From: KP Singh <kpsingh@chromium.org>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: "KP Singh" <kpsingh@chromium.org>,
"James Morris" <jmorris@namei.org>,
"Kees Cook" <keescook@chromium.org>,
"Casey Schaufler" <casey@schaufler-ca.com>,
"open list" <linux-kernel@vger.kernel.org>,
bpf <bpf@vger.kernel.org>,
linux-security-module@vger.kernel.org,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Thomas Garnier" <thgarnie@chromium.org>,
"Michael Halcrow" <mhalcrow@google.com>,
"Paul Turner" <pjt@google.com>,
"Brendan Gregg" <brendan.d.gregg@gmail.com>,
"Jann Horn" <jannh@google.com>,
"Matthew Garrett" <mjg59@google.com>,
"Christian Brauner" <christian@brauner.io>,
"Mickaël Salaün" <mic@digikod.net>,
"Florent Revest" <revest@chromium.org>,
"Brendan Jackman" <jackmanb@chromium.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
"Mauro Carvalho Chehab" <mchehab+samsung@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Nicolas Ferre" <nicolas.ferre@microchip.com>,
"Stanislav Fomichev" <sdf@google.com>,
"Quentin Monnet" <quentin.monnet@netronome.com>,
"Andrey Ignatov" <rdna@fb.com>, "Joe Stringer" <joe@wand.net.nz>,
"Paul Moore" <paul@paul-moore.com>
Subject: Re: [PATCH bpf-next v1 00/13] MAC and Audit policy using eBPF (KRSI)
Date: Fri, 10 Jan 2020 16:27:58 +0100 [thread overview]
Message-ID: <20200110152758.GA260168@google.com> (raw)
In-Reply-To: <8e035f4d-5120-de6a-7ac8-a35841a92b8a@tycho.nsa.gov>
On 09-Jan 14:47, Stephen Smalley wrote:
> On 1/9/20 2:43 PM, KP Singh wrote:
> > On 10-Jan 06:07, James Morris wrote:
> > > On Thu, 9 Jan 2020, Stephen Smalley wrote:
> > >
> > > > On 1/9/20 1:11 PM, James Morris wrote:
> > > > > On Wed, 8 Jan 2020, Stephen Smalley wrote:
> > > > >
> > > > > > The cover letter subject line and the Kconfig help text refer to it as a
> > > > > > BPF-based "MAC and Audit policy". It has an enforce config option that
> > > > > > enables the bpf programs to deny access, providing access control. IIRC,
> > > > > > in
> > > > > > the earlier discussion threads, the BPF maintainers suggested that Smack
> > > > > > and
> > > > > > other LSMs could be entirely re-implemented via it in the future, and that
> > > > > > such an implementation would be more optimal.
> > > > >
> > > > > In this case, the eBPF code is similar to a kernel module, rather than a
> > > > > loadable policy file. It's a loadable mechanism, rather than a policy, in
> > > > > my view.
> > > >
> > > > I thought you frowned on dynamically loadable LSMs for both security and
> > > > correctness reasons?
> >
> > Based on the feedback from the lists we've updated the design for v2.
> >
> > In v2, LSM hook callbacks are allocated dynamically using BPF
> > trampolines, appended to a separate security_hook_heads and run
> > only after the statically allocated hooks.
> >
> > The security_hook_heads for all the other LSMs (SELinux, AppArmor etc)
> > still remains __lsm_ro_after_init and cannot be modified. We are still
> > working on v2 (not ready for review yet) but the general idea can be
> > seen here:
> >
> > https://github.com/sinkap/linux-krsi/blob/patch/v1/trampoline_prototype/security/bpf/lsm.c
> >
> > >
> > > Evaluating the security impact of this is the next step. My understanding
> > > is that eBPF via BTF is constrained to read only access to hook
> > > parameters, and that its behavior would be entirely restrictive.
> > >
> > > I'd like to understand the security impact more fully, though. Can the
> > > eBPF code make arbitrary writes to the kernel, or read anything other than
> > > the correctly bounded LSM hook parameters?
> > >
> >
> > As mentioned, the BPF verifier does not allow writes to BTF types.
> >
> > > > And a traditional security module would necessarily fall
> > > > under GPL; is the eBPF code required to be likewise? If not, KRSI is a
> > > > gateway for proprietary LSMs...
> > >
> > > Right, we do not want this to be a GPL bypass.
> >
> > This is not intended to be a GPL bypass and the BPF verifier checks
> > for license compatibility of the loaded program with GPL.
>
> IIUC, it checks that the program is GPL compatible if it uses a function
> marked GPL-only. But what specifically is marked GPL-only that is required
> for eBPF programs using KRSI?
Good point! If no-one objects, I can add it to the BPF_PROG_TYPE_LSM
specific verification for the v2 of the patch-set which would require
all BPF-LSM programs to be GPL.
- KP
>
> >
> > - KP
> >
> > >
> > > If these issues can be resolved, this may be a "safe" way to support
> > > loadable LSM applications.
> > >
> > > Again, I'd be interested in knowing how this is is handled in the
> > > networking stack (keeping in mind that LSM is a much more invasive API,
> > > and may not be directly comparable).
