wdiff rfc7553.original rfc7553.txt

Network Working Group
Internet Engineering Task Force (IETF) P. Faltstrom
Internet-Draft
Request for Comments: 7553 Netnod
Intended status:
Category: Informational O. Kolkman
Expires: September 26, 2015
ISSN: 2070-1721 ISOC
March 25,
June 2015

The Uniform Resource Identifier (URI) DNS Resource Record
draft-faltstrom-uri-14

Abstract

This document describes the already registered DNS resource record
type
(RR) type, called the Uniform Resource Identifier (URI) RR, that is
used for publishing mappings from hostnames to URIs.

Status of This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a maximum candidate for any level of Internet
Standard; see Section 2 of RFC 5741.

Information about the current status of six months this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained 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 September 26, 2015.
http://www.rfc-editor.org/info/rfc7553.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3
2. Applicability Statement . . . . . . . . . . . . . . . . . . . 3
3. DNS considerations Considerations . . . . . . . . . . . . . . . . . . . . . 3 4
4. The format Format of the URI RR . . . . . . . . . . . . . . . . . . 4
4.1. Ownername, class Owner Name, Class, and type . Type . . . . . . . . . . . . . . . 4
4.2. Priority . . . . . . . . . . . . . . . . . . . . . . . . 5
4.3. Weight . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.4. Target . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.5. URI RDATA Wire Format . . . . . . . . . . . . . . . . . . 5 6
5. Usages . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Example: FTP server Server in the example.com domain Domain . . . . . . 6
5.2. Relation to S-NAPTR . . . . . . . . . . . . . . . . . . . 6 7
5.3. Relation to U-NAPTR . . . . . . . . . . . . . . . . . . . 7
5.4. Relation to SRV . . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. Registration of the URI Resource Record Type . . . . . . 7
6.2. Registration of services Services . . . . . . . . . . . . . . . . 7 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8
8. Acknowledgements References . . . . . . . . . . . . . . . . . . . . . . 8
9. . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . 9
9.1. Normative References . . . . . . . . . . 9
Appendix A. The Original RRTYPE Allocation Request . . . . . . . 11
Acknowledgements . 9
9.2. Non-normative references . . . . . . . . . . . . . . . . 9
Appendix A. The original RRTYPE Allocation Request . . . . . . . 10 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 14

1. Introduction

This document explains the use of the Domain Name System (DNS) for
the storage of URIs [RFC3986], [RFC3986] and how to resolve hostnames to such
URIs that can be used by various applications using the URI Resource
Record Type. resource
record type. For resolution resolution, the application need needs to know both the
hostname and the protocol that the URI is to be used for. The
protocol is registered by IANA.

Historically, uses of the DNS to map a domain name to a URL have
relied on the NAPTR Naming Authority Pointer (NAPTR) RRTYPEs [RFC2915] and
then on the DDDS Dynamic Delegation Discovery System (DDDS) [RFC3401]
application framework with the DNS as a database as specified in RFC
3404 [RFC3404]. This has a number of implications such as the fact
the RRSet returned will contain all URIs "connected" with the owner,
and not only the ones related to a specific service.

The URI resource record specified in this document enables the
querying party to do the equivalence equivalent of selecting which ones of the NAPTR
records one is interested in, in and have only those returned. This is
possible because data in the service field of the NAPTR record is
included in the owner part of the URI resource record type. It is
also the case that as the URI resource record type include includes the
target URI directly as part of the RDATA, it is very easy to extract
the correct target URI, instead of applying rewrite rules as in
NAPTR.

Querying for URI resource records is not replacing querying for NAPTR
resource records (or use of S-NAPTR [RFC3958]). Instead, the URI
resource record type provides a complementary mechanism to use be used
when one already knows what service field is interesting. With it,
one can directly query for the specific subset of the otherwise
possibly large RRSet given back returned when querying for NAPTR resource
records.

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 BCP 14, RFC 2119
[RFC2119].

2. Applicability Statement

In general, it is expected that URI records will be used by clients
for applications where the relevant protocol to be used is known,
but, for example, an extra abstraction is needed in order to separate
a domain name from a point of service (as addressed by the URI). One
example of such a situation is when an organisation organization has many domain
names,
names but only one official web page.

Applications MUST need to know the specific service to prepend the
hostname with. Using repetitive queries for URI records MUST NOT be is not a
replacement for querying for NAPTR records according to the NAPTR
(DDDS) or S-NAPTR algorithms. NAPTR records serve the purpose to
discover of
discovering the various services and or the URIs for (for looking up access
points for a given service. Those service). These are two very different kinds of
needs.

