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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en"><head><title>OAuth Dynamic Client Registration Protocol</title>
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<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<table summary="layout" width="66%" border="0" cellpadding="0" cellspacing="0"><tr><td><table summary="layout" width="100%" border="0" cellpadding="2" cellspacing="1">
<tr><td class="header">Network Working Group</td><td class="header">C. Scholz, Ed.</td></tr>
<tr><td class="header">Internet-Draft</td><td class="header">COM.lounge GmbH</td></tr>
<tr><td class="header">Intended status: Standards Track</td><td class="header">M. Machulak</td></tr>
<tr><td class="header">Expires: February 12, 2011</td><td class="header">Newcastle University</td></tr>
<tr><td class="header"> </td><td class="header">E. Maler</td></tr>
<tr><td class="header"> </td><td class="header">PayPal</td></tr>
<tr><td class="header"> </td><td class="header">August 11, 2010</td></tr>
</table></td></tr></table>
<h1><br />OAuth Dynamic Client Registration Protocol<br />draft-oauth-dyn-reg-v1-00.txt</h1>
<h3>Abstract</h3>
<p>
This specification proposes an OAuth Dynamic Client Registration protocol.
</p>
<h3>Status of this Memo</h3>
<p>
This Internet-Draft is submitted in full
conformance with the provisions of BCP 78 and BCP 79.</p>
<p>
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current
Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.</p>
<p>
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.”</p>
<p>
This Internet-Draft will expire on February 12, 2011.</p>
<h3>Copyright Notice</h3>
<p>
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.</p>
<p>
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.</p>
<a name="toc"></a><br /><hr />
<h3>Table of Contents</h3>
<p class="toc">
<a href="#anchor1">1.</a>
Introduction<br />
<a href="#anchor2">1.1.</a>
Notational Conventions<br />
<a href="#anchor3">1.2.</a>
Terminology<br />
<a href="#anchor4">2.</a>
Use Cases<br />
<a href="#anchor5">3.</a>
Requirements<br />
<a href="#anchor6">3.1.</a>
The client needs to be uniquely identifiable by the authorization server<br />
<a href="#anchor7">3.2.</a>
The authorization server must collect metadata about a client for later user interaction<br />
<a href="#anchor8">3.3.</a>
The authorization server must have the option of strongly
authenticating the client and its metadata<br />
<a href="#anchor9">3.4.</a>
Dynamic client registration must be possible from both web-server applications
and applications with other capabilities and limitations, such as native applications<br />
<a href="#anchor10">3.5.</a>
Transaction integrity must be ensured in large deployments where data
propagation can be an issue<br />
<a href="#anchor11">3.6.</a>
UMA design principles and requirements<br />
<a href="#anchor12">4.</a>
Analysis of Registration Flow Options<br />
<a href="#anchor13">5.</a>
Discovery of Server's Client Registration Endpoint<br />
<a href="#anchor14">6.</a>
Client Registration with Pushed Metadata<br />
<a href="#anchor15">6.1.</a>
Client Registration Request<br />
<a href="#anchor16">6.2.</a>
Client Registration Response<br />
<a href="#anchor17">6.3.</a>
Error Response<br />
<a href="#anchor18">7.</a>
Client Registration with Pushed URL and Pulled Metadata<br />
<a href="#anchor19">7.1.</a>
Client Registration Request<br />
<a href="#anchor20">7.2.</a>
Client Discovery<br />
<a href="#anchor21">7.3.</a>
Client Registration Response<br />
<a href="#anchor22">7.4.</a>
Error Response<br />
<a href="#anchor23">8.</a>
Native Application Client Registration<br />
<a href="#anchor24">9.</a>
Security Considerations<br />
<a href="#anchor25">Appendix A.</a>
Acknowledgements<br />
<a href="#anchor26">Appendix B.</a>
Document History<br />
<a href="#rfc.references1">10.</a>
References<br />
<a href="#rfc.references1">10.1.</a>
Normative References<br />
<a href="#rfc.references2">10.2.</a>
Non-Normative References<br />
<a href="#rfc.authors">§</a>
Authors' Addresses<br />
</p>
<br clear="all" />
<a name="anchor1"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.1"></a><h3>1.
