1 files changed, 86 insertions, 0 deletions
diff --git a/nixos/modules/services/networking/croc.nix b/nixos/modules/services/networking/croc.nix
new file mode 100644
index 00000000000..9466adf71d8
--- /dev/null
+++ b/nixos/modules/services/networking/croc.nix
@@ -0,0 +1,86 @@
+{ config, lib, pkgs, ... }:
+let
+  inherit (lib) types;
+  cfg = config.services.croc;
+  rootDir = "/run/croc";
+in
+{
+  options.services.croc = {
+    enable = lib.mkEnableOption "croc relay";
+    ports = lib.mkOption {
+      type = with types; listOf port;
+      default = [9009 9010 9011 9012 9013];
+      description = "Ports of the relay.";
+    };
+    pass = lib.mkOption {
+      type = with types; either path str;
+      default = "pass123";
+      description = "Password or passwordfile for the relay.";
+    };
+    openFirewall = lib.mkEnableOption "opening of the peer port(s) in the firewall";
+    debug = lib.mkEnableOption "debug logs";
+  };
+
+  config = lib.mkIf cfg.enable {
+    systemd.services.croc = {
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        ExecStart = "${pkgs.croc}/bin/croc --pass '${cfg.pass}' ${lib.optionalString cfg.debug "--debug"} relay --ports ${lib.concatMapStringsSep "," toString cfg.ports}";
+        # The following options are only for optimizing:
+        # systemd-analyze security croc
+        AmbientCapabilities = "";
+        CapabilityBoundingSet = "";
+        DynamicUser = true;
+        # ProtectClock= adds DeviceAllow=char-rtc r
+        DeviceAllow = "";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        MountAPIVFS = true;
+        NoNewPrivileges = true;
+        PrivateDevices = true;
+        PrivateMounts = true;
+        PrivateNetwork = lib.mkDefault false;
+        PrivateTmp = true;
+        PrivateUsers = true;
+        ProcSubset = "pid";
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectProc = "noaccess";
+        ProtectSystem = "strict";
+        RemoveIPC = true;
+        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        RootDirectory = rootDir;
+        # Avoid mounting rootDir in the own rootDir of ExecStart='s mount namespace.
+        InaccessiblePaths = [ "-+${rootDir}" ];
+        BindReadOnlyPaths = [
+          builtins.storeDir
+        ] ++ lib.optional (types.path.check cfg.pass) cfg.pass;
+        # This is for BindReadOnlyPaths=
+        # to allow traversal of directories they create in RootDirectory=.
+        UMask = "0066";
+        # Create rootDir in the host's mount namespace.
+        RuntimeDirectory = [(baseNameOf rootDir)];
+        RuntimeDirectoryMode = "700";
+        SystemCallFilter = [
+          "@system-service"
+          "~@aio" "~@keyring" "~@memlock" "~@privileged" "~@resources" "~@setuid" "~@sync" "~@timer"
+        ];
+        SystemCallArchitectures = "native";
+        SystemCallErrorNumber = "EPERM";
+      };
+    };
+
+    networking.firewall.allowedTCPPorts = lib.mkIf cfg.openFirewall cfg.ports;
+  };
+
+  meta.maintainers = with lib.maintainers; [ hax404 julm ];
+}