logind: introduce LockedHint and SetLockedHint (systemd#3238)

Desktop environments can keep this property up to date to allow
applications to easily track session's Lock status.

src/login/logind-session-dbus.c

@@ -180,6 +180,24 @@ static int property_get_idle_since_hint(
         return sd_bus_message_append(reply, "t", u);
 }
 
+static int property_get_locked_hint(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        Session *s = userdata;
+
+        assert(bus);
+        assert(reply);
+        assert(s);
+
+        return sd_bus_message_append(reply, "b", session_get_locked_hint(s) > 0);
+}
+
 int bus_session_method_terminate(sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Session *s = userdata;
         int r;
@@ -279,6 +297,35 @@ static int method_set_idle_hint(sd_bus_message *message, void *userdata, sd_bus_
         return sd_bus_reply_method_return(message, NULL);
 }
 
+static int method_set_locked_hint(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL;
+        Session *s = userdata;
+        uid_t uid;
+        int r, b;
+
+        assert(message);
+        assert(s);
+
+        r = sd_bus_message_read(message, "b", &b);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_query_sender_creds(message, SD_BUS_CREDS_EUID, &creds);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_creds_get_euid(creds, &uid);
+        if (r < 0)
+                return r;
+
+        if (uid != 0 && uid != s->user->uid)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Only owner of session may set locked hint");
+
+        session_set_locked_hint(s, b);
+
+        return sd_bus_reply_method_return(message, NULL);
+}
+
 int bus_session_method_kill(sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Session *s = userdata;
         const char *swho;
@@ -487,12 +534,14 @@ const sd_bus_vtable session_vtable[] = {
         SD_BUS_PROPERTY("IdleHint", "b", property_get_idle_hint, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
         SD_BUS_PROPERTY("IdleSinceHint", "t", property_get_idle_since_hint, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
         SD_BUS_PROPERTY("IdleSinceHintMonotonic", "t", property_get_idle_since_hint, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+        SD_BUS_PROPERTY("LockedHint", "b", property_get_locked_hint, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
 
         SD_BUS_METHOD("Terminate", NULL, NULL, bus_session_method_terminate, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("Activate", NULL, NULL, bus_session_method_activate, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("Lock", NULL, NULL, bus_session_method_lock, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("Unlock", NULL, NULL, bus_session_method_lock, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("SetIdleHint", "b", NULL, method_set_idle_hint, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("SetLockedHint", "b", NULL, method_set_locked_hint, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("Kill", "si", NULL, bus_session_method_kill, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("TakeControl", "b", NULL, method_take_control, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("ReleaseControl", NULL, NULL, method_release_control, SD_BUS_VTABLE_UNPRIVILEGED),

src/login/logind-session.c

@@ -852,6 +852,23 @@ void session_set_idle_hint(Session *s, bool b) {
         manager_send_changed(s->manager, "IdleHint", "IdleSinceHint", "IdleSinceHintMonotonic", NULL);
 }
 
+int session_get_locked_hint(Session *s) {
+        assert(s);
+
+        return s->locked_hint;
+}
+
+void session_set_locked_hint(Session *s, bool b) {
+        assert(s);
+
+        if (s->locked_hint == b)
+                return;
+
+        s->locked_hint = b;
+
+        session_send_changed(s, "LockedHint", NULL);
+}
+
 static int session_dispatch_fifo(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
         Session *s = userdata;
 

src/login/logind-session.h

@@ -105,6 +105,8 @@ struct Session {
         bool idle_hint;
         dual_timestamp idle_hint_timestamp;
 
+        bool locked_hint;
+
         bool in_gc_queue:1;
         bool started:1;
         bool stopping:1;
@@ -132,6 +134,8 @@ int session_activate(Session *s);
 bool session_is_active(Session *s);
 int session_get_idle_hint(Session *s, dual_timestamp *t);
 void session_set_idle_hint(Session *s, bool b);
+int session_get_locked_hint(Session *s);
+void session_set_locked_hint(Session *s, bool b);
 int session_create_fifo(Session *s);
 int session_start(Session *s);
 int session_stop(Session *s, bool force);

src/login/org.freedesktop.login1.conf

@@ -232,6 +232,10 @@
                        send_interface="org.freedesktop.login1.Session"
                        send_member="SetIdleHint"/>
 
+                <allow send_destination="org.freedesktop.login1"
+                       send_interface="org.freedesktop.login1.Session"
+                       send_member="SetLockedHint"/>
+
                 <allow send_destination="org.freedesktop.login1"
                        send_interface="org.freedesktop.login1.Session"
                        send_member="Kill"/>