CDNI extensions for HTTPS delegation
draft-ietf-cdni-interfaces-https-delegation-06

Document Type Active Internet-Draft (cdni WG)
Authors Frédéric Fieau  , Stephan Emile  , Sanjay Mishra 
Last updated 2021-09-10
Replaces draft-fieau-cdni-interfaces-https-delegation
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CDNI Working Group                                       F.F. Fieau, Ed.
Internet-Draft                                              E.S. Stephan
Intended status: Standards Track                                  Orange
Expires: 14 March 2022                                       S.M. Mishra
                                                                 Verizon
                                                       10 September 2021

                  CDNI extensions for HTTPS delegation
             draft-ietf-cdni-interfaces-https-delegation-06

Abstract

   The delivery of content over HTTPS involving multiple CDNs raises
   credential management issues.  This document proposes extensions in
   CDNI Control and Metadata interfaces to setup HTTPS delegation from
   an Upstream CDN (uCDN) to a Downstream CDN (dCDN).

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
   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 14 March 2022.

Copyright Notice

   Copyright (c) 2021 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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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Known delegation methods  . . . . . . . . . . . . . . . . . .   3
   4.  Extension to CDNI FCI . . . . . . . . . . . . . . . . . . . .   3
   5.  Extending the CDNI metadata model . . . . . . . . . . . . . .   4
     5.1.  Extension to HostMetadata object  . . . . . . . . . . . .   4
     5.2.  Extension to PathMetadata object  . . . . . . . . . . . .   5
   6.  AcmeStarDelegationMethod object . . . . . . . . . . . . . . .   6
   7.  Metadata Simple Data Type Descriptions  . . . . . . . . . . .   8
     7.1.  Periodicity . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  CDNI MI AcmeStarDelegationMethod Payload Type . . . . . .   9
   9.  Security considerations . . . . . . . . . . . . . . . . . . .   9
   10. Comments and questions  . . . . . . . . . . . . . . . . . . .   9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     11.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Content delivery over HTTPS using one or more CDNs along the path
   requires credential management.  This specifically applies when an
   entity delegates delivery of encrypted content to another trusted
   entity.

   Several delegation methods are currently proposed within different
   IETF working groups.  They specify different methods for provisioning
   HTTPS delivery credentials.

   This document extends the CDNI Metadata interface to setup HTTPS
   delegation between an upstream CDN (uCDN) and downstream CDN (dCDN)
   using the Standardized delegation methods.  Furthermore, it includes
   a proposal of IANA registry to enable adding of new methods.

   Section 2 is about terminology used in this document.  Section 3
   presents delegation methods specified at the IETF.  Section 4
   addresses the extension for handling HTTPS delegation in CDNI.
   Section 5 describes simple data types.  Section 6 addresses IANA
   registry for delegation methods.  Section 7 covers the security
   issues.  Section 8 is about comments and questions.

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2.  Terminology

   This document uses terminology from CDNI framework documents such as:
   CDNI framework document [RFC7336], CDNI requirements [RFC7337] and
   CDNI interface specifications documents: CDNI Metadata interface
   [RFC8006] and CDNI Control interface / Triggers [RFC8007].

3.  Known delegation methods

   There are currently Internet drafts within the TLS and ACME working
   groups adopted to handle delegation of HTTPS delivery between
   entities.

   This Internet Draft (I-D) proposes standardizing HTTPS delegation
   between the CDN entities using CDNI interfaces.

   This document only considers the Short-term, Automatically-Renewed
   (STAR) certificates in Automated Certificate Management
   Environment(ACME) [RFC8739]

   This document allows the extension to other delegation methods.
   Those methods can easily be extended to any further methods in the
   future.

4.  Extension to CDNI FCI

   In order for CDNs to negotiate on which methods are supported, the
   Footprint and Capabilities interface as defined in RFC8008, allows a
   uCDN to send a FCI capability type objects, named
   FCI.SupportedDelegationMethods, to dCDN.

   The following example shows an exemple of the supported delegated
   methods capability object serialization for a CDN that supports STAR
   delegation method.

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        {
        "capabilities": [
          {
            "capability-type": "FCI.SupportedDelegationMethods",
            "capability-value": {
              "delegation-methods": [
                       "AcmeStarDelegationDelegationMethod",
                       "... Other delegation methods ..."
              ]
            }
            "footprints": [
              <Footprint objects>
            ]
          }
        ]
      }

5.  Extending the CDNI metadata model

   This section defines a CDNI extension to the current Metadata
   interface model that allows bootstrapping delegation methods between
   a uCDN and a delegate dCDN.

5.1.  Extension to HostMetadata object

   This extension reuses HostMetadata object, as defined in [RFC8006],
   and adds new "Delegation methods" objects as specified in the
   following sections.