Introduction</h3>
<p>
This informal draft discusses a number of requirements for and approaches to
automatic registration of clients with an OAuth authorization server, with special
emphasis on the needs of the OAuth-based User-Managed Access protocol <a class='info' href='#UMA-Core'>[UMA‑Core]<span> (</span><span class='info'>Scholz, C., “UMA Requirements,” 2010.</span><span>)</span></a>.
</p>
<p>
In some use-case scenarios it is desirable or necessary to allow OAuth clients to
obtain authorization from an OAuth authorization server without the two parties
having previously interacted. Nevertheless, in order for the authorization server
to accurately represent to end-users which client is
seeking authorization to access the end-user's resources, a method for automatic
and unique registration of clients is needed.
</p>
<p>
The goal of this proposed registration protocol is for an authorization server to provide a client with a
client identifier and optionally a client secret in a dynamic fashion. To accomplish this,
the authorization server must first be provided with
information about the client, with the client-name being the minimal information
provided. In practice, additional information will need to be furnished to
the authorization server, such as the client's homepage, icon, description, and
so on.
</p>
<p>
The dynamic registration protocol proposed here is envisioned to be an additional
task to be performed by the OAuth authorization server, namely registration of a new
client identifier and optional secret and the issuance of this information to
the client. This task would occur prior to the point at which the client
wields its identifier and secret at the authorization server in order to obtain an access
token in normal OAuth fashion.
</p>
<a name="anchor2"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.1.1"></a><h3>1.1.
Notational Conventions</h3>
<p>
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 <a class='info' href='#RFC2119'>[RFC2119]<span> (</span><span class='info'>Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.</span><span>)</span></a>.
</p>
<p>
Unless otherwise noted, all the protocol parameter names and values are case sensitive.
</p>
<a name="anchor3"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.1.2"></a><h3>1.2.
Terminology</h3>
<p>
</p>
<blockquote class="text"><dl>
<dt>resource server</dt>
<dd>
A server capable of accepting and responding to protected resource requests.
</dd>
<dt>resource owner</dt>
<dd>
An entity capable of granting access to a protected resource.
</dd>
<dt>client</dt>
<dd>
An application obtaining authorization and making protected resource requests.
</dd>
<dt>authorization server</dt>
<dd>
A server capable of issuing tokens after successfully authenticating the resource
owner and obtaining authorization. The authorization server may be the same server as
the resource server, or a separate entity.
</dd>
<dt>authorization manager</dt>
<dd>
An UMA-defined variant of an authorization server that carries out an authorizing
user's policies governing access to a protected resource.
</dd>
<dt>end-user authorization endpoint</dt>
<dd>
The authorization server's HTTP endpoint capable of authenticating the end-user and
obtaining authorization.
</dd>
<dt>token endpoint</dt>
<dd>
The authorization server's HTTP endpoint capable of issuing tokens and refreshing
expired tokens.
</dd>
<dt>client identifier</dt>
<dd>
An unique identifier issued to the client to identify itself to the authorization
server. Client identifiers may have a matching secret.
</dd>
<dt>client registration endpoint</dt>
<dd>
The authorization server's HTTP endpoint capable of issuing client identifiers and
optional client secrets.
</dd>
</dl></blockquote><p>
</p>
<a name="anchor4"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.2"></a><h3>2.
Use Cases</h3>
<p>
The UMA protocol involves two instances of OAuth flows. In the first, an end-user introduces
a host (essentially an enhanced OAuth resource server) to an authorization manager (an enhanced OAuth authorization
server) as a client of it, possibly without that host having obtained client identification information from that server
previously. In the second, a requester (an enhanced OAuth client) approaches a host and
authorization manager to get and use an access token in approximately the normal OAuth fashion, again possibly without
that client having obtained client identification information from that server previously.
Both the host-as-client and the requester-as-client thus
may need dynamic client registration in order for the UMA protocol flow to proceed.
</p>
<p>
The needs for inter-party trust vary in different UMA use cases. In lightweight Web circumstances such as
person-to-person calendar sharing, dynamic registration is entirely appropriate. In cases where high-sensitivity
information is being protected or where a regulatory environment puts constraints on the building of trust
relationships, such as sharing health records with medical professionals or giving access to tax records to outsourced
bookkeeping staff, static means of provisioning client identifiers may be imposed.
</p>
<p>
More information about UMA use cases is available at <a class='info' href='#UMA-UC'>[UMA‑UC]<span> (</span><span class='info'>Akram, H., “UMA Explained,” 2010.</span><span>)</span></a>.
