draft-ietf-dnsext-dhcid-rr-12.txt   draft-ietf-dnsext-dhcid-rr-13.txt 
DNSEXT M. Stapp DNSEXT M. Stapp
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: September 1, 2006 T. Lemon Expires: September 23, 2006 T. Lemon
Nominum, Inc. Nominum, Inc.
A. Gustafsson A. Gustafsson
Araneus Information Systems Oy Araneus Information Systems Oy
February 28, 2006 March 22, 2006
A DNS RR for Encoding DHCP Information (DHCID RR) A DNS RR for Encoding DHCP Information (DHCID RR)
<draft-ietf-dnsext-dhcid-rr-12.txt> <draft-ietf-dnsext-dhcid-rr-13.txt>
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 37 skipping to change at page 1, line 37
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 1, 2006. This Internet-Draft will expire on September 23, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
It is possible for DHCP clients to attempt to update the same DNS It is possible for DHCP clients to attempt to update the same DNS
FQDN or attempt to update a DNS FQDN that has been added to the DNS FQDN or attempt to update a DNS FQDN that has been added to the DNS
for another purpose as they obtain DHCP leases. Whether the DHCP for another purpose as they obtain DHCP leases. Whether the DHCP
server or the clients themselves perform the DNS updates, conflicts server or the clients themselves perform the DNS updates, conflicts
can arise. To resolve such conflicts, "Resolution of DNS Name can arise. To resolve such conflicts, [1] proposes storing client
Conflicts" [1] proposes storing client identifiers in the DNS to identifiers in the DNS to unambiguously associate domain names with
unambiguously associate domain names with the DHCP clients to which the DHCP clients to which they refer. This memo defines a distinct
they refer. This memo defines a distinct RR type for this purpose RR type for this purpose for use by DHCP clients and servers, the
for use by DHCP clients and servers, the "DHCID" RR. "DHCID" RR.
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. DHCID RDATA format . . . . . . . . . . . . . . . . . . . . 3 3.1. DHCID RDATA format . . . . . . . . . . . . . . . . . . . . 3
3.2. DHCID Presentation Format . . . . . . . . . . . . . . . . 4 3.2. DHCID Presentation Format . . . . . . . . . . . . . . . . 4
3.3. The DHCID RR Identifier Type Codes . . . . . . . . . . . . 4 3.3. The DHCID RR Identifier Type Codes . . . . . . . . . . . . 4
3.4. The DHCID RR Digest Type Code . . . . . . . . . . . . . . 4 3.4. The DHCID RR Digest Type Code . . . . . . . . . . . . . . 5
3.5. Computation of the RDATA . . . . . . . . . . . . . . . . . 5 3.5. Computation of the RDATA . . . . . . . . . . . . . . . . . 5
3.5.1. Using the Client's DUID . . . . . . . . . . . . . . . 5 3.5.1. Using the Client's DUID . . . . . . . . . . . . . . . 5
3.5.2. Using the Client Identifier Option . . . . . . . . . . 5 3.5.2. Using the Client Identifier Option . . . . . . . . . . 6
3.5.3. Using the Client's htype and chaddr . . . . . . . . . 6 3.5.3. Using the Client's htype and chaddr . . . . . . . . . 6
3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.6.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 6 3.6.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 6
3.6.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 6 3.6.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 7
3.6.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . 7 3.6.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . 7
4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . . 7 4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . . 8
5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . . 8 5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 12
1. Terminology 1. Introduction
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [2].
2. Introduction
A set of procedures to allow DHCP [6] [10] clients and servers to A set of procedures to allow DHCP [7] [11] clients and servers to
automatically update the DNS (RFC 1034 [3], RFC 1035 [4]) is proposed automatically update the DNS ([3], [4]) is proposed in [1].
in "Resolution of DNS Name Conflicts" [1].
Conflicts can arise if multiple DHCP clients wish to use the same DNS Conflicts can arise if multiple DHCP clients wish to use the same DNS
name or a DHCP client attempts to use a name added for another name or a DHCP client attempts to use a name added for another
purpose. To resolve such conflicts, "Resolution of DNS Name purpose. To resolve such conflicts, [1] proposes storing client
Conflicts" [1] proposes storing client identifiers in the DNS to identifiers in the DNS to unambiguously associate domain names with
unambiguously associate domain names with the DHCP clients using the DHCP clients using them. In the interest of clarity, it is
them. In the interest of clarity, it is preferable for this DHCP preferable for this DHCP information to use a distinct RR type. This
information to use a distinct RR type. This memo defines a distinct memo defines a distinct RR for this purpose for use by DHCP clients
RR for this purpose for use by DHCP clients or servers, the "DHCID" or servers, the "DHCID" RR.
