Messages in this thread Patch in this message | | | From | Mickaël Salaün <> | Subject | [PATCH v2 1/2] landlock: Extend documentation for kernel support | Date | Tue, 27 Feb 2024 12:05:49 +0100 |
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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 <gnoack@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Mickaël Salaün <mic@digikod.net> ---
Changes since v1: * New patch, suggested by Kees Cook. --- Documentation/userspace-api/landlock.rst | 57 +++++++++++++++++++++--- 1 file changed, 51 insertions(+), 6 deletions(-)
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 <landlock_abi_versions>`. If -Landlock is not currently supported, we need to :ref:`configure the kernel -appropriately <kernel_support>`. +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 <landlock_abi_versions>`. +If Landlock is not currently supported, we need to +:ref:`configure the kernel appropriately <kernel_support>`. 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/.*\(\<lsm=\S\+\).*/\1/p' /proc/cmdline + lsm=lockdown,yama,integrity,apparmor + +...we should configure the bootloader to set a cmdline extending the ``lsm`` +list with the ``landlock,`` prefix:: + + lsm=landlock,lockdown,yama,integrity,apparmor + +After a reboot, we can check that Landlock is up and running by looking at +kernel logs: + +.. code-block:: console + + # dmesg | grep landlock || journalctl -kb -g landlock + [ 0.000000] Command line: [...] lsm=landlock,lockdown,yama,integrity,apparmor + [ 0.000000] Kernel command line: [...] lsm=landlock,lockdown,yama,integrity,apparmor + [ 0.000000] LSM: initializing lsm=lockdown,capability,landlock,yama,integrity,apparmor + [ 0.000000] landlock: Up and running. + +Note that according to the built time kernel configuration, +``lockdown,capability,`` may always stay at the beginning of the ``LSM: +initializing lsm=`` list even if they are not configured with the bootloader, +which is OK. + +Network support +--------------- + To be able to explicitly allow TCP operations (e.g., adding a network rule with ``LANDLOCK_ACCESS_NET_BIND_TCP``), the kernel must support TCP (``CONFIG_INET=y``). Otherwise, sys_landlock_add_rule() returns an base-commit: b4007fd27206c478a4b76e299bddf4a71787f520 -- 2.44.0
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