Greeter: Don't unlock persistence via the "Start Tails" button (refs: #17136)

We require to unlock the persistence via the "Unlock" button, to ensure
that the user gets some UI feedback when the persistent Greeter settings
are loaded.

The "Start Tails" is now insensitive if a password was entered in the
persistence password entry but persistence was not unlocked.

config/chroot_local-includes/usr/lib/python3/dist-packages/tailsgreeter/ui/main_window.py

@@ -176,20 +176,6 @@ class GreeterMainWindow(Gtk.Window, TranslatableWindow):
 
     # Actions
 
-    def check_and_login(self):
-        if (self.persistence_setting.has_persistence() and
-                self.entry_storage_passphrase.get_text() and
-                not self.persistence_setting.is_unlocked):
-            logging.debug("Unlocking persistent storage before login")
-            self.persistent_storage.unlock(unlocked_cb=self.finish_login)
-        else:
-            self.finish_login()
-
-    def finish_login(self):
-        logging.info("Starting the session")
-        self.greeter.login()
-        return False
-
     def add_setting(self, id_=None):
         response = self.dialog_add_setting.run(id_)
         if response == Gtk.ResponseType.YES:
@@ -298,7 +284,7 @@ class GreeterMainWindow(Gtk.Window, TranslatableWindow):
         return False
 
     def cb_button_start_clicked(self, widget, user_data=None):
-        self.check_and_login()
+        self.greeter.login()
         return False
 
     def cb_button_storage_unlock_clicked(self, widget, user_data=None):
@@ -311,6 +297,13 @@ class GreeterMainWindow(Gtk.Window, TranslatableWindow):
 
     def cb_entry_storage_passphrase_changed(self, editable, user_data=None):
         self.persistent_storage.passphrase_changed(editable)
+        # Only allow starting if the password entry is empty. We used to
+        # attempt unlocking with the entered password when the "Start Tails"
+        # button was clicked, but changed that behavior (see #17136), so
+        # we now force users to click the "Unlock" button first before
+        # they can click "Start Tails".
+        allow_start = not bool(editable.get_text())
+        self.button_start.set_sensitive(allow_start)
         return False
 
     def cb_infobar_close(self, infobar, user_data=None):

config/chroot_local-includes/usr/lib/python3/dist-packages/tailsgreeter/ui/persistent_storage.py

@@ -27,6 +27,7 @@ class PersistentStorage(object):
         self.infobar_persistence = builder.get_object('infobar_persistence')
         self.label_infobar_persistence = builder.get_object('label_infobar_persistence')
         self.spinner_storage_unlock = builder.get_object('spinner_storage_unlock')
+        self.button_start = builder.get_object("button_start")
 
         self.checkbutton_storage_show_passphrase.connect('toggled', self.cb_checkbutton_storage_show_passphrase_toggled)
 
@@ -112,6 +113,7 @@ class PersistentStorage(object):
                                                     Gtk.IconSize.BUTTON)
         self.image_storage_state.set_visible(True)
         self.box_storage_unlocked.set_visible(True)
+        self.button_start.set_sensitive(True)
 
     def cb_checkbutton_storage_show_passphrase_toggled(self, widget):
         self.entry_storage_passphrase.set_visibility(widget.get_active())