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by Jnr 659 days ago
OP's example was a great one. For example, let's say you visit your friends and you want to watch some content together that is accessible on your server. Using this approach you can open access to that without setting up Wireguard on friend's smart TV.

And Wireguard does use quite a bit of CPU if you are using a lot of network bandwidth. Small servers don't have that much compute power, so utilizing the port knocking somewhat removes that issue.
2 comments
throwitaway1123 659 days ago
WireGuard has apps for most devices (macOS, iOS, Android, Windows). For smart TVs it's a bit of a mixed bag. Some of them do support VPN clients, and I know Tailscale works on the Apple TV now (Tailscale uses WireGuard under the hood).

If you're using the Ruroco client to proxy requests to the server, then you could do the same with WireGuard. You could have HAProxy (or something similar) proxy requests from your local network to the WireGuard interface.

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Jnr 659 days ago
It is much simpler to open access to the same network using port knocking than setting up VPN apps and profiles on TV.
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throwitaway1123 659 days ago
Which smart TVs natively support port knocking?
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Jnr 659 days ago
No, the example is - you go to friends, join their Wifi, have the same external IP, send the knock from your phone/laptop to open 443 to that IP, and then you can connect from TV or their computers.
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throwitaway1123 659 days ago
Port knocking only handles authentication (it's basically a crude password). It doesn't ensure the integrity (tamper prevention) or privacy of your connection. You would need to set up SSL certificates to handle that. You also need to get the TV to accept those certificates, which would require either a public DNS record (which exposes your server's IP via the certificate transparency log to any client that can issue a DNS request), or you would need to modify your friend's router's DNS resolver (which is even more complicated than installing a VPN, and assumes the TV uses the router's DNS server). A TV isn't going to have an /etc/hosts file that you can use to point a domain at your server's IP address.

So instead I would go to my friend's house, connect to their Wifi, and accept incoming connections from computers and TVs over the local area network and forward them through WireGuard. The TV would connect to my device via plain HTTP (which is fine since it's all happening locally), and then my device would be responsible for securely connecting to the server via WireGuard. This also has the benefit of implicitly revoking access as soon as I leave their house with my device.

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Jnr 659 days ago
You are slightly wrong.

TLS is not mandatory in all cases, but if you want to use it, it is not an issue having a certificate. Certificate itself has nothing to do with DNS beyond the verification step.

And even then you do not have to open any ports, even to letsencrypt verification, since you can use DNS verification method instead (for example using Cloudflare API).

And there can be a public DNS record but it doesn't say anything about ports. And the CT transparency log doesn't say anything about ports or IP addresses.

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tptacek 659 days ago
I don't know that you're right about the WireGuard CPU expense thing.
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Jnr 659 days ago
My router (with Wireguard) can't handle more than 45Mbit/s through Wireguard because the CPU starts throttling.

I suspect that RaspberryPi or old Intel NUC also would not be able to handle speeds anywhere near gigabit.

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tptacek 659 days ago
My NUC easily pegs the network. I'm not sure you're right about this. Either way: you can just use WireGuard as a control channel, the same way this software does.
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