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From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Casey Schaufler <casey@schaufler-ca.com>,
	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>,
	Kees Cook <keescook@chromium.org>,
	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, linux-api@vger.kernel.org,
	linux-security-module@vger.kernel.org, netdev@vger.kernel.org
Subject: [kernel-hardening] Re: [PATCH net-next v6 02/11] bpf,landlock: Define an eBPF program type for Landlock
Date: Sun, 16 Apr 2017 23:57:11 +0200
Message-ID: <2fbc99a6-f190-f335-bd14-04bdeed35571@digikod.net> (raw)
In-Reply-To: <20170328234650.19695-3-mic@digikod.net>

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On 29/03/2017 01:46, Mickaël Salaün wrote:
> Add a new type of eBPF program used by Landlock rules.
> 
> This new BPF program type will be registered with the Landlock LSM
> initialization.
> 
> Add an initial Landlock Kconfig.
> 
> Changes since v5:
> * rename file hooks.c to init.c
> * fix spelling
> 
> Changes since v4:
> * merge a minimal (not enabled) LSM code and Kconfig in this commit
> 
> Changes since v3:
> * split commit
> * revamp the landlock_context:
>   * add arch, syscall_nr and syscall_cmd (ioctl, fcntl…) to be able to
>     cross-check action with the event type
>   * replace args array with dedicated fields to ease the addition of new
>     fields
> 
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: James Morris <james.l.morris@oracle.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Serge E. Hallyn <serge@hallyn.com>
> ---
>  include/linux/landlock.h       |  23 ++++++++
>  include/uapi/linux/bpf.h       | 105 +++++++++++++++++++++++++++++++++++
>  security/Kconfig               |   1 +
>  security/Makefile              |   2 +
>  security/landlock/Kconfig      |  18 ++++++
>  security/landlock/Makefile     |   3 +
>  security/landlock/common.h     |  25 +++++++++
>  security/landlock/init.c       | 123 +++++++++++++++++++++++++++++++++++++++++
>  tools/include/uapi/linux/bpf.h | 105 +++++++++++++++++++++++++++++++++++
>  9 files changed, 405 insertions(+)
>  create mode 100644 include/linux/landlock.h
>  create mode 100644 security/landlock/Kconfig
>  create mode 100644 security/landlock/Makefile
>  create mode 100644 security/landlock/common.h
>  create mode 100644 security/landlock/init.c
>
[...]
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 0eb71ab9b4fd..619b1f8707cc 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -114,6 +114,7 @@ enum bpf_prog_type {
>  	BPF_PROG_TYPE_LWT_IN,
>  	BPF_PROG_TYPE_LWT_OUT,
>  	BPF_PROG_TYPE_LWT_XMIT,
> +	BPF_PROG_TYPE_LANDLOCK,
>  };
>  
>  enum bpf_attach_type {
> @@ -661,4 +662,108 @@ struct xdp_md {
>  	__u32 data_end;
>  };
>  
> +/**
> + * enum landlock_subtype_event - event occurring when an action is performed on
> + * a particular kernel object
> + *
> + * An event is a policy decision point which exposes the same context type
> + * (especially the same arg[0-9] field types) for each rule execution.
> + *
> + * @LANDLOCK_SUBTYPE_EVENT_UNSPEC: invalid value
> + * @LANDLOCK_SUBTYPE_EVENT_FS: generic filesystem event
> + */
> +enum landlock_subtype_event {
> +	LANDLOCK_SUBTYPE_EVENT_UNSPEC,
> +	LANDLOCK_SUBTYPE_EVENT_FS,
> +};
> +#define _LANDLOCK_SUBTYPE_EVENT_LAST LANDLOCK_SUBTYPE_EVENT_FS
[...]
> +/**
> + * DOC: landlock_action_fs
> + *
> + * - %LANDLOCK_ACTION_FS_EXEC: execute a file or walk through a directory
> + * - %LANDLOCK_ACTION_FS_WRITE: modify a file or a directory view (which
> + *   include mount actions)
> + * - %LANDLOCK_ACTION_FS_READ: read a file or a directory
> + * - %LANDLOCK_ACTION_FS_NEW: create a file or a directory
> + * - %LANDLOCK_ACTION_FS_GET: open or receive a file
> + * - %LANDLOCK_ACTION_FS_REMOVE: unlink a file or remove a directory
> + *
> + * Each of the following actions are specific to syscall multiplexers. They
> + * fill the syscall_cmd field from &struct landlock_context with their custom
> + * command.
> + *
> + * - %LANDLOCK_ACTION_FS_IOCTL: ioctl command
> + * - %LANDLOCK_ACTION_FS_LOCK: flock or fcntl lock command
> + * - %LANDLOCK_ACTION_FS_FCNTL: fcntl command
> + */
> +#define LANDLOCK_ACTION_FS_EXEC			(1ULL << 0)
> +#define LANDLOCK_ACTION_FS_WRITE		(1ULL << 1)
> +#define LANDLOCK_ACTION_FS_READ			(1ULL << 2)
> +#define LANDLOCK_ACTION_FS_NEW			(1ULL << 3)
> +#define LANDLOCK_ACTION_FS_GET			(1ULL << 4)
> +#define LANDLOCK_ACTION_FS_REMOVE		(1ULL << 5)
> +#define LANDLOCK_ACTION_FS_IOCTL		(1ULL << 6)
> +#define LANDLOCK_ACTION_FS_LOCK			(1ULL << 7)
> +#define LANDLOCK_ACTION_FS_FCNTL		(1ULL << 8)
> +#define _LANDLOCK_ACTION_FS_NB			9
> +#define _LANDLOCK_ACTION_FS_MASK		((1ULL << _LANDLOCK_ACTION_FS_NB) - 1)
> +
> +
> +/**
> + * struct landlock_context - context accessible to a Landlock rule
> + *
> + * @status: bitfield for future use (LANDLOCK_SUBTYPE_STATUS_*)
> + * @arch: indicates system call convention as an AUDIT_ARCH_* value
> + *        as defined in <linux/audit.h>
> + * @syscall_nr: the system call number called by the current process (may be
> + *              useful to debug: find out from which syscall this request came
> + *              from)
> + * @syscall_cmd: contains the command used by a multiplexer syscall (e.g.
> + *               ioctl, fcntl, flock)
> + * @event: event type (&enum landlock_subtype_event)
> + * @arg1: event's first optional argument
> + * @arg2: event's second optional argument
> + */
> +struct landlock_context {
> +	__u64 status;
> +	__u32 arch;
> +	__u32 syscall_nr;
> +	__u32 syscall_cmd;
> +	__u32 event;
> +	__u64 arg1;
> +	__u64 arg2;
> +};

