ceph/doc/ceph-volume/lvm/encryption.rst

   1 .. _ceph-volume-lvm-encryption:
   2
   3 Encryption
   4 ==========
   5
   6 Logical volumes can be encrypted using ``dmcrypt``. Encryption can be done in
   7 different ways, specially with LVM. ``ceph-volume`` is somewhat opinionated
   8 with the way it sets up encryption with logical volumes so that the process is
   9 consistent and robust.
  10
  11 In this case, ``ceph-volume lvm`` follows these constraints:
  12
  13 * only LUKS (version 1) is used
  14 * Logical Volumes are encrypted, while their underlying PVs (physical volumes)
  15   aren't
  16 * Non-LVM devices like partitions are also encrypted with the same OSD key
  17
  18
  19 LUKS
  20 ----
  21 There are currently two versions of LUKS, 1 and 2. Version 2 is a bit easier
  22 to implement but not widely available in all distros Ceph supports. LUKS 1 is
  23 not going to be deprecated in favor of LUKS 2, so in order to have as wide
  24 support as possible, ``ceph-volume`` uses LUKS version 1.
  25
  26 .. note:: Version 1 of LUKS is just referenced as "LUKS" whereas version 2 is
  27           referred to as LUKS2
  28
  29
  30 LUKS on LVM
  31 -----------
  32 Encryption is done on top of existing logical volumes (unlike encrypting the
  33 physical device). Any single logical volume can be encrypted while other
  34 volumes can remain unencrypted. This method also allows for flexible logical
  35 volume setups, since encryption will happen once the LV is created.
  36
  37
  38 Workflow
  39 --------
  40 When setting up the OSD, a secret key will be created, that will be passed
  41 along to the monitor in JSON format as stdin to prevent the key from being
  42 captured in the logs.
  43
  44 The JSON payload looks something like::
  45
  46         {
  47             "cephx_secret": CEPHX_SECRET,
  48             "dmcrypt_key": DMCRYPT_KEY,
  49             "cephx_lockbox_secret": LOCKBOX_SECRET,
  50         }
  51
  52 The naming convention for the keys is **strict**, and they are named like that
  53 for the hardcoded (legacy) names ceph-disk used.
  54
  55 * ``cephx_secret`` : The cephx key used to authenticate
  56 * ``dmcrypt_key`` : The secret (or private) key to unlock encrypted devices
  57 * ``cephx_lockbox_secret`` : The authentication key used to retrieve the
  58   ``dmcrypt_key``. It is named *lockbox* because ceph-disk used to have an
  59   unencrypted partition named after it, used to store public keys and other
  60   OSD metadata.
  61
  62 The naming convention is strict because Monitors supported the naming
  63 convention by ceph-disk, which used these key names. In order to keep
  64 compatibility and prevent ceph-disk from breaking, ceph-volume will use the same
  65 naming convention *although they don't make sense for the new encryption
  66 workflow*.
  67
  68 After the common steps of setting up the OSD during the prepare stage, either
  69 with :term:`filestore` or :term:`bluestore`, the logical volume is left ready
  70 to be activated, regardless of the state of the device (encrypted or decrypted).
  71
  72 At activation time, the logical volume will get decrypted and the OSD started
  73 once the process completes correctly.
  74
  75 Summary of the encryption workflow for creating a new OSD:
  76
  77 #. OSD is created, both lockbox and dmcrypt keys are created, and sent along
  78    with JSON to the monitors, indicating an encrypted OSD.
  79
  80 #. All complementary devices (like journal, db, or wal) get created and
  81    encrypted with the same OSD key. Key is stored in the LVM metadata of the
  82    OSD
  83
  84 #. Activation continues by ensuring devices are mounted, retrieving the dmcrypt
  85    secret key from the monitors and decrypting before the OSD gets started.