Instruction:
Implement a function in Python 3 to
extract and verifies a server message.

Response:
def DecodeMessages(self, response_comms):
    """Extract and verify server message.

    Args:
        response_comms: A ClientCommunication rdfvalue

    Returns:
       list of messages and the CN where they came from.

    Raises:
       DecryptionError: If the message failed to decrypt properly.
    """
    # Have we seen this cipher before?
    cipher_verified = False
    try:
      cipher = self.encrypted_cipher_cache.Get(response_comms.encrypted_cipher)
      stats_collector_instance.Get().IncrementCounter(
          "grr_encrypted_cipher_cache", fields=["hits"])

      # Even though we have seen this encrypted cipher already, we should still
      # make sure that all the other fields are sane and verify the HMAC.
      cipher.VerifyReceivedHMAC(response_comms)
      cipher_verified = True

      # If we have the cipher in the cache, we know the source and
      # should have a corresponding public key.
      source = cipher.GetSource()
      remote_public_key = self._GetRemotePublicKey(source)
    except KeyError:
      stats_collector_instance.Get().IncrementCounter(
          "grr_encrypted_cipher_cache", fields=["misses"])
      cipher = ReceivedCipher(response_comms, self.private_key)

      source = cipher.GetSource()
      try:
        remote_public_key = self._GetRemotePublicKey(source)
        if cipher.VerifyCipherSignature(remote_public_key):
          # At this point we know this cipher is legit, we can cache it.
          self.encrypted_cipher_cache.Put(response_comms.encrypted_cipher,
                                          cipher)
          cipher_verified = True

      except UnknownClientCertError:
        # We don't know who we are talking to.
        remote_public_key = None

    # Decrypt the message with the per packet IV.
    plain = cipher.Decrypt(response_comms.encrypted, response_comms.packet_iv)
    try:
      packed_message_list = rdf_flows.PackedMessageList.FromSerializedString(
          plain)
    except rdfvalue.DecodeError as e:
      raise DecryptionError(e)

    message_list = self.DecompressMessageList(packed_message_list)

    # Are these messages authenticated?
    # pyformat: disable
    auth_state = self.VerifyMessageSignature(
        response_comms,
        packed_message_list,
        cipher,
        cipher_verified,
        response_comms.api_version,
        remote_public_key)
    # pyformat: enable

    # Mark messages as authenticated and where they came from.
    for msg in message_list.job:
      msg.auth_state = auth_state
      msg.source = cipher.cipher_metadata.source

    return (message_list.job, cipher.cipher_metadata.source,
            packed_message_list.timestamp)


Instruction:
Implement a Python 3 function for
verifying the signature of the message list.

Response:
def VerifyMessageSignature(self, unused_response_comms, packed_message_list,
                             cipher, cipher_verified, api_version,
                             remote_public_key):
    """Verify the message list signature.

    This is the way the messages are verified in the client.

    In the client we also check that the nonce returned by the server is correct
    (the timestamp doubles as a nonce). If the nonce fails we deem the response
    unauthenticated since it might have resulted from a replay attack.

    Args:
      packed_message_list: The PackedMessageList rdfvalue from the server.
      cipher: The cipher belonging to the remote end.
      cipher_verified: If True, the cipher's signature is not verified again.
      api_version: The api version we should use.
      remote_public_key: The public key of the source.

    Returns:
      An rdf_flows.GrrMessage.AuthorizationState.

    Raises:
       DecryptionError: if the message is corrupt.
    """
    # This is not used atm since we only support a single api version (3).
    _ = api_version
    result = rdf_flows.GrrMessage.AuthorizationState.UNAUTHENTICATED

    if cipher_verified or cipher.VerifyCipherSignature(remote_public_key):
      stats_collector_instance.Get().IncrementCounter(
          "grr_authenticated_messages")
      result = rdf_flows.GrrMessage.AuthorizationState.AUTHENTICATED

    # Check for replay attacks. We expect the server to return the same
    # timestamp nonce we sent.
    if packed_message_list.timestamp != self.timestamp:  # pytype: disable=attribute-error
      result = rdf_flows.GrrMessage.AuthorizationState.UNAUTHENTICATED

    if not cipher.cipher_metadata:
      # Fake the metadata
      cipher.cipher_metadata = rdf_flows.CipherMetadata(
          source=packed_message_list.source)

    return result


Instruction:
Can you tell what is the following Python 3 function doing
def RegisterLateBindingCallback(target_name, callback, **kwargs):
  _LATE_BINDING_STORE.setdefault(target_name, []).append((callback, kwargs))

Response: Registers a callback to be invoked when the RDFValue named is declared.


Instruction:
Can you create a Python 3 function that
parses a human readable string of a byte string.

Response:
def ParseFromHumanReadable(self, string):
    """Parse a human readable string of a byte string.

    Args:
      string: The string to parse.

    Raises:
      DecodeError: If the string can not be parsed.
    """
    if not string:
      return None

    match = self.REGEX.match(string.strip().lower())
    if not match:
      raise DecodeError("Unknown specification for ByteSize %s" % string)

    multiplier = self.DIVIDERS.get(match.group(2))
    if not multiplier:
      raise DecodeError("Invalid multiplier %s" % match.group(2))

    # The value may be represented as a float, but if not dont lose accuracy.
    value = match.group(1)
    if "." in value:
      value = float(value)
    else:
      value = int(value)

    self._value = int(value * multiplier)


Instruction:
Write a Python 3 function that can
return True if the item should be dropped.

Response:
def FilterItem(self, launchditem):
    """Should this job be filtered.

    Args:
      launchditem: job NSCFDictionary
    Returns:
      True if the item should be filtered (dropped)
    """
    for regex in self.blacklist_regex:
      if regex.match(launchditem.get("Label", "")):
        return True
    return False


Instruction:
Can you tell what is the following Python 3 function doing
def Parse(self, persistence, knowledge_base, download_pathtype):
    pathspecs = []

    if isinstance(persistence, rdf_client.OSXServiceInformation):
      if persistence.program:
        pathspecs = rdf_paths.PathSpec(
            path=persistence.program, pathtype=download_pathtype)
      elif persistence.args:
        pathspecs = rdf_paths.PathSpec(
            path=persistence.args[0], pathtype=download_pathtype)

    for pathspec in pathspecs:
      yield rdf_standard.PersistenceFile(pathspec=pathspec)

Response: Parse persistence collector output.


Instruction:
Here you have a function in Python 3, explain what it does
def Trim(lst, limit):
  limit = max(0, limit)

  clipping = lst[limit:]
  del lst[limit:]
  return clipping

Response: Trims a given list so that it is not longer than given limit.


Instruction:
Can you write a function in Python 3 where it
groups items by given key function.

Response:
def Group(items, key):
  """Groups items by given key function.

  Args:
    items: An iterable or an iterator of items.
    key: A function which given each item will return the key.

  Returns:
    A dict with keys being each unique key and values being a list of items of
    that key.
  """
  result = {}

  for item in items:
    result.setdefault(key(item), []).append(item)

  return result


Instruction:
Can you tell what is the following Python 3 function doing
def Batch(items, size):
  batch = []

  for item in items:
    batch.append(item)
    if len(batch) == size:
      yield batch
      batch = []

  if batch:
    yield batch

Response: Divides items into batches of specified size.


Instruction:
Create a Python 3 function for
checking whether an iterable of items of one iterable are a prefix of another.

Response:
def StartsWith(this, that):
  """Checks whether an items of one iterable are a prefix of another.

  Args:
    this: An iterable that needs to be checked.
    that: An iterable of which items must match the prefix of `this`.

  Returns:
    `True` if `that` is a prefix of `this`, `False` otherwise.
  """
  this_iter = iter(this)
  that_iter = iter(that)

  while True:
    try:
      this_value = next(that_iter)
    except StopIteration:
      return True

    try:
      that_value = next(this_iter)
    except StopIteration:
      return False

    if this_value != that_value:
      return False


Instruction:
How would you implement a function in Python 3 that
unzips specified iterable of pairs to pair of two iterables.

Response:
def Unzip(iterable):
  """Unzips specified iterable of pairs to pair of two iterables.

  This function is an inversion of the standard `zip` function and the following
  hold:

    * ∀ l, r. l, r == unzip(zip(l, r))
    * ∀ p. p == zip(unzip(p))

  Examples:
    >>> Unzip([("foo", 1), ("bar", 2), ("baz", 3)])
    (["foo", "bar", "baz"], [1, 2, 3])

  Args:
    iterable: An iterable of pairs to unzip.

  Returns:
    A pair of iterables after unzipping.
  """
  lefts = []
  rights = []

  for left, right in iterable:
    lefts.append(left)
    rights.append(right)

  return lefts, rights


Instruction:
Write a Python 3 function that can
compute a cartesian product of dict with iterable values. This utility function, accepts a dictionary with iterable values, computes cartesian products of these values and yields dictionaries of expanded values. Examples: >>> list(DictProduct({"a": [1, 2], "b": [3, 4]})) [{"a": 1, "b": 3}, {"a": 1, "b": 4}, {"a": 2, "b": 3}, {"a": 2, "b": 4}] Args: dictionary: A dictionary with iterable values. Yields: Dictionaries with values being a result of cartesian product of values of the input dictionary.

Response:
def DictProduct(dictionary):
  """Computes a cartesian product of dict with iterable values.

  This utility function, accepts a dictionary with iterable values, computes
  cartesian products of these values and yields dictionaries of expanded values.

  Examples:
    >>> list(DictProduct({"a": [1, 2], "b": [3, 4]}))
    [{"a": 1, "b": 3}, {"a": 1, "b": 4}, {"a": 2, "b": 3}, {"a": 2, "b": 4}]

  Args:
    dictionary: A dictionary with iterable values.

  Yields:
    Dictionaries with values being a result of cartesian product of values of
    the input dictionary.
  """
  keys, values = Unzip(iteritems(dictionary))
  for product_values in itertools.product(*values):
    yield dict(zip(keys, product_values))


Instruction:
Here you have a function in Python 3, explain what it does
def AsIter(arg):
  if isinstance(arg, string_types):
    rslt = [arg]
  elif isinstance(arg, collections.Iterable):
    rslt = arg
  elif not arg:
    rslt = []
  else:
    rslt = [arg]
  return tuple(rslt)

Response: Encapsulates an argument in a tuple if it s not already iterable.


Instruction:
How would you explain what the following Python 3 function does
def _GenStates(self):
    self.GenCommentState()
    self.GenFwdState()
    self.GenQuotedState()
    self.GenCatchallState()

Response: Generate the lexer states.


