Does the server get a separate wg interface for every client that connects? Or does it do something like multipoint GRE interfaces with next hop addresses in the arp table?
Does this do a DH key agreement to guarantee forward secrecy or does it literally encrypt the packet with the peers public key?
Also is it in the scope of this project for peers to discover each other for direct communication, like a Phase3 DMVPN?
No. Each wg interface has a public/private key. It then has a list of peers' public keys and associated allowed IPs. By tying each public key to the allowed IPs of that public key, you can be sure that if a packet comes from wg0 and comes from a particular src IP, it comes from who you want. So no need for a new wg0 for each peer.
> Does this do a DH key agreement to guarantee forward secrecy or does it literally encrypt the packet with the peers public key?
It uses a 1-RTT ECDH key agreement based on the Noise Protocol Framework, with identity hiding, perfect forward secrecy, and so forth. So, it does what you hoped it does. :)
> Phase3 DMVPN
I'm not familiar with this, but I'll read up on it. Just found a large cisco document describing it. I suspect that "automatic discovery" wouldn't be very much to my taste, but I'll read up on it before dismissing it wholesale.
If I understand wireguard correctly it seems NHRP could be run using wiregard for transport, but it would cool if a separate NHRP daemon wasn't required, especially since wiregard is already tracking the mapping of internal to public IPs.
> No. Each wg interface has a public/private key. It then has a list of peers' public keys and associated allowed IPs. By tying each public key to the allowed IPs of that public key, you can be sure that if a packet comes from wg0 and comes from a particular src IP, it comes from who you want. So no need for a new wg0 for each peer.
Does this mean that it is impossible for two clients to connect to the same VPN server from behind router doing NAT? Or does each client choose a random source port for their traffic and then the combination of source port and source IP identifies the client?