[Bug 1842417] Re: Ubiquity needs support for fscrypt

[Redsandro]

> I think some problem has to be considered: as far as I understood, the folder /.fscrypt shall not be deleted (risk to loose access to your data?)
> if yes, it's a bit risky in case you re-install system on / with a separated encrypted /home that you want to keep.

When you set up your encrypted home using the fscrypt tool and it
detects that /home is not the same as /, it will offer to create a
recovery protector. This creates a file in your home called fscrypt-
recovery-passphrase.txt (or something like that) that needs to be
written down (similar to ecryptfs). This protector is stored on
/home/.fscrypt.

This means you can unlock the directory on a different (or new) system,
and once unlocked, you can create a new login protector.

I assume ubiquity can be scripted to detect a pre-existing user home was
encrypted using fscrypt, query for the recovery protector passphrase,
unlock the directory, and add add a login protector.

> I also would like to add an other issue of full disk encryption: it
need to enter password at boot on the machine.

I hadn't even thought about that because I never use full disk
encryption. Some will argue that this is the point as it is more secure,
but I would argue that you should have the choice to use your computer
in a more versatile manner while still being able to protect your
personal files from raw disk reading with a bootable usb stick. Options
could be presented:

Encryption options:

* Full Disk Encryption - (Recommended) Best security. Suitable for single user hardware.
* Home Encryption - Good security. Suitable for shared family computers and WoL.
* No Encryption - No security. Good for guests and internet cafes.

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https://bugs.launchpad.net/bugs/1842417

Title:
  Ubiquity needs support for fscrypt

Status in ubiquity package in Ubuntu:
  Confirmed

Bug description:
  Home encryption using ecryptfs was removed in Ubuntu 18.04 for
  reasons. Full disk encryption was recommended as an alternative, and
  set as the one-size-fits-all solution in ubiquity.

  Not everyone agrees that encrypting the entire disk is the best
  alternative. Some prefer a more lightweight solution. Others have
  families and like to share a laptop, perhaps even with an unprivileged
  password-less guest account, and family members want to encrypt their
  home with a personal password.

  Can we re-introduce (an option to choose) home encryption using
  fscrypt? Not only was this suggested (prematurely) by the Ubuntu 18.04
  release notes, it's also feature-complete now with v2 kernel
  encryption policy patches merged in kernel 5.4, which is the default
  kernel on Ubuntu 20.04 LTS.

  
  Setup
  -----

  Steps that would need to be scripted in ubiquity are as simple as:

  ```
  apt install fscrypt libpam-fscrypt
  fscrypt setup
  fscrypt setup /
  fscrypt setup /home ## only if home is on a separate partition
  fscrypt encrypt /home/$USERNAME
  ```

  For the rest you can probably re-use the ubiquity widgets and
  detection code from the ecryptfs days.

  Keep in mind that the fscrypt packages on the Ubuntu repositories are
  outdated. See:
  https://bugs.launchpad.net/ubuntu/+source/fscrypt/+bug/1882993

  
  Resources
  ---------

  Fscrypt ext4 native encryption documented on Kernel.org
  https://www.kernel.org/doc/html/v5.4/filesystems/fscrypt.html

  Build instructions
  https://github.com/ebiggers/fscrypt#fscrypt-

  Fscrypt on Arch Linux
  https://wiki.archlinux.org/index.php/Fscrypt

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