| Open Authentication Protocol | A. Parecki |
| Internet-Draft | Okta |
| Intended status: Standards Track | May 08, 2020 |
| Expires: November 9, 2020 |
OAuth 2.0 Client Intermediary Metadata
draft-parecki-oauth-client-intermediary-metadata-01
This specification defines a mechanism for including information about additional parties involved in an OAuth transaction by adding a new section to the OAuth 2.0 Dynamic Client Registration request, as well as requires that authorization servers surface this information to users during an OAuth transaction.
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In some applications of OAuth, an OAuth client is acting on behalf of one or more intermediary or user-facing applications, and is not the entity that the user has an established relationship with. In the traditional OAuth model, a client_id represents only one application, and so the consent screen lists just one third party: the OAuth client. In these cases, it is not appropriate to list only the actual OAuth client or only the user-facing application. Listing only the actual OAuth client would be confusing to the user, since the user does not have a relationship with this entity. Listing only the user-facing application would be inaccurate and misrepresent the situation, since the user would be unaware that their data is actually being handled by additional parties.
This specification extends [RFC7591] and [RFC7592] to define a mechanism for including information about the additional parties involved in an OAuth transaction by including information about the additional intermediaries as well as the user-facing application into the Dynamic Client Registration request. This specification also defines requirements of the OAuth authorization server to present this information about the additional parties in the OAuth consent screen during an OAuth transaction.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "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.
In addition to the terms defined in referenced specifications, this document uses the following terms:
Registered end user applications, as well as intermediaries, have a set of metadata values associated with the client identifier of the client that represents them in the OAuth transaction, such as a user-visible name, logo, and URL.
Like the OAuth client metadata defined in [RFC7591] and [RFC7592], these metadata values are used in the following ways:
These values are used by the authorization server when displaying the OAuth consent screen to the end user, to inform them of all the additional parties that will be handling the user's data upon approval.
The following metadata fields are defined by this specification. The implementation and use of the fields is OPTIONAL unless stated otherwise. All data member types (strings, arrays, numbers) are defined in terms of their JSON ([RFC7159]) representations.
Some fields are expected to be displayed in the OAuth consent UI and are designated accordingly.
name
REQUIRED. A human-readable name of the end user application or intermediary. Authorization servers MUST display this field to the end user on the OAuth consent screen.
description
REQUIRED. A human-readable description of the end user application or intermediary. This is not intended to be displayed in the OAuth consent screen.
uri
A URL string of a web page providing information about the end user application or intermediary. If present, the authorization server SHOULD display this URL to the end user in a clickable fashion. It is RECOMMENDED that clients always send this field. The value of this field MUST point to a valid web page.
logo_uri
A URL string that references a logo for this end user application or intermediary. If present, the authorization server SHOULD display this image to the end user in the OAuth consent screen. The value of this field MUST be a valid image file.
contacts
Array of strings representing ways to contact people responsible for this end user application or intermediary, typically email addresses or phone numbers. The authorization server MAY display these to the end user in the OAuth consent screen. See Section 6 of [RFC7591] for information on Privacy Considerations.
The client registration endpoint is described in Section 3 of [RFC7591].
Since this specification provides a mechanism for a client to assert user information about additional parties other than itself, the registration endpoint MUST be protected by an OAuth 2.0 access token obtained by the client. The method by which the initial access token is obtained by the client or developer is out of scope of this specification, but is likely to be obtained using the client credentials grant.
This specification extends the client registration request defined in [RFC7591].
This operation registers a combination of client, end user application, and optionally one or more intermediaries with an authorization server. The authorization server assigns a unique client identifier (and optionally a client secret) that represents the combination of all the entities described in the registration request.
To register, the client or developer sends an HTTP POST as described in Section 3.1 of [RFC7591], with an additional property named "end_user_application" containing a JSON object with the end user application registration information, and optionally a property named "intermediaries" with a JSON array of objects of each intermediary's registration information.
For example, the client could send the following registration request to the client registration endpoint using its OAuth 2.0 access token it has previously obtained using the client credentials grant.
The following is a non-normative example request:
POST /register HTTP/1.1
Content-Type: application/json
Accept: application/json
Host: server.example.com
Authorization: Bearer 8IGFGXKXZBV5LL38Y3X1
{
"client_name": "My Example Client",
"redirect_uris": [
"https://client.example.org/callback"
],
"logo_uri": "https://client.example.org/logo.png",
"end_user_application": {
"name": "User-Recognizable App Name",
"description": "This application is what the user
is interacting with in their browser",
"uri": "https://example.net/",
"logo_uri": "https://example.net/logo.png",
"contacts": [
"support@example.net"
]
},
"intermediaries": [
{
"name": "Partner App Name",
"description": "An application that may also receive
this user's data when the user authorizes the client",
"uri": "https://partner.example/",
"logo_uri": "https://partner.example/logo.png",
"contacts": [
"support@partner.example"
]
}
]
}
This specification extends the client information response defined in [RFC7591] and [RFC7592].
