has been changed so that (5a) the NXT RRs in a zone 5. The NXT RR has been changed so that (5a) the NXT RRs in a zone
cover all names, including wildcards as literal names without cover all names, including wildcards as literal names without
expansion, except for glue address records whose names would not expansion, except for glue address records whose names would not
otherwise appear, (5b) all NXT bit map areas whose first octet has otherwise appear, (5b) all NXT bit map areas whose first octet has
bit zero set have been reserved for future definition, and (5c) bit zero set have been reserved for future definition, and (5c)
extending the number of and circumstances under which an NXT must extending the number of and circumstances under which an NXT must
be returned in connection with wildcard names. be returned in connection with wildcard names.
6. Information on the canonical form and ordering of RRs has been 6. Information on the canonical form and ordering of RRs has been
moved into a separate Section 8. moved into a separate Section 8.
7. A subsection covering incremental and full zone transfer has been 7. A subsection covering incremental and full zone transfer has been
added in Section 5. added in Section 5.
8. Concerning DNS chaining: Further specification and policy 8. Concerning DNS chaining: Further specification and policy
recommendations on secure resolution have been added, primarily in recommendations on secure resolution have been added, primarily in
Section 6.3.1. That authenticated data has a validity period of Section 6.3.1. It is now clearly stated that authenticated data
the intersection of the validity periods of the SIG RRs in its has a validity period of the intersection of the validity periods
authentication chain was clarified. The requirement to staticly of the SIG RRs in its authentication chain. The requirement to
configure a superzone's key signed by a zone in all of the zone's staticly configure a superzone's key signed by a zone in all of
authoritative servers has been relaxed in cases where the public the zone's authoritative servers has been relaxed in cases where
key for that zone and all of its direct and indirect subzones will the public key for that zone and all of its direct and indirect
never be staticly configured. The recommendation was dropped to subzones is not staticly configured. The recommendation was
continue DNS security checks in a secure island of DNS data that dropped to continue DNS security checks in a secure island of DNS
is separated from other parts of the DNS tree by insecure zones data that is separated from other parts of the DNS tree by
and does not contain a zone for which a key has been staticly insecure zones and does not contain a zone for which a key has
configured. been staticly configured.
9. The concept of a meta-root key has been added in Section 4.5.
10. That the presence of the AD bit in a response does not apply to 9. It was clarified that the presence of the AD bit in a response
the additional information section or to glue address or does not apply to the additional information section or to glue
delegation point NS RRs was clarified. address or delegation point NS RRs.
Appendix C: Key Tag Calculation Appendix C: Key Tag Calculation
The key tag field in the SIG RR is just a means of more efficiently The key tag field in the SIG RR is just a means of more efficiently
selecting the correct KEY RR to use in verifying the signature when selecting the correct KEY RR to use when there is more than one KEY
there is more than one KEY RR candidate. It is possible for more RR candidate. It is possible for more than one candidate key to have
than one candidate key to have the same tag, in which case each must the same tag, in which case each must be tried in verifying a
be tried in verifying the signature until one works or all fail. The signature, for example, until one works or all fail. The following
following reference implementation is in ANSI C. It is coded for reference implementation is in ANSI C. It is coded for clarity, not
clarity, not efficiency. efficiency.
/* assumes int is at least 16 bits /* assumes int is at least 16 bits
first byte of key tag is the most significant byte of return value first byte of the key tag is the most significant byte of return value
second byte of key tag is the least significant byte of return value */ second byte of the key tag is the least significant byte of return value
*/
int keytag ( int keytag (
unsigned char key[], /* the RDATA part of the KEY RR */ unsigned char key[], /* the RDATA part of the KEY RR */
unsigned int keysize, /* the RDLENGTH */ unsigned int keysize, /* the RDLENGTH */
) )
{ {
long int ac; /* assumed to be 32 bits or larger */ long int ac; /* assumed to be 32 bits or larger */
for ( ac = 0, i = 0; i < keysize; ++i ) for ( ac = 0, i = 0; i < keysize; ++i )
ac += (i&1) ? key[i] : key[i]<<8; ac += (i&1) ? key[i] : key[i]<<8;
 End of changes. 121 change blocks. 
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