linux-kernel - Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)

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Date:	Mon, 18 Jan 2010 07:54:04 -0500
From:	Valdis.Kletnieks@...edu
To:	Pavel Machek <pavel@....cz>
Cc:	Michael Stone <michael@...top.org>,
	James Morris <jmorris@...ei.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>,
	Bryan Donlan <bdonlan@...il.com>,
	Evgeniy Polyakov <zbr@...emap.net>,
	"C. Scott Ananian" <cscott@...ott.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Bernie Innocenti <bernie@...ewiz.org>,
	Mark Seaborn <mrs@...hic-beasts.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Am?rico Wang <xiyou.wangcong@...il.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Samir Bellabes <sam@...ack.fr>,
	Casey Schaufler <casey@...aufler-ca.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Al Viro <viro@...IV.linux.org.uk>
Subject: Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)

On Thu, 14 Jan 2010 10:22:51 +0100, Pavel Machek said:
> > On Tue, 12 Jan 2010 08:59:27 +0100, Pavel Machek said:
> > 
> > > Well, maybe, but mailer system where first user starts is as a daemon
> > > makes sense...
> > 
> > Does it?  How do you get port 25 open for listening if the first user isn't
> > root?  Most *actual* schemes to "launch at first use" that require privs fo
r
> > something have used inetd or similar - that program exists for a
> > *reason*.
> 
> Remember sendmail is setuid root... so it already has the permissions.

Actually, the sendmail setuid bit was removed quite some time ago:

8.12.0/8.12.0   2001/09/08
        *NOTICE*: The default installation of sendmail does not use
                set-user-ID root anymore.  You need to create a new user and
                a new group before installing sendmail (both called smmsp by
                default).  The installation process tries to install
                /etc/mail/submit.cf and creates /var/spool/clientmqueue by
                default.  Please see sendmail/SECURITY for details.

Wow.  2001. And people *still* think it's setuid. ;)

(Interestingly enough, the capabilities bug came *later*:

8.12.1/8.12.1   2001/10/01
        SECURITY: Check whether dropping group privileges actually succeeded
                to avoid possible compromises of the mail system by
                supplying bogus data.  Add configuration options for
                different set*gid() calls to reset saved gid.  Problem
                found by Michal Zalewski.

and was mostly an issue because the same problem existed in pre-8.12 sendmails
that were still setuid and hadn't upgraded yet...


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