Stateless Client Identifier for OAuth
2
This draft provides a method for communicating information about an
OAuth client through its client identifier allowing for fully stateless
operation.
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 RFC 2119.
In the OAuth 2.0 Authorization protocol, the Client must provide a
Client Identifier that the Authorization Server recognizes.
Additionally, an Autorization Server needs to know about a client's
details, such as its name and redirect URIs. Traditionally, this is
handled through a registration process, which may be either manual or
automated, where the authorization server maintains a stateful
relationship between the Client Identifier and its associated metadata.
This draft proposes a mechanism whereby the essential metadata can be
encoded into the Client Identifier itself, signed by the issuer, and
validated by the authorization server, thus allowing the authorization
server to be stateless in regard to client information.
The stateless client identifier consists of a [JWT], optionally
signed with [JWS], whose payload contains claims as defined here.
REQUIRED. URL identifying the party that issued
this client identifier.
REQUIRED. Identifier of the client, locally unique
to the issuer.
OPTIONAL. Timestamp of when this client identifier
was issued.
OPTIONAL. Timestamp of when this client identifier
will expire.
RECOMMENDED if signed. Identifier of the key used
to sign this client identifier at the issuer.
REQUIRED. JSON Object containing a set of metadata
claims of client information such as its redirect URIs, display
name, and other items as defined in [Dyn Reg] and its
extensions.
The issuer SHOULD sign the JWT with JWS in such a way that the
signature can be verified by the authorization server.
The issuer MAY encrypt the JWT with JWE.
Upon receiving a stateless client identifier at either the
authorization endpoint or the token endpoint, the authorization server
parses it as a JWT. It first checks the iss field to determine if it
trusts identifiers issued by the party represented. It then verifies the
signature if the JWT (if signed) using JWS. The key used to sign the JWT
MAY be indicated by the kid field. The authorization server MAY use
other means to validate the JWT and determine its authenticity.
The authorization server then reads the fields inside the reg claim
and uses these to configure the user experience and security parameters
of the authorization.
The client identifier is intended to be opaque to the client, and as
such a stateless client identifier is intended to be obtained and used
in exactly the same way as a stateful client identifer would be for any
OAuth client.
Manual registration: a developer uses an out-of-band
adminstrative process to generate the client identifier and related
credentials.
Dynamic registration: a developer or client uses the process
described in [Dyn Reg] to generate the client identifier and related
credentials.
Self assertion: a developer or client generates the client
identifier on their own, often signing it with their own public
key.
It is completely up to the purview of particular authorization
servers which generation methods, and which client identifiers, they
will accept.
[ maybe we register the "reg" claim above? ]
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
Since many OAuth systems assume that a change in the client
identifier indicates a change in the client itself, systems using
stateless client identifiers SHOULD NOT allow clients to update their
information post registration.
Since the client identifier is passed through the browser to the
authorization endpoint, it MUST NOT contain any sensitive information.
Additionally, as in standard OAuth, posession of the client identifier
itself MUST NOT be assumed to be sufficient authentication [in many
cases? except implicit mode?].