Instruction:
How would you explain what the following Python 3 function does
def GenFwdState(self):
    for c in self.cont:
      self._AddToken("FWD", c, None, None)
    for s in self.sep:
      self._AddToken("FWD", s, None, None)
    self._AddToken("FWD", ".", "PushBack,PopState", None)

Response: Generates forwarding state rules.


Instruction:
Can you tell what is the following Python 3 function doing
def GenQuotedState(self):
    for i, q in enumerate(self.quot):
      label = "%s_STRING" % i
      escaped = re.escape(q)
      self._AddToken(label, escaped, "PopState", None)
      self._AddToken(label, q, "PopState", None)
      if self.ml_quote:
        self._AddToken(label, r"\n", None, None)
      else:
        self._AddToken(label, r"\n", "BadLine", None)
      self._AddToken(label, ".", "AddToField", None)

Response: Generates the string matching rules for the given quotation.


Instruction:
Make a summary of the following Python 3 code
def GenCatchallState(self):
    for c in self.comments:
      self._AddToken(".", c, "PushState,EndField", "COMMENT")
    for c in self.cont:
      self._AddToken(".", c, "PushState", "FWD")
    for t in self.term:
      self._AddToken(".", t, "EndEntry", None)
    for s in self.sep:
      self._AddToken(".", s, "EndField", None)
    for i, q in enumerate(self.quot):
      self._AddToken(".", q, "PushState", "%s_STRING" % i)
    self._AddToken(".", ".", "AddToField", None)

Response: Generates the state handlers that cover both the INITIAL and QUOTATION states.


Instruction:
Write a Python 3 script to
parse a line of the sshd config file.

Response:
def ParseLine(self, line):
    """Extracts keyword/value settings from the sshd config.

    The keyword is always the first string item.
    Values are the remainder of the string. In cases where an sshd config
    allows multiple values, these are split according to whatever separator(s)
    sshd_config permits for that value.

    Keywords and values are normalized. Keywords are converted to lowercase.
    Values are converted into integers, booleans or strings. Strings are always
    lowercased.

    Args:
      line: A line of the configuration file.
    """
    kv = line.split(None, 1)
    keyword = kv[0].lower()
    # Safely set the argument string if it wasn't found.
    values = kv[1:] or [""]
    # Then split any parameters that are actually repeated items.
    separators = self._repeated.get(keyword)
    if separators:
      repeated = []
      for v in values:
        repeated.extend(re.split(separators, v))
      # Remove empty matches.
      values = [v for v in repeated if v]

    # Now convert the values to the right types.
    if keyword in self._integers:
      values = [int(v) for v in values]
    elif keyword in self._booleans:
      values = [v.lower() in self._true for v in values]
    else:
      values = [v.lower() for v in values]
    # Only repeated arguments should be treated as a list.
    if keyword not in self._repeated:
      values = values[0]
    # Switch sections for new match blocks.
    if keyword == "match":
      self._NewMatchSection(values)
    # If it's an alias, resolve it.
    if keyword in self._aliases:
      keyword = self._aliases[keyword]
    # Add the keyword/values to the section.
    self.processor(keyword, values)


Instruction:
Here you have a function in Python 3, explain what it does
def _ParseEntry(self, key, val):
    if key in self._repeated:
      setting = self.section.setdefault(key, [])
      setting.extend(val)
    else:
      self.section.setdefault(key, val)

Response: Parses a configuration setting entry.


Instruction:
Can you generate the documentation for the following Python 3 function
def _ParseMatchGrp(self, key, val):
    if key in self._match_keywords:
      self._ParseEntry(key, val)

Response: Parses a match group parameter.


Instruction:
Can you tell what is the following Python 3 function doing
def _NewMatchSection(self, val):
    section = {"criterion": val, "config": {}}
    self.matches.append(section)
    # Now add configuration items to config section of the match block.
    self.section = section["config"]
    # Switch to a match-specific processor on a new match_block.
    self.processor = self._ParseMatchGrp

Response: Create a new configuration section for each match clause.


Instruction:
Implement a function in Python 3 to
parse the sshd configuration file.

Response:
def Parse(self, stat, file_object, knowledge_base):
    """Parse the sshd configuration.

    Process each of the lines in the configuration file.

    Assembes an sshd_config file into a dictionary with the configuration
    keyword as the key, and the configuration settings as value(s).

    Args:
      stat: unused
      file_object: An open configuration file object.
      knowledge_base: unused

    Yields:
      The configuration as an rdfvalue.
    """
    _, _ = stat, knowledge_base
    # Clean out any residual state.
    self._field_parser.Flush()
    lines = [
        l.strip()
        for l in utils.ReadFileBytesAsUnicode(file_object).splitlines()
    ]
    for line in lines:
      # Remove comments (will break if it includes a quoted/escaped #)
      line = line.split("#")[0].strip()
      if line:
        self._field_parser.ParseLine(line)
    for result in self._field_parser.GenerateResults():
      yield result


Instruction:
Implement a Python 3 function for
parsing the mount command output.

Response:
def Parse(self, cmd, args, stdout, stderr, return_val, time_taken,
            knowledge_base):
    """Parse the mount command output."""
    _ = stderr, time_taken, args, knowledge_base  # Unused.
    self.CheckReturn(cmd, return_val)
    result = rdf_protodict.AttributedDict()
    for entry in self._field_parser.ParseEntries(stdout):
      line_str = " ".join(entry)
      mount_rslt = self.mount_re.match(line_str)
      if mount_rslt:
        device, mount_point, fs_type, option_str = mount_rslt.groups()
        result = rdf_client_fs.Filesystem()
        result.device = device
        result.mount_point = mount_point
        result.type = fs_type
        # Parse these options as a dict as some items may be key/values.
        # KeyValue parser uses OrderedDict as the native parser method. Use it.
        options = KeyValueParser(term=",").ParseToOrderedDict(option_str)
        # Keys without values get assigned [] by default. Because these keys are
        # actually true, if declared, change any [] values to True.
        for k, v in iteritems(options):
          options[k] = v or [True]
        result.options = rdf_protodict.AttributedDict(**options)
        yield result


Instruction:
Here you have a function in Python 3, explain what it does
def ParseAction(self, action):
    rslt = rdf_config_file.LogTarget()
    for dst_str, dst_re in iteritems(self.destinations):
      dst = dst_re.match(action)
      if dst:
        rslt.transport = dst_str
        rslt.destination = dst.group(1)
        break
    return rslt

Response: Parses the rsyslog action string and returns a LogTarget object.


Instruction:
Can you create a Python 3 function that
parses a key value formatted source listing and return a list of potential URLs.

Response:
def ParseURIFromKeyValues(self, data, separator, uri_key):
    """Parse key/value formatted source listing and return potential URLs.

    The fundamental shape of this format is as follows:
    key: value   # here : = separator
    key : value
    URI: [URL]   # here URI = uri_key
      [URL]      # this is where it becomes trickey because [URL]
      [URL]      # can contain 'separator' specially if separator is :
    key: value

    The key uri_key is of interest to us and since the next line
    in the config could contain another [URL], we need to keep track of context
    when we hit uri_key  to be able to check if the next line(s)
    have more [URL].

    Args:
      data: unprocessed lines from a file
      separator: how the key/value pairs are seperated
      uri_key: starting name of the key containing URI.

    Returns:
      A list of potential URLs found in data
    """
    precondition.AssertType(data, Text)
    precondition.AssertType(separator, Text)

    kv_entries = KeyValueParser(kv_sep=separator).ParseEntries(data)
    spaced_entries = FieldParser().ParseEntries(data)

    uris = []
    check_uri_on_next_line = False
    for kv_entry, sp_entry in zip(kv_entries, spaced_entries):
      for k, v in iteritems(kv_entry):
        # This line could be a URL if a) from  key:value, value is empty OR
        # b) if separator is : and first character of v starts with /.
        if (check_uri_on_next_line and
            (not v or (separator == ":" and v[0].startswith("/")))):
          uris.append(sp_entry[0])
        else:
          check_uri_on_next_line = False
          if k.lower().startswith(uri_key) and v:
            check_uri_on_next_line = True
            uris.append(v[0])  # v is a list

    return uris


Instruction:
Write a Python 3 script for
giving a file this will return all potenial APT source URIs.

Response:
def FindPotentialURIs(self, file_obj):
    """Given a file, this will return all potenial APT source URIs."""
    rfc822_format = ""  # will contain all lines not in legacy format
    uris_to_parse = []

    for line in utils.ReadFileBytesAsUnicode(file_obj).splitlines(True):
      # check if legacy style line - if it is then extract URL
      m = re.search(r"^\s*deb(?:-\S+)?(?:\s+\[[^\]]*\])*\s+(\S+)(?:\s|$)", line)
      if m:
        uris_to_parse.append(m.group(1))
      else:
        rfc822_format += line

    uris_to_parse.extend(self.ParseURIFromKeyValues(rfc822_format, ":", "uri"))
    return uris_to_parse


Instruction:
Here you have a function in Python 3, explain what it does
def ParseLine(self, entries):
    # If no entries were found, short circuit.
    if not entries:
      return
    keyword = entries[0].lower()
    # Set the argument string if it wasn't found.
    values = entries[1:] or [""]

    # Convert any types we need too.
    if keyword in self._integers:
      values = [int(v) for v in values]
    if keyword in self._floats:
      values = [float(v) for v in values]

    if keyword not in self._repeated | self._duplicates:
      # We have a plain and simple single key/value config line.
      if isinstance(values[0], string_types):
        self.config[keyword] = " ".join(values)
      else:
        self.config[keyword] = values

    elif keyword in self._repeated:
      # The keyword can have multiple single-word options, so add them as a list
      # and overwrite previous settings.
      self.config[keyword] = values

    elif keyword in self._duplicates:
      if keyword in self._address_based:
        # If we have an address keyed keyword, join the keyword and address
        # together to make the complete key for this data.
        address = values[0].lower()
        values = values[1:] or [""]
        # Add/overwrite the address in this 'keyed' keywords dictionary.
        existing_keyword_config = self.keyed.setdefault(keyword, [])
        # Create a dict which stores the server name and the options.
        # Flatten the remaining options into a single string.
        existing_keyword_config.append({
            "address": address,
            "options": " ".join(values)
        })

      # Are we toggling an option?
      elif keyword in self._boolean:
        for option in values:
          if keyword == "enable":
            self.config[option] = True
          else:
            # As there are only two items in this set, we can assume disable.
            self.config[option] = False

      else:
        # We have a non-keyed & non-boolean keyword, so add to the collected
        # data so far. Order matters technically.
        prev_settings = self.config.setdefault(keyword, [])
        prev_settings.append(" ".join(values))

Response: Parses a single line of ntpd config file.


