Merge pull request #324 from naturallaw777/copilot/fix-rdp-boot-time-setup

fix(rdp): prepend /run/wrappers/bin to PATH and add pkexec preflight check

app/tests/test_rdp_module_boot_setup.py

@@ -0,0 +1,122 @@
+import unittest
+from pathlib import Path
+
+
+RDP_NIX = Path(__file__).resolve().parents[2] / "modules" / "rdp.nix"
+USERNAME_READ = "USERNAME=\"$(tr -d '\\n' < \"$USERNAME_FILE\")\""
+USERNAME_LENGTH_GUARD = "if [ \"''${#USERNAME}\" -gt 32 ]; then"
+SHORT_PASSWORD_GUARD = 'if [ "\'\'${#PASSWORD}" -lt 8 ]; then'
+
+
+def _section(source: str, start: str, end: str) -> str:
+    start_idx = source.find(start)
+    if start_idx == -1:
+        raise AssertionError(f"Expected section start not found: {start!r}")
+    end_idx = source.find(end, start_idx)
+    if end_idx == -1:
+        raise AssertionError(f"Expected section end not found: {end!r}")
+    return source[start_idx:end_idx]
+
+
+class RdpModuleBootSetupTests(unittest.TestCase):
+    def setUp(self):
+        self.source = RDP_NIX.read_text()
+        self.gnome_service = _section(
+            self.source,
+            "systemd.services.gnome-remote-desktop = {",
+            "systemd.tmpfiles.rules = [",
+        )
+        self.setup_service = _section(
+            self.source,
+            "systemd.services.gnome-remote-desktop-setup = {",
+            "};\n}",
+        )
+
+    def test_does_not_redeclare_gnome_remote_desktop_user(self):
+        self.assertNotIn("users.users.gnome-remote-desktop", self.source)
+        self.assertNotIn("createHome = true;", self.source)
+
+    def test_main_service_requires_setup_before_starting(self):
+        self.assertIn('wantedBy = [ "graphical.target" ];', self.gnome_service)
+        self.assertIn('after = [ "gnome-remote-desktop-setup.service" ];', self.gnome_service)
+        self.assertIn('requires = [ "gnome-remote-desktop-setup.service" ];', self.gnome_service)
+
+    def test_setup_waits_for_configuration_service_and_bounded_timeout(self):
+        self.assertIn('wantedBy = [ "graphical.target" ];', self.setup_service)
+        self.assertIn('before = [ "gnome-remote-desktop.service" ];', self.setup_service)
+        self.assertIn('"dbus.service"', self.setup_service)
+        self.assertIn('"gnome-remote-desktop-configuration.service"', self.setup_service)
+        self.assertNotIn("RemainAfterExit", self.setup_service)
+        self.assertIn('TimeoutStartSec = "2min";', self.setup_service)
+        self.assertIn('timeout --kill-after=5s 10s', self.setup_service)
+        self.assertIn('echo "grdctl command timed out: $*" >&2', self.setup_service)
+        self.assertIn('echo "grdctl command failed (exit $rc): $*" >&2', self.setup_service)
+
+    def test_setup_runs_grdctl_directly_as_root(self):
+        # The oneshot service runs as root; grdctl --system is called directly.
+        # GRD 50.x invokes pkexec internally, but the call itself is plain
+        # grdctl --system, not a manual pkexec invocation.
+        self.assertIn('grdctl --system "$@"', self.setup_service)
+        self.assertNotIn("runuser", self.setup_service)
+        self.assertNotIn("sudo", self.setup_service)
+        # No direct Nix-store pkexec invocation (pkgs.polkit}/bin/pkexec).
+        self.assertNotIn("pkgs.polkit}/bin/pkexec", self.setup_service)
+
+    def test_privilege_escalation_packages_absent_from_setup_path(self):
