Blocked that hard-coded google dns garbage.
this post was submitted on 08 Nov 2023
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I have a firewall rule to dst-nat any outgoing DNS requests not coming from piHole back to the piHole server. That way all devices on the LAN are forced to use piHole for DNS and can't bypass it. I don't have an OPNSense firewall but I would think it should be able to do that as well.
I suspect DoT and DoH still go through, though? I mean you can always block the port 853 for DoT, but DoH is another story.
Yeah you'd need an L7 application layer filtering firewall to catch DoH since it would detect the SSL packet signature on port 53. Unfortunately that balloons the cost of the device past a reasonable level for a home aficionado.
A workaround for now would be to block known public servers that use DoH like Google DNS, since a lot of devices are adding features to enable DoH by default at the OS level
That's correct. I block DoT in my firewall and block known DoH domains in piHole. I'm sure stuff slips through occasionally but the vast majority of my DNS requests are handled by piHole.
Traditional DNS over UDP/53 is insecure but I'm using ProtonVPN's DNS server over VPN externally so I'm not worried about that.
I see. I may try to do something similar but towards Unbound on my OPNSense router, if that's possible.
How do you block the DoH servers in the pihole? Pihole is a DNS server, devices using a third party DoH server would just bypass the pihole as they're using the IP of the DoH with no DNS lookup required. No?
To block DoH I think you need to block it at the firewall level with a list of blocked IPs for the DoH servers you want to block over 443
You're probably better off blocking it at the firewall level. It would be more thorough but also more effort. In my experience, most devices/apps that use DoH call a domain name rather than an IP. If you block the domain in piHole, the app cant resolve the DoH server IP and therefore won't be able to use DoH.