Re: [secdir] [tcpm] SECDIR REVIEW of draft-ietf-tcpm-icmp-attacks-10.txt

"Anantha Ramaiah (ananth)" <ananth@cisco.com> Mon, 15 February 2010 22:30 UTC

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Date: Mon, 15 Feb 2010 14:32:17 -0800
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From: "Anantha Ramaiah (ananth)" <ananth@cisco.com>
To: Fernando Gont <fernando@gont.com.ar>, Phillip Hallam-Baker <hallam@gmail.com>
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Cc: tcpm@ietf.org, secdir@ietf.org
Subject: Re: [secdir] [tcpm] SECDIR REVIEW of draft-ietf-tcpm-icmp-attacks-10.txt
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Some general comments on this discussion inline...


> -----Original Message-----
> From: tcpm-bounces@ietf.org [mailto:tcpm-bounces@ietf.org] On 
> Behalf Of Fernando Gont
> Sent: Monday, February 15, 2010 11:50 AM
> To: Phillip Hallam-Baker
> Cc: tcpm@ietf.org; secdir@ietf.org
> Subject: Re: [tcpm] SECDIR REVIEW of 
> draft-ietf-tcpm-icmp-attacks-10.txt
> 
> Hello, Phillip,
> 
> Thanks so much for your feedback! See my comments inline....
> 
> 
> > The principal security risks considered are service risks. 
> ICMP may be 
> > used to perform certain denial of service and performance downgrade 
> > attacks. As such it probably needs rather more 
> justification than 'we 
> > have always done this' when building critical infrastructures.
> 
> I fully agree. This I-D has been debated in tcpm form... 6 
> years now. It was originally meant for Std track, but somehow 
> ended up heading for Informational. What's in the I-D is what 
> most implementation (all the mainstream ones, at least) do.

That is true. Many implementations already do what is being said in this
ID. 

> 
> So if *I* had to answer why we don't stress that ICMP should 
> be disregarded in many scenarios, etc., I can just say that 
> this is what the WG has converged to.

I think you should put some text to this effect. IMO, we don't have an
overwhelming consensus on whether this document should be informational
or standard. To me, I have no issues making this head towards the PS,
one of the main reasons being it has been well adopted in the internet
today. I also agree that "just being popular" doesn't imply that it
needs to become a standard. In this case it is not only popular, these
mitigations have more pros than cons.

<snip>

> > This argument is
> > almost made on page 15. Some statement giving the case for taking 
> > notice of ICMP messages at all is in order.
> 
> I guess the "statement" that you could get here (tcpm) is 
> "responsiveness". -- with which I'd disagree, for many of the 
> reasons stated in the draft, and because in many other cases 
> it has been argued in this very wg that "tcp is supposed to 
> be robust, it's not optimized for any scenario, etc.".
> 
> Should I craft some text along the lines of "responsiveness"?

That may be a good idea.

> 
> 
> 
> > It might well be that an
> > appropriate control in certain cases would be to turn off ICMP hard 
> > errors and rely on timeouts, I am thinking here of critical 
> > infrastructure applications and communications between 
> hosts running 
> > BGP functions.
> 
> Most (if not all) real-world implementations already do this. 
> We have lived with this behaviour that you describe for the 
> last..mm.. 20 years (or so) with BSDs... and there's no way 
> that BSDs, or Linux, or Cisco, or whoever are going to change 
> back their implementations to e.g.
> "resetting connections in response to ICMP hard errors". For 
> instance, they have issued vulnerability advisories in this respect...

Correct.

Thanks,
-Anantha