linux-kernel - Re: USB devices on Dell TB16 dock stop working after resuming

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Message-ID: <20191120174301.GO11621@lahna.fi.intel.com>
Date:   Wed, 20 Nov 2019 19:43:01 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Yehezkel Bernat <yehezkelshb@...il.com>
Cc:     Mario Limonciello <Mario.Limonciello@...l.com>,
        pmenzel@...gen.mpg.de, Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>, ck@...om.net,
        LKML <linux-kernel@...r.kernel.org>,
        Anthony Wong <anthony.wong@...onical.com>
Subject: Re: USB devices on Dell TB16 dock stop working after resuming

On Wed, Nov 20, 2019 at 07:16:58PM +0200, Yehezkel Bernat wrote:
> On Wed, Nov 20, 2019 at 7:06 PM <Mario.Limonciello@...l.com> wrote:
> >
> >
> > But I mean this is generally an unsafe (but convenient) option, it means that you
> > throw out security pre-boot, and all someone needs to do is turn off your machine,
> > plug in a malicious device, turn it on and then they have malicious device all the way
> > into OS.
> 
> Only if the attacker found how to forge the device UUID (and knew what UUIDs
> are allowed), isn't it? Unless you take into account things like
> external GPU box,
> where it's pretty easy to replace the card installed inside it.

No need to forge UUID if you can "borrow" the laptop for a while so that
you boot your own OS there that then updates the Boot ACL with your
malicious device UUIDs. Then you return the laptop and now it suddenly
allows booting from those as well.