You should theoretically be able to use VPNVM as a firewall. However,
there is a bug in qubes-firewall that causes "Deny Except" mode to block
all DNS traffic when a VPN/tunnel is used. The obvious workaround is to
create another proxyVM to be placed between appVM and VPNVM.
If you would rather avoid creating an extra proxyVM, you can use a VPN
project that contains a fix for the DNS bug:
https://github.com/tasket/Qubes-vpn-support
Also, in most cases no firewallVM is needed between VPNVM and sys-net,
so the following chain is OK:
appVM -> VPNVM -> sys-net
--
Chris Laprise,
tas...@posteo.net
https://twitter.com/ttaskett
PGP: BEE2 20C5 356E 764A 73EB 4AB3 1DC4 D106 F07F 1886