Re: [gentoo-user] KDE, sddm etc security. Plus LVM question.

[Rich Freeman]

On Sun, Mar 20, 2022 at 12:05 PM Daniel Frey <djqfrey@×××××.com> wrote:
>
> They don't even need to defeat a password. If they have root, it's
> trivial to unlock a locked session without knowing the password - just FYI.
> ...
> The screen locks in linux are security by obscurity, if something is
> that sensitive, don't stay logged in all the time.

If somebody has root access to your box, then they are going to be
able to get at your data.  They don't have to unlock your session to
do it - they have access to the memory of all your processes,
everything on disk, and so on.  If you're using encryption at the
account level and it is well-implemented then root probably can't get
at your data while you aren't logged in, but they certainly can get it
the next time you log in.

It is true though that linux screensavers are often not
well-implemented.  Honestly, I'm not sure if any of them are - it
seems to be more of an afterthought in the design layered on top.  I
haven't made a study of them, so maybe there are some which are, but
something like this really needs to be designed into the system to be
secure, and some of that needs to be treated as security-critical
code.

Now, if you want to make an argument for leaving systems powered down
except when needed if they contain sensitive data that would certainly
reduce the opportunity for intrusion, but you still need the OS to
keep people from gaining root in the first place.

As others have mentioned at the start of the thread, if you're
concerned with physical security then full disk encryption (or at
least encryption of data combined with airtight authentication of the
OS) has to be part of the solution.  In 99% of linux-based solutions
that requires entering a password at boot.  In theory the linux kernel
has support for TPM verified boot, so you could implement something
like Bitlocker/etc on Linux, but I'm not aware of any distros that
have done so (unless you want to count something like ChromeOS).  For
a desktop system a boot password isn't as much of a problem, but if
you want an unattended server to be able to boot on power restoration
then a TPM-based solution would be better.  It certainly is prettier
on the desktop, and allows for more recovery options, which is why
just about all corporate laptops I've seen do it this way.  Of course
without a boot password you're only as secure as your OS, as any
attacker can still boot the OS and attack it while it is running,
which they can't do if the disk requires a password to decrypt it.

If you're running Windows on a system with a TPM the simplest solution
to all this stuff is to turn on Bitlocker, though this is not
available on the Home edition of Win10.

-- 
Rich