From: Casey Schaufler <casey@schaufler-ca.com>
To: Frederick Lawler <fred@cloudflare.com>,
Paul Moore <paul@paul-moore.com>,
Daniel Borkmann <daniel@iogearbox.net>
Cc: Christian Brauner <brauner@kernel.org>,
kpsingh@kernel.org, revest@chromium.org, jackmanb@chromium.org,
ast@kernel.org, andrii@kernel.org, kafai@fb.com,
songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com,
jmorris@namei.org, serge@hallyn.com, bpf@vger.kernel.org,
linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@cloudflare.com,
Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH 0/2] Introduce security_create_user_ns()
Date: Tue, 28 Jun 2022 09:02:13 -0700 [thread overview]
Message-ID: <d70d3b2d-6c3f-b1fc-f40c-f5ec01a627c0@schaufler-ca.com> (raw)
In-Reply-To: <9ae473c4-cd42-bb45-bce2-8aa2e4784a43@cloudflare.com>
On 6/28/2022 8:14 AM, Frederick Lawler wrote:
> On 6/27/22 6:18 PM, Casey Schaufler wrote:
>> On 6/27/2022 3:27 PM, Paul Moore wrote:
>>> On Mon, Jun 27, 2022 at 6:15 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>>>> On 6/27/22 11:56 PM, Paul Moore wrote:
>>>>> On Mon, Jun 27, 2022 at 8:11 AM Christian Brauner <brauner@kernel.org> wrote:
>>>>>> On Thu, Jun 23, 2022 at 11:21:37PM -0400, Paul Moore wrote:
>>>>> ...
>>>>>
>>>>>>> This is one of the reasons why I usually like to see at least one LSM
>>>>>>> implementation to go along with every new/modified hook. The
>>>>>>> implementation forces you to think about what information is necessary
>>>>>>> to perform a basic access control decision; sometimes it isn't always
>>>>>>> obvious until you have to write the access control :)
>>>>>> I spoke to Frederick at length during LSS and as I've been given to
>>>>>> understand there's a eBPF program that would immediately use this new
>>>>>> hook. Now I don't want to get into the whole "Is the eBPF LSM hook
>>>>>> infrastructure an LSM" but I think we can let this count as a legitimate
>>>>>> first user of this hook/code.
>>>>> Yes, for the most part I don't really worry about the "is a BPF LSM a
>>>>> LSM?" question, it's generally not important for most discussions.
>>>>> However, there is an issue unique to the BPF LSMs which I think is
>>>>> relevant here: there is no hook implementation code living under
>>>>> security/. While I talked about a hook implementation being helpful
>>>>> to verify the hook prototype, it is also helpful in providing an
>>>>> in-tree example for other LSMs; unfortunately we don't get that same
>>>>> example value when the initial hook implementation is a BPF LSM.
>>>> I would argue that such a patch series must come together with a BPF
>>>> selftest which then i) contains an in-tree usage example, ii) adds BPF
>>>> CI test coverage. Shipping with a BPF selftest at least would be the
>>>> usual expectation.
>>> I'm not going to disagree with that, I generally require matching
>>> tests for new SELinux kernel code, but I was careful to mention code
>>> under 'security/' and not necessarily just a test implementation :) I
>>> don't want to get into a big discussion about it, but I think having a
>>> working implementation somewhere under 'security/' is more
>>> discoverable for most LSM folks.
>>
>> I agree. It would be unfortunate if we added a hook explicitly for eBPF
>> only to discover that the proposed user needs something different. The
>> LSM community should have a chance to review the code before committing
>> to all the maintenance required in supporting it.
>>
>> Is there a reference on how to write an eBPF security module?
>
> There's a documentation page that briefly touches on a BPF LSM implementation [1].
That's a brief touch, alright. I'll grant that the LSM interface isn't
especially well documented for C developers, but we have done tutorials
and have multiple examples. I worry that without an in-tree example for
eBPF we might well be setting developers up for spectacular failure.
>
>> There should be something out there warning the eBPF programmer of the
>> implications of providing a secid_to_secctx hook for starters.
>>
>
> Links:
> 1. https://docs.kernel.org/bpf/prog_lsm.html?highlight=bpf+lsm#
>
next prev parent reply other threads:[~2022-06-28 16:03 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-21 23:39 [PATCH 0/2] Introduce security_create_user_ns() Frederick Lawler
2022-06-21 23:39 ` [PATCH 1/2] security, lsm: " Frederick Lawler
2022-06-21 23:39 ` [PATCH 2/2] bpf-lsm: Make bpf_lsm_create_user_ns() sleepable Frederick Lawler
2022-06-22 0:19 ` [PATCH 0/2] Introduce security_create_user_ns() Casey Schaufler
2022-06-22 14:24 ` Frederick Lawler
2022-06-22 15:26 ` Casey Schaufler
2022-06-22 15:26 ` Casey Schaufler
2022-06-24 3:21 ` Paul Moore
2022-06-27 12:11 ` Christian Brauner
2022-06-27 15:51 ` Frederick Lawler
2022-06-27 15:56 ` Christian Brauner
2022-06-27 17:24 ` Casey Schaufler
2022-06-27 22:13 ` Paul Moore
2022-06-27 21:56 ` Paul Moore
2022-06-27 22:15 ` Daniel Borkmann
2022-06-27 22:27 ` KP Singh
2022-06-27 22:27 ` Paul Moore
2022-06-27 23:18 ` Casey Schaufler
2022-06-28 15:14 ` Frederick Lawler
2022-06-28 16:02 ` Casey Schaufler [this message]
2022-06-28 16:12 ` KP Singh
2022-06-28 16:44 ` Frederick Lawler
2022-06-28 15:11 ` Frederick Lawler
2022-06-28 15:13 ` Paul Moore
2022-06-30 18:28 ` Eric W. Biederman
2022-07-01 3:47 ` Frederick Lawler
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d70d3b2d-6c3f-b1fc-f40c-f5ec01a627c0@schaufler-ca.com \
--to=casey@schaufler-ca.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=brauner@kernel.org \
--cc=daniel@iogearbox.net \
--cc=fred@cloudflare.com \
--cc=jackmanb@chromium.org \
--cc=jmorris@namei.org \
--cc=john.fastabend@gmail.com \
--cc=kafai@fb.com \
--cc=kernel-team@cloudflare.com \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=paul@paul-moore.com \
--cc=revest@chromium.org \
--cc=serge@hallyn.com \
--cc=songliubraving@fb.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).