From: "Eric W. Biederman" <ebiederm@xmission.com>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: Paul Moore <paul@paul-moore.com>,
Frederick Lawler <fred@cloudflare.com>,
kpsingh@kernel.org, revest@chromium.org, jackmanb@chromium.org,
ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
john.fastabend@gmail.com, jmorris@namei.org, serge@hallyn.com,
stephen.smalley.work@gmail.com, eparis@parisplace.org,
shuah@kernel.org, brauner@kernel.org, bpf@vger.kernel.org,
linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, kernel-team@cloudflare.com,
cgzones@googlemail.com, karl@bigbadwolfsecurity.com
Subject: Re: [PATCH v4 0/4] Introduce security_create_user_ns()
Date: Tue, 09 Aug 2022 16:52:06 -0500 [thread overview]
Message-ID: <87bkstaxvd.fsf@email.froward.int.ebiederm.org> (raw)
In-Reply-To: <f38216d8-8ee4-d6fd-a5b1-0d21013e09c6@schaufler-ca.com> (Casey Schaufler's message of "Tue, 9 Aug 2022 10:43:30 -0700")
Casey Schaufler <casey@schaufler-ca.com> writes:
> Smack has no interest in using the proposed hook because user namespaces
> are neither subjects nor objects. They are collections of DAC and/or
> privilege configuration alternatives. Or something like that. From the
> viewpoint of a security module that only implements old fashioned MAC
> there is no value in constraining user namespaces.
The goal is to simply enable things that become safe when you don't have
to worry about confusing setuid executables.
> SELinux, on the other hand, seeks to be comprehensive well beyond
> controlling accesses between subjects and objects. Asking the question
> "should there be a control on this operation?" seems sufficient to justify
> adding the control to SELinux policy. This is characteristic of
> "Fine Grain" control.
I see that from a theoretical standpoint. On the flip side I prefer
arguments grounded in something more than what an abstract framework
could appreciate. We are so far from any theoretical purity in the
linux kernel that I can't see theoretical purity being enough to justify
a decision like this.
> So I'm of two minds on this. I don't need the hook, but I also understand
> why SELinux and BPF want it. I don't necessarily agree with their logic,
> but it is consistent with existing behavior. Any system that uses either
> of those security modules needs to be ready for unexpected denials based
> on any potential security concern. Keeping namespaces completely orthogonal
> to LSM seems doomed to failure eventually.
I can cross that bridge when there is a healthy conversation about such
a change.
Too often I get "ouch! Creating a user namespace was used as the easiest
way to exploit a security bug. Let's solve the issue by denying user
namespaces." Which leads to half thought out policies made out of fear.
Which is where I think this conversation started. I haven't seen it
make it's way to any healthy reasons to deny user namespaces yet.
Eric
next prev parent reply other threads:[~2022-08-09 21:52 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-01 18:01 [PATCH v4 0/4] Introduce security_create_user_ns() Frederick Lawler
2022-08-01 18:01 ` [PATCH v4 1/4] security, lsm: " Frederick Lawler
2022-08-02 21:47 ` KP Singh
2022-08-03 13:13 ` Frederick Lawler
2022-08-01 18:01 ` [PATCH v4 2/4] bpf-lsm: Make bpf_lsm_userns_create() sleepable Frederick Lawler
2022-08-01 23:00 ` Alexei Starovoitov
2022-08-01 23:06 ` Paul Moore
2022-08-02 21:29 ` KP Singh
2022-08-01 18:01 ` [PATCH v4 3/4] selftests/bpf: Add tests verifying bpf lsm userns_create hook Frederick Lawler
2022-08-02 22:08 ` KP Singh
2022-08-01 18:01 ` [PATCH v4 4/4] selinux: Implement " Frederick Lawler
2022-08-02 2:56 ` [PATCH v4 0/4] Introduce security_create_user_ns() Eric W. Biederman
2022-08-03 2:10 ` Paul Moore
2022-08-08 18:56 ` Eric W. Biederman
2022-08-08 19:16 ` Paul Moore
2022-08-08 19:26 ` Eric W. Biederman
2022-08-08 19:43 ` Eric W. Biederman
2022-08-08 22:47 ` Paul Moore
2022-08-09 16:07 ` Eric W. Biederman
2022-08-09 16:47 ` Paul Moore
2022-08-09 21:40 ` Eric W. Biederman
2022-08-09 22:40 ` Paul Moore
2022-08-10 0:51 ` Alexei Starovoitov
2022-08-09 17:43 ` Casey Schaufler
2022-08-09 21:52 ` Eric W. Biederman [this message]
2022-08-08 19:49 ` Paul Moore
2022-08-09 16:40 ` Eric W. Biederman
2022-08-14 15:55 ` Serge E. Hallyn
2022-08-15 2:32 ` Paul Moore
2022-08-15 15:41 ` Serge E. Hallyn
2022-08-15 16:24 ` Paul Moore
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