An Extension Language for the DNS
draft-levine-dnsextlang-13
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | John R. Levine , Paul A. Vixie | ||
| Last updated | 2024-02-04 | ||
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| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-levine-dnsextlang-13
Network Working Group J. Levine
Internet-Draft Taughannock Networks
Intended status: Standards Track P. Vixie
Expires: 7 August 2024 4 February 2024
An Extension Language for the DNS
draft-levine-dnsextlang-13
Abstract
Adding new RRTYPEs to the DNS has required that DNS servers and
provisioning software be upgraded to support each new RRTYPE in
Master files. This document defines a DNS extension language
intended to allow most new RRTYPEs to be supported by adding entries
to configuration data read by the DNS software, with no software
changes needed for each RRTYPE.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 7 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Typical usage . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Extension language syntax . . . . . . . . . . . . . . . . . . 4
3.1. Lexical structure . . . . . . . . . . . . . . . . . . . . 4
3.2. Storage in the DNS . . . . . . . . . . . . . . . . . . . 5
3.2.1. Record type directory . . . . . . . . . . . . . . . . 6
3.3. Storage in a file . . . . . . . . . . . . . . . . . . . . 6
3.4. Stanza structure . . . . . . . . . . . . . . . . . . . . 6
3.5. Field types . . . . . . . . . . . . . . . . . . . . . . . 7
3.5.1. Integer fields . . . . . . . . . . . . . . . . . . . 7
3.5.2. IP address and partial address fields . . . . . . . . 8
3.5.3. Domain name fields . . . . . . . . . . . . . . . . . 8
3.5.4. String fields . . . . . . . . . . . . . . . . . . . . 9
3.5.5. Base-32 and Base-64 fields . . . . . . . . . . . . . 9
3.5.6. Hex fields . . . . . . . . . . . . . . . . . . . . . 9
3.5.7. Time stamp fields . . . . . . . . . . . . . . . . . . 10
3.5.8. Miscellaneous fields . . . . . . . . . . . . . . . . 10
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Security considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. References - Normative . . . . . . . . . . . . . . . . . 12
7.2. References - Informative . . . . . . . . . . . . . . . . 13
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 14
A.1. Changes from -12 to -13 . . . . . . . . . . . . . . . . . 14
A.2. Changes from -11 to -12 . . . . . . . . . . . . . . . . . 14
A.3. Changes from -10 to -11 . . . . . . . . . . . . . . . . . 14
A.4. Changes from -09 to -10 . . . . . . . . . . . . . . . . . 14
A.5. Changes from -08 to -09 . . . . . . . . . . . . . . . . . 14
A.6. Changes from -07 to -08 . . . . . . . . . . . . . . . . . 14
A.7. Changes from -06 to -07 . . . . . . . . . . . . . . . . . 15
A.8. Changes from -05 to -06 . . . . . . . . . . . . . . . . . 15
A.9. Changes from -04 to -05 . . . . . . . . . . . . . . . . . 15
A.10. Changes from -03 to -04 . . . . . . . . . . . . . . . . . 15
A.11. Changes from -02 to -03 . . . . . . . . . . . . . . . . . 15
A.12. Changes from -01 to -02 . . . . . . . . . . . . . . . . . 15
A.13. Changes from -00 to -01 . . . . . . . . . . . . . . . . . 15
Appendix B. Descriptions of currently defined RRTYPEs . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
The Domain Name System[RFC1034] [RFC1035] is designed to be
extensible, with new record types, known as RRTYPEs, added as needed.
While it is straightforward in principle to add a new RRTYPE, in
practice it can be difficult due to the software changes needed to
add the new RRTYPE to the master file format read by many
authoritative DNS servers, and to the provisioning software used to
create and update the master files or the local equivalent.
While some new RRTYPEs, notably those for DNSSEC [RFC4033], require
that DNS servers do new special purpose processing, most new RRTYPEs
are, from the point of view of the DNS, just static data to return to
queries, perhaps with some additional section records if the record
includes another domain name. This document defines an extension
language to describe any RRTYPEs, so that provisioning software can
parse master file records for the RRTYPEs. DNS servers can use the
extension language to implement RRTYPEs that do not require special
purpose processing.
The extension language can also be useful in provisioning software,
to create input forms and validate the syntax of entered records.
2. Typical usage
The extension language is written as strings of UTF-8 text that
describe new RR types, intended to be stored in the DNS itself.
