nbd: add programs.nbd, services.nbd, and test

Changes:

nbd: Update nixos/modules/services/networking/nbd.nix

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nbd: Update nixos/modules/services/networking/nbd.nix

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nbd: Update nixos/tests/nbd.nix

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nbd: generalize options in nbd service

nbd: harden service

nbd: Update nixos/modules/services/networking/nbd.nix

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nbd: Update nixos/modules/services/networking/nbd.nix

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nbd: refactor code a bit and BindPaths automatically

3 files changed, 167 insertions, 0 deletions

diff --git a/nixos/modules/module-list.nix b/nixos/modules/module-list.nix
index f3570c3f123..442bcc39d59 100644
--- a/nixos/modules/module-list.nix
+++ b/nixos/modules/module-list.nix
@@ -179,6 +179,7 @@
   ./programs/msmtp.nix
   ./programs/mtr.nix
   ./programs/nano.nix
+  ./programs/nbd.nix
   ./programs/neovim.nix
   ./programs/nm-applet.nix
   ./programs/npm.nix
@@ -818,6 +819,7 @@
   ./services/networking/nar-serve.nix
   ./services/networking/nat.nix
   ./services/networking/nats.nix
+  ./services/networking/nbd.nix
   ./services/networking/ndppd.nix
   ./services/networking/nebula.nix
   ./services/networking/networkmanager.nix
diff --git a/nixos/modules/programs/nbd.nix b/nixos/modules/programs/nbd.nix
new file mode 100644
index 00000000000..fea9bc1ff71
--- /dev/null
+++ b/nixos/modules/programs/nbd.nix
@@ -0,0 +1,19 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.programs.nbd;
+in
+{
+  options = {
+    programs.nbd = {
+      enable = mkEnableOption "Network Block Device (nbd) support";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = with pkgs; [ nbd ];
+    boot.kernelModules = [ "nbd" ];
+  };
+}
diff --git a/nixos/modules/services/networking/nbd.nix b/nixos/modules/services/networking/nbd.nix
new file mode 100644
index 00000000000..87f8c41a8e5
--- /dev/null
+++ b/nixos/modules/services/networking/nbd.nix
@@ -0,0 +1,146 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.nbd;
+  configFormat = pkgs.formats.ini { };
+  iniFields = with types; attrsOf (oneOf [ bool int float str ]);
+  serverConfig = configFormat.generate "nbd-server-config"
+    ({
+      generic =
+        (cfg.server.extraOptions // {
+          user = "root";
+          group = "root";
+          port = cfg.server.listenPort;
+        } // (optionalAttrs (cfg.server.listenAddress != null) {
+          listenaddr = cfg.server.listenAddress;
+        }));
+    }
+    // (mapAttrs
+      (_: { path, allowAddresses, extraOptions }:
+        extraOptions // {
+          exportname = path;
+        } // (optionalAttrs (allowAddresses != null) {
+          authfile = pkgs.writeText "authfile" (concatStringsSep "\n" allowAddresses);
+        }))
+      cfg.server.exports)
+    );
+  splitLists =
+    partition
+      (path: hasPrefix "/dev/" path)
+      (mapAttrsToList (_: { path, ... }: path) cfg.server.exports);
+  allowedDevices = splitLists.right;
+  boundPaths = splitLists.wrong;
+in
+{
+  options = {
+    services.nbd = {
+      server = {
+        enable = mkEnableOption "the Network Block Device (nbd) server";
+
+        listenPort = mkOption {
+          type = types.port;
+          default = 10809;
+          description = "Port to listen on. The port is NOT automatically opened in the firewall.";
+        };
+
+        extraOptions = mkOption {
+          type = iniFields;
+          default = {
+            allowlist = false;
+          };
+          description = ''
+            Extra options for the server. See
+            <citerefentry><refentrytitle>nbd-server</refentrytitle>
+            <manvolnum>5</manvolnum></citerefentry>.
+          '';
+        };
+
+        exports = mkOption {
+          description = "Files or block devices to make available over the network.";
+          default = { };
+          type = with types; attrsOf
+            (submodule {
+              options = {
+                path = mkOption {
+                  type = str;
+                  description = "File or block device to export.";
+                  example = "/dev/sdb1";
+                };
+
+                allowAddresses = mkOption {
+                  type = nullOr (listOf str);
+                  default = null;
+                  example = [ "10.10.0.0/24" "127.0.0.1" ];
+                  description = "IPs and subnets that are authorized to connect for this device. If not specified, the server will allow all connections.";
+                };
+
+                extraOptions = mkOption {
+                  type = iniFields;
+                  default = {
+                    flush = true;
+                    fua = true;
+                  };
+                  description = ''
+                    Extra options for this export. See
+                    <citerefentry><refentrytitle>nbd-server</refentrytitle>
+                    <manvolnum>5</manvolnum></citerefentry>.
+                  '';
+                };
+              };
+            });
+        };
+
+        listenAddress = mkOption {
+          type = with types; nullOr str;
+          description = "Address to listen on. If not specified, the server will listen on all interfaces.";
+          default = null;
+          example = "10.10.0.1";
+        };
+      };
+    };
+  };
+
+  config = mkIf cfg.server.enable {
+    boot.kernelModules = [ "nbd" ];
+
+    systemd.services.nbd-server = {
+      after = [ "network-online.target" ];
+      before = [ "multi-user.target" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        ExecStart = "${pkgs.nbd}/bin/nbd-server -C ${serverConfig}";
+        Type = "forking";
+
+        DeviceAllow = map (path: "${path} rw") allowedDevices;
+        BindPaths = boundPaths;
+
+        CapabilityBoundingSet = "";
+        DevicePolicy = "closed";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        NoNewPrivileges = true;
+        PrivateDevices = false;
+        PrivateMounts = true;
+        PrivateTmp = true;
+        PrivateUsers = true;
+        ProcSubset = "pid";
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectProc = "noaccess";
+        ProtectSystem = "strict";
+        RestrictAddressFamilies = "AF_INET AF_INET6";
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        UMask = "0077";
+      };
+    };
+  };
+}