nixos/intel-sgx: add option for SGX provisioning

nixos/modules/hardware/cpu/intel-sgx.nix

@@ -0,0 +1,47 @@
+{ config, lib, ... }:
+with lib;
+let
+  cfg = config.hardware.cpu.intel.sgx.provision;
+  defaultGroup = "sgx_prv";
+in
+{
+  options.hardware.cpu.intel.sgx.provision = {
+    enable = mkEnableOption "access to the Intel SGX provisioning device";
+    user = mkOption {
+      description = "Owner to assign to the SGX provisioning device.";
+      type = types.str;
+      default = "root";
+    };
+    group = mkOption {
+      description = "Group to assign to the SGX provisioning device.";
+      type = types.str;
+      default = defaultGroup;
+    };
+    mode = mkOption {
+      description = "Mode to set for the SGX provisioning device.";
+      type = types.str;
+      default = "0660";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = hasAttr cfg.user config.users.users;
+        message = "Given user does not exist";
+      }
+      {
+        assertion = (cfg.group == defaultGroup) || (hasAttr cfg.group config.users.groups);
+        message = "Given group does not exist";
+      }
+    ];
+
+    users.groups = optionalAttrs (cfg.group == defaultGroup) {
+      "${cfg.group}" = { };
+    };
+
+    services.udev.extraRules = ''
+      SUBSYSTEM=="misc", KERNEL=="sgx_provision", OWNER="${cfg.user}", GROUP="${cfg.group}", MODE="${cfg.mode}"
+    '';
+  };
+}

nixos/modules/module-list.nix

@@ -45,6 +45,7 @@
   ./hardware/ckb-next.nix
   ./hardware/cpu/amd-microcode.nix
   ./hardware/cpu/intel-microcode.nix
+  ./hardware/cpu/intel-sgx.nix
   ./hardware/corectrl.nix
   ./hardware/digitalbitbox.nix
   ./hardware/device-tree.nix