[gnome-control-center] lock: Add USB protection entry

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 520ca91fe8bb01a9bc59c5ccf6e2a56c2b5b5a11
Author: Ludovico de Nittis <ludovico denittis collabora com>
Date:   Thu May 28 09:59:30 2020 +0200

    lock: Add USB protection entry
    
    In the screen lock tab we add a "Forbid new USB devices" entry with a
    switch to enable or disable said protection.
    
    The actual USB protection is handled by gnome-settings-daemon and
    USBGuard.
    
    We use the "Available" property of gnome-settings-daemon to check
    if we are able to offer the USB protection (i.e. USBGuard is
    installed with the minimum required version ecc..).
    If the host doesn't met the requirements we hide the USB
    protetion row entirely.
    
    Given the fact that the always on protection benefits are very slim we
    decided to give just an on/off switch that by default controls the
    "with lock screen" protection level.

 panels/lock/cc-lock-panel.c  | 106 ++++++++++++++++++++++++++++++++++++++-----
 panels/lock/cc-lock-panel.ui |  19 ++++++++
 2 files changed, 114 insertions(+), 11 deletions(-)
---
diff --git a/panels/lock/cc-lock-panel.c b/panels/lock/cc-lock-panel.c
index cab917dd4..86800e871 100644
--- a/panels/lock/cc-lock-panel.c
+++ b/panels/lock/cc-lock-panel.c
@@ -1,6 +1,7 @@
 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
  *
  * Copyright (C) 2018 Red Hat, Inc
+ * Copyright (C) 2020 Collabora Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -28,17 +29,23 @@
 
 struct _CcLockPanel
 {
-  CcPanel     parent_instance;
-
-  GSettings   *lock_settings;
-  GSettings   *notification_settings;
-  GSettings   *session_settings;
-
-  GtkSwitch   *automatic_screen_lock_switch;
-  GtkComboBox *blank_screen_combo;
-  GtkComboBox *lock_after_combo;
-  GtkListBox  *lock_list_box;
-  GtkSwitch   *show_notifications_switch;
+  CcPanel        parent_instance;
+
+  GSettings     *lock_settings;
+  GSettings     *notification_settings;
+  GSettings     *privacy_settings;
+  GSettings     *session_settings;
+
+  GCancellable  *cancellable;
+
+  GtkSwitch     *automatic_screen_lock_switch;
+  GtkComboBox   *blank_screen_combo;
+  GtkComboBox   *lock_after_combo;
+  GtkListBox    *lock_list_box;
+  GtkSwitch     *show_notifications_switch;
+  GtkSwitch     *usb_protection_switch;
+  GDBusProxy    *usb_proxy;
+  GtkListBoxRow *usb_protection_row;
 };
 
 CC_PANEL_REGISTER (CcLockPanel, cc_lock_panel)
@@ -178,14 +185,70 @@ on_blank_screen_delay_changed_cb (GtkWidget   *widget,
   g_settings_set_uint (self->session_settings, "idle-delay", value);
 }
 
+static void
+on_usb_protection_properties_changed_cb (GDBusProxy  *usb_proxy,
+                                         GVariant    *changed_properties,
+                                         GStrv        invalidated_properties,
+                                         CcLockPanel *self)
+{
+  gboolean available = FALSE;
+
+  if (self->usb_proxy)
+    {
+      g_autoptr(GVariant) variant = NULL;
+
+      variant = g_dbus_proxy_get_cached_property (self->usb_proxy, "Available");
+      if (variant != NULL)
+        available = g_variant_get_boolean (variant);
+    }
+
+  /* Show the USB protection row only if the required daemon is up and running */
+  gtk_widget_set_visible (GTK_WIDGET (self->usb_protection_row), available);
+}
+
+static void
+on_usb_protection_param_ready (GObject      *source_object,
+                               GAsyncResult *res,
+                               gpointer      user_data)
+{
+  g_autoptr(GError) error = NULL;
+  CcLockPanel *self;
+  GDBusProxy *proxy;
+
+  self = user_data;
+  proxy = g_dbus_proxy_new_for_bus_finish (res, &error);
+  if (error)
+    {
+      if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+        {
+          g_warning ("Failed to connect to SettingsDaemon.UsbProtection: %s",
+                     error->message);
+        }
+
+      gtk_widget_hide (GTK_WIDGET (self->usb_protection_row));
+      return;
+    }
+  self->usb_proxy = proxy;
+
+  g_signal_connect_object (self->usb_proxy,
+                           "g-properties-changed",
+                           G_CALLBACK (on_usb_protection_properties_changed_cb),
+                           self,
+                           0);
+  on_usb_protection_properties_changed_cb (self->usb_proxy, NULL, NULL, self);
+}
+
 static void
 cc_lock_panel_finalize (GObject *object)
 {
   CcLockPanel *self = CC_LOCK_PANEL (object);
 
