Internet DRAFT - draft-ietf-regext-rdap-x-media-type
draft-ietf-regext-rdap-x-media-type
Registration Protocols Extensions (regext) A. Newton
Internet-Draft ICANN
Updates: 7480 (if approved) J. Singh
Intended status: Standards Track ARIN
Expires: 30 August 2024 27 February 2024
An RDAP With Extensions Media Type
draft-ietf-regext-rdap-x-media-type-00
Abstract
This document defines a media type for RDAP that can be used to
describe RDAP content with RDAP extensions. Additionally, this
document describes the usage of this media type with RDAP.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 30 August 2024.
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Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. RDAP-X: The RDAP With Extensions Media Type . . . . . . . . . 2
3. Using The RDAP-X Media Type . . . . . . . . . . . . . . . . . 3
4. Usage in RDAP Links . . . . . . . . . . . . . . . . . . . . . 4
5. RDAP-X Extension . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Using the Vary Header . . . . . . . . . . . . . . . 7
Appendix B. Design Considerations . . . . . . . . . . . . . . . 8
B.1. Not Reusing the Existing Media Type . . . . . . . . . . . 8
B.2. Query Parameters Considered Harmful . . . . . . . . . . . 8
B.2.1. Copy and Paste . . . . . . . . . . . . . . . . . . . 8
B.2.2. Redirects . . . . . . . . . . . . . . . . . . . . . . 9
B.2.3. Referral Compatibility . . . . . . . . . . . . . . . 10
B.2.4. Architectual Violations . . . . . . . . . . . . . . . 10
B.3. RDAP Extension Versioning . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Background
[RFC7480] defines the 'application/rdap+json' media type to be used
with RDAP. This document defines a new media type to be used in
conjuction with the current media type when an RDAP extension needs
to be described during HTTP content negotiation.
2. RDAP-X: The RDAP With Extensions Media Type
The media type defined by this document is 'application/rdap-x+json'.
This media type has a parameter of "extensions" which is a
whitespace-separated list of RDAP extensions as defined in the IANA
RDAP Extensions registry.
Here is an example:
application/rdap-x+json;extensions="rdap_level_0 fred"
For readability, this document will refer to this media type, RDAP
With Extensions, as RDAP-X.
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3. Using The RDAP-X Media Type
[RFC7480] specifies the usage of 'application/json', 'application/
rdap+json' or both with HTTP accept header. When using the media
type defined by this document, the 'application/rdap+json' media type
MUST also be used in the accept header.
An example:
accept: application/rdap+json;q=0.9,
application/rdap-x+json;extensions="rdap_level_0 rdapx fred";q=1
When a server is programmed to understand the RDAP-X media type, it
SHOULD respond with this media type in the content-type header. By
doing so, clients will be able to detect if the server recognizes the
media type. Otherwise, the server will use the 'application/
rdap+json' media type signalling to the client that the RDAP-X media
type is not recognized by the server. This updates the usage of the
content-type header with RDAP defined in RFC 7480, but this usage is
backward compatible.
If both a client and server support the RDAP-X media type, and the
client requests an extension that is unimplemented by the server, the
server SHOULD respond with the RDAP-X media type using only
extensions implemented by the server. This behavior is backward
compatible as RDAP clients must ignore unknown extensions as
specified by [RFC9083]. Responding with an HTTP 406 Not Acceptable
status code is NOT RECOMMENDED.
When the RDAP-X media type is used in the content-type header, the
values in the media type's extension parameter SHOULD match the
values in the rdapConformance array in the return JSON. When there
is a mismatch between extension parameters and the rdapConformance
array, clients SHOULD give preference to the rdapConformance array.
Just as servers should not put extensions into the rdapConformance
array for which they do not support, servers SHOULD NOT list
extensions in the RDAP-X media type for which they do not support.
Nothing in this specification sidesteps or obviates the HTTP content
negotiation defined in [RFC9110] for RDAP. Specifically, if a client
gives RDAP-X a lower qvalue than any other media type, that is a
signal not to use RDAP-X.
Likewise, nothing in this specification sidesteps or obviates the
HTTP caching mechanisms defined in [RFC9110]. Further advice on the
vary header may be found in Appendix A.
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Some RDAP extensions, such as [I-D.ietf-regext-rdap-openid], have
other protocol elements passed from the client to the server, and the
presence of these protocol elements may be used by servers to
determine a client's capability to handle the RDAP extension. This
specification does not require the usage of those extensions
identifiers in the extensions parameter, though clients SHOULD list
the extension identifier in the extensions parameter when using other
protocol elements of those extensions. Servers SHOULD NOT require
the usage of extension identifiers in the extensions paramater when
other extension protocol elements are used.
