| OAuth Working Group | J. Richer, Ed. |
| Internet-Draft | The MITRE Corporation |
| Intended status: Standards Track | J. Bradley |
| Expires: February 27, 2014 | Ping Identity |
| M. Jones | |
| Microsoft | |
| M. Machulak | |
| Newcastle University | |
| August 26, 2013 |
OAuth 2.0 Dynamic Client Registration Management Protocol
draft-richer-oauth-dyn-reg-management-00
This specification defines methods for a dynamically registered OAuth 2.0 client to manage its registration through an OAuth 2.0 protected web API as well as extended client metadata attributes.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
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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 2.0 clients to obtain authorization from an OAuth 2.0 authorization server without requiring the two parties to interact beforehand. Nevertheless, 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 OAuth 2.0 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 2.0 protocol.
This specification extends the OAuth 2.0 Core Dynamic Client Registration [DynReg] specification (which provides a method for OAuth 2.0 clients to be registered dynamically with an authorization server) and defines a mechanism for the client to present the authorization server with a set of extended 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. This draft protects these actions through the use of an OAuth 2.0 bearer access token that is issued to the client during registration explicitly for this purpose.
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:
This extends the flow in the core dynamic registration [DynReg] specification as follows:
+--------(A)- Initial Access Token
|
v
+-----------+ +---------------+
| |--(B)- Client Registration Request -->| Client |
| | | Registration |
| |<-(C)- Client Information Response ---| Endpoint |
| | +---------------+
| |
| | +---------------+
| Client or |--(D)- Read or Update Request ------->| |
| Developer | | |
| |<-(E)- Client Information Response ---| Client |
| | | Configuration |
| | | Endpoint |
| | | |
| |--(F)- Delete Request --------------->| |
| | | |
| |<-(G)- Delete Confirmation -----------| |
+-----------+ +---------------+
Figure 1: Abstract Protocol Flow
The abstract OAuth 2.0 Client dynamic registration flow illustrated in Figure 1 describes the interaction between the client or developer and the two endpoints defined in this specification and its parent. This figure does not demonstrate error conditions. This flow includes the following steps:
Throughout the course of the dynamic registration protocol, there are three different classes of credentials in play, each with different properties and targets.
The Authorization Server MAY rotate the client's registration access token and/or client credentials (such as a client_secret) throughout the lifetime of the client. The client can discovery that these values have changed by reading the client information response returned from either a read or update request to the client configuration endpoint. The client's current registration access token and client credentials (if applicable) MUST be included in this response.
The registration access token SHOULD be rotated only in response to a read or update request to the client configuration endpoint, at which point the new registration access token is returned to the client and the old registration access token SHOULD be discarded by both parties. If the registration access token to expire or be rotated outside of such requests, the client or developer may be locked out of managing the client's configuration.
Many OAuth 2.0 clients wish to register different kinds of client metadata to facilitate authorization and usage of the protected API. This specification extends the list of client metadata defined in OAuth 2.0 Core Client Dynamic Registration [DynReg] with the following fields:
Human-readable client metadata values and client metadata values that reference human-readable values MAY be represented in multiple languages and scripts. For example, the values of fields such as client_name, tos_uri, policy_uri, logo_uri, and client_uri might have multiple locale-specific values in some client registrations.
To specify the languages and scripts, BCP47 [RFC5646] language tags are added to client metadata member names, delimited by a # character. Since JSON member names are case sensitive, it is RECOMMENDED that language tag values used in Claim Names be spelled using the character case with which they are registered in the IANA Language Subtag Registry [IANA.Language]. In particular, normally language names are spelled with lowercase characters, region names are spelled with uppercase characters, and languages are spelled with mixed case characters. However, since BCP47 language tag values are case insensitive, implementations SHOULD interpret the language tag values supplied in a case insensitive manner. Per the recommendations in BCP47, language tag values used in metadata member names should only be as specific as necessary. For instance, using fr might be sufficient in many contexts, rather than fr-CA or fr-FR.
