[dm-crypt] [ANNOUNCE] cryptsetup 1.5.0

Milan Broz gmazyland at gmail.com
Tue Jul 10 20:56:12 CEST 2012

Hash: SHA1

The stable cryptsetup 1.5.0 release is available at


Feedback and bug reports are welcomed.

Cryptsetup 1.5.0 Release Notes

This release covers mainly inclusion of:

  * Veritysetup tool (and related libcryptsetup extensions for dm-verity).

  * Experimental cryptsetup-reencrypt tool (LUKS offline reencryption).

Changes since version 1.5.0-rc2
  * Add --device-size option for reencryption tool.
  * Switch to use unit suffix for --reduce-device-size option.
  * Remove open device debugging feature (no longer needed).
  * Fix library name for FIPS check.
  * Add example of using reencryption inside dracut (see misc/dracut).

Changes since version 1.5.0-rc1
Introduce cryptsetup-reencrypt - experimental offline LUKS reencryption tool.

! cryptsetup-reencrypt tool is EXPERIMENTAL

This tool tries to simplify situation when you need to re-encrypt the whole
LUKS device in situ (without need to move data elsewhere).

This can happen for example when you want to change volume (master) key,
encryption algorithm, or other encryption parameter.

Cryptsetup-reencrypt can even optionally shift data on device
(reducing data device size - you need some free space at the end of device).

In general, cryptsetup-reencrypt can be used to

 - re-generate volume key
 - change arbitrary encryption parameters
 - add encryption to not yet encrypted drive

Side effect of reencryption is that final device will contain
only ciphertext (for all sectors) so even if device was not properly
wiped by random data, after reencryption you cannot distinguish
which sectors are used.
(Reecryption is done always for the whole device.)

There are for sure bugs, please TEST IT IN TEST ENVIRONMENT before
use for your data.

This tool is not resistant to HW and kernel failures - hw crash
will cause serious data corruption.

You can enable compilation of this tool with --enable-cryptsetup-reencrypt
configure option (it is switched off by default).
(Tool requires libcryptsetup 1.4.3 and later.)

You have to provide all keyslot passphrases or use --keyslot-option
(then all other keyslots will be disabled).

EXAMPLES (from man page)

Reencrypt /dev/sdb1 (change volume key)
   # cryptsetup-reencrypt /dev/sdb1

Reencrypt and also change cipher and cipher mode
  # cryptsetup-reencrypt /dev/sdb1 -c aes-xts-plain64

  Note: if you are changing key size, there must be enough space
  for keyslots in header or you have to use --reduce-device size and
  reduce fs in advance.

Add LUKS encryption to not yet encrypted device
  First, be sure you have space added to disk.
  Or, alternatively, shrink filesystem in advance.

  Here we need 4096 512-bytes sectors (enough for 2x128 bit key).

  # fdisk -u /dev/sdb # move sdb1 partition end + 4096 sectors

  # cryptsetup-reencrypt /dev/sdb1 --new --reduce-device-size 4096

There are some options which can improve performance (depends on system),
namely --use-directio (use direct IO for all operations) can be faster
on some systems. See man page.

Progress and estimated time is printed during reencryption.

You can suspend reencryption (using ctrl+c or term signal).
To continue reencryption you have to provide only
the device parameter (offset is stored in temporary log file).

Please note LUKS device is marked invalid during reencryption and
you have to retain tool temporary files until reencryption finishes.

Temporary files are LUKS-<uuid>.[log|org|new]

Other changes
  * Fix luks-header-from-active script (do not use LUKS header on-disk, add UUID).
  * Add --test-passphrase option for luksOpen (check passphrase only).
  * Fix parsing of hexadecimal string (salt or root hash) in veritysetup.

Changes since version 1.4.3
Introduce veritysetup tool for dm-verity target management.

The dm-verity device-mapper target was added to Linux kernel 3.4 and
provides transparent integrity checking of block devices using a cryptographic
digest provided by the kernel crypto API. This target is read-only.

It is meant to be setup as part of a verified boot path (it was originally
developed by Chrome OS authors as part of verified boot infrastructure).

For deeper description please see http://code.google.com/p/cryptsetup/wiki/DMVerity
and kernel dm-verity documentation.

The libcryptsetup library was extended to support manipulation
with dm-verity kernel module and new veritysetup CLI tool is added.

There are no additional library requirements (it uses the same crypto
backend as cryptsetup).

If you want compile cryptsetup without veritysetup tool,
use --disable-veritysetup configure option.
For other configuration option see configure --help and veritysetup --help
(e.g. default parameters).

Supported libcryptsetup functions new CRYPT_VERITY type:
  crypt_set_data device
  crypt_activate_by_volume_key (volume key == root hash here)
and new introduced function

Please see comments in libcryptsetup.h and veritysetup.c as an code example
how to use CRYPT_VERITY API.

The veritysetup tool supports these operations:

  veritysetup format <data_device> <hash_device>
    Formats <hash_device> (calculates all hash areas according to <data_device>).
    This is initial command to prepare device <hash_device> for later verification.

  veritysetup create <name> <data_device> <hash_device> <root_hash>
    Creates (activates) a dm-verity mapping with <name> backed by device <data_device>
    and using <hash_device> for in-kernel verification.

  veritysetup verify <data_device> <hash_device> <root_hash>
    Verifies data in userspace (no kernel device is activated).

  veritysetup remove <name>
    Removes activated device from kernel (similar to dmsetup remove).

  veritysetup status <name>
    Reports status for the active kernel dm-verity device.

  veritysetup dump <hash_device>
    Reports parameters of verity device from on-disk stored superblock.

For more info see veritysetup --help and veritysetup man page.

Other changes
  * Both data and header device can now be a file and
    loop device is automatically allocated.

  * Require only up to last keyslot area for header device, previously
    backup (and activation) required device/file of size up to data start
    offset (data payload).

  * Fix header backup and restore to work on files with large data offset.
    Backup and restore now works even if backup file is smaller than data offset.

For full release notes with veritysetup examples see
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