nixos/ecryptfs: init

Currently, ecryptfs support is coupled to `security.pam.enableEcryptfs`, but one
might want to use ecryptfs without enabling the PAM functionality. This commit
splits it out into a `boot.supportedFilesystems` switch.

nixos/modules/module-list.nix

···
   ./tasks/filesystems/bcachefs.nix
   ./tasks/filesystems/btrfs.nix
   ./tasks/filesystems/cifs.nix
+  ./tasks/filesystems/ecryptfs.nix
   ./tasks/filesystems/exfat.nix
   ./tasks/filesystems/ext.nix
   ./tasks/filesystems/f2fs.nix

nixos/modules/security/pam.nix

···
       ++ optionals config.krb5.enable [pam_krb5 pam_ccreds]
       ++ optionals config.security.pam.enableOTPW [ pkgs.otpw ]
       ++ optionals config.security.pam.oath.enable [ pkgs.oathToolkit ]
-      ++ optionals config.security.pam.enableU2F [ pkgs.pam_u2f ]
-      ++ optionals config.security.pam.enableEcryptfs [ pkgs.ecryptfs ];
+      ++ optionals config.security.pam.enableU2F [ pkgs.pam_u2f ];
+
+    boot.supportedFilesystems = optionals config.security.pam.enableEcryptfs [ "ecryptfs" ];
 
     security.wrappers = {
       unix_chkpwd = {
···
         owner = "root";
         setuid = true;
       };
-    } // (if config.security.pam.enableEcryptfs then {
-      "mount.ecryptfs_private".source = "${pkgs.ecryptfs.out}/bin/mount.ecryptfs_private";
-       "umount.ecryptfs_private".source = "${pkgs.ecryptfs.out}/bin/umount.ecryptfs_private";
-    } else {});
+    };
 
     environment.etc =
       mapAttrsToList (n: v: makePAMService v) config.security.pam.services;

nixos/modules/tasks/filesystems/ecryptfs.nix

···
+{ config, lib, pkgs, ... }:
+# TODO: make ecryptfs work in initramfs?
+
+with lib;
+
+{
+  config = mkIf (any (fs: fs == "ecryptfs") config.boot.supportedFilesystems) {
+    system.fsPackages = [ pkgs.ecryptfs ];
+    security.wrappers = {
+      "mount.ecryptfs_private".source = "${pkgs.ecryptfs.out}/bin/mount.ecryptfs_private";
+      "umount.ecryptfs_private".source = "${pkgs.ecryptfs.out}/bin/umount.ecryptfs_private";
+    };
+  };
+}