RR.
In order to obscure potentially sensitive client identifying In order to obscure potentially sensitive client identifying
information, the data stored is the result of a one-way SHA-256 hash information, the data stored is the result of a one-way SHA-256 hash
computation. The hash includes information from the DHCP client's computation. The hash includes information from the DHCP client's
message as well as the domain name itself, so that the data stored in message as well as the domain name itself, so that the data stored in
the DHCID RR will be dependent on both the client identification used the DHCID RR will be dependent on both the client identification used
in the DHCP protocol interaction and the domain name. This means in the DHCP protocol interaction and the domain name. This means
that the DHCID RDATA will vary if a single client is associated over that the DHCID RDATA will vary if a single client is associated over
time with more than one name. This makes it difficult to 'track' a time with more than one name. This makes it difficult to 'track' a
client as it is associated with various domain names. client as it is associated with various domain names.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [2].
3. The DHCID RR 3. The DHCID RR
The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The
DHCID RR is only defined in the IN class. DHCID RRs cause no DHCID RR is only defined in the IN class. DHCID RRs cause no
additional section processing. The DHCID RR is not a singleton type. additional section processing.
3.1. DHCID RDATA format 3.1. DHCID RDATA format
The RDATA section of a DHCID RR in transmission contains RDLENGTH The RDATA section of a DHCID RR in transmission contains RDLENGTH
octets of binary data. The format of this data and its octets of binary data. The format of this data and its
interpretation by DHCP servers and clients are described below. interpretation by DHCP servers and clients are described below.
DNS software should consider the RDATA section to be opaque. DHCP DNS software should consider the RDATA section to be opaque. DHCP
clients or servers use the DHCID RR to associate a DHCP client's clients or servers use the DHCID RR to associate a DHCP client's
identity with a DNS name, so that multiple DHCP clients and servers identity with a DNS name, so that multiple DHCP clients and servers
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representing the actual identifier: representing the actual identifier:
< 2 octets > Identifier type code < 2 octets > Identifier type code
< 1 octet > Digest type code < 1 octet > Digest type code
< n octets > Digest (length depends on digest type) < n octets > Digest (length depends on digest type)
3.2. DHCID Presentation Format 3.2. DHCID Presentation Format
In DNS master files, the RDATA is represented as a single block in In DNS master files, the RDATA is represented as a single block in
base 64 encoding identical to that used for representing binary data base 64 encoding identical to that used for representing binary data
in RFC 3548 [7]. The data may be divided up into any number of white in [8], Section 3. The data may be divided up into any number of
space separated substrings, down to single base 64 digits, which are white space separated substrings, down to single base 64 digits,
concatenated to form the complete RDATA. These substrings can span which are concatenated to form the complete RDATA. These substrings
lines using the standard parentheses. can span lines using the standard parentheses.
3.3. The DHCID RR Identifier Type Codes 3.3. The DHCID RR Identifier Type Codes
The DHCID RR Identifier Type Code specifies what data from the DHCP The DHCID RR Identifier Type Code specifies what data from the DHCP
client's request was used as input into the hash function. The client's request was used as input into the hash function. The
identifier type codes are defined in a registry maintained by IANA, identifier type codes are defined in a registry maintained by IANA,
as specified in Section 7. The initial list of assigned values for as specified in Section 7. The initial list of assigned values for
the identifier type code is: the identifier type code and that type's identifier is:
0x0000 = htype, chaddr from a DHCPv4 client's DHCPREQUEST [6].
0x0001 = The data octets (i.e., the Type and Client-Identifier
fields) from a DHCPv4 client's Client Identifier option [9].
0x0002 = The client's DUID (i.e., the data octets of a DHCPv6
client's Client Identifier option [10] or the DUID field from a
DHCPv4 client's Client Identifier option [12]).
0x0003 - 0xfffe = Available to be assigned by IANA.
