Re: [conex] Stephen Farrell's No Objection on draft-ietf-conex-destopt-09: (with COMMENT)

Bob Briscoe <> Mon, 05 October 2015 23:43 UTC

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From: Bob Briscoe <>
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Date: Tue, 6 Oct 2015 00:43:10 +0100
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Subject: Re: [conex] Stephen Farrell's No Objection on draft-ietf-conex-destopt-09: (with COMMENT)
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On 02/10/15 09:52, Stephen Farrell wrote:
> Hi Bob,
> Those all sound like pretty good changes except perhaps for...
> On 01/10/15 23:06, Bob Briscoe wrote:
>> [Proposed]
>> A network-based attacker could alter ConEx information to fool an audit
>> function in a downstream network into discarding packets. An attack on
>> one network from another by changing an immutable field can be traced,
>> so it would be unlikely given network operators care about their
>> reputation.
> If the attack is carried out by a compromised node then the goals
> of the rightful owner of that node aren't relevant.
Yes, I know. I was trying not to side-track too much into a whole 
treatise on all the more damaging and less traceable attacks that become 
possible if a network node is compromised (e.g. the TTL expiry attack I 
mentioned in the email, but not in proposed draft text).

Perhaps the solution is to say less rather than more, and not mention 
operator reputation, given other attacks are more fruitful whether the 
attacker is the operator or not. How about this:

[Proposal #2]
A network-based attacker could alter ConEx information to fool an audit
function in a downstream network into discarding packets. However,
otherexisting attacks from one network on another such a TTL expiry
attacks are more damaging (because ConEx audit discards silently) and
less traceable (because TTL is meant to change, whereas CDO is not).

Then the following para can still pick up on the traceability aspect.
>> Nonetheless, if ConEx information was being altered within a
>> network, IPsec AH or other more stealthy e2e integrity checks could be
>> useful tools to help pin-point the attack location.
> I'd omit "more stealthy" unless you want to add a reference. (I
> guess that'd be to your Phd thesis and why not include that.)
I'll leave the authors to decide - a ref to my S.12.1.4 of my thesis at 
this point would work.


> Cheers,
> S.

Bob Briscoe