Re: [CDNi] I-D Action: draft-ietf-cdni-uri-signing-12.txt

["Kent Leung (kleung)" <[e-mail]>]

Hi Ben. Thanks for your review comments.  See my response to some of them below.





From: CDNi [mailto:[e-mail]] On Behalf Of Ben Niven-Jenkins
Sent: Tuesday, July 4, 2017 3:59 AM
To: Phil Sorber <[e-mail]>
Cc: [e-mail]
Subject: Re: [CDNi] I-D Action: draft-ietf-cdni-uri-signing-12.txt

Hi Phil & URI Signing authors,

I read the latest draft (-12) and below are some questions / thoughts, in no particular order, that occurred to me while reading the document.

* Why support both symmetric & asymmetric keys? What is the advantage to having both options versus just picking one option (probably asymmetric keys as they work for all use cases)?

KL> There are pros and cons of using either asymmetric keys vs symmetric key. Key distribution limitations and relationships between CSP and CDNs are factors. So I think supporting both allows flexibility for deployments of URI signing. Existing URI signing proprietary implementations typically support both already.


* How are the keys distributed between CDNs? I don’t see a property in the UriSigning Metadata object that would include (or link to) the keys (I’m assuming you need to support distribution of at least 2 keys to support key rotation)?

KL> Key distribution is out of scope. I noticed following text was dropped when method converted to JWT. We can put this back in CDNI Overview section, where the asymmetric and symmetric key methods are mentioned.

“Two types of keys can be used for URI Signing: asymmetric keys and
   symmetric keys.  Asymmetric keys are based on a public/private key
   pair mechanism and always contain a private key only known to the
   entity signing the URI (either CSP or uCDN) and a public key for the
   verification of the Signed URI.  With symmetric keys, the same key is
   used by both the signing entity for signing the URI as well as by the
   validating entity for validating the Signed URI.  Regardless of the
   type of keys used, the validating entity has to obtain the key
   (either the public or the symmetric key).  There are very different
   requirements for key distribution (out of scope of this document)
   with asymmetric keys and with symmetric keys.  Key distribution for
   symmetric keys requires confidentiality to prevent another party from
   getting access to the key, since it could then generate valid Signed
   URIs for unauthorized requests.  Key distribution for asymmetric keys
   does not require confidentiality since public keys can typically be
   distributed openly (because they cannot be used for URI signing) and
   private keys are kept by the URI signing function.”


* How does a uCDN know whether it is OK/safe/within policy to re-distribute symmetric keys to a dCDN?

KL> See above.

* In the case of Signed Token chains, how does a CDN obtain the keys required to sign the new tokens in the chain as it generates them?

KL> See above.

Kent


* Section 3.3.1 I think needs to be more explicit, I don’t know how one could communicate a token chain via the query string as specified in the document, as there is no “back channel” for the CDN to communicate the next token in the chain to the UA.

HTH
Ben

On 25 Jun 2017, at 21:19, Phil Sorber <[e-mail]<mailto:[e-mail]>> wrote:

Really hoping to get some feedback on this at the meeting in Prague. It's got all the changes that have been discussed so I'm not aware of any more substantive changes needed. However, lots of editorial nits I suspect.
Thanks.

On Sun, Jun 25, 2017 at 2:12 PM <[e-mail]<mailto:[e-mail]>> wrote:

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Content Delivery Networks Interconnection of the IETF.

        Title           : URI Signing for CDN Interconnection (CDNI)
        Authors         : Ray van Brandenburg
                          Kent Leung
                          Phil Sorber
        Filename        : draft-ietf-cdni-uri-signing-12.txt
        Pages           : 35
        Date            : 2017-06-25

Abstract:
   This document describes how the concept of URI signing supports the
   content access control requirements of CDNI and proposes a URI
   signing method as a JSON Web Token (JWT) [RFC7519] profile.

   The proposed URI signing method specifies the information needed to
   be included in the URI to transmit the signed JWT as well as the
   claims needed by the signed JWT to authorize a UA.  The mechanism
   described can be used both in CDNI and single CDN scenarios.


The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-cdni-uri-signing/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-ietf-cdni-uri-signing-12
https://datatracker.ietf.org/doc/html/draft-ietf-cdni-uri-signing-12

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-cdni-uri-signing-12


Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org<http://tools.ietf.org/>.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

_______________________________________________
CDNi mailing list
[e-mail]<mailto:[e-mail]>
https://www.ietf.org/mailman/listinfo/cdni
_______________________________________________
CDNi mailing list
[e-mail]<mailto:[e-mail]>
https://www.ietf.org/mailman/listinfo/cdni