0xffff = RESERVED +------------------+------------------------------------------------+
| Identifier Type | Identifier |
| Code | |
+------------------+------------------------------------------------+
| 0x0000 | The 1-octet 'htype' followed by 'hlen' octets |
| | of 'chaddr' from a DHCPv4 client's DHCPREQUEST |
| | [7]. |
| 0x0001 | The data octets (i.e., the Type and |
| | Client-Identifier fields) from a DHCPv4 |
| | client's Client Identifier option [10]. |
| 0x0002 | The client's DUID (i.e., the data octets of a |
| | DHCPv6 client's Client Identifier option [11] |
| | or the DUID field from a DHCPv4 client's |
| | Client Identifier option [6]). |
| 0x0003 - 0xfffe | Undefined; available to be assigned by IANA. |
| 0xffff | Undefined; RESERVED |
+------------------+------------------------------------------------+
3.4. The DHCID RR Digest Type Code 3.4. The DHCID RR Digest Type Code
The DHCID RR Digest Type Code is an identifier for the digest The DHCID RR Digest Type Code is an identifier for the digest
algorithm used. The digest is calculated over an identifier and the algorithm used. The digest is calculated over an identifier and the
canonical FQDN as described in the next section. canonical FQDN as described in the next section.
The digest type codes are defined in a registry maintained by IANA, The digest type codes are defined in a registry maintained by IANA,
as specified in Section 7. The initial list of assigned values for as specified in Section 7. The initial list of assigned values for
the digest type codes is: value 0 is reserved and value 1 is SHA-256. the digest type codes is: value 0 is reserved and value 1 is SHA-256.
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future expansion, is formed by concatenating the 2-octet identifier future expansion, is formed by concatenating the 2-octet identifier
type code, the 1-octet digest type code, and the digest value (32 type code, the 1-octet digest type code, and the digest value (32
octets for SHA-256). octets for SHA-256).
< identifier-type > < digest-type > < digest > < identifier-type > < digest-type > < digest >
The input to the digest hash function is defined to be: The input to the digest hash function is defined to be:
digest = SHA-256(< identifier > < FQDN >) digest = SHA-256(< identifier > < FQDN >)
The FQDN is represented in the buffer in unambiguous canonical form The FQDN is represented in the buffer in the canonical wire format as
as described in RFC 4034 [8], section 6.1. The identifier type code described in [9], section 6.2. The identifier type code and the
and the identifier are related as specified in Section 3.3: the identifier are related as specified in Section 3.3: the identifier
identifier type code describes the source of the identifier. type code describes the source of the identifier.
A DHCPv4 updater uses the 0x0002 type code if a Client Identifier A DHCPv4 updater uses the 0x0002 type code if a Client Identifier
option is present in the DHCPv4 messages and it is encoded as option is present in the DHCPv4 messages and it is encoded as
specified in [12]. Otherwise, the updater uses 0x0001 if a Client specified in [6]. Otherwise, the updater uses 0x0001 if a Client
Identifier option is present and 0x0000 if not. Identifier option is present and 0x0000 if not.
A DHCPv6 updater always uses the 0x0002 type code. A DHCPv6 updater always uses the 0x0002 type code.
3.5.1. Using the Client's DUID 3.5.1. Using the Client's DUID
When the updater is using the Client's DUID (either from a DHCPv6 When the updater is using the Client's DUID (either from a DHCPv6
Client Identifier option or from a portion of the DHCPv4 Client Client Identifier option or from a portion of the DHCPv4 Client
Identifier option encoded as specified in [12]), the first two octets Identifier option encoded as specified in [6]), the first two octets
of the DHCID RR MUST be 0x0002, in network byte order. The third of the DHCID RR MUST be 0x0002, in network byte order. The third
octet is the digest type code (1 for SHA-256). The rest of the DHCID octet is the digest type code (1 for SHA-256). The rest of the DHCID
RR MUST contain the results of computing the SHA-256 hash across the RR MUST contain the results of computing the SHA-256 hash across the
octets of the DUID followed by the FQDN. octets of the DUID followed by the FQDN.
