don't allow downgrades for self-update

azurelinuxagent/ga/agent_update_handler.py

@@ -58,7 +58,12 @@ def __should_update_agent(self, requested_version):
         largest version update(self-update):
             update is allowed once per (as specified in the conf.get_hotfix_upgrade_frequency() or conf.get_normal_upgrade_frequency())
             return false when we don't allow updates.
+        Note: Downgrades are not allowed for self-update.
         """
+
+        if not self.__check_if_downgrade_is_requested_and_allowed(requested_version):
+            return False
+
         now = datetime.datetime.now()
 
         if self._is_requested_version_update:
@@ -261,6 +266,19 @@ def __get_all_agents_on_disk():
         path = os.path.join(conf.get_lib_dir(), "{0}-*".format(AGENT_NAME))
         return [GuestAgent.from_installed_agent(path=agent_dir) for agent_dir in glob.iglob(path) if os.path.isdir(agent_dir)]
 
+    def __check_if_downgrade_is_requested_and_allowed(self, requested_version):
+        """
+        Don't allow downgrades for self-update version
+        Note: The intention of this check is to keep the original behavior of self-update as it is.
+        """
+        if not self._is_requested_version_update:
+            if requested_version < CURRENT_VERSION:
+                msg = "Downgrade requested in the GoalState, but downgrades are not supported for self-update version:{0}, " \
+                      "skipping agent update".format(requested_version)
+                self.__log_event(LogLevel.INFO, msg)
+                return False
+        return True
+
     @staticmethod
     def __log_event(level, msg, success=True):
         if level == LogLevel.INFO:

tests/ga/test_agent_update_handler.py

@@ -148,6 +148,14 @@ def test_it_should_update_to_largest_version_if_time_window_elapsed(self):
                         self.__assert_agent_directories_exist_and_others_dont_exist(versions=[str(CURRENT_VERSION), "99999.0.0.0"])
                         self.assertIn("Agent update found, exiting current process", ustr(context.exception.reason))
 
+    def test_it_should_not_allow_update_if_largest_version_below_current_version(self):
+        self.prepare_agents(count=1)
+        data_file = DATA_FILE.copy()
+        data_file["ga_manifest"] = "wire/ga_manifest_no_upgrade.xml"
+        with self.__get_agent_update_handler(test_data=data_file) as (agent_update_handler, _):
+            agent_update_handler.run(agent_update_handler._protocol.get_goal_state())
+            self.__assert_agent_directories_exist_and_others_dont_exist(versions=[str(CURRENT_VERSION)])
+
     def test_it_should_not_agent_update_if_last_attempted_update_time_not_elapsed(self):
         self.prepare_agents(count=1)
         data_file = DATA_FILE.copy()