From: Andy Lutomirski <luto@amacapital.net>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: "Mickaël Salaün" <mic@digikod.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Arnd Bergmann" <arnd@arndb.de>,
"Casey Schaufler" <casey@schaufler-ca.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Daniel Mack" <daniel@zonque.org>,
"David Drysdale" <drysdale@google.com>,
"David S . Miller" <davem@davemloft.net>,
"Elena Reshetova" <elena.reshetova@intel.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"James Morris" <james.l.morris@oracle.com>,
"Kees Cook" <keescook@chromium.org>,
"Paul Moore" <pmoore@redhat.com>,
"Sargun Dhillon" <sargun@sargun.me>,
"Serge E . Hallyn" <serge@hallyn.com>,
"Tejun Heo" <tj@kernel.org>, "Will Drewry" <wad@chromium.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
"Linux API" <linux-api@vger.kernel.org>,
"LSM List" <linux-security-module@vger.kernel.org>,
"Network Development" <netdev@vger.kernel.org>,
"open list:CONTROL GROUP (CGROUP)" <cgroups@vger.kernel.org>
Subject: [kernel-hardening] Re: [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks
Date: Wed, 14 Sep 2016 19:27:08 -0700 [thread overview]
Message-ID: <CALCETrWXjJZZRj5XvDQ+-Grue+b4MW2TFKsfgYYFYoFBFVH71g@mail.gmail.com> (raw)
In-Reply-To: <20160915021940.GA65119@ast-mbp.thefacebook.com>
On Wed, Sep 14, 2016 at 7:19 PM, Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
> On Wed, Sep 14, 2016 at 06:25:07PM -0700, Andy Lutomirski wrote:
>> On Wed, Sep 14, 2016 at 3:11 PM, Mickaël Salaün <mic@digikod.net> wrote:
>> >
>> > On 14/09/2016 20:27, Andy Lutomirski wrote:
>> >> On Wed, Sep 14, 2016 at 12:24 AM, Mickaël Salaün <mic@digikod.net> wrote:
>> >>> Add a new flag CGRP_NO_NEW_PRIVS for each cgroup. This flag is initially
>> >>> set for all cgroup except the root. The flag is clear when a new process
>> >>> without the no_new_privs flags is attached to the cgroup.
>> >>>
>> >>> If a cgroup is landlocked, then any new attempt, from an unprivileged
>> >>> process, to attach a process without no_new_privs to this cgroup will
>> >>> be denied.
>> >>
>> >> Until and unless everyone can agree on a way to properly namespace,
>> >> delegate, etc cgroups, I think that trying to add unprivileged
>> >> semantics to cgroups is nuts. Given the big thread about cgroup v2,
>> >> no-internal-tasks, etc, I just don't see how this approach can be
>> >> viable.
>> >
>> > As far as I can tell, the no_new_privs flag of at task is not related to
>> > namespaces. The CGRP_NO_NEW_PRIVS flag is only a cache to quickly access
>> > the no_new_privs property of *tasks* in a cgroup. The semantic is unchanged.
>> >
>> > Using cgroup is optional, any task could use the seccomp-based
>> > landlocking instead. However, for those that want/need to manage a
>> > security policy in a more dynamic way, using cgroups may make sense.
>> >
>> > I though cgroup delegation was OK in the v2, isn't it the case? Do you
>> > have some links?
>> >
>> >>
>> >> Can we try to make landlock work completely independently of cgroups
>> >> so that it doesn't get stuck and so that programs can use it without
>> >> worrying about cgroup v1 vs v2, interactions with cgroup managers,
>> >> cgroup managers that (supposedly?) will start migrating processes
>> >> around piecemeal and almost certainly blowing up landlock in the
>> >> process, etc?
>> >
>> > This RFC handle both cgroup and seccomp approaches in a similar way. I
>> > don't see why building on top of cgroup v2 is a problem. Is there
>> > security issues with delegation?
>>
>> What I mean is: cgroup v2 delegation has a functionality problem.
>> Tejun says [1]:
>>
>> We haven't had to face this decision because cgroup has never properly
>> supported delegating to applications and the in-use setups where this
>> happens are custom configurations where there is no boundary between
>> system and applications and adhoc trial-and-error is good enough a way
>> to find a working solution. That wiggle room goes away once we
>> officially open this up to individual applications.
>>
>> Unless and until that changes, I think that landlock should stay away
>> from cgroups. Others could reasonably disagree with me.
>
> Ours and Sargun's use cases for cgroup+lsm+bpf is not for security
> and not for sandboxing. So the above doesn't matter in such contexts.
> lsm hooks + cgroups provide convenient scope and existing entry points.
> Please see checmate examples how it's used.