+        self.assertNotIn("pkgs.polkit", self.setup_service)
+        self.assertNotIn("pkgs.util-linux", self.setup_service)
+
+    def test_run_wrappers_bin_prepended_to_path(self):
+        # /run/wrappers/bin must be prepended to PATH before any grdctl_system
+        # invocation so that grdctl --system resolves the NixOS setuid pkexec.
+        path_export = 'export PATH="/run/wrappers/bin:$PATH"'
+        grdctl_marker = "grdctl_system"
+        script = self.setup_service
+        path_idx = script.find(path_export)
+        grdctl_idx = script.find(grdctl_marker)
+        self.assertGreater(path_idx, -1, f"{path_export!r} not found in setup script")
+        self.assertGreater(
+            grdctl_idx, path_idx,
+            "PATH export must appear before the first grdctl_system usage",
+        )
+
+    def test_pkexec_preflight_check(self):
+        # A preflight must confirm /run/wrappers/bin/pkexec is executable
+        # with a clear error message before any GRD configuration changes.
+        self.assertIn("test -x /run/wrappers/bin/pkexec", self.setup_service)
+        self.assertIn(
+            "/run/wrappers/bin/pkexec is absent or not executable",
+            self.setup_service,
+        )
+
+    def test_hub_files_are_the_source_of_truth_for_username_and_password(self):
+        self.assertIn('DEFAULT_USERNAME="sovran"', self.setup_service)
+        self.assertIn('if [ ! -f "$USERNAME_FILE" ]; then', self.setup_service)
+        self.assertIn(USERNAME_READ, self.setup_service)
+        self.assertIn(USERNAME_LENGTH_GUARD, self.setup_service)
+        self.assertIn('case "$USERNAME" in', self.setup_service)
+        self.assertIn('[A-Za-z_][A-Za-z0-9_-]*)', self.setup_service)
+        self.assertIn("RDP username is too long (''${#USERNAME} characters, maximum 32)", self.setup_service)
+        self.assertIn("RDP username must start with a letter or underscore and contain only letters, numbers, underscores, and hyphens", self.setup_service)
+        self.assertIn('if [ ! -f "$PASSWORD_FILE" ]; then', self.setup_service)
+        self.assertIn("tr -d '\\n'", self.setup_service)
+        self.assertIn('"$PASSWORD_FILE"', self.setup_service)
+        self.assertIn(SHORT_PASSWORD_GUARD, self.setup_service)
+        self.assertIn("RDP password is too short (''${#PASSWORD} characters, minimum 8)", self.setup_service)
+        self.assertIn('grdctl_system rdp set-credentials "$USERNAME" "$PASSWORD"', self.setup_service)
+        self.assertNotIn('grdctl --system rdp set-credentials sovran "$PASSWORD"', self.setup_service)
+
+    def test_secure_permissions_are_enforced_for_state_and_secret_files(self):
+        self.assertIn('"d /var/lib/gnome-remote-desktop/tls 0700', self.source)
+        self.assertIn("chmod 700", self.setup_service)
+        self.assertIn('chmod 600 "$USERNAME_FILE"', self.setup_service)
+        self.assertIn('chmod 600 "$PASSWORD_FILE"', self.setup_service)
+        self.assertIn('chmod 600 "$CRED_FILE"', self.setup_service)
+        self.assertIn('chmod 600 "$TLS_DIR/rdp-tls.key"', self.setup_service)
+        self.assertIn('chmod 644 "$TLS_DIR/rdp-tls.crt"', self.setup_service)
+        self.assertIn('LOCAL_IP="$(hostname -I | awk \'{print $1}\')"', self.setup_service)
+        self.assertIn('LOCAL_IP="127.0.0.1"', self.setup_service)
+
+
+if __name__ == "__main__":
+    unittest.main()

