On Thu, 2016-04-07 at 14:55 -0400, Paul Moore wrote: > 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. Double checking if I got the above correctly. Will be ok if we post a v2 version of this series, removing the hooks de-registration bits, but preserving the selinux nf-hooks and socket_sock_rcv_skb() on-demand/delayed registration ? Will that fit with the post-init read only memory usage that you are planning ? Regards, Paolo _______________________________________________ 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.
