"""Text parser plugin for Snort3/Suricata fast-log alert log files.

Snort3/Suricata fast.log format is a single line log format as shown below.
The following variants are known:

  Snort3:
    Month/Day-Hour:Minute:Second:FractionOfSeconds [**] [sid] "string" [**] \\
    [Classification: string] [Priority : int] {protocol} \\
    SOURCE_IP:SOURCE_PORT -> DESTINATION_IP:DESTINATION_PORT

  Suricata:
    Year/Month/Day-Hour:Minute:Second:FractionOfSeconds [**] [sid] string \\
    [**] [Classification: string] [Priority : int] {protocol} \\
    SOURCE_IP:SOURCE_PORT -> DESTINATION_IP:DESTINATION_PORT

Also see:
  https://docs.suricata.io/en/suricata-6.0.0/configuration/suricata-yaml.html#line-based-alerts-log-fast-log
"""

import pyparsing

from dfdatetime import time_elements as dfdatetime_time_elements

from plaso.containers import events
from plaso.lib import dateless_helper
from plaso.lib import errors
from plaso.parsers import text_parser
from plaso.parsers.text_plugins import interface


class SnortFastAlertEventData(events.EventData):
  """Snort3/Suricata fast-log alert event data.

  Attributes:
    classification (str): classification of the alert.
    destination_ip (str): destination IP-address.
    destination_port (int): destination TCP/UDP port number.
    last_written_time (dfdatetime.DateTimeValues): entry last written date and
        time.
    message (str): message associated with the alert.
    priority (int): priorty, ranging from 1 (high) to 4 (very low).
    rule_identifier (str): identifier of the Snort3/Suricata rule that generated
        the alert.
    source_ip (str): source IP-address.
    source_port (int): source TCP/UDP port number.
  """

  DATA_TYPE = 'snort:fastlog:alert'

  def __init__(self):
    """Initializes event data."""
    super().__init__(data_type=self.DATA_TYPE)
    self.classification = None
    self.destination_ip = None
    self.destination_port = None
    self.last_written_time = None
    self.message = None
    self.priority = None
    self.protocol = None
    self.rule_identifier = None
    self.source_ip = None
    self.source_port = None


class SnortFastLogTextPlugin(
    interface.TextPlugin, dateless_helper.DateLessLogFormatHelper):
  """Text parser plugin for Snort3/Suricata fast-log alert log files."""

  NAME = 'snort_fastlog'
  DATA_FORMAT = 'Snort3/Suricata fast-log alert log (fast.log) file'

  _INTEGER = pyparsing.Word(pyparsing.nums).set_parse_action(
      lambda tokens: int(tokens[0], 10))

  _TWO_DIGITS = pyparsing.Word(pyparsing.nums, exact=2).set_parse_action(
      lambda tokens: int(tokens[0], 10))

  _SIX_DIGITS = pyparsing.Word(pyparsing.nums, exact=6).set_parse_action(
      lambda tokens: int(tokens[0], 10))

  _DATE_MONTH_DAY = (
      _TWO_DIGITS + pyparsing.Suppress('/') + _TWO_DIGITS)

  _DATE_YEAR_MONTH_DAY = (
      _TWO_DIGITS + pyparsing.Suppress('/') + _DATE_MONTH_DAY)

  # Date and time values are formatted as: MM/DD-hh:mm:ss.###### or
  # YY/MM/DD-hh:mm:ss.######
  # For example: 12/28-12:55:38.765402 or 10/05/10-10:08:59.667372

  _DATE_TIME = (
      (_DATE_YEAR_MONTH_DAY | _DATE_MONTH_DAY) + pyparsing.Suppress('-') +
      _TWO_DIGITS + pyparsing.Suppress(':') +
      _TWO_DIGITS + pyparsing.Suppress(':') +
      _TWO_DIGITS + pyparsing.Suppress('.') + _SIX_DIGITS)

  _IP_ADDRESS = (
      pyparsing.pyparsing_common.ipv4_address |
      pyparsing.pyparsing_common.ipv6_address)

  _MESSAGE = (
      pyparsing.Optional(pyparsing.Suppress('"')) +
      pyparsing.Combine(pyparsing.OneOrMore(
          pyparsing.Word(pyparsing.printables, excludeChars='["') |
          pyparsing.White(' ', max=2))).set_results_name('message') +
      pyparsing.Optional(pyparsing.Suppress('"')))

