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Message-Id: <cover.1725657727.git.fahimitahera@gmail.com>
Date: Fri, 6 Sep 2024 15:30:02 -0600
From: Tahera Fahimi <fahimitahera@...il.com>
To: outreachy@...ts.linux.dev
Cc: mic@...ikod.net,
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,
Tahera Fahimi <fahimitahera@...il.com>
Subject: [PATCH v4 0/6] landlock: Signal scoping support
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
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