nixos/nitter: systemd unit hardening

nixos/modules/services/misc/nitter.nix

@@ -312,6 +312,31 @@ in
           AmbientCapabilities = lib.mkIf (cfg.server.port < 1024) [ "CAP_NET_BIND_SERVICE" ];
           Restart = "on-failure";
           RestartSec = "5s";
+          # Hardening
+          CapabilityBoundingSet = if (cfg.server.port < 1024) then [ "CAP_NET_BIND_SERVICE" ] else [ "" ];
+          DeviceAllow = [ "" ];
+          LockPersonality = true;
+          MemoryDenyWriteExecute = true;
+          PrivateDevices = true;
+          # A private user cannot have process capabilities on the host's user
+          # namespace and thus CAP_NET_BIND_SERVICE has no effect.
+          PrivateUsers = (cfg.server.port >= 1024);
+          ProcSubset = "pid";
+          ProtectClock = true;
+          ProtectControlGroups = true;
+          ProtectHome = true;
+          ProtectHostname = true;
+          ProtectKernelLogs = true;
+          ProtectKernelModules = true;
+          ProtectKernelTunables = true;
+          ProtectProc = "invisible";
+          RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+          RestrictNamespaces = true;
+          RestrictRealtime = true;
+          RestrictSUIDSGID = true;
+          SystemCallArchitectures = "native";
+          SystemCallFilter = [ "@system-service" "~@privileged" "~@resources" ];
+          UMask = "0077";
         };
     };