Internet-Draft CDNI extensions for HTTPS delegation September 2021
Fieau, et al. Expires 14 March 2022 [Page]
Workgroup:
CDNI Working Group
Internet-Draft:
draft-ietf-cdni-interfaces-https-delegation-06
Published:
Intended Status:
Standards Track
Expires:
Authors:
F.F. Fieau, Ed.
Orange
E.S. Stephan
Orange
S.M. Mishra
Verizon

CDNI extensions for HTTPS delegation

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 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 14 March 2022.

Table of Contents

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.

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.


     {
     "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":


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.

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]

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

Property: acme-server

Property: credentials-location-uri

Property: periodicity

Property: CSR-template

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":


+-------------------------------+---------------+
| 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, , <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, , <https://www.rfc-editor.org/info/rfc8007>.
[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, , <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, , <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, , <https://www.rfc-editor.org/info/rfc7337>.

Authors' Addresses

Frederic Fieau (editor)
Orange
40-48, avenue de la Republique
92320 Chatillon
France
Emile Stephan
Orange
2, avenue Pierre Marzin
22300 Lannion
France
Sanjay Mishra
Verizon
13100 Columbia Pike
Silver Spring, MD 20904
United States of America