ACME Challenges Using an Authority Token
draft-peterson-acme-authority-token-00

Network Working Group                                        J. Peterson
Internet-Draft                                                   Neustar
Intended status: Informational                          October 30, 2017
Expires: May 3, 2018

                ACME Challenges Using an Authority Token
               draft-peterson-acme-authority-token-00.txt

Abstract

   A number of proposed challenges for the Automated Certificate
   Management Environment (ACME) effectively rely on an external
   authority issuing a token according to a particular policy.  This
   document specifies a generic Authority Token challenge for ACME which
   admits of subtypes for different identifiers or namespaces.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Challenges for an Authority Token . . . . . . . . . . . . . .   3
     3.1.  Token Type Requirements . . . . . . . . . . . . . . . . .   4
   4.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   ACME [I-D.ietf-acme-acme] is a mechanism for automating certificate
   management on the Internet.  It enables administrative entities to
   prove effective control over resources like domain names, and
   automtes the process of generating and issuing certificates.

   In some cases, proving effective control over an identifier requires
   an attestation from a third policy who has authority over the
   resource, for example, an external policy administrator for a
   namespace other than the DNS.  In order to automate the process of
   issuing certificates for those resources, this specification defines
   a generic Authority Token challenge that ACME servers can issue in
   order to acquire such a token.  The challenge contains a type
   indication that tells the client what sort of token it needs to
   acquire.  It is expected that the Authority Token challenge will be
   usable for a variety of identifer types.

   For example, the system of [I-D.ietf-acme-service-provider] provides
   a mechanism that allows service providers to acquire certificates
   corresponding to a Service Provider Code (SPC) as defined in
   [I-D.ietf-stir-certificates] by consulting an external authority
   responsible for those codes.  Furthermore, Communications Service
   Providers (CSPs) can delegate authority over numbers to their
   customers, and those CSPs who support ACME can then help customers to
   acquire certificates for those numbering resources with ACME.  This
   can permit number acquisition flows compatible with those shown in
   [I-D.ietf-modern-problem-framework].  Another, similar example would
   a mechanism that permits CSPs to delegate authority for particular
   telephone numbers to customers, as described in
   [I-D.ietf-acme-telephone].

   This draft is a stub intended for discussing different approaches to
   genericizing the token challenge methods under consideration.

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2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in [RFC2119].

3.  Challenges for an Authority Token

   Proving that a device on the Internet has effective control over a
   non-Internet resource is not as straightforward as proving control
   over an Internet resources like a DNS zone or a web page.  Provided
   that the issuer of identifiers, or someone acting on their behalf,
   can implement a service that grants tokens to the people to whom it
   has issued identifiers, however, a token could be used as a response
   to an ACME challenge.

   This challenge type requires a new "token-type" element, and may
   optionally supply a "token-authority" designating a location where
   tokens can be acquired.  The set of "token-types" and the semantic
   requirements for those tokens tracked by an IANA registry.  Taking
   the example of [I-D.ietf-acme-service-provider], a challenge might
   look as follows:

       HTTP/1.1 200 OK
       Content-Type: application/json
       Link: <https://example.com/acme/some-directory>;rel="directory"

       {
        "status": "pending",

        "identifier": {
           "type": "TNAuthList",
           "value": ["1234-0111"]
         },
         "challenges": [
         {
           "type": "token-01",
           "token-type": "TNAuthList-JWT",
           "token-authority": "https://authority.example.org/authz",
           "url": "https://boulder.example.com/authz/asdf/0"
           "token": "IlirfxKKXAsHtmzK29Pj8A" }
         ],
       }

   Entities receiving this challenge know that they can as a proof
   acquire a JWT token from the designated token authority.  Once the

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   JWT has been acquired, it can be posted back to the URL given by the
   ACME challenge.

       POST /acme/authz/asdf/0 HTTP/1.1
       Host: boulder.example.com
       Content-Type: application/jose+json

        {
         "protected": base64url({
         "alg": "ES256",
         "kid": "https://boulder.example.com/acme/reg/asdf",
         "nonce": "Q_s3MWoqT05TrdkM2MTDcw",
         "url": "https://boulder.example.com/acme/authz/asdf/0"
          }),
         "payload": base64url({
         "TNAuthList-JWT": "evaGxfADs...62jcerQ"
            }),
         "signature": "5wUrDI3eAaV4wl2Rfj3aC0Pp--XB3t4YYuNgacv_D3U"
        }

   Because the assignment of resources can change over time,
   demonstrations of effective control must be regularly refreshed --
   though again, because of the diverse capabilities of the devices
   involved, different schemes for refreshing the challenge, ones that
   require less direct user supervision, may be available to some
   devices and not others.

3.1.  Token Type Requirements

   [TBD.]

4.  Acknowledgments

   We would like to thank you for your contributions to this problem
   statement and framework.

5.  IANA Considerations

   Future versions of this specification will include registrations for
   the ACME Challenge type registries here.  It will also create a
   registry for "token types" as used in these challenges.

6.  Security Considerations

   TBD.

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7.  Informative References

   [I-D.ietf-acme-acme]
              Barnes, R., Hoffman-Andrews, J., and J. Kasten, "Automatic
              Certificate Management Environment (ACME)", draft-ietf-
              acme-acme-07 (work in progress), June 2017.

   [I-D.ietf-acme-service-provider]
              Barnes, M. and C. Wendt, "ACME Identifiers and Challenges
              for VoIP Service Providers", draft-ietf-acme-service-
              provider-01 (work in progress), July 2017.

   [I-D.ietf-acme-star]
              Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T.
              Fossati, "Use of Short-Term, Automatically-Renewed (STAR)
              Certificates to Delegate Authority over Web Sites", draft-
              ietf-acme-star-00 (work in progress), June 2017.

   [I-D.ietf-acme-telephone]
              Peterson, J. and R. Barnes, "ACME Identifiers and
              Challenges for Telephone Numbers", draft-ietf-acme-
              telephone-00 (work in progress), July 2017.

   [I-D.ietf-modern-problem-framework]
              Peterson, J. and T. McGarry, "Modern Problem Statement,
              Use Cases, and Framework", draft-ietf-modern-problem-
              framework-03 (work in progress), July 2017.

   [I-D.ietf-stir-certificates]
              Peterson, J. and S. Turner, "Secure Telephone Identity
              Credentials: Certificates", draft-ietf-stir-
              certificates-14 (work in progress), May 2017.

   [I-D.ietf-stir-passport]
              Wendt, C. and J. Peterson, "Personal Assertion Token
              (PASSporT)", draft-ietf-stir-passport-11 (work in
              progress), February 2017.

   [I-D.ietf-stir-rfc4474bis]
              Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-16
              (work in progress), February 2017.

   [I-D.rescorla-stir-fallback]
              Rescorla, E. and J. Peterson, "STIR Out of Band
              Architecture and Use Cases", draft-rescorla-stir-
              fallback-02 (work in progress), June 2017.

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   [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>.

   [RFC7340]  Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
              Telephone Identity Problem Statement and Requirements",
              RFC 7340, DOI 10.17487/RFC7340, September 2014,
              <https://www.rfc-editor.org/info/rfc7340>.

Author's Address

   Jon Peterson
   Neustar, Inc.
   1800 Sutter St Suite 570
   Concord, CA  94520
   US

   Email: jon.peterson@neustar.biz

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