(They may also be stored in a local file with a well-known name, for
debugging and local overrides, but this usage is optional.) All of
the DNS software that needs to handle master file records fetches
records from the DNS as needed. To support a new RRTYPE, one would
add suitable records to the DNS zone where the descriptions are
located, or to the local file.
DNS servers can use the extension language to parse new RRTYPE
records in master files, and to translate them to the binary
representation. Servers that create ASCII master files from zone
data retrieved via AXFR can use the extension language to create
master file records for new RRTYPEs.
Provisioning software can use the extension language to create
templates for users to fill in, to create new RRTYPE records in
master files to be passed to DNS servers, and to syntax check records
entered by users. The extension language includes natural language
field descriptions intended to be used as prompts in fill-in
templates, and can handle versions of prompts in multiple languages.
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Provisioning software could create TYPEnn master records if the local
DNS server doesn't implement the extension language, although it
would be less confusing if both provisioning and server software both
accept the same master record syntax.
Some DNS servers store records in ways other than master files, such
as SQL databases. The extension language could be used to create new
schema entries to handle new RRTYPEs, although the details are too
specific to particular varieties of DNS server software for this
document to try to describe the details.
The extension language can describe all existing RRTYPEs, which may
be useful in table driven provisioning software.
3. Extension language syntax
3.1. Lexical structure
The extension language consists of "stanzas", each of which defines
an RRTYPE. In the DNS, a stanza is stored as a multi-string TXT
record, with each string conceptually being a line in the stanza. In
a file, it is stored as a series of lines. The first line of a
stanza defines the symbolic RRTYPE name. Subsequent lines, which
must start with white space, each define a field in the record.
Blank lines and comment lines where the first nonblank character is
"#" are ignored.
The following ABNF imports ALPHA, DIGIT, and WSP from [RFC5234].
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ldh = ALPHA 0*(ALPHA | DIGIT | "-")
dnsextfile = 1*stanza
stanza = rrtypeline 1*fieldline
rrtypeline = ldh ":" 1*DIGIT 0*1(":" 1*ALPHA) 0*1(WSP freetext)
fieldline = ftype 0*1qualifiers 0*1(":" ldh ) 0*1(WSP freetext)
ftype = "I1" | "I2" | "I4" | "A" | "AA" | "AAAA" | "N" | "S" |
"B32" | "B64" | "X" | "EUI48" | "EUI64" | "T" | "Z"
qualifiers = "[" qual 0*(, qual) "]"
qual = ldh "=" 1*DIGIT | "C" | "A" | "L" | "M" | "X" | "P" |
"WKS" | "NSAP" | "NXT" | "A6P" | "A6S" | "APL" | "IPSECKEY" |
"HIPHIT" | "HIPPK"
freetext = 0*(%x20-%xfe)
3.2. Storage in the DNS
Each extension language stanza stored in the DNS is stored as two
identical TXT records, one with a name based on the numeric RR type,
one with a name based on the text name. (One record may be aliased
to the other using a CNAME.) The numeric names are located at
RRTYPE.ARPA, and the text names are located at RRNAME.ARPA.
The first string in the TXT record are the identification tag
"RRTYPE=1" to identify the record as an RRTYPE definition. Each line
of the stanza is a string in the TXT records. The leading spaces
used in the file format (described below) are not used. The record
name may also have a language tag [RFC5646] prefix that identifies
the language in which the descriptive text is written. There should
always be an unprefixed record for each type, to be the default if
there is no record in the desired languge, which might be aliased to
a prefixed record with CNAME.
For example, if the FOO record type were type 999, the two records
for an English language description would be:
999.RRTYPE.ARPA. TXT "RRTYPE=1" "FOO:999 Foorec" "I2:count Count" "..."
FOO.RRNAME.ARPA. TXT "RRTYPE=1" "FOO:999 Foorec" "I2:count Count" "..."
If there are descriptions in multiple languages, they are stored with
name prefixes, and applications can choose the most suitable one.
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EN.999.RRTYPE.ARPA. TXT "RRTYPE=1" "FOO:999 Foo rec" "..."
999.RRTYPE.ARPA. CNAME EN.999.RTYPE.ARPA.
FR.999.RRTYPE.ARPA. TXT "RRTYPE=1" "FOO:999 Un foo" "..."
EN.FOO.RRNAME.ARPA. TXT "RRTYPE=1" "FOO:999 Foo rec" "..."
