Subject: [P2PSIP] Mirja Kühlewind's No Objection on draft-ietf-p2psip-share-09: (with COMMENT)

From: "Mirja Kuehlewind" <[email-masked]>
Date: Mon, 31 Oct 2016 07:06:56 -0700

Mirja Kühlewind has entered the following ballot position for
draft-ietf-p2psip-share-09: No Objection

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COMMENT:
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Quick questions on sec 6.3. (Validating Write Access through an ACL):
Do I really need to validate the authorization chain in the ACL every
time I give access to a resource? Wouldn't I rather validate the ACL when
it's modified and then simply assume that it is sufficient that I have an
entry in the ACL to provide access?

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From: "Thomas C. Schmidt" <[email-masked]>
Date: Mon, 31 Oct 2016 15:37:49 +0100

Hi Mirja,

you are right in the sense that (a) if all previous evaluations have 
been performed without a failure, and (b) if no revocation occurred (or 
(c) a previous revocation has cleaned up all further delegation 
entries), then the write procedure can rely on the single delegation 
entry that matches the current user name of the writer.

However, this includes several "ifs". For instance, if cleanup of the 
delegation list has not been completed at the time of granting write 
access, errors in the trust chain may occur. This could introduce 
unwanted attack surface.

Our rationale behind designing this complete, self-contained procedure 
was (a) writing an ACL list is not a frequent operation (so complexity 
is not the major concern), and (b) keeping all operations simple, 
robust, and of minimal dependence w.r.t. each other.

That's why it's like that.

Cheers,
  Thomas

-- 

Prof. Dr. Thomas C. Schmidt
° Hamburg University of Applied Sciences                   Berliner Tor 7 °
° Dept. Informatik, Internet Technologies Group    20099 Hamburg, Germany °
° http://www.haw-hamburg.de/inet                   Fon: +49-40-42875-8452 °
° http://www.informatik.haw-hamburg.de/~schmidt    Fax: +49-40-42875-8409 °