caddy service: initial implementation

nixos/modules/misc/ids.nix

@@ -259,6 +259,7 @@
       hydra-www = 236;
       syncthing = 237;
       mfi = 238;
+      caddy = 239;
 
       # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!
 
@@ -489,6 +490,7 @@
       radicale = 234;
       syncthing = 237;
       #mfi = 238; # unused
+      caddy = 239;
 
       # When adding a gid, make sure it doesn't match an existing
       # uid. Users and groups with the same name should have equal

nixos/modules/module-list.nix

@@ -433,6 +433,7 @@
   ./services/ttys/kmscon.nix
   ./services/web-apps/pump.io.nix
   ./services/web-servers/apache-httpd/default.nix
+  ./services/web-servers/caddy.nix
   ./services/web-servers/fcgiwrap.nix
   ./services/web-servers/jboss/default.nix
   ./services/web-servers/lighttpd/cgit.nix

nixos/modules/services/web-servers/caddy.nix

@@ -0,0 +1,53 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.caddy;
+  configFile = pkgs.writeText "Caddyfile" cfg.config;
+in
+{
+  options.services.caddy = {
+    enable = mkEnableOption "Caddy web server";
+
+    config = mkOption {
+      description = "Verbatim Caddyfile to use";
+    };
+
+    email = mkOption {
+      default = "";
+      type = types.string;
+      description = "Email address (for Let's Encrypt certificate)";
+    };
+
+    dataDir = mkOption {
+      default = "/var/lib/caddy";
+      type = types.path;
+      description = "The data directory, for storing certificates.";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.caddy = {
+      description = "Caddy web server";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        ExecStart = "${pkgs.caddy}/bin/caddy -conf=${configFile} -email=${cfg.email}";
+	Type = "simple";
+	User = "caddy";
+	Group = "caddy";
+	AmbientCapabilities = "cap_net_bind_service";
+      };
+    };
+
+    users.extraUsers.caddy = {
+      group = "caddy";
+      uid = config.ids.uids.caddy;
+      home = cfg.dataDir;
+      createHome = true;
+    };
+
+    users.extraGroups.caddy.gid = config.ids.uids.caddy;
+  };
+}