flake.nix

@@ -117,6 +117,92 @@
             ${lib.optionalString (!serviceIdentityTestsPass) "exit 1"}
             touch $out
           '';
+
+          reverse-proxy-basic-route =
+            let
+              testConfig =
+                (lib.nixosSystem {
+                  system = "x86_64-linux";
+                  specialArgs.my = self.lib;
+                  modules = [
+                    ./modules/reverse-proxy.nix
+                    {
+                      modules.reverse-proxy = {
+                        enable = true;
+                        routes."budget.alexion.dev" = {
+                          path = "/";
+                          backend = "http://10.23.20.42:5006";
+                        };
+                      };
+                    }
+                  ];
+                }).config;
+              vhost = testConfig.services.nginx.virtualHosts."budget.alexion.dev";
+            in
+            pkgs.runCommand "reverse-proxy-basic-route-check" { } ''
+              ${
+                lib.optionalString (
+                  !(vhost.forceSSL && vhost.enableACME && vhost.locations."/".proxyPass == "http://10.23.20.42:5006")
+                ) "exit 1"
+              }
+              touch $out
+            '';
+
+          reverse-proxy-actualbudget-guest-route =
+            let
+              testConfig =
+                (self.nixosConfigurations.pikachu.extendModules {
+                  modules = [
+                    {
+                      guests.actualbudget.reverseProxy = {
+                        enable = true;
+                        host = "budget.alexion.dev";
+                        backend = "http://10.23.20.42:5006";
+                      };
+                    }
+                  ];
+                }).config;
+              route = testConfig.modules.reverse-proxy.routes.actualbudget;
+            in
+            pkgs.runCommand "reverse-proxy-actualbudget-guest-route-check" { } ''
+              ${
+                lib.optionalString (
+                  !(route.host == "budget.alexion.dev" && route.backend == "http://10.23.20.42:5006")
+                ) "exit 1"
+              }
+              touch $out
+            '';
+
+          reverse-proxy-secondary-path-requires-root =
+            let
+              testConfig =
+                (lib.nixosSystem {
+                  system = "x86_64-linux";
+                  specialArgs.my = self.lib;
+                  modules = [
+                    ./modules/reverse-proxy.nix
+                    {
+                      modules.reverse-proxy = {
+                        enable = true;
+                        routes.raichu-files = {
+                          host = "files.alexion.dev";
+                          path = "/raichu";
+                          backend = "http://10.23.20.10:3923";
+                        };
+                      };
+                    }
+                  ];
+                }).config;
+              hasFailedRootAssertion = lib.any (
+                assertion:
+                assertion.assertion == false
+                && assertion.message == "modules.reverse-proxy.routes for files.alexion.dev must include a primary / route."
+              ) testConfig.assertions;
+            in
+            pkgs.runCommand "reverse-proxy-secondary-path-requires-root-check" { } ''
+              ${lib.optionalString (!hasFailedRootAssertion) "exit 1"}
+              touch $out
+            '';
         };
     };
 }

guests/reverse-proxy.nix

@@ -0,0 +1,51 @@
+{
+  config,
+  lib,
+  my,
+  ...
+}:
+let
+  legacyBackend = "http://10.23.20.32";
+  legacyHosts = [
+    "games.alexion.dev"
+    "git.alexion.dev"
+    "music.alexion.dev"
+    "photos.alexion.dev"
+    "plex.alexion.dev"
+    "servers.alexion.dev"
+    "todo.alexion.dev"
+    "wings.alexion.dev"
+  ];
+  legacyRoutes = lib.listToAttrs (
+    map (host: {
+      name = "legacy-${lib.replaceStrings [ "." ] [ "-" ] host}";
+      value = {
+        inherit host;
+        backend = legacyBackend;
+      };
+    }) legacyHosts
+  );
+in
+{
+  imports = [
+    (my.guest {
+      name = "reverse-proxy";
+      interior = {
+        modules.reverse-proxy = {
+          enable = true;
+          routes = config.modules.reverse-proxy.routes // legacyRoutes;
+        };
+      };
+    })
+  ];
+
+  config = lib.mkIf config.guests.reverse-proxy.enable {
+    guests.reverse-proxy = {
+      limits = {
+        memory = lib.mkDefault "1G";
+        cpu = lib.mkDefault "100%";
+        tasksMax = lib.mkDefault 256;
+      };
+    };
+  };
+}

hosts/pikachu/default.nix

@@ -79,6 +79,17 @@
     vlan = 20;
     mac = "BC:24:11:C1:CD:28";
     dataPath = "/pikachu/data/actualbudget";
+    reverseProxy = {
+      enable = true;
+      host = "budget.alexion.dev";
+      backend = "http://10.23.20.42:5006";
+    };
+  };
+
+  guests.reverse-proxy = {
+    enable = true;
+    vlan = 20;
+    mac = "02:98:64:5a:07:4f";
   };
 
   guests.copyparty = {

lib/default.nix

@@ -14,6 +14,8 @@ let
     ;
 
   serviceIdentityRegistry = import ./service-identities.nix { inherit lib; };
+  reverseProxyRoutes = import ./reverse-proxy-routes.nix { inherit lib; };
+
   collectNixFiles =
     dir:
     flatten (
@@ -44,6 +46,7 @@ let
       self
       specialArgs
       bridgeName
+      reverseProxyRoutes
       ;
   };
 
