Since Gitea servers may be exposed directly to the Internet, it is
important to prevent SSH tunneling, lest the server become an ingress
point into the network.
Additionally, the *gitea* user should not be allowed to use password
authentication, as this would only work if the user actually has a
password (which it does not) and would result in shell access instead of
Gitea.
This commit adjusts the firewall and networking configuration on dc0 to
host the Pyrocufflink remote access IPsec VPN locally instead of
forwarding it to the internal VPN server.
The host *zbx0.pyrocufflink.blue* (a Raspberry Pi) runs the Zabbix
server and web UI. It has a reserved IPv4 address to simplify reverse
DNS management for now, since Samba's dynamic DNS client does not
register PTR records.
These IPv6 reverse DNS zones are managed by the Samba AD DCs for the
*pyrocufflink.blue* domain. These zones correspond to the IPv6 prefixes
used by the "blue" network.
Connection Tracking does not work for DHCP messages, since many are
broadcast. As such, the firewall must explicitly allow datagrams
destined for the DHCP client port.
For internal services, particularly DNS, it is easier to use a ULA
prefix than rely exclusively on routed addresses, since these can change
relatively frequently.
Instead of listing the addresses for DNS and NTP servers again in the
DHCP server configuration, these are now taken from the canonical
definitions in the `dch_networks` variable.
The *filter* table is responsible for deciding which packets will be
accepted and which will be rejected. It has three chains, which classify
packets according to whether they are destined for the local machine
(input), passing through this machine (forward) or originating from the
local machine (output).
The *dch-gw* role now configures all three chains in this table. For
now, it defines basic rules, mostly based on TCP/UDP destination port:
* Traffic destined for a service hosted by the local machine (DNS, DHCP,
SSH), is allowed if it does not come from the Internet
* Traffic passing through the machine is allowed if:
* It is passing between internal networks
* It is destined for a host on the FireMon network (VPN)
* It was NATed to in internal host (marked 323)
* It is destined for the Internet
* Only DHCP, HTTP, and DNS are allowed to originate from the local
machine
This configuration requires an `internet_iface` variable, which
indicates the name of the network interface connected to the Internet
directly.
The *samba-dc* role now configures `winbindd` on domain controllers to
support identity mapping on the local machine. This will allow domain
users to log into the domain controller itself, e.g. via SSH.
The Fedora packaging of *samba4* still has some warts. Specifically, it
does not have a proper SELinux policy, so some work-arounds need to be
put into place in order for confined processes to communicate with
winbind.
The BIND9_DLZ plugin turned out to be pretty flaky. It craps out
whenever `named` is reloaded, which seems to happen occasionally for
reasons I cannot identify. Combined with the weird SELinux issues, and
the fact that upstream recommends against it anyway, I decided to just
use the built-in DNS server in Samba.
Dustin