On Fri, Mar 11, 2022 at 03:52:54PM -0500, Paul Moore wrote: > On Fri, Mar 11, 2022 at 9:01 AM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > Agreed. After going through the patch set, I was wondering what's the > > overall security model and how to visualize that. > > > > So probably there needs to be a documentation patch which explains > > what's the new security model and how does it work. > > Yes, of course. I'll be sure to add a section to the existing docs. > > > Also think both in terms of DAC and MAC. (Instead of just focussing too > > hard on SELinux). > > Definitely. Most of what I've been thinking about the past day or so > has been how to properly handle some of the DAC/capability issues; I > have yet to start playing with the code, but for the most part I think > the MAC/SELinux bits are already working properly. > > > My understanding is that in current model, some of the overlayfs > > operations require priviliges. So mounter is supposed to be priviliged > > and does the operation on underlying layers. > > > > Now in this new model, there will be two levels of check. Both overlay > > level and underlying layer checks will happen in the context of task > > which is doing the operation. So first of all, all tasks will need > > to have enough priviliges to be able to perform various operations > > on lower layer. > > > > If we do checks at both the levels in with the creds of calling task, > > I guess that probably is fine. (But will require a closer code inspection > > to make sure there is no privilege escalation both for mounter as well > > calling task). > > I have thoughts on this, but I don't think I'm yet in a position to > debate this in depth just yet; I still need to finish poking around > the code and playing with a few things :) > > It may take some time before I'm back with patches, but I appreciate > all of the tips and insight - thank you! Let me resurrect this discussion. With https://github.com/fedora-selinux/selinux-policy/commit/1e8688ea694393c9d918939322b72dfb44a01792 the Fedora policy changed kernel_t to a confined domain. This means that many overlayfs setups that are created in initrd will now run into issues, as it will have kernel_t as part of the saved credentials. So while the original use case that inspired the patch set was probably not very common that now changed. It's tricky to work around this. Loading a policy in initrd causes a lot of issues now that kernel_t isn't unconfined anymore. Once the policy is loaded by systemd changing the mounts is tough since we use it for /etc and at this time systemd already has open file handles for policy files in /etc. Johannes -- GPG Key EE16 6BCE AD56 E034 BFB3 3ADD 7BF7 29D5 E7C8 1FA0 Subkey fingerprint: 250F 43F5 F7CE 6F1E 9C59 4F95 BC27 DD9D 2CC4 FD66 SUSE Software Solutions Germany GmbH, Frankenstraße 146, 90461 Nürnberg, Germany Geschäftsführer: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman (HRB 36809, AG Nürnberg)
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