Instruction:
Write a Python 3 function for
parsing a ntp config into rdf.

Response:
def Parse(self, stat, file_object, knowledge_base):
    """Parse a ntp config into rdf."""
    _, _ = stat, knowledge_base

    # TODO(hanuszczak): This parser only allows single use because it messes
    # with its state. This should be fixed.
    field_parser = NtpdFieldParser()
    for line in field_parser.ParseEntries(
        utils.ReadFileBytesAsUnicode(file_object)):
      field_parser.ParseLine(line)

    yield rdf_config_file.NtpConfig(
        config=field_parser.config,
        server=field_parser.keyed.get("server"),
        restrict=field_parser.keyed.get("restrict"),
        fudge=field_parser.keyed.get("fudge"),
        trap=field_parser.keyed.get("trap"),
        peer=field_parser.keyed.get("peer"),
        broadcast=field_parser.keyed.get("broadcast"),
        manycastclient=field_parser.keyed.get("manycastclient"))


Instruction:
Given the following Python 3 function, write the documentation
def _ExtractList(self, fields, ignores=(",",), terminators=()):
    extracted = []
    i = 0
    for i, field in enumerate(fields):
      # Space-separated comma; ignore, but this is not a finished list.
      # Similar for any other specified ignores (eg, equals sign).
      if field in ignores:
        continue

      # However, some fields are specifically meant to terminate iteration.
      if field in terminators:
        break

      extracted.append(field.strip("".join(ignores)))
      # Check for continuation; this will either be a trailing comma or the
      # next field after this one being a comma. The lookahead here is a bit
      # nasty.
      if not (field.endswith(",") or
              set(fields[i + 1:i + 2]).intersection(ignores)):
        break

    return extracted, fields[i + 1:]

Response: Extracts a list from the given fields.


Instruction:
Can you generate the documentation for the following Python 3 function
def ParseSudoersEntry(self, entry, sudoers_config):

    key = entry[0]
    if key in SudoersFieldParser.ALIAS_TYPES:
      # Alias.
      alias_entry = rdf_config_file.SudoersAlias(
          type=SudoersFieldParser.ALIAS_TYPES.get(key), name=entry[1])

      # Members of this alias, comma-separated.
      members, _ = self._ExtractList(entry[2:], ignores=(",", "="))
      field = SudoersFieldParser.ALIAS_FIELDS.get(key)
      getattr(alias_entry, field).Extend(members)

      sudoers_config.aliases.append(alias_entry)
    elif key.startswith(SudoersFieldParser.DEFAULTS_KEY):
      # Default.
      # Identify scope if one exists (Defaults<scope> ...)
      scope = None
      if len(key) > len(SudoersFieldParser.DEFAULTS_KEY):
        scope = key[len(SudoersFieldParser.DEFAULTS_KEY) + 1:]

      # There can be multiple defaults on a line, for the one scope.
      entry = entry[1:]
      defaults, _ = self._ExtractList(entry)
      for default in defaults:
        default_entry = rdf_config_file.SudoersDefault(scope=scope)

        # Extract key name and value(s).
        default_name = default
        value = []
        if "=" in default_name:
          default_name, remainder = default_name.split("=", 1)
          value = [remainder]
        default_entry.name = default_name
        if entry:
          default_entry.value = " ".join(value)

        sudoers_config.defaults.append(default_entry)
    elif key in SudoersFieldParser.INCLUDE_KEYS:
      # TODO(user): make #includedir more obvious in the RDFValue somewhere
      target = " ".join(entry[1:])
      sudoers_config.includes.append(target)
    else:
      users, entry = self._ExtractList(entry)
      hosts, entry = self._ExtractList(entry, terminators=("=",))

      # Remove = from <user> <host> = <specs>
      if entry[0] == "=":
        entry = entry[1:]

      # Command specification.
      sudoers_entry = rdf_config_file.SudoersEntry(
          users=users, hosts=hosts, cmdspec=entry)

      sudoers_config.entries.append(sudoers_entry)

Response: Parses an entry and adds it to the given SudoersConfig rdfvalue.


Instruction:
Make a summary of the following Python 3 code
def Preprocess(self, data):
    # Add whitespace to line continuations.
    data = data.replace(":\\", ": \\")

    # Strip comments manually because sudoers has multiple meanings for '#'.
    data = SudoersFieldParser.COMMENTS_RE.sub("", data)
    return data

Response: Preprocess the given data ready for parsing.


Instruction:
Can you create a Python 3 function that
validates an RDFValue instance.

Response:
def Validate(self, value):
    """Validate an RDFValue instance.

    Args:
      value: An RDFValue instance or something which may be used to instantiate
        the correct instance.

    Raises:
      TypeValueError: If the value is not a valid RDFValue instance or the
        required type.

    Returns:
      A Valid RDFValue instance.
    """
    # Allow None as a default.
    if value is None:
      return

    if not isinstance(value, self.rdfclass):
      # Try to coerce the type to the correct rdf_class.
      try:
        return self.rdfclass(value)
      except rdfvalue.InitializeError:
        raise TypeValueError("Value for arg %s should be an %s" %
                             (self.name, self.rdfclass.__name__))

    return value


Instruction:
How would you implement a function in Python 3 that
validates the value. Args: value: Value is expected to be a dict-like object that a given RDFStruct can be initialized from. Raises: TypeValueError: If the value is not a valid dict-like object that a given RDFStruct can be initialized from. Returns: A valid instance of self.rdfclass or None.

Response:
def Validate(self, value):
    """Validate the value.

    Args:
      value: Value is expected to be a dict-like object that a given RDFStruct
        can be initialized from.

    Raises:
      TypeValueError: If the value is not a valid dict-like object that a given
        RDFStruct can be initialized from.

    Returns:
      A valid instance of self.rdfclass or None.
    """
    if value is None:
      return None

    if not isinstance(value, self.rdfclass):
      # Try to coerce the type to the correct rdf_class.
      try:
        r = self.rdfclass()
        r.FromDict(value)
        return r
      except (AttributeError, TypeError, rdfvalue.InitializeError):
        # AttributeError is raised if value contains items that don't
        # belong to the given rdfstruct.
        # TypeError will be raised if value is not a dict-like object.
        raise TypeValueError("Value for arg %s should be an %s" %
                             (self.name, self.rdfclass.__name__))

    return value


Instruction:
Write a Python 3 script to
return a copy of this set with a new element added.

Response:
def Add(self, other):
    """Returns a copy of this set with a new element added."""
    new_descriptors = []
    for desc in self.descriptors + other.descriptors:
      if desc not in new_descriptors:
        new_descriptors.append(desc)

    return TypeDescriptorSet(*new_descriptors)


Instruction:
Write a Python 3 function that can
append the descriptor to this set.

Response:
def Append(self, desc):
    """Append the descriptor to this set."""
    if desc not in self.descriptors:
      self.descriptors.append(desc)
      self.descriptor_map[desc.name] = desc
      self.descriptor_names.append(desc.name)


Instruction:
Can you write a function in Python 3 where it
returns a copy of this set without elements with given names.

Response:
def Remove(self, *descriptor_names):
    """Returns a copy of this set without elements with given names."""
    new_descriptor_map = self.descriptor_map.copy()
    for name in descriptor_names:
      new_descriptor_map.pop(name, None)

    new_descriptors = [
        desc for desc in self.descriptors
        if desc in itervalues(new_descriptor_map)
    ]
    return TypeDescriptorSet(*new_descriptors)


Instruction:
Can you create a Python 3 function that
parses and validate the args.

Response:
def ParseArgs(self, args):
    """Parse and validate the args.

    Note we pop all the args we consume here - so if there are any args we dont
    know about, args will not be an empty dict after this. This allows the same
    args to be parsed by several TypeDescriptorSets.

    Args:
      args: A dictionary of arguments that this TypeDescriptorSet might use. If
        this dict does not have a required parameter, we still yield its default
        value.

    Yields:
      A (name, value) tuple of the parsed args.
    """
    for descriptor in self:
      # Get the value from the kwargs or, if not specified, the default.
      value = args.pop(descriptor.name, None)

      if value is None:
        # No need to validate the default value.
        value = descriptor.default
      else:
        try:
          # Validate this value - this should raise if the value provided is not
          # acceptable to the type descriptor.
          value = descriptor.Validate(value)
        except Exception:
          logging.error("Invalid value %s for arg %s", value, descriptor.name)
          raise

      yield descriptor.name, value


Instruction:
Implement a function in Python 3 to
parse a bool from a string.

Response:
def FromString(self, string):
    """Parse a bool from a string."""
    if string.lower() in ("false", "no", "n"):
      return False

    if string.lower() in ("true", "yes", "y"):
      return True

    raise TypeValueError("%s is not recognized as a boolean value." % string)


Instruction:
Create a Python 3 function to
validate a potential list.

Response:
def Validate(self, value):
    """Validate a potential list."""
    if isinstance(value, string_types):
      raise TypeValueError("Value must be an iterable not a string.")

    elif not isinstance(value, (list, tuple)):
      raise TypeValueError("%r not a valid List" % value)

    # Validate each value in the list validates against our type.
    return [self.validator.Validate(val) for val in value]


Instruction:
Can you generate the documentation for the following Python 3 function
def Register():
  # pyformat: disable

  # Command parsers.
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Dpkg", linux_cmd_parser.DpkgCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Dmidecode", linux_cmd_parser.DmidecodeCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Mount", config_file.MountCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "OsxSpHardware", osx_file_parser.OSXSPHardwareDataTypeParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Ps", linux_cmd_parser.PsCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Rpm", linux_cmd_parser.RpmCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "SshdConfig", config_file.SshdConfigCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Sysctl", linux_sysctl_parser.SysctlCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "YumList", linux_cmd_parser.YumListCmdParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "YumRepolist", linux_cmd_parser.YumRepolistCmdParser)

  # Grep parsers.
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Passwd", linux_file_parser.PasswdBufferParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "Netgroup", linux_file_parser.NetgroupBufferParser)

  # WMI query parsers.
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiEventConsumer", wmi_parser.WMIEventConsumerParser)
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiInstalledSoftware", wmi_parser.WMIInstalledSoftwareParser)
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiHotfixesSoftware", wmi_parser.WMIHotfixesSoftwareParser)
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiUser", wmi_parser.WMIUserParser)
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiLogicalDisks", wmi_parser.WMILogicalDisksParser)
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiCsp", wmi_parser.WMIComputerSystemProductParser)
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WmiInterfaces", wmi_parser.WMIInterfacesParser)

