EncryptedHomeDirectory

Revision 5 as of 2008-12-03 00:48:12

Clear message

Summary

Based on the delivery of EncryptedPrivateDirectory in Ubuntu Intrepid, this specification describes the next steps to extend that work to provide a seamless mechanism for encrypting a user's entire home directory, mounting it on login, and un-mounting it on the last logout.

Release Note

The Ubuntu Jaunty Jackalope (9.04) release will enable per-user home directory encryption, automatically mounting it on login, and un-mounting it on the last logout of the user.

Rationale

The EncryptedPrivateDirectory work proved the usefulness and stability of the Linux kernel's ecryptfs cryptographic filesystem. Encrypting only ~/Private directory, however, requires Ubuntu users to consciously store sensitive data in that location, and manually linking that data to traditionally locations.

Use Cases

See the use cases for:

Encrypted home directories will provide a more complete solution to encrypting all of the user's unique data, while not requiring the performance penalty of encrypting all of the data on the entire system and not requiring a passphrase to boot an unattended system.

Assumptions

Users of encrypted home directories are willing to pay the minor performance penalty incurred by encrypting/decrypting their data in the home directory in exchange for data security on the disk.

  • We should get some formal filesystem benchmarks against an encrypted home directory.

Users will record their mount passphrase in a safe location, such that they can retrieve their data manually if necessary.

  • We need to state this clearly on user creation, and provide a graphical utility for retrieving said mount passphrase and allowing the user to print/record it.

Swap space will be encrypted.

Design

The eCryptfs Linux kernel cryptographic filesystem was chosen as the implementation mechanism for several reasons:

  1. This is the same technology developed and proven in the Intrepid release in the EncryptedPrivateDirectory specification.

  2. The underlying cryptographic data is encrypted on a per-file basis, and as such, it is possible to incrementally sync changes to the encrypted data to remote backup systems.
  3. Since it is an overlay virtual filesystem, no predetermined disk allocation is necessary for the encrypted mountpoint. Rather, the same amount of available disk space available to a normal home directory is available to the encrypted home directory.

Implementation

UI Changes

Should cover changes required to the UI, or specific UI that is required to implement this

Code Changes

Code changes should include an overview of what needs to change, and in some cases even the specific details.

Migration

Include:

  • data migration, if any
  • redirects from old URLs to new ones, if any
  • how users will be pointed to the new way of doing things, if necessary.

Test/Demo Plan

As of 2008-12-02, you can test this by:

  1. Install the adduser and ecryptfs-utils packages in the following PPA:

  2. Add a user with an encrypted home directory as root, with:
    •  # adduser --encrypt-home testuser 

  3. Login as testuser on the console, through the GUI, and via ssh. Ensure that all programs work as expected. Log out of the console/GUI/ssh. Ensure that the home directory is not mounted and that the data stored in /home/testuser/.Private is encrypted.

Unresolved issues

There are two other specifications, solving related issues:

Discussion

Please post questions to:


CategorySpec