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ACE Working Group                                               L. Seitz
Internet-Draft                                                      RISE
Intended status: Standards Track                       November 26, 2018
Expires: May 30, 2019


      Additional OAuth Parameters for Authorization in Constrained
                           Environments (ACE)
                     draft-ietf-ace-oauth-params-01

Abstract

   This specification defines new parameters for the OAuth 2.0 token and
   introspection endpoints when used with framework for authentication
   and authorization for constrained environments (ACE).  These are used
   to express the desired audience of a requested access token, the
   desired proof-of-possession key, the proof-of-possession key that the
   AS has selected, and the key the RS should use to authenticate to the
   client.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 30, 2019.

Copyright Notice

   Copyright (c) 2018 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Parameters for the Token Endpoint . . . . . . . . . . . . . .   3
     3.1.  Client-to-AS Request  . . . . . . . . . . . . . . . . . .   3
     3.2.  AS-to-Client Response . . . . . . . . . . . . . . . . . .   4
     3.3.  The Resource Server Confirmation Claim  . . . . . . . . .   6
   4.  Parameters for the Introspection Endpoint . . . . . . . . . .   6
     4.1.  AS-to-RS Response . . . . . . . . . . . . . . . . . . . .   6
   5.  Confirmation Method Parameters  . . . . . . . . . . . . . . .   7
   6.  CBOR Mappings . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  JSON Web Token Claims . . . . . . . . . . . . . . . . . .   9
     9.2.  CBOR Web Token Claims . . . . . . . . . . . . . . . . . .   9
     9.3.  OAuth Parameter Registration  . . . . . . . . . . . . . .  10
     9.4.  OAuth Introspection Response Parameter Registration . . .  10
     9.5.  Token Endpoint CBOR Mappings Registraton  . . . . . . . .  11
     9.6.  Introspection Endpoint CBOR Mappings Registraton  . . . .  11
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Overlap with OAuth work  . . . . . . . . . . . . . .  13
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   The Authentication and Authorization for Constrained Environments
   (ACE) specification [I-D.ietf-ace-oauth-authz] requires some new
   parameters for interactions with the OAuth 2.0 [RFC6749] token and
   introspection endpoints, as well as some new claims to be used in
   access tokens.  These parameters and claims can also be used in other
   contexts, and may need to be updated to align them with ongoing OAuth
   work.  Therefore they have been split out into this document, which
   can be used and updated independently of [I-D.ietf-ace-oauth-authz].

2.  Terminology

   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 BCP



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   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Readers are assumed to be familiar with the terminology from
   [I-D.ietf-ace-oauth-authz].

   Note that the term "endpoint" is used here following its OAuth 2.0
   [RFC6749] definition, which is to denote resources such as token and
   introspection at the AS and authz-info at the RS.  The CoAP [RFC7252]
   definition, which is "An entity participating in the CoAP protocol"
   is not used in this specification.

3.  Parameters for the Token Endpoint

3.1.  Client-to-AS Request

   This document defines the following additional parameters for
   requesting an access token from a token endpoint in the ACE framework
   [I-D.ietf-ace-oauth-authz]:

   req_aud
      OPTIONAL.  Specifies the audience for which the client is
      requesting an access token.  If this parameter is missing, it is
      assumed that the AS has a default audience for access tokens
      issued to this client.  If a client submits a request for an
      access token without specifying a "req_aud" parameter, and the AS
      does not have a default audience value for this client, then the
      AS MUST respond with an error message using a response code
      equivalent to the CoAP response code 4.00 (Bad Request).  Values
      of this parameter follow the syntax of the "aud" claim from
      section 3.1.3 of [RFC8392].

   req_cnf
      OPTIONAL.  This field contains information about the key the
      client would like to bind to the access token for proof-of-
      possession.  It is RECOMMENDED that an AS reject a request
      containing a symmetric key value in the 'req_cnf' field, since the
      AS is expected to be able to generate better symmetric keys than a
      potentially constrained client.  The AS MUST verify that the
      client really is in possession of the corresponding key.  Values
      of this parameter follow the syntax of the "cnf" claim from
      section 3.1 of [I-D.ietf-ace-cwt-proof-of-possession].