</p>
<a name="anchor5"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3"></a><h3>3.
Requirements</h3>
<p>
Following are proposed requirements for dynamic client registration.
</p>
<a name="anchor6"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3.1"></a><h3>3.1.
The client needs to be uniquely identifiable by the authorization server</h3>
<p>
In order for an authorization server to do proper user-delegated authorization
and prevent unauthorized access it must be able to identify clients uniquely.
As is done today in OAuth, the client identifier (and optional secret) should
thus be issued by the authorization server and not simply accepted as proposed by the client.
</p>
<a name="anchor7"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3.2"></a><h3>3.2.
The authorization server must collect metadata about a client for later user interaction</h3>
<p>
In order for the authorization server to describe a client to an end-user in an
authorization step it needs information about the client. This can be the client
name at a minimum, but today servers usually request at least a description, a
homepage URL, and an icon when doing manual registration.
</p>
<a name="anchor8"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3.3"></a><h3>3.3.
The authorization server must have the option of strongly
authenticating the client and its metadata</h3>
<p>
In order to prevent spoofing of clients and enable dynamic building of strong trust relationships,
the authorization server should have the option to verify the provided information. This might be
solved using message signature verification; relatively weaker authentication might be achieved in a
simpler way by pulling metadata from a trusted client URL.
</p>
<a name="anchor9"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3.4"></a><h3>3.4.
Dynamic client registration must be possible from both web-server applications
and applications with other capabilities and limitations, such as native applications</h3>
<p>
In the UMA context, alternative types of applications might serve as both hosts (for example, as a device-based
personal data store) and requesters (for example, to subscribe to a calendar or view a photo).
Such applications, particularly native applications, may have special limitations, so new solutions
to meeting the set of requirements presented here may be needed. We anticipate that each instance of a
native application (that is, the specific instance running on each device)
that is installed and run by the same user may need the option of getting a unique client identifier. In this case,
there are implications around gathering and displaying enough information to ensure that the end-user is delegating
authorization to the intended application.
</p>
<a name="anchor10"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3.5"></a><h3>3.5.
Transaction integrity must be ensured in large deployments where data
propagation can be an issue</h3>
<p>
When a client sends information to a server endpoint, it might take time for this data
to propagate through big server installations that
spread across various data centers. Care needs to be taken that subsequent interactions with the user after the
registration process, such as an authorization request, show the correct data.
</p>
<p>
In the UMA context, dynamic registration of a host at an AM is almost certain to take place in the middle of
an introduction and authorization process mediated by the end-user; even though the host needs a client identifier
from the AM no matter which end-user
caused the registration process to take place, the end-user may need to wait for the registration sub-process
to finish in order to continue with the overall process. It may be
necessary to ensure that the host interacts with the same AM server throughout.
</p>
<a name="anchor11"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.3.6"></a><h3>3.6.
UMA design principles and requirements</h3>
<p>
In addition to general requirements for dynamic client registration, UMA seeks to optimize
for the design principles and requirements found in the UMA Requirements document
<a class='info' href='#UMA-Reqs'>[UMA‑Reqs]<span> (</span><span class='info'>Maler, E., “UMA Requirements,” 2010.</span><span>)</span></a>, most particularly:
</p>
<ul class="text">
<li>
DP1: Simple to understand, implement in an interoperable fashion, and deploy on an Internet-wide scale
</li>
<li>
DP6: Able to be combined and extended to support a variety of use cases and emerging application functionality
</li>
<li>
DP8: Avoid adding crypto requirements beyond what existing web app implementations do today
</li>
<li>
DP10: Complexity should be borne by the authorization endpoint vs. other endpoints
</li>
</ul><p>
</p>
<a name="anchor12"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.4"></a><h3>4.
Analysis of Registration Flow Options</h3>
<p>
This section analyzes some options for exchanging client metadata
for a client identifier and optional secret.
</p>
<p>It currently seems impossible to specify a single registration flow that will satisfy all
requirements, deployment needs, and client types. This document, therefore, presents as
small a variety of options as possible. If it is possible to construct a single unified flow in the ultimate
design, all other things being equal this would be preferred.
</p>
<p>
</p>
<blockquote class="text"><dl>
<dt>Client provides metadata on every request</dt>
<dd>
In this approach, the client passes all necessary metadata such as its name and
icon on every request to the authorization server, and the client doesn't wield a client identifier as such.
