nixos: initrd/luks: simplify Yubikey handling code

From reading the source I'm pretty sure it doesn't support multiple Yubikeys, hence
those options are useless.

Also, I'm pretty sure nobody actually uses this feature, because enabling it causes
extra utils' checks to fail (even before applying any patches of this branch).

As I don't have the hardware to test this, I'm too lazy to fix the utils, but
I did test that with extra utils checks commented out and Yubikey
enabled the resulting script still passes the syntax check.

1 files changed, 16 insertions, 36 deletions

diff --git a/nixos/modules/system/boot/luksroot.nix b/nixos/modules/system/boot/luksroot.nix
index ea6d189d9907..5f42c76d5d7f 100644
--- a/nixos/modules/system/boot/luksroot.nix
+++ b/nixos/modules/system/boot/luksroot.nix
@@ -75,9 +75,13 @@ let
     # Warning: Do NOT replace with tmpfs!
     mkdir -p /crypt-ramfs
     mount -t ramfs none /crypt-ramfs
+
+    # For Yubikey salt storage
+    mkdir -p /crypt-storage
   '';
 
   postCommands = ''
+    umount /crypt-storage 2>/dev/null
     umount /crypt-ramfs 2>/dev/null
   '';
 
@@ -184,11 +188,11 @@ let
         local new_response
         local new_k_luks
 
-        mkdir -p ${yubikey.storage.mountPoint}
-        mount -t ${yubikey.storage.fsType} ${toString yubikey.storage.device} ${yubikey.storage.mountPoint}
+        mount -t ${yubikey.storage.fsType} ${yubikey.storage.device} /crypt-storage || \
+          die "Failed to mount Yubikey salt storage device"
 
-        salt="$(cat ${yubikey.storage.mountPoint}${yubikey.storage.path} | sed -n 1p | tr -d '\n')"
-        iterations="$(cat ${yubikey.storage.mountPoint}${yubikey.storage.path} | sed -n 2p | tr -d '\n')"
+        salt="$(cat /crypt-storage${yubikey.storage.path} | sed -n 1p | tr -d '\n')"
+        iterations="$(cat /crypt-storage${yubikey.storage.path} | sed -n 2p | tr -d '\n')"
         challenge="$(echo -n $salt | openssl-wrap dgst -binary -sha512 | rbtohex)"
         response="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"
 
@@ -216,10 +220,7 @@ let
             fi
         done
 
-        if [ "$opened" == false ]; then
-            umount ${yubikey.storage.mountPoint}
-            die "Maximum authentication errors reached"
-        fi
+        [ "$opened" == false ] && die "Maximum authentication errors reached"
 
         echo -n "Gathering entropy for new salt (please enter random keys to generate entropy if this blocks for long)..."
         for i in $(seq ${toString yubikey.saltLength}); do
@@ -244,26 +245,17 @@ let
             new_k_luks="$(echo | pbkdf2-sha512 ${toString yubikey.keyLength} $new_iterations $new_response | rbtohex)"
         fi
 
-        mkdir -p ${yubikey.ramfsMountPoint}
-        # A ramfs is used here to ensure that the file used to update
-        # the key slot with cryptsetup will never get swapped out.
-        # Warning: Do NOT replace with tmpfs!
-        mount -t ramfs none ${yubikey.ramfsMountPoint}
-
-        echo -n "$new_k_luks" | hextorb > ${yubikey.ramfsMountPoint}/new_key
-        echo -n "$k_luks" | hextorb | ${cschange} --key-file=- ${yubikey.ramfsMountPoint}/new_key
+        echo -n "$new_k_luks" | hextorb > /crypt-ramfs/new_key
+        echo -n "$k_luks" | hextorb | ${cschange} --key-file=- /crypt-ramfs/new_key
 
         if [ $? == 0 ]; then
-            echo -ne "$new_salt\n$new_iterations" > ${yubikey.storage.mountPoint}${yubikey.storage.path}
+            echo -ne "$new_salt\n$new_iterations" > /crypt-storage${yubikey.storage.path}
         else
             echo "Warning: Could not update LUKS key, current challenge persists!"
         fi
 
-        rm -f ${yubikey.ramfsMountPoint}/new_key
-        umount ${yubikey.ramfsMountPoint}
-        rm -rf ${yubikey.ramfsMountPoint}
-
-        umount ${yubikey.storage.mountPoint}
+        rm -f /crypt-ramfs/new_key
+        umount /crypt-storage
     }
 
     open_yubikey() {
@@ -506,12 +498,6 @@ in
                   description = "Time in seconds to wait for the Yubikey.";
                 };
 
-                ramfsMountPoint = mkOption {
-                  default = "/crypt-ramfs";
-                  type = types.str;
-                  description = "Path where the ramfs used to update the LUKS key will be mounted during early boot.";
-                };
-
                 /* TODO: Add to the documentation of the current module:
 
                    Options related to the storing the salt.
@@ -532,12 +518,6 @@ in
                     description = "The filesystem of the unencrypted device.";
                   };
 
-                  mountPoint = mkOption {
-                    default = "/crypt-storage";
-                    type = types.str;
-                    description = "Path where the unencrypted device will be mounted during early boot.";
-                  };
-
                   path = mkOption {
                     default = "/crypt-storage/default";
                     type = types.str;
@@ -550,8 +530,8 @@ in
               };
             });
           };
-
-        }; }));
+        };
+      }));
     };
 
     boot.initrd.luks.yubikeySupport = mkOption {