linux-kernel - Re: [libseccomp-discuss] ANN: libseccomp

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Message-ID: <4892415.SaF4mnePOG@sifl>
Date:	Mon, 16 Apr 2012 10:15:33 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	libseccomp-discuss@...ts.sourceforge.net
Cc:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	linux-security-module@...r.kernel.org,
	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org
Subject: Re: [libseccomp-discuss] ANN: libseccomp

On Friday, April 13, 2012 11:47:08 PM Henrique de Moraes Holschuh wrote:
> On Fri, 13 Apr 2012, Paul Moore wrote:
> > the seccomp filter into the kernel.  By default libseccomp attempts to set
> > NO_NEW_PRIVS but does not fail if prctl(NO_NEW_PRIVS) returns with an
> > error;
>
> Isn't that dangerous in non-obvious ways, as in it can actually
> cause/activate/enable/open security issues on priviledged processes that
> don't expect whatever filtering seccomp will subject them to?

We could debate this point but it turns out it is a bit of a non-issue as the 
kernel code requires NO_NEW_PRIVS unless CAP_SYS_ADMIN is set; if neither 
conditions are true the seccomp filter with fail (check Will's patches).

If prctl(NO_NEW_PRIVS) fails the error is always returned, and the 
attribute/boolean to disable this functionality has been removed since it 
likely serves little purpose.

> Defaults are important, as they're what people _who don't know any better_
> are likely to use.

Agreed.  You'll never hear me argue otherwise.

-- 
paul moore
www.paul-moore.com

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