  # Registry value parsers.
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinCcs", windows_registry_parser.CurrentControlSetKBParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinCodepage", windows_registry_parser.CodepageParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinEnvironment", windows_registry_parser.WinEnvironmentParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinServices", windows_registry_parser.WinServicesParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinSystemDrive", windows_registry_parser.WinSystemDriveParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinSystemRoot", windows_registry_parser.WinSystemRootParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinTimezone", windows_registry_parser.WinTimezoneParser)

  # Registry parsers.
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinAllUsersProfileEnvVar",
      windows_registry_parser.AllUsersProfileEnvironmentVariable)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinProfileDirEnvVar",
      windows_registry_parser.ProfilesDirectoryEnvironmentVariable)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WinUserSids",
      windows_registry_parser.WinUserSids)

  # Artifact file parsers.
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "DarwinPersistenceMechanism",
      osx_launchd.DarwinPersistenceMechanismsParser)
  parsers.SINGLE_RESPONSE_PARSER_FACTORY.Register(
      "WindowsPersistenceMechanism",
      windows_persistence.WindowsPersistenceMechanismsParser)

  # Registry multi-parsers.
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "WinUserSpecialDirs", windows_registry_parser.WinUserSpecialDirs)

  # Artifact file multi-parsers.
  parsers.MULTI_RESPONSE_PARSER_FACTORY.Register(
      "OsxUsers", osx_file_parser.OSXUsersParser)

  # File parsers.
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "ChromeHistory", chrome_history.ChromeHistoryParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "CronAtAllAllowDeny", config_file.CronAtAllowDenyParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "CronTab", cron_file_parser.CronTabParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "FirefoxHistory", firefox3_history.FirefoxHistoryParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "IeHistory", ie_history.IEHistoryParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "LinuxWtmp", linux_file_parser.LinuxWtmpParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "Mtab", config_file.MtabParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "Netgroup", linux_file_parser.NetgroupParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "NfsExports", config_file.NfsExportsParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "Ntpd", config_file.NtpdParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "PackageSource", config_file.PackageSourceParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "Passwd", linux_file_parser.PasswdParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "Path", linux_file_parser.PathParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "SshdConfigFile", config_file.SshdConfigParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "Sudoers", config_file.SudoersParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "OsxLaunchdPlist", osx_file_parser.OSXLaunchdPlistParser)
  parsers.SINGLE_FILE_PARSER_FACTORY.Register(
      "OSXInstallHistoryPlist", osx_file_parser.OSXInstallHistoryPlistParser)

  try:
    from debian import deb822  # pylint: disable=g-import-not-at-top
    parsers.SINGLE_FILE_PARSER_FACTORY.Register(
        "DpkgStatusParser",
        lambda: linux_software_parser.DebianPackagesStatusParser(deb822))
  except ImportError:
    pass

  # File multi-parsers.
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "LinuxBaseShadow", linux_file_parser.LinuxBaseShadowParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "LinuxLsbInit", linux_service_parser.LinuxLSBInitParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "LinuxXinetd", linux_service_parser.LinuxXinetdParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "LinuxSysvInit", linux_service_parser.LinuxSysVInitParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "LinuxPam", linux_pam_parser.PAMParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "LinuxReleaseInfo", linux_release_parser.LinuxReleaseParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "PciDevicesInfo", linux_file_parser.PCIDevicesInfoParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "ProcSys", linux_sysctl_parser.ProcSysParser)
  parsers.MULTI_FILE_PARSER_FACTORY.Register(
      "Rsyslog", config_file.RsyslogParser)

Response: Registers all known command parsers to the registry.


Instruction:
Write a Python 3 function for
returning the rdfurn of the current audit log.

Response:
def _CurrentAuditLog():
  """Get the rdfurn of the current audit log."""
  now_sec = rdfvalue.RDFDatetime.Now().AsSecondsSinceEpoch()
  rollover_seconds = AUDIT_ROLLOVER_TIME.seconds
  # This gives us a filename that only changes every
  # AUDIT_ROLLOVER_TIfilME seconds, but is still a valid timestamp.
  current_log = (now_sec // rollover_seconds) * rollover_seconds
  return _AuditLogBase().Add(str(current_log))


Instruction:
Here you have a function in Python 3, explain what it does
def UnicodeFromCodePage(string):
  # get the current code page
  codepage = ctypes.windll.kernel32.GetOEMCP()
  try:
    return string.decode("cp%s" % codepage)
  except UnicodeError:
    try:
      return string.decode("utf16", "ignore")
    except UnicodeError:
      # Fall back on utf8 but ignore errors
      return string.decode("utf8", "ignore")

Response: Attempt to coerce string into a unicode object.


Instruction:
Write a Python 3 script for
enumerating all interfaces from the client.

Response:
def EnumerateInterfacesFromClient(args):
  """Enumerate all MAC addresses of all NICs.

  Args:
    args: Unused.

  Yields:
    `rdf_client_network.Interface` instances.
  """
  del args  # Unused.

  pythoncom.CoInitialize()
  for interface in (wmi.WMI().Win32_NetworkAdapterConfiguration() or []):
    addresses = []
    for ip_address in interface.IPAddress or []:
      addresses.append(
          rdf_client_network.NetworkAddress(human_readable_address=ip_address))

    response = rdf_client_network.Interface(ifname=interface.Description)
    if interface.MACAddress:
      response.mac_address = binascii.unhexlify(
          interface.MACAddress.replace(":", ""))
    if addresses:
      response.addresses = addresses

    yield response


Instruction:
Create a Python 3 function for
enumerating all local filesystems mounted on this system.

Response:
def EnumerateFilesystemsFromClient(args):
  """List all local filesystems mounted on this system."""
  del args  # Unused.
  for drive in win32api.GetLogicalDriveStrings().split("\x00"):
    if not drive:
      continue
    try:
      volume = win32file.GetVolumeNameForVolumeMountPoint(drive).rstrip("\\")

      label, _, _, _, fs_type = win32api.GetVolumeInformation(drive)
    except win32api.error:
      continue
    yield rdf_client_fs.Filesystem(
        device=volume,
        mount_point="/%s:/" % drive[0],
        type=fs_type,
        label=UnicodeFromCodePage(label))


Instruction:
How would you explain what the following Python 3 function does
def QueryService(svc_name):
  hscm = win32service.OpenSCManager(None, None,
                                    win32service.SC_MANAGER_ALL_ACCESS)
  result = None
  try:
    hs = win32serviceutil.SmartOpenService(hscm, svc_name,
                                           win32service.SERVICE_ALL_ACCESS)
    result = win32service.QueryServiceConfig(hs)
    win32service.CloseServiceHandle(hs)
  finally:
    win32service.CloseServiceHandle(hscm)

  return result

Response: Query service and get its config.


Instruction:
Write a Python 3 function for
running the WMI query and return the data.

Response:
def WmiQueryFromClient(args):
  """Run the WMI query and return the data."""
  query = args.query
  base_object = args.base_object or r"winmgmts:\root\cimv2"

  if not query.upper().startswith("SELECT "):
    raise RuntimeError("Only SELECT WMI queries allowed.")

  for response_dict in RunWMIQuery(query, baseobj=base_object):
    yield response_dict


Instruction:
How would you explain what the following Python 3 function does
def RunWMIQuery(query, baseobj=r"winmgmts:\root\cimv2"):
  pythoncom.CoInitialize()  # Needs to be called if using com from a thread.
  wmi_obj = win32com.client.GetObject(baseobj)
  # This allows our WMI to do some extra things, in particular
  # it gives it access to find the executable path for all processes.
  wmi_obj.Security_.Privileges.AddAsString("SeDebugPrivilege")

  # Run query
  try:
    query_results = wmi_obj.ExecQuery(query)
  except pythoncom.com_error as e:
    raise RuntimeError("Failed to run WMI query \'%s\' err was %s" % (query, e))

  # Extract results from the returned COMObject and return dicts.
  try:
    for result in query_results:
      response = rdf_protodict.Dict()
      properties = (
          list(result.Properties_) +
          list(getattr(result, "SystemProperties_", [])))

      for prop in properties:
        if prop.Name not in IGNORE_PROPS:
          # Protodict can handle most of the types we care about, but we may
          # get some objects that we don't know how to serialize, so we tell the
          # dict to set the value to an error message and keep going
          response.SetItem(prop.Name, prop.Value, raise_on_error=False)
      yield response

  except pythoncom.com_error as e:
    raise RuntimeError("WMI query data error on query \'%s\' err was %s" %
                       (e, query))

Response: Run a WMI query and return a result.


Instruction:
Can you generate the documentation for the following Python 3 function
def Run(self, unused_args):
    # Don't use winreg.KEY_WOW64_64KEY since it breaks on Windows 2000
    subkey = winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE,
                            "Software\\Microsoft\\Windows NT\\CurrentVersion",
                            0, winreg.KEY_READ)
    install_date = winreg.QueryValueEx(subkey, "InstallDate")
    self.SendReply(rdfvalue.RDFDatetime.FromSecondsSinceEpoch(install_date[0]))

Response: Estimate the install date of this system.


Instruction:
Can you generate a brief explanation for the following Python 3 code
def Run(self, unused_arg):
    logging.debug("Disabling service")

    win32serviceutil.ChangeServiceConfig(
        None,
        config.CONFIG["Nanny.service_name"],
        startType=win32service.SERVICE_DISABLED)
    svc_config = QueryService(config.CONFIG["Nanny.service_name"])
    if svc_config[1] == win32service.SERVICE_DISABLED:
      logging.info("Disabled service successfully")
      self.SendReply(rdf_protodict.DataBlob(string="Service disabled."))
    else:
      self.SendReply(
          rdf_protodict.DataBlob(string="Service failed to disable."))

Response: This kills us with no cleanups.


Instruction:
Here you have a function in Python 3, explain what it does
def OpenKey(key, sub_key):
  regopenkeyex = advapi32["RegOpenKeyExW"]
  regopenkeyex.restype = ctypes.c_long
  regopenkeyex.argtypes = [
      ctypes.c_void_p, ctypes.c_wchar_p, ctypes.c_ulong, ctypes.c_ulong,
      ctypes.POINTER(ctypes.c_void_p)
  ]

  new_key = KeyHandle()
  # Don't use KEY_WOW64_64KEY (0x100) since it breaks on Windows 2000
  rc = regopenkeyex(
      key.handle, sub_key, 0, KEY_READ,
      ctypes.cast(
          ctypes.byref(new_key.handle), ctypes.POINTER(ctypes.c_void_p)))
  if rc != ERROR_SUCCESS:
    raise ctypes.WinError(2)

  return new_key

Response: This calls the Windows OpenKeyEx function in a Unicode safe way.


