There is a standard way (working across Linux distributions) to launch a process (from another application) asking for the root password in order to elevate privileges?
I tried to use gksudo (it is installed in ubuntu by default), but under other distributions (or under other desktop manager) it may not be installed.
I would recommend looking at PolicyKit which is what most modern distros are using to accomplish this.
That works everywhere but does not cache the password and asks for the root and not the user password (as sudo does):
su - -c command
EDIT: Not on ubuntu where the root-account is disabled. Probably you need something like that:
test -x /usr/bin/sudo && sudo command || su - -c command
The only default thing is text mode su. Most distros have also sudo installed.
Now, in KDE based distros you'll have kdesu, while in GNOME based it'll be gksu and gksudo. Machines in Kerberized domains have ksu.
You might try to use /etc/sysconfig/desktop to see which is the default desktop.
Traditionally, if your application needs to allow a user to elevate privileges, it installs its own single-purpose setuid executable -- single-purpose meaning that it performs the task needed, instead of acting as a general-purpose launcher.
$ su -
# cp `type -p id` /usr/local/bin/root-id
# chown root:users /usr/local/bin/root-id
# chmod 4750 /usr/local/bin/root-id
$ /usr/local/bin/root-id
... euid=0(root) ...
OTOH setuid executables have also been a common source of security holes too, so exercise care.
