[Buildroot] [PATCH v2] package/libselinux: Add autorelabel for first boot

[Yann E. MORIN]

José, All,

On 2021-08-19 12:29 +0300, José Pekkarinen spake thusly:
> Currently buildroot ship libselinux without triggering
> this option, which often shows inconsistencies between
> what the refpolicy defines as a label for a file and
> what the actual file has. Triggering an initial relabel
> would help activating enforcing state right away without
> requiring to enter it once in permissive and tweak the
> labels.
> 
> Signed-off-by: José Pekkarinen <jose.pekkarinen at unikie.com>
> ---
> [ v1 -> v2 ] Fix if statement in libselinux recipe
> 
>  package/libselinux/Config.in     | 7 +++++++
>  package/libselinux/libselinux.mk | 3 +++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/package/libselinux/Config.in b/package/libselinux/Config.in
> index 62070c8d59..df8bd7ffd0 100644
> --- a/package/libselinux/Config.in
> +++ b/package/libselinux/Config.in
> @@ -18,3 +18,10 @@ config BR2_PACKAGE_LIBSELINUX
>  
>  comment "libselinux needs a toolchain w/ threads, dynamic library"
>  	depends on !BR2_TOOLCHAIN_HAS_THREADS || BR2_STATIC_LIBS
> +
> +config BR2_PACKAGE_LIBSELINUX_AUTORELABEL
> +	bool
> +	depends on BR2_PACKAGE_LIBSELINUX
> +	depends on BR2_PACKAGE_FINDUTILS
> +	depends on BR2_PACKAGE_GREP
> +	default y
> diff --git a/package/libselinux/libselinux.mk b/package/libselinux/libselinux.mk
> index fdd13aa942..adf4b3d6f6 100644
> --- a/package/libselinux/libselinux.mk
> +++ b/package/libselinux/libselinux.mk
> @@ -71,6 +71,9 @@ define LIBSELINUX_INSTALL_TARGET_CMDS
>  	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D) \
>  		$(LIBSELINUX_MAKE_OPTS) DESTDIR=$(TARGET_DIR) \
>  		$(LIBSELINUX_MAKE_INSTALL_TARGETS)
> +	$(if $(BR2_PACKAGE_LIBSELINUX_AUTORELABEL),
> +		echo "-F" > $(TARGET_DIR)/.autorelabel
> +		mkdir $(TARGET_DIR)/var/lib/selinux)

Isn't this going to fail on read-only filesystems? Relabelling suposedly
requires that extended attributes be added/updated/removed, and that
requires a read-write filesystem...

Can't we do the re-labelling at the time we create the filesystem, i.e.
in fs/common.mk?

And it seems we already have that:

   52 ifeq ($(BR2_PACKAGE_REFPOLICY),y)
   53 define ROOTFS_SELINUX
   54     $(HOST_DIR)/sbin/setfiles -m -r $(TARGET_DIR) \
   55         -c $(TARGET_DIR)/etc/selinux/targeted/policy/policy.$(BR2_PACKAGE_LIBSEPOL_POLICY_VERSION) \
   56         $(TARGET_DIR)/etc/selinux/targeted/contexts/files/file_contexts \
   57         $(TARGET_DIR)
   58 endef
   59 ROOTFS_COMMON_DEPENDENCIES += host-policycoreutils
   60 endif

So why is the labelling wrong? Can't we fix it right there rather than
at runtime?

Regards,
Yann E. MORIN.

>  	if ! grep -q "selinuxfs" $(TARGET_DIR)/etc/fstab; then \
>  		echo "none /sys/fs/selinux selinuxfs noauto 0 0" >> $(TARGET_DIR)/etc/fstab ; fi
>  endef
> -- 
> 2.25.1
> 
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