On Thursday, April 07, 2016 01:45:32 AM Florian Westphal wrote: > Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > On Wed, Apr 6, 2016 at 6:14 PM, Florian Westphal <fw@xxxxxxxxx> wrote: > > > netfilter hooks are per namespace -- so there is hook unregister when > > > netns is destroyed. > > > > Looking around, I see the global and per-namespace registration > > functions (nf_register_hook and nf_register_net_hook, respectively), > > but I'm looking to see if/how newly created namespace inherit > > netfilter hooks from the init network namespace ... if you can create > > a network namespace and dodge the SELinux hooks, that isn't a good > > thing from a SELinux point of view, although it might be a plus > > depending on where you view Paolo's original patches ;) > > Heh :-) > > If you use nf_register_net_hook, the hook is only registered in the > namespace. > > If you use nf_register_hook, the hook is put on a global list and > registed in all existing namespaces. > > New namespaces will have the hook added as well (see > netfilter_net_init -> nf_register_hook_list in netfilter/core.c ) > > Since nf_register_hook is used it should be impossible to get a netns > that doesn't call these hooks. Great, thanks. > > > Do you think it makes sense to rework the patch to delay registering > > > of the netfiler hooks until the system is in a state where they're > > > needed, without the 'unregister' aspect? > > > > I would need to see the patch to say for certain, but in principle > > that seems perfectly reasonable and I think would satisfy both the > > netdev and SELinux camps - good suggestion. My main goal is to drop > > the selinux_nf_ip_init() entirely so it can't be used as a ROP gadget. > > > > We might even be able to trim the secmark_active and peerlbl_active > > checks in the SELinux netfilter hooks (an earlier attempt at > > optimization; contrary to popular belief, I do care about SELinux > > performance), although that would mean that enabling the network > > access controls would be one way ... I guess you can disregard that > > last bit, I'm thinking aloud again. > > One way is fine I think. Yes, just disregard my second paragraph above. > > > Ideally this would even be per netns -- in perfect world we would > > > be able to make it so that a new netns are created with an empty > > > hook list. > > > > In general SELinux doesn't care about namespaces, for reasons that are > > sorta beyond the scope of this conversation, so I would like to stick > > to a all or nothing approach to enabling the SELinux netfilter hooks > > across namespaces. Perhaps we can revisit this at a later time, but > > let's keep it simple right now. > > Okay, I'd prefer to stick to your recommendation anyway wrt. to selinux > (Casey, I read your comment regarding smack. Noted, we don't want to > break smack either...) > > I think that in this case the entire question is: > > In your experience, how likely is a config where selinux is enabled BUT the > hooks are not needed (i.e., where we hit the > > if (!selinux_policycap_netpeer) > return NF_ACCEPT; > > if (!secmark_active && !peerlbl_active) > return NF_ACCEPT; > > tests inside the hooks)? If such setups are uncommon we should just > drop this idea or at least put it on the back burner until the more > expensive netfilter hooks (conntrack, cough) are out of the way. A few years ago I would have said that it is relatively uncommon for admins to enable the SELinux network access controls; it was typically just government/intelligence agencies who had very strict access control requirements and represented a small portion of SELinux users. However, over the past few years I've been fielding more and more questions from admins/devs in the virtualization space who are interested in some of these capabilities; it isn't clear to me how many of these people are switching it on, but there is definitely more interest than I have seen in the past and the interested is centered around some rather common use cases. So, to summarize, I don't know ;) If you've got bigger sources of overhead, my opinion would be to go tackle those first. Perhaps I can even find the time to work on the SELinux/netfilter stuff while you are off slaying the bigger dragons, no promises at the moment. -- paul moore www.paul-moore.com _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.
