Comment 2 for bug 1818165

This isn't a total disaster; you can get the master key from dmsetup table --showkeys while the mapping still exists, and cryptsetup luksAddKey has a --master-key-file parameter you can use to add a known passphrase for adding to vault. (I
m not sure if --master-key-file wants hex-encoded data, as printed by dmsetup, or binary.)