I plan to simplify and make the FS event more generic for the IOCTL,
LOCK or FCNTL actions. The action flags for the
LANDLOCK_SUBTYPE_EVENT_FS event will remain the same but the syscall_cmd
field will be removed from struct landlock_context. Instead, one of
three dedicated events will be triggered in addition to one of this
three multiplexed actions.

The aim is to trigger the LANDLOCK_SUBTYPE_EVENT_FS for all file system
events (still including IOCTL/LOCK/FCNTL actions). This should avoid a
developer/user to forget such actions. However, when this kind of action
is triggered, a LANDLOCK_SUBTYPE_EVENT_FS_{IOCTL,LOCK,FCNTL} event will
follow. This enable to simplify the struct landlock_context while still
having it as generic as possible. The difference will be that the arg2
field for one of the LANDLOCK_SUBTYPE_EVENT_FS_{IOCTL,LOCK,FCNTL} events
will contain a custom IOCTL, LOCK or FCNTL command (currently in the
syscall_cmd field) instead of a LANDLOCK_ACTION_FS_* value. The same
logic could be used to tighten other actions in the future.

The HOOK_NEW_FS_CMD(...) from [04/11]:security/landlock/hooks_fs.c will
be replaced with dedicated calls.


I also plan to remove the arch and syscall_nr fields. This will make
struct landlock_context even more simple and arch-independent.


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  reply index

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   ` Mickaël Salaün [this message]
2017-04-18 21:58   ` [kernel-hardening] " 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
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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