Network Working Group M. Jones
Internet-Draft Y. Goland
Intended status: Standards Track Microsoft
Expires: May 9, 2013 November 5, 2012
Simple Web Discovery (SWD)
draft-jones-simple-web-discovery-04
Abstract
Simple Web Discovery (SWD) defines an HTTPS GET based mechanism to
discover the location of a given type of service for a given
principal starting only with a domain name.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 3
2. Simple Web Discovery Request . . . . . . . . . . . . . . . . . 3
2.1. "simple-web-discovery" Subdomain . . . . . . . . . . . . . 4
3. Simple Web Discovery Responses . . . . . . . . . . . . . . . . 5
3.1. Response Containing One or More Locations . . . . . . . . . 5
3.2. 401 Unauthorized Response . . . . . . . . . . . . . . . . . 5
3.3. Other HTTP 1.1 Responses . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Document History . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
Simple Web Discovery (SWD) defines an HTTPS GET based mechanism to
discover the location of a given type of service for a given
principal starting only with a domain name. SWD requests use query
parameters to specify a URI for the principal and another URI for the
type of service being sought. If the request is successful then the
response, by default, is a JavaScript Object Notation (JSON)
[RFC4627] object containing an array of URIs that point to where the
principal has instances of services of the requested type.
For example, let us say that a requester wants to discover where Joe
keeps his calendar. The requester could take Joe's e-mail address,
"joe@example.com", and use its domain to create an HTTPS GET request
of the following form (with long lines broken for display purposes
only):
GET /.well-known/simple-web-discovery
?principal=joe@example.com
&service=urn:example:service:calendar HTTP/1.1
Host: example.com
HTTP/1.1 200 OK
Content-Type: application/json
{
"locations": ["https://calendars.example.net/calendars/joseph"]
}
Note: The request-URI is left unencoded in the above example for the
sake of readability. The query parameters above would actually be
encoded as "?principal=joe%40example.com&service=urn%3Aexample%3Aserv
ice%3Acalendar".
1.1. Notational Conventions
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 Key words for use in
RFCs to Indicate Requirement Levels [RFC2119].
2. Simple Web Discovery Request
Domains that support SWD requests SHOULD make an SWD server available
for their domain at the path "/.well-known/simple-web-discovery".
The syntax and semantics of "/.well-known" are defined in RFC 5785
[RFC5785]. "/.well-known/simple-web-discovery" MUST point to an SWD
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server compliant with this specification.
SWD servers MUST support receiving SWD requests via TLS 1.2 [RFC5246]
and MAY support other transport layer security mechanisms of
equivalent security. SWD servers MUST reject SWD requests sent over
plain HTTP or any other transport that does not provide both privacy
and validation of the server's identity.
An SWD server is queried using an HTTPS GET request with the
previously specified path along with a query segment containing a
form encoded using the application/x-www-form-urlencoded encoding
algorithm as defined in HTML 4.01 [W3C.REC-html401-19991224]. The
form MUST contain two name/value pairs that MUST appear exactly once,
"principal" and "service". Both name/value pairs MUST have values
that are set to URIs [RFC3986]. If any of the previous requirements
are not met in an SWD request, then the request MUST be rejected with
a 400 Bad Request.
The SWD request form MAY contain additional name/value pairs but if
those name/value pairs are not recognized by the SWD server then the
SWD server MUST ignore them for processing purposes.
The "principal" query component is a URI that identifies an entity.
The "service" query component is a URI that identifies a service
type. The semantics of the SWD query is "Please return the
location(s) of instances of the specified service type associated
with the specified principal". The definition of URIs used to
identify principals and services are outside the scope of this
specification.
SWD servers MAY also be located on ports other than 443 (the default
HTTPS port), provided they use TLS on those ports. The means by
which an SWD client would know to use any alternative ports are out
of scope for this specification.
2.1. "simple-web-discovery" Subdomain
It may be difficult or impossible for some domains wanting to support
SWD requests to make an SWD server available for their domain at the
path "/.well-known/simple-web-discovery". For instance, in the case
of hosted domains, no web server may be running on the domain host at
all.
For that reason, SWD servers for a domain MAY be located on a
specific subdomain of that domain: "simple-web-discovery". For
example, the SWD server for the domain "example.com" MAY be located
at the URI "https://simple-web-discovery.example.com/.well-known/simp
le-web-discovery".