   The existence of the delegation methods in a HostMetaData Object
   shall enable the use of one of this methods, chosen by the delegating
   entity.  The delegation method will be activated for the set of Host
   defined in the HostMatch.  See Section 6 for more details about
   delegation methods metadata specification.

   Example:

   The HostMatch object can reference a host metadata that points at the
   delegation information.  Delegation metadata are added to
   HostMetadata object.

   Below shows both HostMatch and HostMetadata objects related to a
   host, for example, here is a HostMatch object referencing
   "video.example.com":

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   HostMatch:
      {
        "host": "video.example.com",
        "host-metadata": {
          "type": "MI.HostMetadata",
          "href": "https://metadata.ucdn.example/host1234"
        }
      }

   Following the example above, the HostMetadata can be modeled
   for ACMEStarDelegationMethod as:

           {
       "hostmetadata": [
               {
           "generic-metadata-type": "MI.AcmeStarDelegationMethod",
           "generic-metadata-value": {
              "star-proxy": "10.2.2.2",
              "acme-server" : "10.2.3.3",
              "credentials-location-uri": “www.ucdn.com/credentials",
              "periodicity": 36000,
              "CSR-template": Json/Text of the CSR template (see 4.2)
               }}]
           }

   This extension allows to explicitly indicate support for a given
   method.  Therefore, the presence (or lack thereof) of an
   AcmeStarDelegationMethod, and/or further delegation methods, implies
   support (or lack thereof) for the given method.

5.2.  Extension to PathMetadata object

   This extension reuses PathMetadata object, as defined in [RFC8006],
   and adds new "Delegation methods" objects as specified in the
   following sections.

   This allows to explicitly indicate support for a given method.
   Therefore, the presence (or lack thereof) of an
   AcmeStarDelegationMethod, and/or further delegation methods, implies
   support (or lack thereof) for the given method.

   Example:

   The PathMatch object can reference a path-metadata that points at the
   delegation information.  Delegation metadata are added to
   PathMetaData object.

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   Below shows both PathMatch and PathMetaData objects related to a
   path, for example, here /movies/* located at
   https://metadata.ucdn.example/video.example.com/movies

 PathMatch:
 {
   "path-pattern": {
    "pattern": "/movies/*",
    "case-sensitive": true
   },
   "path-metadata": {
    "type": "MI.PathMetadata",
    "href": "https://metadata.ucdn.example/video.example.com/movies"
   }
 }

 Following the example above, the PathMetadata can be modeled
 for ACMEStarDelegationMethod as:

 {
  PathMetadata:
  {
   "metadata": [
     {
         "generic-metadata-type": "MI.AcmeStarDelegationMethod",
         "generic-metadata-value": {
         "star-proxy": "10.2.2.2",
         "acme-server" : "10.2.3.3",
         "credentials-location-uri": “www.ucdn.com/credentials",
         "periodicity": 36000,
         "CSR-template": Json/Text of the CSR template (see section 4.2)
         }}]
  }
 }

   The existence of the "MI.AcmeStarDelegationMethod" object in a
   PathMetaData Object shall enable the use of one of the
   AcmeStarDelegation Methods, chosen by the delegating entity.  The
   delegation method will be activated for the set of Path defined in
   the PathMatch.  See Section 6 for more details about delegation
   methods metadata specification.

6.  AcmeStarDelegationMethod object

   This section defines the AcmeStarDelegationMethod object which
   describes metadata related to the use of ACME/STAR API presented in
   [RFC8739]

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   As expressed in [RFC8739], when an origin has set a delegation to a
   specific domain (i.e. dCDN), the dCDN should present to the end-user
   client, a short-term certificate bound to the master certificate.

dCDN                  uCDN             Content Provider           CA
 |              ACME/STAR proxy        ACME/STAR client    ACME/STAR srv
 |                     |                     |                     |
 | 1. GET Metadata incl. Delegation Method object with CSR template|
 +-------------------->|                     |                     |
 | 200 OK + Metadata incl. CSR template [CDNI]                     |
 |<--------------------+                     |                     |
 | 2. Request delegation: video.dcdn.example + dCDN public key     |
 +-------------------->|                     |                     |
 |                     | 3. Request STAR Cert + dCDN public key    |
 |                     +-------------------->| 4. Request STAR cert|
 |                     |                     |    + Pubkey         |
 |                     |                     |-------------------->|
 |                     |                     | 5. STAR certificate |
 |                     | 6. STAR certificate |<--------------------|
 | 7. STAR certificate |<--------------------+                     |
 +<--------------------|                     |                     |
 |                     |                     |                     |
 | 8. Retrieve STAR certificate (credential-location-uri)          |
 +---------------------------------------------------------------->|
 |                     |                     |         9. renew +--|
 |                     |                     |            cert  |  |
 | 10. Star certificate                      |                  +->|
 |<----------------------------------------------------------------+
 |  ...                |                     |                     |

Figure 1: Example call-flow of STAR delegation in CDNI showing 2 levels
of delegation

   Property: star-proxy

      Description: Used to advertise the STAR Proxy to the dCDN.
      Endpoint type defined in RFC8006, Section 4.3.3.