+  g_cancellable_cancel (self->cancellable);
+  g_clear_object (&self->cancellable);
   g_clear_object (&self->lock_settings);
   g_clear_object (&self->notification_settings);
   g_clear_object (&self->session_settings);
+  g_clear_object (&self->usb_proxy);
 
   G_OBJECT_CLASS (cc_lock_panel_parent_class)->finalize (object);
 }
@@ -205,6 +268,8 @@ cc_lock_panel_class_init (CcLockPanelClass *klass)
   gtk_widget_class_bind_template_child (widget_class, CcLockPanel, lock_after_combo);
   gtk_widget_class_bind_template_child (widget_class, CcLockPanel, lock_list_box);
   gtk_widget_class_bind_template_child (widget_class, CcLockPanel, show_notifications_switch);
+  gtk_widget_class_bind_template_child (widget_class, CcLockPanel, usb_protection_switch);
+  gtk_widget_class_bind_template_child (widget_class, CcLockPanel, usb_protection_row);
 
   gtk_widget_class_bind_template_callback (widget_class, on_blank_screen_delay_changed_cb);
   gtk_widget_class_bind_template_callback (widget_class, on_lock_combo_changed_cb);
@@ -223,7 +288,10 @@ cc_lock_panel_init (CcLockPanel *self)
                                 cc_list_box_update_header_func,
                                 NULL, NULL);
 
+  self->cancellable = g_cancellable_new ();
+
   self->lock_settings = g_settings_new ("org.gnome.desktop.screensaver");
+  self->privacy_settings = g_settings_new ("org.gnome.desktop.privacy");
   self->notification_settings = g_settings_new ("org.gnome.desktop.notifications");
   self->session_settings = g_settings_new ("org.gnome.desktop.session");
 
@@ -249,4 +317,20 @@ cc_lock_panel_init (CcLockPanel *self)
 
   value = g_settings_get_uint (self->session_settings, "idle-delay");
   set_blank_screen_delay_value (self, value);
+
+  g_settings_bind (self->privacy_settings,
+                   "usb-protection",
+                   self->usb_protection_switch,
+                   "active",
+                   G_SETTINGS_BIND_DEFAULT);
+
+  g_dbus_proxy_new_for_bus (G_BUS_TYPE_SESSION,
+                            G_DBUS_PROXY_FLAGS_NONE,
+                            NULL,
+                            "org.gnome.SettingsDaemon.UsbProtection",
+                            "/org/gnome/SettingsDaemon/UsbProtection",
+                            "org.gnome.SettingsDaemon.UsbProtection",
+                            self->cancellable,
+                            on_usb_protection_param_ready,
+                            self);
 }
diff --git a/panels/lock/cc-lock-panel.ui b/panels/lock/cc-lock-panel.ui
index c3c8dbefa..85140eefa 100644
--- a/panels/lock/cc-lock-panel.ui
+++ b/panels/lock/cc-lock-panel.ui
@@ -114,6 +114,25 @@
                         </child>
                       </object>
                     </child>
+
+                    <!-- USB protection row -->
+                    <child>
+                      <object class="HdyActionRow" id="usb_protection_row">
+                        <property name="visible">false</property>
+                        <property name="title" translatable="yes">Forbid new _USB devices</property>
+                        <property name="subtitle" translatable="yes">Prevent new USB devices from 
interacting with the system when the screen is locked.</property>
+                        <property name="activatable-widget">usb_protection_switch</property>
+                        <property name="use-underline">true</property>
+                        <child type="action">
+                          <object class="GtkSwitch" id="usb_protection_switch">
+                            <property name="visible">true</property>
+                            <property name="halign">end</property>
+                            <property name="valign">center</property>
+                          </object>
+                        </child>
+                      </object>
+                    </child>
+
                     <style>
                       <class name="view"/>
                       <class name="frame"/>