In the end firewall is implemented as .Get and .Set rules, with policy
statically set to 'drop'. This way allow atomic firewall updates.
Since we already have appropriate firewall format handling in
qubes.firewall module - reuse it from there, but adjust the code to be
prepared for potentially malicious input. And also mark such variables
with untrusted_ prefix.
There is also third method: .Reload - which cause firewall reload
without making any change.
QubesOS/qubes-issues#2622FixesQubesOS/qubes-issues#2869
There is a problem with having separate default action ("policy") and
rules because it isn't possible to set both of them atomically at the
same time.
To solve this problem, always have policy 'drop' (as a safe default),
but by default have a single rule with action 'accept'
FixesQubesOS/qubes-issues#2869
First part - handling firewall.xml and rules formatting.
Specification on https://qubes-os.org/doc/vm-interface/
TODO (for dom0):
- plug into QubesVM object
- expose rules in QubesDB (including reloading)
- drop old functions (vm.get_firewall_conf etc)
QubesOS/qubes-issues#1815
