CDNI Metadata for Delegated Credentials

Abstract

The delivery of content over HTTPS involving multiple CDNs raises credential management issues. This document defines metadata in CDNI Control and Metadata interface to setup HTTPS delegation using Delegated Credentials from an Upstream CDN (uCDN) to a Downstream CDN (dCDN).¶

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 defines the CDNI Metadata interface to setup HTTPS delegation using Delegated Credentials between an upstream CDN (uCDN) and downstream CDN (dCDN). 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 metadata for handling Delegated Credentials in CDNI. Section 5 addresses IANA registry for delegation methods.¶

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 Delegated Credentials as a delegation method as defined in [I-D.ietf-tls-subcerts].¶

4. DelegatedCredentialsMethod metadata

This section defines the DelegatedCredentialsMethod metadata related to the use of Delegated credentials as presented in [I-D.ietf-tls-subcerts]¶

Client                  dCDN                 uCDN                 Content
   |                     |                     |                  Provider
   |                     |                     |                     |
   |                     |                     | Certificate         |
   |                     |                     |<--------------------|
   |                     | GET Metadata incl. Delegated Cred. method obj.
   |                     +-------------------->|                     |
   |                     | 200 OK + Metadata   |                     |
   |                     |<--------------------+                     |
   |                     | Get Delegated Credentials                 |
   |                     +-------------------->|                     |
   |                     | Delegated Credentials                     |
   |                     |<--------------------+                     |
   | Client Hello + Delegated credentials support                    |
   +-------------------->|                     |                     |
   | Server Hello + delegated credentials      |                     |
   |<--------------------|                     |                     |
   | Certificate         |                     |                     |
   |<--------------------|                     |                     |
   | TLS ServerKeyExchange                     |                     |
   |<--------------------|                     |                     |
   | TLS ClientKeyExchange                     |                     |
   |<--------------------|                     |                     |
   | TLS Finished        |                     |                     |
   |<--------------------|                     |                     |
   |                     |                     |                     |

   Figure 2: Example call-flow of Delegated credentials in CDNI

As expressed in [I-D.ietf-tls-subcerts], when an origin has set a delegation to a downstream entity such as a downstream CDN (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.¶

Below we define metadata related to DelegatedCredentialsMethod. Please refer to [I-D.ietf-cdni-interfaces-https-delegation] for details on the use of the following metadata.¶

Property: credentials-delegating-entity¶

• Description: Endpoint ID (IP) of the delegating Entity (uCDN). Endpoint type defined in RFC8006, Section 4.3.3.¶
• Type: Endpoint¶
• Mandatory-to-Specify: Yes¶

Property: credential-recipient-entity¶

• Description: Endpoint ID (IP) of the delegated entity (dCDN). Endpoint type is defined in RFC8006, Section 4.3.3.¶
• Type: Endpoint¶
• 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.¶
• Type: Integer¶
• Mandatory-to-Specify: Yes¶

5. 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.DelegatedCredentialsMethod | RFCthis       |
+-------------------------------+---------------+

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

6. References