Eliot Lear <[email protected]> wrote: > A few of us are just trying to put out an initial draft that addresses > one gap in MUD (there are several).
> In a MUD file one can say that one
> wants to access a controller in two ways: either "my-controller”
> meaning a controller that services devices of a particular MUD URL or a
> “controller” class that services devices based on a particular class
> name of controller.
I think that we have two potential avenues for security attacks here:
1) a device that claims to be a controller in order to gain access to
devices.
2) devices that claim to be belong to a controller in order to attack
controllers.
To my mind there are some different things we could do:
1) insist that to user the my-controller connections that the two devices
have to be signed by the "same" entity. ["same" could mean literal the
same key, the same certificate Issuer/DN, or something more complex]
2) we could have devices declare in an MUD extension the
DN/certificate/entity which must sign their controller device.
3) (2) above, but with some level of indirection through some URL.
> In either case, right now the administrator has to manually know and
> populate information, to say - some device 1.2.3.4 is a controller,
> either for MUD URL https://example.com/mud <https://example.com/mud> or
> a class http://example.com/mudclass1 <http://example.com/mudclass1>.
> That can be laborious. To assist, we are examining ways to have a
> controller declare itself as a candidate controller. That at least
> provides a hint to the administrator that this particular device is
> capable of serving in a particular role.
I think that anything that requires administrator activity to be a fail for
residential use. It's too complex.
> To make that declaration, the device must- Form the declaration; Find
> the MUD manager; and Send it.
> Finding the MUD manager depends on one question: Was the device built
> to be a controller or is it a general purpose device that has an app
> that is intended to be a controller?
> If the device was built to be a controller, we can simply cram the
> declaration into that devices own MUD file as an extension. If the
> device is a general purpose computer, things get a bit more
> interesting.
Yes... but I think that we have to solve the multi-purpose computer MUD
anyway. The intelligent speakers (Echo,Home,Mycroft,etc.) need to gain new
MUD definitions as they gain "skills", and I think that we can treat a
smartphone in a similar way.
This might be a place where IPv6 wins, if we can split off each skill into a
new provisioning domain, giving it a new IPv6 IID. I was thinking that maybe
we can associate the private key that signed the MUD file to the IID via
something like SEND/CGA, but I'm not sure how many private keys we have
(one for the app developer, or one per app installed on each device).
> In this case we have two choices:
> Either create a MUD file that points somewhere internally - this
> doesn’t seem very plug and play. Make the declaration directly to the
> MUD manager.
> I’m going to focus on the latter for the moment. It is easy enough to
> create a RESTful interface for this purpose, but it requires a
> mechanism to discovered the MUD manager, which up until now has been an
> internal part of the network infrastructure.
> Let me call this out plainly: letting the app itself directly call the
> MUD manager requires that the MUD manager itself become exposed to the
> user infrastructure, which is a change.
Agreed.
And that the MUD manager have some reason to trust the device is not p0wned,
and sending a bogus MUD file up. A certificate chain back to the
manufacturer is not enough, it has to be signed by a key that an attacker
can't get access to. So that requires attested keys if they are "local", or
for the signature to be done elsewhere.
> One possibility to address this is to incorporate the new RESTful
> endpoint into an ANIMA BRSKI join registrar, which may already be
> exposed. But that requires that ANIMA BRSKI be in play, which it may
> not.
It is, however, a really good idea for the case where it is in play.
> My thinking is that we do this work in two stages. First handle the
> easy case, which is the MUD file extension, and then figure out how to
> do the app version of this.
> Thoughts?
yes.
--
Michael Richardson <[email protected]>, Sandelman Software Works
-= IPv6 IoT consulting =-
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