3. DNS considerations Considerations

Using prefix labels, such as underscored service tags, for a specific
owner name may cause a counter-intuitive effect when the owner name
is a wildcard name. For example, _s2._s1.*.example.net. _s2._s1.*.example.net is not a
wildcard name and cannot be used to return a synthesized answer for a
query name of _s2._s1.a.example.net. See Section 4.5 of RFC4592 RFC 4592
[RFC4592] for more details. Besides, underscored service tags used
for the URI RR (based on the Service "Service Name and Transport Protocol
Port Number Registry) Registry") may have slightly different semantics than
service tags used for underscored prefix labels that are used in
combination with other (yet unspecified) RR types. This may cause
subtle management problems when delegation structure that has
developed within the context of URI RRs is also to be used for other
RR types.
Since Because the service labels might be overloaded,
applications should carefully check that the application level application-level
protocol is indeed the protocol they expect.

Subtle management issues may also arise when the delegations from
service to sub service label involves sub-service labels involve several parties and different
stake holders.
stakeholders.

4. The format Format of the URI RR

This is the presentation format of the URI RR:

Ownername

Owner name TTL Class URI Priority Weight Target

The URI RR does not cause any kind of Additional Section processing.

4.1. Ownername, class Owner Name, Class, and type Type

The URI ownername owner name is subject to special conventions.

Just like the SRV RR [RFC2782] [RFC2782], the URI RR has service information
encoded in its ownername. owner name. In order to encode the service for a
specific owner name name, one uses service parameters. Valid service
parameters used are those registered by IANA in the Service "Service Name and
Transport Protocol Port Number Registry [RFC6335], Registry" [RFC6335] or as Enumservice "Enumservice
Registrations [RFC6117]. The Enumservice Registration parameters are
reversed (subtype(s) (i.e., subtype(s) before type), prepended with an underscore (_)
(_), and prepended to the owner name in separate labels. The
underscore is prepended to the service parameters to avoid collisions
with DNS labels that occur in nature, and the order is reversed to
make it possible to do delegations, if needed, to different zones
(and therefore providers of DNS).

For example, suppose we are looking for the URI for a service with
ENUM Service Parameter "A:B:C" for host example.com. Then we would
query for (QNAME,QTYPE)=("_C._B._A.example.com","URI") (QNAME,QTYPE)=("_C._B._A.example.com","URI").

As another example, suppose we are looking for the URI for a service
with Service Name "A" and Transport Protocol "B" for host
example.com. Then we would query for
(QNAME,QTYPE)=("_A._B.example.com","URI")
(QNAME,QTYPE)=("_A._B.example.com","URI").

The type number for the URI record is 256.

The URI resource record is class independent.

The URI RR has no special TTL Time-to-Live (TTL) requirements.

4.2. Priority

The

This field holds the priority of the target URI in this RR. Its
range is 0-65535. A client MUST attempt to contact the URI with the
lowest-numbered priority it can reach; URIs with the same priority
SHOULD be selected according to propabilities defined by the weight
field.

4.3. Weight

This field holds the server selection mechanism. The weight field
specifies a relative weight for entries with the same priority.
Larger weights SHOULD be given a proportionately higher probability
of being selected. The range of this number is 0-65535.

4.4. Target

The

This field holds the URI of the target, enclosed in double-quote
characters ('"'), where the URI is as specified in RFC 3986
[RFC3986]. Resolution of the URI is according to the definitions for
the Scheme of the URI.

Since the URI will not be encoded as a <character-string> (see
RFC1035 section
Section 3.3 [RFC1035]) of RFC 1035 [RFC1035]), there is no 255 character 255-character size
limitation.

The Target MUST NOT be an empty URI ("").

4.5. URI RDATA Wire Format

The RDATA for a URI RR consists of a 2 octet 2-octet Priority field, a two
octet
2-octet Weight field, and a variable length target variable-length Target field.

Priority and Weight are unsigned integers in network byte order.

The remaining data in the RDATA contains the Target field. The
Target field contains the URI as a sequence of octets (without the
enclosing double- quote double-quote characters used in the presentation format).

The length of the target Target field MUST be greater than zero.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Priority | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ /
/ Target /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5. Usages

5.1. Example: FTP server Server in the example.com domain Domain

An organisation organization has the domain names example.com and example.net, and
their FTP archive is at ftp://ftp1.example.com/public. Given the
Service Name
service name "ftp" and Transport Protocol transport protocol "tcp" (from the IANA
registry of Service
"Service Name and Transport Protocol Port Numbers), Number Registry"), the
following URI Resource Records resource records could be made available in the
respective zones (example.com and example.net):

$ORIGIN example.com.
_ftp._tcp IN URI 10 1 "ftp://ftp1.example.com/public"

$ORIGIN example.net.
_ftp._tcp IN URI 10 1 "ftp://ftp1.example.com/public"

5.2. Relation to S-NAPTR

The URI resource record type is not a replacement for the S-NAPTR.
It is instead an extension and the second step of the S-NAPTR
resolution can resolve a URI resource record instead of using SRV
records and yet another algorithm for how to use SRV records for the
specific protocol.

