A usual step in creating OS file system trees is to apply the
correct SELinux labels for all files and directories. This is
done by the org.osbuild.selinux stage, which internally uses the
setfiles command in order to do so. The SELiunx policy to be
used for this operation is the one of the newly created system,
not the host one. It therefore can contain labels that are not
known on the host. The kernel will prevent setting invalid,
i.e. unknown, labels unless the caller has the CAP_MAC_ADMIN
capability. By default, setfiles is executed in the setfiles_t
domain, where it lacks that capability. Therefore a custom
osbuild SELinux policy was created, with a special transition
rule that will execute setfiles in the setfiles_mac_t
domain. All stages, sources and assemblers as well as the main
binary are label with the new osbuild_exec_t label.
Additionally, allow a transition from osbuild_t to install_t by
using `anaconda_domtrans_install`, so that ostree and
rpm-ostree, which are labeled as install_exec_t, can transition
to the install_t domain when called form osbuild. Update the
spec file to build the policy and include it in a new
osbuild-selinux sub-package.
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