FOO.RRTYPE.ARPA. CNAME EN.FOO.RTYPE.ARPA.
FR.FOO.RRNAME.ARPA. TXT "RRTYPE=1" "FOO:999 Un foo" "..."
3.2.1. Record type directory
A directory of all of the available RR names is stored at
_LIST.RRTYPE.ARPA. It is a TXT record containing RRTYPE=1 followed
by each name as a separate string, e.g.:
_LIST.RRNAME.ARPA. TXT "RRTYPE=1" "A" "A6" ... "WKS" "X25"
3.3. Storage in a file
All the extension language stanzas stored in a file are stored as
lines of ASCII text. The name of the RR type starts in the first
position of the first line in the stanza. Subsequent lines in the
stanza start with white space. A line that is blank or where the
first nonblank character is a # is a comment and is ignored.
Descriptions in different languages are stored in separate files. A
directory of names can be created by scanning the file.
3.4. Stanza structure
Each stanza starts with a line containing the name of the RRTYPE, a
colon, and the numeric RRTYPE. The name of the RRTYPE must start in
the first position on the line. When stored in a file, the RRTYPE
name should not be the same as an existing RRTYPE or DNS class name
(IN or CH) or bad things will happen.
The RRTYPE may be followed a colon and letters, to indicate options
for the RRTYPE. The letter is "X" means that implementing the RRTYPE
requires extra processing by DNS servers, e.g., the extra processing
for DNAME or DNSSEC records. The intention of the option is to allow
DNS servers to report an error if a zone contains a record defined
with "X" for which the server does not implement the extra
processing. The letters "I" and "A" mean that the RRTYPE is defined
in the IN class only, or in any class, respectively. The letters "O"
and "E" indicate that the type is obsolete or experimental,
respectively.
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That can be followed by white space and a descriptive comment
intended to be displayed to human users, but not interpreted by DNS
software. Provisioning software might use the comments as prompts or
labels to help a user select the desired RRTYPE.
The rest of the lines in the stanza describe the fields in the
record. Each field is one or more octets long, and fields are stored
sequentially in the record:
FOO:999 Foo record
field description
field:tag description
field[qual,qual] description
field[qual,qual]:tag description
field ...
Some fields may be followed by a comma-separated list of qualifiers
in square brackets. The qualifiers further define the field, e.g.,
in a numeric field, the qualifiers may define symbolic names for
field values or bit masks. That can be followed by an colon and an
ldh string. The string is intended to be used as the name of the
field in software applications that create data structures for an
RRTYPE. Applications will often have to change the punctuation to
match the syntax of the programming language, such as replacing
hyphens with underscores. If two fields in an RRTYPE have the same
name, the result is undefined.
The field and optional qualifiers and name may be followed by white
space and a description of the field. The description is intended to
be displayed to human users, and is not interpreted by DNS software.
Provisioning software might use the comments as prompts or labels for
templates into which users enter RR data.
3.5. Field types
Each field type is defined by a token name consisting of letters and
digits, starting with a letter.
3.5.1. Integer fields
Integer fields are defined by I1, I2, and I4 tokens, for fields one,
two, or four octets long. The corresponding value in a master record
is an unsigned integer number. A field may be followed by qualifiers
defining symbolic field values.
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A symbolic field value is represented as NAME=NN where NAME is the
symbol and NN is the numeric value to be placed in the field. The
corresponding value in a master record is the symbol. The symbol can
contain letters, digits, and hypens. For example, to define the type
field in a CERT record [RFC4398]:
I2[PKIX=1,SPKI=2,PGP=2,IPKIX=4,ISPKI=5,IPGP=6,ACPKIX=7,\
IACPKIX=8,URI=253,OID=254]:type Certificate type
RRTYPE fields are defined by R tokens, for a two octet field
containing an RRTYPE. The corresponding value in a master record is
a symbolic RRTYPE or TYPEnnn for types without names. A R[L] token
and qualifier defines a structured bitmap of RRTYPEs used in NSEC and
NSEC3 records, which must be the last field in the record. The
corresponding value in a master record is a list of RRTYPEs.
3.5.2. IP address and partial address fields
IP address fields are defined by A or AAAA tokens, for four-octet
IPv4 addresses or 16-octet IPv6 addresses. The corresponding value
in a master record is an IP address written in the usual way. There
are no qualifiers.