  _RULE = (
      pyparsing.Suppress('[') +
      pyparsing.Combine(
          _INTEGER + pyparsing.Literal(':') +
          _INTEGER + pyparsing.Literal(':') +
          _INTEGER).set_results_name('rule_identifier') +
      pyparsing.Suppress(']'))

  _CLASSIFICATION = (
      pyparsing.Suppress('[Classification:') +
      pyparsing.Regex('[^]]*').set_results_name('classification') +
      pyparsing.Suppress(']'))

  _PRIORITY = (
      pyparsing.Suppress('[Priority:') +
      _INTEGER.set_results_name('priority') +
      pyparsing.Suppress(']'))

  _SOURCE_IP_ADDRESS_AND_PORT = (
      _IP_ADDRESS.set_results_name('source_ip_address') +
      pyparsing.Suppress(':') +
      _INTEGER.set_results_name('source_port'))

  _DESTINATION_IP_ADDRESS_AND_PORT = (
      _IP_ADDRESS.set_results_name('destination_ip_address') +
      pyparsing.Suppress(':') +
      _INTEGER.set_results_name('destination_port'))

  _END_OF_LINE = pyparsing.Suppress(pyparsing.LineEnd())

  _LOG_LINE = (
      _DATE_TIME.set_results_name('date_time') +
      pyparsing.Suppress('[**]') +
      _RULE +
      _MESSAGE +
      pyparsing.Suppress('[**]') +
      pyparsing.Optional(_CLASSIFICATION) +
      pyparsing.Optional(_PRIORITY) +
      pyparsing.Suppress('{') +
      pyparsing.Word(pyparsing.alphanums).set_results_name('protocol') +
      pyparsing.Suppress('}') + (
          _IP_ADDRESS.set_results_name('source_ip_address') ^
          _SOURCE_IP_ADDRESS_AND_PORT) +
      pyparsing.Suppress('->') + (
          _IP_ADDRESS.set_results_name('destination_ip_address') ^
          _DESTINATION_IP_ADDRESS_AND_PORT) +
      _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.
    """
    time_elements_structure = self._GetValueFromStructure(
        structure, 'date_time')

    event_data = SnortFastAlertEventData()
    event_data.classification = self._GetValueFromStructure(
        structure, 'classification')
    event_data.destination_ip = self._GetValueFromStructure(
        structure, 'destination_ip_address')
    event_data.destination_port = self._GetValueFromStructure(
        structure, 'destination_port')
    event_data.last_written_time = self._ParseTimeElements(
        time_elements_structure)
    event_data.message = self._GetStringValueFromStructure(
        structure, 'message')
    event_data.priority = self._GetValueFromStructure(structure, 'priority')
    event_data.protocol = self._GetValueFromStructure(structure, 'protocol')
    event_data.source_ip = self._GetValueFromStructure(
        structure, 'source_ip_address')
    event_data.source_port = self._GetValueFromStructure(
        structure, 'source_port')
    event_data.rule_identifier = self._GetValueFromStructure(
        structure, 'rule_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.TimeElements: date and time value.

    Raises:
      ParseError: if a valid date and time value cannot be derived from
          the time elements.
    """
    try:
      has_year = len(time_elements_structure) == 7

      if has_year:
        year, month, day_of_month, hours, minutes, seconds, microseconds = (
            time_elements_structure)

        year += 2000
      else:
        month, day_of_month, hours, minutes, seconds, microseconds = (
            time_elements_structure)

        self._UpdateYear(month)

        year = self._GetRelativeYear()

      time_elements_tuple = (
          year, month, day_of_month, hours, minutes, seconds, microseconds)

      date_time = dfdatetime_time_elements.TimeElementsInMicroseconds(
          is_delta=(not has_year), time_elements_tuple=time_elements_tuple)

      date_time.is_local_time = True

      return date_time

    except (IndexError, TypeError, ValueError) as exception:
      raise errors.ParseError(
          f'Unable to parse time elements with error: {exception!s}')

  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

    self._SetEstimatedYear(parser_mediator)

    time_elements_structure = self._GetValueFromStructure(
        structure, 'date_time')

    try:
      self._ParseTimeElements(time_elements_structure)
    except errors.ParseError:
      return False

    return True


text_parser.TextLogParser.RegisterPlugin(SnortFastLogTextPlugin)
