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From: Andy Lutomirski <luto@amacapital.net>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Casey Schaufler <casey@schaufler-ca.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	David Drysdale <drysdale@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	James Morris <james.l.morris@oracle.com>,
	Jann Horn <jann@thejh.net>, Jonathan Corbet <corbet@lwn.net>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Paul Moore <paul@paul-moore.com>,
	Sargun Dhillon <sargun@sargun.me>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	Shuah Khan <shuah@kernel.org>, Tejun Heo <tj@kernel.org>,
	Thomas Graf <tgraf@suug.ch>, Tycho Andersen <tycho@tycho.ws>,
	Will Drewry <wad@chromium.org>,
	Kernel Hardening <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>
Subject: Re: [PATCH bpf-next v8 00/11] Landlock LSM: Toward unprivileged sandboxing
Date: Tue, 6 Mar 2018 22:33:17 +0000	[thread overview]
Message-ID: <CALCETrUQYp0ta4tLgUWJ79pZVwp3WRY7cp-XaPcn1WyTc=wZyg@mail.gmail.com> (raw)
In-Reply-To: <a70b41ee-78cb-52cc-152c-ac5e43b7e45c@digikod.net>

On Tue, Mar 6, 2018 at 10:25 PM, Mickaël Salaün <mic@digikod.net> wrote:
>
>
> On 28/02/2018 00:09, Andy Lutomirski wrote:
>> On Tue, Feb 27, 2018 at 10:03 PM, Mickaël Salaün <mic@digikod.net> wrote:
>>>
>>> On 27/02/2018 05:36, Andy Lutomirski wrote:
>>>> On Tue, Feb 27, 2018 at 12:41 AM, Mickaël Salaün <mic@digikod.net> wrote:
>>>>> Hi,
>>>>>
>>
>>>>>
>>>>> ## Why use the seccomp(2) syscall?
>>>>>
>>>>> Landlock use the same semantic as seccomp to apply access rule
>>>>> restrictions. It add a new layer of security for the current process
>>>>> which is inherited by its children. It makes sense to use an unique
>>>>> access-restricting syscall (that should be allowed by seccomp filters)
>>>>> which can only drop privileges. Moreover, a Landlock rule could come
>>>>> from outside a process (e.g.  passed through a UNIX socket). It is then
>>>>> useful to differentiate the creation/load of Landlock eBPF programs via
>>>>> bpf(2), from rule enforcement via seccomp(2).
>>>>
>>>> This seems like a weak argument to me.  Sure, this is a bit different
>>>> from seccomp(), and maybe shoving it into the seccomp() multiplexer is
>>>> awkward, but surely the bpf() multiplexer is even less applicable.
>>>
>>> I think using the seccomp syscall is fine, and everyone agreed on it.
>>>
>>
>> Ah, sorry, I completely misread what you wrote.  My apologies.  You
>> can disregard most of my email.
>>
>>>
>>>>
>>>> Also, looking forward, I think you're going to want a bunch of the
>>>> stuff that's under consideration as new seccomp features.  Tycho is
>>>> working on a "user notifier" feature for seccomp where, in addition to
>>>> accepting, rejecting, or kicking to ptrace, you can send a message to
>>>> the creator of the filter and wait for a reply.  I think that Landlock
>>>> will want exactly the same feature.
>>>
>>> I don't think why this may be useful at all her. Landlock does not
>>> filter at the syscall level but handles kernel object and actions as
>>> does an LSM. That is the whole purpose of Landlock.
>>
>> Suppose I'm writing a container manager.  I want to run "mount" in the
>> container, but I don't want to allow moun() in general and I want to
>> emulate certain mount() actions.  I can write a filter that catches
>> mount using seccomp and calls out to the container manager for help.
>> This isn't theoretical -- Tycho wants *exactly* this use case to be
>> supported.
>
> Well, I think this use case should be handled with something like
> LD_PRELOAD and a helper library. FYI, I did something like this:
> https://github.com/stemjail/stemshim

I doubt that will work for containers.  Containers that use user
namespaces and, for example, setuid programs aren't going to honor
LD_PRELOAD.

