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TNAuthList profile of ACME Authority Token
draft-ietf-acme-authority-token-tnauthlist-11

Document Type Active Internet-Draft (acme WG)
Authors Chris Wendt , David Hancock , Mary Barnes , Jon Peterson
Last updated 2022-11-12
Replaces draft-wendt-acme-authority-token-tnauthlist
Stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Formats
Reviews
OPSDIR Last Call Review Incomplete, due 2021-03-16
Stream WG state In WG Last Call
Associated WG milestone
Apr 2020
TNAuthlist extension submitted to IESG
Document shepherd Rich Salz
Shepherd write-up Show Last changed 2020-08-13
IESG IESG state IESG Evaluation::AD Followup
Action Holder
Consensus boilerplate Yes
Telechat date (None)
Has a DISCUSS. Has enough positions to pass once DISCUSS positions are resolved.
Responsible AD Roman Danyliw
Send notices to Rich Salz <rsalz@akamai.com>
IANA IANA review state Version Changed - Review Needed
IANA expert review state Expert Reviews OK
draft-ietf-acme-authority-token-tnauthlist-11
Network Working Group                                           C. Wendt
Internet-Draft                                                Somos Inc.
Intended status: Standards Track                              D. Hancock
Expires: 16 May 2023                                             Comcast
                                                               M. Barnes
                                                             J. Peterson
                                                            Neustar Inc.
                                                        12 November 2022

               TNAuthList profile of ACME Authority Token
             draft-ietf-acme-authority-token-tnauthlist-11

Abstract

   This document defines a profile of the Automated Certificate
   Management Environment (ACME) Authority Token for the automated and
   authorized creation of certificates for VoIP Telephone Providers to
   support Secure Telephony Identity (STI) using the TNAuthList defined
   by STI certificates.

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 https://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 16 May 2023.

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
   and restrictions with respect to this document.  Code Components

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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.  ACME new-order identifiers for TNAuthList . . . . . . . . . .   3
   4.  TNAuthList Identifier Authorization . . . . . . . . . . . . .   5
   5.  TNAuthList Authority Token  . . . . . . . . . . . . . . . . .   7
     5.1.  "iss" claim . . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  "exp" claim . . . . . . . . . . . . . . . . . . . . . . .   7
     5.3.  "jti" claim . . . . . . . . . . . . . . . . . . . . . . .   7
     5.4.  "atc" claim . . . . . . . . . . . . . . . . . . . . . . .   7
     5.5.  Acquiring the token from the Token Authority  . . . . . .   8
     5.6.  Token Authority Responsibilities  . . . . . . . . . . . .  10
     5.7.  Scope of the TNAuthList . . . . . . . . . . . . . . . . .  10
   6.  Validating the TNAuthList Authority Token . . . . . . . . . .  10
   7.  Using ACME-issued Certificates with JSON Web Signature  . . .  11
   8.  Usage Considerations  . . . . . . . . . . . . . . . . . . . .  13
     8.1.  Large number of Non-contiguous TNAuthList values  . . . .  13
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     12.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   [RFC8555] is a mechanism for automating certificate management on the
   Internet.  It enables administrative entities to prove effective
   control over resources like domain names, and automates the process
   of generating and issuing certificates.
   [I-D.ietf-acme-authority-token] extends ACME to provide a general
   method of extending the authority and authorization of entities to
   control a resource via a third party Token Authority beyond the
   Certification Authority (CA).

   This document is a profile document using the Authority Token
   mechanism defined in [I-D.ietf-acme-authority-token].  It is a
   profile that specifically addresses the STIR problem statement
   [RFC7340] which identifies the need for Internet credentials that can
   attest authority for the originator of VoIP calls in order to detect
   impersonation, which is currently an enabler for common attacks
   associated with illegal robocalling, voicemail hacking, and swatting.

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   These credentials are used to sign PASSporTs [RFC8225], which can be
   carried in using protocols such as SIP [RFC8224].  Currently, the
   only defined credentials for this purpose are the certificates
   specified in [RFC8226] using the TNAuthList.  This document defines
   the use of the TNAuthList Authority Token in the ACME challenge to
   proof the authoritative use of the contents of the TNAuthList,
   including a Service Provider Token (SPC), a Telephone Number, or a
   set of telephone numbers or telephone number blocks.

   This document also describes the ability for a telephone authority to
   authorize the creation of CA types of certificates for delegation as
   defined in [RFC9060].