Instruction:
Implement a function in Python 3 to
convert a Windows Registry value to the corresponding Python data type.

Response:
def _Reg2Py(data, size, data_type):
  """Converts a Windows Registry value to the corresponding Python data type."""
  if data_type == winreg.REG_DWORD:
    if size == 0:
      return 0
    # DWORD is an unsigned 32-bit integer, see:
    # https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-dtyp/262627d8-3418-4627-9218-4ffe110850b2
    return ctypes.cast(data, ctypes.POINTER(ctypes.c_uint32)).contents.value
  elif data_type == winreg.REG_SZ or data_type == winreg.REG_EXPAND_SZ:
    return ctypes.wstring_at(data, size // 2).rstrip(u"\x00")
  elif data_type == winreg.REG_MULTI_SZ:
    return ctypes.wstring_at(data, size // 2).rstrip(u"\x00").split(u"\x00")
  else:
    if size == 0:
      return None
    return ctypes.string_at(data, size)


Instruction:
How would you code a function in Python 3 to
list the names of all keys and values.

Response:
def ListNames(self):
    """List the names of all keys and values."""

    # TODO: This check is flawed, because the current definition of
    # "IsDirectory" is the negation of "is a file". One registry path can
    # actually refer to a key ("directory"), a value of the same name ("file")
    # and the default value of the key at the same time.
    if not self.IsDirectory():
      return

    # Handle the special case where no hive is specified and just list the hives
    if self.hive is None:
      for name in dir(winreg):
        if name.startswith("HKEY_"):
          yield name

      return

    try:
      with OpenKey(self.hive, self.local_path) as key:
        (self.number_of_keys, self.number_of_values,
         self.last_modified) = QueryInfoKey(key)

        found_keys = set()

        # First keys
        for i in range(self.number_of_keys):
          try:
            key_name = EnumKey(key, i)
            found_keys.add(key_name)
            yield key_name
          except OSError:
            pass

        # Now Values
        for i in range(self.number_of_values):
          try:
            name, unused_value, unused_value_type = EnumValue(key, i)

            # A key might contain a sub-key and value of the same name. Do not
            # yield the same name twice in this case. With only the name,
            # the caller cannot differentiate between a key and a value anyway.
            if name not in found_keys:
              yield name
          except OSError:
            pass

    except OSError as e:
      raise IOError("Unable to list key %s: %s" % (self.key_name, e))


Instruction:
Explain what the following Python 3 code does
def CreateAFF4Object(stat_response, client_id_urn, mutation_pool, token=None):

  urn = stat_response.pathspec.AFF4Path(client_id_urn)

  if stat.S_ISDIR(stat_response.st_mode):
    ftype = standard.VFSDirectory
  else:
    ftype = aff4_grr.VFSFile

  with aff4.FACTORY.Create(
      urn, ftype, mode="w", mutation_pool=mutation_pool, token=token) as fd:
    fd.Set(fd.Schema.STAT(stat_response))
    fd.Set(fd.Schema.PATHSPEC(stat_response.pathspec))

Response: This creates a File or a Directory from a stat response.


Instruction:
Create a Python 3 function to
filter out duplicates from passed PathInfo objects.

Response:
def _FilterOutPathInfoDuplicates(path_infos):
  """Filters out duplicates from passed PathInfo objects.

  Args:
    path_infos: An iterable with PathInfo objects.

  Returns:
    A list of PathInfo objects with duplicates removed. Duplicates are
    removed following this logic: they're sorted by (ctime, mtime, atime,
    inode number) in the descending order and then the first one is taken
    and the others are dropped.
  """
  pi_dict = {}

  for pi in path_infos:
    path_key = (pi.path_type, pi.GetPathID())
    pi_dict.setdefault(path_key, []).append(pi)

  def _SortKey(pi):
    return (
        pi.stat_entry.st_ctime,
        pi.stat_entry.st_mtime,
        pi.stat_entry.st_atime,
        pi.stat_entry.st_ino,
    )

  for pi_values in pi_dict.values():
    if len(pi_values) > 1:
      pi_values.sort(key=_SortKey, reverse=True)

  return [v[0] for v in pi_dict.values()]


Instruction:
Here you have a function in Python 3, explain what it does
def WriteStatEntries(stat_entries, client_id, mutation_pool, token=None):

  for stat_response in stat_entries:
    if stat_response.pathspec.last.stream_name:
      # This is an ads. In that case we always need to create a file or
      # we won't be able to access the data. New clients send the correct mode
      # already but to make sure, we set this to a regular file anyways.
      # Clear all file type bits:
      stat_response.st_mode &= ~stat_type_mask
      stat_response.st_mode |= stat.S_IFREG

  if data_store.AFF4Enabled():
    for stat_entry in stat_entries:
      CreateAFF4Object(
          stat_entry,
          client_id_urn=rdf_client.ClientURN(client_id),
          mutation_pool=mutation_pool,
          token=token)

  if data_store.RelationalDBEnabled():
    path_infos = [rdf_objects.PathInfo.FromStatEntry(s) for s in stat_entries]
    # NOTE: TSK may return duplicate entries. This is may be either due to
    # a bug in TSK implementation, or due to the fact that TSK is capable
    # of returning deleted files information. Our VFS data model only supports
    # storing multiple versions of the files when we collect the versions
    # ourselves. At the moment we can't store multiple versions of the files
    # "as returned by TSK".
    #
    # Current behaviour is to simply drop excessive version before the
    # WritePathInfo call. This way files returned by TSK will still make it
    # into the flow's results, but not into the VFS data.
    data_store.REL_DB.WritePathInfos(client_id,
                                     _FilterOutPathInfoDuplicates(path_infos))

Response: Writes stat entries into the AFF4 data store.


Instruction:
How would you code a function in Python 3 to
start the Glob. This is the main entry point for this flow mixin. First we convert the pattern into regex components, and then we interpolate each component. Finally, we generate a cartesian product of all combinations. Args: paths: A list of GlobExpression instances. pathtype: The pathtype to use for creating pathspecs. root_path: A pathspec where to start searching from. process_non_regular_files: Work with all kinds of files - not only with regular ones. collect_ext_attrs: Whether to gather information about file extended attributes.

Response:
def GlobForPaths(self,
                   paths,
                   pathtype="OS",
                   root_path=None,
                   process_non_regular_files=False,
                   collect_ext_attrs=False):
    """Starts the Glob.

    This is the main entry point for this flow mixin.

    First we convert the pattern into regex components, and then we
    interpolate each component. Finally, we generate a cartesian product of all
    combinations.

    Args:
      paths: A list of GlobExpression instances.
      pathtype: The pathtype to use for creating pathspecs.
      root_path: A pathspec where to start searching from.
      process_non_regular_files: Work with all kinds of files - not only with
        regular ones.
      collect_ext_attrs: Whether to gather information about file extended
        attributes.
    """
    patterns = []

    if not paths:
      # Nothing to do.
      return

    self.state.pathtype = pathtype
    self.state.root_path = root_path
    self.state.process_non_regular_files = process_non_regular_files
    self.state.collect_ext_attrs = collect_ext_attrs

    # Transform the patterns by substitution of client attributes. When the
    # client has multiple values for an attribute, this generates multiple
    # copies of the pattern, one for each variation. e.g.:
    # /home/%%Usernames%%/* -> [ /home/user1/*, /home/user2/* ]
    for path in paths:
      patterns.extend(
          path.Interpolate(knowledge_base=self.client_knowledge_base))

    # Sort the patterns so that if there are files whose paths conflict with
    # directory paths, the files get handled after the conflicting directories
    # have been added to the component tree.
    patterns.sort(key=len, reverse=True)

    # Expand each glob pattern into a list of components. A component is either
    # a wildcard or a literal component.
    # e.g. /usr/lib/*.exe -> ['/usr/lib', '.*.exe']

    # We build a tree for each component such that duplicated components are
    # merged. We do not need to reissue the same client requests for the same
    # components. For example, the patterns:
    # '/home/%%Usernames%%*' -> {'/home/': {
    #      'syslog.*\\Z(?ms)': {}, 'test.*\\Z(?ms)': {}}}
    # Note: The component tree contains serialized pathspecs in dicts.
    for pattern in patterns:
      # The root node.
      curr_node = self.state.component_tree

      components = self.ConvertGlobIntoPathComponents(pattern)
      for i, curr_component in enumerate(components):
        is_last_component = i == len(components) - 1
        next_node = curr_node.get(curr_component.SerializeToString(), {})
        if is_last_component and next_node:
          # There is a conflicting directory already existing in the tree.
          # Replace the directory node with a node representing this file.
          curr_node[curr_component.SerializeToString()] = {}
        else:
          curr_node = curr_node.setdefault(curr_component.SerializeToString(),
                                           {})

    root_path = next(iterkeys(self.state.component_tree))
    self.CallStateInline(
        messages=[None],
        next_state="ProcessEntry",
        request_data=dict(component_path=[root_path]))


Instruction:
Make a summary of the following Python 3 code
def GlobReportMatch(self, stat_response):
    # By default write the stat_response to the AFF4 VFS.
    with data_store.DB.GetMutationPool() as pool:
      WriteStatEntries([stat_response],
                       client_id=self.client_id,
                       mutation_pool=pool,
                       token=self.token)

Response: Called when we have found a match a StatEntry.


Instruction:
How would you explain what the following Python 3 function does
def FindNode(self, component_path):
    # Find the node that the component path is referring to.
    node = self.state.component_tree
    for component in component_path:
      node = node[component]

    return node

Response: Find the node in the component tree from component_path.


Instruction:
Make a summary of the following Python 3 code
def _MatchPath(self, pathspec, response):
    to_match = response.pathspec.Basename()
    if pathspec.path_options == rdf_paths.PathSpec.Options.CASE_INSENSITIVE:
      return to_match.lower() == pathspec.path.lower()
    elif pathspec.path_options == rdf_paths.PathSpec.Options.CASE_LITERAL:
      return to_match == pathspec.path
    elif pathspec.path_options == rdf_paths.PathSpec.Options.REGEX:
      return bool(re.match(pathspec.path, to_match, flags=re.IGNORECASE))
    elif pathspec.path_options == rdf_paths.PathSpec.Options.RECURSIVE:
      return True
    raise ValueError("Unknown Pathspec type.")

Response: Returns True if the responses match the pathspec.


