"pelzflorian (Florian Pelz)" <pelzflorian@pelzflorian.de> skriver:

> I’m reopening this bug because it is very similar to my issue.
>
> When using my Macbook’s keyboard XF86MonBrightnessUp/Down keys to
> adjust screen brightness (probably on non-Macbooks too) in GDM or
> MATE, I am asked to enter my authentication password to make
> gnome-settings-daemon’s libexec/gsd-backlight-helper (or some
> equivalent program on MATE) change screen brightness.
>
> This should not be so; gsd-backlight-helper should have PolicyKit, pam
> or setuid or whatever.

gnome-service-type installs a PolicyKit rule for gnome-settings-daemon.

Should the MATE service do the same?

To work around it locally, try adding:

  (simple-service 'gsd-polkit polkit-service-type
                  (list gnome-settings-daemon))

to the (services ...) section of your system configuration.