From 72b8bd089c6fd8d05183c1adc402f308aee1e7c2 Mon Sep 17 00:00:00 2001
From: Jack O'Sullivan <jackos1998@gmail.com>
Date: Wed, 22 Jan 2025 19:19:03 +0000
Subject: [PATCH] nixos/uk: Add WireGuard VPN for access

---
 lib/constants.nix          |  9 ++++++
 nixos/boxes/britnet.nix    | 56 ++++++++++++++++++++++++++++++++++++--
 secrets/britnet/wg.key.age | 13 +++++++++
 3 files changed, 75 insertions(+), 3 deletions(-)
 create mode 100644 secrets/britnet/wg.key.age

diff --git a/lib/constants.nix b/lib/constants.nix
index e9c046d..0feb28e 100644
--- a/lib/constants.nix
+++ b/lib/constants.nix
@@ -337,6 +337,15 @@ rec {
   britnet = {
     domain = "bhx1.int.${pubDomain}";
     pubV4 = "77.74.199.67";
+    vpn = {
+      port = 51820;
+    };
+    prefixes = with lib.my.net.cidr; rec {
+      vpn = {
+        v4 = "10.200.0.0/24";
+        v6 = "fdfb:5ebf:6e84::/64";
+      };
+    };
   };
 
   tailscale = {
diff --git a/nixos/boxes/britnet.nix b/nixos/boxes/britnet.nix
index 1f03455..22e3df9 100644
--- a/nixos/boxes/britnet.nix
+++ b/nixos/boxes/britnet.nix
@@ -2,7 +2,7 @@
 let
   inherit (lib.my) net;
   inherit (lib.my.c) pubDomain;
-  inherit (lib.my.c.britnet) domain pubV4;
+  inherit (lib.my.c.britnet) domain pubV4 prefixes;
 in
 {
   nixos.systems.britnet = {
@@ -22,6 +22,13 @@ in
           gateway = "2a12:ab46:5344::1";
         };
       };
+      vpn = {
+        ipv4 = {
+          address = net.cidr.host 1 prefixes.vpn.v4;
+          gateway = null;
+        };
+        ipv6.address = net.cidr.host 1 prefixes.vpn.v6;
+      };
     };
 
     configuration = { lib, pkgs, modulesPath, config, assignments, allAssignments, ... }:
@@ -65,6 +72,12 @@ in
               };
             };
 
+            environment = {
+              systemPackages = with pkgs; [
+                wireguard-tools
+              ];
+            };
+
             services = {
               iperf3 = {
                 enable = true;
@@ -89,6 +102,28 @@ in
             networking = { inherit domain; };
 
             systemd.network = {
+              netdevs = {
+                "30-wg0" = {
+                  netdevConfig = {
+                    Name = "wg0";
+                    Kind = "wireguard";
+                  };
+                  wireguardConfig = {
+                    PrivateKeyFile = config.age.secrets."britnet/wg.key".path;
+                    ListenPort = lib.my.c.britnet.vpn.port;
+                  };
+                  wireguardPeers = [
+                    {
+                      PublicKey = "EfPwREfZ/q3ogHXBIqFZh4k/1NRJRyq4gBkBXtegNkE=";
+                      AllowedIPs = [
+                        (net.cidr.host 10 prefixes.vpn.v4)
+                        (net.cidr.host 10 prefixes.vpn.v6)
+                      ];
+                    }
+                  ];
+                };
+              };
+
               links = {
                 "10-veth0" = {
                   matchConfig.PermanentMACAddress = "00:db:d9:62:68:1a";
@@ -110,6 +145,12 @@ in
                     ];
                   }
                 ];
+                "30-wg0" = mkMerge [
+                  (networkdAssignment "wg0" assignments.vpn)
+                  {
+                    networkConfig.IPv6AcceptRA = mkForce false;
+                  }
+                ];
               };
             };
 
@@ -119,16 +160,25 @@ in
                 key = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJIEx+1EC/lN6WKIaOB+O5LJgVHRK962YpZEPQg/m78O";
                 files = {
                   "tailscale-auth.key" = {};
+                  "britnet/wg.key" = {
+                    owner = "systemd-network";
+                  };
                 };
               };
 
               firewall = {
+                udp.allowed = [ lib.my.c.britnet.vpn.port ];
                 trustedInterfaces = [ "tailscale0" ];
                 extraRules = ''
+                  table inet filter {
+                    chain forward {
+                      iifname wg0 oifname veth0 accept
+                    }
+                  }
                   table inet nat {
                     chain postrouting {
-                      iifname tailscale0 oifname veth0 snat ip to ${assignments.allhost.ipv4.address}
-                      iifname tailscale0 oifname veth0 snat ip6 to ${assignments.allhost.ipv6.address}
+                      iifname { tailscale0, wg0 } oifname veth0 snat ip to ${assignments.allhost.ipv4.address}
+                      iifname { tailscale0, wg0 } oifname veth0 snat ip6 to ${assignments.allhost.ipv6.address}
                     }
                   }
                 '';
diff --git a/secrets/britnet/wg.key.age b/secrets/britnet/wg.key.age
new file mode 100644
index 0000000..5256c81
--- /dev/null
+++ b/secrets/britnet/wg.key.age
@@ -0,0 +1,13 @@
+-----BEGIN AGE ENCRYPTED FILE-----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+-----END AGE ENCRYPTED FILE-----