> > >
> > > --
> > > James Morris
> > > <jmorris@namei.org>
> > >
>
next prev parent reply other threads:[~2020-01-10 15:28 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 15:41 [PATCH bpf-next v1 00/13] MAC and Audit policy using eBPF (KRSI) KP Singh
2019-12-20 15:41 ` [PATCH bpf-next v1 01/13] bpf: Refactor BPF_EVENT context macros to its own header KP Singh
2019-12-20 20:10 ` Andrii Nakryiko
2019-12-20 20:26 ` KP Singh
2019-12-20 15:41 ` [PATCH bpf-next v1 02/13] bpf: lsm: Add a skeleton and config options KP Singh
2020-01-07 21:13 ` James Morris
2019-12-20 15:41 ` [PATCH bpf-next v1 03/13] bpf: lsm: Introduce types for eBPF based LSM KP Singh
2019-12-20 15:41 ` [PATCH bpf-next v1 04/13] bpf: lsm: Allow btf_id based attachment for LSM hooks KP Singh
2019-12-23 23:54 ` Andrii Nakryiko
2019-12-30 19:22 ` KP Singh
2019-12-20 15:42 ` [PATCH bpf-next v1 05/13] tools/libbpf: Add support in libbpf for BPF_PROG_TYPE_LSM KP Singh
2019-12-24 0:07 ` Andrii Nakryiko
2019-12-24 0:09 ` Andrii Nakryiko
2020-01-03 23:59 ` KP Singh
2019-12-20 15:42 ` [PATCH bpf-next v1 06/13] bpf: lsm: Init Hooks and create files in securityfs KP Singh
2019-12-24 6:28 ` Andrii Nakryiko
2019-12-30 15:37 ` KP Singh
2019-12-30 18:52 ` Andrii Nakryiko
2019-12-30 19:20 ` Kees Cook
2020-01-03 23:53 ` KP Singh
2020-01-07 21:22 ` James Morris
2019-12-20 15:42 ` [PATCH bpf-next v1 07/13] bpf: lsm: Implement attach, detach and execution KP Singh
2019-12-24 5:48 ` Andrii Nakryiko
2020-01-07 21:27 ` James Morris
2019-12-20 15:42 ` [PATCH bpf-next v1 08/13] bpf: lsm: Show attached program names in hook read handler KP Singh
2020-01-07 21:28 ` James Morris
2019-12-20 15:42 ` [PATCH bpf-next v1 09/13] bpf: lsm: Add a helper function bpf_lsm_event_output KP Singh
2019-12-24 6:36 ` Andrii Nakryiko
2019-12-30 15:11 ` KP Singh
2019-12-30 18:56 ` Andrii Nakryiko
2019-12-20 15:42 ` [PATCH bpf-next v1 10/13] bpf: lsm: Handle attachment of the same program KP Singh
2019-12-24 6:38 ` Andrii Nakryiko
2020-01-08 18:21 ` James Morris
2019-12-20 15:42 ` [PATCH bpf-next v1 11/13] tools/libbpf: Add bpf_program__attach_lsm KP Singh
2019-12-24 6:44 ` Andrii Nakryiko
2020-01-08 18:24 ` James Morris
2019-12-20 15:42 ` [PATCH bpf-next v1 12/13] bpf: lsm: Add selftests for BPF_PROG_TYPE_LSM KP Singh
2019-12-24 6:49 ` Andrii Nakryiko
2020-01-04 0:09 ` KP Singh
2020-01-09 17:59 ` Andrii Nakryiko
2020-01-08 18:25 ` James Morris
2019-12-20 15:42 ` [PATCH bpf-next v1 13/13] bpf: lsm: Add Documentation KP Singh
2019-12-20 17:17 ` [PATCH bpf-next v1 00/13] MAC and Audit policy using eBPF (KRSI) Casey Schaufler
2019-12-20 17:38 ` KP Singh
2019-12-30 19:15 ` Kees Cook
2020-01-08 15:25 ` Stephen Smalley
2020-01-08 18:58 ` James Morris
2020-01-08 19:33 ` Stephen Smalley
2020-01-09 18:11 ` James Morris
2020-01-09 18:23 ` Greg Kroah-Hartman
2020-01-09 18:58 ` Stephen Smalley
2020-01-09 19:07 ` James Morris
2020-01-09 19:43 ` KP Singh
2020-01-09 19:47 ` Stephen Smalley
2020-01-10 15:27 ` KP Singh [this message]
2020-01-10 17:48 ` James Morris
2020-01-10 17:53 ` Alexei Starovoitov
2020-01-14 16:54 ` Stephen Smalley
2020-01-14 17:42 ` Stephen Smalley
2020-01-15 2:48 ` Alexei Starovoitov
2020-01-15 13:59 ` Stephen Smalley
2020-01-15 14:09 ` Greg Kroah-Hartman
2020-01-15 22:23 ` Alexei Starovoitov
2020-01-09 19:11 ` KP Singh
2020-01-08 18:27 ` James Morris
2019-12-20 22:46 ` Mickaël Salaün
2019-12-30 19:30 ` Kees Cook
2019-12-31 12:11 ` Mickaël Salaün
2019-12-22 1:27 ` Alexei Starovoitov
2019-12-30 14:58 ` KP Singh
2019-12-30 19:14 ` Andrii Nakryiko
2019-12-24 6:51 ` Andrii Nakryiko
2019-12-30 15:04 ` KP Singh
2019-12-30 18:58 ` Andrii Nakryiko
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