   Figure 1 shows a request for an access token using the "req_aud"
   parameter to request a specific audience and the "req_cnf" parameter
   to request a specific public key as proof-of-possession key.  The
   content is displayed in CBOR diagnostic notation, without
   abbreviations for better readability.



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   Header: POST (Code=0.02)
   Uri-Host: "as.example.com"
   Uri-Path: "token"
   Content-Format: "application/ace+cbor"
   Payload:
   {
      "req_aud" : "tempSensor4711",
      "req_cnf" : {
         "COSE_Key" : {
            "kty" : "EC",
            "kid" : h'11',
            "crv" : "P-256",
            "x" : b64'usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8',
            "y" : b64'IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4'
         }
      }
    }

   Figure 1: Example request for an access token bound to an asymmetric
                                   key.

3.2.  AS-to-Client Response

   This document defines the following additional parameters for an AS
   response to a request to the token endpoint:

   cnf
      REQUIRED if the token type is "pop" and a symmetric key is used.
      MAY be present for asymmetric proof-of-possession keys.  This
      field contains the proof-of-possession key that the AS selected
      for the token.  Values of this parameter follow the syntax of the
      "cnf" claim from section 3.1 of
      [I-D.ietf-ace-cwt-proof-of-possession].  See Section 5 for details
      on the use of this parameter.

   rs_cnf
      OPTIONAL if the token type is "pop" and asymmetric keys are used.
      MUST NOT be present otherwise.  This field contains information
      about the public key used by the RS to authenticate.  If this
      parameter is absent, either the RS does not use a public key or
      the AS assumes that the client already knows the public key of the
      RS.  Values of this parameter follow the syntax of the "cnf" claim
      from section 3.1 of [I-D.ietf-ace-cwt-proof-of-possession].  See
      Section 5 for details on the use of this parameter.

   Figure 2 shows an AS response containing a token and a "cnf"
   parameter with a symmetric proof-of-possession key.




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   Header: Created (Code=2.01)
   Content-Format: "application/ace+cbor"
   Payload:
   {
     "access_token" : b64'SlAV32hkKG ...
      (remainder of CWT omitted for brevity;
      CWT contains COSE_Key in the "cnf" claim)',
     "cnf" : {
       "COSE_Key" : {
         "kty" : "Symmetric",
         "kid" : b64'39Gqlw',
         "k" : b64'hJtXhkV8FJG+Onbc6mxCcQh'
       }
     }
   }

       Figure 2: Example AS response with an access token bound to a
                              symmetric key.

   Figure 3 shows an AS response containing a token bound to a
   previously requested asymmetric proof-of-possession key (not shown)
   and a "rs_cnf" parameter containing the public key of the RS.

   Header: Created (Code=2.01)
   Content-Format: "application/ace+cbor"
   Payload:
   {
     "access_token" : b64'SlAV32hkKG ...
      (remainder of CWT omitted for brevity;
      CWT contains COSE_Key in the "cnf" claim)',
     "rs_cnf" : {
       "COSE_Key" : {
         "kty" : "EC",
         "kid" : h'12',
         "crv" : "P-256",
         "x" : b64'vO5+qsFi+R5vMw9XcSEeIguLVGyWWJsKxK0P0kx34fE',
         "y" : b64'xkezjFXvu8TmLmUXIPAC1ddbLgwCzRMm5mK8oiK5BBY'
       }
     }
   }

       Figure 3: Example AS response with an access token bound to a
                              symmetric key.








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3.3.  The Resource Server Confirmation Claim

   If the AS needs to convey a hint to the RS about which key it should
   use to authenticate towards the client, this specification defines
   the "rs_cnf" claim, which MAY be used in the access token, with the
   same syntax and semantics as defined in for the "rs_cnf" parameter.

4.  Parameters for the Introspection Endpoint

4.1.  AS-to-RS Response

   This document defines the following additional parameters for an AS
   response to a request to the introspection endpoint:

   cnf
      OPTIONAL.  This field contains information about the proof-of-
      possession key that binds the client to the access token.  Values
      of this parameter follow the syntax of the "cnf" claim from
      section 3.1 of [I-D.ietf-ace-cwt-proof-of-possession].  See
      Section 5 for more details on the use of the "cnf" parameter.

   rs_cnf
      OPTIONAL.  If the RS uses asymmetric keys to authenticate towards
      the client (e.g. with a DTLS-RPK handshake) and it has several
      such keys (e.g. for different elliptic curves), the AS can give
      the RS a hint using this parameter, as to which key it should use.
      Values of this parameter follow the syntax of the "cnf" claim from
      section 3.1 of [I-D.ietf-ace-cwt-proof-of-possession].  See
      Section 5 for details on the use of this parameter.

