netdev - Re: [PATCH] USB: disable all RNDIS protocol drivers

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Date:   Tue, 29 Nov 2022 16:48:07 -0600
From:   Dan Williams <dcbw@...hat.com>
To:     Nicolas Cavallari <nicolas.cavallari@...en-communications.fr>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Kalle Valo <kvalo@...nel.org>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Maciej Żenczykowski <maze@...gle.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andrzej Pietrasiewicz <andrzejtp2010@...il.com>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Łukasz Stelmach <l.stelmach@...sung.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org,
        Ilja Van Sprundel <ivansprundel@...ctive.com>,
        Joseph Tartaro <joseph.tartaro@...ctive.com>
Subject: Re: [PATCH] USB: disable all RNDIS protocol drivers

On Wed, 2022-11-23 at 16:40 +0100, Nicolas Cavallari wrote:
> On 23/11/2022 13:46, Greg Kroah-Hartman wrote:
> > The Microsoft RNDIS protocol is, as designed, insecure and
> > vulnerable on
> > any system that uses it with untrusted hosts or devices.  Because
> > the
> > protocol is impossible to make secure, just disable all rndis
> > drivers to
> > prevent anyone from using them again.
> > 
> > Windows only needed this for XP and newer systems, Windows systems
> > older
> > than that can use the normal USB class protocols instead, which do
> > not
> > have these problems.
> > 
> > Android has had this disabled for many years so there should not be
> > any
> > real systems that still need this.
> 
> I kind of disagree here. I have seen plenty of android devices that
> only 
> support rndis for connection sharing, including my android 11 phone 
> released in Q3 2020. I suspect the qualcomm's BSP still enable it by 
> default.
> 
> There are also probably cellular dongles that uses rndis by default. 
> Maybe ask the ModemManager people ?

Yes, there are.

Another class of WWAN dongles presented as USB RNDIS to the host, had
an onboard DHCP server, and "bridged" that (for lack of a better term)
to the WWAN. And like a home router exposed HTTP based management on
192.168.1.1 to control the WWAN stuff.

https://openwrt.org/docs/guide-user/network/wan/wwan/ethernetoverusb_rndis

RE Wifi, (echoing Johannes) there was one Broadcom chipset, but a bunch
of devices used it. I have some though I don't actively use them. But
they still work...

Dan

> 
> I'm also curious if reimplementing it in userspace would solve the 
> security problem.
>