The AA token defines a 64 bit field written like half of an IPv6
address, with up to four colon separated groups of up to four hex
digits.
3.5.3. Domain name fields
Domain name fields are defined by N tokens. The qualifier C means
the name is compressed. The qualifier A means that the domain name
represents a mailbox, with the first component being the local part
of the mailbox. The qualifier L means that the domain name is
converted to lower case before DNSSEC validation. An N tag and an O
qualifier, which can only appear as the last field in a record, means
the name is optional.
The corresponding value in a master record is a domain name, written
in the usual way, with \. meaning a literal dot in a record.
Names are absolute if they end with a dot, otherwise relative to
$ORIGIN, the convention for master files.
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3.5.4. String fields
String fields are defined by S tokens. A plain S token means a
single string preceded by a one-octet length. A S[M] token and
qualifier means that there may be multiple strings, each stored as a
length and string in the record. A S[M] field must be the last field
in the record.
An S[X] token and qualifier is a raw string, stored without any
length bytes. It must be the last field in the record.
The corresponding value in a master record is a string enclosed in
single or double quotes, or multiple strings if the M qualifier is
present. Embedded quotes may be escaped with a backslash, and a
double backslash represents a backslash. If a non-null string
contains no white space, quote characters, or backslashes, the quotes
may be omitted.
3.5.5. Base-32 and Base-64 fields
A base32 or base64 field is defined by a B32 or B64 token. A base32
field is stored in the record with a preceding one-octet length. A
base64 field is stored as binary data, and must be the last field in
the record.
The corresponding value in a master record is a string represented as
base32 or base64 [RFC3548]. The value of a base64 field may include
embedded spaces for readability, which are ignored.
3.5.6. Hex fields
A hex field is defined by an X token. A plain X field is binary
data. An X[C] token and qualifier means that the field is stored in
the record as a string with a preceding one-octet length. An
unqualified hex field must be the last field in the record, and may
include embedded spaces for readability, which are ignored.
The corresponding value in a master record is a string represented as
an even number of hexadecimal digits.
EUI48 and EUI64 fields are defined by X6 and X8 tokens, respectively.
The corresponding fields in master records are six or eight pairs of
hex digits separated by hyphens.
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3.5.7. Time stamp fields
A 32-bit timestamp field is defined by a T token. The corresponding
value in a master record is a fourteen digit value in the form
YYYYMMDDHHmmSS indicating a UTC timestamp, or as an unsigned number
of seconds with ten digits or less. The field is stored in the
record as a Unix timestamp, the unsigned number of seconds since
January 1, 1970 00:00:00 UTC.
3.5.8. Miscellaneous fields
Some RRTYPEs have fields with a unique syntax, represented as
qualifiers in a Z field.
Z[WKS] is the bitmap of port numbers in the WKS [RFC1035] RRTYPE.
Z[NSAP] is the special hex syntax for the address in the NSAP
[RFC1706] RRTYPE.
Z[NXT] is the bitmap of RRTYPES in the NXT [RFC2535] RRTYPE.
Z[A6P] and Z[A6S] are the prefix length and the variable length
address suffix in the A6 [RFC2874] RRTYPE.
Z[APL] is the list of address prefixes in the APL [RFC3123] RRTYPE.
Z[IPSECKEY] is the variable format gateway in the IPSECKEY [RFC4025]
RRTYPE.
Z[HIPHIT] and Z[HIPPK] are the hex HIT and base64 PK fields with
detached implicit lengths in the HIP [RFC5205] RRTYPE.
Z[SVCB] is the list of service parameters in the SVCB and HTTPS
[RFC9460] RRTYPEs.
4. Examples
A description of an MX record could be defined as:
MX:15 Mail exchanger
I2:priority Priority (lower values are higher priority)
N[A,C]:exchanger Host name
The name is MX, the RRTYPE is 15, and the data includes a two-octet
number and a compressed domain name, with additional section records
for the domain name.
The SRV record [RFC2782] could be defined as:
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SRV:33 Service location
I2:priority Priority
I2:weight Weight
I2:port Port
N:target Target host name
The name is SRV, the RRTYPE is 33. The record contains three two-
octet fields for the priority, weight, and port, and a domain name.
The domain name is not compressed.