3.5.2. Using the Client Identifier Option 3.5.2. Using the Client Identifier Option
When the updater is using the DHCPv4 Client Identifier option sent by When the updater is using the DHCPv4 Client Identifier option sent by
the client in its DHCPREQUEST message, the first two octets of the the client in its DHCPREQUEST message, the first two octets of the
DHCID RR MUST be 0x0001, in network byte order. The third octet is DHCID RR MUST be 0x0001, in network byte order. The third octet is
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'chaddr' field in the client's DHCPREQUEST message follow, in the 'chaddr' field in the client's DHCPREQUEST message follow, in the
same order in which the octets appear in the DHCPREQUEST message. same order in which the octets appear in the DHCPREQUEST message.
The number of significant octets in the 'chaddr' field is specified The number of significant octets in the 'chaddr' field is specified
in the 'hlen' field of the DHCPREQUEST message. The FQDN data, as in the 'hlen' field of the DHCPREQUEST message. The FQDN data, as
specified above, follows. specified above, follows.
3.6. Examples 3.6. Examples
3.6.1. Example 1 3.6.1. Example 1
A DHCP server allocating the IPv4 address 10.0.0.1 to a client with A DHCP server allocates the IPv6 address 2001:DB8::1234:5678 to a
Ethernet MAC address 01:02:03:04:05:06 using domain name client which included the DHCPv6 client-identifier option data 00:01:
"client.example.com" uses the client's link-layer address to identify 00:06:41:2d:f1:66:01:02:03:04:05:06 in its DHCPv6 request. The
the client. The DHCID RDATA is composed by setting the two type server updates the name "chi6.example.com" on the client's behalf,
octets to zero, the 1-octet digest type to 1 for SHA-256, and and uses the DHCP client identifier option data as input in forming a
performing an SHA-256 hash computation across a buffer containing the DHCID RR. The DHCID RDATA is formed by setting the two type octets
Ethernet MAC type octet, 0x01, the six octets of MAC address, and the to the value 0x0002, the 1-octet digest type to 1 for SHA-256, and
domain name (represented as specified in Section 3.5). performing a SHA-256 hash computation across a buffer containing the
14 octets from the client-id option and the FQDN (represented as
client.example.com. A 10.0.0.1 specified in Section 3.5).
client.example.com. DHCID ( AAABxLmlskllE0MVjd57zHcWmEH3pCQ6V
ytcKD//7es/deY= )
chi6.example.com. AAAA 2001:DB8::1234:5678
chi6.example.com. DHCID ( AAIBY2/AuCccgoJbsaxcQc9TUapptP69l
OjxfNuVAA2kjEA= )
If the DHCID RR type is not supported, the RDATA would be encoded If the DHCID RR type is not supported, the RDATA would be encoded
[13] as: [13] as:
\# 35 ( 000001c4b9a5b249651343158dde7bcc77169841f7a4243a572b5c283 \# 35 ( 000201636fc0b8271c82825bb1ac5c41cf5351aa69b4febd94e8f17cd
fffedeb3f75e6 ) b95000da48c40 )
3.6.2. Example 2 3.6.2. Example 2
A DHCP server allocates the IPv4 address 10.0.12.99 to a client which A DHCP server allocates the IPv4 address 192.0.2.2 to a client which
included the DHCP client-identifier option data 01:07:08:09:0a:0b:0c included the DHCP client-identifier option data 01:07:08:09:0a:0b:0c
in its DHCP request. The server updates the name "chi.example.com" in its DHCP request. The server updates the name "chi.example.com"
on the client's behalf, and uses the DHCP client identifier option on the client's behalf, and uses the DHCP client identifier option
data as input in forming a DHCID RR. The DHCID RDATA is formed by data as input in forming a DHCID RR. The DHCID RDATA is formed by
setting the two type octets to the value 0x0001, the 1-octet digest setting the two type octets to the value 0x0001, the 1-octet digest
type to 1 for SHA-256, and performing a SHA-256 hash computation type to 1 for SHA-256, and performing a SHA-256 hash computation
across a buffer containing the seven octets from the client-id option across a buffer containing the seven octets from the client-id option
and the FQDN (represented as specified in Section 3.5). and the FQDN (represented as specified in Section 3.5).
