Testing chrony seccomp support

[Miroslav Lichvar]

In chrony 2.2-pre1 was added support for system call filtering with
the kernel seccomp facility. In chrony it's mainly useful to reduce
the damage from attackers who can execute arbitrary code, e.g. prevent
gaining the root privileges through a kernel vulnerability.

The rawhide chrony package is now compiled with the seccomp support,
but the filtering is not enabled by default. The trouble is it has to
cover all system calls needed in all possible configurations of chrony
and all libraries it depends on, which is difficult and it may even
change over time as the libraries are updated.

I'm interested to know if this works in other configurations than what
I tried, especially non-default NSS configurations, and get an idea if
this could be enabled by default at some point.

If you would like to help with the testing:

1. echo 'OPTIONS="-F -1"' > /etc/sysconfig/chronyd
2. systemctl restart chronyd
3. occasionally check if chronyd is still running

If you see in the log that the process was killed with status=31/SYS,
it's a problem in the seccomp support. Please let me know it has
crashed for you. Unfortunately, abrt doesn't seem to catch these
crashes, even when /proc/sys/fs/suid_dumpable is set to 2.

For F22 and F23 there is a COPR repo with packages built from the
current development code:
https://copr.fedoraproject.org/coprs/mlichvar/chrony/

Thanks,

-- 
Miroslav Lichvar