Re: [Captive-portals] [Int-area] [homenet] Evaluate impact of MAC address randomization to IP applications

["Pascal Thubert (pthubert)" <[e-mail]>]

Hello Dave and all:

So far I have not seen how the MAC randomization deals with:

- DAD - the chances of duplication seem much higher than for IPv6; maybe we can help by doing DAD with something like RFC 8505 on the first hop switch / AP.

- differentiated environments - the preferred behavior on a highway or at a coffee shop may differ from that at in a corporate or a DC network. In the corporate network, we can expect something like .1x to undo the privacy, for good reasons. And we can expect state to be maintained for each IP and each MAC. When a MAC changes, there can be unwanted state created and remaining in the DHCP server, LISP MSMR, SAVI switch,  etc... Privacy MAC is only an additional hassle that we want to minimize.

The current implementations seem to use the SSID to do something similar to RFC 7721. When you come back to the same SSID, you get the same MAC. This helps the corporate network, and is detrimental to the privacy at the coffee shop and the highway, if the same SSID is used across the country in all coffee halts and highway stops.

There appears to be work to do so that:
- the node forms a privacy MAC
- with that privacy MAC the node can do local things like 1x and DAD, if they are available
- if the visited network is recognized, the node applies a behavior (policy) that depends on the visited network
- else use a default higher privacy mode that may renew the MAC more aggressively
- only then, form IP addresses and stuff. If the MAC address was built using privacy, then we could restore the old behavior of embedding it in the IPv6 IID.

Bottom line is that the separate efforts at IETF and IEEE seem to have produced a complex overall solution, with duplicated and somewhat misaligned efforts and yet, gaps. The privacy properties of L2 and L3 addresses are not aligned to a same policy, and is not adapted to the joined network. The impact on upper layers of changing the MAC address is not fully understood. Duplicate addresses are not properly avoided at either layer and yet we pay a high broadcast price on wireless for the inefficient operation of IPv6 DAD. Hopefully we will not replicate that at L2.

This BoF may be an opportunity for IEEE and IETF to work together and converge to a better overall service to the upper layers.