For example, a client could represent its name in English as "client_name#en": "My Client" and its name in Japanese as "client_name#ja-Jpan-JP": "\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D" within the same registration request. The authorization server MAY display any or all of these names to the resource owner during the authorization step, choosing which name to display based on system configuration, user preferences or other factors.
If any human-readable field is sent without a language tag, parties using it MUST NOT make any assumptions about the language, character set, or script of the string value, and the string value MUST be used as-is wherever it is presented in a user interface. To facilitate interoperability, it is RECOMMENDED that clients and servers use a human-readable field without any language tags in addition to any language-specific fields, and it is RECOMMENDED that any human-readable fields sent without language tags contain values suitable for display on a wide variety of systems.
Implementer's Note: Many JSON libraries make it possible to reference members of a JSON object as members of an object construct in the native programming environment of the library. However, while the # character is a valid character inside of a JSON object's member names, it is not a valid character for use in an object member name in many programming environments. Therefore, implementations will need to use alternative access forms for these claims. For instance, in JavaScript, if one parses the JSON as follows, var j = JSON.parse(json);, then the member client_name#en-us can be accessed using the JavaScript syntax j["client_name#en-us"].
The client configuration endpoint is an OAuth 2.0 protected resource that is provisioned by the server to facilitate viewing, updating, and deleting a client's registered information. The location of this endpoint is communicated to the client through the registration_client_uri member of the Client Information Response [client-info-response]. The client MUST use 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]. If an authorization server does not support a particular method on the client configuration endpoint, it MUST respond with the appropriate error code.
The authorization server MUST provide the client with the fully qualified URL in the registration_client_uri 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 configuration 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 or a query parameter. For example, a client with the client identifier s6BhdRkqt3 could be given a client configuration endpoint URL of https://server.example.com/register/s6BhdRkqt3 (path parameter) or of https://server.example.com/register?client_id=s6BhdRkqt3 (query parameter). In both of these cases, the client simply uses the URL as given by the authorization server.
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 configuration endpoint URL and change behavior based on the authentication context provided by the registration access token.
To read the current configuration of the client on the authorization server, the client makes an HTTP GET request to the client configuration 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]. Some values in the response, including the client_secret and registration_access_token, MAY be different from those in the initial registration response. If the authorization server includes a new client secret and/or registration access token in its response, the client MUST immediately discard its previous client secret and/or registration access token. The value of the client_id MUST NOT change from the initial registration response.
If the registration access token used to make this request is not valid, the server MUST respond with an error as described in OAuth Bearer Token Usage [RFC6750].
If the client does not exist on this server, the server MUST respond with HTTP 401 Unauthorized and the registration access token used to make this request SHOULD be immediately revoked.
If the client does not have permission to read its record, the server MUST return an HTTP 403 Forbidden.
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 configuration 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_client_uri, client_secret_expires_at, or client_id_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 the client_secret field in the request, the value of this field 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 chosen 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 with new information:
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_uris":["https://client.example.org/callback",
"https://client.example.org/alt"],
"scope": "read write dolphin",
"grant_types": ["authorization_code", "refresh_token"]
"token_endpoint_auth_method": "client_secret_basic",
"jwks_uri": "https://client.example.org/my_public_keys.jwks"
"client_name":"My New Example",
"client_name#fr":"Mon Nouvel Exemple",
"logo_uri":"https://client.example.org/newlogo.png"
"logo_uri#fr":"https://client.example.org/fr/newlogo.png"
}
Upon successful update, the authorization server responds with an HTTP 200 OK Message with content type application/json and a payload as described in Client Information Response [client-info-response]. Some values in the response, including the client_secret and registration_access_token, MAY be different from those in the initial registration response. If the authorization server includes a new client secret and/or registration access token in its response, the client MUST immediately discard its previous client secret and/or registration access token. The value of the client_id MUST NOT change from the initial registration response.
If the registration access token used to make this request is not valid, the server MUST respond with an error as described in OAuth Bearer Token Usage [RFC6750].
If the client does not exist on this server, the server MUST respond with HTTP 401 Unauthorized, and the registration access token used to make this request SHOULD be immediately revoked.
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 [DynReg].
