Re: ICMP PTB spoofing attacks (was: RE: 6MAN: Adoption call on draft-hinden-6man-rfc1981bis-01)

[Fernando Gont <[e-mail]>]

On 02/05/2016 02:46 PM, Templin, Fred L wrote:
> Hi Fred,
> 
>> As soon as I say "there is no such attack", one will materialize, so I won't assert that.  However, I am not aware of attacks in which
>> someone creates ICMP PTBs and sends them to someone else in order to reduce their windows unnecessarily.
> 
> RFC4821 Section 11 (Security Considerations) recognizes the potential for spoofed
> (i.e., inaccurate) ICMP PTB messages and suggests a mitigation (ignore all ICMP PTBs).
> For paths over which any node in the network can inject an inaccurate ICMP PTB
> message, an attack vector exists.

In theory, you can do some basic validation for ICMP messages. However,
in v6, as a result of possible EHs, you may not find any meaningful data
in the ICMP payload to apply validity checks on.

Anyway, you can implement the countermeasure we implemented in
<https://tools.ietf.org/html/rfc5927#section-7.2> -- I implemented it
for OpenBSD, and it still runs it... and IIRC it was ported to at least
NetBSD later.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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