| OAuth Working Group | J. Richer, Ed. |
| Internet-Draft | The MITRE Corporation |
| Intended status: Standards Track | J. Bradley |
| Expires: August 19, 2013 | Ping Identity |
| M. Jones | |
| Microsoft | |
| M. Machulak | |
| Newcastle University | |
| February 15, 2013 |
OAuth Dynamic Client Registration Protocol
draft-ietf-oauth-dyn-reg-06
This specification defines an endpoint and protocol for dynamic registration of OAuth Clients at an Authorization Server.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 19, 2013.
Copyright (c) 2013 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 requiring the two parties to interact before hand. Nevertheless, in order for the authorization server to accurately and securely 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 metadata, such as a display name and icon to be presented to the user during the authorization step. This draft also provides a mechanism for the Client to read and update this information after the initial registration action.
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 [RFC6749].
This specification defines the following additional terms:
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, such as the list of valid redirect URIs.
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.
[[ Editor's note: normative language in the table below is meant to apply to the *client* when sending the request. The paragraph above is meant to say that the server must at least accept all parameters and not fail with an error at an unknown parameter, especially if it's in the list below. Also, extensions need to explicitly call out if they're not going to do something with one of these basic parameters instead of just ignoring their existence. This is meant to be the *minimum set* of parameters for interoperability. ]]
Other authentication methods may be defined by extension. If unspecified or omitted, the default is
client_secret_basic, denoting HTTP Basic Authentication Scheme as specified in Section 2.3.1 of OAuth 2.0.Authorization Servers MAY allow for other values as defined in grant type extensions to OAuth2. The extension process is described in OAuth2 Section 2.5, and the value of this parameter MUST be the same as the value of the
grant_type parameter defined in the extension.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/json format. The Client Registration Endpoint MUST be protected by a transport-layer security mechanism, and 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 Client Registration Endpoint MAY accept an initial authorization credential in the form of an OAuth 2.0 [RFC6749] 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.
In order to support open registration and facilitate wider interoperability, the Client Registration Endpoint SHOULD allow initial registration requests with no authentication. These requests MAY be rate-limited or otherwise limited to prevent a denial-of-service attack on the Client Registration Endpoint.
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 to the Client Registration Access Endpoint [AccessEndpoint]. As such, the Client Registration Access Endpoint MUST accept requests with OAuth 2.0 Bearer Tokens [RFC6750] for these operations, whether or not the initial registration call requires authentication of some form.
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 any parameters described in Client Metadata [client-metadata] that the client wishes to specify for itself during the registration. The Authorization Server MAY provision default values for any items omitted in the Client Metadata.
The Client sends an HTTP POST to the Client Registration Endpoint with a content type of "application/json". The HTTP Entity Payload is a JSON [RFC4627] document consisting of a JSON object and all parameters as top- level members of that JSON object.
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
Content-Type: application/json
Accept: application/json
Host: server.example.com
{
"redirect_uris":["https://client.example.org/callback",
"https://client.example.org/callback2"]
"client_name":"My Example Client",
"token_endpoint_auth_method":"client_secret_basic",
"scope":"read write dolphin",
"logo_url":"https://client.example.org/logo.png",
"jwk_url":"https://client.example.org/my_rsa_public_key.jwk"
}
Upon successful registration, the Authorization Server generates a new Client Identifier for the client. This Client Identifier MUST be unique at the server and MUST NOT be in use by any other client. The server responds with an HTTP 201 Created code and a body of type application/json with content described in Client Information Response [client-info-response].
Upon an unsuccessful registration, the Authorization Server responds with an error as described in Client Registration Error [client-registration-error].
The Client Registration Access Endpoint is an OAuth 2.0 protected endpoint that is provisioned by the server for a specific client to be able to view and update its registered information. The Client MUST include its Registration Access Token in all calls to this endpoint as an OAuth 2.0 Bearer Token [RFC6750].
Operations on this endpoint are switched through the use of different HTTP methods [RFC2616].
The Authorization Server MUST provide the client with the fully qualified URL in the registration_access_url element of the Client Information Response [client-info-response]. The Authorization Server MUST NOT expect the client to construct or discover this URL on its own. The Client MUST use the URL as given by the server and MUST NOT construct this URL from component pieces.
Depending on deployment characteristics, the Client Registration Access Endpoint URL may take any number of forms. It is RECOMMENDED that this endpoint URL be formed through the use of a server-constructed URL string which combines the Client Registration Endpoint's URL and the issued client_id for this Client, with the latter as either a path parameter (https://server.example.com/register/client_id) or a query parameter (https://server.example.com/register/?update=client_id). These common patterns can help the Server to more easily determine the client to which the request pertains, which MUST be matched against the client to which the Registration Access Token was issued. If desired, the server MAY simply return the Client Registration Endpoint URL as the Client Registration Access Endpoint URL and change behavior based on the authentication context provided by the Registration Access Token.
