Re: [PATCH v2 0/4] Introduce security_create_user_ns()

From: Casey Schaufler <casey@schaufler-ca.com>
To: Paul Moore <paul@paul-moore.com>
Cc: "Frederick Lawler" <fred@cloudflare.com>,
	"Christian Göttsche" <cgzones@googlemail.com>,
	"KP Singh" <kpsingh@kernel.org>,
	revest@chromium.org, jackmanb@chromium.org,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"James Morris" <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	"Stephen Smalley" <stephen.smalley.work@gmail.com>,
	"Eric Paris" <eparis@parisplace.org>,
	shuah@kernel.org, "Christian Brauner" <brauner@kernel.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	bpf@vger.kernel.org, linux-security-module@vger.kernel.org,
	"SElinux list" <selinux@vger.kernel.org>,
	linux-kselftest@vger.kernel.org,
	"Linux kernel mailing list" <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org, kernel-team@cloudflare.com,
	casey@schaufler-ca.com
Subject: Re: [PATCH v2 0/4] Introduce security_create_user_ns()
Date: Wed, 20 Jul 2022 14:42:11 -0700	[thread overview]
Message-ID: <f1f8b350-4dc5-b975-3854-ecbf9f4e54ba@schaufler-ca.com> (raw)
In-Reply-To: <CAHC9VhQ-mBYH-GwSULDyyQ6mNC6K8GNB4fra0pJ+s0ZnEpCgcg@mail.gmail.com>

On 7/19/2022 6:32 PM, Paul Moore wrote:
> On Fri, Jul 8, 2022 at 12:11 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> On 7/8/2022 7:01 AM, Frederick Lawler wrote:
>>> On 7/8/22 7:10 AM, Christian Göttsche wrote:
>>>> ,On Fri, 8 Jul 2022 at 00:32, Frederick Lawler <fred@cloudflare.com>
>>>> wrote:
> ..
>
>>>> Also I think the naming scheme is <object>_<verb>.
>>> That's a good call out. I was originally hoping to keep the
>>> security_*() match with the hook name matched with the caller function
>>> to keep things all aligned. If no one objects to renaming the hook, I
>>> can rename the hook for v3.
> No objection from me.
>
> [Sorry for the delay, the last week or two has been pretty busy.]
>
>>>> III.
>>>>
>>>> Maybe even attach a security context to namespaces so they can be
>>>> further governed?
>> That would likely add confusion to the existing security module namespace
>> efforts. SELinux, Smack and AppArmor have all developed namespace models.
> I'm not sure I fully understand what Casey is saying here as SELinux
> does not yet have an established namespace model to the best of my
> understanding, but perhaps we are talking about different concepts for
> the word "namespace"?

Stephen Smalley proposed a SELinux namespace model, with patches,
some time back. It hasn't been adopted, but I've seen at least one
attempt to revive it. You're right that there isn't an established
model. The model proposed for Smack wasn't adopted either. My point
is that models have been developed and refinements and/or alternatives
are likely to be suggested.

>
> >From a SELinux perspective, if we are going to control access to a
> namespace beyond simple creation, we would need to assign the
> namespace a label (inherited from the creating process).  Although
> that would need some discussion among the SELinux folks as this would
> mean treating a userns as a proper system entity from a policy
> perspective which is ... interesting.
>
>> That, or it could replace the various independent efforts with a single,
>> unified security module namespace effort.
> We've talked about this before and I just don't see how that could
> ever work, the LSM implementations are just too different to do
> namespacing at the LSM layer.

It's possible that fresh eyes might see options that those who have
been staring at the current state and historical proposals may have
missed.

>   If a LSM is going to namespace
> themselves, they need the ability to define what that means without
> having to worry about what other LSMs want to do.

Possibly. On the other hand, if someone came up with a rational scheme
for general xattr namespacing I don't see that anyone would pass it up.