This option makes it more difficult (though not impossible) to meet the first and second requirements since different
clients could theoretically represent themselves to an authorization server with the same metadata
and the same client could represent itself on subsequent visits with different metadata.
Also, today's OAuth protocol requires the use of a client identifier. Because of the UMA
simplicity principle we do not recommend this flow option and
and have not provided a candidate solution.
</dd>
<dt>Client pushes metadata</dt>
<dd>
In this approach, the client discovers the registration endpoint of
the authorization server and sends its metadata directly to that endpoint in a standard format. The
authorization server answers with a client identifier and optional secret in the response. This approach may be
necessary in cases where the client is behind a firewall, but strong authentication
of the client metadata may be more difficult or costly with this approach than with a "pull" approach, discussed
just below.
Further, this approach is problematic in the case of applications that can't function as POST-capable web servers.
A proposal for "push" is presented in this document.
</dd>
<dt>Client pushes URL, server pulls metadata from it</dt>
<dd>
In this approach, the client sends only a URL to the authorization server, which then uses that
URL to pull metadata about the client in some standard format, returning identification information
in the response to the initial request. This approach more easily allows for strong
authentication of clients because the metadata can be statically signed. (The message containing the
URL could be signed as well.) However, caution should be exercised around the propagation issue if the initial
URL push is made to a server different from the one the end-user is interacting with. Further,
this approach is problematic in the case of applications that cannot themselves serve as "pull-able"
metadata repositories.
A proposal for "pull" is presented in this document.
</dd>
<dt>Native-app client collaborates with home-base web app to provide metadata</dt>
<dd>
An instance of a native application (for example, on a mobile device) may have difficulty directly conveying
trustworthy metadata
but may also have difficulty providing a trustworthy third-party source from which a server can pull metadata.
This document explores one option for meeting the requirements, but does not present a full-fledged proposal.
</dd>
</dl></blockquote><p>
</p>
<a name="anchor13"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.5"></a><h3>5.
Discovery of Server's Client Registration Endpoint</h3>
<p>
Regardless of flow option, the client needs to discover the authorization server's client registration endpoint.
</p>
<p>
The client MUST use the <a class='info' href='#RFC5785'>[RFC5785]<span> (</span><span class='info'>Nottingham, M. and E. Hammer-Lahav, “Defining Well-Known Uniform Resource Identifiers (URIs),” April 2010.</span><span>)</span></a> and <a class='info' href='#hostmeta'>[hostmeta]<span> (</span><span class='info'>Hammer-Lahav, E., “Web Host Metadata,” 2010.</span><span>)</span></a> discovery mechanisms to learn
the URI of the client registration endpoint at the authorization server.
The authorization server MUST provide a host-meta document containing a Link element with a rel value of: <tt>http://oauth.net/as/registration</tt>
</p>
<p>
For example:
</p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
<XRD>
<Host>http://server.example.com</Host>
<Link rel="http://oauth.net/as/registration"
href="https://server.example.com/register">
<Title>Client Registration Endpoint</Title>
</Link>
</XRD>
</pre></div>
<a name="anchor14"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.6"></a><h3>6.
Client Registration with Pushed Metadata</h3>
<p>
This registration flow works as follows:
</p>
<p>
</p>
<ol class="text">
<li>
The client sends its metadata in JSON form to the client registration endpoint. The
client MUST send its name, description, and redirection URI and MAY send a URI
for its icon. The client MAY sign the metadata as a JSON Token issuer, using the
mechanisms defined in <a class='info' href='#OAuth-Sig'>[OAuth‑Sig]<span> (</span><span class='info'>Balfanz, D., “OAuth Signature proposals,” 2010.</span><span>)</span></a>.
</li>
<li>
The authorization server checks the data, verifying the signature as necessary, and
returns a client identifier and an optional client secret.
</li>
</ol><p>
</p><br /><hr class="insert" />
<a name="Figure-1"></a>
<div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
+--------+ +---------------+
| Client |--(A)--- Registration Request --->| Authorization |
| | with Metadata | Server |
| | | |
| |<-(B)----Registration Response ---| |
| | with Client ID Info | |
+--------+ +---------------+
</pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b> Figure 1: Client Registration Flow with Pushed Metadata </b></font><br /></td></tr></table><hr class="insert" />
<a name="anchor15"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.6.1"></a><h3>6.1.
