nixos/…/swap.nix: don't create a LUKS header for randomEncryption

Creating and then erasing the key relies on the disk erasing data
correctly, and otherwise allows attackers to simply decrypt swap just
using "secretkey". We don't actually need a LUKS header, so we can save
ourselves some pointless disk writes and identifiability.

In addition, I wouldn't have made the awful mistake of backing up my swap partition's LUKS header instead of my zpool's. May my data rest in peace.

1 files changed, 1 insertions, 3 deletions

diff --git a/nixos/modules/config/swap.nix b/nixos/modules/config/swap.nix
index e57ed2565a10..5d47b09ded99 100644
--- a/nixos/modules/config/swap.nix
+++ b/nixos/modules/config/swap.nix
@@ -149,9 +149,7 @@ in
                   fi
                 ''}
                 ${optionalString sw.randomEncryption ''
-                  echo "secretkey" | cryptsetup luksFormat --batch-mode ${sw.device}
-                  echo "secretkey" | cryptsetup luksOpen ${sw.device} ${sw.deviceName}
-                  cryptsetup luksErase --batch-mode ${sw.device}
+                  cryptsetup open ${sw.device} ${sw.deviceName} --type plain --key-file /dev/urandom
                   mkswap ${sw.realDevice}
                 ''}
               '';