| OAuth Working Group | N. Sakimura |
| Internet-Draft | Nomura Research Institute |
| Intended status: Standards Track | March 26, 2015 |
| Expires: September 27, 2015 |
Sender Constrained JWT for OAuth 2.0
draft-sakimura-oauth-rjwtprof-03
This discussion document describes a method to indicate a sender constraint within JWT. It could potentially be incorporated into POP spec.
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 [RFC2119].
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OAuth 2.0 Proof-of-Possession (PoP) Security Architecture [POPA] identifies Sender Constraint and Key Confirmation as a possible threat mitigation against the use of token by an unauthorized presenter. While Proof-Of-Possession Semantics for JSON Web Tokens (JWTs) [POPS] touches briefly on the Sender Constraint, it is only one paragraph within a introductory text and does not discuss it in detail. Instead, it devotes much of the discussion to the Key Confirmation method. It also is making the usage of such token against the resource out of scope.
This discussion draft describes a way to express the Sender Constraint in the JWT, as well as one possible way of using it to access a protected resource.
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 RFC 2119 [RFC2119].
Unless otherwise noted, all the protocol parameter names and values are case sensitive.
For the purpose of this document, the terms defined in RFC6749 [RFC6749] is used. In addition, following term is defined.
Sender Constraint is expressed by including the following member at the top level of JWT payload.
Follwoing is an example of such JWT payload.
{
"iss": "https://server.example.com",
"sub": "joe@example.com",
"azp": "clientID-1342050",
"aud": "https://client.example.org",
"exp": "1361398824",
"nbf": "1360189224",
}
Figure 3-1 Example of Sender Constrained JWT.
The resource that supports this specification MUST authenticate the Client. In this document a possible method is proposed as follows:
1. The authorized presenter issues a HEAD or GET request to the resource.
GET /resource/1234 HTTP/1.0 Host: server.example.com
2. The resource returns a HTTP 401 response with WWW-Authenticate header with "Named" scheme, whcih includes nonce.
HTTP/1.0 401 Unauthorized Server: HTTPd/0.9 Date: Wed, 14 March 2015 09:26:53 GMT WWW-Authenticate: Named nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093"
3. The client creates JWS compact seriarization over the nonce.
4. The client sends the request to the resource, this time with Authorize: header with Named scheme and access token and the JWS.
GET /resource/1234 HTTP/1.0 Host: server.example.com Authorization: Named at="access.token.jwt", s="jws.of.nonce"
5. The resource server finds the client key corresponding to the value of azp in the access token. It may have been obtained through client registration at the Issuer.
6. The resource server creates the JWS of the nonce and compare it with the value of s of the Authorization header. If it fails, the process stops here and the resource access MUST be denied.
7. The resource server MUST verify the access token. If it is valid, the resource SHOULD be returned as HTTP resonse.
This specification registers the Destination Claim defined herein in the IANA JSON Web Token Claims registry defined in [I-D.ietf-oauth-json-web-token].
Needless to say, the client's secret key must be kept securely.
TBD
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC6749] | Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, October 2012. |
| [POPA] | Hunt, P., "OAuth 2.0 Proof-of-Possession (PoP) Security Architecture", March 2015. |
| [POPS] | Jones, M., "Proof-Of-Possession Semantics for JSON Web Tokens (JWTs)", March 2015. |