2.  Terminology

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

3.  ACME new-order identifiers for TNAuthList

   In [RFC8555], Section 7 defines the procedure that an ACME client
   uses to order a new certificate from a CA.  The new-order request
   contains an identifier field that specifies the identifier objects
   the order corresponds to.  This draft defines a new type of
   identifier object called TNAuthList.  A TNAuthList identifier
   contains the identity information to be populated in the TN
   Authorization List of the new certificate.  For the TNAuthList
   identifier, the new-order request includes a type set to the string
   "TNAuthList".  The value of the TNAuthList identifier MUST be set to
   the details of the TNAuthList requested.

   The format of the string that represents the TNAuthList MUST be
   constructed using base64url encoding, as per [RFC8555] base64url
   encoding described in Section 5 of [RFC4648] according to the profile
   specified in JSON Web Signature in Section 2 of [RFC7515].  The
   base64url encoding MUST NOT include any padding characters and the
   TNAuthList ASN.1 object MUST encoded using DER encoding rules.

   An example of an ACME order object "identifiers" field containing a
   TNAuthList certificate would look as follows,

    "identifiers": [{"type":"TNAuthList","value":"F83n2a...avn27DN3"}]

   where the "value" object string represents the arbitrary length
   base64url encoded string.

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   A full new-order request would look as follows,

   POST /acme/new-order HTTP/1.1
   Host: example.com
   Content-Type: application/jose+json

   {
     "protected": base64url({
       "alg": "ES256",
       "kid": "https://example.com/acme/acct/evOfKhNU60wg",
       "nonce": "5XJ1L3lEkMG7tR6pA00clA",
       "url": "https://example.com/acme/new-order"
     }),
     "payload": base64url({
       "identifiers": [{"type":"TNAuthList","value":"F83n...n27DN3"}],
       "notBefore": "2021-01-01T00:00:00Z",
       "notAfter": "2021-01-08T00:00:00Z"
     }),
     "signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g"
   }

   On receiving a valid new-order request, the ACME server creates an
   authorization object, [RFC8555] Section 7.1.4, containing the
   challenge that the ACME client must satisfy to demonstrate authority
   for the identifiers specified by the new order (in this case, the
   TNAuthList identifier).  The CA adds the authorization object URL to
   the "authorizations" field of the order object, and returns the order
   object to the ACME client in the body of a 201 (Created) response.

   HTTP/1.1 201 Created
   Content-Type: application/json
   Replay-Nonce: MYAuvOpaoIiywTezizk5vw
   Location: https://example.com/acme/order/1234

   {
     "status": "pending",
     "expires": "2022-01-08T00:00:00Z",

     "notBefore": "2022-01-01T00:00:00Z",
     "notAfter": "2022-01-08T00:00:00Z",
     "identifiers":[{"type":"TNAuthList",
                    "value":"F83n2a...avn27DN3"}],

     "authorizations": [
      "https://example.com/acme/authz/1234"
     ],
     "finalize": "https://example.com/acme/order/1234/finalize"
   }

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4.  TNAuthList Identifier Authorization

   On receiving the new-order response, the ACME client queries the
   referenced authorization object to obtain the challenges for the
   identifier contained in the new-order request as shown in the
   following example request and response.

   POST /acme/authz/1234 HTTP/1.1
       Host: example.com
       Content-Type: application/jose+json

       {
         "protected": base64url({
           "alg": "ES256",
           "kid": " https://example.com/acme/acct/evOfKhNU60wg",
           "nonce": "uQpSjlRb4vQVCjVYAyyUWg",
           "url": "https://example.com/acme/authz/1234"
         }),
         "payload": "",
         "signature": "nuSDISbWG8mMgE7H...QyVUL68yzf3Zawps"
       }

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

   {
     "status": "pending",
     "expires": "2022-01-08T00:00:00Z",

     "identifier": {
       "type:"TNAuthList",
       "value":"F83n2a...avn27DN3"
     },

     "challenges": [
       {
         "type": "tkauth-01",
         "tkauth-type": "atc",
         "token-authority": "https://authority.example.org",
         "url": "https://example.com/acme/chall/prV_B7yEyA4",
         "token": "IlirfxKKXAsHtmzK29Pj8A"
       }
     ]
   }

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   When processing a certificate order containing an identifier of type
   "TNAuthList", a CA uses the Authority Token challenge type of
   "tkauth-01" with a "tkauth-type" of "atc" in
   [I-D.ietf-acme-authority-token] to verify that the requesting ACME
   client has authenticated and authorized control over the requested
   resources represented by the "TNAuthList" value.

