nixos/znc: harden systemd unit

nixos/modules/services/networking/znc/default.nix

@@ -258,6 +258,34 @@ in
         ExecStart = "${pkgs.znc}/bin/znc --foreground --datadir ${cfg.dataDir} ${escapeShellArgs cfg.extraFlags}";
         ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
         ExecStop = "${pkgs.coreutils}/bin/kill -INT $MAINPID";
+        # Hardening
+        CapabilityBoundingSet = [ "" ];
+        DevicePolicy = "closed";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        NoNewPrivileges = true;
+        PrivateDevices = true;
+        PrivateTmp = true;
+        PrivateUsers = true;
+        ProcSubset = "pid";
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectProc = "invisible";
+        ProtectSystem = "strict";
+        ReadWritePaths = [ cfg.dataDir ];
+        RemoveIPC = true;
+        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        SystemCallArchitectures = "native";
+        SystemCallFilter = [ "@system-service" "~@privileged" "~@resources" ];
+        UMask = "0027";
       };
       preStart = ''
         mkdir -p ${cfg.dataDir}/configs