Re: [v6ops] A common problem with SLAAC in "renumbering" scenarios

Fernando Gont <fgont@si6networks.com> Mon, 25 February 2019 18:30 UTC

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Subject: Re: [v6ops] A common problem with SLAAC in "renumbering" scenarios
To: Lorenzo Colitti <lorenzo=40google.com@dmarc.ietf.org>, Richard Patterson <richard@helix.net.nz>
Cc: IPv6 Operations <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>, Fernando Gont <fernando@gont.com.ar>
References: <6D78F4B2-A30D-4562-AC21-E4D3DE019D90@consulintel.es> <B6E2EC33-EEAF-40D0-AFCC-BDAFA9134ACD@consulintel.es> <20190220113603.GK71606@Space.Net> <28fbc2c305c640c9afb3704050f6e8d7@boeing.com> <20190220213107.GS71606@Space.Net> <019c552eb1624d348641d6930829fd1f@boeing.com> <CAKD1Yr0HBG+rhyFWg9zh0t3mW486Mjx9umjn+CRqAZg4z9r0dg@mail.gmail.com> <20190221073530.GT71606@Space.Net> <CAO42Z2wmB2W52b4MZ2h9sW5E9cQKm-HRjyf--q8C26jezS7LXQ@mail.gmail.com> <a73818d31db7422b99a524bc431b00ed@boeing.com> <CAO42Z2z9-48Gbb_Exf+oWUqDO=axSLpZBtqeDcxkAoFq5OziGw@mail.gmail.com> <CALx6S3624hnGauG1HaSWPMvQw0t2Q5R3gb8W4R8w3kuK7dcrWQ@mail.gmail.com> <1F07F2BB-2F37-4D12-9731-7892DF4E3D88@consulintel.es> <0a582916-af14-bd82-a4cd-002a36f8830b@huitema.net> <67515a73-26a5-3ed0-da88-1a4ce64550d3@foobar.org> <360afa02-cf23-375c-4876-780d3c2aa5ac@gont.com.ar> <CAHL_VyD34V=TRcsCp0DOO9HJNHyy5xkiMQ_cZoBa7zTE4fe5OA@mail.gmail.com> <CAKD1Yr1rQ-yUAq33gUcoCE6fJjmjwXE1muBQ+JOVEQYVEOtZCw@mail.gmail.com>
From: Fernando Gont <fgont@si6networks.com>
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Date: Mon, 25 Feb 2019 15:29:40 -0300
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Hello, Lorenzo,

On 25/2/19 10:27, Lorenzo Colitti wrote:
> On Mon, Feb 25, 2019 at 7:33 PM Richard Patterson <richard@helix.net.nz
> <mailto:richard@helix.net.nz>> wrote:
> 
>     The Valid Lifetime cannot be zeroed or shortened below 2 hours, but
>     the Preferred Lifetime can.  So we can't invalidate the prefix, but we
>     can deprecate it so it's not used for new outbound sessions.   This is
>     what we've implemented in our CPEs, after an unavoidable change in
>     prefix, and it seems to have mitigated (or reduced the impact of) the
>     issue.
> 
>     RFC4862 §5.5.3
> 
>     e)  If the advertised prefix is equal to the prefix of an address
>           configured by stateless autoconfiguration in the list, the
>           preferred lifetime of the address is reset to the Preferred
>           Lifetime in the received advertisement.
> 
> 
> Have we considered simply removing this paragraph and allowing routers
> to send RA lifetimes of 0? On an IPv6-capable network, an attacker that
> is able to send RAs can do way more damage than just this sort of DOS
> attack - they can collect/monitor traffic, selectively block
> destinations or sources, etc. etc.

I completely agree.

And yes, we have considered that and will be incorporating that in the
next rev of the I-D.

If you want to peek at my working copy (upcoming version -02), it is
available at:
https://github.com/fgont/draft-slaac-renum/raw/master/draft-gont-6man-slaac-renum-02.txt
   (Section 5.1.1.2 proposes this, with the same rationale you suggested
above).

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492