$ORIGIN example.com.
;; order pref flags
IN NAPTR 100 10 "D" "EM:ProtA" ( ; service
"" ; regexp
_http._tcp.example.com. ) ; replacement

_http._tcp IN URI 10 1 "http://www.example.com/path"

5.3. Relation to U-NAPTR

The URI Resource Record Type, resource record type, together with S-NAPTR, can be viewed as
a replacement for U-NAPTR [RFC4848]. The URI Resource Record Type resource record type is
though
only interesting when one know a base domain name, a protocol protocol, and a
service so that one can compose the record to look up. NAPTR records
of any kind are used to look up what services exists exist for a certain
domain, which is one step before the URI resource record is used.

5.4. Relation to SRV

The URI Resource Record Type resource record type can be viewed as a replacement for the
SRV record. This is because it it, like the SRV record record, can only be
looked up if one know knows the base domain, the protocol protocol, and the
service. It has a similar functionality, functionality and uses the same registry
for Service
Names, service names, but instead of returning a hostname and port
number, the URI record return returns a full URI. As such, it can be viewed
as a more powerful resource record than SRV.

6. IANA Considerations

6.1. Registration of the URI Resource Record Type

After an expert review in February 2011 (see Appendix A) A), IANA has
allocated RRTYPE 256 for the URI Resource Record Type resource record type in the registry
named Resource "Resource Record (RR) TYPEs and QTYPEs as TYPEs" (as defined in BCP 42 (at [BCP42], which was
RFC 6195 at the time but has since been replaced by RFC 6195 [RFC6195]), 6895) located
at
http://www.iana.org/assignments/dns-parameters. <http://www.iana.org/assignments/dns-parameters>.

IANA is requested to update has updated the reference with that for this registration to refer to this
RFC.

6.2. Registration of services Services

No new registry is needed for the registration of services as the
Service Name, Transport Protocol Port Numbers, Enumservices and the
DNS SRV Service Type registries are used also used for the URI resource
record type.

7. Security Considerations

Using the URI resource record together with security mechanisms that
relies
rely on verification of authentication of hostnames, like TLS, makes
it important to choose the correct domain name when doing the
comparison,
comparison and ensure that the change in what the hostname to use be used is
secured by DNSSEC so that it can be trusted in a similar way as a
redirect in HTTP using TLS.

If, for example example, the URI resource record is not signed with the help
of
DNSSEC, DNSSEC and then validated successfully, trusting the non-signed
URI will effectlyely effectively lead to a downgrade attack.

The basic mechanism for successful use of URI works as follows:

1. Announce the fact that example.com is hosted at example.org (with some
URL) in DNS DNS.

2. Secure the URI resource record with DNSSEC. Best of course This is best done
by doing validation in the application doing the lookup, but it
could also be done in the local recursive resolver or in the
trusted recursive resolver also doing validation. All are
according to the local trust policy.

3. Verify the TLS (for example) certificate for the connection to
example.org matches, i.e. i.e., use the hostname in the URI and not
the hostname used originally when looking up the URI resource
record.

4. If needed, do application layer authentication etc application-layer authentication, etc., over the
then encrypted connection.

What also can happen

It is also possible that the URI in the resource record type has
errors in it. Applications using the URI resource record type for
resolution should behave similarly as if the user typed (or copy copied
and pasted) the URI. At least it must be clear to the user that the
error is not due to any error from his side.

One SHOULD NOT include userinfo (see User Information, "User Information",
Section 3.2.1,
in 3.2.1 of RFC 3986 [RFC3986]) in a URI that is used in a URI
resource record as DNS data must be viewed as publicly available
information.

8. Acknowledgements

Ideas on how to split the two different kind of queries "What
services exists for this domain name" and "What is the URI for this
service" came from Scott Bradner and Lawrence Conroy. Other people
that have contributed to this document include Richard Barnes, Leslie
Daigle, Victor Dukhovni, Olafur Gudmundsson, Philip Hallam-Baker, Ted
Hardie, Sam Hartman, Evan Hunt, John klensin, Peter Koch, Eliot Lear,
Andy Newton, Mark Nottingham, Penn Pfautz, Jinmei Tatuya, Willem
Toorop, Nico Williams.

Cisco is acknowledged as mr Faltstrom's employer at the time this
document was developed.