To deprovision itself on the authorization server, the client makes an HTTP DELETE request to the client configuration 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 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 the server does not support the delete method, the server MUST respond with an HTTP 405 Not Supported.
If the registration access token used to make this request is not valid, the server MUST respond with an error as described in OAuth Bearer Token Usage [RFC6750].
If the client does not exist on this server, the server MUST respond with HTTP 401 Unauthorized and the registration access token used to make this request SHOULD be immediately revoked.
If the client is not allowed to delete itself, the server MUST respond with HTTP 403 Forbidden.
Following is a non-normative example response:
HTTP/1.1 204 No Content Cache-Control: no-store Pragma: no-cache
In response to certain requests from the client to either the client registration endpoint or the client configuration endpoint as described in this specification, the authorization server sends the following response bodies.
This specification extends the client information response defined in OAuth 2.0 Core Client Dynamic Registration. The response contains the client identifier as well as the client secret, if the client is a confidential client. The response also contains the fully qualified URL of the client configuration 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 configuration 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
Pragma: no-cache
{
"registration_access_token": "reg-23410913-abewfq.123483",
"registration_client_uri":
"https://server.example.com/register/s6BhdRkqt3",
"client_id":"s6BhdRkqt3",
"client_secret": "cf136dc3c1fc93f31185e5885805d",
"client_id_issued_at":2893256800
"client_secret_expires_at":2893276800
"client_name":"My Example Client",
"client_name#ja-Jpan-JP":
"\u30AF\u30E9\u30A4\u30A2\u30F3\u30C8\u540D",
"redirect_uris":["https://client.example.org/callback",
"https://client.example.org/callback2"]
"scope": "read write dolphin",
"grant_types": ["authorization_code", "refresh_token"]
"token_endpoint_auth_method": "client_secret_basic",
"logo_uri": "https://client.example.org/logo.png",
"jwks_uri": "https://client.example.org/my_public_keys.jwks"
}
This specification makes no requests of IANA.
Since the client configuration endpoint is an OAuth 2.0 protected resource, it 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. For instance, a rogue client might use the name and logo for the legitimate client which it is trying to impersonate. Additionally, a rogue client might try to use the software identifier or software version of a legitimate client to attempt to associate itself on the authorization server instances of the legitimate client. To counteract this, an authorization server needs to take steps to mitigate this phishing risk by looking at the entire registration request and client configuration. 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 could also refuse registration from a known software identifier that is requesting different redirect URIs or a different client homepage uri. An authorization server can also present warning messages to end users about dynamically registered clients in all cases, especially if such clients have been recently registered or 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_uri, tos_uri, client_uri, and policy_uri). For instance, a rogue client could specify a registration request with a reference to a drive-by download in the policy_uri. The authorization server SHOULD check to see if the logo_uri, tos_uri, client_uri, and policy_uri have the same host and scheme as the those defined in the array of redirect_uris and that all of these resolve to valid web pages.
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 developer or client could be left in a situation where they have no means of retrieving or updating the client's registration information. Were that the case, a new registration would be required, thereby generating a new client identifier. However, to limit the exposure surface of the registration access token, the registration access token MAY be rotated when the developer or client does a read or update operation on the client's client configuration endpoint. As the registration access tokens are relatively long-term credentials, and since the registration access token is a Bearer token and acts as the sole authentication for use at the client configuration endpoint, it MUST be protected by the developer or client as described in OAuth 2.0 Bearer Token Usage [RFC6750].
If a client is deprovisioned from a server, any outstanding registration access token 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 configuration endpoint where the authentication would succeed but the action would fail because the client is no longer valid. To prevent accidental disclosure from such an erroneous situation, the authorization server MUST treat all such requests as if the registration access token was invalid (by returning an HTTP 401 Unauthorized error, as described).
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, Derek Atkins, Tim Bray, Domenico Catalano, Donald Coffin, Vladimir Dzhuvinov, George Fletcher, Thomas Hardjono, Phil Hunt, William Kim, Torsten Lodderstedt, Eve Maler, Josh Mandel, Nov Matake, Nat Sakimura, Christian Scholz, and Hannes Tschofenig.
[[ to be removed by the RFC editor before publication as an RFC ]]
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