Re: [tcpm] comments on draft-ietf-tcpm-icmp-attacks-05

Fernando Gont <fernando@gont.com.ar> Mon, 15 June 2009 02:16 UTC

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Date: Sun, 14 Jun 2009 23:16:48 -0300
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Cc: "tcpm@ietf.org" <tcpm@ietf.org>, Fernando Gont <fernando.gont@gmail.com>
Subject: Re: [tcpm] comments on draft-ietf-tcpm-icmp-attacks-05
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Joe Touch wrote:

>>> 5) (general) Section 5.1, last paragraph, it
>>> seems like we should be mentioning TCP-AO as
>>> well here, though I don't think it changes any
>>> part of the claim.
>> Agreed. Maybe this is also an indication that TCP-AO *should* change
>> something in this respect!
> 
> TCP-AO already addresses ICMP attacks in the security considerations
> section, and requires there to be a way to disable reaction to ICMPs.
> Like IPsec, though, we don't make a-priori assessments as to whether
> ICMPs should be blocked or not on connections on which TCP-AO (or IPsec)
> is used.

IIRC, the motivation for the TCP MD5 option was to mitigate RST-based
reset attacks. Does it make any sense to have the option and still even
consider reacting to ICMP error messages?

Reaction to ICMP "frag needed" is probably a little more difficult to
assess (for obvious reasons), but reaction to ICMP hard errors is, IMO,
a no-brainer, and I believe should default to "SHOULD NOT abort
connections".

Kind regards,
-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@acm.org
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