In order to read the current configuration of the Client on the Authorization Server, the Client makes an HTTP GET request to the Client Registration Access Endpoint, authenticating with its Registration Access Token.
Following is a non-normative example request (with line wraps for display purposes only):
GET /register/s6BhdRkqt3 HTTP/1.1 Accept: application/json Host: server.example.com Authorization: Bearer reg-23410913-abewfq.123483
Upon successful read of the information for a currently active Client, the Authorization Server responds with an HTTP 200 OK with content type of application/json and a payload as described in Client Information Response [client-info-response].
If the client does not exist on this server, the server MUST return an HTTP 404 Not Found. [[ Editor's note: If the client doesn't exist, then the Refresh Access Token shouldn't be valid, making this kind of error a 403 at the auth layer instead. How best to call this inconsistency out? ]]
This operation updates a previously-registered client with new metadata at the Authorization Server. This request is authenticated by the Registration Access Token issued to the client.
The Client sends an HTTP PUT to the Client Registration Access Endpoint with a content type of "application/json". The HTTP Entity Payload is a JSON [RFC4627] document consisting of a JSON object and all parameters as top- level members of that JSON object.
This request MUST include all fields described in Client Metadata [client-metadata] as returned to the Client from a previous register, read, or update operation. The Client MUST NOT include the registration_access_token, registration_access_url, expires_at, or issued_at fields described in Client Information Response [client-info-response].
Valid values of Client Metadata fields in this request MUST replace, not augment, the values previously associated with this Client. Omitted fields MUST be treated as null or empty values by the server.
The Client MUST include its client_id field in the request, and it MUST be the same as its currently-issued Client Identifier. If the client includes its client_secret in the request, then it MUST match the currently-issued client_secret for that Client. The client MUST NOT be allowed to overwrite its existing client_secret with its own value.
For all metadata fields, the Authorization Server MAY replace any invalid values with suitable default values, and it MUST return any such fields to the Client in the response.
For example, a client could send the following request to the Client Registration Endpoint to update the client registration in the above example:
Following is a non-normative example request (with line wraps for display purposes only):
PUT /register/s6BhdRkqt3 HTTP/1.1
Accept: application/json
Host: server.example.com
Authorization: Bearer reg-23410913-abewfq.123483
{
"client_id":"s6BhdRkqt3",
"client_secret": "cf136dc3c1fc93f31185e5885805d",
"redirect_uri":["https://client.example.org/callback",
"https://client.example.org/alt"],
"scope": "read write dolphin",
"grant_type": ["authorization_code", "refresh_token"]
"token_endpoint_auth_method": "client_secret_basic",
"jwk_url": "https://client.example.org/my_rsa_public_key.jwk"
"client_name":"My New Example",
"logo_url":"https://client.example.org/newlogo.png"
}
Upon successful update, the Authorization Server responds with an HTTP 200 OK Message with content type applicaiton/json and a payload as described in Client Information Response [client-info-response]. The Authorization Server MAY include a new Client Secret and/or Registration Access Token in its response. If so, the Client MUST immediately discard its previous Client Secret and/or Registration Access Token.
If the Client does not exist on this server, the server MUST return an HTTP 404 Not Found. [[ Editor's note: If the client doesn't exist, then the Refresh Access Token shouldn't be valid, making this kind of error a 403 at the auth layer instead. How best to call this inconsistency out? ]]
If the Client is not allowed to update its records, the server MUST respond with HTTP 403 Forbidden.
If the Client attempts to set an invalid metadata field and the Authorization Server does not set a default value, the Authorization Server responds with an error as described in Client Registration Error Response [client-registration-error].
[[ Editor's note: The utility and nature of this function are still under active discussion. This is a proposed set of functionality that a server MAY choose to implement, else give a 405 response to any client that tries, if it can't support it. ]]
In order to deprovision itself on the Authorization Server, the Client makes an HTTP DELETE request to the Client Registration Access Endpoint. This request is authenticated by the Registration Access Token issued to the client.
Following is a non-normative example request (with line wraps for display purposes only):
DELETE /register/s6BhdRkqt3 HTTP/1.1 Accept: application/json Host: server.example.com Authorization: Bearer reg-23410913-abewfq.123483
A successful delete action will invalidate the client_id, client_secret, and registration_access_token for this client, thereby preventing the client_id from being used at either the Authorization Endpoint or Token Endpoint of the Authorization Server. The Authorization Server SHOULD immediately invalidate all existing authorization grants and currently-active tokens associated with this Client.
