| Network Working Group | J. Richer, Ed. |
| Internet-Draft | The MITRE Corporation |
| Intended status: Standards Track | T. Hardjono |
| Expires: May 09, 2013 | MIT |
| M. Machulak | |
| Newcastle University | |
| E. Maler | |
| XMLgrrl.com | |
| C. Scholz | |
| COM.lounge GmbH | |
| N. Sakimura | |
| NRI | |
| J. Bradley | |
| Ping Identity | |
| M.B. Jones | |
| Microsoft | |
| November 05, 2012 |
OAuth Dynamic Client Registration Protocol
draft-ietf-oauth-dyn-reg-01
This specification proposes an OAuth Dynamic Client Registration protocol.
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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http:/⁠/⁠datatracker.ietf.org/⁠drafts/⁠current/⁠.
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This Internet-Draft will expire on May 09, 2013.
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.
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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. The OAuth2 authorization framework does not define how the relationship between the Client and the Authorization Server is initialized, or how a given client is assigned a unique Client Identifier. Historically, this has happened out-of-band from the OAuth protocol. This draft provides a mechanism for a client to register itself with the Authorization Server, which can be used to dynamically provision a Client Identifier, and optionally a Client Secret.
As part of the registration process, this specification also defines a mechanism for the client to present the Authorization Server with a set of meta information, such as a display name and icon to be presented to the user during the authorization step. This draft provides a method for the client to register and update this information over time.
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 [RFC2119].
Unless otherwise noted, all the protocol parameter names and values are case sensitive.
This specification uses the terms "Access Token", "Refresh Token", "Authorization Code", "Authorization Grant", "Authorization Server", "Authorization Endpoint", "Client", "Client Identifier", "Client Secret", "Protected Resource", "Resource Owner", "Resource Server", and "Token Endpoint" defined by OAuth 2.0 [OAuth2.0].
This specification defines the following additional terms:
[[ Following are proposed requirements for dynamic client registration. This section is intended for discussion and will likely be removed in the final draft. ]]
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.
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.
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.
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. The registration protocol should be simple and flexible enough to allow for multiple types of applications.
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.
The Client Registration Endpoint is an OAuth 2.0 Endpoint defined in this document that is designed to allow a Client to register itself with the Authorization Server. The Client Registration Endpoint MUST accept HTTP POST messages with request parameters encoded in the entity body using the application/x-www-form-urlencoded format. The Client Registration Endpoint MUST be protected by a transport-layer security mechanism when sending requests to the Registration Endpoint. The server MUST support TLS 1.2 RFC 5246 [RFC5246] and/or TLS 1.0 [RFC2246] and MAY support additional transport-layer mechanisms meeting its security requirements. When using TLS, the Client MUST perform a TLS/SSL server certificate check, per RFC 6125 [RFC6125].
The Endpoint defines three operations that a client can take on it, switched by the "operation" parameter:
In order to facilitate registered clients updating their information, the Client Registration Endpoint issues a request_access_token for clients to securely identify themselves in future connections. As such, the Endpoint MUST accept requests with OAuth 2.0 Bearer Tokens [OAuth.Bearer] for these operations.
In order to support open registration and facilitate wider interoperability, the Client Registration Endpoint SHOULD allow client_associate requests with no further authentication. These requests MAY be rate-limited to prevent a denial-of-service attack on the Client Registration Endpoint.
In addition, the Client Registration Endpoint MAY accept an initial authorization credential in the form of an OAuth 2.0 [OAuth2.0] access token in order to limit registration to only previously authorized parties. The method by which this access token is obtained by the registrant is generally out-of-band and is out of scope of this specification.
These two aspects, operation selection and client authentication, are represented by two parameters common to all operations:
Each operation takes a different parameter set, and all operations are described below.
The Client Registration Endpoint MUST ignore all parameters it does not understand.
This operation registers a new client to the Authorization Server. The Authorization Server assigns this client a unique Client Identifier, optionally assigns a Client Secret, and associates the metadata given in the request with the issued Client Identifier. The request includes the two parameters described above as well as any parameters described in Client Metadata [client-metadata].
For example, a client could send the following registration request to the Client Registration Endpoint:
Following is a non-normative example request (with line wraps for display purposes only):
POST /register HTTP/1.1
Accept: application/x-www-form-urlencoded
Host: server.example.com
Authorization: Bearer eyJhbGciOiJSUzI1NiJ9.eyJ ... fQ.8Gj_-sj ... _X
operation=client_associate
&redirect_uris=https://client.example.org/callback
%20https://client.example.org/callback2
&client_name=My%20Example%20
&logo_url=https://client.example.org/logo.png
&token_endpoint_auth_type=client_secret_basic
&jwk_url=https://client.example.org/my_rsa_public_key.jwk
Upon successful association, the Client Registration Endpoint returns the newly-created Client Identifier and, optionally, a Client Secret. The response also contains a Registration Access Token that is to be used by the client to perform subsequent operations at this endpoint. These items are returned as a JSON document with the following fields as top-level members of the root JSON object.
