knot: add keyFiles option

This useful to include tsig keys using nixops without adding those
world-readable to the nix store.

nixos/modules/services/networking/knot.nix

@@ -5,14 +5,16 @@ with lib;
 let
   cfg = config.services.knot;
 
-  configFile = pkgs.writeText "knot.conf" cfg.extraConfig;
-  socketFile = "/run/knot/knot.sock";
+  configFile = pkgs.writeTextFile {
+    name = "knot.conf";
+    text = (concatMapStringsSep "\n" (file: "include: ${file}") cfg.keyFiles) + "\n" +
+           cfg.extraConfig;
+    checkPhase = lib.optionalString (cfg.keyFiles == []) ''
+      ${cfg.package}/bin/knotc --config=$out conf-check
+    '';
+  };
 
-  knotConfCheck = file: pkgs.runCommand "knot-config-checked"
-    { buildInputs = [ cfg.package ]; } ''
-    ln -s ${configFile} $out
-    knotc --config=${configFile} conf-check
-  '';
+  socketFile = "/run/knot/knot.sock";
 
   knot-cli-wrappers = pkgs.stdenv.mkDerivation {
     name = "knot-cli-wrappers";
@@ -45,6 +47,19 @@ in {
         '';
       };
 
+      keyFiles = mkOption {
+        type = types.listOf types.path;
+        default = [];
+        description = ''
+          A list of files containing additional configuration
+          to be included using the include directive. This option
+          allows to include configuration like TSIG keys without
+          exposing them to the nix store readable to any process.
+          Note that using this option will also disable configuration
+          checks at build time.
+        '';
+      };
+
       extraConfig = mkOption {
         type = types.lines;
         default = "";
@@ -81,7 +96,7 @@ in {
 
       serviceConfig = {
         Type = "notify";
-        ExecStart = "${cfg.package}/bin/knotd --config=${knotConfCheck configFile} --socket=${socketFile} ${concatStringsSep " " cfg.extraArgs}";
+        ExecStart = "${cfg.package}/bin/knotd --config=${configFile} --socket=${socketFile} ${concatStringsSep " " cfg.extraArgs}";
         ExecReload = "${knot-cli-wrappers}/bin/knotc reload";
         CapabilityBoundingSet = "CAP_NET_BIND_SERVICE CAP_SETPCAP";
         AmbientCapabilities = "CAP_NET_BIND_SERVICE CAP_SETPCAP";

nixos/tests/knot.nix

@@ -28,6 +28,13 @@ let
     name = "knot-zones";
     paths = [ exampleZone delegatedZone ];
   };
+  # DO NOT USE pkgs.writeText IN PRODUCTION. This put secrets in the nix store!
+  tsigFile = pkgs.writeText "tsig.conf" ''
+    key:
+      - id: slave_key
+        algorithm: hmac-sha256
+        secret: zOYgOgnzx3TGe5J5I/0kxd7gTcxXhLYMEq3Ek3fY37s=
+  '';
 in {
   name = "knot";
   meta = with pkgs.stdenv.lib.maintainers; {
@@ -48,6 +55,7 @@ in {
       };
       services.knot.enable = true;
       services.knot.extraArgs = [ "-v" ];
+      services.knot.keyFiles = [ tsigFile ];
       services.knot.extraConfig = ''
         server:
             listen: 0.0.0.0@53
@@ -56,6 +64,7 @@ in {
         acl:
           - id: slave_acl
             address: 192.168.0.2
+            key: slave_key
             action: transfer
 
         remote:
@@ -103,6 +112,7 @@ in {
         ];
       };
       services.knot.enable = true;
+      services.knot.keyFiles = [ tsigFile ];
       services.knot.extraArgs = [ "-v" ];
       services.knot.extraConfig = ''
         server:
@@ -117,6 +127,7 @@ in {
         remote:
           - id: master
             address: 192.168.0.1@53
+            key: slave_key
 
         template:
           - id: default
@@ -155,10 +166,10 @@ in {
         ];
       };
       environment.systemPackages = [ pkgs.knot-dns ];
-    };    
+    };
   };
 
-  testScript = { nodes, ... }: let 
+  testScript = { nodes, ... }: let
     master4 = (lib.head nodes.master.config.networking.interfaces.eth1.ipv4.addresses).address;
     master6 = (lib.head nodes.master.config.networking.interfaces.eth1.ipv6.addresses).address;