      Type: Endpoint

      Mandatory-to-Specify: Yes

   Property: acme-server

      Description: used to advertise the ACME server to the dCDN.
      Endpoint type is defined in RFC8006, Section 4.3.3.

      Type: Endpoint

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      Mandatory-to-Specify: Yes

   Property: credentials-location-uri

      Description: expresses the location of the credentials to be
      fetched by the dCDN.  Link type is as defined in RFC8006,
      Section 4.3.1.

      Type: Link

      Mandatory-to-Specify: Yes

   Property: periodicity

      Description: expresses the credentials renewal periodicity.  See
      Section 7.1.

      Type: Periodicity

      Mandatory-to-Specify: Yes

   Property: CSR-template

      Description: The CSR template must be included in the metadata
      when dealing with AcmeStarDelegation Methods.  It shall follow the
      description in [RFC8739] section 3.  It should be included in
      JSON/text format.

      Type: JSON

      Mandatory-to-Specify: Yes

7.  Metadata Simple Data Type Descriptions

   This section describes the simple data types that are used for
   properties for objects in this document.

7.1.  Periodicity

   A time value expressed in seconds to indicate a periodicity.

   Type: Integer

8.  IANA considerations

   This document requests the registration of the following entries
   under the "CDNI Payload Types" registry hosted by IANA regarding
   "CDNI delegation":

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   +-------------------------------+---------------+
   | Payload Type                  | Specification |
   +-------------------------------+---------------+
   | MI.AcmeStarDelegationMethod   | RFCthis       |
   +-------------------------------+---------------+

   [RFC Editor: Please replace RFCthis with the published RFC number for
      this document.]

8.1.  CDNI MI AcmeStarDelegationMethod Payload Type

   Purpose: The purpose of this Payload Type is to distinguish
   AcmeStarDelegationMethod MI objects (and any associated capability
   advertisement)

   Interface: MI/FCI

   Encoding: see Section 4.2.1

9.  Security considerations

   Extensions proposed here do not alter nor change Security
   Considerations as outlined in the CDNI Metadata and Footprint and
   Capabilities RFCs [RFC8006].

10.  Comments and questions

   Should dCDN be visible from the Content Provider or not?  This would
   lead to different solutions to handle delegation towards the CP.  In
   most cases, the dCDNs should never be visible to the CP, in order to
   reduce the burden of certificates generation for dCDN.

11.  References

11.1.  Normative References

   [RFC8006]  Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
              "Content Delivery Network Interconnection (CDNI)
              Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
              <https://www.rfc-editor.org/info/rfc8006>.

   [RFC8007]  Murray, R. and B. Niven-Jenkins, "Content Delivery Network
              Interconnection (CDNI) Control Interface / Triggers",
              RFC 8007, DOI 10.17487/RFC8007, December 2016,
              <https://www.rfc-editor.org/info/rfc8007>.

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   [RFC8739]  Sheffer, Y., Lopez, D., Gonzalez de Dios, O., Pastor
              Perales, A., and T. Fossati, "Support for Short-Term,
              Automatically Renewed (STAR) Certificates in the Automated
              Certificate Management Environment (ACME)", RFC 8739,
              DOI 10.17487/RFC8739, March 2020,
              <https://www.rfc-editor.org/info/rfc8739>.

11.2.  Informative References

   [RFC7336]  Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
              "Framework for Content Distribution Network
              Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
              August 2014, <https://www.rfc-editor.org/info/rfc7336>.

   [RFC7337]  Leung, K., Ed. and Y. Lee, Ed., "Content Distribution
              Network Interconnection (CDNI) Requirements", RFC 7337,
              DOI 10.17487/RFC7337, August 2014,
              <https://www.rfc-editor.org/info/rfc7337>.

Authors' Addresses

   Frederic Fieau (editor)
   Orange
   40-48, avenue de la Republique
   92320 Chatillon
   France

   Email: frederic.fieau@orange.com

   Emile Stephan
   Orange
   2, avenue Pierre Marzin
   22300 Lannion
   France

   Email: emile.stephan@orange.com

   Sanjay Mishra
   Verizon
   13100 Columbia Pike
   Silver Spring,  MD 20904
   United States of America

   Email: sanjay.mishra@verizon.com

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