linux-kernel - Re: [RFC][PATCH v3] Unprivileged: Disable raising of privileges

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Message-ID: <m2bphfti1u.fsf@ssh.synack.fr>
Date:	Thu, 31 Dec 2009 14:00:13 +0100
From:	Samir Bellabes <sam@...ack.fr>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	ebiederm@...ssion.com (Eric W. Biederman),
	"Serge E. Hallyn" <serue@...ibm.com>,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Bryan Donlan <bdonlan@...il.com>,
	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>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Pavel Machek <pavel@....cz>, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC][PATCH v3] Unprivileged: Disable raising of privileges

Alan Cox <alan@...rguk.ukuu.org.uk> writes:

> Well to be fair its random regurgitated security idea of every year or
> two.

true, last year the same kind of discussion occurs with the 'personal
firewall' aka a network MAC.
http://marc.info/?t=123247387500003&r=3&w=2
http://marc.info/?t=123187029200001&r=2&w=2

> More to the point - we have security_* hooks so this kind of continuous
> security proposal turdstream can stay out of the main part of the kernel.

indeed, LSM framework was design to be the abstraction tool. the 3
design rules were : 

0. truly generic, where using a different security model is merely a
   matter of loading a different kernel module;
1. conceptually simple, minimally invasive, and efficient; and
2. able to support the existing POSIX.1e capabilities logic as an
   optional security module.

so, 'minimally invasive' is keyword. what's why I don't understand the
purpose of this kind of patch, even if I see the goal to achieve:

 int security_socket_connect(struct socket *sock, struct sockaddr *address, int addrlen)
 {
-	return security_ops->socket_connect(sock, address, addrlen);
+	int ret = 0;
+
+	ret = security_ops->socket_connect(sock, address, addrlen);
+	if (ret)
+		goto out;
+
+#ifdef CONFIG_SECURITY_DISABLENETWORK
+	ret = disablenetwork_security_socket_connect(sock, address, addrlen);
+	if (ret)
+		goto out;
+#endif
+
+out:
+	return ret;
 }

This really seems to be a kind of stacking, but it's not. So are we
going to move LSM framework to support stacking, or are we respecting
the rules of LSM framework (respecting the abstract hooks) ?
This change makes LSM framework no more generic at all.
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