flake.lock

@@ -5,11 +5,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1783086783,
-        "narHash": "sha256-NxXpNF/9tq2nI+SxFHUxjro3u11SF3l4vs7bawdMKkQ=",
+        "lastModified": 1783519926,
+        "narHash": "sha256-2zwAN4lNitHFrHVnRZG3YcvpdtWOoF0cOBstxMeB1KI=",
         "owner": "emmanuelrosa",
         "repo": "btc-clients-nix",
-        "rev": "4f6d07cae877ef58f0fbc9e731c99800ddb80859",
+        "rev": "731a1e11c2fefb14f0aa4b1f03cfa85c19c28d71",
         "type": "github"
       },
       "original": {
@@ -139,11 +139,11 @@
     },
     "nixpkgs-stable": {
       "locked": {
-        "lastModified": 1782999065,
-        "narHash": "sha256-5Dgj5+pIQYZKrXUGaLCk7CKfN3MmpwIhO94++WVxvng=",
+        "lastModified": 1783856661,
+        "narHash": "sha256-ZGP04e+Q6WyQJGA9ZvI5CL6+heGQldbAG9U1T9NGvmU=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "80d591ed473cfc46329932c2aadac9b435342c7c",
+        "rev": "569d578509928497eddc3fdbf94a799027050be4",
         "type": "github"
       },
       "original": {
@@ -187,11 +187,11 @@
     },
     "nixpkgs_3": {
       "locked": {
-        "lastModified": 1782959384,
-        "narHash": "sha256-xnJJk+ct+D2+wdRxj1wk36w5zV9RVESwRqcklPdt3fM=",
+        "lastModified": 1783776592,
+        "narHash": "sha256-UgCQzxeWI75XM8G+hPrPh+MKzEPjG3SpAj7dtqSbksA=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "65179426c83bb3f6bc14898b42ea1c6f01d374b0",
+        "rev": "e7a3ca8092b61ff85b6a45bf863ea2b2d6a661b3",
         "type": "github"
       },
       "original": {
@@ -203,11 +203,11 @@
     },
     "nixpkgs_4": {
       "locked": {
-        "lastModified": 1782948114,
-        "narHash": "sha256-AXmz9ho4Lud5CsbrZsuSVwpQZ4o5FgZ1chxBn5cJ8+0=",
+        "lastModified": 1783791668,
+        "narHash": "sha256-zbcZ1dmBTPfJ7Mlqh/yLEPGpgJnwuv4Xr1xucy2WqMA=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "9e92285f211dad236540fd617d7e30e0b99bc0e1",
+        "rev": "716c7a2664ca8325617b8a7fbb609273f2c4cae7",
         "type": "github"
       },
       "original": {
@@ -224,11 +224,11 @@
         "systems": "systems_2"
       },
       "locked": {
-        "lastModified": 1783173302,
-        "narHash": "sha256-nlnOw/zsD2H2NHSZ5oNWwcjuM17vipyAapfXsO78GjY=",
+        "lastModified": 1783941741,
+        "narHash": "sha256-F+3M1IZrJa920cx2/k2AMKqedEodxLF7COJVkLJwUBo=",
         "owner": "nix-community",
         "repo": "nixvim",
-        "rev": "a402fdf2a1ef297d8ea7c95b90d6af0dbe90ab11",
+        "rev": "e6715f01d9f56f07a27a01386b85ae22b06f0705",
         "type": "github"
       },
       "original": {

modules/element-calling.nix

@@ -72,17 +72,30 @@ $MATRIX {
 }
 
 $ELEMENT_CALLING {
-  handle /livekit/jwt/sfu/get {
+  # Route all current lk-jwt-service authorization endpoints to port 8073,
+  # stripping the /livekit/jwt prefix that Caddy adds on the public URL.
+  @lk_jwt path /livekit/jwt/sfu/get* /livekit/jwt/get_token* /livekit/jwt/healthz* /livekit/jwt/sfu_webhook* /livekit/jwt/delegate_delayed_leave*
+  handle @lk_jwt {
     uri strip_prefix /livekit/jwt
     reverse_proxy [::1]:8073 {
       header_up Host {host}
       header_up X-Forwarded-Server {host}
       header_up X-Real-IP {remote_host}
       header_up X-Forwarded-For {remote_host}
+      header_up X-Forwarded-Proto {scheme}
     }
   }
   handle {
-    reverse_proxy localhost:7880
+    reverse_proxy localhost:7880 {
+      header_up Host {host}
+      header_up X-Forwarded-Proto {scheme}
+      header_up X-Forwarded-For {remote_host}
+      header_up X-Real-IP {remote_host}
+      transport http {
+        read_timeout 300s
+        write_timeout 300s
+      }
+    }
   }
 }
 EOF
@@ -94,8 +107,11 @@ EOF
   #   * reads the matrix domain from /var/lib/domains/matrix (never hardcoded)
   #   * copies Caddy's already-issued matrix cert/key into /var/lib/livekit
   #     so LoadCredential can stage them for the (DynamicUser) livekit unit
-  #   * writes a complete LiveKit config (with turn.domain substituted) that the
-  #     overridden ExecStart loads.
+  #   * detects the primary network interface from the IPv4 default route so
+  #     LiveKit only advertises real ICE candidates — not VPN/container/private
+  #     addresses from interfaces like Tailscale or Docker bridges
+  #   * writes a complete LiveKit config (with turn.domain and interface
+  #     substituted) that the overridden ExecStart loads.
   systemd.services.livekit-turn-setup = {
     description = "Stage TURN cert and generate LiveKit runtime config from domain files";
     after = [ "caddy.service" "livekit-key-setup.service" ];
@@ -109,7 +125,7 @@ EOF
     unitConfig = {
       ConditionPathExists = "/var/lib/domains/element-calling";
     };
-    path = [ pkgs.coreutils pkgs.findutils ];
+    path = [ pkgs.coreutils pkgs.findutils pkgs.iproute2 pkgs.gawk ];
     script = ''
       MATRIX=$(cat /var/lib/domains/matrix)
 
