1 files changed, 167 insertions, 0 deletions
diff --git a/modules/stalwart-mail.nix b/modules/stalwart-mail.nix
new file mode 100644
index 0000000..ebeedd9
--- /dev/null
+++ b/modules/stalwart-mail.nix
@@ -0,0 +1,167 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.stalwart-mail;
+  configFormat = pkgs.formats.toml { };
+  configFile = configFormat.generate "stalwart-mail.toml" cfg.settings;
+  dataDir = "/var/lib/stalwart-mail";
+
+  readTOML =
+    path:
+    builtins.fromTOML (builtins.unsafeDiscardStringContext (lib.readFile path));
+  recursiveUpdateList =
+    attrList:
+    lib.lists.foldr (a1: a2: lib.attrsets.recursiveUpdate a1 a2) {} attrList;
+  mkOverrideRec =
+    priority:
+    content:
+    if lib.isAttrs content then
+      lib.mapAttrs (_: v: mkOverrideRec priority v) content
+    else
+      lib.mkOverride priority content;
+  mkOptionDefaultRec = mkOverrideRec 1500;
+
+  cfgPkg = pkgs.callPackage ../pkgs/stalwart-mail-config.nix {};
+  cfgFiles = (readTOML "${cfgPkg}/config.toml").include.files;
+  settingsDefault = recursiveUpdateList (map (path: readTOML path) cfgFiles);
+in {
+  options.services.stalwart-mail = {
+    enable = mkEnableOption (mdDoc "the Stalwart all-in-one email server");
+    package = mkPackageOption pkgs "stalwart-mail" { };
+
+    loadCredential = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      default = [];
+      example = [ "dkim.private:/path/to/stalwart.private" ];
+      description = lib.mdDoc ''
+        This can be used to pass secrets to the systemd service without adding them to
+        the nix store.
+        See the LoadCredential section of systemd.exec manual for more information.
+      '';
+    };
+
+    settings = mkOption {
+      inherit (configFormat) type;
+      default = { };
+      description = mdDoc ''
+        Configuration options for the Stalwart email server.
+        See <https://stalw.art/docs/category/configuration> for available options.
+
+        By default, the module is configured to store everything locally.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    # set the default upstream settings
+    # assumptions
+    # 1. ./config.toml exists and only containts include.files and macros
+    # 2. no other files containts include.files
+    services.stalwart-mail.settings = mkOptionDefaultRec
+      (lib.attrsets.recursiveUpdate settingsDefault {
+        macros.base_path = dataDir;
+        server.run-as.user = {};
+        server.run-as.group = {};
+        global.tracing.method = "stdout";
+        # outliers as of v0.6.0
+        acme."letsencrypt".cache = "${cfg.settings.macros.base_path}/acme";
+      });
+
+    assertions = let 
+      m = cfg.settings.macros;
+
+      mkMacroMessage =
+        opt:
+        "config.stalwart-mail.settings.macros.${opt} can not be empty";
+    in [
+      {
+        assertion = m ? host
+                    && m.host != ""
+                    && m.host != null;
+        message = mkMacroMessage "host";
+      }
+      {
+        assertion = m ? default_domain
+                    && m.default_domain != ""
+                    && m.default_domain != null;
+        message = mkMacroMessage "default_domain";
+      }
+      {
+        assertion = m ? default_directory
+                    && m.default_directory != ""
+                    && m.default_directory != null;
+        message = mkMacroMessage "default_directory";
+      }
+      {
+        assertion = m ? default_store &&
+                    m.default_store != ""
+                    && m.default_store != null;
+        message = mkMacroMessage "default_store";
+      }
+    ];
+
+    systemd.services.stalwart-mail = {
+      wantedBy = [ "multi-user.target" ];
+      after = [ "local-fs.target" "network.target" ];
+
+      serviceConfig = {
+        ExecStart =
+          "${cfg.package}/bin/stalwart-mail --config=${configFile}";
+
+        # Base from template resources/systemd/stalwart-mail.service
+        Type = "simple";
+        LimitNOFILE = 65536;
+        KillMode = "process";
+        KillSignal = "SIGINT";
+        Restart = "on-failure";
+        RestartSec = 5;
+        StandardOutput = "journal";
+        StandardError = "journal";
+        SyslogIdentifier = "stalwart-mail";
+
+        DynamicUser = true;
+        User = "stalwart-mail";
+        StateDirectory = "stalwart-mail";
+        LoadCredential = cfg.loadCredential;
+
+        # Bind standard privileged ports
+        AmbientCapabilities = [ "CAP_NET_BIND_SERVICE" ];
+        CapabilityBoundingSet = [ "CAP_NET_BIND_SERVICE" ];
+
+        # Hardening
+        DeviceAllow = [ "" ];
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        PrivateDevices = true;
+        PrivateUsers = false;  # incompatible with CAP_NET_BIND_SERVICE
+        ProcSubset = "pid";
+        PrivateTmp = true;
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectProc = "invisible";
+        ProtectSystem = "strict";
+        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        SystemCallArchitectures = "native";
+        SystemCallFilter = [ "@system-service" "~@privileged" ];
+        UMask = "0077";
+      };
+    };
+
+    # Make admin commands available in the shell
+    environment.systemPackages = [ cfg.package ];
+  };
+
+  meta = {
+    maintainers = with maintainers; [ happysalada pacien ];
+  };
+}