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Versions: 00 01 02 draft-erdtman-oauth-rpcc

ACE Working Group                                               L. Seitz
Internet-Draft                                                 RISE SICS
Intended status: Informational                                S. Erdtman
Expires: May 3, 2018                                          Spotify AB
                                                        October 30, 2017


     Raw-Public-Key and Pre-Shared-Key as OAuth client credentials
                       draft-erdtman-ace-rpcc-02

Abstract

   This document describes Transport Layer Security (TLS) authentication
   using Raw-Public-Key and Pre-Shared-Key as new mechanisms for OAuth
   client authentication.  Although defined for TLS the mechanisms are
   equally applicable for DTLS.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 3, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Pre-Shared-Key for Client Authentication  . . . . . . . . . .   3
   3.  Raw-Public-Key for Client Authentication  . . . . . . . . . .   3
   4.  Dynamic Registration  . . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  OAuth Dynamic Client Registration Metadata Registration .   4
       6.1.1.  Registry Contents . . . . . . . . . . . . . . . . . .   5
     6.2.  Token Endpoint Authentication Method Registration . . . .   5
       6.2.1.  Registry Contents . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This document describes Transport Layer Security (TLS) authentication
   using Raw-Public-Key and Pre-Shared-Key as the mechanism for OAuth
   client authentication.  Examples of endpoint requiring client
   authentication are token and introspection.

   The OAuth 2.0 Authorization Framework [RFC6749] defines a shared
   secret method of client authentication but also allows for the
   definition and use of additional client authentication mechanisms
   when interacting with the authorization server's token endpoint.
   This document describes two additional mechanisms of client
   authentication utilizing Raw-Public-Key [RFC7250] and Pre-Shared-Key
   TLS [RFC4279], which provide better security characteristics than
   shared secrets.

   To get most bennefits and improved security with these new client
   credential types it is recomended to use the 'one credential per
   Client Software Instance' paradigm.  This can be achived by letting
   the client dynamicly register as described in [RFC7591].

1.1.  Requirements Language

   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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2.  Pre-Shared-Key for Client Authentication

   The following section defines, as an extension of OAuth 2.0,
   Section 2.3 [RFC6749], using Pre-Shared-Key with TLS [RFC4279] to
   authenticate the client.  This method is registered as
   'tls_client_psk' in "OAuth Token Endpoint Authentication Methods"
   registry.  If this method is to be used, the client and the
   Authorization Server MUST share a secret key, and they MUST agree on
   an identifier for this key.

   The (D)TLS handshake MUST be done according to [RFC4279], with the
   client indicating support for one or more Pre-Shared-Key cipher
   suites and authorization server selecting a Pre-Shared-Key cipher
   suite.  In order to enable the authorization server to select the
   correct pre-shared-key the client MUST send the key identifier in the
   psk-identity field of the ClientKeyExchange message.  How the
   authorization server maps the identifier to a pre-shared-key, and to
   a specific client is out of scope for this specification.

   Note that the key identifier MUST be 2^16 bytes or shorter, in order
   to fit into the psk-identity field.

3.  Raw-Public-Key for Client Authentication

   The following section defines, as an extension of OAuth 2.0,
   Section 2.3 [RFC6749], the use of Raw-Public-Key with (D)TLS
   [RFC7250] to authenticate the client.  This method is registered as
   'tls_client_rpk' in "OAuth Token Endpoint Authentication Methods"
   registry.

   The (D)TLS handshake MUST be done according to [RFC7250], with the
   client indicating support for Raw-Public-Key certificates and the
   authorization server asking client send its Raw Public Key
   certificate.  Since the client cannot send an explicit client or key
   identifier in the handshake, the authorization server MUST derive a
   client identifier from RPK that the client uses.

   Note to implementers: Authorization servers can use the following
   method to map a Raw Public Key to a client identifier: The client
   identifier is generated from the Raw Public Key using the procedure
   specified in section 3 of [RFC6920].  The digest is calculated on the
   Raw Public Key only (not on the SubjectPublicKeyInfo used in the
   handshake).  An example is shown in Figure 1.