@@ -123,16 +139,37 @@ EOF
       cp "$KEY" /var/lib/livekit/turn.key
       chmod 640 /var/lib/livekit/turn.crt /var/lib/livekit/turn.key
 
-      # Generate the full LiveKit config the daemon will load. turn.domain is
-      # only known at runtime, so it is substituted here. The cert/key paths
-      # point at the LoadCredential-staged copies under /run/credentials.
+      # Detect the primary network interface from the IPv4 default route.
+      # Restricting LiveKit to this single interface prevents it from
+      # advertising VPN/container/private ICE candidates (e.g. Tailscale,
+      # Docker bridges) that remote peers cannot reach, which causes all
+      # ICE negotiation attempts to fail with responsesReceived: 0.
+      IFACE=$(ip -4 route show default | awk '/^default/ { for(i=1;i<=NF;i++) if($i=="dev" && (i+1)<=NF) { print $(i+1); exit } }')
+      if [ -z "$IFACE" ]; then
+        echo "ERROR: Could not detect a default-route network interface from 'ip -4 route show default'." >&2
+        echo "ERROR: Cannot generate a valid LiveKit config without a real interface to bind ICE candidates to." >&2
+        echo "ERROR: Ensure a default IPv4 route is configured, e.g.: ip route add default via <gateway> dev <interface>" >&2
+        echo "ERROR: Inspect the current routing table with: ip -4 route show" >&2
+        exit 1
+      fi
+      echo "Detected primary network interface: $IFACE"
+
+      # Generate the full LiveKit config the daemon will load. turn.domain and
+      # rtc.interfaces.includes are only known at runtime, so they are
+      # substituted here. The cert/key paths point at the LoadCredential-staged
+      # copies under /run/credentials.
       cat > /run/livekit/livekit.yaml <<EOF
 port: 7880
 rtc:
   use_external_ip: true
+  skip_external_ip_validation: true
+  tcp_port: 7881
   udp_port: 7882
   port_range_start: 30000
   port_range_end: 40000
+  interfaces:
+    includes:
+      - $IFACE
 room:
   auto_create: false
 turn:
@@ -155,6 +192,8 @@ EOF
     keyFile = livekitKeyFile;
     settings = {
       rtc.use_external_ip = true;
+      rtc.skip_external_ip_validation = true;
+      rtc.tcp_port = 7881;
       rtc.udp_port = 7882;
       rtc.port_range_start = 30000;
       rtc.port_range_end = 40000;
@@ -186,6 +225,9 @@ EOF
 
   networking.firewall.allowedTCPPorts = [ 5349 7881 ];
   networking.firewall.allowedUDPPorts = [ 3478 7882 ];
+  networking.firewall.allowedUDPPortRanges = [
+    { from = 30000; to = 40000; } # LiveKit internal TURN relay range
+  ];
 
