Using the openvpn network manager applet, this strange error occured when trying to connect to my VPN. I also figured that the configuration edit was denied with a strange error on not being able to load the template.

Jan  4 16:57:03 nbmif NetworkManager[2872]:  Starting VPN service 'openvpn'...
Jan  4 16:57:03 nbmif NetworkManager[2872]:  VPN service 'openvpn' started (org.freedesktop.NetworkManager.openvpn), PID 6230
Jan  4 16:57:03 nbmif NetworkManager[2872]:  VPN service 'openvpn' appeared; activating connections
Jan  4 16:57:03 nbmif NetworkManager[2872]:  [1388851023.483964] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #3: (6) No agents were available for this request.
Jan  4 16:57:08 nbmif NetworkManager[2872]:  VPN service 'openvpn' disappeared

The gdm session log unveils that something is missing…

$ tail -f .cache/gdm/session.log

      JS LOG: Error 'VPN plugin at /usr/lib/NetworkManager/nm-openvpn-auth-dialog is not executable' while processing VPN keyfile '/etc/NetworkManager/VPN/nm-openvpn-service.name'

Looking at the openvpn service configuration itsself, it’s configured correct:

# vim /etc/NetworkManager/VPN/nm-openvpn-service.name

[GNOME]
auth-dialog=/usr/lib/NetworkManager/nm-openvpn-auth-dialog
properties=/usr/lib/NetworkManager/libnm-openvpn-properties
supports-external-ui-mode=true

But the file itsself is missing…

# ls -la /usr/lib/NetworkManager/nm-openvpn-auth-dialog
ls: Zugriff auf /usr/lib/NetworkManager/nm-openvpn-auth-dialog nicht möglich: Datei oder Verzeichnis nicht gefunden

Re-install the involved packages.

# apt-get install --reinstall network-manager-openvpn network-manager-openvpn-gnome

# ls -la /usr/lib/NetworkManager/nm-openvpn-auth-dialog
-rwxr-xr-x 1 root root 31K Sep 13 19:54 /usr/lib/NetworkManager/nm-openvpn-auth-dialog*

Now check the broken symlink for the gnome shell and manually fix it.

# ls -la /usr/lib/gnome-shell/nm-openvpn*
#
# ln -s /usr/lib/NetworkManager/nm-openvpn-auth-dialog /usr/lib/gnome-shell/
# ls -la /usr/lib/gnome-shell/nm-openvpn*
lrwxrwxrwx 1 root root 46 Jan  4 17:10 /usr/lib/gnome-shell/nm-openvpn-auth-dialog -> /usr/lib/NetworkManager/nm-openvpn-auth-dialog*

But still, it remains broken.

$ tail -f .cache/gdm/session.log

      JS LOG: Invalid VPN service type (cannot find authentication binary)

It’s necessary to not only restart the network manager, but also dbus in order to apply the changes. And while at it, save your current work, and reboot. Killing dbus while running a window manager isn’t much fun 😉

# service network-manager restart
# service dbus restart
# reboot

Kudos to this forum post out of many many bug reports and hints. It seems that package upgrade broke/changed the location of the auth dialog file which then broke everything, as usual.