   The challenge "token-authority" parameter is only used in cases where
   the VoIP telephone network requires the CA to identify the Token
   Authority.  This is currently not the case for the SHAKEN
   [ATIS-1000080] certificate framework governance, but may be used by
   other frameworks.  If a "token-authority" parameter is present, then
   the ACME client MAY use the "token-authority" value to identify the
   URL representing the Token Authority that will provide the TNAuthList
   Authority Token response to the challenge.  If the "token-authority"
   parameter is not present, then the ACME client MUST identify the
   Token Authority based on locally configured information or local
   policies.

   The ACME client responds to the challenge by posting the TNAuthList
   Authority Token to the challenge URL identified in the returned ACME
   authorization object, an example of which follows.

   POST /acme/chall/prV_B7yEyA4 HTTP/1.1
   Host: boulder.example.com
   Content-Type: application/jose+json

   {
     "protected": base64url({
     "alg": "ES256",
     "kid": "https://example.com/acme/acct/evOfKhNU60wg",
     "nonce": "Q_s3MWoqT05TrdkM2MTDcw",
     "url": "https://boulder.example.com/acme/authz/asdf/0"
     }),
     "payload": base64url({
     "tkauth": "DGyRejmCefe7v4N...vb29HhjjLPSggwiE"
     }),
     "signature": "9cbg5JO1Gf5YLjjz...SpkUfcdPai9uVYYQ"
   }

   The "tkauth" field is defined as a new field in the challenge object
   specific to the tkauth-01 challenge type that should contain the
   TNAuthList Authority Token defined in the next section.

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5.  TNAuthList Authority Token

   The Telephone Number Authority List Authority Token (TNAuthList
   Authority Token) is a profile instance of the ACME Authority Token
   defined in [I-D.ietf-acme-authority-token].

   The TNAuthList Authority Token Protected header MUST comply with the
   Authority Token Protected header as defined in
   [I-D.ietf-acme-authority-token].

   The TNAuthList Authority Token Payload MUST include the mandatory
   claims "exp", "jti", and "atc", and MAY include the optional claims
   defined for the Authority Token detailed in the next subsections.

5.1.  "iss" claim

   The "iss" claim is an optional claim defined in [RFC7519]
   Section 4.1.1.  It can be used as a URL identifying the Token
   Authority that issued the TNAuthList Authority Token beyond the "x5u"
   or other Header claims that identify the location of the certificate
   or certificate chain of the Token Authority used to validate the
   TNAuthList Authority Token.

5.2.  "exp" claim

   The "exp" claim, defined in [RFC7519] Section 4.1.4, MUST be included
   and contains the DateTime value of the ending date and time that the
   TNAuthList Authority Token expires.

5.3.  "jti" claim

   The "jti" claim, defined in [RFC7519] Section 4.1.7, MUST be included
   and contains a unique identifier for this TNAuthList Authority Token
   transaction.

5.4.  "atc" claim

   The "atc" claim MUST be included and is defined in
   [I-D.ietf-acme-authority-token].  It contains a JSON object with the
   following elements:

   *  a "tktype" key with a string value equal to "TNAuthList" to
      represent a TNAuthList profile of the authority token
      [I-D.ietf-acme-authority-token] defined by this document. "tktype"
      is a required key and MUST be included.

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   *  a "tkvalue" key with a string value equal to the base64url
      encoding of the TN Authorization List certificate extension ASN.1
      object using DER encoding rules. "tkvalue" is a required key and
      MUST be included.

   *  a "ca" key with a boolean value set to either true when the
      requested certificate is allowed to be a CA cert for delegation
      uses or false when the requested certificate is not intended to be
      a CA cert, only an end-entity certificate. "ca" is an optional
      key, if not included the "ca" value is considered false by
      default.

   *  a "fingerprint" key is constructed as defined in [RFC8555]
      Section 8.1 corresponding to the computation of the "Thumbprint"
      step using the ACME account key credentials. "fingerprint" is a
      required key and MUST be included.