   ####### JWT SERVICE RUNTIME CONFIG #######
   systemd.services.lk-jwt-service-runtime-config = {
@@ -204,11 +246,13 @@ EOF
     path = [ pkgs.coreutils ];
     script = ''
       ELEMENT_CALLING=$(cat /var/lib/domains/element-calling)
+      MATRIX=$(cat /var/lib/domains/matrix)
 
       mkdir -p /run/lk-jwt-service
 
       cat > /run/lk-jwt-service/env <<EOF
 LIVEKIT_URL=wss://$ELEMENT_CALLING
+LIVEKIT_FULL_ACCESS_HOMESERVERS=$MATRIX
 EOF
 
       chmod 640 /run/lk-jwt-service/env

modules/rdp.nix

@@ -2,70 +2,104 @@
 
 lib.mkIf config.sovran_systemsOS.features.rdp {
 
-  users.users.gnome-remote-desktop = {
-    isSystemUser = true;
-    group = "gnome-remote-desktop";
-    home = "/var/lib/gnome-remote-desktop";
-    createHome = true;
-  };
-  users.groups.gnome-remote-desktop = {};
-
   # Enable the GNOME Remote Desktop service at the system level
   services.gnome.gnome-remote-desktop.enable = true;
 
   # Open RDP port in the firewall
   networking.firewall.allowedTCPPorts = [ 3389 ];
 
-  # Ensure the service actually starts and waits for setup to complete
+  # Ensure the service only starts after setup succeeds
   systemd.services.gnome-remote-desktop = {
     wantedBy = [ "graphical.target" ];
     after = [ "gnome-remote-desktop-setup.service" ];
-    wants = [ "gnome-remote-desktop-setup.service" ];
+    requires = [ "gnome-remote-desktop-setup.service" ];
   };
 
   systemd.tmpfiles.rules = [
-    "d /var/lib/gnome-remote-desktop 0750 gnome-remote-desktop gnome-remote-desktop -"
-    "d /var/lib/gnome-remote-desktop/.local 0750 gnome-remote-desktop gnome-remote-desktop -"
-    "d /var/lib/gnome-remote-desktop/.local/share 0750 gnome-remote-desktop gnome-remote-desktop -"
-    "d /var/lib/gnome-remote-desktop/.local/share/gnome-remote-desktop 0750 gnome-remote-desktop gnome-remote-desktop -"
+    "d /var/lib/gnome-remote-desktop/.local 0700 gnome-remote-desktop gnome-remote-desktop -"
+    "d /var/lib/gnome-remote-desktop/.local/share 0700 gnome-remote-desktop gnome-remote-desktop -"
+    "d /var/lib/gnome-remote-desktop/.local/share/gnome-remote-desktop 0700 gnome-remote-desktop gnome-remote-desktop -"
+    "d /var/lib/gnome-remote-desktop/tls 0700 gnome-remote-desktop gnome-remote-desktop -"
   ];
 
   systemd.services.gnome-remote-desktop-setup = {
     description = "Configure GNOME Remote Desktop RDP";
-    wantedBy = [ "multi-user.target" ];
+    wantedBy = [ "graphical.target" ];
     before = [ "gnome-remote-desktop.service" ];
-    after = [ "systemd-tmpfiles-setup.service" "network-online.target" ];
-    wants = [ "network-online.target" ];
+    after = [
+      "dbus.service"
+      "systemd-tmpfiles-setup.service"
+      "network-online.target"
+      "gnome-remote-desktop-configuration.service"
+    ];
+    wants = [
+      "network-online.target"
+      "gnome-remote-desktop-configuration.service"
+    ];
     serviceConfig = {
       Type = "oneshot";
-      RemainAfterExit = true;
+      TimeoutStartSec = "2min";
     };
     path = [
-      pkgs.gnome-remote-desktop
-      pkgs.polkit
-      pkgs.openssl
-      pkgs.hostname
+      pkgs.coreutils
       pkgs.gawk
+      pkgs.gnome-remote-desktop
+      pkgs.hostname
+      pkgs.openssl
+      pkgs.systemd
     ];
     script = ''
-      # Ensure directory structure exists
-      mkdir -p /var/lib/gnome-remote-desktop/.local/share/gnome-remote-desktop
-      chown -R gnome-remote-desktop:gnome-remote-desktop /var/lib/gnome-remote-desktop
+      set -euo pipefail
 