   Figure 4 shows an AS response to an introspection request including
   the "cnf" parameter to indicate the proof-of-possession key bound to
   the token and the "rs_cnf" parameter to indicate the key the RS is
   supposed to use to authenticate to the client.

















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   Header: Created Code=2.01)
   Content-Format: "application/ace+cbor"
   Payload:
   {
     "active" : true,
     "scope" : "read",
     "aud" : "tempSensor4711",
     "cnf" : {
       "COSE_Key" : {
         "kty" : "EC",
         "kid" : h'11',
         "crv" : "P-256",
         "x" : b64'usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8',
         "y" : b64'IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4'
       }
     },
     "rs_cnf" : {
       "COSE_Key" : {
         "kty" : "EC",
         "kid" : h'12',
         "crv" : "P-256",
         "x" : b64'vO5+qsFi+R5vMw9XcSEeIguLVGyWWJsKxK0P0kx34fE',
         "y" : b64'xkezjFXvu8TmLmUXIPAC1ddbLgwCzRMm5mK8oiK5BBY'
       }
     }
   }

                 Figure 4: Example introspection response.

5.  Confirmation Method Parameters

   The confirmation method parameters are used as follows:

   o  "req_cnf" in the access token request C -> AS, OPTIONAL to
      indicate the client's raw public key, or the key-identifier of a
      previously established key between C and RS that the client wishes
      to use for proof-of-possession of the access token.
   o  "cnf" in the token response AS -> C, OPTIONAL if using an
      asymmetric key or a key that the client requested via a key
      identifier in the request.  REQUIRED if the client didn't specify
      a "req_cnf" and symmetric keys are used.  Used to indicate the
      symmetric key generated by the AS for proof-of-possession of the
      access token.
   o  "cnf" in the introspection response AS -> RS, REQUIRED if the
      access token that was subject to introspection is a proof-of-
      possession token, absent otherwise.  Indicates the proof-of-
      possession key bound to the access token.




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   o  "rs_cnf" in the token response AS -> C, OPTIONAL to indicate the
      public key of the RS, if it uses one to authenticate to the
      client.
   o  "rs_cnf" in the introspection response AS -> RS, OPTIONAL,
      contains the public key that the RS should use for authenticating
      to the client (e.g. if the RS has several different public keys).

   Note that the COSE_Key structure in a confirmation claim or parameter
   may contain an "alg" or "key_ops" parameter.  If such parameters are
   present, a client MUST NOT use a key that is not compatible with the
   profile or proof-of-possession algorithm according to those
   parameters.  An RS MUST reject a proof-of-possession using such a
   key.

   If an access token is issued for an audience that includes several
   RS, the "rs_cnf" parameter MUST NOT be used, since the client cannot
   determine for which RS the key applies.  This document recommends to
   specify a different endpoint that the client can use to acquire RS
   authentication keys in such cases.  The specification of such an
   endpoint is out of scope for this document.

6.  CBOR Mappings

   If CBOR is used, the new parameters and claims defined in this
   document MUST be mapped to CBOR types as specified in Figure 5, using
   the given integer abbreviation for the map key.

       /-----------------+----------+----------------------------------\
       | Parameter name  | CBOR Key | Value Type                       |
       |-----------------+----------+----------------------------------|
       | req_aud         |  3       | text string                      |
       | cnf             |  8       | map                              |
       | rs_cnf          | 11       | map                              |
       | req_cnf         | 12       | map                              |
       \-----------------+----------+----------------------------------/

                Figure 5: CBOR mappings for new parameters.

7.  Security Considerations

   This document is an extension to [I-D.ietf-ace-oauth-authz].  All
   security considerations from that document apply here as well.

   The audience claim as defined in [RFC7519] and the equivalent
   "req_aud" parameter are intentionally vague on how to match the
   audience value to a specific RS.  This is intended to allow
   application specific semantics to be used.  This section attempts to




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   give some general guidance for the use of audiences in constrained
   environments.