@@ -81,6 +84,7 @@ in
     mkHost
     mkHosts
     bridgeName
+    reverseProxyRoutes
     ;
 
   inherit (guests) deriveMac guest;

lib/guests.nix

@@ -3,6 +3,7 @@
   self,
   specialArgs,
   bridgeName,
+  reverseProxyRoutes,
 }:
 let
   inherit (lib) escapeShellArg mapAttrsToList;
@@ -130,6 +131,10 @@ let
             guest takes its address by DHCP, keeping IP management at the router.
           '';
         };
+        reverseProxy = reverseProxyRoutes.mkRouteOptions {
+          subject = "guest route";
+          enableDefault = false;
+        };
         mounts = lib.mkOption {
           type = lib.types.attrsOf (
             lib.types.submodule {
@@ -273,6 +278,10 @@ let
       config = lib.mkIf cfg.enable {
         sops.secrets = lib.genAttrs cfg.secrets (_: { });
 
+        modules.reverse-proxy.routes.${machineName} = lib.mkIf cfg.reverseProxy.enable (
+          reverseProxyRoutes.routeFields cfg.reverseProxy
+        );
+
         assertions = [
           {
             assertion = mountCollisions == [ ];

lib/reverse-proxy-routes.nix

@@ -0,0 +1,77 @@
+{ lib }:
+let
+  mkRouteOptions =
+    {
+      name ? null,
+      subject ? "route",
+      enableDefault ? true,
+    }:
+    {
+      enable = lib.mkOption {
+        type = lib.types.bool;
+        default = enableDefault;
+        description = "Whether this reverse-proxy ${subject} is active.";
+      };
+
+      host = lib.mkOption (
+        {
+          type = lib.types.str;
+          description = "Primary hostname served by this reverse-proxy ${subject}.";
+        }
+        // lib.optionalAttrs (name != null) {
+          default = name;
+          defaultText = lib.literalMD "the route attribute name";
+        }
+      );
+
+      aliases = lib.mkOption {
+        type = lib.types.listOf lib.types.str;
+        default = [ ];
+        description = "Additional hostnames served by this reverse-proxy ${subject}.";
+      };
+
+      path = lib.mkOption {
+        type = lib.types.str;
+        default = "/";
+        description = "URL path prefix proxied by this reverse-proxy ${subject}.";
+      };
+
+      backend = lib.mkOption {
+        type = lib.types.str;
+        description = "Full HTTP backend URL that receives proxied traffic.";
+      };
+
+      tls = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = "Whether to serve this reverse-proxy ${subject} with ACME-backed TLS.";
+      };
+
+      websockets = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = "Whether to enable websocket proxy headers for this reverse-proxy ${subject}.";
+      };
+    };
+
+  routeFields = route: {
+    inherit (route)
+      host
+      aliases
+      path
+      backend
+      tls
+      websockets
+      ;
+  };
+in
+{
+  inherit mkRouteOptions routeFields;
+
+  routeType = lib.types.submodule (
+    { name, ... }:
+    {
+      options = mkRouteOptions { inherit name; };
+    }
+  );
+}

modules/reverse-proxy.nix

@@ -0,0 +1,82 @@
+{ config, lib, my, ... }:
+let
+  cfg = config.modules.reverse-proxy;
+  inherit (my) reverseProxyRoutes;
+
+  enabledRoutes = lib.filterAttrs (_: route: route.enable) cfg.routes;
+  routesByHost = lib.groupBy (route: route.host) (lib.attrValues enabledRoutes);
+
+  rootRoutesByHost = lib.mapAttrs (
+    host: routes:
+    let
+      roots = builtins.filter (route: route.path == "/") routes;
+    in
+    if roots == [ ] then null else builtins.head roots
+  ) routesByHost;
+
+  hasDuplicatePaths = routes:
+    let
+      paths = map (route: route.path) routes;
+    in
+    lib.length paths != lib.length (lib.unique paths);
+
+  mkLocation = route: {
+    proxyPass = route.backend;
+    proxyWebsockets = route.websockets;
+  };
+
+  mkVirtualHost = host: routes:
+    let
+      rootRoute = rootRoutesByHost.${host};
+    in
+    lib.mkIf (rootRoute != null) {
+      forceSSL = rootRoute.tls;
+      enableACME = rootRoute.tls;
+      serverAliases = rootRoute.aliases;
+      locations = lib.listToAttrs (
+        map (route: lib.nameValuePair route.path (mkLocation route)) routes
+      );
+    };
+in
+{
+  options.modules.reverse-proxy = {
+    enable = lib.mkEnableOption "the Nginx reverse proxy route realizer";
+
+    routes = lib.mkOption {
+      type = lib.types.attrsOf reverseProxyRoutes.routeType;
+      default = { };
+      description = "Reverse-proxy route declarations keyed by stable route name.";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    assertions =
+      lib.mapAttrsToList (host: rootRoute: {
+        assertion = rootRoute != null;
+        message = "modules.reverse-proxy.routes for ${host} must include a primary / route.";
+      }) rootRoutesByHost
+      ++ lib.mapAttrsToList (host: routes: {
+        assertion = !hasDuplicatePaths routes;
+        message = "modules.reverse-proxy.routes for ${host} must not declare the same path more than once.";
+      }) routesByHost;
+
+    networking.firewall.allowedTCPPorts = [
+      80
+      443
+    ];
+
+    security.acme = {
+      acceptTerms = true;
+      defaults.email = "contact@alexion.dev";
+    };
+
+    services.nginx = {
+      enable = true;
+      recommendedGzipSettings = true;
+      recommendedOptimisation = true;
+      recommendedProxySettings = true;
+      recommendedTlsSettings = true;
+      virtualHosts = lib.mapAttrs mkVirtualHost routesByHost;
+    };
+  };
+}

modules/services/actualbudget.nix

@@ -40,6 +40,7 @@ in
       default = "storage";
       description = "Group account that owns Actual Budget's writable state.";
     };
+
   };
 
   config = lib.mkIf cfg.enable {