Messages in this thread | | | Date | Thu, 14 Jan 2010 09:00:39 -0600 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4) |
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Quoting Pavel Machek (pavel@ucw.cz): > > Quoting Michael Stone (michael@laptop.org): > > > Serge Hallyn wrote: > > > >Michael, I'm sorry, I should go back and search the thread for the > > > >answer, but don't have time right now - do you really need > > > >disablenetwork to be available to unprivileged users? > > > > > > Rainbow can only drop the networking privileges when we know at app launch time > > > (e.g. based on a manifest or from the human operator) that privileges can be > > > dropped. Unfortunately, most of the really interesting uses of disablenetwork > > > happen *after* rainbow has dropped privilege and handed control the app. > > > Therefore, having an API which can be used by at least some low-privilege > > > processes is important to me. > > > > > > >is it ok to require CAP_SETPCAP (same thing required for dropping privs from > > > >bounding set)? > > > > > > Let me try to restate your idea: > > > > > > We can make disablenetwork safer by permitting its use only where explicitly > > > permitted by some previously privileged ancestor. The securebits facility > > > described in > > > > > > http://lwn.net/Articles/280279/ > > > > > > may be a good framework in which to implement this control. > > > > > > Did I understand correctly? If so, then yes, this approach seems like it would > > > work for me. > > > > That is a little more than I was saying this time though I think I > > suggested it earlier. > > > > But really I don't think anyone would care to separate a system into > > some processes allowed to do unprivileged disablenetwork and other > > processes not allowed to, so a (root-owned mode 644) sysctl seems just > > as useful. > > Global solution like that is always wrong. (And we have better > solution available.)
All right, so Michael suggested securebits, I personally feel prctl would be more appropriate, but in any case the suggestion then is:
foo_enable_disablenet() is either prctl(PR_ALLOW_DISABLENET) or prctl(PR_SET_SECUREBITS, (1 << PR_ALLOW_DISABLENET) | (1 << PR_ALLOW_DISABLENET_LOCK)) and it requires privilege (CAP_NET_ADMIN presumably) to make this call.
prctl(PR_SET_DISABLENETWORK), or whatever Michael was using, does not require privilege, but requires that foo_enable_disablenet() have been previously called by a privileged app.
-serge
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