4. Usage in RDAP Links
Section 4.2 of [RFC9083] defines a link structure used in RDAP.
{
"value" : "https://example.com/context_uri",
"rel" : "self",
"href" : "https://example.com/target_uri",
"hreflang" : [ "en", "ch" ],
"title" : "title",
"media" : "screen",
"type" : "application/json"
}
The type attribute signals to a client the expected media type of the
resource referenced in the href attribute, and some clients use this
information to determine if the URI in the href attribute should be
dereferenced.
Servers MAY use the RDAP-X media type in the type attribute if a
client has negotiated content with the server using the RDAP-X media
type, the resource referenced by the URI matches the RDAP-X media
type, and the resource referenced by the URI is served by a server
compliant with this specification. Otherwise, use of the
application/rdap+json media type is RECOMMENDED when the URI
references RDAP resources.
5. RDAP-X Extension
This document defines an RDAP "profile" extension using the
identifier "rdapx" (hyphen characters are not allowed in RDAP
extension identifiers). This RDAP extension defines no additional
RDAP queries or response structures.
The purpose of this RDAP extension is to allow servers to signal
support for RDAP-X in rdapConformance arrays of responses to /help
(aka "service discovery").
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6. Security Considerations
As stated in Section 3, this specification does not override the
protocol elements of RDAP security extensions, such as
[I-D.ietf-regext-rdap-openid], nor does it override the protocol
elements of other security features of HTTP.
This specification does contrast with solutions using query
parameters in that those solutions require servers to blindly copy
query parameters into redirect URLs in situations where such copying
could cause harm, such as copying an API key intended for one server
into the redirect URL of another server.
7. IANA Considerations
Type name: application
Subtype name: rdap-x+json
Required parameters: This media type has a parameter of "extensions"
which is a whitespace-separated list of RDAP extensions as defined in
the IANA RDAP Extensions registry.
Optional parameters: N/A
Encoding considerations: See Section 3.1 of [RFC6839].
Security considerations: The media represented by this identifier
does not have security considerations beyond that found in Section 12
of [RFC8259].
Interoperability considerations: There are no known interoperability
problems regarding this media format.
Published specification: This document.
Applications that use this media type: Implementations of the
Registration Data Access Protocol (RDAP) with Extensions.
Additional information: This media type is a product of the IETF
REGEXT Working Group. The REGEXT charter, information on the REGEXT
mailing list, and other documents produced by the REGEXT Working
Group can be found at https://datatracker.ietf.org/wg/regext/
(https://datatracker.ietf.org/wg/regext/).
Person & email address to contact for further information: IESG
<iesg&ietf.org>
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Intended usage: COMMON
Restrictions on usage: none
Author: Andy Newton
Change controller: IETF
Provisional Registration: No
8. Acknowledgements
Pawel Kowalik and James Mitchell have provided ideas and feedbacks
that have contributed to the content of this document.
9. References
9.1. Normative References
[RFC6839] Hansen, T. and A. Melnikov, "Additional Media Type
Structured Syntax Suffixes", RFC 6839,
DOI 10.17487/RFC6839, January 2013,
<https://www.rfc-editor.org/info/rfc6839>.
[RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 7480, DOI 10.17487/RFC7480, March 2015,
<https://www.rfc-editor.org/info/rfc7480>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
9.2. Informative References
[I-D.ietf-regext-rdap-openid]
Hollenbeck, S., "Federated Authentication for the
Registration Data Access Protocol (RDAP) using OpenID
Connect", Work in Progress, Internet-Draft, draft-ietf-
regext-rdap-openid-27, 5 November 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-regext-
rdap-openid-27>.
[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,
<https://www.rfc-editor.org/info/rfc3986>.
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[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.
[RFC9083] Hollenbeck, S. and A. Newton, "JSON Responses for the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 9083, DOI 10.17487/RFC9083, June 2021,
<https://www.rfc-editor.org/info/rfc9083>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
Appendix A. Using the Vary Header
Server implementers may want to consider using the vary header
depending on the caching behavior desired of shared caches (i.e.
middleboxes, not client caches).
Consider the following scenario where user Bob and user Alice send
queries to the same RDAP server that is routed through a middlebox
network element implementing a shared HTTP cache.
