From: Alexei Starovoitov <alexei.starovoitov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: "Mickaël Salaün" <mic-WFhQfpSGs3bR7s880joybQ@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Alexei Starovoitov <ast-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
Arnaldo Carvalho de Melo
<acme-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Casey Schaufler <casey-iSGtlc1asvQWG2LlvL+J4A@public.gmane.org>,
Daniel Borkmann <daniel-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>,
David Drysdale <drysdale-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
"David S . Miller"
<davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
"Eric W . Biederman"
<ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>,
James Morris
<james.l.morris-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
Jann Horn <jann-XZ1E9jl8jIdeoWH0uzbU5w@public.gmane.org>,
Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>,
Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>,
Michael Kerrisk
<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Paul Moore <paul-r2n+y4ga6xFZroRs9YW3xA@public.gmane.org>,
Sargun Dhillon <sargun-GaZTRHToo+CzQB+pC5nmwQ@public.gmane.org>,
"Serge E . Hallyn"
<serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org>,
Shuah Khan <shuah-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Thomas Graf <tgr>
Subject: Re: [PATCH net-next v7 08/10] bpf: Add a Landlock sandbox example
Date: Wed, 23 Aug 2017 19:59:02 -0700 [thread overview]
Message-ID: <20170824025901.cpppy4nn5xv2ao24@ast-mbp> (raw)
In-Reply-To: <20170821000933.13024-9-mic-WFhQfpSGs3bR7s880joybQ@public.gmane.org>
On Mon, Aug 21, 2017 at 02:09:31AM +0200, Mickaël Salaün wrote:
> Add a basic sandbox tool to create a process isolated from some part of
> the system. This sandbox create a read-only environment. It is only
> allowed to write to a character device such as a TTY:
>
> # :> X
> # echo $?
> 0
> # ./samples/bpf/landlock1 /bin/sh -i
> Launching a new sandboxed process.
> # :> Y
> cannot create Y: Operation not permitted
>
> Signed-off-by: Mickaël Salaün <mic-WFhQfpSGs3bR7s880joybQ@public.gmane.org>
...
> +SEC("landlock1")
> +static int landlock_fs_prog1(struct landlock_context *ctx)
> +{
> + char fmt_error_mode[] = "landlock1: error: get_mode:%lld\n";
> + char fmt_error_access[] = "landlock1: error: access denied\n";
> + long long ret;
> +
> + /*
> + * The argument ctx->arg2 contains bitflags of actions for which the
> + * rule is run. The flag LANDLOCK_ACTION_FS_WRITE means that a write
> + * is requested by one of the userspace processes restricted by this
> + * rule. The following test allows any actions which does not include a
> + * write.
> + */
> + if (!(ctx->arg2 & LANDLOCK_ACTION_FS_WRITE))
> + return 0;
> +
> + /*
> + * The argument ctx->arg1 is a file handle for which the process want
> + * to access. The function bpf_handle_fs_get_mode() return the mode of
> + * a file (e.g. S_IFBLK, S_IFDIR, S_IFREG...). If there is an error,
> + * for example if the argument is not a file handle, then an
> + * -errno value is returned. Otherwise the caller get the file mode as
> + * with stat(2).
> + */
> + ret = bpf_handle_fs_get_mode((void *)ctx->arg1);
> + if (ret < 0) {
> +
> + /*
> + * The bpf_trace_printk() function enable to write in the
> + * kernel eBPF debug log, accessible through
> + * /sys/kernel/debug/tracing/trace_pipe . To be allowed to call
> + * this function, a Landlock rule must have the
> + * LANDLOCK_SUBTYPE_ABILITY_DEBUG ability, which is only
> + * allowed for CAP_SYS_ADMIN.
> + */
> + bpf_trace_printk(fmt_error_mode, sizeof(fmt_error_mode), ret);
> + return 1;
> + }
> +
> + /*
> + * This check allows the action on the file if it is a directory or a
> + * pipe. Otherwise, a message is printed to the eBPF log.
> + */
> + if (S_ISCHR(ret) || S_ISFIFO(ret))
> + return 0;
> + bpf_trace_printk(fmt_error_access, sizeof(fmt_error_access));
> + return 1;
> +}
> +
> +/*
> + * This subtype enable to set the ABI, which ensure that the eBPF context and
> + * program behavior will be compatible with this Landlock rule.