>
To be clear: I'm not arguing at all that there shouldn't be
bpf+lsm+cgroup integration. I'm arguing that the unprivileged
landlock interface shouldn't expose any cgroup integration, at least
until the cgroup situation settles down a lot.
--Andy
next prev parent reply other threads:[~2016-09-15 2:27 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-14 7:23 [kernel-hardening] [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 01/22] landlock: Add Kconfig Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 02/22] bpf: Move u64_to_ptr() to BPF headers and inline it Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 03/22] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles Mickaël Salaün
2016-09-14 18:51 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 23:22 ` Mickaël Salaün
2016-09-14 23:28 ` Alexei Starovoitov
2016-09-15 21:51 ` Mickaël Salaün
2016-10-03 23:53 ` Kees Cook
2016-10-05 22:02 ` Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 04/22] bpf: Set register type according to is_valid_access() Mickaël Salaün
2016-10-19 14:54 ` [kernel-hardening] " Thomas Graf
2016-10-19 15:10 ` Daniel Borkmann
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 05/22] bpf,landlock: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2016-10-19 15:01 ` [kernel-hardening] " Thomas Graf
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 06/22] landlock: Add LSM hooks Mickaël Salaün
2016-10-19 15:19 ` [kernel-hardening] " Thomas Graf
2016-10-19 22:42 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 07/22] landlock: Handle file comparisons Mickaël Salaün
2016-09-14 19:07 ` [kernel-hardening] " Jann Horn
2016-09-14 22:39 ` Mickaël Salaün
2016-09-14 21:06 ` Alexei Starovoitov
2016-09-14 23:02 ` Mickaël Salaün
2016-09-14 23:24 ` Alexei Starovoitov
2016-09-15 21:25 ` Mickaël Salaün
2016-09-20 0:12 ` [kernel-hardening] lsm naming dilemma. " Alexei Starovoitov
2016-09-20 1:10 ` [kernel-hardening] " Sargun Dhillon
2016-09-20 16:58 ` Mickaël Salaün
2016-10-03 23:30 ` [kernel-hardening] " Kees Cook
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 08/22] seccomp: Fix documentation for struct seccomp_filter Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 09/22] seccomp: Move struct seccomp_filter in seccomp.h Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 10/22] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 11/22] seccomp,landlock: Handle Landlock hooks per process hierarchy Mickaël Salaün
2016-09-14 18:43 ` [kernel-hardening] " Andy Lutomirski
2016-09-14 22:34 ` Mickaël Salaün
2016-10-03 23:52 ` Kees Cook
2016-10-05 21:05 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 12/22] bpf: Cosmetic change for bpf_prog_attach() Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 13/22] bpf/cgroup: Replace struct bpf_prog with union bpf_object Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 14/22] bpf/cgroup: Make cgroup_bpf_update() return an error code Mickaël Salaün
2016-09-14 21:16 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 15/22] bpf/cgroup: Move capability check Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 16/22] bpf/cgroup,landlock: Handle Landlock hooks per cgroup Mickaël Salaün
2016-10-03 23:43 ` [kernel-hardening] " Kees Cook
2016-10-05 20:58 ` Mickaël Salaün
2016-10-05 21:25 ` Kees Cook
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 17/22] cgroup: Add access check for cgroup_get_from_fd() Mickaël Salaün
2016-09-14 22:06 ` [kernel-hardening] " Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks Mickaël Salaün
2016-09-14 18:27 ` [kernel-hardening] " Andy Lutomirski
2016-09-14 22:11 ` Mickaël Salaün
2016-09-15 1:25 ` Andy Lutomirski
2016-09-15 2:19 ` Alexei Starovoitov
2016-09-15 2:27 ` Andy Lutomirski [this message]
2016-09-15 4:00 ` Alexei Starovoitov
2016-09-15 4:08 ` Andy Lutomirski
2016-09-15 4:31 ` Alexei Starovoitov
2016-09-15 4:38 ` Andy Lutomirski
2016-09-15 4:48 ` Alexei Starovoitov
2016-09-15 19:41 ` Mickaël Salaün
2016-09-20 4:37 ` Sargun Dhillon
2016-09-20 17:02 ` Mickaël Salaün
2016-09-15 19:35 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 19/22] landlock: Add interrupted origin Mickaël Salaün
2016-09-14 18:29 ` [kernel-hardening] " Andy Lutomirski
2016-09-14 22:14 ` Mickaël Salaün
2016-09-15 1:19 ` Andy Lutomirski
2016-10-03 23:46 ` Kees Cook
2016-10-05 21:01 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 20/22] landlock: Add update and debug access flags Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 21/22] bpf,landlock: Add optional skb pointer in the Landlock context Mickaël Salaün
2016-09-14 21:20 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 22:46 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 22/22] samples/landlock: Add sandbox example Mickaël Salaün
2016-09-14 21:24 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 14:36 ` [kernel-hardening] RE: [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing David Laight
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