Re: net_admin audit for setsockopt SO_SNDBUFFORCE

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On Tue, 2017-03-21 at 16:06 +0100, cgzones wrote:
> Hi list,
> this thread[1] about setsockopt(...,...,SO_SNDBUFFORCE), which
> triggers widely due to systemd, let me think about the recent SELinux
> kernel fixes: the reordering of dac_read_search and dac_override and
> also the cap_wake_alarm fix.
> 
> Would it make sense to test, if the send buffer is really set to a
> higher value than wmem_max, before testing for the cap_net_admin
> permission[2]?
> (might also apply to SO_RCVBUFFORCE)

Probably not, since SO_SNDBUFFORCE only exists to allow a process with
CAP_NET_ADMIN to override the wmem_max limit per the man page.  IOW,
only processes with CAP_NET_ADMIN should ever use that option. 
dontaudit'ing that does not seem like a good idea either; I think you
have to allow it or risk silent breakage.

What would perhaps be better would be to introduce LSM hooks to allow
finer-grained distinctions to be made among the different CAP_NET_ADMIN
cases, ala issue #26.  Then the impact of allowing net_admin would be
less significant.


> 
> Best regards,
>     Christian Göttsche
> 
> 
> [1] http://oss.tresys.com/pipermail/refpolicy/2017-March/009185.html
> [2] https://github.com/torvalds/linux/blob/ae50dfd61665086e617cc9e554
> a1285d52765670/net/core/sock.c#L715
> 
> 
> p.s.: friendly ping on https://marc.info/?l=selinux&m=148944677530753
> &w=2
> 
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