nix-config/services/wireguard.nix

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# A simple, in-kernel VPN service
#
# Strongly inspired by [1].
# [1]: https://github.com/delroth/infra.delroth.net/blob/master/roles/wireguard-peer.nix
{ config, lib, pkgs, ... }:
let
cfg = config.my.services.wireguard;
hostName = config.networking.hostName;
peers = config.my.secrets.wireguard.peers;
thisPeer = peers."${hostName}";
otherPeers = lib.filterAttrs (name: _: name != hostName) peers;
in
{
options.my.services.wireguard = with lib; {
enable = mkEnableOption "Wireguard VPN service";
iface = mkOption {
type = types.str;
default = "wg";
example = "wg0";
description = "Name of the interface to configure";
};
port = mkOption {
type = types.port;
default = 51820;
example = 55555;
description = "Port to configure for Wireguard";
};
net = {
v4 = {
subnet = mkOption {
type = types.str;
default = "10.0.0";
example = "10.100.0";
description = "Which prefix to use for internal IPs";
};
mask = mkOption {
type = types.int;
default = 24;
example = 28;
description = "The CIDR mask to use on internal IPs";
};
};
v6 = {
subnet = mkOption {
type = types.str;
default = "fd42:42:42";
example = "fdc9:281f:04d7:9ee9";
description = "Which prefix to use for internal IPs";
};
mask = mkOption {
type = types.int;
default = 64;
example = 68;
description = "The CIDR mask to use on internal IPs";
};
};
};
};
config.networking = lib.mkIf cfg.enable {
wireguard.interfaces."${cfg.iface}" = {
listenPort = cfg.port;
ips = with cfg.net; with lib; [
"${v4.subnet}.${toString thisPeer.clientNum}/${toString v4.mask}"
"${v6.subnet}::${toString thisPeer.clientNum}/${toHexString v6.mask}"
];
# Insecure, I don't care
privateKey = thisPeer.privateKey;
peers = lib.mapAttrsToList
(_: peer: {
inherit (peer) publicKey;
} // lib.optionalAttrs (thisPeer ? externalIp) {
# Only forward from server to clients
allowedIPs = with cfg.net; [
"${v4.subnet}.${toString peer.clientNum}/32"
"${v6.subnet}::${toString peer.clientNum}/128"
];
} // lib.optionalAttrs (peer ? externalIp) {
# Known addresses
endpoint = "${peer.externalIp}:${toString cfg.port}";
} // lib.optionalAttrs (!(thisPeer ? externalIp)) {
# Forward all traffic to server
allowedIPs = with cfg.net; [
"0.0.0.0/0"
"::/0"
];
# Roaming clients need to keep NAT-ing active
persistentKeepalive = 10;
})
otherPeers;
} // lib.optionalAttrs (thisPeer ? externalIp) {
# Setup forwarding on server
# FIXME: 'eth0' should not hard-coded
postSetup = with cfg.net; ''
${pkgs.iptables}/bin/iptables -t nat -A POSTROUTING -s ${v4.subnet}.0/${toString v4.mask} -o eth0 -j MASQUERADE
${pkgs.iptables}/bin/ip6tables -t nat -A POSTROUTING -s ${v6.subnet}::0/${toString v6.mask} -o eth0 -j MASQUERADE
'';
postShutdown = with cfg.net; ''
${pkgs.iptables}/bin/iptables -t nat -D POSTROUTING -s ${v4.subnet}.0/${toString v4.mask} -o eth0 -j MASQUERADE
${pkgs.iptables}/bin/ip6tables -t nat -D POSTROUTING -s ${v6.subnet}::0/${toString v6.mask} -o eth0 -j MASQUERADE
'';
};
nat = lib.optionalAttrs (thisPeer ? externalIp) {
enable = true;
externalInterface = "eth0"; # FIXME: should not hard-coded
internalInterfaces = [ cfg.iface ];
};
firewall.allowedUDPPorts = lib.optional (thisPeer ? externalIp) cfg.port;
};
}