Instruction:
How would you explain what the following Python 3 function does
def ProcessEntry(self, responses):
    if not responses.success:
      return

    # The Find client action does not return a StatEntry but a
    # FindSpec. Normalize to a StatEntry.
    stat_responses = [
        r.hit if isinstance(r, rdf_client_fs.FindSpec) else r for r in responses
    ]

    # If this was a pure path matching call without any regex / recursion, we
    # know exactly which node in the component tree we have to process next and
    # get it from the component_path. If this was a regex match though, we
    # sent the client a combined regex that matches all nodes in order to save
    # round trips and client processing time. In that case we only get the
    # base node and have to check for all subnodes if the response actually
    # matches that subnode before we continue processing.
    component_path = responses.request_data.get("component_path")
    if component_path is not None:

      for response in stat_responses:
        self._ProcessResponse(response, [component_path])

    else:
      # This is a combined match.
      base_path = responses.request_data["base_path"]
      base_node = self.FindNode(base_path)
      for response in stat_responses:
        matching_components = []
        for next_node in base_node:
          pathspec = rdf_paths.PathSpec.FromSerializedString(next_node)

          if self._MatchPath(pathspec, response):
            matching_path = base_path + [next_node]
            matching_components.append(matching_path)

        if matching_components:
          self._ProcessResponse(
              response, matching_components, base_wildcard=True)

Response: Processes the responses from the client.


Instruction:
Implement a function in Python 3 to
query the database file.

Response:
def Query(self, sql_query):
    """Query the database file."""
    results = {}

    try:
      self._connection = sqlite.connect(self.name)
      self._connection.execute("PRAGMA journal_mode=%s" % self.journal_mode)
      self._cursor = self._connection.cursor()
      results = self._cursor.execute(sql_query).fetchall()

    except sqlite.Error as error_string:
      logging.warning("SQLite error %s", error_string)

    return results


Instruction:
Can you tell what is the following Python 3 function doing
def GetClientURNsForHostnames(hostnames, token=None):

  if data_store.RelationalDBEnabled():
    index = ClientIndex()
  else:
    index = CreateClientIndex(token=token)

  keywords = set()
  for hostname in hostnames:
    if hostname.startswith("host:"):
      keywords.add(hostname)
    else:
      keywords.add("host:%s" % hostname)
  results = index.ReadClientPostingLists(keywords)

  result = {}
  for keyword, hits in iteritems(results):
    result[keyword[len("host:"):]] = hits
  return result

Response: Gets all GRR client_ids for a given list of hostnames or FQDNs.


Instruction:
Given the following Python 3 function, write the documentation
def GetMostRecentClient(client_list, token=None):
  last = rdfvalue.RDFDatetime(0)
  client_urn = None
  for client in aff4.FACTORY.MultiOpen(client_list, token=token):
    client_last = client.Get(client.Schema.LAST)
    if client_last > last:
      last = client_last
      client_urn = client.urn
  return client_urn

Response: Returns the urn of the most recent client from a list of clients.


Instruction:
Can you generate the documentation for the following Python 3 function
def BulkLabel(label, hostnames, owner=None, token=None, client_index=None):
  if client_index is None:
    client_index = CreateClientIndex(token=token)

  fqdns = set()
  for hostname in hostnames:
    fqdns.add(hostname.lower())

  labelled_urns = client_index.LookupClients(["+label:%s" % label])

  # If a labelled client fqdn isn't in the set of target fqdns remove the label.
  # Labelled clients with a target fqdn need no action and are removed from the
  # set of target fqdns.
  for client in aff4.FACTORY.MultiOpen(
      labelled_urns, token=token, aff4_type=aff4_grr.VFSGRRClient, mode="rw"):
    fqdn = utils.SmartStr(client.Get("FQDN")).lower()
    if fqdn not in fqdns:
      client_index.RemoveClientLabels(client)
      client.RemoveLabel(label, owner=owner)
      client.Flush()
      client_index.AddClient(client)
    else:
      fqdns.discard(fqdn)

  # The residual set of fqdns needs labelling.
  # Get the latest URN for these clients and open them to add the label.
  urns = []
  keywords = ["+host:%s" % fqdn for fqdn in fqdns]
  for client_list in client_index.ReadClientPostingLists(keywords).itervalues():
    for client_id in client_list:
      urns.append(rdfvalue.RDFURN(client_id))

  for client in aff4.FACTORY.MultiOpen(
      urns, token=token, aff4_type=aff4_grr.VFSGRRClient, mode="rw"):
    client.AddLabel(label, owner=owner)
    client.Flush()
    client_index.AddClient(client)

Response: Assign a label to a group of clients based on hostname.


Instruction:
Implement a Python 3 function for
searching for clients associated with keywords.

Response:
def LookupClients(self, keywords):
    """Returns a list of client URNs associated with keywords.

    Args:
      keywords: The list of keywords to search by.

    Returns:
      A list of client URNs.

    Raises:
      ValueError: A string (single keyword) was passed instead of an iterable.
    """
    if isinstance(keywords, string_types):
      raise ValueError(
          "Keywords should be an iterable, not a string (got %s)." % keywords)

    start_time, end_time, filtered_keywords, unversioned_keywords = (
        self._AnalyzeKeywords(keywords))

    last_seen_map = None
    if unversioned_keywords:
      last_seen_map = {}

    # TODO(user): Make keyword index datetime aware so that
    # AsMicrosecondsSinceEpoch is unnecessary.

    raw_results = self.Lookup(
        list(map(self._NormalizeKeyword, filtered_keywords)),
        start_time=start_time.AsMicrosecondsSinceEpoch(),
        end_time=end_time.AsMicrosecondsSinceEpoch(),
        last_seen_map=last_seen_map)
    if not raw_results:
      return []

    if unversioned_keywords:
      universal_last_seen_raw = {}
      self.ReadPostingLists(
          list(map(self._NormalizeKeyword, raw_results)),
          start_time=start_time.AsMicrosecondsSinceEpoch(),
          end_time=end_time.AsMicrosecondsSinceEpoch(),
          last_seen_map=universal_last_seen_raw)

      universal_last_seen = {}
      for (_, client_id), ts in iteritems(universal_last_seen_raw):
        universal_last_seen[client_id] = ts

      old_results = set()
      for keyword in unversioned_keywords:
        for result in raw_results:
          if last_seen_map[(keyword, result)] < universal_last_seen[result]:
            old_results.add(result)
      raw_results -= old_results

    return [rdf_client.ClientURN(result) for result in raw_results]


Instruction:
Write a Python 3 function that can
read all clients associated with any of the given keywords.

Response:
def ReadClientPostingLists(self, keywords):
    """Looks up all clients associated with any of the given keywords.

    Args:
      keywords: A list of keywords we are interested in.

    Returns:
      A dict mapping each keyword to a list of matching clients.
    """

    start_time, end_time, filtered_keywords, _ = self._AnalyzeKeywords(keywords)

    # TODO(user): Make keyword index datetime aware so that
    # AsMicrosecondsSinceEpoch is unecessary.
    return self.ReadPostingLists(
        filtered_keywords,
        start_time=start_time.AsMicrosecondsSinceEpoch(),
        end_time=end_time.AsMicrosecondsSinceEpoch())


Instruction:
Can you generate the documentation for the following Python 3 function
def AnalyzeClient(self, client):

    client_id = self._ClientIdFromURN(client.urn)

    # Start with both the client id itself, and a universal keyword, used to
    # find all clients.
    #
    # TODO(user): Remove the universal keyword once we have a better way
    # to do this, i.e., once we have a storage library which can list all
    # clients directly.

    keywords = [self._NormalizeKeyword(client_id), "."]

    def TryAppend(prefix, keyword):
      precondition.AssertType(prefix, Text)
      if keyword:
        keyword_string = self._NormalizeKeyword(Text(keyword))
        keywords.append(keyword_string)
        if prefix:
          keywords.append(prefix + ":" + keyword_string)

    def TryAppendPrefixes(prefix, keyword, delimiter):
      if keyword is None:
        return 0
      TryAppend(prefix, keyword)
      segments = keyword.split(delimiter)
      for i in range(1, len(segments)):
        TryAppend(prefix, delimiter.join(segments[0:i]))
      return len(segments)

    def TryAppendIP(ip):
      TryAppend("ip", ip)
      # IP4v?
      if TryAppendPrefixes("ip", str(ip), ".") == 4:
        return
      # IP6v?
      TryAppendPrefixes("ip", str(ip), ":")

    def TryAppendMac(mac):
      TryAppend("mac", mac)
      if len(mac) == 12:
        # If looks like a mac address without ":" symbols, also add the keyword
        # with them.
        TryAppend("mac", ":".join([mac[i:i + 2] for i in range(0, 12, 2)]))

    s = client.Schema
    TryAppend("host", client.Get(s.HOSTNAME))
    TryAppendPrefixes("host", client.Get(s.HOSTNAME), "-")
    TryAppend("host", client.Get(s.FQDN))
    TryAppendPrefixes("host", client.Get(s.FQDN), ".")
    TryAppend("", client.Get(s.SYSTEM))
    TryAppend("", client.Get(s.UNAME))
    TryAppend("", client.Get(s.OS_RELEASE))
    TryAppend("", client.Get(s.OS_VERSION))
    TryAppend("", client.Get(s.KERNEL))
    TryAppend("", client.Get(s.ARCH))

    kb = client.Get(s.KNOWLEDGE_BASE)
    if kb:
      for user in kb.users:
        TryAppend("user", user.username)
        TryAppend("", user.full_name)
        if user.full_name:
          for name in user.full_name.split():
            # full_name often includes nicknames and similar, wrapped in
            # punctuation, e.g. "Thomas 'TJ' Jones". We remove the most common
            # wrapping characters.
            TryAppend("", name.strip("\"'()"))

    for username in client.Get(s.USERNAMES, []):
      TryAppend("user", username)

    for interface in client.Get(s.INTERFACES, []):
      if interface.mac_address:
        TryAppendMac(interface.mac_address.human_readable_address)
      for ip in interface.GetIPAddresses():
        TryAppendIP(ip)

    # We should have all mac and ip addresses already, but some test data only
    # has it attached directly, so just in case we look there also.
    if client.Get(s.MAC_ADDRESS):
      for mac in str(client.Get(s.MAC_ADDRESS)).split("\n"):
        TryAppendMac(mac)
    ip_list = client.Get(s.HOST_IPS, "")
    for ip in str(ip_list).split("\n"):
      TryAppendIP(ip)

    client_info = client.Get(s.CLIENT_INFO)
    if client_info:
      TryAppend("client", client_info.client_name)
      TryAppend("client", client_info.client_version)
      if client_info.labels:
        for label in client_info.labels:
          TryAppend("label", label)

    for label in client.GetLabelsNames():
      TryAppend("label", label)

    return client_id, keywords

Response: Analyze a client record and returns the client_id and keywords.


