linux-kernel - Re: [PATCH v2] kernel: Conditionally support non-root users, groups and capabilities

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Message-ID: <54CBDFF4.1070503@schaufler-ca.com>
Date:	Fri, 30 Jan 2015 11:48:04 -0800
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	josh@...htriplett.org
CC:	paulmck@...ux.vnet.ibm.com, Iulia Manda <iulia.manda21@...il.com>,
	gnomes@...rguk.ukuu.org.uk, serge.hallyn@...onical.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	peterz@...radead.org, mhocko@...e.cz,
	LSM <linux-security-module@...r.kernel.org>,
	Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v2] kernel: Conditionally support non-root users, groups
 and capabilities

On 1/30/2015 11:13 AM, josh@...htriplett.org wrote:
> On Thu, Jan 29, 2015 at 06:25:23PM -0800, Casey Schaufler wrote:
>> On 1/29/2015 5:36 PM, Paul E. McKenney wrote:
>>> A few K here, a few K there, and pretty soon you actually fit into the
>>> small-memory 32-bit SoCs.  I do not believe that the processing time
>>> is the issue.
>> And UNIX, with UID and GID processing, used to run in 64K of RAM,
>> without swap or paging. Bluntly, there are many other places to look
>> before you go here.
> And we're looking in all those places too.  Each patch is worth
> evaluating independently.  We've *already* gone here, the code is
> written (and being revised based on feedback), and "go work over there
> out of my backyard" is not going to work.  One of these days, we're
> going to run in 64k again.

Oh good heavens. Don't take this personally. I don't.

>>>> As for LSMs, I can easily see putting in the security model from the old
>>>> RTOS on top of a NON_ROOT configuration. Won't that be fun when the CVEs
>>>> start to fly?
> The security model is "there's one process on this system".  (Expect
> patches for CONFIG_FORK=n and CONFIG_EXEC=n at some point.)

Ok. Why not use Bada?

>>>> Do you think you'll be running system services like systemd on top of this?
>>>> Anyone *else* remember what happened when they put capability handling into
>>>> sendmail?
>>> Nope, I don't expect these systems to be using LSM, systemd, or sendmail.
>>> I think that many of these will instead run the application directly
>>> out of the init process.
>> Where an "application" might be something like CrossWalk,
> No, not a chance.  If you're running a web runtime, you're on a much
> larger system, and you're going to be less concerned about shaving
> kilobytes; you're also going to want many of the kernel facilities for
> sandboxing code.
>
> The kinds of applications we're talking about here run entirely in one
> binary, serving a few very narrow functions.  We're not talking
> "automobile IVI system" here; we're talking "two buttons and an output",
> or "a few sensors and an SD card".

Linux is an insane choice for such a system. Why would you
even consider it?

>
> - Josh Triplett
>

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