   An example of the TNAuthList Authority Token is as follows:

   {
     "protected": base64url({
       "typ":"JWT",
       "alg":"ES256",
       "x5u":"https://authority.example.org/cert"
     }),
     "payload": base64url({
       "iss":"https://authority.example.org",
       "exp":1640995200,
       "jti":"id6098364921",
       "atc":{"tktype":"TNAuthList",
         "tkvalue":"F83n2a...avn27DN3",
         "ca":false,
         "fingerprint":"SHA256 56:3E:CF:AE:83:CA:4D:15:B0:29:FF:1B:71:
          D3:BA:B9:19:81:F8:50:9B:DF:4A:D4:39:72:E2:B1:F0:B9:38:E3"}
     }),
     "signature": "9cbg5JO1Gf5YLjjz...SpkUfcdPai9uVYYQ"
   }

5.5.  Acquiring the token from the Token Authority

   Following [I-D.ietf-acme-authority-token] Section 5, the authority
   token should be acquired using a RESTful HTTP POST transaction as
   follows:

     POST /at/account/:id/token HTTP/1.1
     Host: authority.example.org
     Content-Type: application/json

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   The request will pass the account id as a string in the request
   parameter "id".  This string will be managed as an identifier
   specific to the Token Authority's relationship with a communications
   service provider (CSP).  There is assumed to also be a corresponding
   authentication procedure that can be verified for the success of this
   transaction.  For example, an HTTP authorization header containing a
   valid authorization credentials as defined in [RFC7231] Section 14.8.

   The body of the POST request MUST contain a JSON object with key
   value pairs corresponding to values that are requested as the content
   of the claims in the issued token.  As an example, the body SHOULD
   contain a JSON object as follows:

    {
      "tktype":"TNAuthList",
      "tkvalue":"F83n2a...avn27DN3",
      "ca":false,
      "fingerprint":"SHA256 56:3E:CF:AE:83:CA:4D:15:B0:29:FF:1B:71:D3
        :BA:B9:19:81:F8:50:9B:DF:4A:D4:39:72:E2:B1:F0:B9:38:E3"
    }

   The response to the POST request if successful returns a 200 OK with
   a JSON body that contains, at a minimum, the TNAuthList Authority
   Token as a JSON object with a key of "token" and the base64url
   encoded string representing the atc token.  JSON is easily
   extensible, so users of this specification may want to pass other
   pieces of information relevant to a specific application.

   An example successful response would be as follows:

   HTTP/1.1 200 OK
   Content-Type: application/json

   {"token": "DGyRejmCefe7v4N...vb29HhjjLPSggwiE"}

   If the request is not successful, the response should indicate the
   error condition.  Specifically, for the case that the authorization
   credentials are invalid or if the Account ID provided does not exist,
   the response code MUST be 403 - Forbidden.  Other 4xx and 5xx
   responses MUST follow standard [RFC7231] HTTP error condition
   conventions.

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5.6.  Token Authority Responsibilities

   When creating the TNAuthList Authority Token, the Token Authority
   MUST validate that the information contained in the ASN.1 TNAuthList
   accurately represents the service provider code (SPC) or telephone
   number (TN) resources the requesting party is authorized to represent
   based on their pre-established and verified secure relationship
   between the Token Authority and the requesting party.  Note that the
   fingerprint in the token request is not meant to be verified by the
   Token Authority, but rather is meant to be signed as part of the
   token so that the party that requests the token can, as part of the
   challenge response, allow the ACME server to validate the token
   requested and used came from the same party that controls the ACME
   client.

5.7.  Scope of the TNAuthList

   Because this specification specifically involves the TNAuthList
   defined in [RFC8226] which involves SPC, TNBlock, and individual TNs,
   the client may also request an Authority Token with some subset of
   its own authority as the TNAuthList provided in the "tkvalue" element
   in the "atc" JSON object.  Generally, the scope of authority
   representing a communications service provider is represented by a
   particular SPC (e.g. in North America, an operating company number
   (OCN) or service provider identifier (SPID)).  That provider is also
   generally associated, based on number allocations, with a particular
   set of different TN Blocks and/or TNs.  TNAuthList can be constructed
   to define a limited scope of the TNBlocks or TNs either associated
   with an SPC or with the scope of TN Blocks or TNs the client has
   authority over.

