Murray's Blog

gnome-lirc-properties: Using PolicyKit to get sudo access

murrayc

Can’t get PolicyKit’s ObtainAuthorization() to work.

gnome-lirc-properties, which I just mentioned needs to edit /etc/lirc/lircd.conf, which requires sudo/root access. Various APIs exist to get temporary sudo/root access but everyone now seems to agree that the new PolicyKit system is the way to go. I’d like to link to a website for it. All the system administration control panels in Ubuntu Hardy Heron seem to use PolicyKit already.

But I can’t get the thing to work, maybe because I’m using Python, and I haven’t found any help so far. I have defined the PolicyKit mechanism, but I can’t get even a simple test of the ObtainAuthorization() method to do anything interesting. This python code does not return anything other than None from ObtainAuthorization() and none of the callbacks are called:

#!/usr/bin/python

import pygtk
pygtk.require('2.0')
import gtk

import dbus
import os

class TestWindow:
    def on_button_clicked(self, widget, data=None):

	#Call the D-Bus method to request PolicyKit authorization:

        session_bus = dbus.SessionBus()
        policykit = session_bus.get_object('org.freedesktop.PolicyKit.AuthenticationAgent', '/', "org.gnome.PolicyKit.AuthorizationManager.SingleInstance")
        if(policykit == None):
           print("Error: Could not get PolicyKit D-Bus Interface\n")

        gdkwindow = self.window.window
        xid = gdkwindow.xid

        print "Calling ObtainAuthorization..."

        #This complains that no ObtainAuthorization(ssi) exists:
        #granted = policykit.ObtainAuthorization("test_action_id", xid, os.getpid())

        #TODO: Neither of the async callbacks are called, and how could the return value be useful if it is async?
        # Note: Other code (such as gnome-panel) seems to use ShowDialog instead of ObtainAuthorization, though
        # ShowDialog is apparently deprecated (I don't know when), but that also has no effect.
        granted = policykit.ObtainAuthorization("test_action_id", xid, os.getpid(), reply_handler=self.__handleAuthReply, error_handler=self.__handleAuthError)

        print "...Finished."

        print "granted=", granted

    def __handleAuthReply(self, granted):
        print "handleAuthReply: granted\n"

    def __handleAuthError(self, exception):
        print "handleAuthError: not granted: %s\n" % exception

    def on_delete_event(self, widget, event, data=None):
        # Close the window:
        return False

    def on_destroy(self, widget, data=None):
        gtk.main_quit()

    def show(self):
       self.window.show()

    def __init__(self):

        self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        self.window.connect("delete_event", self.on_delete_event)
        self.window.connect("destroy", self.on_destroy)

        self.button = gtk.Button("Obtain Authorization")
        self.button.connect("clicked", self.on_button_clicked, None)
        self.window.add(self.button)
        self.button.show()

window = TestWindow()
window.show()
gtk.main()

gnome-lirc-properties has a real mechanism and tries to use ObtainAuthorization() for real, if someone wants to look at it properly. Here is the gnome-lirc-properties svn, and a tarball (it doesn’t do much yet).

How to use PolicyKit from an application

In return for asking the lazy web, I’ll try to describe how I think it should work, based mostly on David Zeuthen’s description. There are many opportunities to get something wrong:

Exit mobile version