The NLnet Labs is acknowledged as mr Kolkman's employer at the time
this document was developed.

9. References

9.1.

8.1. Normative References

[BCP42] Eastlake 3rd, D., "Domain Name System (DNS) IANA
Considerations", BCP 42, RFC 6895, April 2013,
<http://www.rfc-editor.org/info/bcp42>.

[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987. 1987, <http://www.rfc-editor.org/info/rfc1035>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997.

[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005.

[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.

[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010. 2005,
<http://www.rfc-editor.org/info/rfc3986>.

[RFC6117] Hoeneisen, B., Mayrhofer, A., and J. Livingood, "IANA
Registration of Enumservices: Guide, Template, and IANA
Considerations", RFC 6117, DOI 10.17487/RFC6117, March 2011.

[RFC6195] Eastlake, D., "Domain Name System (DNS) IANA
Considerations", RFC 6195, March 2011.
2011, <http://www.rfc-editor.org/info/rfc6117>.

[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011.

9.2. Non-normative references 2011,
<http://www.rfc-editor.org/info/rfc6335>.

8.2. Informative References

[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. 2000,
<http://www.rfc-editor.org/info/rfc2782>.

[RFC2915] Mealling, M. and R. Daniel, "The Naming Authority Pointer
(NAPTR) DNS Resource Record", RFC 2915,
DOI 10.17487/RFC2915, September 2000,
<http://www.rfc-editor.org/info/rfc2915>.

[RFC3401] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Part One: The Comprehensive DDDS", RFC 3401,
DOI 10.17487/RFC3401, October 2002. 2002,
<http://www.rfc-editor.org/info/rfc3401>.

[RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Part Three: The Domain Name System (DNS) Database",
RFC 3403, DOI 10.17487/RFC3403, October 2002. 2002,
<http://www.rfc-editor.org/info/rfc3403>.

[RFC3404] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Part Four: The Uniform Resource Identifiers (URI)",
RFC 3404, DOI 10.17487/RFC3404, October 2002. 2002,
<http://www.rfc-editor.org/info/rfc3404>.

[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
(RR) Types", RFC 3597, DOI 10.17487/RFC3597, September 2003.

[RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain
Name System (DNS)", RFC 3833, August 2004.
2003, <http://www.rfc-editor.org/info/rfc3597>.

[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application
Service Location Using SRV RRs and the Dynamic Delegation
Discovery Service (DDDS)", RFC 3958, DOI 10.17487/RFC3958,
January 2005. 2005, <http://www.rfc-editor.org/info/rfc3958>.

[RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name
System", RFC 4592, DOI 10.17487/RFC4592, July 2006. 2006,
<http://www.rfc-editor.org/info/rfc4592>.

[RFC4848] Daigle, L., "Domain-Based Application Service Location
Using URIs and the Dynamic Delegation Discovery Service
(DDDS)", RFC 4848, DOI 10.17487/RFC4848, April 2007. 2007,
<http://www.rfc-editor.org/info/rfc4848>.

[RFC5507] IAB, Faltstrom, P., Ed., Austein, R., Ed., and P. Koch,
Ed., "Design Choices When Expanding the DNS", RFC 5507,
DOI 10.17487/RFC5507, April 2009. 2009,
<http://www.rfc-editor.org/info/rfc5507>.

Appendix A. The original Original RRTYPE Allocation Request

On February 22, 2011 IANA assigned RRTYPE 256 for the URI resource
record based on a request that followed the procedure documented in
[BCP42] (which was RFC 6195 [RFC6195]. at the time but has since been replaced
by RFC 6895). The DNS RRTYPE PARAMETER ALLOCATION form as submitted
to IANA at thet that time is replicated below for reference.

Note: Although "ownername" should be "owner name", "ownername" has
been preserved below because it was part of the original request form
submitted to IANA.

A. Submission Date:

May 23, 2009

B. Submission Type:

[X] New RRTYPE
[ ] Modification to existing RRTYPE

C. Contact Information for submitter:

Name: Patrik Faltstrom
Email Address: paf@cisco.com
International telephone number: +46-8-6859131
Other contact handles:
(Note: This information will be publicly posted.)

D. Motivation for the new RRTYPE application?

There is no easy way to get from a domain name to a URI (or
IRI). URI. Some
mechanisms exists via use of the NAPTR [RFC3403] resource
record. That implies quite complicated rules that are
simplified via the S-NAPTR [RFC3958] specification. But, the
ability to directly look up a URI still exists. This
specification uses a prefix based naming mechanism originated in
the definition of the SRV [RFC2782] resource record, and the
RDATA is a URI, encoded as one text field.