111 lines
4 KiB
Python
111 lines
4 KiB
Python
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#
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# screensaver.py - Screensaver management methods and data
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#
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# Copyright (C) 2014 Red Hat, Inc. All rights reserved.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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"""The screensaver inhibition module.
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The "screensaver" term includes the following effects, none of which we want during installation:
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- locking the screen
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- turning off the screen
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- suspending the system
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See also the origin bz: https://bugzilla.redhat.com/show_bug.cgi?id=928825
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We are using the freedesktop D-Bus api for inhibiting the screensaver:
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https://people.freedesktop.org/~hadess/idle-inhibition-spec/re01.html
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Note this does NOT use the systemd / logind API with similar name and capability!
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The D-Bus api lives on the session bus. Connections to the session bus must be made with the
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effective UID of the login user, which in live installs is not the UID of anaconda. This means
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we need to call seteuid while creating the proxy and making calls on the bus.
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Additionally, at the time of writing, creating the proxy actually starts the session bus daemon
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and so creates the bus. Conversely, when the proxy stops existing, the bus goes down.
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The inhibition is in effect only if all of these conditions are met:
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- The process called Inhibit on the session bus for the correct user.
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- The process exists.
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- The session bus exists.
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- The process did not call UnInhibit on the session bus with the right cookie.
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Altogether this means that once the proxy is correctly created, we call Inhibit, and then
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the proxy object must exist as long as we want the inhibition to be in effect.
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"""
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import os
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from dasbus.connection import SessionMessageBus
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from dasbus.error import DBusError
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from dasbus.identifier import DBusServiceIdentifier
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from pyanaconda.anaconda_loggers import get_module_logger
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log = get_module_logger(__name__)
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__all__ = ["inhibit_screensaver", "uninhibit_screensaver"]
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session_proxy = None
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inhibit_id = None
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class SetEuidFromPkexec():
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"""Context manager to temporarily set euid from env. variable set by consolehelper.
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Live installs use pkexec to run as root, which sets the original UID in $PKEXEC_UID.
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"""
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def __init__(self):
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self.old_euid = None
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def __enter__(self):
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if "PKEXEC_UID" in os.environ:
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self.old_euid = os.geteuid()
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new_euid = int(os.environ["PKEXEC_UID"])
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os.seteuid(new_euid)
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return self
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def __exit__(self, exc_type, exc_value, exc_traceback):
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if self.old_euid is not None:
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os.seteuid(self.old_euid)
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self.old_euid = None
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def inhibit_screensaver():
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"""Inhibit the "screensaver" idle timer."""
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log.info("Inhibiting screensaver.")
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global session_proxy
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global inhibit_id
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try:
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with SetEuidFromPkexec():
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SCREENSAVER = DBusServiceIdentifier(
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namespace=("org", "freedesktop", "ScreenSaver"),
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message_bus=SessionMessageBus()
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)
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session_proxy = SCREENSAVER.get_proxy()
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inhibit_id = session_proxy.Inhibit("anaconda", "Installing")
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except DBusError as e:
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log.warning("Unable to inhibit the screensaver: %s", e)
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def uninhibit_screensaver():
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"""Re-enable the "screensaver" idle timer."""
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if session_proxy is None or inhibit_id is None:
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return
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log.info("Un-inhibiting screensaver.")
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try:
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with SetEuidFromPkexec():
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session_proxy.UnInhibit(inhibit_id)
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except (DBusError, KeyError) as e:
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log.warning("Unable to uninhibit the screensaver: %s", e)
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