Merge pull request #108578 from ctem/feature/chrony

nixos/chrony: add support for Network Time Security (NTS) authentication

nixos/modules/services/networking/ntp/chrony.nix

@@ -4,13 +4,14 @@ with lib;
 
 let
   cfg = config.services.chrony;
+  chronyPkg = cfg.package;
 
-  stateDir = "/var/lib/chrony";
+  stateDir = cfg.directory;
   driftFile = "${stateDir}/chrony.drift";
   keyFile = "${stateDir}/chrony.keys";
 
   configFile = pkgs.writeText "chrony.conf" ''
-    ${concatMapStringsSep "\n" (server: "server " + server + " iburst") cfg.servers}
+    ${concatMapStringsSep "\n" (server: "server " + server + " " + cfg.serverOption + optionalString (cfg.enableNTS) " nts") cfg.servers}
 
     ${optionalString
       (cfg.initstepslew.enabled && (cfg.servers != []))
@@ -19,6 +20,7 @@ let
 
     driftfile ${driftFile}
     keyfile ${keyFile}
+    ${optionalString (cfg.enableNTS) "ntsdumpdir ${stateDir}"}
 
     ${optionalString (!config.time.hardwareClockInLocalTime) "rtconutc"}
 
@@ -39,6 +41,15 @@ in
         '';
       };
 
+      package = mkOption {
+        type = types.package;
+        default = pkgs.chrony;
+        defaultText = "pkgs.chrony";
+        description = ''
+          Which chrony package to use.
+        '';
+      };
+
       servers = mkOption {
         default = config.networking.timeServers;
         type = types.listOf types.str;
@@ -47,6 +58,29 @@ in
         '';
       };
 
+      serverOption = mkOption {
+        default = "iburst";
+        type = types.enum [ "iburst" "offline" ];
+        description = ''
+          Set option for server directives.
+
+          Use "iburst" to rapidly poll on startup. Recommended if your machine
+          is consistently online.
+
+          Use "offline" to prevent polling on startup. Recommended if your
+          machine boots offline or is otherwise frequently offline.
+        '';
+      };
+
+      enableNTS = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to enable Network Time Security authentication.
+          Make sure it is supported by your selected NTP server(s).
+        '';
+      };
+
       initstepslew = mkOption {
         default = {
           enabled = true;
@@ -59,6 +93,12 @@ in
         '';
       };
 
+      directory = mkOption {
+        type = types.str;
+        default = "/var/lib/chrony";
+        description = "Directory where chrony state is stored.";
+      };
+
       extraConfig = mkOption {
         type = types.lines;
         default = "";
@@ -80,7 +120,7 @@ in
   config = mkIf cfg.enable {
     meta.maintainers = with lib.maintainers; [ thoughtpolice ];
 
-    environment.systemPackages = [ pkgs.chrony ];
+    environment.systemPackages = [ chronyPkg ];
 
     users.groups.chrony.gid = config.ids.gids.chrony;
 
@@ -110,12 +150,12 @@ in
         after    = [ "network.target" ];
         conflicts = [ "ntpd.service" "systemd-timesyncd.service" ];
 
-        path = [ pkgs.chrony ];
+        path = [ chronyPkg ];
 
         unitConfig.ConditionCapability = "CAP_SYS_TIME";
         serviceConfig =
           { Type = "simple";
-            ExecStart = "${pkgs.chrony}/bin/chronyd ${chronyFlags}";
+            ExecStart = "${chronyPkg}/bin/chronyd ${chronyFlags}";
 
             ProtectHome = "yes";
             ProtectSystem = "full";