linux-kernel - Re: RFC: disablenetwork facility. (v4)

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Message-ID: <3e8340490912291243q7ba43fd9v266835ebbda9315b@mail.gmail.com>
Date:	Tue, 29 Dec 2009 15:43:52 -0500
From:	Bryan Donlan <bdonlan@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Benny Amorsen <benny+usenet@...rsen.dk>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	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>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	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: disablenetwork facility. (v4)

On Tue, Dec 29, 2009 at 3:40 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> Benny Amorsen <benny+usenet@...rsen.dk> writes:
>
>> Bryan Donlan <bdonlan@...il.com> writes:
>>
>>> I, for one, think it would be best to handle it exactly like the
>>> nosuid mount option - that is, pretend the file doesn't have any
>>> setuid bits set. There's no reason to deny execution; if the process
>>> would otherwise be able to execute it, it can also copy the file to
>>> make a non-suid version and execute that instead.
>>
>> Execute != read. The executable file may contain secrets which must not
>> be available to the user running the setuid program. If you fail the
>> setuid, the user will be able to ptrace() and then the secret is
>> revealed.
>>
>> It's amazing how many security holes appear from what seems like a very
>> simple request.
>
> Do we have a security hole in nosuid mount option?

Looks like it:
$ /tmp/m/sudo
sudo: must be setuid root
$ ls -l /tmp/m/sudo
-rwsr-x--x 1 root root 123448 2009-06-22 12:14 /tmp/m/sudo
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