Instruction:
Can you write a function in Python 3 where it
adds a client to the index.

Response:
def AddClient(self, client):
    """Adds a client to the index.

    Args:
      client: A VFSGRRClient record to add or update.
    """

    client_id, keywords = self.AnalyzeClient(client)
    self.AddKeywordsForName(client_id, keywords)


Instruction:
Can you implement a function in Python 3 that
removes all labels for a given client object.

Response:
def RemoveClientLabels(self, client):
    """Removes all labels for a given client object.

    Args:
      client: A VFSGRRClient record.
    """
    keywords = []
    for label in client.GetLabelsNames():
      keyword = self._NormalizeKeyword(utils.SmartStr(label))
      # This might actually delete a keyword with the same name as the label (if
      # there is one). Usually the client keywords will be rebuilt after the
      # deletion of the old labels though, so this can only destroy historic
      # index data; normal search functionality will not be affected.
      keywords.append(keyword)
      keywords.append("label:%s" % keyword)

    self.RemoveKeywordsForName(self._ClientIdFromURN(client.urn), keywords)


Instruction:
Can you write a function in Python 3 where it
extracts a start time from a list of keywords if present.

Response:
def _AnalyzeKeywords(self, keywords):
    """Extracts a start time from a list of keywords if present."""
    start_time = rdfvalue.RDFDatetime.Now() - rdfvalue.Duration("180d")
    filtered_keywords = []

    for k in keywords:
      if k.startswith(self.START_TIME_PREFIX):
        try:
          start_time = rdfvalue.RDFDatetime.FromHumanReadable(
              k[self.START_TIME_PREFIX_LEN:])
        except ValueError:
          pass
      else:
        filtered_keywords.append(k)

    if not filtered_keywords:
      filtered_keywords.append(".")

    return start_time, filtered_keywords


Instruction:
How would you explain what the following Python 3 function does
def LookupClients(self, keywords):
    if isinstance(keywords, string_types):
      raise ValueError(
          "Keywords should be an iterable, not a string (got %s)." % keywords)

    start_time, filtered_keywords = self._AnalyzeKeywords(keywords)

    keyword_map = data_store.REL_DB.ListClientsForKeywords(
        list(map(self._NormalizeKeyword, filtered_keywords)),
        start_time=start_time)

    results = itervalues(keyword_map)
    relevant_set = set(next(results))

    for hits in results:
      relevant_set &= set(hits)

      if not relevant_set:
        return []

    return sorted(relevant_set)

Response: Searches for clients associated with a list of keywords.


Instruction:
Given the following Python 3 function, write the documentation
def ReadClientPostingLists(self, keywords):

    start_time, filtered_keywords = self._AnalyzeKeywords(keywords)

    return data_store.REL_DB.ListClientsForKeywords(
        filtered_keywords, start_time=start_time)

Response: Reads all clients associated with any of the given keywords.


Instruction:
Can you implement a function in Python 3 that
analyzes a client object record and returns a list of keywords related to it.

Response:
def AnalyzeClient(self, client):
    """Finds the client_id and keywords for a client.

    Args:
      client: A Client object record to find keywords for.

    Returns:
      A list of keywords related to client.
    """

    # Start with a universal keyword, used to find all clients.
    #
    # TODO(user): Remove the universal keyword once we have a better way
    # to do this, i.e., once we have a storage library which can list all
    # clients directly.

    keywords = set(["."])

    def TryAppend(prefix, keyword):
      precondition.AssertType(prefix, Text)
      precondition.AssertType(keyword, Text)
      if keyword:
        keyword_string = self._NormalizeKeyword(keyword)
        keywords.add(keyword_string)
        if prefix:
          keywords.add(prefix + ":" + keyword_string)

    def TryAppendPrefixes(prefix, keyword, delimiter):
      TryAppend(prefix, keyword)
      segments = keyword.split(delimiter)
      for i in range(1, len(segments)):
        TryAppend(prefix, delimiter.join(segments[0:i]))
      return len(segments)

    def TryAppendIP(ip):
      TryAppend("ip", ip)
      # IP4v?
      if TryAppendPrefixes("ip", Text(ip), ".") == 4:
        return
      # IP6v?
      TryAppendPrefixes("ip", Text(ip), ":")

    def TryAppendMac(mac):
      TryAppend("mac", mac)
      if len(mac) == 12:
        # If looks like a mac address without ":" symbols, also add the keyword
        # with them.
        TryAppend("mac", ":".join([mac[i:i + 2] for i in range(0, 12, 2)]))

    TryAppend("host", client.knowledge_base.fqdn)
    host = client.knowledge_base.fqdn.split(".", 1)[0]
    TryAppendPrefixes("host", host, "-")
    TryAppendPrefixes("host", client.knowledge_base.fqdn, ".")
    TryAppend("", client.knowledge_base.os)
    TryAppend("", client.Uname())
    TryAppend("", client.os_release)
    TryAppend("", client.os_version)
    TryAppend("", client.kernel)
    TryAppend("", client.arch)

    kb = client.knowledge_base
    if kb:
      for user in kb.users:
        TryAppend("user", user.username)
        TryAppend("", user.full_name)
        if user.full_name:
          for name in user.full_name.split():
            # full_name often includes nicknames and similar, wrapped in
            # punctuation, e.g. "Thomas 'TJ' Jones". We remove the most common
            # wrapping characters.
            TryAppend("", name.strip("\"'()"))

    for ip in client.GetIPAddresses():
      TryAppendIP(ip)
    for mac in client.GetMacAddresses():
      TryAppendMac(mac)

    client_info = client.startup_info.client_info
    if client_info:
      TryAppend("client", client_info.client_name)
      TryAppend("client", Text(client_info.client_version))
      if client_info.labels:
        for label in client_info.labels:
          TryAppend("label", label)

    return keywords


Instruction:
Here you have a function in Python 3, explain what it does
def AddClient(self, client):
    keywords = self.AnalyzeClient(client)
    keywords.add(self._NormalizeKeyword(client.client_id))

    data_store.REL_DB.AddClientKeywords(client.client_id, keywords)

Response: Adds a client to the index.


Instruction:
Write a Python 3 script to
remove all labels for a given client.

Response:
def RemoveAllClientLabels(self, client_id):
    """Removes all labels for a given client.

    Args:
      client_id: The client_id.
    """
    labels_to_remove = set(
        [l.name for l in data_store.REL_DB.ReadClientLabels(client_id)])
    self.RemoveClientLabels(client_id, labels_to_remove)


Instruction:
How would you code a function in Python 3 to
remove all labels for a given client.

Response:
def RemoveClientLabels(self, client_id, labels):
    """Removes all labels for a given client.

    Args:
      client_id: The client_id.
      labels: A list of labels to remove.
    """
    for label in labels:
      keyword = self._NormalizeKeyword(label)
      # This might actually delete a keyword with the same name as the label (if
      # there is one).
      data_store.REL_DB.RemoveClientKeyword(client_id, keyword)
      data_store.REL_DB.RemoveClientKeyword(client_id, "label:%s" % keyword)


Instruction:
Write a Python 3 script to
verify the signature of a message.

Response:
def VerifyMessageSignature(self, response_comms, packed_message_list, cipher,
                             cipher_verified, api_version, remote_public_key):
    """Verifies the message list signature.

    In the server we check that the timestamp is later than the ping timestamp
    stored with the client. This ensures that client responses can not be
    replayed.

    Args:
      response_comms: The raw response_comms rdfvalue.
      packed_message_list: The PackedMessageList rdfvalue from the server.
      cipher: The cipher object that should be used to verify the message.
      cipher_verified: If True, the cipher's signature is not verified again.
      api_version: The api version we should use.
      remote_public_key: The public key of the source.

    Returns:
      An rdf_flows.GrrMessage.AuthorizationState.
    """
    if (not cipher_verified and
        not cipher.VerifyCipherSignature(remote_public_key)):
      stats_collector_instance.Get().IncrementCounter(
          "grr_unauthenticated_messages")
      return rdf_flows.GrrMessage.AuthorizationState.UNAUTHENTICATED

    try:
      client_id = cipher.cipher_metadata.source
      try:
        client = self.client_cache.Get(client_id)
      except KeyError:
        client = aff4.FACTORY.Create(
            client_id,
            aff4.AFF4Object.classes["VFSGRRClient"],
            mode="rw",
            token=self.token)
        self.client_cache.Put(client_id, client)
        stats_collector_instance.Get().SetGaugeValue(
            "grr_frontendserver_client_cache_size", len(self.client_cache))

      ip = response_comms.orig_request.source_ip
      client.Set(client.Schema.CLIENT_IP(ip))

      # The very first packet we see from the client we do not have its clock
      remote_time = client.Get(client.Schema.CLOCK) or rdfvalue.RDFDatetime(0)
      client_time = packed_message_list.timestamp or rdfvalue.RDFDatetime(0)

      # This used to be a strict check here so absolutely no out of
      # order messages would be accepted ever. Turns out that some
      # proxies can send your request with some delay even if the
      # client has already timed out (and sent another request in
      # the meantime, making the first one out of order). In that
      # case we would just kill the whole flow as a
      # precaution. Given the behavior of those proxies, this seems
      # now excessive and we have changed the replay protection to
      # only trigger on messages that are more than one hour old.

      if client_time < remote_time - rdfvalue.Duration("1h"):
        logging.warning("Message desynchronized for %s: %s >= %s", client_id,
                        remote_time, client_time)
        # This is likely an old message
        return rdf_flows.GrrMessage.AuthorizationState.DESYNCHRONIZED

      stats_collector_instance.Get().IncrementCounter(
          "grr_authenticated_messages")

      # Update the client and server timestamps only if the client
      # time moves forward.
      if client_time > remote_time:
        client.Set(client.Schema.CLOCK, client_time)
        client.Set(client.Schema.PING, rdfvalue.RDFDatetime.Now())

        clock = client_time
        ping = rdfvalue.RDFDatetime.Now()

        for label in client.Get(client.Schema.LABELS, []):
          stats_collector_instance.Get().IncrementCounter(
              "client_pings_by_label", fields=[label.name])
      else:
        clock = None
        ping = None
        logging.warning("Out of order message for %s: %s >= %s", client_id,
                        remote_time, client_time)

      client.Flush()
      if data_store.RelationalDBEnabled():
        source_ip = response_comms.orig_request.source_ip
        if source_ip:
          last_ip = rdf_client_network.NetworkAddress(
              human_readable_address=response_comms.orig_request.source_ip)
        else:
          last_ip = None

        if ping or clock or last_ip:
          try:
            data_store.REL_DB.WriteClientMetadata(
                client_id.Basename(),
                last_ip=last_ip,
                last_clock=clock,
                last_ping=ping,
                fleetspeak_enabled=False)
          except db.UnknownClientError:
            pass

    except communicator.UnknownClientCertError:
      pass

    return rdf_flows.GrrMessage.AuthorizationState.AUTHENTICATED


Instruction:
Can you write a function in Python 3 where it
verifies the signature of a message list.