User Bob sends a query for the domain example.com
(http://regy.example/domain/example.com (http://regy.example/domain/
example.com)) without RDAP-X. The accept header sent for Bob's query
would be accept: application/rdap+json or accept: application/json.
User Alice later sends a query for the same domain, however her
client uses RDAP-X. The accept header returned by Alice might be
accept: application/rdap-x+json, application/rdap+json.
If no vary header is set in the response for these queries, the
shared cache will compare only the URL of the query when processing
cache items and therefore user Bob and user Alice would receive the
same answer. In other words, since both queried
http://regy.example/domain/example.com the shared cache would return
the answer of the first query to the second query and all other
subsequent queries until the item expired out of the cache.
If server implementers do not desire this behaviour and would signal
that caches consider each query separately, servers should also
return a vary: accept header to inform the cache that the accept
header should also be considered when processing cache items. Server
implementers should also consult [RFC9110] regarding caching and
other uses of the vary header.
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Appendix B. Design Considerations
B.1. Not Reusing the Existing Media Type
Section 4.3 of [RFC6838] strongly discourages the creation of new
parameters on existing media types to enable new features. As RDAP
has always had extensions, it could be argued that adding an
"extensions" parameter to the existing application/rdap+json media
type is not adding a new feature to RDAP. However, the opposite
could be argued that adding the capability for clients to signal
desired RDAP extensions is a new feature.
More practically, there is concern that adding a new parameter to the
existing media type would not be backward compatible with some server
software. That is, servers examining media types as exact string
matches may incorrectly conclude that the existing media type with an
unknown, new parameter may not be the same as the existing media type
without parameters. A similar, though less likely, concern exists
for clients.
As servers are required to handle multiple media types according to
[RFC7480] and [RFC9110], it therefore seems reasonable to conclude
that defining a new media type for use with the existing media type
is best to preserve backward compatibility.
B.2. Query Parameters Considered Harmful
Another design approach to communicating RDAP extensions from the
client to the server would be the use of URI query parameters:
https://rdap.example/domain/foo.example?extensions=fizzbuzz
B.2.1. Copy and Paste
Consider two RDAP users, Alice and Bob. Alice has an RDAP client that
supports the extensions "fizzbuzz", and Bob has an RDAP client that
does not support this extension.
Now consider the scenario where Alice copies and pastes the RDAP URL
from above into an email and sends it to Bob. When Bob uses that URL
with his RDAP client, it will be communicating to the server that the
extension "fizzbuzz" is understood by Bob's client when it is not.
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In this scenario, Bob's client will be unable to render the RDAP
extension regardless of the usage or not of the query parameter.
However, if the server is using the query parameter for secondary
purposes, such as gathering metrics and statistics, then the
capabilities of Bob's client will have been incorrectly signalled to
the server.
B.2.2. Redirects
The RDAP ecosystem uses redirects in many situations. [RFC7480]
discusses "aggregators", which are RDAP servers used to help clients
find authoritative RDAP servers using the RDAP bootstrap registries.
Redirects are also heavily used by the RIRs when IP addresses or
autonomous system numbers are transferred from one RIR to another.
Within HTTP, URI query parameters are not explicitly preserved during
a redirect (probably due to architecture considerations, see the
section below). Specific to RDAP, [RFC7480] instructs RDAP servers
to ignore unknown query parameters and instructs clients not to
transform a URL of a redirect.
Therefore, query parameters denoting RDAP extensions will not survive
redirects. This can be readily observed in currently deployed RDAP
servers:
curl -v https://rdap-bootstrap.arin.net/bootstrap/autnum/2830?extension=fizzbuzz
To further demonstrate that query parameters do not automatically
survive redirects but that media types do, consider the code found
here (https://github.com/anewton1998/draft-regext-ext-json-media-
type). This code consists of a simple client and a simple server.
The client sets both a new media type and query parameters. The
servers listens on two ports, redirecting the client from a URL on
the first port to a URL on the second port.
Here is the output of the client. It shows that the query parameters
are not automatically preserved but that the media type is
automatically preserved.
2024-01-05T11:15:34.380989Z INFO client: sending reqwest to http://127.0.0.1:3000/ex1/domain/foo.example?foo&bar
2024-01-05T11:15:34.431386Z INFO client: returned content type: "application/rdap-x;extensions=\"foo bar\""
2024-01-05T11:15:34.431413Z INFO client: status code is 418 I'm a teapot
2024-01-05T11:15:34.431476Z INFO client: response is {"errorCode":418,"title": "Your Beverage Choice is Not Available"}
Here is the output of the server. It show that the client, upon
redirect, automatically sends the media type but does not
automatically preserve the query parameters.
