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

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Message-ID: <20240912.eix6ith8Zuxa@digikod.net>
Date: Thu, 12 Sep 2024 14:51:24 +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

On Wed, Sep 11, 2024 at 06:15:24PM -0600, Tahera Fahimi wrote:
> On Wed, Sep 11, 2024 at 08:17:04PM +0200, Mickaël Salaün wrote:
> > We should also have the same tests as for scoped_vs_unscoped variants.
> Hi, 
> 
> Thanks for the review, I will add them soon.
> > 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
> Wonderful! Thank you :)
> 
> > 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.
> I will keep an eye on reviews. What parts of hook_file_send_sigiotask
> would need changes?

The file_send_sigiotask hook was not fully covered.  It's OK now, I
reworked this test to fix that with four variants.

You still need to work on the scoped_vs_unscoped tests for signaling
though.

> 
> > 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
> > > 
> 
>