Changes to launchd plists parser plugin (#4803)

plaso/parsers/plist.py

@@ -145,13 +145,6 @@ def ParseFileObject(self, parser_mediator, file_object):
     display_name = parser_mediator.GetDisplayName()
     filename_lower_case = filename.lower()
 
-    try:
-      top_level_keys = set(top_level_object.keys())
-    except AttributeError as exception:
-      raise errors.WrongParser(
-          'Unable to parse top level keys of: {0:s} with error: {1!s}.'.format(
-              filename, exception))
-
     found_matching_plugin = False
     for plugin_name, plugin in self._plugins_per_name.items():
       if parser_mediator.abort:
@@ -170,13 +163,17 @@ def ParseFileObject(self, parser_mediator, file_object):
             if path_filter.Match(filename_lower_case):
               path_filter_match = True
 
-        result = (path_filter_match and
-                  top_level_keys.issuperset(plugin.PLIST_KEYS))
+        try:
+          required_format = plugin.CheckRequiredFormat(top_level_object)
+        except Exception as exception:  # pylint: disable=broad-except
+          parser_mediator.ProduceExtractionWarning((
+              'plugin: {0:s} unable to parse plist file with error: '
+              '{1!s}').format(plugin_name, exception))
 
       finally:
         parser_mediator.SampleFormatCheckStopTiming(profiling_name)
 
-      if not result:
+      if not path_filter_match or not required_format:
         logger.debug('Skipped parsing file: {0:s} with plugin: {1:s}'.format(
             display_name, plugin_name))
         continue

plaso/parsers/plist_plugins/interface.py

@@ -690,13 +690,13 @@ class PlistPlugin(plugins.BasePlugin):
   NAME = 'plist_plugin'
 
   # This is expected to be overridden by the processing plugin, for example:
-  # frozenset(PlistPathFilter('com.apple.bluetooth.plist'))
+  # PLIST_PATH_FILTERS = frozenset(PlistPathFilter('com.apple.bluetooth.plist'))
   PLIST_PATH_FILTERS = frozenset()
 
-  # PLIST_KEYS is a list of keys required by a plugin.
-  # This is expected to be overridden by the processing plugin.
-  # Ex. frozenset(['DeviceCache', 'PairedDevices'])
-  PLIST_KEYS = frozenset(['any'])
+  # PLIST_KEYS is a list of keys required by a plugin. This is expected to be
+  # overridden by the processing plugin, for example:
+  # PLIST_KEYS = frozenset(['DeviceCache', 'PairedDevices'])
+  PLIST_KEYS = frozenset()
 
   def _GetDateTimeValueFromPlistKey(self, plist_key, plist_value_name):
     """Retrieves a date and time value from a specific value in a plist key.
@@ -750,6 +750,7 @@ def _GetKeys(self, top_level, keys, depth=1):
       # Return an empty dict here if top_level is a list object, which happens
       # if the plist file is flat.
       return match
+
     keys = set(keys)
 
     if depth == 1:
@@ -857,6 +858,17 @@ def _ParsePlist(
       top_level (Optional[dict[str, object]]): plist top-level item.
     """
 
+  def CheckRequiredFormat(self, top_level):
+    """Check if the plist has the minimal structure required by the plugin.
+
+    Args:
+      top_level (dict[str, object]): plist top-level item.
+
+    Returns:
+      bool: True if this is the correct plugin, False otherwise.
+    """
+    return set(top_level.keys()).issuperset(self.PLIST_KEYS)
+
   def Process(self, parser_mediator, top_level=None, **kwargs):
     """Extracts events from a plist file.
 

plaso/parsers/plist_plugins/launchd.py

@@ -56,12 +56,25 @@ class MacOSLaunchdPlistPlugin(interface.PlistPlugin):
   # /Library/LaunchAgents/*.plist
   # ~/Library/LaunchAgents
 