>
> Otherwise, we should think about enabling a process to (dynamically)
> extend/patch the vDSO (similar to LD_PRELOAD but at the syscall level
> and works with static binaries) for a subset of processes (the same way
> seccomp filters are inherited). It may be more powerful and flexible
> than extending the kernel/seccomp to patch (buggy?) userland.

Egads!

  reply	other threads:[~2018-03-06 22:33 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-27  0:41 Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 01/11] fs,security: Add a security blob to nameidata Mickaël Salaün
2018-02-27  0:57   ` Al Viro
2018-02-27  1:23     ` Al Viro
2018-03-11 20:14       ` Mickaël Salaün
2018-02-28 16:27   ` kbuild test robot
2018-02-28 16:58   ` kbuild test robot
2018-02-27  0:41 ` [PATCH bpf-next v8 02/11] fs,security: Add a new file access type: MAY_CHROOT Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 03/11] bpf: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 04/11] bpf,landlock: Define an eBPF program type for Landlock hooks Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 05/11] seccomp,landlock: Enforce Landlock programs per process hierarchy Mickaël Salaün
2018-02-27  2:08   ` Alexei Starovoitov
2018-02-27  4:40     ` Andy Lutomirski
2018-02-27  4:54       ` Alexei Starovoitov
2018-02-27  5:20         ` Andy Lutomirski
2018-02-27  5:32           ` Alexei Starovoitov
2018-02-27 16:39             ` Andy Lutomirski
2018-02-27 17:30               ` Casey Schaufler
2018-02-27 17:36                 ` Andy Lutomirski
2018-02-27 18:03                   ` Casey Schaufler
2018-02-27 21:48               ` Mickaël Salaün
2018-04-08 13:13                 ` Mickaël Salaün
2018-04-08 21:06                   ` Andy Lutomirski
2018-04-08 22:01                     ` Mickaël Salaün
2018-04-10  4:48                       ` Alexei Starovoitov
2018-04-11 22:18                         ` Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 06/11] bpf,landlock: Add a new map type: inode Mickaël Salaün
2018-02-28 17:35   ` kbuild test robot
2018-02-27  0:41 ` [PATCH bpf-next v8 07/11] landlock: Handle filesystem access control Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 08/11] landlock: Add ptrace restrictions Mickaël Salaün
2018-02-27  4:17   ` Andy Lutomirski
2018-02-27  5:01     ` Andy Lutomirski
2018-02-27 22:14       ` Mickaël Salaün
2018-02-27 23:02         ` Andy Lutomirski
2018-02-27 23:23           ` Andy Lutomirski
2018-02-28  0:00             ` Mickaël Salaün
2018-02-28  0:09               ` Andy Lutomirski
2018-03-06 22:28                 ` Mickaël Salaün
2018-04-01 22:48                   ` Mickaël Salaün
2018-02-27 22:18     ` Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 09/11] bpf: Add a Landlock sandbox example Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 10/11] bpf,landlock: Add tests for Landlock Mickaël Salaün
2018-02-27  0:41 ` [PATCH bpf-next v8 11/11] landlock: Add user and kernel documentation " Mickaël Salaün
2018-02-27  4:36 ` [PATCH bpf-next v8 00/11] Landlock LSM: Toward unprivileged sandboxing Andy Lutomirski
2018-02-27 22:03   ` Mickaël Salaün
2018-02-27 23:09     ` Andy Lutomirski
2018-03-06 22:25       ` Mickaël Salaün
2018-03-06 22:33         ` Andy Lutomirski [this message]
2018-03-06 22:46           ` Tycho Andersen
2018-03-06 23:06             ` Mickaël Salaün
2018-03-07  1:21               ` Andy Lutomirski
2018-03-08 23:51                 ` Mickaël Salaün
2018-03-08 23:53                   ` Andy Lutomirski
2018-04-01 22:04                     ` Mickaël Salaün
2018-04-02  0:39                       ` Tycho Andersen

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