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

From: Dan Williams <dcbw@redhat.com>
To: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Kalle Valo" <kvalo@kernel.org>,
	"Oleksij Rempel" <linux@rempel-privat.de>,
	"Maciej Żenczykowski" <maze@google.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Andrzej Pietrasiewicz" <andrzejtp2010@gmail.com>,
	"Jacopo Mondi" <jacopo@jmondi.org>,
	"Łukasz Stelmach" <l.stelmach@samsung.com>,
	"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	linux-usb@vger.kernel.org, netdev@vger.kernel.org,
	linux-wireless@vger.kernel.org,
	"Ilja Van Sprundel" <ivansprundel@ioactive.com>,
	"Joseph Tartaro" <joseph.tartaro@ioactive.com>
Subject: Re: [PATCH] USB: disable all RNDIS protocol drivers
Date: Tue, 29 Nov 2022 16:48:07 -0600	[thread overview]
Message-ID: <8b11568a8022cdb759a43f34fdcddf33d9abc37c.camel@redhat.com> (raw)
In-Reply-To: <04ea37cc-d97a-3e00-8a99-135ab38860f2@green-communications.fr>

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.
> 