linux-kernel - Re: [PATCH] Define CAP

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Date:	Sat, 13 Mar 2010 23:35:21 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	mtk.manpages@...il.com
Cc:	James Morris <jmorris@...ei.org>,
	lkml <linux-kernel@...r.kernel.org>,
	SELinux <selinux@...ho.nsa.gov>,
	linux-security-module@...r.kernel.org,
	Stephen Smalley <sds@...ch.ncsc.mil>,
	Kees Cook <kees.cook@...onical.com>,
	Andrew Morgan <morgan@...nel.org>,
	"Christopher J. PeBenito" <cpebenito@...sys.com>,
	Eric Paris <eparis@...isplace.org>
Subject: Re: [PATCH] Define CAP_SYSLOG

Quoting Michael Kerrisk (mtk.manpages@...glemail.com):
> > There is one downside to this patch:  If some site or distro currently
> > has syslogd/whatever running as a non-root user with cap_sys_admin+pe,
> > then it will need to be changed to run with cap_syslog+pe.  I don't
> > know if there are such sites, or if that concern means we should take
> > a different approach to introducing this change, or simply refuse this
> > change.
> 
> *If* this is a problem, would the way to address it not be to permit
> syslog if the caller has *either* CAP_SYS_ADMIN or CAP_SYSLOG? (The
> only weakness I see in this idea is that it fails to lighten the
> hugely overlaoded CAP_SYS_ADMIN.)

Which becomes a very big weakness because it won't allow a
container to be started with cap_sys_admin but not cap_syslog
in its capability bounding set.

So, if it is deemed a problem, then the alternative will be to
introduce a syslog namespace.  Container setup can then create
a new syslog namespace, and can no longer read or clear the
host's syslog.

thanks,
-serge
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