Re: RFC4941bis implementations

On Fri, 3 Apr 2020, 07:12 Florian Obser, <florian@openbsd.org> wrote:

> On Thu, Apr 02, 2020 at 09:09:26PM +0200, Alexandre Petrescu wrote:
> > Le 02/04/2020 à 19:26, Fernando Gont a écrit :
> > > Folks,
> > >
> > > FWIW, I produce a patch for Linux kernel (net-next) that implements
> > > rfc4941bis:
> > > https://www.gont.com.ar/code/fgont-patch-linux-net-next-rfc4941bis.txt
> > > (up & running here).
> >
> > Does it work with a plen 65 in RA?
>
> I'm happy to report that slaacd(8) in OpenBSD does not care about the plen.
> It just forms a 128 bit random number and overwrites the front with
> the prefix.[1]
> So if you put your whole /29 onlink you can have 99 bits of entropy!
>

Or 1 bit of entropy if you use a 127.

Might be worth issuing a warning about the privacy properties of an RFC4941
address if the prefix length gets to long.

A false sense of privacy is probably just as bad as a false sense of
security.

Regards,
Mark.

> Cheers,
> Florian
>
> >
> > Alex, LF/HF 1
>
> 1) https://github.com/openbsd/src/blob/master/sbin/slaacd/engine.c#L1415
>
> --
> I'm not entirely sure you are real.
>
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