   As recommended in [I-D.ietf-acme-authority-token] security
   considerations, an Authority Token can either have a scope that
   attests all of the resources which a client is eligible to receive
   certificates for, or potentially a more limited scope that is
   intended to capture only those resources for which a client will
   receive a certificate from a particular certification authority.  Any
   certification authority that sees an Authority Token can learn
   information about the resources a client can claim.  In cases where
   this incurs a privacy risk, Authority Token scopes should be limited
   to only the resources that will be attested by the requested ACME
   certificate.

6.  Validating the TNAuthList Authority Token

   Upon receiving a response to the challenge, the ACME server MUST
   perform the following steps to determine the validity of the
   response.

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   *  Verify that the value of the "atc" claim is a well-formed JSON
      object containing the mandatory key values.

   *  If there is an "x5u" parameter verify the "x5u" parameter is a
      HTTPS URL with a reference to a certificate representing the
      trusted issuer of authority tokens for the eco-system.

   *  If there is an "x5c" parameter verify the certificate array
      contains a certificate representing the trusted issuer of
      authority tokens for the eco-system.

   *  Verify the TNAuthList Authority Token signature using the public
      key of the certificate referenced by the token's "x5u" or "x5c"
      parameter.

   *  Verify that "atc" claim contains a "tktype" identifier with the
      value "TNAuthList".

   *  Verify that the "atc" claim "tkvalue" identifier contains the
      equivalent base64url encoded TNAuthList certificate extension
      string value as the Identifier specified in the original
      challenge.

   *  Verify that the remaining claims are valid (e.g., verify that
      token has not expired)

   *  Verify that the "atc" claim "fingerprint" is valid and matches the
      account key of the client making the request

   *  Verify that the "atc" claim "ca" identifier boolean corresponds to
      the CA boolean in the Basic Constraints extension in the CSR for
      either CA certificate or end-entity certificate

   If all steps in the token validation process pass, then the ACME
   server MUST set the challenge object "status" to "valid".  If any
   step of the validation process fails, the "status" in the challenge
   object MUST be set to "invalid".

7.  Using ACME-issued Certificates with JSON Web Signature

   JSON Web Signature (JWS, [RFC7515]) objects can include an "x5u"
   header parameter to refer to a certificate that is used to validate
   the JWS signature.  For example, the STIR PASSporT framework
   [RFC8225] uses "x5u" to indicate the STIR certificate used to
   validate the PASSporT JWS object.  The URLs used in "x5u" are
   expected to provide the required certificate in response to a GET
   request, not a POST-as-GET as required for the "certificate" URL in
   the ACME order object.  Thus the current mechanism generally requires

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   the ACME client to download the certificate and host it on a public
   URL to make it accessible to relying parties.  This section defines
   an optional mechanism for the Certificate Authority (CA) to host the
   certificate directly and provide a URL that the ACME client owner can
   directly reference in the "x5u" of their signed PASSporTs.

   As described in Section 7.4 of [RFC8555] when the certificate is
   ready for making a finalize request, the server will return a 200
   (OK) with the updated order object.  In this response, an ACME Server
   can add a newly defined field called "x5u" that can pass this URL to
   the ACME client for usage in generated PASSporTs as a publically
   available URL for PASSporT validation.

   x5u (optional, string):  A URL that can be used to reference the
      certificate in the "x5u" parameter of a JWS object [RFC7515]

   The publishing of the certificates at the new "x5u" URL should follow
   the GET request requirement as mentioned above and should be
   consistent with the timely publication according to the durations of
   the certificate lifecycle.

   The following is an example of the use of "x5u" in the response when
   the certificate status is "valid".

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   HTTP/1.1 200 OK
   Replay-Nonce: CGf81JWBsq8QyIgPCi9Q9X
   Link: <https://example.com/acme/directory>;rel="index"
   Location: https://example.com/acme/order/TOlocE8rfgo

   {
     "status": "valid",
     "expires": "2016-01-20T14:09:07.99Z",

     "notBefore": "2016-01-01T00:00:00Z",
     "notAfter": "2016-01-08T00:00:00Z",

     "identifiers": [
       "type:"TNAuthList",
       "value":"F83n2a...avn27DN3"
     ],

     "authorizations": ["https://sti-ca.com/acme/authz/1234"],

     "finalize": "https://example.com/acme/order/TOlocE8rfgo/finalize",

     "certificate": "https://example.com/acme/cert/mAt3xBGaobw",

     "x5u": "https://example.com/cert-repo/giJI53km23.pem"
   }

8.  Usage Considerations

8.1.  Large number of Non-contiguous TNAuthList values

   There are many scenarios and reasons to have various combinations of
   SPCs, TNs, and TN Ranges.  [RFC8226] has provided a somewhat
   unbounded set of combinations.  It's possible that a complex non-
   contiguous set of telephone numbers are being managed by a CSP.  Best
   practice may be simply to split a set of non-contiguous numbers under
   management into multiple STI certificates to represent the various
   contiguous parts of the greater non-contiguous set of TNs,
   particularly if length of the set of values in identifier object
   grows to be too large.

