Re: [Dots] draft-ietf-dots-filter-control: acl updates

["Konda, Tirumaleswar Reddy" <[e-mail]>]

I don’t think approach (1) is a good idea because of out of order delivery of packets. Further, the anti-relay detection technique in DTLS uses sliding windows procedure. An MITM can possibility cache and drop the packets from the client, and replay the cached packets that fall within the sliding window. For instance in the below example, the server could receive packets in the order T0, T4, T1, T2.

Monotonically increasing ‘mid’ is the only defense against this mechanism, and I don’t think the signal channel draft needs any update.

Cheers,
-Tiru

From: Dots <[e-mail]> On Behalf Of [e-mail]
Sent: Tuesday, May 14, 2019 8:14 PM
To: [e-mail]
Subject: [Dots] draft-ietf-dots-filter-control: acl updates


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________________________________
Hi all,

The current version of the draft allows to include acl attributes in requests with new or existing ‘mid’s. By “existing mid’, we meant an existing request which does not include acl attributes when the request was initially created. For such requests, the activation-type of the same acl can be changed as the attack evolve or even control other ACLs. This is supposed to be covered by this text:

   When acl-* attributes are to be
   included in a mitigation request with an existing 'mid', the DOTS
   client MUST repeat all the other parameters as sent in the original
   mitigation request (i.e., having that 'mid') apart from a possible
   change to the lifetime parameter value.

For example:
T0: R(mid)
T1: R(mid, acl1, activation-type=value1)
T2: R(mid, acl2, activation-type=value2)
T3: R(mid, acl1, activation-type=value2)
T4: R(mid)
...

Now, if acl attributes are included in a request with a new mid, we need to specify how activation-type (and acl-list in general) can be updated. We do have two options:


  1.  Update the draft with this NEW text:


   If 'acl-list', 'acl-name', and 'activation-type' attributes are

   included in the initial mitigation request (that is, a mitigation

   request with a new 'mid'), the DOTS client may update the

   'acl-list' as an active attack evolves.  To do so, the DOTS

   client MUST repeat all the other parameters as sent in the original

   mitigation request apart from a possible change to the 'acl-list’

   and the lifetime parameter values.

   And the signal channel spec as follows:


   For a mitigation request to continue beyond the initial negotiated

   lifetime, the DOTS client has to refresh the current mitigation

   request by sending a new PUT request..  This PUT request MUST use the

   same 'mid' value, and MUST repeat all the other parameters as sent in

   the original mitigation request apart from a possible change to the

   lifetime parameter value or other changes to attributes defined in future extensions.

                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For example:
T0: R(mid, acl1, activation-type=value1)
T1: R(mid, acl2, activation-type=value2)
T2: R(mid, acl1, activation-type=value2)
..



  1.  Require a new mid each time a client has to insert acl attributes.

For example:
T0: R(mid0)
T1: R(mid1, acl1, activation-type=value1)
T2: R(mid2, acl2, activation-type=value2)
T3: R(mid3, acl1, activation-type=value2)
...


Thoughts?

Cheers,
Med