qusal/salt/sys-print

sys-print

Printer environment in Qubes OS.

Table of Contents

• Description
• Security
• Installation
• Access Control
• Usage
  • Add a printer
  • Print
• Credits

Description

Creates a print server named "sys-print" and a named disposable "disp-sys-print" qube for sending files to your configured printer, which can be done over the network or with IPP-over-USB.

Security

The client does not have CUPS, does not need internet connection and does not have USB devices connected.

Using CUPS in a dedicated qube reduces attack surface and has a better usability as you only need to configure the printer in one qube and other qubes will have access through Qrexec.

If the devices connected to the server qube can attack the CUPS server, it can escalate the attack to the client qube. Usage of disposables servers does not prevent this from happening, it just avoids persistent infection on the server, where you could attribute different printers to different levels of trust.

Sending files to the print server with qvm-copy is always safer than allowing a direct connection from the qube that wants to print files to the qube that has access to the printer.

Installation

• Top:

sudo qubesctl top.enable sys-print
sudo qubesctl --targets=tpl-sys-print state.apply
sudo qubesctl top.disable sys-print
sudo qubesctl state.apply sys-print.appmenus

• State:

sudo qubesctl state.apply sys-print.create
sudo qubesctl --skip-dom0 --targets=tpl-sys-print state.apply sys-print.install
sudo qubesctl state.apply sys-print.appmenus

If you want to install all printer drivers:

sudo qubesctl --skip-dom0 --targets=tpl-sys-print state.apply sys-print.install-driver-all

On the client template:

sudo qubesctl --skip-dom0 --targets=TEMPLATE state.apply sys-print.install-client

The client qube requires the split Print service to be enabled:

qvm-features QUBE service.print-client 1

Access Control

Default policy (qusal.Print RPC service):

• Clients with tag print-client are allowed to call servers with tag print-server, defaulting to sys-print.
• All clients can ask servers with tag print-server, defaulting to sys-print.

Asking can spawn multiple requests depending on the client, usage of allow is recommended for trusted clients.

Add the tag print-client to the qube requesting the print content:

qvm-tags QUBE add print-client

As the call will default to sys-print, you can enforce the use of disp-sys-print via policy and not any other qube:

qusal.Print * @tag:print-client @default allow target=disp-sys-print
qusal.Print * @tag:print-client @anyvm   deny

Usage

Add a printer

You will configure your printer from sys-print or disp-sys-print, it can connect over the network or USB. If you do not want to save printing configuration, use disp-sys-print.

On sys-print or disp-sys-print, add your printer:

system-config-printer

Print

On the client, select the file to print, open it with an editor, viewer or browser and target the desired printer.

Credits

• Unman