"""Text parser plugin for SELinux audit log (audit.log) files.
audit.log log line example:
type=AVC msg=audit(1105758604.519:420): avc: denied { getattr } for pid=5962
comm="httpd" path="/home/auser/public_html" dev=sdb2 ino=921135
Where msg=audit(1105758604.519:420) contains the number of seconds since January 1, 1970
00:00:00 UTC and the number of milliseconds after the dot for example: "seconds:
1105758604, milliseconds: 519".
The number after the timestamp (420 in the example) is a 'serial number' that can be
used to correlate multiple logs generated from the same event.
"""
import pyparsing
from dfdatetime import posix_time as dfdatetime_posix_time
from plaso.containers import events
from plaso.lib import definitions
from plaso.lib import errors
from plaso.parsers import text_parser
from plaso.parsers.text_plugins import interface
[docs]
class SELinuxLogEventData(events.EventData):
"""SELinux log event data.
Attributes:
audit_type (str): audit type.
body (str): body of the log line.
last_written_time (dfdatetime.DateTimeValues): entry last written date and
time.
pid (int): process identifier (PID) that created the SELinux log line.
"""
DATA_TYPE = "selinux:line"
[docs]
def __init__(self):
"""Initializes event data."""
super().__init__(data_type=self.DATA_TYPE)
self.audit_type = None
self.body = None
self.last_written_time = None
self.pid = None
[docs]
class SELinuxTextPlugin(interface.TextPlugin):
"""Text parser plugin for SELinux audit log (audit.log) files."""
NAME = "selinux"
DATA_FORMAT = "SELinux audit log (audit.log) file"
_INTEGER = pyparsing.Word(pyparsing.nums).set_parse_action(
lambda tokens: int(tokens[0], 10)
)
_KEY_VALUE_GROUP = pyparsing.Group(
pyparsing.Word(pyparsing.alphanums)
+ pyparsing.Suppress("=")
+ (pyparsing.QuotedString('"') ^ pyparsing.Word(pyparsing.printables))
)
_KEY_VALUE_DICT = pyparsing.Dict(pyparsing.ZeroOrMore(_KEY_VALUE_GROUP))
_TIMESTAMP = pyparsing.Group(_INTEGER + pyparsing.Suppress(".") + _INTEGER)
_END_OF_LINE = pyparsing.Suppress(pyparsing.LineEnd())
# A log line is formatted as: type=TYPE msg=audit([0-9]+\.[0-9]+:[0-9]+): .*
_LOG_LINE = (
pyparsing.Suppress("type=")
+ (
pyparsing.Word(pyparsing.srange("[A-Z_]"))
^ pyparsing.Regex(r"UNKNOWN\[[0-9]+\]")
).set_results_name("type")
+ pyparsing.Suppress("msg=audit(")
+ _TIMESTAMP.set_results_name("timestamp")
+ pyparsing.Suppress(":")
+ _INTEGER
+ pyparsing.Suppress("):")
+ pyparsing.restOfLine().set_results_name("body")
+ _END_OF_LINE
)
_LINE_STRUCTURES = [("log_line", _LOG_LINE)]
VERIFICATION_GRAMMAR = _LOG_LINE
def _ParseRecord(self, parser_mediator, key, structure):
"""Parses a pyparsing structure.
Args:
parser_mediator (ParserMediator): mediates interactions between parsers
and other components, such as storage and dfVFS.
key (str): name of the parsed structure.
structure (pyparsing.ParseResults): tokens from a parsed log line.
Raises:
ParseError: if the structure cannot be parsed.
"""
if key == "log_line":
time_elements_structure = self._GetValueFromStructure(
structure, "timestamp"
)
# Try to parse the body text as key value pairs. Note that not
# all log lines will be properly formatted key value pairs.
body = self._GetValueFromStructure(structure, "body", default_value="")
body = body.strip()
try:
body_structure = self._KEY_VALUE_DICT.parse_string(body)
process_identifier = self._GetValueFromStructure(body_structure, "pid")
except pyparsing.ParseException:
process_identifier = None
event_data = SELinuxLogEventData()
event_data.audit_type = self._GetValueFromStructure(structure, "type")
event_data.body = body or None
event_data.last_written_time = self._ParseTimeElements(
time_elements_structure
)
event_data.pid = process_identifier
parser_mediator.ProduceEventData(event_data)
def _ParseTimeElements(self, time_elements_structure):
"""Parses date and time elements of a log line.
Args:
time_elements_structure (pyparsing.ParseResults): date and time elements
of a log line.
Returns:
dfdatetime.PosixTimeInMilliseconds: date and time value.
Raises:
ParseError: if a valid date and time value cannot be derived from
the time elements.
"""
try:
seconds, milliseconds = time_elements_structure
timestamp = (seconds * definitions.MILLISECONDS_PER_SECOND) + milliseconds
return dfdatetime_posix_time.PosixTimeInMilliseconds(timestamp=timestamp)
except (TypeError, ValueError) as exception:
raise errors.ParseError(
f"Unable to parse time elements with error: {exception!s}"
)
[docs]
def CheckRequiredFormat(self, parser_mediator, text_reader):
"""Check if the log record has the minimal structure required by the plugin.
Args:
parser_mediator (ParserMediator): mediates interactions between parsers
and other components, such as storage and dfVFS.
text_reader (EncodedTextReader): text reader.
Returns:
bool: True if this is the correct plugin, False otherwise.
"""
try:
structure = self._VerifyString(text_reader.lines)
except errors.ParseError:
return False
time_elements_structure = self._GetValueFromStructure(structure, "timestamp")
try:
self._ParseTimeElements(time_elements_structure)
except errors.ParseError:
return False
return True
text_parser.TextLogParser.RegisterPlugin(SELinuxTextPlugin)