5. Security considerations
The extension language makes it possible to create master files that
represent arbitrary DNS records. Since most DNS servers already
provide ways to represent arbitrary data, this doesn't introduce any
new security issues to the DNS and DNS servers, although it may
create security issues in provisioning software if the provisioning
system is intended to limit the kinds of records its users can
define.
Extension language files with accidentally or deliberately invalid
field definitions could provoke odd bugs in server or provisioning
software that doesn't check the syntax before using it.
When extension language data are imported from the DNS, a hostile
party might use DNS spoofing techniques to modify the records
imported. Methods to defend against DNS spoofing include DNSSEC.
6. IANA considerations
This document requests that IANA create the RRTYPE.ARPA and
RRNAME.ARPA zones. Their initial contents are as shown in
Appendix B.
When new RR types are defined, the defining documents SHOULD request
IANA to add appropriate records to RRTYPE.ARPA and RRNAME.ARPA.
This document requests that IANA create a registry of DNS Extension
Language Field Types. Its initial contents are as follows
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+=======+=================+=================+
| TYPE | REFERENCE | EXTLANG VERSION |
+=======+=================+=================+
| I1 | (this document) | 1 |
+-------+-----------------+-----------------+
| I2 | (this document) | 1 |
+-------+-----------------+-----------------+
| I4 | (this document) | 1 |
+-------+-----------------+-----------------+
| A | (this document) | 1 |
+-------+-----------------+-----------------+
| AA | (this document) | 1 |
+-------+-----------------+-----------------+
| AAAA | (this document) | 1 |
+-------+-----------------+-----------------+
| N | (this document) | 1 |
+-------+-----------------+-----------------+
| S | (this document) | 1 |
+-------+-----------------+-----------------+
| B32 | (this document) | 1 |
+-------+-----------------+-----------------+
| B64 | (this document) | 1 |
+-------+-----------------+-----------------+
| X | (this document) | 1 |
+-------+-----------------+-----------------+
| EUI48 | (this document) | 1 |
+-------+-----------------+-----------------+
| EUI64 | (this document) | 1 |
+-------+-----------------+-----------------+
| T | (this document) | 1 |
+-------+-----------------+-----------------+
| Z | (this document) | 1 |
+-------+-----------------+-----------------+
Table 1: DNS Extension Language Field
Types Registry Initial Values
7. References
7.1. References - Normative
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
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[RFC3548] Josefsson, S., Ed., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, DOI 10.17487/RFC3548, July 2003,
<https://www.rfc-editor.org/info/rfc3548>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
September 2009, <https://www.rfc-editor.org/info/rfc5646>.
7.2. References - Informative
[RFC1706] Manning, B. and R. Colella, "DNS NSAP Resource Records",
RFC 1706, DOI 10.17487/RFC1706, October 1994,
<https://www.rfc-editor.org/info/rfc1706>.
[RFC2535] Eastlake 3rd, D., "Domain Name System Security
Extensions", RFC 2535, DOI 10.17487/RFC2535, March 1999,
<https://www.rfc-editor.org/info/rfc2535>.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
DOI 10.17487/RFC2782, February 2000,
<https://www.rfc-editor.org/info/rfc2782>.
[RFC2874] Crawford, M. and C. Huitema, "DNS Extensions to Support
IPv6 Address Aggregation and Renumbering", RFC 2874,
DOI 10.17487/RFC2874, July 2000,
<https://www.rfc-editor.org/info/rfc2874>.
[RFC3123] Koch, P., "A DNS RR Type for Lists of Address Prefixes
(APL RR)", RFC 3123, DOI 10.17487/RFC3123, June 2001,
<https://www.rfc-editor.org/info/rfc3123>.
[RFC4025] Richardson, M., "A Method for Storing IPsec Keying
Material in DNS", RFC 4025, DOI 10.17487/RFC4025, March
2005, <https://www.rfc-editor.org/info/rfc4025>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/info/rfc4033>.
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[RFC4398] Josefsson, S., "Storing Certificates in the Domain Name
System (DNS)", RFC 4398, DOI 10.17487/RFC4398, March 2006,
<https://www.rfc-editor.org/info/rfc4398>.
[RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol
(HIP) Domain Name System (DNS) Extensions", RFC 5205,
DOI 10.17487/RFC5205, April 2008,
<https://www.rfc-editor.org/info/rfc5205>.
[RFC9460] Schwartz, B., Bishop, M., and E. Nygren, "Service Binding
and Parameter Specification via the DNS (SVCB and HTTPS
Resource Records)", RFC 9460, DOI 10.17487/RFC9460,
November 2023, <https://www.rfc-editor.org/info/rfc9460>.
