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Message-ID: <3e8340490912292057g3e87eaabn115f85b78af2b08c@mail.gmail.com>
Date: Tue, 29 Dec 2009 23:57:50 -0500
From: Bryan Donlan <bdonlan@...il.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: "Serge E. Hallyn" <serue@...ibm.com>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Benny Amorsen <benny+usenet@...rsen.dk>,
Michael Stone <michael@...top.org>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-security-module@...r.kernel.org,
Andi Kleen <andi@...stfloor.org>, David Lang <david@...g.hm>,
Oliver Hartkopp <socketcan@...tkopp.net>,
Herbert Xu <herbert@...dor.apana.org.au>,
Valdis Kletnieks <Valdis.Kletnieks@...edu>,
Evgeniy Polyakov <zbr@...emap.net>,
"C. Scott Ananian" <cscott@...ott.net>,
James Morris <jmorris@...ei.org>,
Bernie Innocenti <bernie@...ewiz.org>,
Mark Seaborn <mrs@...hic-beasts.com>,
Randy Dunlap <randy.dunlap@...cle.com>,
Américo Wang <xiyou.wangcong@...il.com>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Samir Bellabes <sam@...ack.fr>,
Casey Schaufler <casey@...aufler-ca.com>,
Pavel Machek <pavel@....cz>, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC][PATCH] Unprivileged: Disable acquisition of privileges
On Tue, Dec 29, 2009 at 11:33 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> Bryan Donlan <bdonlan@...il.com> writes:
>
>> Is this sufficient for other security models such as selinux or
>> TOMOYO? Can processes in these models gain privileges through means
>> not restricted here?
>
> The LSM is primarily about returning -EPERM more often.
> Except for the prctl and the capability hooks I am not aware
> of anywhere a LSM can increase a processes capabilities.
I'm more concerned about a case where a privilege that the LSM
currently denies is lifted by execing some executable - this is still
an increase in privilege, even though the LSM only adds additional
restrictions. That is:
1) Initial state: LSM denies access to /somefile (although normal
POSIX permissions would permit access)
2) Disable capability-gaining
3) Disable network access with proposed API
4) Exec some application, which is labeled in a way that permits
access to /somefile
5) Application fails to access the network, then does something to /somefile
I'm not entirely sure if step 4) can happen in any of the currently
existing LSMs - if it's not possible to gain privileges in them via a
suid-like mechanism, this isn't a problem, but it's something that
needs to be checked for.
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