[Bug 2028172] Re: Cups-browsed cannot bind to port 631 as non-root user on Ubuntu 23.04

[Till Kamppeter]

Seth, this is an even better way, especially also as the systemd files
are part of the upstream repository and by setting the capabilities
there we do the change for all distributions, not just for Debian,
Ubuntu, and distros derived from those.


So let us go this way.

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https://bugs.launchpad.net/bugs/2028172

Title:
  Cups-browsed cannot bind to port 631 as non-root user on Ubuntu 23.04

Status in cups-browsed package in Ubuntu:
  Confirmed

Bug description:
  After upgrading to Ubuntu 23.04, my laptop failed to discover our print server.
  The problem seems to have been caused by a new change in cups-browsed that was added to Ubuntu 23.04.
  I looked into it and found a small fix that seems to solve my issue.

  Using the debug configuration for cupsd and cups-browsed, I looked through the logs and noticed the following line:
  failed to bind CUPS Browsing socket: Permission denied

  After reading more about printer advertisement and cups-browsed, I concluded that the printer is shared to my Ubuntu 23.04 laptop via CUPS on port 631.
  When I connected an Ubuntu 22.04 laptop to the WIFI network, I saw the printer really was being shared with CUPS on port 631.
  Cups-browsed was running as root on 22.04 while on 23.04 it is running as a new user - cups-browsed, but this new user didn't seem to have the necessary permissions to open a listening socket on port 631.
  The solution I tried was granting the relevant binding permissions to the binary with this command (on the 23.04):
  setcap cap_net_bind_service+ep /usr/sbin/cups-browsed

  After giving the permissions, my computer successfully discovered the printer, just like it used to on 22.04!
  I think the command should be added to the post install script or maybe the capability should be granted to the new cups-browsed user.
  I posted it as an issue in the CUPS project on github. They told me to post it here because its an Ubuntu issue: https://github.com/OpenPrinting/cups-browsed/issues/17

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