chi.example.com. A 10.0.12.99 chi.example.com. A 192.0.2.2
chi.example.com. DHCID ( AAEBOSD+XR3Os/0LozeXVqcNc7FwCfQdW chi.example.com. DHCID ( AAEBOSD+XR3Os/0LozeXVqcNc7FwCfQdW
L3b/NaiUDlW2No= ) L3b/NaiUDlW2No= )
If the DHCID RR type is not supported, the RDATA would be encoded If the DHCID RR type is not supported, the RDATA would be encoded
[13] as: [13] as:
\# 35 ( 0001013920fe5d1dceb3fd0ba3379756a70d73b17009f41d58bddbfcd \# 35 ( 0001013920fe5d1dceb3fd0ba3379756a70d73b17009f41d58bddbfcd
6a2503956d8da ) 6a2503956d8da )
3.6.3. Example 3 3.6.3. Example 3
A DHCP server allocates the IPv6 address 2000::1234:5678 to a client A DHCP server allocating the IPv4 address 192.0.2.3 to a client with
which included the DHCPv6 client-identifier option data 00:01:00:06: Ethernet MAC address 01:02:03:04:05:06 using domain name
41:2d:f1:66:01:02:03:04:05:06 in its DHCPv6 request. The server "client.example.com" uses the client's link-layer address to identify
updates the name "chi6.example.com" on the client's behalf, and uses the client. The DHCID RDATA is composed by setting the two type
the DHCP client identifier option data as input in forming a DHCID octets to zero, the 1-octet digest type to 1 for SHA-256, and
RR. The DHCID RDATA is formed by setting the two type octets to the performing an SHA-256 hash computation across a buffer containing the
value 0x0002, the 1-octet digest type to 1 for SHA-256, and 1-octet 'htype' value for Ethernet, 0x01, followed by the six octets
performing a SHA-256 hash computation across a buffer containing the of the Ethernet MAC address, and the domain name (represented as
14 octets from the client-id option and the FQDN (represented as
specified in Section 3.5). specified in Section 3.5).
chi6.example.com. AAAA 2000::1234:5678 client.example.com. A 192.0.2.3
chi6.example.com. DHCID ( AAIBY2/AuCccgoJbsaxcQc9TUapptP69l client.example.com. DHCID ( AAABxLmlskllE0MVjd57zHcWmEH3pCQ6V
OjxfNuVAA2kjEA= ) ytcKD//7es/deY= )
If the DHCID RR type is not supported, the RDATA would be encoded If the DHCID RR type is not supported, the RDATA would be encoded
[13] as: [13] as:
\# 35 ( 000201636fc0b8271c82825bb1ac5c41cf5351aa69b4febd94e8f17cd \# 35 ( 000001c4b9a5b249651343158dde7bcc77169841f7a4243a572b5c283
b95000da48c40 ) fffedeb3f75e6 )
4. Use of the DHCID RR 4. Use of the DHCID RR
This RR MUST NOT be used for any purpose other than that detailed in This RR MUST NOT be used for any purpose other than that detailed in
"Resolution of DNS Name Conflicts" [1]. Although this RR contains [1]. Although this RR contains data that is opaque to DNS servers,
data that is opaque to DNS servers, the data must be consistent the data must be consistent across all entities that update and
across all entities that update and interpret this record. interpret this record. Therefore, new data formats may only be
defined through actions of the DHC Working Group, as a result of
Therefore, new data formats may only be defined through actions of revising [1].
the DHC Working Group, as a result of revising [1].
5. Updater Behavior 5. Updater Behavior
The data in the DHCID RR allows updaters to determine whether more The data in the DHCID RR allows updaters to determine whether more
than one DHCP client desires to use a particular FQDN. This allows than one DHCP client desires to use a particular FQDN. This allows
site administrators to establish policy about DNS updates. The DHCID site administrators to establish policy about DNS updates. The DHCID
RR does not establish any policy itself. RR does not establish any policy itself.
Updaters use data from a DHCP client's request and the domain name Updaters use data from a DHCP client's request and the domain name
that the client desires to use to compute a client identity hash, and that the client desires to use to compute a client identity hash, and
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However, it should be noted that an attacker that has some knowledge, However, it should be noted that an attacker that has some knowledge,
such as of MAC addresses commonly used in DHCP client identification such as of MAC addresses commonly used in DHCP client identification
data, may be able to discover the client's DHCP identify by using a data, may be able to discover the client's DHCP identify by using a
brute-force attack. Even without any additional knowledge, the brute-force attack. Even without any additional knowledge, the
number of unknown bits used in computing the hash is typically only number of unknown bits used in computing the hash is typically only
48 to 80. 48 to 80.
