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From: Andy Lutomirski <luto@amacapital.net>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: Tycho Andersen <tycho@tycho.ws>,
	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>, 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: Wed, 7 Mar 2018 01:21:11 +0000	[thread overview]
Message-ID: <CALCETrXT8JUXVwDNKGVRG7=aenthDRePD+T+YiDY6cceaazDeA@mail.gmail.com> (raw)
In-Reply-To: <7082be04-d6af-b853-4bb7-f331836662e2@digikod.net>

On Tue, Mar 6, 2018 at 11:06 PM, Mickaël Salaün <mic@digikod.net> wrote:
>
> On 06/03/2018 23:46, Tycho Andersen wrote:
>> On Tue, Mar 06, 2018 at 10:33:17PM +0000, Andy Lutomirski wrote:
>>>>> 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.
>>
>> Or anything that calls syscalls directly, like go programs.
>
> That's why the vDSO-like approach. Enforcing an access control is not
> the issue here, patching a buggy userland (without patching its code) is
> the issue isn't it?
>
> As far as I remember, the main problem is to handle file descriptors
> while "emulating" the kernel behavior. This can be done with a "shim"
> code mapped in every processes. Chrome used something like this (in a
> previous sandbox mechanism) as a kind of emulation (with the current
> seccomp-bpf ). I think it should be doable to replace the (userland)
> emulation code with an IPC wrapper receiving file descriptors through
> UNIX socket.
>

Can you explain exactly what you mean by "vDSO-like"?

When a 64-bit program does a syscall, it just executes the SYSCALL
instruction.  The vDSO isn't involved at all.  32-bit programs usually
go through the vDSO, but not always.

It could be possible to force-load a DSO into an entire container and
rig up seccomp to intercept all SYSCALLs not originating from the DSO
such that they merely redirect control to the DSO, but that seems
quite messy.

  reply	other threads:[~2018-03-07  1:21 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
2018-03-06 22:46           ` Tycho Andersen
2018-03-06 23:06             ` Mickaël Salaün
2018-03-07  1:21               ` Andy Lutomirski [this message]
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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