[Bug 1263740] Re: 12.04.4 alternate installer encryption should default to aes-xts-plain64

[Colin Watson]

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!

** Changed in: partman-crypto (Ubuntu Precise)
       Status: In Progress => Fix Committed

** Tags added: verification-needed

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https://bugs.launchpad.net/bugs/1263740

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

Status in “partman-crypto” package in Ubuntu:
  Fix Released
Status in “partman-crypto” source package in Precise:
  Fix Committed
Status in “partman-crypto” package in Debian:
  Fix Released

Bug description:
  [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/

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