   URLs are not a good way of identifying mobile devices that can switch
   networks and thus be associated with new URLs.  If the audience
   represents a single RS, and asymmetric keys are used, the RS can be
   uniquely identified by a hash of its public key.  If this approach is
   used this framework RECOMMENDS to apply the procedure from section 3
   of [RFC6920].

   If the audience addresses a group of resource servers, the mapping of
   group identifier to individual RS has to be provisioned to each RS
   before the group-audience is usable.  Managing dynamic groups could
   be an issue, if the RS is not always reachable when the group
   memberships change.  Furthermore issuing access tokens bound to
   symmetric proof-of-possession keys that apply to a group-audience is
   problematic, as an RS that is in possession of the access token can
   impersonate the client towards the other RSs that are part of the
   group.  It is therefore NOT RECOMMENDED to issue access tokens bound
   to a group audience and symmetric proof-of possession keys.

8.  Privacy Considerations

   This document is an extension to [I-D.ietf-ace-oauth-authz].  All
   privacy considerations from that document apply here as well.

9.  IANA Considerations

9.1.  JSON Web Token Claims

   This specification registers the following new claim in the JSON Web
   Token (JWT) registry of JSON Web Token Claims
   [IANA.JsonWebTokenClaims]:

   o  Claim Name: "rs_cnf"
   o  Claim Description: The public key the RS is supposed to use to
      authenticate to the client wielding this token.
   o  Change Controller: IESG
   o  Reference: Section 3.3 of [this document]

9.2.  CBOR Web Token Claims

   This specification registers the following new claim in the "CBOR Web
   Token (CWT) Claims" registry [IANA.CborWebTokenClaims].

   o  Claim Name: "rs_cnf"
   o  Claim Description: The public key the RS is supposed to use to
      authenticate to the client wielding this token.



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   o  JWT Claim Name: N/A
   o  Claim Key: TBD (suggested: 39)
   o  Claim Value Type(s): map
   o  Change Controller: IESG
   o  Specification Document(s): Section 3.3 of [this document]

9.3.  OAuth Parameter Registration

   This section registers the following parameters in the "OAuth
   Parameters" registry [IANA.OAuthParameters]:

   o  Name: "req_aud"
   o  Parameter Usage Location: authorization request, token request
   o  Change Controller: IESG
   o  Reference: Section 3.1 of [this document]

   o  Name: "req_cnf"
   o  Parameter Usage Location: token request
   o  Change Controller: IESG
   o  Reference: Section 5 of [this document]

   o  Name: "rs_cnf"
   o  Parameter Usage Location: token response
   o  Change Controller: IESG
   o  Reference: Section 5 of [this document]

   o  Name: "cnf"
   o  Parameter Usage Location: token response
   o  Change Controller: IESG
   o  Reference: Section 5 of [this document]

9.4.  OAuth Introspection Response Parameter Registration

   This section registers the following parameters in the OAuth Token
   Introspection Response registry [IANA.TokenIntrospectionResponse].

   o  Name: "cnf"
   o  Description: Key to prove the right to use a PoP token.
   o  Change Controller: IESG
   o  Reference: Section 4.1 of [this document]

   o  Name: "rs_cnf"
   o  Description: The key the RS should use to authenticate to the
      client.
   o  Change Controller: IESG
   o  Reference: Section 4.1 of [this document]





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9.5.  Token Endpoint CBOR Mappings Registraton

   This section registers teh following parameter mappings in the "Token
   Endpoint CBOR Mappings" registry established in section 8.9. of
   [I-D.ietf-ace-oauth-authz].

   o  Name: "req_aud"
   o  CBOR key: 18
   o  Change Controller: IESG
   o  Reference: Section 3.1 of [this document]

   o  Name: "req_cnf"
   o  CBOR key: 19
   o  Change Controller: IESG
   o  Reference: Section 3.1 of [this document]

   o  Name: "cnf"
   o  CBOR key: 8
   o  Change Controller: IESG
   o  Reference: Section 3.2 of [this document]

   o  Name: "rs_cnf"
   o  CBOR key: 17
   o  Change Controller: IESG
   o  Reference: Section 3.2 of [this document]

