Initial framework: reusable modules, lib, pkgs, overlays, scripts, sample environment

2026-05-10 19:06:58 +02:00
commit c53d997d07
32 changed files with 1339 additions and 0 deletions
@@ -0,0 +1,116 @@
+{ config, pkgs, lib, ... }:
+
+let
+  cfg = config.services.dns;
+  dnsPkg = if cfg.package != null then cfg.package else pkgs.technitium-dns-server;
+
+  # Build the config.json for Technitium DNS Server.
+  # The server reads this file on startup from its config directory.
+  configJson = {
+    WebServicePort = cfg.webPort;
+    DNSListenerPort = cfg.dnsPort;
+    Recursion = cfg.recursion;
+    Forwarders = cfg.forwarders;
+    Log = false;
+    CachePrefetch = false;
+    AllowTtlOverride = true;
+  } // lib.optionalAttrs (cfg.adminPasswordFile != null) {
+    # Password hash will be set by the activation script on first run
+    # using the value from adminPasswordFile.
+  } // lib.optionalAttrs (cfg.listenAddresses != [ ]) {
+    ListenAddresses = cfg.listenAddresses;
+  } // lib.optionalAttrs (cfg.allowZoneTransfer != [ ]) {
+    AllowZoneTransfer = cfg.allowZoneTransfer;
+  } // cfg.extraConfig;
+
+  configFile = pkgs.writeText "technitium-dns-config.json"
+    (builtins.toJSON configJson);
+in
+
+{
+  imports = [
+    ./options.nix
+  ];
+
+  config = lib.mkIf cfg.enable {
+
+    environment.systemPackages = [ dnsPkg ];
+
+    # Create the config directory and deploy initial config.json
+    systemd.tmpfiles.rules = [
+      "d ${cfg.configDir} 0750 dns dns - -"
+    ];
+
+    systemd.services.technitium-dns-server = {
+      description = "Technitium DNS Server";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+      wants = [ "network-online.target" ];
+
+      # Generate a password hash if adminPasswordFile is provided.
+      # The server is stopped on first run if no password hash exists,
+      # so we pre-seed the config with the hashed password.
+      preStart = ''
+        if [ -f "${cfg.configDir}/config.json" ]; then
+          # Config already exists, do not overwrite
+          true
+        else
+          install -m 0640 ${configFile} ${cfg.configDir}/config.json
+          ${lib.optionalString (cfg.adminPasswordFile != null) ''
+            if [ -f "${cfg.adminPasswordFile}" ]; then
+              # .NET-compatible SHA256 hash of the password
+              PASSWORD=$(cat "${cfg.adminPasswordFile}" | tr -d '\n')
+              HASH=$(echo -n "$PASSWORD" | ${pkgs.openssl}/bin/openssl dgst -sha256 -hex | cut -d' ' -f2)
+              ${pkgs.jq}/bin/jq \
+                ".AdminPassword = \"$HASH\" | .Pbkdf2Iterations = 600000" \
+                ${cfg.configDir}/config.json > ${cfg.configDir}/config.json.tmp
+              mv ${cfg.configDir}/config.json.tmp ${cfg.configDir}/config.json
+            fi
+          ''}
+        fi
+      '';
+
+      serviceConfig = {
+        Type = "simple";
+        ExecStart = "${dnsPkg}/bin/technitium-dns-server ${cfg.configDir}";
+        User = "dns";
+        Group = "dns";
+        Restart = "on-failure";
+        RestartSec = "5s";
+        LimitNOFILE = 1048576;
+        # Protect the system
+        ProtectSystem = "full";
+        ProtectHome = true;
+        PrivateTmp = true;
+        NoNewPrivileges = true;
+        ReadWritePaths = [ cfg.configDir ];
+      };
+    };
+
+    # Create the dns system user and group
+    users.users.dns = {
+      description = "Technitium DNS Server daemon user";
+      group = "dns";
+      isSystemUser = true;
+      home = cfg.configDir;
+      createHome = true;
+    };
+
+    users.groups.dns = { };
+
+    # Open firewall ports for DNS (UDP/TCP 53) and optionally the web interface
+    networking.firewall = lib.mkMerge [
+      {
+        allowedTCPPorts = [ cfg.dnsPort ];
+        allowedUDPPorts = [ cfg.dnsPort ];
+      }
+      # Allow web admin access only if listenAddresses restricts it to localhost
+      (lib.mkIf (cfg.listenAddresses == [ ] || builtins.elem "127.0.0.1" cfg.listenAddresses) {
+        allowedTCPPorts = [ cfg.webPort ];
+      })
+    ];
+
+    # Ensure DNS resolution is available locally before starting
+    networking.nameservers = lib.mkAfter [ "127.0.0.1" ];
+  };
+}