From: "Mickaël Salaün" <mic@digikod.net>
To: Jann Horn <jannh@google.com>
Cc: "James Morris" <jmorris@namei.org>,
"Serge E . Hallyn" <serge@hallyn.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Andy Lutomirski" <luto@amacapital.net>,
"Anton Ivanov" <anton.ivanov@cambridgegreys.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Casey Schaufler" <casey@schaufler-ca.com>,
"Jeff Dike" <jdike@addtoit.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Kees Cook" <keescook@chromium.org>,
"Michael Kerrisk" <mtk.manpages@gmail.com>,
"Richard Weinberger" <richard@nod.at>,
"Shuah Khan" <shuah@kernel.org>,
"Vincent Dagonneau" <vincent.dagonneau@ssi.gouv.fr>,
"Kernel Hardening" <kernel-hardening@lists.openwall.com>,
"Linux API" <linux-api@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"kernel list" <linux-kernel@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
"Mickaël Salaün" <mic@linux.microsoft.com>
Subject: Re: [PATCH v22 12/12] landlock: Add user and kernel documentation
Date: Thu, 29 Oct 2020 12:38:26 +0100 [thread overview]
Message-ID: <de1a6799-1545-b9d9-915a-2d5184db001e@digikod.net> (raw)
In-Reply-To: <CAG48ez07p+BtCRo4D75S3xsr76Kj_9Aipv3pBHsc4zyNjEiEmQ@mail.gmail.com>
On 29/10/2020 02:07, Jann Horn wrote:
> On Tue, Oct 27, 2020 at 9:04 PM Mickaël Salaün <mic@digikod.net> wrote:
>> This documentation can be built with the Sphinx framework.
>>
>> Cc: James Morris <jmorris@namei.org>
>> Cc: Jann Horn <jannh@google.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Serge E. Hallyn <serge@hallyn.com>
>> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
>> Reviewed-by: Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr>
> [...]
>> diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
> [...]
>> +Landlock rules
>> +==============
>> +
>> +A Landlock rule enables to describe an action on an object. An object is
>
> s/enables to describe/describes/
OK.
>
>> +currently a file hierarchy, and the related filesystem actions are defined in
>> +`Access rights`_. A set of rules is aggregated in a ruleset, which can then
>> +restrict the thread enforcing it, and its future children.
>> +
>> +Defining and enforcing a security policy
>> +----------------------------------------
>> +
>> +We first need to create the ruleset that will contain our rules. For this
>> +example, the ruleset will contain rules which only allow read actions, but
>> +write actions will be denied. The ruleset then needs to handle both of these
>> +kind of actions. To have a backward compatibility, these actions should be
>> +ANDed with the supported ones.
>
> This sounds as if there is a way for userspace to discover which
> actions are supported by the running kernel; but we don't have
> anything like that, right?
Right, it dates from the landlock_get_features(2), which is now gone but
may be replaced by something else in the future. I'll remove that.
>
> If we want to make that possible, we could maybe change
> sys_landlock_create_ruleset() so that if
> ruleset_attr.handled_access_fs contains bits we don't know, we clear
> those bits and then copy the struct back to userspace? And then
> userspace can retry the syscall with the cleared bits? Or something
> along those lines?
Yes, but I would prefer clear syscall which don't read and write from/to
the same argument. I'm working on a more generic solution. It should not
be an issue for now.
>
> [...]
>> +We can now add a new rule to this ruleset thanks to the returned file
>> +descriptor referring to this ruleset. The rule will only enable to read the
>
> s/enable to read/allow reading/
OK.
>
>> +file hierarchy ``/usr``. Without another rule, write actions would then be
>> +denied by the ruleset. To add ``/usr`` to the ruleset, we open it with the
>> +``O_PATH`` flag and fill the &struct landlock_path_beneath_attr with this file
>> +descriptor.
> [...]
>> +Inheritance
>> +-----------
>> +
>> +Every new thread resulting from a :manpage:`clone(2)` inherits Landlock domain
>> +restrictions from its parent. This is similar to the seccomp inheritance (cf.
>> +:doc:`/userspace-api/seccomp_filter`) or any other LSM dealing with task's
>> +:manpage:`credentials(7)`. For instance, one process's thread may apply
>> +Landlock rules to itself, but they will not be automatically applied to other
>> +sibling threads (unlike POSIX thread credential changes, cf.
>> +:manpage:`nptl(7)`).
>> +
>> +When a thread sandbox itself, we have the grantee that the related security
>
> s/sandbox/sandboxes/
> s/grantee/guarantee/
OK.
>
>> +policy will stay enforced on all this thread's descendants. This enables to
>> +create standalone and modular security policies per application, which will
>
> s/enables to create/allows creating/
OK.
>
>
>> +automatically be composed between themselves according to their runtime parent
>> +policies.
next prev parent reply other threads:[~2020-10-29 11:38 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 20:03 [PATCH v22 00/12] Landlock LSM Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 01/12] landlock: Add object management Mickaël Salaün
2020-10-29 1:05 ` Jann Horn
2020-10-29 9:30 ` Mickaël Salaün
2020-10-30 3:02 ` Jann Horn
2020-11-16 21:26 ` Pavel Machek
2020-11-16 21:36 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 02/12] landlock: Add ruleset and domain management Mickaël Salaün
2020-10-29 1:05 ` Jann Horn
2020-10-29 9:35 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 03/12] landlock: Set up the security framework and manage credentials Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-27 20:03 ` [PATCH v22 04/12] landlock: Add ptrace restrictions Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-27 20:03 ` [PATCH v22 05/12] LSM: Infrastructure management of the superblock Mickaël Salaün
2020-10-28 5:29 ` James Morris
2020-10-27 20:03 ` [PATCH v22 06/12] fs,security: Add sb_delete hook Mickaël Salaün
2020-10-28 5:30 ` James Morris
2020-10-29 1:06 ` Jann Horn
2020-10-27 20:03 ` [PATCH v22 07/12] landlock: Support filesystem access-control Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-29 10:47 ` Mickaël Salaün
2020-11-03 16:03 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 08/12] landlock: Add syscall implementations Mickaël Salaün
2020-10-29 1:06 ` Jann Horn
2020-10-29 11:30 ` Mickaël Salaün
2020-10-30 3:07 ` Jann Horn
2020-10-30 12:41 ` Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 09/12] arch: Wire up Landlock syscalls Mickaël Salaün
2020-10-28 5:31 ` James Morris
2020-10-27 20:03 ` [PATCH v22 10/12] selftests/landlock: Add user space tests Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 11/12] samples/landlock: Add a sandbox manager example Mickaël Salaün
2020-10-27 20:03 ` [PATCH v22 12/12] landlock: Add user and kernel documentation Mickaël Salaün
2020-10-29 1:07 ` Jann Horn
2020-10-29 11:38 ` Mickaël Salaün [this message]
2020-10-29 1:05 ` [PATCH v22 00/12] Landlock LSM Jann Horn
2020-10-29 11:40 ` Mickaël Salaün
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