From: Casey Schaufler <casey@schaufler-ca.com>
To: Stephen Smalley <stephen.smalley.work@gmail.com>,
KP Singh <kpsingh@chromium.org>
Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
LSM List <linux-security-module@vger.kernel.org>,
Brendan Jackman <jackmanb@google.com>,
Florent Revest <revest@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
James Morris <jmorris@namei.org>,
Kees Cook <keescook@chromium.org>, Paul Turner <pjt@google.com>,
Jann Horn <jannh@google.com>,
Florent Revest <revest@chromium.org>,
Brendan Jackman <jackmanb@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Paul Moore <paul@paul-moore.com>,
Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH bpf-next v5 4/7] bpf: lsm: Implement attach, detach and execution
Date: Tue, 24 Mar 2020 09:25:06 -0700 [thread overview]
Message-ID: <d578d19f-1d3b-f60d-f803-2fcb46721a4a@schaufler-ca.com> (raw)
In-Reply-To: <CAEjxPJ4YnCCeQUTK36Ao550AWProHrkrW1a6K5RKuKYcPcfhyA@mail.gmail.com>
On 3/24/2020 7:58 AM, Stephen Smalley wrote:
> On Tue, Mar 24, 2020 at 10:50 AM KP Singh <kpsingh@chromium.org> wrote:
>> On 24-Mär 10:35, Stephen Smalley wrote:
>>> On Mon, Mar 23, 2020 at 12:46 PM KP Singh <kpsingh@chromium.org> wrote:
>>>> From: KP Singh <kpsingh@google.com>
>>>> diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
>>>> index 530d137f7a84..2a8131b640b8 100644
>>>> --- a/kernel/bpf/bpf_lsm.c
>>>> +++ b/kernel/bpf/bpf_lsm.c
>>>> @@ -9,6 +9,9 @@
>>>> #include <linux/btf.h>
>>>> #include <linux/lsm_hooks.h>
>>>> #include <linux/bpf_lsm.h>
>>>> +#include <linux/jump_label.h>
>>>> +#include <linux/kallsyms.h>
>>>> +#include <linux/bpf_verifier.h>
>>>>
>>>> /* For every LSM hook that allows attachment of BPF programs, declare a NOP
>>>> * function where a BPF program can be attached as an fexit trampoline.
>>>> @@ -27,6 +30,32 @@ noinline __weak void bpf_lsm_##NAME(__VA_ARGS__) {}
>>>> #include <linux/lsm_hook_names.h>
>>>> #undef LSM_HOOK
>>>>
>>>> +#define BPF_LSM_SYM_PREFX "bpf_lsm_"
>>>> +
>>>> +int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
>>>> + const struct bpf_prog *prog)
>>>> +{
>>>> + /* Only CAP_MAC_ADMIN users are allowed to make changes to LSM hooks
>>>> + */
>>>> + if (!capable(CAP_MAC_ADMIN))
>>>> + return -EPERM;
>>> I had asked before, and will ask again: please provide an explicit LSM
>>> hook for mediating whether one can make changes to the LSM hooks.
>>> Neither CAP_MAC_ADMIN nor CAP_SYS_ADMIN suffices to check this for SELinux.
>> What do you think about:
>>
>> int security_check_mutable_hooks(void)
>>
>> Do you have any suggestions on the signature of this hook? Does this
>> hook need to be BPF specific?
> I'd do something like int security_bpf_prog_attach_security(const
> struct bpf_prog *prog) or similar.
> Then the security module can do a check based on the current task
> and/or the prog. We already have some bpf-specific hooks.
I *strongly* disagree with Stephen on this. KRSI and SELinux are peers.
Just as Yama policy is independent of SELinux policy so KRSI policy should
be independent of SELinux policy. I understand the argument that BDF programs
ought to be constrained by SELinux, but I don't think it's right. Further,
we've got unholy layering when security modules call security_ functions.
I'm not saying there is no case where it would be appropriate, but this is not
one of them.
next prev parent reply other threads:[~2020-03-24 16:25 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-23 16:44 [PATCH bpf-next v5 0/8] MAC and Audit policy using eBPF (KRSI) KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 1/7] bpf: Introduce BPF_PROG_TYPE_LSM KP Singh
2020-03-23 19:02 ` Yonghong Song
2020-03-23 16:44 ` [PATCH bpf-next v5 2/7] security: Refactor declaration of LSM hooks KP Singh
2020-03-23 19:33 ` Kees Cook
2020-03-23 19:56 ` Andrii Nakryiko
2020-03-24 16:06 ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 3/7] bpf: lsm: provide attachment points for BPF LSM programs KP Singh
2020-03-23 19:04 ` Yonghong Song
2020-03-23 19:33 ` Kees Cook
2020-03-23 19:59 ` Andrii Nakryiko
2020-03-24 10:39 ` KP Singh
2020-03-24 16:12 ` KP Singh
2020-03-24 21:26 ` Andrii Nakryiko
2020-03-24 22:39 ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 4/7] bpf: lsm: Implement attach, detach and execution KP Singh
2020-03-23 19:16 ` Yonghong Song
2020-03-23 19:44 ` KP Singh
2020-03-23 20:18 ` Andrii Nakryiko
2020-03-24 19:00 ` KP Singh
2020-03-24 14:35 ` Stephen Smalley
2020-03-24 14:50 ` KP Singh
2020-03-24 14:58 ` Stephen Smalley
2020-03-24 16:25 ` Casey Schaufler [this message]
2020-03-24 17:49 ` Stephen Smalley
2020-03-24 18:01 ` Kees Cook
2020-03-24 18:06 ` KP Singh
2020-03-24 18:21 ` Stephen Smalley
2020-03-24 18:27 ` KP Singh
2020-03-24 18:31 ` KP Singh
2020-03-24 18:34 ` Kees Cook
2020-03-24 18:33 ` Kees Cook
2020-03-23 16:44 ` [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks KP Singh
2020-03-23 19:44 ` Kees Cook
2020-03-23 19:47 ` KP Singh
2020-03-23 20:21 ` Andrii Nakryiko
2020-03-23 20:47 ` Casey Schaufler
2020-03-23 21:44 ` Kees Cook
2020-03-23 21:58 ` Casey Schaufler
2020-03-23 22:12 ` Kees Cook
2020-03-23 23:39 ` Casey Schaufler
2020-03-24 1:53 ` KP Singh
2020-03-25 14:35 ` KP Singh
2020-03-24 1:13 ` Casey Schaufler
2020-03-24 1:52 ` KP Singh
2020-03-24 14:37 ` Stephen Smalley
2020-03-24 14:42 ` KP Singh
2020-03-24 14:51 ` Stephen Smalley
2020-03-24 14:51 ` KP Singh
2020-03-24 17:57 ` Kees Cook
2020-03-23 16:44 ` [PATCH bpf-next v5 6/7] tools/libbpf: Add support for BPF_PROG_TYPE_LSM KP Singh
2020-03-23 19:21 ` Yonghong Song
2020-03-23 20:25 ` Andrii Nakryiko
2020-03-24 1:57 ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 7/7] bpf: lsm: Add selftests " KP Singh
2020-03-23 20:04 ` Yonghong Song
2020-03-24 20:04 ` KP Singh
2020-03-24 23:54 ` Andrii Nakryiko
2020-03-25 0:36 ` KP Singh
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