Client Registration Request</h3>
<p>
The client sends a JSON formatted document to the client registration endpoint.
The client includes the following parameters in the request:
</p>
<p>
</p>
<blockquote class="text"><dl>
<dt>type</dt>
<dd>
REQUIRED. This parameter must be set to "push".
</dd>
<dt>client_name</dt>
<dd>
REQUIRED. This field contains a human-readable name of the client.
</dd>
<dt>client_url</dt>
<dd>
REQUIRED. This field contains the URL of the homepage of the client.
</dd>
<dt>client_description</dt>
<dd>
REQUIRED. This field contains a text description of the client.
</dd>
<dt>client_icon</dt>
<dd>
OPTIONAL. This field contains a URL for an icon for the client.
</dd>
<dt>redirect_url</dt>
<dd>
REQUIRED. This field contains the URL to which the authorization server should send its response.
</dd>
</dl></blockquote><p>
</p>
<p>
The client MAY include additional metadata in the request and the
authorization server MAY ignore this additional information.
</p>
<p>
For example, the client might send the following request:
</p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
POST /register HTTP/1.1
Host: server.example.com
Content-Type: application/json
{
type: "push",
client_name: "Online Photo Gallery",
client_url: "http://onlinephotogallery.com",
client_description: "Uploading and also editing capabilities!",
client_icon: "http://onlinephotogallery.com/icon.png",
redirect_url: "https://onlinephotogallery.com/client_reg"
}
</pre></div>
<p>
The parameters are included in the entity body of the HTTP request using the
"application/json" media type as defined by <a class='info' href='#JSON'>[JSON]<span> (</span><span class='info'>Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” 2006.</span><span>)</span></a>. The parameters are
serialized into a JSON structure by adding each parameter at the highest
structure level. Parameter names and string values are included as JSON strings.
</p>
<a name="anchor16"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.6.2"></a><h3>6.2.
Client Registration Response</h3>
<p>
After receiving and verifying information received from the client, the
authorization server issues a client identifier and an optional client secret,
and constructs the response by adding the following parameters to the entity
body of the HTTP response with a 200 status code (OK):
</p>
<blockquote class="text"><dl>
<dt>client_id</dt>
<dd>
REQUIRED.
</dd>
<dt>client_secret</dt>
<dd>
OPTIONAL.
</dd>
<dt>issued_at</dt>
<dd>
OPTIONAL. Specifies the timestamp when the identifier was issued.
The timestamp value MUST be a positive integer. The value is expressed
in the number of seconds since January 1, 1970 00:00:00 GMT.
</dd>
<dt>expires_in</dt>
<dd>
OPTIONAL; if supplied, the <tt>issued_at</tt> parameter
is REQUIRED. Specifies the valid
lifetime, in seconds, of the identifier. The value is represented in base 10 ASCII.
</dd>
</dl></blockquote><p>
</p>
<p>
The parameters are included in the entity body of the HTTP response using the
"application/json" media type as defined by <a class='info' href='#JSON'>[JSON]<span> (</span><span class='info'>Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” 2006.</span><span>)</span></a>. The parameters are
serialized into a JSON structure by adding each parameter at the highest
structure level. Parameter names and string values are included as JSON strings.
</p>
<p>
The authorization server MUST include the HTTP <tt>Cache-Control</tt> response header field with a value of
<tt>no-store</tt> in any response containing
<tt>client_secret</tt>.
</p>
<p>
For example, the authorization server might return the following response:
</p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
client_id: "5UO9XcL4TQTa",
client_secret: "WdRKN3zeTc20"
}
</pre></div>
<a name="anchor17"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.6.3"></a><h3>6.3.
Error Response</h3>
<p>
If the request for registration is invalid or unauthorized, the authorization
server constructs the response by adding the following parameters to the
entity body of the HTTP response with a 400 status code (Bad Request) using
the “application/json” media type:
</p>
<ul class="text">
<li>
<tt>error</tt> (REQUIRED).
</li>
<li>
<tt>error_description</tt> (OPTIONAL). Human-readable text providing
additional information, used to assist in the understanding and
resolution of the error occurred.
</li>
<li>
<tt>error_uri</tt> (OPTIONAL). A URI identifying a human-readable web page
with information about the error, used to provide the end-user
with additional information about the error.
