From: jannh@google.com (Jann Horn)
To: linux-security-module@vger.kernel.org
Subject: [PATCH v5 5/5] sidechannel: Linux Security Module for sidechannel
Date: Fri, 28 Sep 2018 01:47:39 +0200 [thread overview]
Message-ID: <CAG48ez3Jnao-5z3O8s=RdoAx8=b68C_1pfKNKJSm+6R_HyU_fg@mail.gmail.com> (raw)
In-Reply-To: <alpine.LRH.2.21.1809280936290.13517@namei.org>
On Fri, Sep 28, 2018 at 1:43 AM James Morris <jmorris@namei.org> wrote:
> On Thu, 27 Sep 2018, Schaufler, Casey wrote:
> > > > On 9/27/2018 2:45 PM, James Morris wrote:
> > > > > On Wed, 26 Sep 2018, Casey Schaufler wrote:
> > > > >
> > > > >> + /*
> > > > >> + * Namespace checks. Considered safe if:
> > > > >> + * cgroup namespace is the same
> > > > >> + * User namespace is the same
> > > > >> + * PID namespace is the same
> > > > >> + */
> > > > >> + if (current->nsproxy)
> > > > >> + ccgn = current->nsproxy->cgroup_ns;
> > > > >> + if (p->nsproxy)
> > > > >> + pcgn = p->nsproxy->cgroup_ns;
> > > > >> + if (ccgn != pcgn)
> > > > >> + return -EACCES;
> > > > >> + if (current->cred->user_ns != p->cred->user_ns)
> > > > >> + return -EACCES;
> > > > >> + if (task_active_pid_ns(current) != task_active_pid_ns(p))
> > > > >> + return -EACCES;
> > > > >> + return 0;
> > > > > I really don't like the idea of hard-coding namespace security semantics
> > > > > in an LSM. Also, I'm not sure if these semantics make any sense.
> > > >
> > > > Checks on namespaces where explicitly requested.
> > >
> > > By whom and what is the rationale?
> >
> > The rationale is to protect containers. Since those closest thing
> > there is to a definition of containers is "uses namespaces" that
> > becomes the focus. Separating them out does not make too much
> > sense as I would expect someone concerned with one to be concerned
> > with all.
>
> A lot of people will not be using user namespaces due to security
> concerns,
Ugh.
> so with this hard-coded logic, you are saying this case is
> 'safe' in a sidechannel context.
>
> Which hints at the deeper issue that containers are a userland
> abstraction. Protection of containers needs to be defined by userland
> policy.
Or just compare mount namespaces additionally/instead. I think that
containers will always use those, because AFAIK nobody uses chroot()
for containers, given that the kernel makes absolutely no security
guarantees about chroot().
next prev parent reply other threads:[~2018-09-27 23:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-26 20:34 [PATCH v5 0/5] LSM: Support ptrace sidechannel access checks Casey Schaufler
2018-09-26 20:34 ` [PATCH v5 1/5] AppArmor: Prepare for PTRACE_MODE_SCHED Casey Schaufler
2018-09-26 21:16 ` Jann Horn
2018-09-26 21:18 ` Jann Horn
2018-09-26 22:47 ` Schaufler, Casey
2018-09-26 20:34 ` [PATCH v5 2/5] Smack: " Casey Schaufler
2018-09-26 21:30 ` Jann Horn
2018-09-26 22:53 ` Schaufler, Casey
2018-09-26 22:58 ` Jann Horn
2018-10-04 7:47 ` Jiri Kosina
2018-10-04 11:36 ` Jann Horn
2018-10-16 11:44 ` Jiri Kosina
2018-09-26 20:34 ` [PATCH v5 3/5] SELinux: " Casey Schaufler
2018-09-27 15:50 ` Stephen Smalley
2018-09-27 16:23 ` Schaufler, Casey
2018-09-26 20:34 ` [PATCH v5 4/5] Capability: Complete PTRACE_MODE_SCHED Casey Schaufler
2018-09-26 21:26 ` Jann Horn
2018-09-26 22:24 ` Schaufler, Casey
2018-09-26 20:34 ` [PATCH v5 5/5] sidechannel: Linux Security Module for sidechannel Casey Schaufler
2018-09-27 21:45 ` James Morris
2018-09-27 22:39 ` Casey Schaufler
2018-09-27 22:47 ` James Morris
2018-09-27 23:19 ` Schaufler, Casey
2018-09-27 23:43 ` James Morris
2018-09-27 23:47 ` Jann Horn [this message]
2018-09-28 16:33 ` James Morris
2018-09-28 17:40 ` Schaufler, Casey
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