ACE Working Group                                            O. Bergmann
Internet-Draft                                                       TZI
Updates: draft-ietf-ace-dtls-authorize (if             J. Preuß Mattsson
         approved)                                           G. Selander
Intended status: Standards Track                                Ericsson
Expires: 8 September 2022                                   7 March 2022

           Extension of the CoAP-DTLS Profile for ACE to TLS


   This document updates the CoAP-DTLS profile for ACE
   [I-D.ietf-ace-dtls-authorize] by specifying that the profile applies
   to TLS as well as DTLS.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Authentication and
   Authorization for Constrained Environments Working Group mailing list
   (ace@ietf.org), which is archived at

   Source for this draft and an issue tracker can be found at

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 8 September 2022.

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Copyright Notice

   Copyright (c) 2022 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 (https://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
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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Connection Establishment  . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   [I-D.ietf-ace-dtls-authorize] only specifies the use of DTLS
   [RFC6347] but works equally well for TLS [RFC8446].  For many
   constrained implementations, CoAP over UDP [RFC7252] is the first
   choice, but when deploying ACE in networks controlled by other
   entities (such as the Internet), UDP might be blocked on the path
   between the client and the RS, and the client might have to fall back
   to CoAP over TCP [RFC8323] for NAT or firewall traversal.  This
   feature is supported by the OSCORE profile
   [I-D.ietf-ace-oscore-profile] but is lacking in the DTLS profile.

   This document updates [I-D.ietf-ace-dtls-authorize] by specifying
   that the profile applies to TLS as well as DTLS.  The same access
   rights are valid in case transport layer security is provided by
   either DTLS or TLS, and the same access token can be used.
   Therefore, the value coap_dtls in the ace_profile parameter of an AS-
   to-Client response or in the ace_profile claim of an access token
   indicates that either DTLS or TLS can be used for transport layer

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Readers are expected to be familiar with the terms and concepts
   described in [I-D.ietf-ace-oauth-authz] and

3.  Connection Establishment

   Following the procedures defined in [I-D.ietf-ace-dtls-authorize], a
   Client can retrieve an Access Token from an Authorization Server (AS)
   in order to establish a security association with a specific Resource
   Server.  The ace_profile parameter in the Client-to-AS request and
   AS-to-client response is used to determine the ACE profile that the
   Client uses towards the Resource Server (RS).

   In case the ace_profile parameter indicates the use of the DTLS
   profile for ACE as defined in [I-D.ietf-ace-dtls-authorize], the
   Client MAY try to connect to the Resource Server via TLS, or try TLS
   and DTLS in parallel to accelerate the session setup.

   As resource-constrained devices are not expected to support both
   transport layer security mechanisms, a Client that implements either
   TLS or DTLS but not both might fail in establishing a secure
   communication channel with the Resource Server altogether.  This
   error SHOULD be handled by the Client in the same way as unsupported
   ACE profiles.  If the Client is modified accordingly or it learns
   that the Resource Server has been, the Client may try to connect to
   the Resource Server using the transport layer security mechanism that
   was previously not mutually supported.

   Note that a communication setup with an a priori unknown Resource
   Server typically employs an initial unauthorized resource request as
   illustrated in Section 2 of [I-D.ietf-ace-dtls-authorize].  If this
   message exchange succeeds, the Client SHOULD first use the same
   underlying transport protocol for the establishment of the security
   association as well (i.e., DTLS for UDP, and TLS for TCP).

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   As a consequence, the selection of the transport protocol used for
   the initial unauthorized resource request also depends on the
   transport layer security mechanism supported by the Client.  Clients
   that support either DTLS or TLS but not both SHOULD use the transport
   protocol underlying the supported transport layer security mechanism
   also for an initial unauthorized resource request.

4.  IANA Considerations

   The following updates have been done for the "ACE Profiles" registry
   for the profile with Profile ID 1 and Profile name coap_dtls:

   Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]"
   with the RFC number of this specification and delete this paragraph.

   Description: Profile for delegating client Authentication and
   Authorization for Constrained Environments by establishing a Datagram
   Transport Layer Security (DTLS) or Transport Layer Security (TLS)
   channel between resource-constrained nodes.

   Change Controller: IESG

   Reference: [RFC-XXXX]

5.  Security Considerations

   The security consideration and requirements in TLS 1.3 [RFC8446] and
   BCP 195 [RFC7525] [RFC8996] also apply to this document.

6.  References

6.1.  Normative References

              Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and
              L. Seitz, "Datagram Transport Layer Security (DTLS)
              Profile for Authentication and Authorization for
              Constrained Environments (ACE)", Work in Progress,
              Internet-Draft, draft-ietf-ace-dtls-authorize-18, 4 June
              2021, <https://www.ietf.org/archive/id/draft-ietf-ace-

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              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)", Work in Progress, Internet-Draft,
              draft-ietf-ace-oauth-authz-46, 8 November 2021,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,

   [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>.

   [RFC8323]  Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
              Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
              Application Protocol) over TCP, TLS, and WebSockets",
              RFC 8323, DOI 10.17487/RFC8323, February 2018,

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,

6.2.  Informative References

              Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson,
              "OSCORE Profile of the Authentication and Authorization
              for Constrained Environments Framework", Work in Progress,
              Internet-Draft, draft-ietf-ace-oscore-profile-19, 6 May
              2021, <https://www.ietf.org/archive/id/draft-ietf-ace-

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   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC8996]  Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
              1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,


   The authors would like to thank Marco Tiloca for reviewing this

Authors' Addresses

   Olaf Bergmann
   Universität Bremen TZI
   Bremen, D-28359
   Email: bergmann@tzi.org

   John Preuß Mattsson
   Ericsson AB
   SE-164 80 Stockholm
   Email: john.mattsson@ericsson.com

   Göran Selander
   Ericsson AB
   SE-164 80 Stockholm
   Email: goran.selander@ericsson.com

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