> + */
> +SEC("subtype")
> +static const union bpf_prog_subtype _subtype = {
> + .landlock_rule = {
> + .abi = 1,
> + .event = LANDLOCK_SUBTYPE_EVENT_FS,
> + .ability = LANDLOCK_SUBTYPE_ABILITY_DEBUG,
> + }
> +};
from rule writer perspective can you somehow merge subtype definition
with the program? It seems they go hand in hand.
Like section name of the program can be:
SEC("landlock_rule1/event=fs/ability=debug")
static int landlock_fs_prog1(struct landlock_context *ctx)...
and the loader can parse this string and prepare appropriate
data structures for the kernel.
next prev parent reply other threads:[~2017-08-24 2:59 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-21 0:09 [PATCH net-next v7 00/10] Landlock LSM: Toward unprivileged sandboxing Mickaël Salaün
2017-08-21 0:09 ` [PATCH net-next v7 01/10] selftest: Enhance kselftest_harness.h with a step mechanism Mickaël Salaün
2017-08-24 2:31 ` Alexei Starovoitov
2017-08-25 7:58 ` Mickaël Salaün
2017-08-26 1:07 ` Alexei Starovoitov
2017-08-28 18:01 ` Shuah Khan
2017-08-21 0:09 ` [PATCH net-next v7 02/10] bpf: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2017-08-23 2:44 ` Alexei Starovoitov
2017-08-23 7:45 ` Mickaël Salaün
[not found] ` <607ceb21-5aa5-678b-4438-0d8dcb69fc3c-WFhQfpSGs3bR7s880joybQ@public.gmane.org>
2017-08-24 1:22 ` Alexei Starovoitov
2017-08-28 3:48 ` James Morris
2017-08-28 3:46 ` James Morris
2017-08-21 0:09 ` [PATCH net-next v7 03/10] bpf,landlock: Define an eBPF program type for a Landlock rule Mickaël Salaün
2017-08-24 2:28 ` Alexei Starovoitov
2017-08-25 8:02 ` Mickaël Salaün
2017-08-21 0:09 ` [PATCH net-next v7 04/10] bpf: Define handle_fs and add a new helper bpf_handle_fs_get_mode() Mickaël Salaün
2017-08-28 4:09 ` James Morris
2017-08-21 0:09 ` [PATCH net-next v7 05/10] landlock: Add LSM hooks related to filesystem Mickaël Salaün
2017-08-22 21:59 ` Mickaël Salaün
[not found] ` <20170821000933.13024-6-mic-WFhQfpSGs3bR7s880joybQ@public.gmane.org>
2017-08-24 2:50 ` Alexei Starovoitov
2017-08-25 8:16 ` Mickaël Salaün
2017-08-26 1:16 ` Alexei Starovoitov
2017-08-27 13:31 ` Mickaël Salaün
2017-08-28 5:26 ` Alexei Starovoitov
2017-08-21 0:09 ` [PATCH net-next v7 06/10] seccomp,landlock: Handle Landlock events per process hierarchy Mickaël Salaün
2017-08-21 0:09 ` [PATCH net-next v7 07/10] landlock: Add ptrace restrictions Mickaël Salaün
2017-08-21 0:09 ` [PATCH net-next v7 08/10] bpf: Add a Landlock sandbox example Mickaël Salaün
[not found] ` <20170821000933.13024-9-mic-WFhQfpSGs3bR7s880joybQ@public.gmane.org>
2017-08-24 2:59 ` Alexei Starovoitov [this message]
2017-08-25 8:17 ` Mickaël Salaün
2017-09-01 10:25 ` Alban Crequy
2017-09-02 13:19 ` Mickaël Salaün
2017-08-21 0:09 ` [PATCH net-next v7 09/10] bpf,landlock: Add tests for Landlock Mickaël Salaün
2017-08-21 0:09 ` [PATCH net-next v7 10/10] landlock: Add user and kernel documentation " Mickaël Salaün
2017-08-28 3:38 ` [PATCH net-next v7 00/10] Landlock LSM: Toward unprivileged sandboxing James Morris
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