Upon a successful registration request, the authorization server returns a client identifier for the combination of the client, end user application, and any intermediaries specified in the request.
In addition to the response fields defined in Section 3.2 of [RFC7591] and Section 3 of [RFC7592], the response MUST also contain all registered metadata about the end user application and any intermediaries. The authorization server MAY reject or replace any of the requested metadata values submitted during the registration and substitute them with suitable values.
The following is a non-normative example response of a successful registration:
HTTP/1.1 201 Created
Content-Type: application/json
Cache-Control: no-store
Pragma: no-cache
{
"client_id": "V8tvEkZWhDAdxSaKGUJZ",
"client_secret": "SpsuwZIxnp8bBEhp5sk1EKiIKTZ4X4DKU",
"grant_types": ["authorization_code", "refresh_token"],
"token_endpoint_auth_method": "client_secret_basic",
"registration_client_uri": "https://server.example.com/client/tmzaAMkyWlH3",
"registration_access_token": "MphaAqDaZT86C93ENWRZcf3dfU2dW6POASo8dFXa",
"client_name": "My Example Client",
"redirect_uris": [
"https://client.example.org/callback"
],
"logo_uri": "https://client.example.org/logo.png",
"end_user_application": {
"name": "User-Recognizable App Name",
"description": "This application is what the user is interacting
with in their browser",
"uri": "https://example.net/",
"logo_uri": "https://example.net/logo.png",
"contacts": [
"support@example.net"
]
},
"intermediaries": [
{
"name": "Partner App Name",
"description": "An application that may also receive
this user's data when the user authorizes the client",
"uri": "https://partner.example/",
"logo_uri": "https://partner.example/logo.png",
"contacts": [
"support@partner.example"
]
}
]
}
The registration_client_uri and registration_access_token properties are required in order to support updating and deleting this client as described in [RFC7592].
This specification extends the client read request defined in [RFC7592] to include the additional metadata properties in the response that describe the end user application and intermediaries. No additional behavior is prescribed by this specification.
This specification extends the client update request defined in [RFC7592] to be able to update the additional metadata properties that describe the end user application and intermediaries.
The additional properties are provided in the update request in the same format as in the initial registration request.
Since these values were asserted by the client in the initial registration, there is no need to prescribe any additional security model around the ability to update them, even though these represent additional parties.
No new behavior is prescribed for delete requests beyond that defined in [RFC7592].
When the authorization server begins a request from an OAuth client identifier that has been registered with additional end user application or intermediary information, it MUST display the additional parties in the consent UI visible to the end user.
The authorization server MAY choose to emphasize or make the end user application information the primary information displayed in the consent screen. This is because the end user application is likely the most recognizable entity to the end user, and the end user may not be aware that it is actually a different organization's OAuth client that is the one making requests for the user's data.
The authorization server chooses how best to display the additional information, but it MUST include at least the name of the end user application, intermediaries, and client, and SHOULD include the logo of each as well.
Once an access token has been issued to this client, the client uses the access token to make requests at the resource server on behalf of the specific end user application on behalf of the end user.
As this extends [RFC7591], all security considerations from that draft apply here as well.
Specifically, if the authorization server supports open client registration without any authentication, it must be careful with any URLs received in the registration request such as logo_uri, tos_uri, and uri, as these values will be shown to end users. [RFC7591] recommends requiring that these URIs have a matching host and scheme as the defined redirect_uris, and that they are resolvable URIs. See section 5 of [RFC7591] for more details.
The authors would like to thank Ryan Christiansen and Preston McFarland for their initial contributions of the concepts behind this specification. The authors would also like to thank Don Cardinal, Ryan Christiansen and Preston McFarland for their reviews of this specification. Additionally the work of the OAuth Working Group on the referenced and related specifications that this specification builds upon is much appreciated.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC6749] | Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012. |
| [RFC7159] | Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014. |
| [RFC7591] | Richer, J., Jones, M., Bradley, J., Machulak, M. and P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol", RFC 7591, DOI 10.17487/RFC7591, July 2015. |
| [RFC7592] | Richer, J., Jones, M., Bradley, J. and M. Machulak, "OAuth 2.0 Dynamic Client Registration Management Protocol", RFC 7592, DOI 10.17487/RFC7592, July 2015. |