1 files changed, 39 insertions, 4 deletions
diff --git a/nixos/modules/services/networking/mosquitto.nix b/nixos/modules/services/networking/mosquitto.nix
index 10b49d9b220..b98a717e658 100644
--- a/nixos/modules/services/networking/mosquitto.nix
+++ b/nixos/modules/services/networking/mosquitto.nix
@@ -233,15 +233,50 @@ in
         ExecStart = "${pkgs.mosquitto}/bin/mosquitto -c ${mosquittoConf}";
         ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
 
-        ProtectSystem = "strict";
-        ProtectHome = true;
+        # Hardening
+        CapabilityBoundingSet = "";
+        DevicePolicy = "closed";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        NoNewPrivileges = true;
         PrivateDevices = true;
         PrivateTmp = true;
-        ReadWritePaths = "${cfg.dataDir}";
+        PrivateUsers = true;
+        ProtectClock = true;
         ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
         ProtectKernelModules = true;
         ProtectKernelTunables = true;
-        NoNewPrivileges = true;
+        ProtectProc = "invisible";
+        ProcSubset = "pid";
+        ProtectSystem = "strict";
+        ReadWritePaths = [
+          cfg.dataDir
+          "/tmp"  # mosquitto_passwd creates files in /tmp before moving them
+        ];
+        ReadOnlyPaths = with cfg.ssl; lib.optionals (enable) [
+          certfile
+          keyfile
+          cafile
+        ];
+        RemoveIPC = true;
+        RestrictAddressFamilies = [
+          "AF_UNIX"  # for sd_notify() call
+          "AF_INET"
+          "AF_INET6"
+        ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        SystemCallArchitectures = "native";
+        SystemCallFilter = [
+          "@system-service"
+          "~@privileged"
+          "~@resources"
+        ];
+        UMask = "0077";
       };
       preStart = ''
         rm -f ${cfg.dataDir}/passwd