Proper username detection for Postfix

'grp' module that was used in Postfix autodetection,
to retrieve username monasca-agent runs with' was actually
returning the gropname of that user.

Instead of retrieving gid, new code retrieves user uid and later
on, using pwd module, retrieves its username.

Detected on SLES SP 12.

Change-Id: I3da4ca138424d065a8373b5786673dd265bdfaac

monasca_setup/detection/plugins/postfix.py

@@ -1,39 +1,64 @@
 # (c) Copyright 2015-2016 Hewlett Packard Enterprise Development LP
+# Copyright 2017 Fujitsu LIMITED
 
-import grp
 import logging
 import os
+import pwd
 import yaml
 
-import monasca_setup.agent_config
-import monasca_setup.detection
+from monasca_setup import agent_config
+from monasca_setup.detection import plugin
+from monasca_setup.detection import utils
 
 log = logging.getLogger(__name__)
 
+_POSTFIX_PROC_NAME = 'postfix'
+_POSTFIX_DIRECTORY = """/var/spool/postfix"""
+_POSTFIX_CHECK_COMMAND = ('sudo -l -U {0} find %s/incoming '
+                          '-type f > /dev/null' % _POSTFIX_DIRECTORY)
+"""Command to verify if user running monasca-agent
+ has sudo permission to access postfix directory"""
 
-class Postfix(monasca_setup.detection.Plugin):
+
+class Postfix(plugin.Plugin):
     """If postfix is running install the default config.
     """
+
+    ERROR_MSG = 'postfix plugin will not be configured.'
+
     def _detect(self):
         """Run detection, set self.available True if the service is detected.
 
         """
-        # Detect Agent's OS username by getting the group owner of confg file
+
         try:
-            gid = os.stat('/etc/monasca/agent/agent.yaml').st_gid
-            agent_user = grp.getgrgid(gid)[0]
-        except OSError:
-            agent_user = None
-        if monasca_setup.detection.find_process_cmdline('postfix') is not None:
-            # Test for sudo access
-            test_sudo = os.system('sudo -l -U {0} find /var/spool/postfix/incoming -type f > /dev/null'.format(agent_user))
-            if test_sudo != 0:
-                log.info("Postfix found but the required sudo access is not configured.\n\t" +
-                         "Refer to plugin documentation for more detail")
-                return False
-            self.available = True
-        else:
+            has_process = (utils.find_process_cmdline(_POSTFIX_PROC_NAME)
+                           is not None)
+            agent_user = self._get_agent_username() if has_process else None
+            has_user = agent_user is not None
+            has_sudoers = (self._has_sudoers(agent_user)
+                           if agent_user else False)
+        except Exception:
             self.available = False
+            detailed_msg = ('Unexpected exception while '
+                            'running postfix detection.')
+            log.exception('%s\n%s' % (detailed_msg, self.ERROR_MSG))
+        else:
+            self.available = has_process and has_sudoers
+            if not self.available:
+                if not has_process:
+                    detailed_msg = ('%s process was not found.'
+                                    % _POSTFIX_PROC_NAME)
+                    log.info('%s\n%s' % (detailed_msg, self.ERROR_MSG))
+                elif not has_user:
+                    detailed_msg = 'Did not locate agent\'s username.'
+                    log.error('%s\n%s' % (detailed_msg, self.ERROR_MSG))
+                elif not has_sudoers:
+                    detailed_msg = ('%s cannot access %s directory. '
+                                    '\n Refer to postfix plugin documentation '
+                                    'for more details.'
+                                    % (agent_user, _POSTFIX_DIRECTORY))
+                    log.error('%s\n%s' % (detailed_msg, self.ERROR_MSG))
 
     def build_config(self):
         """Build the config as a Plugins object and return.
@@ -43,9 +68,20 @@ class Postfix(monasca_setup.detection.Plugin):
         # plugin is the exception not the rule
         with open(os.path.join(self.template_dir, 'conf.d/postfix.yaml.example'), 'r') as postfix_template:
             default_net_config = yaml.safe_load(postfix_template.read())
-        config = monasca_setup.agent_config.Plugins()
+        config = agent_config.Plugins()
         config['postfix'] = default_net_config
         return config
 
     def dependencies_installed(self):
         return True
+
+    @staticmethod
+    def _get_agent_username():
+        uid = os.stat('/etc/monasca/agent/agent.yaml').st_uid
+        agent_user = pwd.getpwuid(uid).pw_name
+        return agent_user
+
+    @staticmethod
+    def _has_sudoers(agent_user):
+        test_sudo = os.system(_POSTFIX_CHECK_COMMAND.format(agent_user))
+        return test_sudo == 0