Commit Graph

6 Commits

Author SHA1 Message Date
Mickaël Salaün
5e469829ba
landlock: Explain how to support Landlock
Let's help users by documenting how to enable and check for Landlock in
the kernel and the running system.  The userspace-api section may not be
the best place for this but it still makes sense to put all the user
documentation at the same place.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220513112743.156414-1-mic@digikod.net
Reviewed-by: Paul Moore <paul@paul-moore.com>
2022-05-23 13:28:03 +02:00
Mickaël Salaün
09340cf413
landlock: Document good practices about filesystem policies
Explain how to set access rights per hierarchy in an efficient and safe
way, especially with the LANDLOCK_ACCESS_FS_REFER side effect (i.e.
partial ordering and constraints for access rights per hierarchy).

Reviewed-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220506161102.525323-12-mic@digikod.net
2022-05-23 13:28:01 +02:00
Mickaël Salaün
6f59abfae3
landlock: Document LANDLOCK_ACCESS_FS_REFER and ABI versioning
Add LANDLOCK_ACCESS_FS_REFER in the example and properly check to only
use it if the current kernel support it thanks to the Landlock ABI
version.

Move the file renaming and linking limitation to a new "Previous
limitations" section.

Improve documentation about the backward and forward compatibility,
including the rational for ruleset's handled_access_fs.

Update the document date.

Reviewed-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220506161102.525323-11-mic@digikod.net
2022-05-23 13:28:00 +02:00
Mickaël Salaün
75c542d6c6
landlock: Reduce the maximum number of layers to 16
The maximum number of nested Landlock domains is currently 64.  Because
of the following fix and to help reduce the stack size, let's reduce it
to 16.  This seems large enough for a lot of use cases (e.g. sandboxed
init service, spawning a sandboxed SSH service, in nested sandboxed
containers).  Reducing the number of nested domains may also help to
discover misuse of Landlock (e.g. creating a domain per rule).

Add and use a dedicated layer_mask_t typedef to fit with the number of
layers.  This might be useful when changing it and to keep it consistent
with the maximum number of layers.

Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220506161102.525323-3-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
2022-05-23 13:27:56 +02:00
Mauro Carvalho Chehab
69fe554015 docs: userspace-api: landlock.rst: avoid using ReST :doc:foo markup
The :doc:`foo` tag is auto-generated via automarkup.py.
So, use the filename at the sources, instead of :doc:`foo`.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/24888a9c5da3c505b2bc274fcd83be348dbaf972.1623824363.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-06-17 13:24:39 -06:00
Mickaël Salaün
5526b45083 landlock: Add user and kernel documentation
Add a first document describing userspace API: how to define and enforce
a Landlock security policy.  This is explained with a simple example.
The Landlock system calls are described with their expected behavior and
current limitations.

Another document is dedicated to kernel developers, describing guiding
principles and some important kernel structures.

This documentation can be built with the Sphinx framework.

Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
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>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210422154123.13086-13-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>
2021-04-22 12:22:11 -07:00