[gdm/wip/rancell/autologin-accountsservice] Use automatic login configuration from AccountsService.

[Robert Ancell <rancell src gnome org>]

commit bb8b68c5c09b1b9b3edf91ece1779dee4797f1fe
Author: Robert Ancell <robert ancell canonical com>
Date:   Fri Dec 22 12:11:53 2017 +1300

    Use automatic login configuration from AccountsService.
    
    Currently the GDM autologin configuration is pulled from the GDM configuration.
    AccountsService already manages the autologin configuration (writing to the GDM
    custom.conf file). By using a new property in AccountsService [1] we can let
    AccountsService migrate to storing the configuration itself. This allows
    multiple display managers (e.g. LightDM) to share the same configuration.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791860
    
    [1] https://bugs.freedesktop.org/show_bug.cgi?id=104564

 daemon/gdm-manager.c |   83 ++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 67 insertions(+), 16 deletions(-)
---
diff --git a/daemon/gdm-manager.c b/daemon/gdm-manager.c
index 69bae91..d550cc5 100644
--- a/daemon/gdm-manager.c
+++ b/daemon/gdm-manager.c
@@ -1241,8 +1241,8 @@ get_timed_login_details (GdmManager *manager,
 }
 
 static gboolean
-get_automatic_login_details (GdmManager *manager,
-                             char      **usernamep)
+get_automatic_login_details_legacy (GdmManager *manager,
+                                    char      **usernamep)
 {
         gboolean res;
         gboolean enabled;
@@ -1282,6 +1282,64 @@ get_automatic_login_details (GdmManager *manager,
         return enabled;
 }
 
+static gchar *
+get_automatic_login_user (GdmManager *manager)
+{
+        g_autoptr(GDBusProxy) accountsservice_proxy = NULL;
+        g_autoptr(GVariant) result = NULL;
+        g_autoptr(GVariantIter) iter = NULL;
+        const gchar *path;
+        g_autoptr(GError) error = NULL;
+
+        accountsservice_proxy = g_dbus_proxy_new_sync (manager->priv->connection,
+                                                       0, NULL,
+                                                       "org.freedesktop.Accounts",
+                                                       "/org/freedesktop/Accounts",
+                                                       "org.freedesktop.Accounts",
+                                                       NULL,
+                                                       &error);
+        if (!accountsservice_proxy) {
+                g_warning ("Failed to contact accountsservice: %s", error->message);
+                return NULL;
+        }
+
+        /* If AccountsService doesn't support this property, fall back to old method */
+        result = g_dbus_proxy_get_cached_property (accountsservice_proxy, "AutomaticLoginUsers");
+        if (!result) {
+                char *username;
+                if (!get_automatic_login_details_legacy (manager, &username)) {
+                        return NULL;
+                }
+                return username;
+        }
+        if (!g_variant_is_of_type (result, G_VARIANT_TYPE ("ao"))) {
+                return NULL;
+        }
+
+        g_variant_get (result, "ao", &iter);
+        if (g_variant_iter_next (iter, "&o", &path)) {
+                g_autoptr(GDBusProxy) proxy = NULL;
+                g_autoptr(GVariant) username = NULL;
+
+                proxy = g_dbus_proxy_new_sync (manager->priv->connection,
+                                               0, NULL,
+                                               "org.freedesktop.Accounts",
+                                               path,
+                                               "org.freedesktop.Accounts.User",
+                                               NULL,
+                                               &error);
+                if (proxy == NULL) {
+                        g_warning ("Failed to get automatic login details from AccountsService for user %s: 
%s", path, error->message);
+                        return NULL;
+                }
+
+                username = g_dbus_proxy_get_cached_property (proxy, "UserName");
+                return g_variant_dup_string (username, NULL);
+        }
+
+        return NULL;
+}
+
 static void
 maybe_start_pending_initial_login (GdmManager *manager,
                                    GdmDisplay *greeter_display)
@@ -1577,17 +1635,14 @@ set_up_session (GdmManager *manager,
         ActUser *user;
         gboolean loaded;
         gboolean is_initial_display = FALSE;
-        gboolean autologin_enabled = FALSE;
-        char *username = NULL;
+        g_autofree gchar *username = NULL;
 
         g_object_get (G_OBJECT (display), "is-initial", &is_initial_display, NULL);
 
         if (!manager->priv->ran_once && is_initial_display)
-                autologin_enabled = get_automatic_login_details (manager, &username);
-
-        if (!autologin_enabled) {
-                g_free (username);
+                username = get_automatic_login_user (manager);
 
+        if (username == NULL) {
 #ifdef HAVE_LIBXDMCP
                 if (GDM_IS_XDMCP_CHOOSER_DISPLAY (display)) {
                         set_up_chooser_session (manager, display);
@@ -1612,7 +1667,7 @@ set_up_session (GdmManager *manager,
                 operation = g_new (UsernameLookupOperation, 1);
                 operation->manager = g_object_ref (manager);
                 operation->display = g_object_ref (display);
-                operation->username = username;
+                operation->username = g_steal_pointer (&username);
 
                 g_signal_connect (user,
                                   "notify::is-loaded",
@@ -2214,8 +2269,7 @@ on_session_conversation_started (GdmSession *session,
                                  GdmManager *manager)
 {
         GdmDisplay *display;
-        gboolean    enabled;
-        char       *username;
+        g_autofree gchar *username = NULL;
 
         g_debug ("GdmManager: session conversation started for service %s", service_name);
 
@@ -2234,9 +2288,8 @@ on_session_conversation_started (GdmSession *session,
                 return;
         }
 
-        enabled = get_automatic_login_details (manager, &username);
-
-        if (! enabled) {
+        username = get_automatic_login_user (manager);
+        if (username == NULL) {
                 return;
         }
 
@@ -2245,8 +2298,6 @@ on_session_conversation_started (GdmSession *session,
         /* service_name will be "gdm-autologin"
          */
         gdm_session_setup_for_user (session, service_name, username);
-
-        g_free (username);
 }
 
 static void