Appendix A. Change Log
*NOTE TO RFC EDITOR: This section may be removed upon publication of
this document as an RFC.*
A.1. Changes from -12 to -13
Change to current rfcxml. Minor editorial changes.
A.2. Changes from -11 to -12
Change to xml2rfc v3. Minor editorial changes.
A.3. Changes from -10 to -11
Put language back in the name. Add _LIST directory. Add O and E
hints.
A.4. Changes from -09 to -10
Add hint letters for RRTYPE classes.
A.5. Changes from -08 to -09
Add Z fields for rrtype-specific fields. Redid qualifier
descriptions.
Add definitions of RRTYPEs.
A.6. Changes from -07 to -08
Add counted hex and raw strings and other new types. Added language
tags. Added field names.
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A.7. Changes from -06 to -07
Add RRTYPE=1 tag in TXT records.
Allow digits and hyphens in qualifier tags, for names like SHA-1.
A.8. Changes from -05 to -06
Fix formatting problems.
Add RRTYPE option "X".
A.9. Changes from -04 to -05
DNS publication in RRYPE.ARPA and RRNAME.ARPA.
A.10. Changes from -03 to -04
More use cases.
Fix up BNF
A.11. Changes from -02 to -03
First stab at BNF
Note $ORIGIN matters
A.12. Changes from -01 to -02
Editorial nits
A.13. Changes from -00 to -01
Switch to multi-line format. Add comments for provisioning.
Appendix B. Descriptions of currently defined RRTYPEs
Here are descriptions of currently RRTYPEs that can appear in zone
files. The \ indicating continuation lines are only for display in
this document and would not appear in the descriptions.
A:1:I a host address [RFC1035]
A:addr IPv4 address
NS:2:A an authoritative name server [RFC1035]
N[C]:host Host name
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MD:3:AO a mail destination (OBSOLETE - use MX) [RFC1035]
N[C]:host Host name
MF:4:AO a mail forwarder (OBSOLETE - use MX) [RFC1035]
N[C]:host Host name
CNAME:5:A the canonical name for an alias [RFC1035]
N[C]:host Host name
SOA:6:A marks the start of a zone of authority [RFC1035]
N[C]:primary Primary server name
N[A]:mailbox Responsible mailbox
I4:serial Serial number
I4:refresh Refresh time (seconds)
I4:retry Retry time (seconds)
I4:expire Expire time (seconds)
I4:minimum Minium time (seconds)
MB:7:AE a mailbox domain name (EXPERIMENTAL) [RFC1035]
N[C]:host Host name
MG:8:AE a mail group member (EXPERIMENTAL) [RFC1035]
N[A]:mailbox Mailbox name
MR:9:AE a mail rename domain name (EXPERIMENTAL) [RFC1035]
N[A]:mailbox Mailbox name
WKS:11:I a well known service description [RFC1035]
A IPv4 address
I1 Protocol number
Z[WKS]:bitmap Bit Map
PTR:12:A a domain name pointer [RFC1035]
N[C]:host Host name
HINFO:13:A host information [RFC1035]
S:cpu CPU type
S:os Operating system
MINFO:14:A mailbox or mail list information [RFC1035]
N[A]:respbox Responsible mailbox
N[A]:errbox Error mailbox
MX:15:A mail exchange [RFC1035]
I2:priority Priority (lower values are higher priority)
N[C]:hostname Host name
TXT:16:A text strings [RFC1035]
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S[M]:text Strings
RP:17:A for Responsible Person [RFC1183]
N[A]:mailbox Mailbox
N:text Text location
AFSDB:18:A for AFS Data Base location [RFC1183][RFC5864]
I2:subtype Subtype
N:hostname Hostname
X25:19:A for X.25 PSDN address [RFC1183]
S:address PSDN address
ISDN:20:A for ISDN address [RFC1183]
S[M]:address ISDN address, and optional subaddress
RT:21:A for Route Through [RFC1183]
I2:preference Preference
N:hostname Intermediate host