</li>
</ul><p>
</p>
<p>
An example error response (with line breaks for readability):
</p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error": "unauthorized_client",
"description": "This client is not on the
white list of this Authorization Server."
}
</pre></div>
<a name="anchor18"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.7"></a><h3>7.
Client Registration with Pushed URL and Pulled Metadata</h3>
<p>
This registration flow works as follows:
</p>
<p>
</p>
<ol class="text">
<li>
The client sends its metadata URI to the client registration endpoint. The client MAY sign the
metadata as a JSON Token issuer, using the mechanisms defined in <a class='info' href='#OAuth-Sig'>[OAuth‑Sig]<span> (</span><span class='info'>Balfanz, D., “OAuth Signature proposals,” 2010.</span><span>)</span></a>.
</li>
<li>
The authorization server verifies the signature as necessary, and uses the
<a class='info' href='#RFC5785'>[RFC5785]<span> (</span><span class='info'>Nottingham, M. and E. Hammer-Lahav, “Defining Well-Known Uniform Resource Identifiers (URIs),” April 2010.</span><span>)</span></a> and <a class='info' href='#hostmeta'>[hostmeta]<span> (</span><span class='info'>Hammer-Lahav, E., “Web Host Metadata,” 2010.</span><span>)</span></a> discovery
mechanisms on this URI to retrieve the host-meta document
describing the client. The host-meta document MUST contain the client
name, description, and redirection URI, and MAY contain a URI for the client
icon.
</li>
</ol><p>
</p><br /><hr class="insert" />
<a name="Figure-2"></a>
<div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
+--------+ +---------------+
| Client |--(A)--- Registration Request --->| Authorization |
| | with URL | Server |
| | | |
| |<-(B)--- Client Discovery --------| |
| | | |
| |--(C)---- Host-Meta Document ---->| |
| | | |
| |<-(D)--- Registration Response ---| |
| | with Client ID Info | |
+--------+ +---------------+
</pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b> Figure 2: Client Registration Flow with Pushed URL and Pulled Metadata </b></font><br /></td></tr></table><hr class="insert" />
<a name="anchor19"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.7.1"></a><h3>7.1.
Client Registration Request</h3>
<p>
The client sends a JSON formatted document to the client registration endpoint.
The client includes the following parameters in the request:
</p>
<p>
</p>
<blockquote class="text"><dl>
<dt>type</dt>
<dd>
REQUIRED. This parameter must be set to "pull".
</dd>
<dt>client_url</dt>
<dd>
REQUIRED. This field contains the URL of the homepage of the client.
</dd>
</dl></blockquote><p>
</p>
<p>
The client MUST NOT include other metadata parameters, such as those defined in the pushed-metadata scenario.
</p>
<p>
For example, the client might send the following request:
</p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
POST /register HTTP/1.1
Host: server.example.com
Content-Type: application/json
{
type: "pull",
url: "http://onlinephotogallery.com"
}
</pre></div>
<p>
The parameters are included in the entity body of the HTTP request using the
"application/json" media type as defined by <a class='info' href='#JSON'>[JSON]<span> (</span><span class='info'>Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” 2006.</span><span>)</span></a>. The parameters are
serialized into a JSON structure by adding each parameter at the highest
structure level. Parameter names and string values are included as JSON strings.
</p>
<a name="anchor20"></a><br /><hr />
<table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc"> TOC </a></td></tr></table>
<a name="rfc.section.7.2"></a><h3>7.2.
Client Discovery</h3>
<p>
The authorization server evaluates this request and MAY perform a <a class='info' href='#RFC5785'>[RFC5785]<span> (</span><span class='info'>Nottingham, M. and E. Hammer-Lahav, “Defining Well-Known Uniform Resource Identifiers (URIs),” April 2010.</span><span>)</span></a> and <a class='info' href='#hostmeta'>[hostmeta]<span> (</span><span class='info'>Hammer-Lahav, E., “Web Host Metadata,” 2010.</span><span>)</span></a> discovery
mechanism on the provided URL to the host-meta document for the client.
</p>
<p>
For example:
</p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
GET /.well-known/host-meta HTTP/1.1
Host: onlinephotogallery.com
</pre></div>
<p>
The authorization server retrieves the host-meta document, which MUST contain:
</p>
<p>
</p>
<ul class="text">
<li>
A
<tt>Property</tt>
element with a
<tt>type</tt>
value of