12.04.4 alternate installer encryption should default to aes-xts-plain64

[Marc Deslauriers]

[Impact]

 * Default LUKS encryption settings in the installer are proven to be susceptible to a malleability attack (targeted manipulation of encrypted data).
 * Thus it is proposed to bump defaults to aes-xts-plain64 which is believe to not be affected by above attack.

[Test Case]

 * Perform LUKS encrypted installation using d-i (text) based interface
 * After installation verity that XTS has been used, and not CBC.

# cryptsetup luksDump /dev/sda5|grep Cipher

Here is the sample of _bad_ (CBC) output:

Cipher name: aes
Cipher mode: cbc-essiv:sha256

Here is the sample of _good_ (XTS) output:

Cipher name: aes
Cipher mode: xts-plain64

[Other Info]

12.04 LUKS encryption in the installer defaulted to CBC. We should switch 12.04.4 to aes-xts-plain64 as in 12.10 and above.

See:
http://www.jakoblell.com/blog/2013/12/22/practical-malleability-attack-against-cbc-encrypted-luks-partitions/

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Colin Watson (cjwatson)]

Hello Marc, or anyone else affected,

Accepted partman-crypto into precise-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/partman-crypto/50ubuntu2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Dimitri John Ledkov (xnox)]

Verified using server image, xts-plain64 was used and the machine booted / mounted encrypted root correctly.

[Launchpad Janitor (janitor)]

This bug was fixed in the package partman-crypto - 50ubuntu2

---------------
partman-crypto (50ubuntu2) precise; urgency=medium

  * Backport support for, and use by default, xts-plain64. (LP: #1263740) (closes: #482092)
    - Double key size if xts mode is selected.
 -- Dimitri John Ledkov <email address hidden> Wed, 22 Jan 2014 12:25:11 +0000

[Colin Watson (cjwatson)]

The verification of the Stable Release Update for partman-crypto has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regresssions.