Let's track the "dirty" state of a home directory backed by a LUKS
volume by setting a new xattr "home.home-dirty" on the backing file
whenever it is in use.
This allows us to later user this information to show a home directory
as "dirty". This is useful because we trim/allocate on log-out, and
if we don't do that a home directory will be larger than necessary. This
fact is something we should communicate to the admin.
The idea is that when an admin sees a user with a "dirty" home directory
they can ask them to log in, to clean up the dirty state, and thus trim
everything again.
The cryptsetup context pins the loop device even after deactivation.
Let's explicitly release the context to make sure the subsequent
loopback device detaching works cleanly.
This how this works on Linux: when atomically creating a file we need to
fully populate it under a temporary name and then when we are fully
done, sync it and the directory it is contained in, before renaming it
to the final name.
homed maintains two or three copies of the user's identity record per
home directory: one on the host, one inside the LUKS header, and one
embedded in the home directory.
Previously we'd insist that if a user logs in they have to authenticate
against all three, as a safety feature. This broke logging into
unfixated records however, since in that case the host version is
synthetic and thus does not carry any authentication data.
Let's hence losen the strictness here: accept authentication against
host records that carry no auth data. This should be safe as we know
after all that the second/third record will catch invalid accesses.
Fixes: #15178
When managing a home directory as LUKS image we currently place a
directory at the top that contains the actual home directory (so that
the home directory of the user won't be cluttered by lost-found and
suchlike). On btrfs let's make that a subvol though. This is a good idea
so that possibly later on we can make use of this for automatic history
management.
Fixes: #15121
Lennart Poettering