linux-kernel - Re: [PATCH v24 08/12] landlock: Add syscall implementations

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Date:   Sat, 21 Nov 2020 08:00:00 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...capital.net>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Arnd Bergmann <arnd@...db.de>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Jeff Dike <jdike@...toit.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Richard Weinberger <richard@....at>,
        Shuah Khan <shuah@...nel.org>,
        Vincent Dagonneau <vincent.dagonneau@....gouv.fr>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v24 08/12] landlock: Add syscall implementations

On Thu, Nov 12, 2020 at 9:52 PM Mickaël Salaün <mic@...ikod.net> wrote:
> These 3 system calls are designed to be used by unprivileged processes
> to sandbox themselves:
> * landlock_create_ruleset(2): Creates a ruleset and returns its file
>   descriptor.
> * landlock_add_rule(2): Adds a rule (e.g. file hierarchy access) to a
>   ruleset, identified by the dedicated file descriptor.
> * landlock_enforce_ruleset_current(2): Enforces a ruleset on the current
>   thread and its future children (similar to seccomp).  This syscall has
>   the same usage restrictions as seccomp(2): the caller must have the
>   no_new_privs attribute set or have CAP_SYS_ADMIN in the current user
>   namespace.
>
> All these syscalls have a "flags" argument (not currently used) to
> enable extensibility.
>
> Here are the motivations for these new syscalls:
> * A sandboxed process may not have access to file systems, including
>   /dev, /sys or /proc, but it should still be able to add more
>   restrictions to itself.
> * Neither prctl(2) nor seccomp(2) (which was used in a previous version)
>   fit well with the current definition of a Landlock security policy.
>
> All passed structs (attributes) are checked at build time to ensure that
> they don't contain holes and that they are aligned the same way for each
> architecture.
>
> See the user and kernel documentation for more details (provided by a
> following commit):
> * Documentation/userspace-api/landlock.rst
> * Documentation/security/landlock.rst
>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: James Morris <jmorris@...ei.org>
> Cc: Jann Horn <jannh@...gle.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Serge E. Hallyn <serge@...lyn.com>
> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>

Reviewed-by: Jann Horn <jannh@...gle.com>