From patchwork Tue Feb 27 11:05:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 13573562 Received: from smtp-42a8.mail.infomaniak.ch (smtp-42a8.mail.infomaniak.ch [84.16.66.168]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A28BF137C38 for ; Tue, 27 Feb 2024 11:15:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=84.16.66.168 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709032514; cv=none; b=Z6a1G3scwbuCO9GExMzTiiUfBe/yJKthLEazxBI4GYgbjoKzHiaI9RfERbdk9xskZJL9PKASVsrC2me08AYhy9WGKs+SHYNGnHRt53SySsBOATO122scau5UEo8C4HpqIX2slO5AtsEdJSTdF4/VFTs+nULBgXFGnBSVKGCnI8c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709032514; c=relaxed/simple; bh=fo0e4FRJyzZJ6d6n/7sR3VvkreP3rfZ9EhEu8wKED6Q=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=Zq7JcYG406UgrQtP0KWX4f9J2GA9HxK8A/kNcfxphE7sq5RFFbH6mNXK0q6wk53u2JEitjCLlKm/RIez4o1AanuznDEhqVXrhYQpDSF63bDl1QEJ/xNdmKXyo8ygl4lQ5NIccRQ7Pb/66bqnIEo8l0sg81uId+39/28LljoUQFE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=aJAgMZqv; arc=none smtp.client-ip=84.16.66.168 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="aJAgMZqv" Received: from smtp-4-0001.mail.infomaniak.ch (unknown [10.7.10.108]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4TkZRK3mSFzMq5jp; Tue, 27 Feb 2024 12:06:05 +0100 (CET) Received: from unknown by smtp-4-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4TkZRJ1SGDzDLf; Tue, 27 Feb 2024 12:06:04 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1709031965; bh=fo0e4FRJyzZJ6d6n/7sR3VvkreP3rfZ9EhEu8wKED6Q=; h=From:To:Cc:Subject:Date:From; b=aJAgMZqvXCuTbBi3QrqQEix+We3BKKkgtSzWSI/iyXVsm+O11Q4WECvzP7XS5p7AK SysOh8oMYi25zAJ5MEnSVlYHTBLoZKpMm1EgyycJhArAgZ+5oaXh/Ej5Es4I7TuWwX 6Vizit1a6SoZwfE3jEmCv42kq4iV/5BZJ2nNfIPM= From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: =?utf-8?q?G=C3=BCnther_Noack?= , Paul Moore , "Serge E . Hallyn" Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Konstantin Meskhidze , Shervin Oloumi , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Kees Cook Subject: [PATCH v2 1/2] landlock: Extend documentation for kernel support Date: Tue, 27 Feb 2024 12:05:49 +0100 Message-ID: <20240227110550.3702236-1-mic@digikod.net> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Infomaniak-Routing: alpha Extend the kernel support section with one subsection for build time configuration and another for boot time configuration. Extend the boot time subsection with a concrete example. Update the journalctl command to include the boot option. Cc: Günther Noack Cc: Kees Cook Signed-off-by: Mickaël Salaün Reviewed-by: Günther Noack Reviewed-by: Alejandro Colomar --- Changes since v1: * New patch, suggested by Kees Cook. --- Documentation/userspace-api/landlock.rst | 57 +++++++++++++++++++++--- 1 file changed, 51 insertions(+), 6 deletions(-) base-commit: b4007fd27206c478a4b76e299bddf4a71787f520 diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst index 2e3822677061..838cc27db232 100644 --- a/Documentation/userspace-api/landlock.rst +++ b/Documentation/userspace-api/landlock.rst @@ -19,11 +19,12 @@ unexpected/malicious behaviors in user space applications. Landlock empowers any process, including unprivileged ones, to securely restrict themselves. We can quickly make sure that Landlock is enabled in the running system by -looking for "landlock: Up and running" in kernel logs (as root): ``dmesg | grep -landlock || journalctl -kg landlock`` . Developers can also easily check for -Landlock support with a :ref:`related system call `. If -Landlock is not currently supported, we need to :ref:`configure the kernel -appropriately `. +looking for "landlock: Up and running" in kernel logs (as root): +``dmesg | grep landlock || journalctl -kb -g landlock`` . +Developers can also easily check for Landlock support with a +:ref:`related system call `. +If Landlock is not currently supported, we need to +:ref:`configure the kernel appropriately `. Landlock rules ============== @@ -499,6 +500,9 @@ access rights. Kernel support ============== +Build time configuration +------------------------ + Landlock was first introduced in Linux 5.13 but it must be configured at build time with ``CONFIG_SECURITY_LANDLOCK=y``. Landlock must also be enabled at boot time as the other security modules. The list of security modules enabled by @@ -507,11 +511,52 @@ contains ``CONFIG_LSM=landlock,[...]`` with ``[...]`` as the list of other potentially useful security modules for the running system (see the ``CONFIG_LSM`` help). +Boot time configuration +----------------------- + If the running kernel does not have ``landlock`` in ``CONFIG_LSM``, then we can -still enable it by adding ``lsm=landlock,[...]`` to +enable Landlock by adding ``lsm=landlock,[...]