[pkg-gnupg-maint] Bug#842015: Merging bugs about pinentry failing without GNOME-connected d-bus

[Daniel Kahn Gillmor]

On Tue 2016-11-08 02:55:22 -0600, Vincent Lefevre wrote:
> Then, there should be another mean (I don't know which one) so that
> pinentry-gnome3 displays the prompt at the right place, e.g. when
> the user has an X session open locally on the machine but also
> accesses the machine remotely via ssh and the user runs gpg from
> this remote access.
>
> Communicating with the d-bus session only doesn't seem to be enough
> since DBUS_SESSION_BUS_ADDRESS has the same value under X and via ssh.

they do share a d-bus session in some circumstances (e.g. when
dbus-user-session is installed), and they do not in others.  But I hear
you that the situation you want changed is happening when they do share
a session.

> It should use the information about the current screen. Under X11,
> this comes from DISPLAY (I don't think there's another way because
> the user can choose where something should be displayed by directly
> changing the value of DISPLAY, and disregarding DISPLAY would not
> honor this requirement). For wayland, probably WAYLAND_DISPLAY, but
> according to the package description, only X and text terminals are
> currently supported by pinentry-gnome3: "If the X Window System is
> not active then an alternative text-mode dialog will be used."

I consider this a bug in pinentry-gnome3's documentation -- it does not
care about the X Window system at all, but rather uses d-bus.

> And if you mean that pinentry-gnome3 should delegate the display
> to GNOME so that it doesn't have to know whether X or wayland or
> whatever is used, then fine, but:
>
> * It should still have a fallback to X / terminal when GNOME is not
>   used (this is my case here).

If Gcr (the GNOME crypto kit, which includes the system prompter) is not
available on the current d-bus session, pinentry-gnome3 *does* fall back
to the terminal.  Are you suggesting that we should be checking for some
other test?

> * It should be able to detect whether the user is in front of his
>   GNOME session or accesses the machine in some other way (e.g.
>   ssh from a remote machine).

Can you recommend a mechanism for this?  What would you test?

We could simply test for the presence of $DISPLAY *even though
pinentry-gnome3 doesn't need it* and fall back if it is unset.

But pinentry-gnome3's end-user prompts currently work even when they're
run from a process where DISPLAY has unset for whatever reason.  It
sounds like you're asking to break this functionality.

Another possible approach would be to prompt via the terminal *in
addition* to prompting graphically, if the current d-bus session knows
about an X11 session, but that X11 session does not match the current
value of $DISPLAY (e.g. if $DISPLAY is unset, or if it is set to a
different value).

To begin that work, we'd need to be able to query d-bus about what
current X11 session it believes it is attached to.  I don't know how to
do that.  do you?

>> Perhaps you mean to be using pinentry-gtk-2?
>
> pinentry-gnome3 is used by default, so in any case, it should work
> correctly.

pinentry-gnome3 is used by default if it is installed.  But the default
pinentry that will be installed if you just "apt install gnupg" will be
pinentry-curses.

Regards,

        --dkg
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