If a Client has been successfully deprovisioned, the Authorization Server responds with an HTTP 204 No Content message.
If there is no such client, the server responds with an HTTP 404 Not Found. [[ Editor's note: This is an inconsistent state and shouldn't happen. See discussion about the Registration Access Token validity above. ]]
If the client is not allowed to delete itself, the server responds with HTTP 403 Forbidden.
If the server does not support the delete method, it responds with an HTTP 405 Not Supported.
Following is a non-normative example response:
HTTP/1.1 204 No Content Cache-Control: no-store
In response to certain requests from the Client to either the Client Registration Endpoint or the Client Registration Access Endpoint as described in this specification, the Authorization Server sends the following response bodies.
The response contains the following fields:
, as well as a Client Secret if this client is a confidential client. The response also contains the fully qualified URL to the Client Registration Access Endpoint for this specific client that the client may use to obtain and update information about itself. The response also contains a Registration Access Token that is to be used by the client to perform subsequent operations at the Client Registration Access Endpoint.
Additionally, the Authorization Server MUST return all registered metadata [client-metadata] about this client, including any fields provisioned by the Authorization Server itself. The Authorization Server MAY reject or replace any of the client's requested metadata values submitted during the registration or update requests and substitute them with suitable values.
The response is an application/json document with all parameters as top-level members of a JSON object [RFC4627] .
Following is a non-normative example response:
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"registration_access_token": "reg-23410913-abewfq.123483",
"registration_access_url":
"https://server.example.com/register/s6BhdRkqt3",
"client_id":"s6BhdRkqt3",
"client_secret": "cf136dc3c1fc93f31185e5885805d",
"expires_at":2893276800
"redirect_uris":["https://client.example.org/callback",
"https://client.example.org/callback2"]
"scope": "read write dolphin",
"grant_type": ["authorization_code", "refresh_token"]
"token_endpoint_auth_method": "client_secret_basic",
"logo_url": "https://client.example.org/logo.png",
"jwk_url": "https://client.example.org/my_rsa_public_key.jwk"
}
When an OAuth error condition occurs, such as the client presenting an invalid Registration Access Token, the Authorization Server returns an Error Response as defined in Section 5.2 of the OAuth 2.0 specification.
When a registration error condition occurs, the Authorization Server returns an HTTP 400 status code with content type application/json consisting of a JSON object [RFC4627] 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 (with line wraps for display purposes only):
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error":"invalid_redirect_uri",
"error_description":"The redirect URI of http://sketchy.example.com
is not allowed for this server."
}
This document makes no requests of IANA.
[[ Editor's note: Following are some security considerations taken from the UMA and OpenID Connect source drafts. These need to be massaged into a properly generic set of considerations. ]]
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].
As this endpoint is an OAuth2 Protected Resource, requests to the Registration Endpoint SHOULD have some rate limiting on failures to prevent the Registration Access Token from being disclosed though repeated access attempts.
The authorization server MUST treat all client metadata as self-asserted. A rogue Client might use the name and logo for the legitimate Client, which it is trying to impersonate. An Authorization Server needs to take steps to mitigate this phishing risk, since the logo could confuse users into thinking they're logging in to the legitimate Client. For instance, an Authorization Server could warn if the domain/site of the logo doesn't match the domain/site of redirect URIs. An Authorization Server can also present warning messages to end users about untrusted Clients in all cases, especially if such clients have been dynamically registered and have not been trusted by any users at the Authorization Server before.
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.
While the Client Secret can expire, the Registration Access Token should not expire while a client is still actively registered. If this token were to expire, a Client could be left in a situation where it has no means of updating itself and must register itself anew. As the Registration Access Tokens are long-term credentials, and since the Registration Access Token is a Bearer token and acts as the sole authentication for use at the Client Registration Access Endpoint, it MUST be protected by the Client as described in OAuth 2.0 Bearer [RFC6750].
If a Client is deprovisioned from a server, any outstanding Registration Access Tokens for that client MUST be invalidated at the same time. Otherwise, this can lead to an inconsistent state wherein a Client could make requests to the Client Registration Access Endpoint where the authentication would succeed but the action would fail because the Client is no longer valid.
The authors thank the OAuth Working Group, the User-Managed Access Working Group, and the OpenID Connect Working Group participants for their input to this document. In particular, the following individuals have been instrumental in their review and contribution to various versions of this document: Amanda Anganes, Tim Bray, Domenico Catalano, George Fletcher, Torsten Lodderstedt, Eve Maler, Thomas Hardjono, Nat Sakimura, and Christian Scholz.
[[ to be removed by the RFC editor before publication as an RFC ]]
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