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2024-01-05T11:15:31.071936Z INFO servers: starting server on port 3000
2024-01-05T11:15:31.071961Z INFO servers: starting server on port 4000
2024-01-05T11:15:34.429595Z INFO servers: [redirecting server] Serving request from 127.0.0.1:60260
2024-01-05T11:15:34.429648Z INFO servers: [redirecting server] received query parameters: 'bar', 'foo'
2024-01-05T11:15:34.429682Z INFO servers: [redirecting server] client signaled RDAP extension 'foo'
2024-01-05T11:15:34.429693Z INFO servers: [redirecting server] client signaled RDAP extension 'bar'
2024-01-05T11:15:34.429704Z INFO servers: [redirecting server] redirecting to http://127.0.0.1:4000/ex2/domain/foo.example
2024-01-05T11:15:34.430940Z INFO servers: [authoritative server] Serving request from 127.0.0.1:40840
2024-01-05T11:15:34.430967Z INFO servers: [authoritative server] received query parameters:
2024-01-05T11:15:34.430983Z INFO servers: [authoritative server] client signaled RDAP extension 'foo'
2024-01-05T11:15:34.430989Z INFO servers: [authoritative server] client signaled RDAP extension 'bar'
2024-01-05T11:15:34.430995Z INFO servers: [authoritative server] responding with an unuseful error
Preservation of query parameters is not a guaranteed feature of HTTP
client and server libraries, whereas preservation of media types is.
B.2.3. Referral Compatibility
It is common in the RDAP ecosystem to link from one RDAP resource to
another. These are typically conveyed in the link structure defined
in Section 4.2 of [RFC9083] and use the "application/rdap+json" media
type. One common usage is to link to a domain registration in a
domain registrar from a domain registration in a domain registry.
{
"value" : "https://regy.example/domain/foo.example",
"rel" : "related",
"href" : "https://regr.example/domain/foo.example",
"type" : "application/rdap+json"
}
Usage of the RDAP-X media type does not require clients to conduct
further processing of these referrals, whereas a query parameter
approach would require clients to process and deconflict any other
query parameters if present.
B.2.4. Architectual Violations
As noted in [RFC3986], URI query parameters are meant to be part of
the identity of the resource being identified by a URI and pointed to
by the location of a URL. RDAP extensions change the portions of
JSON returned by the server but are not intended to change the
resource being identified. That is, a domain registration is the
same domain registration regardless of whether the postal address in
that domain registration is communicated via JCard or a new RDAP
extension for JSContact.
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Changing how the content of a resource is conveyed is called content
negotiation and is discussed in detail in [RFC9110] using media
types.
Readers should note that protocol design is not a "priestly affair"
in which architectural violations are strictly forbidden. Every
design decision is a trade-off. However, following the architecture
of an ecosystem generally makes re-use of software and systems
easier, and often eases the adoption of newer features in the future.
When given the choice between two designs, the design that does not
violate architecture should be preferred when all other
considerations are equal.
B.3. RDAP Extension Versioning
It is beyond the scope of this document to define the versioning of
RDAP extensions. However, there is design intent to allow the use of
explicitly versioned RDAP extension identifiers where they are also
compatible with the identifiers used in the rdapConformance array of
RDAP.
Consider the scenario in which the IETF decides that RDAP extension
identifiers suffixed with the character string __V denotes RDAP
extensions versioned using a semantic versioning scheme. In this
scenario, the RDAP extension identifier fizzbuzz__V is registered
with IANA. The __V suffix indicates that when the identifier is used
in the rdapConformance array, it must appear appended with a
character string denoting the semantic version of the extension.
For example, fizzbuzz__V_2_1 denotes version 2.1 of the fizzbuzz
extension. In RDAP JSON, the conformance would appear as:
"rdapConformance" : [
"rdap_level_0",
"fizzbuzz__V_2_1"
]
The usage with the rdap-x media type would be:
application/rdap-x+json;extensions="rdap_level_0 fizzbuzz__V_2_1"
Readers should note that this scenario is provided to show design
intent and is not a full-fledged extension versioning design.
Additionally, the new media type defined in this document has utility
with existing, opaquely versioned RDAP extensions and does not depend
on the definition of a new versioning scheme for RDAP extensions.
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Authors' Addresses
Andy Newton
ICANN
Email: andy@hxr.us
Jasdip Singh
ARIN
Email: jasdips@arin.net
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