`` to Documentation/admin-guide/kernel-parameters.rst thanks to the bootloader configuration. +For example, if the current built-in configuration is: + +.. code-block:: console + + $ zgrep -h "^CONFIG_LSM=" "/boot/config-$(uname -r)" /proc/config.gz 2>/dev/null + CONFIG_LSM="lockdown,yama,integrity,apparmor" + +...and if the cmdline doesn't contain ``landlock`` either: + +.. code-block:: console + + $ sed -n 's/.*\(\ X-Patchwork-Id: 13573551 Received: from smtp-1909.mail.infomaniak.ch (smtp-1909.mail.infomaniak.ch [185.125.25.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12374139591 for ; Tue, 27 Feb 2024 11:06:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.125.25.9 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709031975; cv=none; b=a+J6kUT9YaZWf7MnNi90d8kuE4R42s5CA0He9uUZl1xbv7zT/fSyrmlfC2ab7iJJYDl4gSuI5IgpNLdDfBSbMAJ9HZf/8vlNUC9nRouueHOCJg4SCVyzCZDv+OYZdnjdMK1FWq7S0zg4WNQJoi3GcPLCXoBZ2yorKEImLwkpugs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709031975; c=relaxed/simple; bh=jPUoWxQfL0gN4M9XnMPtb4OVmzxvQ8jhCx4n49IoT7U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=BlQE8QYr9exPrETTQaZK86vqrgyy5GZFGAYRuYyhrGntI5UtK7mMnj23oarqBNgF+smlMy9L9egLxGyI9x5doOtiTSH7uUruPPWv4gOdKN9Ha6ZaFQ+s/obaTjQWOFoBpjvOe3VYi2d1QvbseWYfvlQJAMXfTDE05pJWVRG1Pmc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=oCw/iF23; arc=none smtp.client-ip=185.125.25.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="oCw/iF23" Received: from smtp-3-0000.mail.infomaniak.ch (smtp-3-0000.mail.infomaniak.ch [10.4.36.107]) by smtp-4-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4TkZRL3hQgzfF; Tue, 27 Feb 2024 12:06:06 +0100 (CET) Received: from unknown by smtp-3-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4TkZRL0Ngrz3k; Tue, 27 Feb 2024 12:06:06 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1709031966; bh=jPUoWxQfL0gN4M9XnMPtb4OVmzxvQ8jhCx4n49IoT7U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oCw/iF23a34Rv0MBwr2Ia6cQ8m8h0jvHC8OAnyauVIncs0HoaFwNz47dPhVBwgEjw R5yruWwiqbByh+WzDRqxenUS46BMI9ak98EP9PcOxTd4ecJ/LXUlBEDCPa5K9iN5Qt hb3lJFSu+CT4yjc6FlcRhOYLyM3bfinMCILgyBUg= From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: =?utf-8?q?G=C3=BCnther_Noack?= , Paul Moore , "Serge E . Hallyn" Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Konstantin Meskhidze , Shervin Oloumi , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, stable@vger.kernel.org, Kees Cook , =?utf-8?q?G?= =?utf-8?q?=C3=BCnther_Noack?= Subject: [PATCH v2 2/2] landlock: Warn once if a Landlock action is requested while disabled Date: Tue, 27 Feb 2024 12:05:50 +0100 Message-ID: <20240227110550.3702236-2-mic@digikod.net> In-Reply-To: <20240227110550.3702236-1-mic@digikod.net> References: <20240227110550.3702236-1-mic@digikod.net> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Infomaniak-Routing: alpha Because sandboxing can be used as an opportunistic security measure, user space may not log unsupported features. Let the system administrator know if an application tries to use Landlock but failed because it isn't enabled at boot time. This may be caused by bootloader configurations with outdated "lsm" kernel's command-line parameter. Cc: stable@vger.kernel.org Fixes: 265885daf3e5 ("landlock: Add syscall implementations") Reviewed-by: Kees Cook Reviewed-by: Günther Noack Signed-off-by: Mickaël Salaün --- Changes since v1: * Add Kees's and Günther's Reviewed-by. * Rename is_not_initialized() to not_initialized() and invert the logic, as suggested by Günther. This is a cosmetic change without global behavioral changed. * Update link to point to a new subsection. --- security/landlock/syscalls.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index 898358f57fa0..6788e73b6681 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -33,6 +33,18 @@ #include "ruleset.h" #include "setup.h" +static bool is_initialized(void) +{ + if (likely(landlock_initialized)) + return true; + + pr_warn_once( + "Disabled but requested by user space. " + "You should enable Landlock at boot time: " + "https://docs.kernel.org/userspace-api/landlock.html#boot-time-configuration\n"); + return false; +} + /** * copy_min_struct_from_user - Safe future-proof argument copying * @@ -173,7 +185,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset, /* Build-time checks. */ build_check_abi(); - if (!landlock_initialized) + if (!is_initialized()) return -EOPNOTSUPP; if (flags) { @@ -398,7 +410,7 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd, struct landlock_ruleset *ruleset; int err; - if (!landlock_initialized) + if (!is_initialized()) return -EOPNOTSUPP; /* No flag for now. */ @@ -458,7 +470,7 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32, struct landlock_cred_security *new_llcred; int err; - if (!landlock_initialized) + if (!is_initialized()) return -EOPNOTSUPP; /*