NSAP:22:I for NSAP address, NSAP style A record [RFC1706]
Z[NSAP]:address NSAP Address
NSAP-PTR:23:I for domain name pointer, NSAP style [RFC1348][RFC1637]
N:hostname Host name
SIG:24:A for security signature [RFC4034]
I2:sigtype Type covered
I1:algorithm Algorithm
I1:labels Labels
I4:ttl Original TTL
T:expires Signature expiration time
T:signed Time signed
I2:footprint Key footprint
N[C]:name Signer's name
B64:signature Signature data
KEY:25:A for security key [RFC4034]
I2:flags Flags
I1:protocol Protocol
I1:algorithm Algorithm
B64:data Key data
PX:26:I X.400 mail mapping information [RFC2163]
I2:pref Preference
N:idomain Internet mail domain
N:xdomain X.400 mail domain
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GPOS:27:A Geographical Position [RFC1712]
S:longitude Longitude (decimal degrees)
S:latitude Latitude (decimal degrees)
S:altitude Altitude (meters)
AAAA:28:I IP6 Address [RFC3596]
AAAA:address Address
LOC:29:A Location Information [RFC1876]
I1:version Version
I1:sphere Sphere size
I2:hprecision Horiz precision
I2:vprecision Vert precision
I4:latitude Latitude (offset milliseconds)
I4:longitude Longitude (offset milliseconds)
I4:altitude Altitude (offset cm)
NXT:30:AO Next Domain (OBSOLETE) [RFC3755][RFC2535]
N[C]:next Domain
Z[NXT]:rrtypes Bitmap of rrtypes
SRV:33:I Server Selection [1][RFC2782]
I2:priority Priority
I2:weight Weight
I2:port Port
N:target Target host name
NAPTR:35:I Naming Authority Pointer [RFC2915][RFC2168][RFC3403]
I2:order Order
I2:pref Preference
S:flags Flags
S:services Services
S:regex Regular expression
N:replacement Replacement
KX:36:I Key Exchanger [RFC2230]
I2:pref Preference
N:exchanger Exchanger
CERT:37:A CERT [RFC4398]
I2[PKIX=1,SPKI=2,PGP=2,IPKIX=4,ISPKI=5,IPGP=6,ACPKIX=7,IACPKIX=8,\
URI=253,OID=254]:type Type
I2:tag Key tag
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,INDIRECT=252,PRIVATEDNS=253,\
PRIVATEOID=254]:algorithm Algorithm
B64:certificate Certificate or CRL
A6:38:IO A6 (OBSOLETE - use AAAA) [RFC3226][RFC2874][RFC6563]
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Z[A6P]:preflen Prefix length
Z[A6S]:suffix Address suffix
N:prefname Prefix name
DNAME:39:A DNAME [RFC6672]
N:source Source name
APL:42:I APL [RFC3123]
Z[APL]:prefixes Prefixes
DS:43:A Delegation Signer [RFC4034][RFC3658]
I2:keytag Key tag
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,DSA-NSEC-SHA1=6,\
RSASHA1-NSEC3-SHA1=7,RSASHA256=8,RSASHA512=10,ECC-GOST=12,\
ECDSAP256SHA256=13,ECDSAP384SHA384=14,INDIRECT=252,PRIVATEDNS=253,\
PRIVATEOID=254]:algorithm Algorithm
I1[SHA-1=1,SHA-256=2,GOST=3,SHA-384=4]:digtype Digest type
X:digest Digest
SSHFP:44:A SSH Key Fingerprint [RFC4255]
I1:algorithm Algorithm
I1:ftype Fingerprint type
X:fingerprint Fingerprint
IPSECKEY:45:I IPSECKEY [RFC4025]
I1:prec Precedence
I1:gtype Gateway type
I1:algorithm Algorithm
Z[IPSECKEY]:gateway Gateway
B64:key Public key
RRSIG:46:A RRSIG [RFC4034][RFC3755]
R:rrtype Type covered (Type mnemonic)
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,INDIRECT=252,PRIVATEDNS=253,\
PRIVATEOID=254]:algorithm Algorithm
I1:labels Labels
I4:origttl Original TTL
T:expire Signature expiration (timestamp)
T:inception Signature inception (timestamp)
I2:keytag Key tag
N:signer Signer's name
B64:signature Signature
NSEC:47:A NSEC [RFC4034][RFC3755]
N:next Next domain name
R[L]:types Type bitmaps (as window blocks)
DNSKEY:48:A DNSKEY [RFC4034][RFC3755]
