From mboxrd@z Thu Jan  1 00:00:00 1970
From: Valdis.Kletnieks@vt.edu
Subject: Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)
Date: Mon, 11 Jan 2010 21:54:13 -0500
Message-ID: <5768.1263264853@localhost>
References: <alpine.LRH.2.00.1001110811350.25601@tundra.namei.org> <20100110215409.GA3705@heat>
            <20100110215848.GA26609@elf.ucw.cz>
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Cc: Michael Stone <michael@laptop.org>,
	James Morris <jmorris@namei.org>, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, linux-security-module@vger.kernel.org,
	Andi Kleen <andi@firstfloor.org>, David Lang <david@lang.hm>,
	Oliver Hartkopp <socketcan@hartkopp.net>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Bryan Donlan <bdonlan@gmail.com>,
	Evgeniy Polyakov <zbr@ioremap.net>,
	"C. Scott Ananian" <cscott@cscott.net>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Bernie Innocenti <bernie@codewiz.org>,
	Mark Seaborn <mrs@mythic-beasts.com>,
	Randy Dunlap <randy.dunlap@oracle.com>,
	=?iso-8859-1?Q?Am=E9rico?= Wang <xiyou.wangcong@gmail.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Samir Bellabes <sam@synack.fr>,
	Casey Schaufler <casey@schaufler-ca.com>,
	"Serge E. Hallyn" <serue@us.ibm.com>,
	Al Viro <viro@ZenIV.linux.org.uk>
To: Pavel Machek <pavel@ucw.cz>
Return-path: <linux-security-module-owner@vger.kernel.org>
In-Reply-To: Your message of "Sun, 10 Jan 2010 22:58:48 +0100."
             <20100110215848.GA26609@elf.ucw.cz>
Sender: linux-security-module-owner@vger.kernel.org
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On Sun, 10 Jan 2010 22:58:48 +0100, Pavel Machek said:

> Scenario 2:
> 
> Mallory calls disablenetwork, calls sendmail as the first user after
> boot; sendmail can't deliver anything (its network is disabled), but
> starts forking and taking requests for other users, DoSing the mail
> delivery.

You need to be root to start sendmail as a daemon.  If Mallory is getting
a root shell before your /etc/rc.d scripts have started sendmail, you
have bigger problems.

> Scenario 3:
> 
> Mallory calls disablenetwork, then keeps hammering on su, knowing that
> su can no longer send data to audit subsystem and so he will not get caught.

I assume you mean syslog, not audit.  And it still won't work.

% strace /usr/bin/logger test message
...
socket(PF_FILE, SOCK_DGRAM|SOCK_CLOEXEC, 0) = 1
connect(1, {sa_family=AF_FILE, path="/dev/log"}, 110) = 0
sendto(1, "<13>Jan 11 21:49:25 logger: test"..., 40, MSG_NOSIGNAL, NULL, 0) = 40
close(1)                                = 0

su's complaint will get written to /dev/log which isn't interfered with
by the disablenetwork patch - and then syslogd will forward over the net
if configured to do so.

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