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wireguard provisioning

motivation

Based on this Freifunk project proposal I'd summarize the following two requirements of existing mesh communities:

  • Public IPv4 & IPv6 addresses to nodes in a mesh network
  • Remote access to nodes (if desired) to help non-technical users

Optional:

  • Encrypted traffic to a trusted gateway over an unencrypted wireless mesh network

Idea

Nodes are pre setup with the address and credentials of a VPN server. On node boot a VPN client is configured and tries to connect to the VPN server.

The VPN server should be very simple to setup and allow configuration of IPv4/6 forwarding to connected clients, also allow NAT for specified addresses.

Possible technology

VPN part

Wireguard could solve this issue with minimal configuration hassle, low storage impact on nodes and good bandwidth performance when used for uplink connections.

Problem is the negotiation of addresses as wireguard does not support DHCP for clients like other VPN services may do. Automatic IP provisioning is required.

As the public key of the server is preset there is no risk of MITM attacks. So the clients process of receiving it IP address(es) doesn't require special security measures.

The VPN server interface would allow administrators to automatically assign free addresses to connecting nodes or set specific addresses to known public key of clients.

Internal mesh routing

Assigning public addresses to hosts via a VPN can result in unnecessary routing as two connecting nodes use the VPN as gateway which traffic is then forwarded to the VPNs client node. This could drastically slow down internal mesh connection. A possible solution for this problem is to let the used mesh routing protocol announce it's public IP address to the rest of the mesh network. A simple configuration of this is found in the package lime-proto-bmx7.

Possible implementation

Manual assignment

Currently just a shell script running on the VPN server which should be a OpenWrt node.

The server hosts all content of ./public with disabled autoindex. Client will generate a fresh wireguard private key on first boot and tries to fetch a free ip from vpn ip/sha256 of pubkey. On success the client setups wireguard and starts using it. On fail, retry after x.

The clients public key could be shown in a simplified web interface like lime-app and allow the users to request vpn access by the vpn provider.

This approach could provide people secure connections (to a gateway) within an unencrypted mesh network and public IPv{4,6} provided by the gateway.

Automatic assignment

tba

server

  • WIREGUARD_IP: ip for the wireguard interface with subnet
  • WIREGUARD_CLIENTS: (generated) file which contain the ips + public key
  • PRIVATE_KEY: guess

usage

  • set an adequate ip in WIREGUARD_IP
  • run ./wg-pro.sh to create an initial config file
  • edit WIREGUARD_CLIENTS adding public keys of clients (and may comments)
  • run ./wg-pro.sh again to create uci config and fill ./public folder

client

tba