-      TLS_DIR="/var/lib/gnome-remote-desktop/tls"
-      CRED_FILE="/var/lib/gnome-remote-desktop/rdp-credentials"
+      # GRD 50.x invokes pkexec internally for every grdctl --system call, even
+      # when the caller is root.  NixOS exposes the required setuid wrapper at
+      # /run/wrappers/bin/pkexec; the Nix-store polkit binary is not setuid and
+      # must not shadow it.  Prepend the wrapper directory so every subsequent
+      # grdctl --system resolves the correct binary.
+      export PATH="/run/wrappers/bin:$PATH"
+
+      STATE_DIR="/var/lib/gnome-remote-desktop"
+      TLS_DIR="$STATE_DIR/tls"
+      USERNAME_FILE="$STATE_DIR/rdp-username"
+      PASSWORD_FILE="$STATE_DIR/rdp-password"
+      CRED_FILE="$STATE_DIR/rdp-credentials"
+      DEFAULT_USERNAME="sovran"
+
+      grdctl_system() {
+        local rc=0
+
+        if timeout --kill-after=5s 10s \
+          grdctl --system "$@"; then
+          return 0
+        else
+          rc=$?
+        fi
+
+        if [ "$rc" -eq 124 ] || [ "$rc" -eq 137 ]; then
+          echo "grdctl command timed out: $*" >&2
+        fi
+        echo "grdctl command failed (exit $rc): $*" >&2
+
+        return "$rc"
+      }
+
+      mkdir -p "$STATE_DIR/.local/share/gnome-remote-desktop" "$TLS_DIR"
+      chown -R gnome-remote-desktop:gnome-remote-desktop "$STATE_DIR"
+      chmod 700 \
+        "$STATE_DIR" \
+        "$STATE_DIR/.local" \
+        "$STATE_DIR/.local/share" \
+        "$STATE_DIR/.local/share/gnome-remote-desktop" \
+        "$TLS_DIR"
 
-      # Regenerate TLS certificate if missing OR if ownership is wrong
-      # (disable/re-enable cycle can break ownership or grdctl state)
       NEED_REGEN=0
       if [ ! -f "$TLS_DIR/rdp-tls.crt" ] || [ ! -f "$TLS_DIR/rdp-tls.key" ]; then
         NEED_REGEN=1
-      elif [ "$(stat -c '%U' "$TLS_DIR/rdp-tls.key" 2>/dev/null)" != "gnome-remote-desktop" ]; then
+      elif [ "$(stat -c '%U:%G' "$TLS_DIR/rdp-tls.key" 2>/dev/null)" != "gnome-remote-desktop:gnome-remote-desktop" ]; then
         NEED_REGEN=1
       fi
 
       if [ "$NEED_REGEN" = "1" ]; then
-        mkdir -p "$TLS_DIR"
         rm -f "$TLS_DIR/rdp-tls.key" "$TLS_DIR/rdp-tls.crt"
         openssl req -x509 -newkey ec -pkeyopt ec_paramgen_curve:prime256v1 \
           -sha256 -nodes -days 3650 \
@@ -75,39 +109,59 @@ lib.mkIf config.sovran_systemsOS.features.rdp {
         echo "Generated new RDP TLS certificate"
       fi
 
-      # Always fix ownership and permissions (handles re-enable after disable)
-      chown -R gnome-remote-desktop:gnome-remote-desktop "$TLS_DIR"
+      chown gnome-remote-desktop:gnome-remote-desktop "$TLS_DIR/rdp-tls.key" "$TLS_DIR/rdp-tls.crt"
       chmod 600 "$TLS_DIR/rdp-tls.key"
       chmod 644 "$TLS_DIR/rdp-tls.crt"
 
