netdev - Re: [PATCH bpf-next v8 08/11] landlock: Add ptrace restrictions

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Message-ID: <CALCETrW5v1sa17jPJuTskW5vdvcXqjFtRvAd0auWBmKvnAX-zQ@mail.gmail.com>
Date:   Wed, 28 Feb 2018 00:09:13 +0000
From:   Andy Lutomirski <luto@...nel.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <james.l.morris@...cle.com>,
        Jann Horn <jann@...jh.net>, Jonathan Corbet <corbet@....net>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <paul@...l-moore.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Shuah Khan <shuah@...nel.org>, Tejun Heo <tj@...nel.org>,
        Thomas Graf <tgraf@...g.ch>, Tycho Andersen <tycho@...ho.ws>,
        Will Drewry <wad@...omium.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v8 08/11] landlock: Add ptrace restrictions

On Wed, Feb 28, 2018 at 12:00 AM, Mickaël Salaün <mic@...ikod.net> wrote:
>
> On 28/02/2018 00:23, Andy Lutomirski wrote:
>> On Tue, Feb 27, 2018 at 11:02 PM, Andy Lutomirski <luto@...nel.org> wrote:
>>> On Tue, Feb 27, 2018 at 10:14 PM, Mickaël Salaün <mic@...ikod.net> wrote:
>>>>
>>>
>>> I think you're wrong here.  Any sane container trying to use Landlock
>>> like this would also create a PID namespace.  Problem solved.  I still
>>> think you should drop this patch.
>
> Containers is one use case, another is build-in sandboxing (e.g. for web
> browser…) and another one is for sandbox managers (e.g. Firejail,
> Bubblewrap, Flatpack…). In some of these use cases, especially from a
> developer point of view, you may want/need to debug your applications
> (without requiring to be root). For nested Landlock access-controls
> (e.g. container + user session + web browser), it may not be allowed to
> create a PID namespace, but you still want to have a meaningful
> access-control.
>

The consideration should be exactly the same as for normal seccomp.
If I'm in a container (using PID namespaces + seccomp) and a run a web
browser, I can debug the browser.

If there's a real use case for adding this type of automatic ptrace
protection, then by all means, let's add it as a general seccomp
feature.