From: Kees Cook <keescook@chromium.org>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: Casey Schaufler <casey@schaufler-ca.com>,
LKML <linux-kernel@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
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>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Michael Kerrisk <mtk.manpages@gmail.com>,
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@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Linux API <linux-api@vger.kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>
Subject: [kernel-hardening] Re: [PATCH net-next v6 04/11] landlock: Add LSM hooks related to filesystem
Date: Wed, 19 Apr 2017 18:48:47 -0700 [thread overview]
Message-ID: <CAGXu5jJCvJ6-uZ=Kfhh3xD7UvaY+G99e9NXFMzvi=9OQzA6Ecg@mail.gmail.com> (raw)
In-Reply-To: <35272f2b-ec5f-d032-ae2e-9fc0b4c0e2e3@digikod.net>
On Wed, Apr 19, 2017 at 3:03 PM, Mickaël Salaün <mic@digikod.net> wrote:
>
> On 19/04/2017 01:40, Kees Cook wrote:
>> On Tue, Apr 18, 2017 at 4:16 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>>> On 4/18/2017 3:44 PM, Mickaël Salaün wrote:
>>>> On 19/04/2017 00:17, Kees Cook wrote:
>>>>> On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@digikod.net> wrote:
>>>>>> +void __init landlock_add_hooks(void)
>>>>>> +{
>>>>>> + pr_info("landlock: Version %u", LANDLOCK_VERSION);
>>>>>> + landlock_add_hooks_fs();
>>>>>> + security_add_hooks(NULL, 0, "landlock");
>>>>>> + bpf_register_prog_type(&bpf_landlock_type);
>>>>> I'm confused by the separation of hook registration here. The call to
>>>>> security_add_hooks is with count=0 is especially weird. Why isn't this
>>>>> just a single call with security_add_hooks(landlock_hooks,
>>>>> ARRAY_SIZE(landlock_hooks), "landlock")?
>>>> Yes, this is ugly with the new security_add_hooks() with three arguments
>>>> but I wanted to split the hooks definition in multiple files.
>>>
>>> Why? I'll buy a good argument, but there are dangers in
>>> allowing multiple calls to security_add_hooks().
>
> I prefer to have one file per hook "family" (e.g. filesystem, network,
> ptrace…). This reduce the mess with all the included files (needed for
> LSM hook argument types) and make the files easier to read, understand
> and maintain.
>
>>>
>>>>
>>>> The current security_add_hooks() use lsm_append(lsm, &lsm_names) which
>>>> is not exported. Unfortunately, calling multiple security_add_hooks()
>>>> with the same LSM name would register multiple names for the same LSM…
>>>> Is it OK if I modify this function to not add duplicated entries?
>>>
>>> It may seem absurd, but it's conceivable that a module might
>>> have two hooks it wants called. My example is a module that
>>> counts the number of times SELinux denies a process access to
>>> things (which needs to be called before and after SELinux in
>>> order to detect denials) and takes "appropriate action" if
>>> too many denials occur. It would be weird, wonky and hackish,
>>> but that never stopped anybody before.
>
> Right, but now, with the new lsm_append(), module names are concatenated
> ("%s,%s") in the lsm_names variable. It would be nice to not pollute
> this string with multiple time the same module name.
Perhaps security_add_hooks could be modified to accept a NULL lsm to
skip the lsm_append() call, so it could do:
security_add_hooks(hooks1, count1, NULL);
security_add_hooks(hooks2, count2, NULL);
security_add_hooks(NULL, 0, "landlock");
Or, as Casey suggests, disregard adding the name when it already exists:
security_add_hooks(hooks1, count1, "landlock");
security_add_hooks(hooks2, count2, "landlock");
Yeah, I think I prefer this...
-Kees
>
>>
>> If ends up being sane and clear, I'm fine with allowing multiple calls.
>>
>> -Kees
>>
>
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2017-04-20 1:48 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-28 23:46 [kernel-hardening] [PATCH net-next v6 00/11] Landlock LSM: Toward unprivileged sandboxing Mickaël Salaün
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 01/11] bpf: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2017-03-29 13:48 ` [kernel-hardening] " kbuild test robot
2017-04-18 21:48 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 02/11] bpf,landlock: Define an eBPF program type for Landlock Mickaël Salaün
2017-04-16 21:57 ` [kernel-hardening] " Mickaël Salaün
2017-04-18 21:58 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 03/11] bpf: Define handle_fs and add a new helper bpf_handle_fs_get_mode() Mickaël Salaün
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 04/11] landlock: Add LSM hooks related to filesystem Mickaël Salaün
2017-03-29 15:18 ` [kernel-hardening] " kbuild test robot
2017-04-18 22:17 ` Kees Cook
2017-04-18 22:44 ` Mickaël Salaün
2017-04-18 23:16 ` Casey Schaufler
2017-04-18 23:40 ` Kees Cook
2017-04-19 22:03 ` Mickaël Salaün
2017-04-19 23:58 ` Casey Schaufler
2017-04-20 1:48 ` Kees Cook [this message]
2017-04-18 23:39 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 05/11] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün
2017-04-18 22:23 ` [kernel-hardening] " Kees Cook
2017-04-18 22:47 ` Mickaël Salaün
2017-04-19 22:18 ` Mickaël Salaün
2017-04-20 1:54 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 06/11] seccomp,landlock: Handle Landlock events per process hierarchy Mickaël Salaün
2017-03-29 10:35 ` Djalal Harouni
2017-03-31 21:15 ` Mickaël Salaün
2017-04-18 22:54 ` Kees Cook
2017-04-18 22:53 ` [kernel-hardening] " Kees Cook
2017-04-18 23:24 ` Mickaël Salaün
2017-04-18 23:48 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 07/11] landlock: Add ptrace restrictions Mickaël Salaün
2017-04-10 6:48 ` Djalal Harouni
2017-04-11 7:19 ` Mickaël Salaün
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 08/11] bpf: Add a Landlock sandbox example Mickaël Salaün
2017-04-18 23:06 ` [kernel-hardening] " Kees Cook
2017-04-18 23:35 ` Mickaël Salaün
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 09/11] seccomp: Enhance test_harness with an assert step mechanism Mickaël Salaün
2017-04-19 0:02 ` [kernel-hardening] " Kees Cook
2017-04-19 21:51 ` Mickaël Salaün
2017-04-19 22:02 ` Kees Cook
2017-04-19 22:05 ` Mickaël Salaün
2017-04-20 1:50 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 10/11] bpf,landlock: Add tests for Landlock Mickaël Salaün
2017-04-18 23:16 ` [kernel-hardening] " Kees Cook
2017-04-18 23:53 ` Mickaël Salaün
2017-04-18 23:59 ` Kees Cook
2017-03-28 23:46 ` [kernel-hardening] [PATCH net-next v6 11/11] landlock: Add user and kernel documentation " Mickaël Salaün
2017-03-29 15:58 ` [kernel-hardening] " kbuild test robot
2017-04-18 23:26 ` [kernel-hardening] Re: [PATCH net-next v6 00/11] Landlock LSM: Toward unprivileged sandboxing Kees Cook
2017-04-19 0:12 ` Mickaël Salaün
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