-  PLIST_KEYS = frozenset([
-      'GroupName',
-      'Label',
-      'Program',
-      'ProgramArguments',
-      'UserName'])
+  # The Mac OS documentation indicates that Label and # ProgramArguments are
+  # required keys, lauchd plists have been observed  that contain Label and
+  # Program keys.
+
+  PLIST_KEYS = frozenset(['Label'])
+
+  def CheckRequiredFormat(self, top_level):
+    """Check if the plist has the minimal structure required by the plugin.
+
+    Args:
+      top_level (dict[str, object]): plist top-level item.
+
+    Returns:
+      bool: True if this is the correct plugin, False otherwise.
+    """
+    if not super(MacOSLaunchdPlistPlugin, self).CheckRequiredFormat(top_level):
+      return False
+
+    return 'Program' in top_level or 'ProgramArguments' in top_level
 
   # pylint: disable=arguments-differ
   def _ParsePlist(self, parser_mediator, top_level=None, **unused_kwargs):
@@ -74,8 +87,12 @@ def _ParsePlist(self, parser_mediator, top_level=None, **unused_kwargs):
     """
     program = top_level.get('Program', None)
     program_arguments = top_level.get('ProgramArguments', None)
+    if not (program or program_arguments):
+      return
     if program and program_arguments:
       program = ' '.join([program, ' '.join(program_arguments)])
+    elif program_arguments:
+      program = ' '.join(program_arguments)
 
     event_data = MacOSLaunchdEventData()
     event_data.group_name = top_level.get('GroupName')

test_data/launchd.minimal.plist

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>Label</key>
+	<string>foo</string>
+	<key>Program</key>
+	<string>/usr/bin/true</string>
+</dict>
+</plist>

test_data/launchd.noprogram.plist

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>Label</key>
+	<string>foo</string>
+	<key>ProgramArguments</key>
+	<array>
+		<string>/usr/bin/true</string>
+	</array>
+</dict>
+</plist>

tests/parsers/plist_plugins/launchd.py

@@ -42,6 +42,62 @@ def testProcess(self):
     event_data = storage_writer.GetAttributeContainerByIndex('event_data', 0)
     self.CheckEventData(event_data, expected_event_values)
 
+  def testProcessMinimal(self):
+    """Tests the Process function."""
+    plist_name = 'launchd.minimal.plist'
+
+    plugin = launchd.MacOSLaunchdPlistPlugin()
+    storage_writer = self._ParsePlistFileWithPlugin(
+        plugin, [plist_name], plist_name)
+
+    number_of_event_data = storage_writer.GetNumberOfAttributeContainers(
+        'event_data')
+    self.assertEqual(number_of_event_data, 1)
+
+    number_of_warnings = storage_writer.GetNumberOfAttributeContainers(
+        'extraction_warning')
+    self.assertEqual(number_of_warnings, 0)
+
+    number_of_warnings = storage_writer.GetNumberOfAttributeContainers(
+        'recovery_warning')
+    self.assertEqual(number_of_warnings, 0)
+
+    expected_event_values = {
+        'data_type': 'macos:launchd:entry',
+        'name': 'foo',
+        'program': '/usr/bin/true'}
+
+    event_data = storage_writer.GetAttributeContainerByIndex('event_data', 0)
+    self.CheckEventData(event_data, expected_event_values)
+
+  def testProcessNoProgram(self):
+    """Tests the Process function."""
+    plist_name = 'launchd.noprogram.plist'
+
+    plugin = launchd.MacOSLaunchdPlistPlugin()
+    storage_writer = self._ParsePlistFileWithPlugin(
+        plugin, [plist_name], plist_name)
+
+    number_of_event_data = storage_writer.GetNumberOfAttributeContainers(
+        'event_data')
+    self.assertEqual(number_of_event_data, 1)
+
+    number_of_warnings = storage_writer.GetNumberOfAttributeContainers(
+        'extraction_warning')
+    self.assertEqual(number_of_warnings, 0)
+
+    number_of_warnings = storage_writer.GetNumberOfAttributeContainers(
+        'recovery_warning')
+    self.assertEqual(number_of_warnings, 0)
+
+    expected_event_values = {
+        'data_type': 'macos:launchd:entry',
+        'name': 'foo',
+        'program': '/usr/bin/true'}
+
+    event_data = storage_writer.GetAttributeContainerByIndex('event_data', 0)
+    self.CheckEventData(event_data, expected_event_values)
+
 
 if __name__ == '__main__':
   unittest.main()