bug#71969: [PATCH] Support interactive D-Bus authentication

[Steven Allen via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Michael Albinus <michael.albinus@gmx.de> writes:
> Steven Allen <steven@stebalien.com> writes:
>
> Hi Steven,
>
>>>> Sorry about that. To restart the bluetooth service, execute:
>>>>
>>>>     (dbus-call-method
>>>>      :system
>>>>      "org.freedesktop.systemd1" "/org/freedesktop/systemd1"
>>>>      "org.freedesktop.systemd1.Manager" "RestartUnit"
>>>>      :authorize t
>>>>      "bluetooth.service" "replace")
>>>>
>>>> Assuming you have a polkit agent running (most DEs will run one by
>>>> default, but agents like mate-polkit work pretty well standalone),
>>>> you'll be prompted to authorize the operation and the bluetooth service
>>>> will be restarted.
>>>
>>> Nice. I get an authorization prompt.
>>>
>>> However, on my Fedora 40 / Gnome 46 / systemd 255 system, it doesn't
>>> matter, whether I use ':authorize t', ':authorize nil', or none of
>>> them. Is interactive authorization enabled by default, and we don't need
>>> to care about?
>>
>> It worked for me as well until a recent update (likely polkit 124 or
>> systemd 256). I'm guessing one of these projects fixed a bug somewhere
>> as it sounds like this flag should always have been required.
>
> Hmm, I don't understand what you want to say.
>
> Anyway, I believe we shall add this feature to Emacs only when we have
> seen an example where it makes a difference.
>
> Best regards, Michael.

I meant that `dbus-method-call` worked without `:authorize t` for me as
well until I updated my system. Testing both systemd and fwupd, it
appears that the issue was caused by upgrading to systemd 256 (available
on Arch Linux but not Fedora 40). That is, systemd 256 requires
`:authorize t` while fwupd does not.

From what I can tell, this change was introduced in this [1] systemd PR.
Specifically, this comment:

    This also fixes a bunch of wrong uses of the "interactive" bool. The
    bool makes no sense today as the ALLOW_INTERACTIVE_AUTHORIZATION
    field in the D-Bus message header replaces it fully.

[1]: https://github.com/systemd/systemd/pull/30565