Following is a non-normative example response:
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"client_id":"s6BhdRkqt3",
"client_secret":
"cf136dc3c1fd9153029bb9c6cc9ecead918bad9887fce6c93f31185e5885805d",
"registration_access_token": "this.is.a.access.token.value.ffx83",
"expires_at":2893276800
}
This operation updates a previously-registered client with new metadata at the Authorization Server. This request MUST be protected by the Registration Authorization Token associated with the Client Identifier. This request MAY include any fields described in Client Metadata [client-metadata]. The values of Client Metadata fields in this request MUST replace (not augment) the values previously associated with this client_identifier. Empty values in Client Metadata SHOULD be taken as a request to clear any existing value of that field.
For example, a client could send the following registration request to the Client Registration Endpoint:
Following is a non-normative example request (with line wraps for display purposes only):
POST /register HTTP/1.1
Accept: application/x-www-form-urlencoded
Host: server.example.com
Authorization: Bearer eyJhbGciOiJSUzI1NiJ9.eyJ ... fQ.8Gj_-sj ... _X
operation=client_update
&redirect_uris=https://client.example.org/callback
%20https://client.example.org/callback2
&client_name=My%20Example%20
&logo_url=https://client.example.org/logo.png
&token_endpoint_auth_type=client_secret_basic
&jwk_url=https://client.example.org/my_rsa_public_key.jwk
Upon successful update, the Client Registration Endpoint returns a JSON document with the following fields as top-level members of the root JSON object.
Following is a non-normative example response:
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"client_id":"s6BhdRkqt3",
}
[[ Editor's note: should this return the entire client data object, for confirmation and review, including any fields that may have been asserted by the AS? ]]
This operation allows the client to rotate its current Client Secret, if it has one. If the client has not been issued a Client Secret, this operation is an error. [[ Editor's note: could this request be used to rotate the Registration Access Token, even when there's not a client_secret? Should something else be used to rotate the token independently? This is an open issue. ]]
Following is a non-normative example request (with line wraps for display purposes only):
POST /register HTTP/1.1 Accept: application/x-www-form-urlencoded Host: server.example.com Authorization: Bearer eyJhbGciOiJSUzI1NiJ9.eyJ ... fQ.8Gj_-sj ... _X operation=rotate_secret
Upon successful rotation of the client secret, the Client Registration Endpoint returns a JSON document with the following fields as top-level members of the root JSON object.
Following is a non-normative example response:
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"client_id":"s6BhdRkqt3",
"client_secret":
"cf136dc3c1fd9153029bb9c6cc9ecead918bad9887fce6c93f31185e5885805d",
"registration_access_token": "this.is.a.access.token.value.ffx83",
"expires_at":2893276800
}
When an OAuth error condition occurs, the Client Registration Endpoint returns an Error Response as defined in Section 5.2 of the OAuth 2.0 specification.
When a registration error condition occurs, the Client Registration Endpoint returns a HTTP 400 status code including a JSON object describing the error in the response body.
The JSON object contains two members:
This specification defines the following error codes:
Following is a non-normative example of an error response:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error":"invalid_operation",
"error_description":"The value of the operation parameter must be one of client_associate, rotate_secret or client_update."
}
Clients generally have an array of metadata associated with their unique Client Identifier at the Authorization Server. These can range from human-facing display strings, such as a client name, to items that impact the security of the protocol,
Extensions and profiles of this specification MAY expand this list, but MUST at least accept all parameters on this list. The Authorization Server MUST ignore any additional parameters sent by the Client that it does not understand.
This document makes no requests of IANA.
[[ Editor's note: Following are some security considerations taken whole from the UMA and OpenID Connect source drafts. ]]
Since requests to the Client Registration Endpoint result in the transmission of clear-text credentials (in the HTTP request and response), the server MUST require the use of a transport-layer security mechanism when sending requests to the Registration Endpoint. The server MUST support TLS 1.2 RFC 5246 [RFC5246] and/or TLS 1.0 [RFC2246] and MAY support additional transport-layer mechanisms meeting its security requirements. When using TLS, the Client MUST perform a TLS/SSL server certificate check, per RFC 6125 [RFC6125].
Requests to the Registration Endpoint for client_update MUST have some rate limiting on failures to prevent the Client secret from being disclosed though repeated access attempts.
A rogue RP might use the logo for the legitimate RP, which it is trying to impersonate. An IdP needs to take steps to mitigate this phishing risk, since the logo could confuse users into thinking they're logging in to the legitimate RP. An IdP could also warn if the domain/site of the logo doesn't match the domain/site of redirect URIs. An IdP can also make warnings against untrusted RPs in all cases, especially if they're dynamically registered, have not been trusted by any users at the IdP before, and want to use the logo feature.
In a situation where the Authorization Server is supporting open Client registration, it must be extremely careful with any URL provided by the Client that will be displayed to the user (e.g. logo_url and policy_url). A rogue Client could specify a registration request with a reference to a drive-by download in the policy_url. The Authorization Server should check to see if the logo_url and policy_url have the same host as the hosts defined in the array of redirect_uris.
The authors thank the User-Managed Access Work Group and the OpenID Connect Working Group participants for their input to this document.
[[ to be removed by RFC editor before publication as an RFC ]]
- 01
- 00
| [UMA-Core] | Scholz, C., "UMA Requirements", 2010. |
| [UMA-UC] | Akram, H., "UMA Explained", 2010. |
| [UMA-Reqs] | Maler, E., "UMA Requirements", 2010. |