SELinux policy store migration
The newest SELinux userspace project release 2015-02-02 includes a change of the location of the SELinux policy store, which defaults to /var/lib/selinux/.
- Name: Petr Lautrbach
- Email: firstname.lastname@example.org
- Name: Miroslav Grepl
- Email: email@example.com
- Release notes owner:
- Targeted release: Fedora 23
- Last updated: 2015-06-10
- Tracker bug: <will be assigned by the Wrangler>
SELinux security policy is located in /etc/selinux directory together with configuration files. In Fedora, we use a modular policy. It means the policy is not one large source policy but it can be built from modules. These modules together with a base policy (contains the mandatory information) are compiled, linked and located in a policy store where can be built into a binary format and then loaded into the security server. This binary policy is located in /etc/selinux/<SELINUXTYPE>/policy/policy.29 for example.
The above mentioned policy store is located at
- /etc/selinux/<SELINUXTYPE>/modules - default for systems that support versions < 2.4 of libsemanage, libsepol, and policycoreutils.
- /var/lib/selinux/<SELINUXTYPE>/modules - default for systems that support versions >= 2.4 of libsemanage, libsepol, and policycoreutils.
This change builds CIL into libsepol, libsemanage, semodule, semanage to understand CIL and add ability to manage /var/lib/selinux as a new store location. It means this new location only matters if a policy is rebuilt or manipulated.
The new policy store
- has a new complex structure
- supports priority of modules
- the CIL language is used for cached modules
- original modules are converted using an HLL compiler in /usr/libexec/selinux/hll/. The pp compiler converts pp format to CIL language.
Benefit to Fedora
The new store implementation and the CIL language bring improvements to system:
- the policy store is moved out of /etc
- there's performance improvements
- speed-up of SELinux tools like semanage, setsebool
- reduce of memory peak usage
- cached SELinux policy module can be overwritten by a module with same name and with higher priority
- readable CIL format vs. compiled policy modules
- ability to override distribution provided policy!
semodule --priority 100 --install fedora_distro/openstack.pp semodule --priority 400 --install custom/openstack.pp
Both openstack modules are installed in the policy store, but only the custom openstack module is included in the final kernel binary.
- Proposal owners:
- prepare SELinux userspace packages with the release 2015-02-02
- prepare SELinux policy packages with the new store location
- prepare a migration script for users modifications and modules
- check if all packages containing SELinux modules use the right location
- check if all SELinux modules used in Fedora packages are compatible with the new SELinux userspace and are convertible to CIL language
- Other developers:
- Release engineering: N/A
- Policies and guidelines:
- there's no need to update policies
- there might be guidelines which mention the old store location which should be updated
- Trademark approval: N/A (not needed for this Change)
There should be no impact on upgrade. Existing modules will be migrated during the update of userspace packages and SELinux policy package will use the new location by default.
How To Test
- update system with libselinux-2.4 release
- try semodule -l
- try to create a module
- e.g. ausearch -m avc -ts boot | audit2allow -M mytestmodule
- install it - semodule -i mytestmodule.pp
- deinstall it, enable/disable it, see semodule -h
Regular users should not experience any change. The migration should be transparent. There'll be change only for the modules store and operations on SELinux modules should be faster.
N/A (not a System Wide Change)
- use the previous SELinux userspace project release
- use the selinux-policy packages with the policy store located in /etc/selinux
- Contingency mechanism:
- selinux-policy maintainers will revert selinux-policy spec file changes to use the original store in /etc/selinux
- SELinux userspace maintainers will drop SELinux userspace tools version 2.4 and use tools version 2.3
- Contingency deadline: beta freeze
- Blocks release? Yes
- Blocks product? N/A