-      # Configure TLS certificate
-      grdctl --system rdp set-tls-cert "$TLS_DIR/rdp-tls.crt"
-      grdctl --system rdp set-tls-key "$TLS_DIR/rdp-tls.key"
+      if [ ! -f "$USERNAME_FILE" ]; then
+        printf '%s\n' "$DEFAULT_USERNAME" > "$USERNAME_FILE"
+      fi
+      USERNAME="$(tr -d '\n' < "$USERNAME_FILE")"
+      if [ -z "$USERNAME" ]; then
+        USERNAME="$DEFAULT_USERNAME"
+        printf '%s\n' "$USERNAME" > "$USERNAME_FILE"
+      fi
+      if [ "''${#USERNAME}" -gt 32 ]; then
+        echo "RDP username is too long (''${#USERNAME} characters, maximum 32): $USERNAME from $USERNAME_FILE" >&2
+        exit 1
+      fi
+      case "$USERNAME" in
+        [A-Za-z_][A-Za-z0-9_-]*)
+          ;;
+        *)
+          echo "RDP username must start with a letter or underscore and contain only letters, numbers, underscores, and hyphens: $USERNAME from $USERNAME_FILE" >&2
+          exit 1
+          ;;
+      esac
+      chown gnome-remote-desktop:gnome-remote-desktop "$USERNAME_FILE"
+      chmod 600 "$USERNAME_FILE"
 
-      # Generate password on first boot only
-      PASSWORD=""
-      if [ ! -f /var/lib/gnome-remote-desktop/rdp-password ]; then
-        PASSWORD=$(openssl rand -base64 16)
-        echo "$PASSWORD" > /var/lib/gnome-remote-desktop/rdp-password
-        chmod 600 /var/lib/gnome-remote-desktop/rdp-password
-      else
-        PASSWORD=$(cat /var/lib/gnome-remote-desktop/rdp-password)
+      if [ ! -f "$PASSWORD_FILE" ]; then
+        openssl rand -base64 16 > "$PASSWORD_FILE"
+      fi
+      PASSWORD="$(tr -d '\n' < "$PASSWORD_FILE")"
+      if [ -z "$PASSWORD" ]; then
+        echo "RDP password file is empty: $PASSWORD_FILE" >&2
+        exit 1
+      fi
+      if [ "''${#PASSWORD}" -lt 8 ]; then
+        echo "RDP password is too short (''${#PASSWORD} characters, minimum 8): $PASSWORD_FILE" >&2
+        exit 1
+      fi
+      chown gnome-remote-desktop:gnome-remote-desktop "$PASSWORD_FILE"
+      chmod 600 "$PASSWORD_FILE"
+
+      LOCAL_IP="$(hostname -I | awk '{print $1}')"
+      if [ -z "$LOCAL_IP" ]; then
+        LOCAL_IP="127.0.0.1"
       fi
 
-      # Write username to a separate file for the hub
-      echo "sovran" > /var/lib/gnome-remote-desktop/rdp-username
-      chmod 600 /var/lib/gnome-remote-desktop/rdp-username
-
-      # Get current IP address
-      LOCAL_IP=$(hostname -I | awk '{print $1}')
-
-      # Always rewrite the credentials file with the current IP
       cat > "$CRED_FILE" <<EOF
       ========================================
        GNOME Remote Desktop (RDP) Credentials
       ========================================
 
-       Username: sovran
+       Username: $USERNAME
        Password: $PASSWORD
 
        Connect from any RDP client to:
@@ -116,11 +170,22 @@ lib.mkIf config.sovran_systemsOS.features.rdp {
       ========================================
       EOF
 
+      chown gnome-remote-desktop:gnome-remote-desktop "$CRED_FILE"
       chmod 600 "$CRED_FILE"
 
-      # Enable RDP backend and set credentials
-      grdctl --system rdp enable
-      grdctl --system rdp set-credentials sovran "$PASSWORD"
+      # Preflight: the NixOS setuid pkexec wrapper must be present and executable
+      # before any grdctl --system call.  Absence means the system was booted
+      # without security.wrappers or the wrapper directory is not mounted yet.
+      if ! test -x /run/wrappers/bin/pkexec; then
+        echo "Preflight check failed: /run/wrappers/bin/pkexec is absent or not executable." >&2
+        echo "GNOME Remote Desktop system configuration requires the NixOS setuid pkexec wrapper at /run/wrappers/bin/pkexec." >&2
+        exit 1
+      fi
+
+      grdctl_system rdp enable
+      grdctl_system rdp set-tls-cert "$TLS_DIR/rdp-tls.crt"
+      grdctl_system rdp set-tls-key "$TLS_DIR/rdp-tls.key"
+      grdctl_system rdp set-credentials "$USERNAME" "$PASSWORD"
 
       echo "GNOME Remote Desktop RDP configured successfully"
     '';