Administrators should be wary of permitting unsecured DNS updates to Administrators should be wary of permitting unsecured DNS updates to
zones, whether or not they are exposed to the global Internet. Both zones, whether or not they are exposed to the global Internet. Both
DHCP clients and servers SHOULD use some form of update DHCP clients and servers SHOULD use some form of update
authentication (e.g., TSIG [11]) when performing DNS updates. authentication (e.g., [12]) when performing DNS updates.
7. IANA Considerations 7. IANA Considerations
IANA is requested to allocate a DNS RR type number for the DHCID IANA is requested to allocate a DNS RR type number for the DHCID
record type. record type.
This specification defines a new number-space for the 2-octet This specification defines a new number-space for the 2-octet
identifier type codes associated with the DHCID RR. IANA is identifier type codes associated with the DHCID RR. IANA is
requested to establish a registry of the values for this number- requested to establish a registry of the values for this number-
space. Three initial values are assigned in Section 3.3, and the space. Three initial values are assigned in Section 3.3, and the
value 0xFFFF is reserved for future use. New DHCID RR identifier value 0xFFFF is reserved for future use. New DHCID RR identifier
type codes are assigned through Standards Action, as defined in RFC type codes are assigned through Standards Action, as defined in [5].
2434 [5].
This specification defines a new number-space for the 1-octet digest This specification defines a new number-space for the 1-octet digest
type codes associated with the DHCID RR. IANA is requested to type codes associated with the DHCID RR. IANA is requested to
establish a registry of the values for this number-space. Two establish a registry of the values for this number-space. Two
initial values are assigned in Section 3.4. New DHCID RR digest type initial values are assigned in Section 3.4. New DHCID RR digest type
codes are assigned through Standards Action, as defined in RFC 2434 codes are assigned through Standards Action, as defined in [5].
[5].
8. Acknowledgements 8. Acknowledgements
Many thanks to Harald Alvestrand, Ralph Droms, Olafur Gudmundsson, Many thanks to Harald Alvestrand, Ralph Droms, Olafur Gudmundsson,
Sam Hartman, Josh Littlefield, Pekka Savola, and especially Bernie Sam Hartman, Josh Littlefield, Pekka Savola, and especially Bernie
Volz for their review and suggestions. Volz for their review and suggestions.
9. References 9. References
9.1. Normative References 9.1. Normative References
skipping to change at page 10, line 5 skipping to change at page 10, line 8
[3] Mockapetris, P., "Domain names - concepts and facilities", [3] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987. STD 13, RFC 1034, November 1987.
[4] Mockapetris, P., "Domain names - implementation and [4] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[6] Lemon, T. and B. Sommerfeld, "Node-specific Client Identifiers
for Dynamic Host Configuration Protocol Version Four (DHCPv4)",
RFC 4361, February 2006.
9.2. Informative References 9.2. Informative References
[6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, [7] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[7] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", [8] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings",
RFC 3548, July 2003. RFC 3548, July 2003.
[8] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, [9] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
"Resource Records for the DNS Security Extensions", RFC 4034, "Resource Records for the DNS Security Extensions", RFC 4034,
March 2005. March 2005.
[9] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor [10] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997. Extensions", RFC 2132, March 1997.
[10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. [11] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
[11] Vixie, P., Gudmundsson, O., Eastlake, D., and B. Wellington, [12] Vixie, P., Gudmundsson, O., Eastlake, D., and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)", "Secret Key Transaction Authentication for DNS (TSIG)",
RFC 2845, May 2000. RFC 2845, May 2000.
[12] Lemon, T. and B. Sommerfeld, "Node-specific Client Identifiers
for Dynamic Host Configuration Protocol Version Four (DHCPv4)",
RFC 4361, February 2006.
[13] Gustafsson, A., "Handling of Unknown DNS Resource Record (RR) [13] Gustafsson, A., "Handling of Unknown DNS Resource Record (RR)
Types", RFC 3597, September 2003. Types", RFC 3597, September 2003.
Authors' Addresses Authors' Addresses
Mark Stapp Mark Stapp
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Ave. 1414 Massachusetts Ave.
Boxborough, MA 01719 Boxborough, MA 01719
USA USA
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