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            Raw Public Key (Base64 encoded):
            MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEEtboxNKPgxEKV9JTNzy
            tUvAbxEfkCTVB9kOzheF5wRAoOz2NKP+ln+XLVAQSp1D6jfo09tppvN
            poQA1nnBNH6A==";

            Encoding:
            ni:///sha-256;xzLa24yOBeCkos3VFzD2gd83Urohr9TsXqY9nhdDN0

        Figure 1: Example encoding of a raw public key in the Named
                          Information URI Format

4.  Dynamic Registration

   For dynamic registration of a RPK this specification registers the
   new parameter 'rpk' to the Client Registration Metadata Registry.
   When used this parameter MUST contain a JSON Web Key representing the
   public key of the client.  When 'rpk' is present in the registration
   request 'token_endpoint_auth_method' MUST include 'tls_client_rpk'.

   For dynamic registration of a PSK this specification registers the
   new parameter 'psk' to the Client Registration Metadata Registry.
   When used this parameter MUST contain a JSON Web Key representing the
   key of the client.  When registering the client can include the key
   in the registrations request or the authorisation can generate the
   key and return it.  If the 'psk' attribute is present in a request
   'token_endpoint_auth_method' MUST include 'tls_client_psk'.  To
   request the authorisation server to generate the key the client
   includes 'tls_client_psk' in 'token_endpoint_auth_method' but does
   not send 'psk' attribute.

   The 'jwks' and 'jwks_uri' is not used to avoid conflict and confusion
   with application layer keys.

5.  Acknowledgements

   This document is highly inspired by [I-D.ietf-oauth-mtls] written by
   B.  Campbell, J.  Bradley, N.  Sakimura and T.  Lodderstedt.

6.  IANA Considerations

6.1.  OAuth Dynamic Client Registration Metadata Registration

   This specification requests registration of the following value in
   the IANA "OAuth Dynamic Client Registration Metadata" registry
   [IANA.OAuth.Parameters] established by [RFC7591].






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6.1.1.  Registry Contents

   o  Client Metadata Name: "rpk"
   o  Client Metadata Description: JWK for client Raw-Public-Key, can be
      included in request.
   o  Change Controller: IESG
   o  Specification Document(s): [[ this specification ]]

   o  Client Metadata Name: "psk"
   o  Client Metadata Description: JWK for client Pre-Shared-Key, can be
      included both in request and response.
   o  Change Controller: IESG
   o  Specification Document(s): [[ this specification ]]

6.2.  Token Endpoint Authentication Method Registration

   This specification requests registration of the following value in
   the IANA "OAuth Token Endpoint Authentication Methods" registry
   [IANA.OAuth.Parameters] established by [RFC7591].

6.2.1.  Registry Contents

   o  Token Endpoint Authentication Method Name: "tls_client_rpk"
   o  Change Controller: IESG
   o  Specification Document(s): [[ this specification ]]

   o  Token Endpoint Authentication Method Name: "tls_client_psk"
   o  Change Controller: IESG
   o  Specification Document(s): [[ this specification ]]

7.  Security Considerations

   TBD

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4279]  Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
              Ciphersuites for Transport Layer Security (TLS)",
              RFC 4279, DOI 10.17487/RFC4279, December 2005,
              <https://www.rfc-editor.org/info/rfc4279>.




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   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.

   [RFC6920]  Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
              Keranen, A., and P. Hallam-Baker, "Naming Things with
              Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,
              <https://www.rfc-editor.org/info/rfc6920>.

   [RFC7250]  Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
              Weiler, S., and T. Kivinen, "Using Raw Public Keys in
              Transport Layer Security (TLS) and Datagram Transport
              Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
              June 2014, <https://www.rfc-editor.org/info/rfc7250>.

   [RFC7591]  Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
              P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
              RFC 7591, DOI 10.17487/RFC7591, July 2015,
              <https://www.rfc-editor.org/info/rfc7591>.

8.2.  Informative References

   [I-D.ietf-oauth-mtls]
              Campbell, B., Bradley, J., Sakimura, N., and T.
              Lodderstedt, "Mutual TLS Profile for OAuth 2.0", draft-
              ietf-oauth-mtls-04 (work in progress), October 2017.

   [IANA.OAuth.Parameters]
              IANA, "OAuth Parameters",
              <http://www.iana.org/assignments/oauth-parameters>.

Authors' Addresses

   Ludwig Seitz
   RISE SICS
   Scheelevaegen 17
   Lund  223 70
   SWEDEN

   Email: ludwig.seitz@ri.se











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   Samuel Erdtman
   Spotify AB
   Birger Jarlsgatan 61, 4tr
   Stockholm  113 56
   Sweden

   Email: erdtman@spotify.com












































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