linux-kernel - Re: [PATCH v4 0/6] landlock: Signal scoping support

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Message-ID: <20240911.BieLu8DooJiw@digikod.net>
Date: Wed, 11 Sep 2024 20:17:04 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Tahera Fahimi <fahimitahera@...il.com>
Cc: outreachy@...ts.linux.dev, gnoack@...gle.com, paul@...l-moore.com, 
	jmorris@...ei.org, serge@...lyn.com, linux-security-module@...r.kernel.org, 
	linux-kernel@...r.kernel.org, bjorn3_gh@...tonmail.com, jannh@...gle.com, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v4 0/6] landlock: Signal scoping support

We should also have the same tests as for scoped_vs_unscoped variants.
I renamed them from the abstract unix socket patch series, please take a
look:
https://git.kernel.org/pub/scm/linux/kernel/git/mic/linux.git/log/?h=next

I'll send more reviews tomorrow and I'll fix most of them in my -next
branch (WIP), except for the hook_file_send_sigiotask tests and these
scoped_vs_unscoped variants that you should resolve.

On Fri, Sep 06, 2024 at 03:30:02PM -0600, Tahera Fahimi wrote:
> This patch series adds scoping mechanism for signals.
> Closes: https://github.com/landlock-lsm/linux/issues/8
> 
> Problem
> =======
> 
> A sandboxed process is currently not restricted from sending signals
> (e.g. SIGKILL) to processes outside the sandbox since Landlock has no
> restriction on signals(see more details in [1]).
> 
> A simple way to apply this restriction would be to scope signals the
> same way abstract unix sockets are restricted.
> 
> [1]https://lore.kernel.org/all/20231023.ahphah4Wii4v@digikod.net/
> 
> Solution
> ========
> 
> To solve this issue, we extend the "scoped" field in the Landlock
> ruleset attribute structure by introducing "LANDLOCK_SCOPED_SIGNAL"
> field to specify that a ruleset will deny sending any signals from
> within the sandbox domain to its parent(i.e. any parent sandbox or
> non-sandbox processes).
> 
> Example
> =======
> 
> Create a sansboxed shell and pass the character "s" to LL_SCOPED:
> LL_FD_RO=/ LL_FS_RW=. LL_SCOPED="s" ./sandboxer /bin/bash
> Try to send a signal(like SIGTRAP) to a process ID <PID> through:
> kill -SIGTRAP <PID>
> The sandboxed process should not be able to send the signal.
> 
> Previous Versions
> =================
> v3:https://lore.kernel.org/all/cover.1723680305.git.fahimitahera@gmail.com/
> v2:https://lore.kernel.org/all/cover.1722966592.git.fahimitahera@gmail.com/
> v1:https://lore.kernel.org/all/cover.1720203255.git.fahimitahera@gmail.com/
> 
> Tahera Fahimi (6):
>   landlock: Add signal scoping control
>   selftest/landlock: Signal restriction tests
>   selftest/landlock: Add signal_scoping_threads test
>   selftest/landlock: Test file_send_sigiotask by sending out-of-bound
>     message
>   sample/landlock: Support sample for signal scoping restriction
>   landlock: Document LANDLOCK_SCOPED_SIGNAL
> 
>  Documentation/userspace-api/landlock.rst      |  22 +-
>  include/uapi/linux/landlock.h                 |   3 +
>  samples/landlock/sandboxer.c                  |  17 +-
>  security/landlock/fs.c                        |  17 +
>  security/landlock/fs.h                        |   6 +
>  security/landlock/limits.h                    |   2 +-
>  security/landlock/task.c                      |  59 +++
>  .../selftests/landlock/scoped_signal_test.c   | 371 ++++++++++++++++++
>  .../testing/selftests/landlock/scoped_test.c  |   2 +-
>  9 files changed, 486 insertions(+), 13 deletions(-)
>  create mode 100644 tools/testing/selftests/landlock/scoped_signal_test.c
> 
> -- 
> 2.34.1
>