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I2:flags Flags
I1:protocol Protocol (must be 3)
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,INDIRECT=252,PRIVATEDNS=253,\
PRIVATEOID=254]:algorithm Algorithm
B64:publickey Public key
DHCID:49:I DHCID [RFC4701]
B64:dhcpinfo DHCP information
NSEC3:50:A NSEC3 [RFC5155]
I1[SHA-1=1]:algorithm Hash algorithm
I1[OPTOUT=1]:flags Flags
I2:iterations Iterations
X[C]:salt Salt
B32:next Next hashed owner
R[L]:types Type bitmaps (as window blocks)
NSEC3PARAM:51:A NSEC3PARAM [RFC5155]
I1[SHA-1=1]:algorithm Hash algorithm
I1[OPTOUT=1]:flags Flags
I2:iterations Iterations
X[C]:salt Salt
TLSA:52:A TLSA [RFC6698]
I1:usage Certificate usage
I1:selector Certificate selector
I1:mtype Matching Type
X:cert Certificate association data
SMIMEA:53:A S/MIME cert association [draft-ietf-dane-smime]
I1:usage Certificate usage
I1:selector Certificate selector
I1:mtype Matching Type
X:cert Certificate association data
HIP:55:A Host Identity Protocol [RFC-ietf-hip-rfc5205-bis-10]
I1:pkalg PK algorithm
Z[HIPHIT]:hit HIT
Z[HIPPK]:pubkey Public Key
N[O]:servers Rendezvous servers
CDS:59:A Child DS [RFC7344]
I2:keytag Key tag
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,DSA-NSEC-SHA1=6,\
RSASHA1-NSEC3-SHA1=7,RSASHA256=8,RSASHA512=10,ECC-GOST=12,\
ECDSAP256SHA256=13,ECDSAP384SHA384=14,INDIRECT=252,\
PRIVATEDNS=253,PRIVATEOID=254]:algorithm Algorithm
I1[SHA-1=1,SHA-256=2,GOST=3,SHA-384=4]:digtype Digest type
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X:digest Digest
CDNSKEY:60:A DNSKEY(s) the Child wants reflected in DS [RFC7344]
I2:flags Flags
I1:protocol Protocol (must be 3)
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,INDIRECT=252,PRIVATEDNS=253,\
PRIVATEOID=254]:algorithm Algorithm
B64:publickey Public key
OPENPGPKEY:61:A OpenPGP Key [RFC7929]
B64:key PGP key
CSYNC:62:A Child-To-Parent Synchronization [RFC7477]
I4:serial SOA serial
I2:flags Flags
R[L]:Types
ZONEMD:63:Zone Message Digest
I4:serial SOA serial
I1[SIMPLE=1]:scheme Scheme
I1:{SHA384=1]:hash Hash Algorithm
X:digest Message Digest
SVCB:64:Service Binding
I2:prio Service Priority
N:target Target name
Z[SVCB]:svcparams Service Parameters
HTTPS:65:HTTPS
I2:prio Service Priority
N:target Target name
Z[SVCB]:svcparams Service Parameters
SPF:99:AO [RFC7208]
S[M]:text SPF data
NID:104:A [RFC6742]
I2:preference Preference
AA:nodeid Node ID
L32:105:A [RFC6742]
I2:preference Preference
A:locator Locator32
L64:106:A [RFC6742]
I2:preference Preference
AA:locator Locator64
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LP:107:A [RFC6742]
I2:preference Preference
N:pointer Pointer
EUI48:108:A an EUI-48 address [RFC7043]
X6:address Address (digit pairs separated by hyphens)
EUI64:109:A an EUI-64 address [RFC7043]
X8:address Address (digit pairs separated by hyphens)
URI:256:A URI [RFC7553]
I2:priority Priority
I2:weight Weight
S[X]:target Target
CAA:257:A Certification Authority Restriction [RFC6844]
I1:flags Flags
S:tag Tag
S[X]:value Value
DLV:32769:A DNSSEC Lookaside Validation [RFC4431]
I2:key Key tag
I1[RSAMD5=1,DH=2,DSA=3,ECC=4,RSASHA1=5,INDIRECT=252,PRIVATEDNS=253,\
PRIVATEOID=254]:algorithm Algorithm
I1:type Digest type
X:digest Digest
Authors' Addresses
John Levine
Taughannock Networks
PO Box 727
Trumansburg
Email: standards@taugh.com
URI: http://jl.ly
Paul Vixie
950 Charter Street
Redwood City
Email: vixie@fsi.io
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