CDNI Working Group F. Fieau, Ed.
Internet-Draft E. Stephan
Intended status: Standards Track Orange
Expires: March 21, 2019 S. Mishra
September 17, 2018

CDNI extensions for HTTPS delegation


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).

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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). Furthermore, it includes a proposal of IANA registry to enable the 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 is about an IANA registry for delegation methods. Section 7 raises the security issues.

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

This I-D proposes standardizing HTTPS delegation between the entities using CDNI interfaces.

This document considers the following two I-D that supports HTTPS delegation:

- Sub-certificates [I-D.ietf-tls-subcerts]

- Short-term certificates in ACME using STAR API [I-D.ietf-acme-star]

4. 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.

4.1. Extension to PathMetadata object

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

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


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

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

Below shows the PathMetaData Object related to /movie/* 
(located at https://metadata.ucdn.example/

    "metadata": [
	     "generic-metadata-type": "MI.TimeWindowACL",
	     "generic-metadata-value": {
		    "times": [{
			    "windows": [
				    "start": "1213948800",
				    "end": "1478047392"
		    "action": "allow",
        "generic-metadata-type": "MI.AcmeStarDelegationMethod",
        "generic-metadata-value": {	
        "starproxy": "",
        "acmeserver" : "",
        "credentialslocationuri": “",
        "periodicity": 36000

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

4.2. Delegation methods

This section defines the delegation methods objects metadata. Those metadata allows bootstrapping a secured delegatioin by providing the dCDN with the needed parameters to set it up.

4.2.1. AcmeStarDelegationMethod object

This section defines the AcmeStarDelegationMethod object which describes metadata related to the use of Acme Star API presented in [I-D.ietf-acme-star]

As expressed in [I-D.ietf-acme-star], 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.

Property: starproxy

Property: acmeserver

Property: credentialslocationuri

Property: periodicity

As an example, AcmeStarDelegationMethod object could express the Acme-Star delegation as the following:

AcmeStarDelegationMethod: {
    "generic-metadata-type": "MI.AcmeStarDelegationMethod",
    "generic-metadata-value": {
        “starproxy”: “”,
        “acmeserver”: “”,
        "credentialslocationuri": “”,
        "periodicity": 36000  

4.2.2. SubcertsDelegationMethod object

This section defines the SubcertsDelegationMethod object which describes metadata related to the use of Subcerts as presented in [I-D.ietf-tls-subcerts]

As expressed in [I-D.ietf-tls-subcerts], when an origin has set a delegation to a specific domain (i.e. dCDN), the dCDN should present the Origin or uCDN certificate or "delegated_credential" during the TLS handshake [RFC8446] to the end-user client application, instead of its own certificate.

Property: credentialsdelegatingentity

Property: credentialrecipiententity

Property: credentialslocationuri

Property: periodicity

As an example, when a uCDN has delegated HTTPS delivery to dCDN, a SubcertsDelegationMethod object can express the SubCerts delegation as the following:

SubcertsDelegationMethod: {
    "generic-metadata-type": "MI.SubcertsDelegationMethod",
    "generic-metadata-value": {
        "credentialsdelegatingentity": “”,
        “credentialsrecepiententity”: “”,
        "credentialslocationuri": “”,
        "periodicity": 36000  

5. Metadata Simple Data Type Descriptions

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

5.1. Periodicity

A time value expressed in seconds to indicate a periodicity.

Type: Integer

6. 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       |
| MI.SubCertDelegationMethod | RFCthis       |

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


6.1. 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

6.2. CDNI MI SubCertsDelegationMethod Payload Type

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

Interface: MI/FCI

Encoding: see Section 4.2.2

7. Security considerations

Extensions proposed here do not change Security Considerations as outlined in the CDNI Metadata and Footprint and Capabilities RFCs [RFC8006].

8. References

8.1. Normative References

[RFC7937] Le Faucheur, F., Bertrand, G., Oprescu, I. and R. Peterkofsky, "Content Distribution Network Interconnection (CDNI) Logging Interface", RFC 7937, DOI 10.17487/RFC7937, August 2016.
[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.
[RFC8007] Murray, R. and B. Niven-Jenkins, "Content Delivery Network Interconnection (CDNI) Control Interface / Triggers", RFC 8007, DOI 10.17487/RFC8007, December 2016.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.

8.2. Informative References

[I-D.ietf-acme-star] Sheffer, Y., Lopez, D., Dios, O., Pastor, A. and T. Fossati, "Support for Short-Term, Automatically-Renewed (STAR) Certificates in Automated Certificate Management Environment (ACME)", Internet-Draft draft-ietf-acme-star-03, March 2018.
[I-D.ietf-tls-subcerts] Barnes, R., Iyengar, S., Sullivan, N. and E. Rescorla, "Delegated Credentials for TLS", Internet-Draft draft-ietf-tls-subcerts-02, August 2018.
[RFC7336] Peterson, L., Davie, B. and R. van Brandenburg, "Framework for Content Distribution Network Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336, August 2014.
[RFC7337] Leung, K. and Y. Lee, "Content Distribution Network Interconnection (CDNI) Requirements", RFC 7337, DOI 10.17487/RFC7337, August 2014.

Authors' Addresses

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