Authenticating GTK app to run with root permissions

Question

I have a UI app (uses GTK) for Linux that requires to be run as root (it reads and writes /dev/sd*).

Instead of requiring the user to open a root shell or use "sudo" manually every time when he launches my app, I wonder if the app can use some OS-provided API to get root permissions. (Note: gtk app's can't use "setuid" mode, so that's not an option here.)

The advantage here would be an easier workflow: The user could, from his default user account, double click my app from the desktop instead of having to open a root terminal and launch it from there.

I ask this because OS X offers exactly this: An app can ask the OS to launch an executable with root permissions - the OS (and not the app) then asks the user to input his credentials, verifies them and then launches the target as desired.

I wonder if there's something similar for Linux (Ubuntu, e.g.)

Clarification:

So, after the hint at PolicyKit I wonder if I can use that to get r/w access to the "/dev/sd..." block devices. I find the documention quite hard to understand, so I thought I'd first ask whether this is possible at all before I spend hours on trying to understand it in vain.

Update:

The app is a remote operated disk repair tool for the unsavvy Linux user, and those Linux noobs won't have much understanding of using sudo or even changing their user's group memberships, especially if their disk just started acting up and they're freaking out. That's why I seek a solution that avoids technicalities like this.

Answer 1

The old way, simple but now being phased out, is GKSu. Here is the discussion on GKSu's future.

The new way is to use PolicyKit. I'm not quite sure how this works but I think you need to launch your app using the pkexec command.

UPDATE:

Looking at the example code on http://hal.freedesktop.org/docs/polkit/polkit-apps.html, it seems that you can use PolicyKit to obtain authorization for certain actions which are described by .policy files in /usr/share/polkit-1/actions. The action for executing a program as another user is org.freedesktop.policykit.exec. I can't seem to find an action for directly accessing block devices, but I have to admit, the PolicyKit documentation breaks my brain too.

So, perhaps the simplest course of action for you is to separate your disk-mangling code that requires privileges into a command-line utility, and run that from your GUI application using g_spawn_[a]sync() with pkexec. That way you wouldn't have to bother with requesting actions and that sort of thing. It's probably bad practice anyway to run your whole GUI application as root.

Another suggestion is to ask the author of PolicyKit (David Zeuthen) directly. Or try posting your question to the gtk-app-devel list.