On Fri, Aug 2, 2024 at 7:45 AM Stephen Smalley <stephen.smalley.work@xxxxxxxxx> wrote: > > On Fri, Aug 2, 2024 at 4:27 AM Dominick Grift > <dominick.grift@xxxxxxxxxxx> wrote: > > > > > > I think this question was already asked but I could not find the > > discussion. > > > > What would be the challenges to support a monolitic policy on a volatile > > root? > > > > In a volatile root scenario there is only a non-volatile readonly > > /usr. Would it be possible to teach libselinux that if there is a > > /usr/selinux and not a /etc/selinux and/or /var/lib/selinux that it would > > use that instead? > > > > The challenge I am currently facing with systemd.volatile=yes is that > > when the policy is loaded from initramfs that systemd-tmpfiles (and > > systemd-sysusers) cannot properly populate root from /usr/share/factory > > (or created) because they rely on libselinux,get/setfilecon and thus on > > /etc/selinux/contexts/files. There is a slight chicken and egg situation there. > > > > Often times its not a probable because one can do with automatic type > > transitions but some of these files get created atomically (/etc/passwd > > and /etc/shadow for example) and not to mention that these libselinux > > linked components might get confused and noisy if selinux is enabled and > > enforcing but there is no /etc/selinux. > > > > Duplicating policy in initramfs and /etc, /var/lib would invite > > inconsistencies and is not feasible but if the policy is readonly and > > thus monolitic then this might be feasible if it is not too > > ugly. Actually in such a scenario we would probably not need a policy in > > initramfs at all since systemd would just load it from /usr instead of /etc. > > I've seen a similar concern raised previously even for modular/managed policy. > It's all just software so I don't think it would be hard to modify > libselinux to fall back to /usr/selinux if there is no file in > /etc/selinux; it just requires someone to write a patch for it. May > have policy implications (i.e. anything that currently accesses > /etc/selinux now also may need search access to usr_t) but that's > pretty common anyway. To clarify, for monolithic policy, you just need to update libselinux to fall back to searching /usr if /etc lacks the file. For modular/managed policy we would also need to update libsemanage to write the final policy files somewhere, although /var seems more appropriate than /usr for that?
