Re: Limiting what devices can pair over Bluetooth?

From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
To: James Pearson <james-p@moving-picture.com>
Cc: "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
Subject: Re: Limiting what devices can pair over Bluetooth?
Date: Wed, 8 Jan 2020 12:53:31 -0800	[thread overview]
Message-ID: <CABBYNZKAkZLvce-MfpscV6Y=9+UBVXAdcVgKAWTH8HupW8_qVA@mail.gmail.com> (raw)
In-Reply-To: <ac3d2402-abad-96dc-b042-8c8c7d592124@moving-picture.com>

Hi James,

On Wed, Jan 8, 2020 at 12:15 PM James Pearson
<james-p@moving-picture.com> wrote:
>
> Luiz Augusto von Dentz wrote:
> > Hi James,
> >
> > On Wed, Jan 8, 2020 at 3:47 AM James Pearson
> > <james-p@moving-picture.com> wrote:
> >>
> >> We don't normally enable Bluetooth on Linux (CentOS 7) installs for
> >> security reasons, but we have a case where we would like to use a
> >> Wacom tablet over Bluetooth
> >>
> >> I would like to be able to configure things so Bluetooth can _only_
> >> be used to pair with Wacom tablets (or just HID devices?)
> >>
> >> As I never used Bluetooth in anger before, I'm struggling to find
> >> out where to start looking - does anyone know how to do this - or
> >> any pointers for where I should start looking?
> >
> > Are you asking this from the system or user perspective, from the
> > system we don't have a configuration where you can restrict the
> > types of devices that the user can pair, on the other hand there is
> > nothing stopping the user interface (gnome, kde, etc) to implement
> > such policy on their bluetooth settings, though be aware targeting a
> > subset of HID devices may not be possible.
>
> Ideally I would want to limit this at the system level - although I can
> not find anything user interface-wise that mentions limiting access
> either (although I might be looking in the wrong places?)
>
> My aim is to prevent Bluetooth being used (in any way) to transfer
> files/data on/off the workstation
>
> I've found that if I blacklist the bnep, cmtp and rfcomm kernel modules
> (just leaving the bluetooth and hidp kernel modules enabled) then the
> Wacom tablet still works over Bluetooth

bnep is for tethering, depending on the system that might be useful,
and if you block RFCOMM you no only block usage of file transfer but
also HFP, but perhaps you don't care about those so that would be fine
to disable. Btw, for getting file sharing you would just need to
disable obexd though it doesn't seems it is a user service which you
can disable with systemctl.

> Would this be sufficient to prevent any kind of file transfer over
> Bluetooth ?
>
> Thanks
>
> James Pearson

-- 
Luiz Augusto von Dentz