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SWD clients MUST first attempt to make an SWD request to the domain's
"/.well-known/simple-web-discovery" endpoint, and then if that fails,
they MUST then attempt to make the request to the SWD endpoint at the
"simple-web-discovery" subdomain for the domain.
3. Simple Web Discovery Responses
3.1. Response Containing One or More Locations
A 200 OK response to an SWD request that contains the information
requested MUST return content of type application/json [RFC4627].
The JSON response MUST contain a JSON object that contains a member
pair whose name is the string "locations" and whose value is an array
of strings that are each a URI pointing to a location where the
desired service type belonging to the specified principal can be
found. There are no semantics associated with the order in which the
URIs are listed in the array.
The JSON object MAY contain other members but a receiver of the
object MAY ignore any member pairs whose name it does not recognize.
3.2. 401 Unauthorized Response
An SWD server MAY respond to a request with a 401 Unauthorized
Response, as described in RFC 2616 [RFC2616], Section 10. Per the
RFC, the request MAY be repeated with a suitable Authorization header
field. Authorization information may be communicated in this manner,
including a JSON Web Token [JWT].
3.3. Other HTTP 1.1 Responses
An SWD server MAY return other HTTP 1.1 responses, including 404 Not
Found, 400 Bad Request, and 403 Forbidden. SWD implementations MUST
correctly handle these responses.
4. IANA Considerations
This specification registers a well-known URI suffix value relative
to "/.well-known/" in the IANA Well-Known URI registry defined in RFC
5785 [RFC5785]:
URI suffix: simple-web-discovery
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Change controller: IETF
Specification document: [[ this document ]]
5. Security Considerations
SWD responses can contain confidential information. Therefore a,
general approach is used to require TLS in all cases. But TLS can
only provide for privacy and server validation, it cannot validate
that the requester is authorized to see the results of a query. The
exact mechanism used to determine if the requester is authorized to
see the result of the query is outside the scope of this
specification.
Because SWD responses can contain confidential information, the
requestor may need authorization to receive them. Standard HTTP
authorization mechanisms MAY be employed to request authorized
access, including the use of an HTTP Authorization header field in
requests, which in turn, may contain a JSON Web Token [JWT], among
other authorization data formats.
When the SWD server for a domain is located at the
"simple-web-discovery" subdomain, a TLS certificate will need to be
present for that subdomain.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
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[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
April 2010.
[W3C.REC-html401-19991224]
Hors, A., Raggett, D., and I. Jacobs, "HTML 4.01
Specification", World Wide Web Consortium
Recommendation REC-html401-19991224, December 1999,
<http://www.w3.org/TR/1999/REC-html401-19991224>.
6.2. Informative References
[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", October 2012.
Appendix A. Document History
[[ to be removed by the RFC editor before publication as an RFC ]]
-04
o Specified that the SWD server for a domain may be located at the
"simple-web-discovery" subdomain of the domain and that SWD
clients must first try the endpoint at the domain and then the
endpoint at the subdomain.
o Removed the "SWD_service_redirect" response, since redirection can
be accomplished by pointing the "simple-web-discovery" subdomain
to a different location than the domain's host.
o Removed "mailto:" from examples in favor of bare e-mail address
syntax.
o Specified that SWD servers may also be run on ports other than
443, provided they use TLS on those ports.
-03
o Changed "requests use the x-www-form-urlencoded format" to
"requests use query parameters" and changed "an x-www-form-
urlencoded form" to "a form encoded using the application/
x-www-form-urlencoded encoding algorithm", both at the suggestion
of Julian Reschke.
o Updated examples to use "urn:example:" URNs rather than
"urn:example.org:" URNs, also at Julian's suggestion.
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o Applied applicable editorial improvements from JOSE specs to SWD.
o Updated references to related specifications.
-02
o Update examples to use example.{com,net,org} domain names.
o Provide encoded representation of the request-URI query parameters
for the first example request.
o Changed "200 O.K." to "200 OK".
o Respect line length restrictions in examples.
o No normative changes.
-01
o Refresh draft before expiration of -00. No normative changes.
-00
o Initial version.
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
Yaron Y. Goland
Microsoft
Email: yarong@microsoft.com
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