[Bug 1780332] Re: vaultlocker does not ensure that udev is triggered to create /dev/disk/by-uuid/<uuid-in-luks-header> symlink and fails

[Dimitri John Ledkov]

I'm not sure what vaultlocker is.

trigger might be appropriate together with a '--settle' flag, if/where
available.

instead of manually opening things, i'd expect crypttab to be adjusted
with `systemctl daemon-reload` re-run to regenerated systemd-cryptsetup@
units and "open" the encrytped device using systemd-cryptsetup@ instance
unit.... However that might be "too" systemd specific for vaultcrypt
upstream...

If one injects uuid onto a drive, it might not generate any kernel udev
events for udevd to react to and create/update symlinks.

It would be nice to have an interleaved log of udev events from udevadm
monitor, to see if there are any events emitted after "format" action is
done. If there are none, then vaultlocker needs to be fixed to trigger
things.

** Also affects: systemd (Ubuntu)
   Importance: Undecided
       Status: New

** Changed in: cryptsetup (Ubuntu)
       Status: New => Incomplete

** Changed in: systemd (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1780332

Title:
  vaultlocker does not ensure that udev is triggered to create /dev/disk
  /by-uuid/<uuid-in-luks-header> symlink and fails

Status in vaultlocker:
  Fix Released
Status in cryptsetup package in Ubuntu:
  Incomplete
Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  When an encrypted device is setup up a UUID (osd_fsid) is passed from
  the charm to be used in the cryptsetup command which accepts a UUID to
  place into the LUKS header (shown in cryptsetup luksDump <path-to-
  block-device>).

  https://github.com/openstack/charm-ceph-osd/blob/stable/18.05/lib/ceph/utils.py#L1788-L1804 
  UUID comes from osd_fsid

  https://github.com/openstack-charmers/vaultlocker/blob/8c9cb85dc3ed5dbf18c66a810d189a5230d85c34/vaultlocker/shell.py#L69-L80
  # else statement is used here
       block_uuid = str(uuid.uuid4()) if not args.uuid else args.uuid

       dmcrypt.luks_format(key, block_device, block_uuid) # creates a LUKS header
  # ...
       dmcrypt.luks_open(key, block_uuid) # sets up a device with device mapper decrypting it via dmcrypt

  https://github.com/openstack-
  charmers/vaultlocker/blob/d813233179bdf2eec8ed101c702a8e552a966f44/vaultlocker/dmcrypt.py#L44-L56

  This UUID is visible in blkid output

  /dev/sdc: UUID="<luks-header-uuid>" TYPE="crypto_LUKS"

  and a udev rule exists to create a /dev/disk/by-uuid/<luks-header-
  uuid> symlink (which is normally used for filesystem -> block device
  resolution)

  https://git.launchpad.net/~usd-import-team/ubuntu/+source/lvm2/tree/udev/13-dm-disk.rules.in#n25
  ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"

  
  Where vaultlocker fails is in luks_open command (right after luks_format) 

   # cryptsetup --batch-mode --key-file - open UUID=<luks-header-uuid>
  crypt-<luks-header-uuid> --type luks

  because it tries to access /dev/disk/by-uuid/<luks-header-uuid> which
  does not exist.

  This happens since udev rules are not re-triggered to create this
  symlink after a LUKS device is created.

  Solution: call the command below after luks_format before luks_open

  udevadm settle --exit-if-exists=/dev/disk/by-uuid/<luks-header-uuid-
  equal-to-osd-fsid>

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