jitterentropy-rngd: update module for 1.3.1

Signed-off-by: Markus Theil <theil.markus@gmail.com>

nixos/modules/services/security/jitterentropy-rngd.nix

@@ -11,12 +11,53 @@ in
   options.services.jitterentropy-rngd = {
     enable = lib.mkEnableOption "jitterentropy-rngd service configuration";
     package = lib.mkPackageOption pkgs "jitterentropy-rngd" { };
+    osr = lib.mkOption {
+      type = lib.types.ints.between 3 20;
+      default = 3;
+      description = "Oversampling rate for jitterentropy (3 to 20)";
+    };
+    flags = lib.mkOption {
+      type = lib.types.int;
+      default = 0;
+      description = "Additional flags to pass to jitterentropy";
+    };
+    forceSP800-90B = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = "Force SP800-90B mode for entropy reading";
+    };
+    verbose = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = "Enable verbose log messages";
+    };
   };
 
-  config = lib.mkIf cfg.enable {
-    systemd.packages = [ cfg.package ];
-    systemd.services."jitterentropy".wantedBy = [ "basic.target" ];
-  };
+  config =
+    let
+      # use identical arguments for status and service execution,
+      # in order to get meaningful output
+      args =
+        "--osr ${builtins.toString cfg.osr} --flags ${builtins.toString cfg.flags}"
+        + lib.optionalString cfg.forceSP800-90B " --sp800-90b"
+        + lib.optionalString cfg.verbose " -vvv";
+    in
+    lib.mkIf cfg.enable {
+      systemd.packages = [ cfg.package ];
+      systemd.services."jitterentropy".wantedBy = [ "basic.target" ];
+      systemd.services."jitterentropy".serviceConfig = {
+        # logs used configuration for comparison
+        ExecStartPre = [
+          "-${cfg.package}/bin/jitterentropy-rngd --status ${args}"
+        ];
+        ExecStart = [
+          # clear old setting from built-in service file
+          ""
+          # use service from package with our configured args
+          "${cfg.package}/bin/jitterentropy-rngd ${args}"
+        ];
+      };
+    };
 
   meta.maintainers = with lib.maintainers; [ thillux ];
 }