9.  Security Considerations

   The token represented by this document has the credentials to
   represent the scope of a telephone number, a block of telephone
   numbers, or an entire set of telephone numbers represented by an SPC.
   The creation, transport, and any storage of this token MUST follow
   the strictest of security best practices beyond the recommendations
   of the use of encrypted transport protocols in this document to

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   protect it from getting in the hands of bad actors with illegitimate
   intent to impersonate telephone numbers.

   This document inherits the security properties of
   [I-D.ietf-acme-authority-token].  Implementations should follow the
   best practices identified in [RFC8725].

   This document only specifies SHA256 for the fingerprint hash.
   However, the syntax of the fingerprint object would permit other
   algorithms if, due to concerns about algorithmic agility, a more
   robust algorithm were required at a future time.  Future
   specifications can define new algorithms for the fingerprint object
   as needed.

10.  IANA Considerations

   This document requests the addition of a new identifier object type
   to the "ACME Identifier Types" registry defined in Section 9.7.7 of
   [RFC8555].

                            +------------+-----------+
                            |   Label    | Reference |
                            +------------+-----------+
                            | TNAuthList |  RFCThis  |
                            +------------+-----------+

11.  Acknowledgements

   We would like to thank Richard Barnes and Russ Housley for valuable
   contributions to this document.

12.  References

12.1.  Normative References

   [I-D.ietf-acme-authority-token]
              Peterson, J., Barnes, M., Hancock, D., and C. Wendt, "ACME
              Challenges Using an Authority Token", Work in Progress,
              Internet-Draft, draft-ietf-acme-authority-token-09, 24
              October 2022, <https://www.ietf.org/archive/id/draft-ietf-
              acme-authority-token-09.txt>.

   [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>.

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   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <https://www.rfc-editor.org/info/rfc4648>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [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>.

   [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>.

   [RFC8226]  Peterson, J. and S. Turner, "Secure Telephone Identity
              Credentials: Certificates", RFC 8226,
              DOI 10.17487/RFC8226, February 2018,
              <https://www.rfc-editor.org/info/rfc8226>.

   [RFC8555]  Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
              Kasten, "Automatic Certificate Management Environment
              (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
              <https://www.rfc-editor.org/info/rfc8555>.

   [RFC8725]  Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
              Current Practices", BCP 225, RFC 8725,
              DOI 10.17487/RFC8725, February 2020,
              <https://www.rfc-editor.org/info/rfc8725>.

   [RFC9060]  Peterson, J., "Secure Telephone Identity Revisited (STIR)
              Certificate Delegation", RFC 9060, DOI 10.17487/RFC9060,
              September 2021, <https://www.rfc-editor.org/info/rfc9060>.

12.2.  Informative References

   [ATIS-1000080]
              ATIS/SIP Forum NNI Task Group, "Signature-based Handling
              of Asserted information using toKENs (SHAKEN) Governance
              Model and Certificate Management
              <https://access.atis.org/apps/group_public/
              download.php/32237/ATIS-1000080.pdf>", July 2017.

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   [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>.

   [RFC8224]  Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", RFC 8224,
              DOI 10.17487/RFC8224, February 2018,
              <https://www.rfc-editor.org/info/rfc8224>.

   [RFC8225]  Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
              Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
              <https://www.rfc-editor.org/info/rfc8225>.

Authors' Addresses

   Chris Wendt
   Somos Inc.
   United States of America
   Email: chris-ietf@chriswendt.net

   David Hancock
   Comcast
   United States of America
   Email: davidhancock.ietf@gmail.com

   Mary Barnes
   Neustar Inc.
   United States of America
   Email: mary.ietf.barnes@gmail.com

   Jon Peterson
   Neustar Inc.
   1800 Sutter St Suite 570
   Concord, CA  94520,
   United States of America
   Email: jon.peterson@neustar.biz

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