[secdir] Secdir review of draft-ietf-core-observe-14

[Dorothy Gellert <[e-mail]>]

I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the IESG.
These comments were written primarily for the benefit of the security
area directors. Document editors and WG chairs should treat these
comments just like any other last call comments.

This Standards Track draft is a best effort protocol extension to CoAP to enable clients to retrieve a representation of a resource and keep this representation updated by its server for a period of time.

The security considerations section does exist and discloses the following threats and suggests ways to mitigate these attacks.

- an increase in amplification attacks, and requires the server to limit notifications without client authentication.

- acknowledgements may be spoofed if confirmable messages are predictable.

- server may want access control to prevent resource exhaustion attacks,

- intermediaries may create loops..

Section 1.3, describes 2 issues where a client might be assuming an old state. This issue could be considered a security threat depending on the sensitivity of that resource.  You might want to flag this also in the security considerations section.

This protocol is intended to be best effort only, as noted in the abstract section.    This should be also emphasized in the security section.

In general, very nice thorough analysis of all the race conditions inherent in a best effort only protocol syncing state between client and server.

As an editorial comment, please expand the first occurrence of CoAP

Best Regards,
Dorothy Gellert
Silver Spring Networks
Director, Standards and Technology
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