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qidle

qidled is an idle daemon for Qubes OS.

It can detect the user or VMs going idle and accordingly trigger user-defined actions (usually a VM shutdown).

Besides the obvious energy savings it is mostly intended to harden a Qubes OS host against memory side-channel and other attacks originating from compromised VMs.

The basic idea is:
Halted attacker VMs cannot attack and halted target VMs are harder to attack. So let's make an attacker's life harder by halting everything we don't need!

Features

  • not interruptable by (potentially malicious) VMs as it runs in dom0
  • works with all Qubes OS VMs
  • no input from VMs
  • highly customizable (timeouts per VM, actions, enable/disable per VM, ...)

Why another?

The official Qubes OS solution runs inside the respective VM which it is meant to monitor and halt as needed.

However if that VM is compromised, it can easily avoid its shutdown by e.g. re-writing the shutdown script. Afterwards it may use the time gained to deploy e.g. a memory side channel attack against other running VMs - all of this while the user is probably idle.

Moreover it only works on Fedora and Debian VMs and doesn't provide enough flexibility for my use cases.

Therefore I decided to write this script.

Installation

  1. Download blib, copy it to dom0 and install it according to its instructions.
  2. Download this repository with git clone https://github.com/3hhh/qidle.git or your browser and copy it to dom0.
  3. Move the repository to a directory of your liking.
  4. Symlink the qidled binary into your dom0 PATH for convenience, e.g. to /usr/bin/.
  5. Configure qidled at /etc/qidled.conf. A sample configuration is included in your repository copy. Copy that one to /etc/qidled.conf for a start.
  6. (Optional) Configure Qubes OS so that qidled start is run on autostart by the X server user.

A word of caution

It is recommended to apply standard operational security practices during installation such as:

  • Github SSL certificate checks
  • Check the GPG commit signatures using git log --pretty="format:%h %G? %GK %aN %s". All of them should be good (G) signatures coming from the same key (1533 C122 5C1B 41AF C46B 33EB) EB03 A691 DB2F 0833 (assuming you trust that key).
  • Code review

You're installing something to dom0 after all.

Usage

Execute qidled on the command-line to obtain an overview of its capabilities.

The sample configuration is a full-fledged bash file with lots of comments and should thus be mostly self-explanatory. Feel free to directly program your custom stuff inside your own configuration file.
Happy hacking! :-)

Uninstall

  1. Remove all symlinks and autostart references that you created during the installation.
  2. Remove the repository clone from dom0.
  3. Uninstall blib according to its instructions.

Copyright

© 2020 David Hobach GPLv3

See LICENSE for details.