Keep safe

Pascal


> -----Original Message-----
> From: Int-area <[e-mail]> On Behalf Of David R. Oran
> Sent: mardi 22 septembre 2020 23:27
> To: Stephen Farrell <[e-mail]>
> Cc: Michael Richardson <[e-mail]>; [e-mail];
> [e-mail]; [e-mail]
> Subject: Re: [Int-area] [homenet] Evaluate impact of MAC address
> randomization to IP applications
> 
> On 22 Sep 2020, at 17:18, Stephen Farrell wrote:
> 
> > Hiya,
> >
> > On 22/09/2020 22:08, Lee, Yiu wrote:
> >> Hi Stephen,
> >>
> >> Thanks for the notes. Actually, we believe that there are good
> >> privacy reasons to randomize mac-address. This BoF isn't trying to
> >> "fix" randomized mac-address. On the contrary, we want the community
> >> to embrace it. In order to ease the anxiety for transitioning, we
> >> want to document what may break and propose best practice to
> >> transition to dynamic mac-address.
> >
> > Sure, I get that. However, we've seen a number of these efforts start
> > thusly but end up being perceived to be partly trying to unwind the
> > privacy benefits, so I think a good way to avoid that mis-perception
> > is to also present the reasons for (in this case, MAC address
> > randomisation) as fully as the description of the challenges caused.
> >
> Right. it would not advance the case to introduce (or start using) something
> else bout the device that can be tracked and/or provide likability and thereby
> damage privacy in order to preserve the randomized MAC address machinery.
> 
> > Cheers,
> > S.
> >
> >
> >>
> >> Thanks, Yiu
> >>
> >>
> >> On 9/22/20, 4:51 PM, "Int-area on behalf of Stephen Farrell"
> >> <[e-mail] on behalf of [e-mail]>
> >> wrote:
> >>
> >>
> >> That agenda and draft seem to make the seemingly common enough
> >> mistake of only focusing on what a new privacy or security mechanism
> >> breaks and glossing over the good reasons why people introduce these
> >> mechanisms. I hope the BoF proponents fix that because otherwise they
> >> may end up giving the impression that they would prefer to not see
> >> the privacy benefits (which I'd guess is not their goal at all). One
> >> reason those good reasons need to be included is that they constrain
> >> the kinds of additions that might make sense to better handle the new
> >> mechanism.
> >>
> >> We've seen a number of these kinds of reactions and I figure it'd
> >> really be better if the reaction were not to appear purely
> >> reactionary;-)
> >>
> >> If that were fixed, then there may be a better discussion of what, if
> >> any, additional things need doing. If that is not fixed, I'd not be
> >> surprised if the putative BoF were to devolve into a "it's bad" vs.
> >> "no, it's good" bun fight that won't really take us further.
> >>
> >> Cheers, S.
> >>
> >> On 22/09/2020 21:40, Michael Richardson wrote:
> >>>
> >>> Damn. Spelt captive-portal without the s again.  Reposting, sorry
> >>> for duplicates. I hate when WG names and list names do not match,
> >>> and that we can't have aliases. And I think that reply-to gets
> >>> filtered.
> >>>
> >>> Archived-At:
> >>> <https://urldefense.com/v3/__https://mailarchive.ietf.org/arch/msg/i
> >>> nt-
> area/14Skgm84GslPZ9UcGoWY3uzmK6I__;!!CQl3mcHX2A!Q0pEjWrLTcmcryUR
> 2
> >>> EMbSc6uWBNU-xJadaznxWvwmDk2-ARoR0DYYq_eprXSEjo$
> >>>> To: [e-mail], [e-mail], [e-mail]
> >>> From: Michael Richardson <[e-mail]> Date: Tue, 22 Sep
> >>> 2020 16:34:33 -0400
> >>>
> >>> This thread was started today on the INTAREA WG ML.
> >>>
> >>> While I don't object to a BOF, I don't know where it goes. What I
> >>> see is that much of this problem needs to be resolved through
> >>> increased use of 802.1X: making WPA-Enterprise easier to use and
> >>> setup, this changing core identity from MAC Address to IDevID.
> >>>
> >>> My understanding is that Apple intends to randomize MAC every 12
> >>> hours, even on the same "LAN" (ESSID), and that they will just
> >>> repeat the WPA authentication afterwards to get back on the
> >>> network.   If the per-device unique policy (including CAPPORT
> >>> authorization) can be tied to the device better, than the MAC
> >>> address based "physical" exception can be updated.
> >>>
> >>> But, WPA-PSK doesn't work, because it does not, in general,
> >>> distinguish between different devices.
> >>>
> >>> It can be made to work if every device is given a unique PSK, and
> >>> there are some successful experiments doing exactly that.  Mostly it
> >>> just works, but the challenge is communicating the unique PSK
> >>> through an unreliable human. BRSKI can certainly do this, and it can
> >>> leverage that unencrypted ESSID present at most hospitality
> >>> locations to get onto the encrypted WPA-Enterprise.  Or BRSKI-TEEP,
> >>> or some other BRSKI-EAP method.  The unencrypted SSID is not going
> >>> away at those locations.
> >>>
> >>> Thus QR-code based methods are best, yet those do not work for many
> >>> IoT devices.   EMU's EAP-NOOB can help in certain cases, but we, as
> >>> a community need be clear on what direction we want to go.  One
> >>> answer is that IoT devices have little reason to randomize their MAC
> >>> if they are not generally ported.
> >>>
> >>>
> >>> On 2020-09-22 3:49 p.m., Lee, Yiu wrote:
> >>>> Hi team,
> >>>>
> >>>> We proposed a BoF. The agenda is in
> >>>> https://urldefense.com/v3/__https://github.com/jlivingood/IETF109Bo
> >>>> F/blob/master/109-
> Agenda.md__;!!CQl3mcHX2A!Q0pEjWrLTcmcryUR2EMbSc6u
> >>>> WBNU-xJadaznxWvwmDk2-ARoR0DYYq_e7alyc8U$
> >>>> and the proposal is in
> >>>> https://urldefense.com/v3/__https://github.com/jlivingood/IETF109Bo
> >>>> F/blob/master/BoF-Proposal-
> 20200918.md__;!!CQl3mcHX2A!Q0pEjWrLTcmcr
> >>>> yUR2EMbSc6uWBNU-xJadaznxWvwmDk2-ARoR0DYYq_eNfKGqkE$
> >>>> . You can also find the draft here
> >>>> https://urldefense.com/v3/__https://tools.ietf.org/html/draft-lee-r
> >>>> andomized-macaddr-ps-
> 01__;!!CQl3mcHX2A!Q0pEjWrLTcmcryUR2EMbSc6uWBNU
> >>>> -xJadaznxWvwmDk2-ARoR0DYYq_erhCF3-A$
> >>>> .
> >>>>
> >>>> At this stage, we are looking for inputs for more use cases and
> >>>> interests of working together in this domain. Please post your
> >>>> comments in the mailing list.
> >>>>
> >>>> Thanks
> >>>>
> >>>
> >>>
> >>> -- Michael Richardson <[e-mail]>   . o O ( IPv6 IøT
> >>> consulting ) Sandelman Software Works Inc, Ottawa and Worldwide
> >>>
> >>>
> >>> _______________________________________________ homenet mailing
> list
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> >>> menet__;!!CQl3mcHX2A!Q0pEjWrLTcmcryUR2EMbSc6uWBNU-
> xJadaznxWvwmDk2-AR
> >>> oR0DYYq_epVo5mQQ$
> >>
> >>>
> >>
> >>
> >> _______________________________________________ homenet mailing
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> DaveO
> 
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