9.6.  Introspection Endpoint CBOR Mappings Registraton

   This section registers teh following parameter mappings in the
   "Introspection Endpoint CBOR Mappings" registry established in
   section 8.11. of [I-D.ietf-ace-oauth-authz].

   o  Name: "cnf"
   o  CBOR key: 8
   o  Change Controller: IESG
   o  Reference: Section 4.1 of [this document]

   o  Name: "rs_cnf"
   o  CBOR key: 17
   o  Change Controller: IESG
   o  Reference: Section 4.1 of [this document]

10.  Acknowledgments

   This document is a product of the ACE working group of the IETF.

   Ludwig Seitz worked on this document as part of the CelticPlus
   project CyberWI, with funding from Vinnova.



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11.  References

11.1.  Normative References

   [I-D.ietf-ace-cwt-proof-of-possession]
              Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
              Tschofenig, "Proof-of-Possession Key Semantics for CBOR
              Web Tokens (CWTs)", draft-ietf-ace-cwt-proof-of-
              possession-05 (work in progress), November 2018.

   [I-D.ietf-ace-oauth-authz]
              Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
              H. Tschofenig, "Authentication and Authorization for
              Constrained Environments (ACE) using the OAuth 2.0
              Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-16
              (work in progress), October 2018.

   [IANA.CborWebTokenClaims]
              IANA, "CBOR Web Token (CWT) Claims",
              <https://www.iana.org/assignments/cwt/cwt.xhtml#claims-
              registry>.

   [IANA.JsonWebTokenClaims]
              IANA, "JSON Web Token Claims",
              <https://www.iana.org/assignments/jwt/jwt.xhtml#claims>.

   [IANA.OAuthParameters]
              IANA, "OAuth Parameters",
              <https://www.iana.org/assignments/oauth-parameters/oauth-
              parameters.xhtml#parameters>.

   [IANA.TokenIntrospectionResponse]
              IANA, "OAuth Token Introspection Response",
              <https://www.iana.org/assignments/oauth-parameters/oauth-
              parameters.xhtml#token-introspection-response>.

   [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>.

   [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>.







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   [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>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014, <https://www.rfc-
              editor.org/info/rfc7252>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8392]  Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
              "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
              May 2018, <https://www.rfc-editor.org/info/rfc8392>.

11.2.  Informative References

   [I-D.ietf-oauth-pop-key-distribution]
              Bradley, J., Hunt, P., Jones, M., Tschofenig, H., and M.
              Mihaly, "OAuth 2.0 Proof-of-Possession: Authorization
              Server to Client Key Distribution", draft-ietf-oauth-pop-
              key-distribution-04 (work in progress), October 2018.

   [I-D.ietf-oauth-resource-indicators]
              Campbell, B., Bradley, J., and H. Tschofenig, "Resource
              Indicators for OAuth 2.0", draft-ietf-oauth-resource-
              indicators-01 (work in progress), October 2018.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

Appendix A.  Overlap with OAuth work

   This document overlaps with draft work from OAuth, namely
   [I-D.ietf-oauth-pop-key-distribution] and
   [I-D.ietf-oauth-resource-indicators].

   The former specifies the use of "req_cnf" and "cnf" for requesting
   proof-of-possession tokens and indicating the key that the AS has
   selected.  It it was initially deemed that the work at OAuth had been
   discontinued and therefore equivalent functionality was defined here.
   Work in OAuth has since resumed, but it is lagging behind the planned
   milestones of the ACE working group.  We have therefore split this
   work out into a separate document so that it can later be updated or



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   obsoleted to align it with the final result of the OAuth work,
   without affecting [I-D.ietf-ace-oauth-authz].

   The latter defines the use of the "resource" parameter, allowing to
   indicate the location fo the target service or resource where access
   is being requested.  This partially overlaps with the "req_aud"
   parameter specified here, however the definition of "req_aud" is more
   broad, since it can be used in an application specific way that is
   not necessarily bound to the location of the target audience (e.g. a
   group identifier referring to several resource servers, or the public
   key of a resource server).

Author's Address

   Ludwig Seitz
   RISE
   Scheelevaegen 17
   Lund  223 70
   Sweden

   Email: ludwig.seitz@ri.se






























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