Response:
def VerifyMessageSignature(self, response_comms, packed_message_list, cipher,
                             cipher_verified, api_version, remote_public_key):
    """Verifies the message list signature.

    In the server we check that the timestamp is later than the ping timestamp
    stored with the client. This ensures that client responses can not be
    replayed.

    Args:
      response_comms: The raw response_comms rdfvalue.
      packed_message_list: The PackedMessageList rdfvalue from the server.
      cipher: The cipher object that should be used to verify the message.
      cipher_verified: If True, the cipher's signature is not verified again.
      api_version: The api version we should use.
      remote_public_key: The public key of the source.

    Returns:
      An rdf_flows.GrrMessage.AuthorizationState.
    """
    if (not cipher_verified and
        not cipher.VerifyCipherSignature(remote_public_key)):
      stats_collector_instance.Get().IncrementCounter(
          "grr_unauthenticated_messages")
      return rdf_flows.GrrMessage.AuthorizationState.UNAUTHENTICATED

    try:
      client_id = cipher.cipher_metadata.source.Basename()
      metadata = data_store.REL_DB.ReadClientMetadata(client_id)
      client_time = packed_message_list.timestamp or rdfvalue.RDFDatetime(0)
      update_metadata = True

      # This used to be a strict check here so absolutely no out of
      # order messages would be accepted ever. Turns out that some
      # proxies can send your request with some delay even if the
      # client has already timed out (and sent another request in
      # the meantime, making the first one out of order). In that
      # case we would just kill the whole flow as a
      # precaution. Given the behavior of those proxies, this seems
      # now excessive and we have changed the replay protection to
      # only trigger on messages that are more than one hour old.
      if metadata and metadata.clock:
        stored_client_time = metadata.clock

        if client_time < stored_client_time - rdfvalue.Duration("1h"):
          logging.warning("Message desynchronized for %s: %s >= %s", client_id,
                          stored_client_time, client_time)
          # This is likely an old message
          return rdf_flows.GrrMessage.AuthorizationState.DESYNCHRONIZED

        # Update the client and server timestamps only if the client time moves
        # forward.
        if client_time < stored_client_time:
          logging.warning("Out of order message for %s: %s > %s", client_id,
                          stored_client_time, client_time)
          update_metadata = False

      stats_collector_instance.Get().IncrementCounter(
          "grr_authenticated_messages")

      for label in data_store.REL_DB.ReadClientLabels(client_id):
        stats_collector_instance.Get().IncrementCounter(
            "client_pings_by_label", fields=[label.name])

      if not update_metadata:
        return rdf_flows.GrrMessage.AuthorizationState.AUTHENTICATED

      source_ip = response_comms.orig_request.source_ip
      if source_ip:
        last_ip = rdf_client_network.NetworkAddress(
            human_readable_address=response_comms.orig_request.source_ip)
      else:
        last_ip = None

      data_store.REL_DB.WriteClientMetadata(
          client_id,
          last_ip=last_ip,
          last_clock=client_time,
          last_ping=rdfvalue.RDFDatetime.Now(),
          fleetspeak_enabled=False)

    except communicator.UnknownClientCertError:
      pass

    return rdf_flows.GrrMessage.AuthorizationState.AUTHENTICATED


Instruction:
Create a Python 3 function for
processing a queue of messages as passed from the client. We basically dispatch all the GrrMessages in the queue to the task scheduler for backend processing. We then retrieve from the TS the messages destined for this client. Args: request_comms: A ClientCommunication rdfvalue with messages sent by the client. source should be set to the client CN. response_comms: A ClientCommunication rdfvalue of jobs destined to this client. Returns: tuple of (source, message_count) where message_count is the number of messages received from the client with common name source.

Response:
def HandleMessageBundles(self, request_comms, response_comms):
    """Processes a queue of messages as passed from the client.

    We basically dispatch all the GrrMessages in the queue to the task scheduler
    for backend processing. We then retrieve from the TS the messages destined
    for this client.

    Args:
       request_comms: A ClientCommunication rdfvalue with messages sent by the
         client. source should be set to the client CN.
       response_comms: A ClientCommunication rdfvalue of jobs destined to this
         client.

    Returns:
       tuple of (source, message_count) where message_count is the number of
       messages received from the client with common name source.
    """
    messages, source, timestamp = self._communicator.DecodeMessages(
        request_comms)

    now = time.time()
    if messages:
      # Receive messages in line.
      self.ReceiveMessages(source, messages)

    # We send the client a maximum of self.max_queue_size messages
    required_count = max(0, self.max_queue_size - request_comms.queue_size)
    tasks = []

    message_list = rdf_flows.MessageList()
    # Only give the client messages if we are able to receive them in a
    # reasonable time.
    if time.time() - now < 10:
      tasks = self.DrainTaskSchedulerQueueForClient(source, required_count)
      message_list.job = tasks

    # Encode the message_list in the response_comms using the same API version
    # the client used.
    self._communicator.EncodeMessages(
        message_list,
        response_comms,
        destination=source,
        timestamp=timestamp,
        api_version=request_comms.api_version)

    return source, len(messages)


Instruction:
Create a Python 3 function for
draining the Task Scheduler queue for a given client.

Response:
def DrainTaskSchedulerQueueForClient(self, client, max_count=None):
    """Drains the client's Task Scheduler queue.

    1) Get all messages in the client queue.
    2) Sort these into a set of session_ids.
    3) Use data_store.DB.ResolvePrefix() to query all requests.
    4) Delete all responses for retransmitted messages (if needed).

    Args:
       client: The ClientURN object specifying this client.
       max_count: The maximum number of messages we will issue for the client.
         If not given, uses self.max_queue_size .

    Returns:
       The tasks respresenting the messages returned. If we can not send them,
       we can reschedule them for later.
    """
    if max_count is None:
      max_count = self.max_queue_size

    if max_count <= 0:
      return []

    client = rdf_client.ClientURN(client)
    start_time = time.time()
    # Drain the queue for this client
    if data_store.RelationalDBEnabled():
      action_requests = data_store.REL_DB.LeaseClientActionRequests(
          client.Basename(),
          lease_time=rdfvalue.Duration.FromSeconds(self.message_expiry_time),
          limit=max_count)
      result = [
          rdf_flow_objects.GRRMessageFromClientActionRequest(r)
          for r in action_requests
      ]
    else:
      new_tasks = queue_manager.QueueManager(token=self.token).QueryAndOwn(
          queue=client.Queue(),
          limit=max_count,
          lease_seconds=self.message_expiry_time)

      initial_ttl = rdf_flows.GrrMessage().task_ttl
      check_before_sending = []
      result = []
      for task in new_tasks:
        if task.task_ttl < initial_ttl - 1:
          # This message has been leased before.
          check_before_sending.append(task)
        else:
          result.append(task)

      if check_before_sending:
        with queue_manager.QueueManager(token=self.token) as manager:
          status_found = manager.MultiCheckStatus(check_before_sending)

          # All messages that don't have a status yet should be sent again.
          for task in check_before_sending:
            if task not in status_found:
              result.append(task)
            else:
              manager.DeQueueClientRequest(task)

    stats_collector_instance.Get().IncrementCounter("grr_messages_sent",
                                                    len(result))
    if result:
      logging.debug("Drained %d messages for %s in %s seconds.", len(result),
                    client,
                    time.time() - start_time)

    return result


Instruction:
Create a Python 3 function for
enroling a Fleetspeak - enabled client for use with GRR.

Response:
def EnrolFleetspeakClient(self, client_id):
    """Enrols a Fleetspeak-enabled client for use with GRR.

    Args:
      client_id: GRR client-id for the client.

    Returns:
      True if the client is new, and actually got enrolled. This method
      is a no-op if the client already exists (in which case False is returned).
    """
    client_urn = rdf_client.ClientURN(client_id)

    # If already enrolled, return.
    if data_store.RelationalDBEnabled():
      try:
        data_store.REL_DB.ReadClientMetadata(client_id)
        return False
      except db.UnknownClientError:
        pass
    else:
      if aff4.FACTORY.ExistsWithType(
          client_urn, aff4_type=aff4_grr.VFSGRRClient, token=self.token):
        return False

    logging.info("Enrolling a new Fleetspeak client: %r", client_id)

    if data_store.RelationalDBEnabled():
      now = rdfvalue.RDFDatetime.Now()
      data_store.REL_DB.WriteClientMetadata(
          client_id, first_seen=now, fleetspeak_enabled=True, last_ping=now)

    if data_store.AFF4Enabled():
      # TODO(fleetspeak-team,grr-team): If aff4 isn't reliable enough, we can
      # catch exceptions from it and forward them to Fleetspeak by failing its
      # gRPC call. Fleetspeak will then retry with a random, perhaps healthier,
      # instance of the GRR frontend.
      with aff4.FACTORY.Create(
          client_urn,
          aff4_type=aff4_grr.VFSGRRClient,
          mode="rw",
          token=self.token) as client:

        client.Set(client.Schema.FLEETSPEAK_ENABLED, rdfvalue.RDFBool(True))

        index = client_index.CreateClientIndex(token=self.token)
        index.AddClient(client)
        if data_store.RelationalDBEnabled():
          client_obj = rdf_objects.ClientSnapshot(
              client_id=client_urn.Basename())
          index = client_index.ClientIndex()
          index.AddClient(client_obj)

    # Publish the client enrollment message.
    events.Events.PublishEvent("ClientEnrollment", client_urn, token=self.token)
    return True


Instruction:
Here you have a function in Python 3, explain what it does
def ReceiveMessagesRelationalFlows(self, client_id, messages):
    now = time.time()
    unprocessed_msgs = []
    message_handler_requests = []
    dropped_count = 0
    for session_id, msgs in iteritems(
        collection.Group(messages, operator.attrgetter("session_id"))):

      # Remove and handle messages to WellKnownFlows
      leftover_msgs = self.HandleWellKnownFlows(msgs)

      for msg in leftover_msgs:
        if (msg.auth_state != msg.AuthorizationState.AUTHENTICATED and
            msg.session_id != self.unauth_allowed_session_id):
          dropped_count += 1
          continue

        if session_id in queue_manager.session_id_map:
          message_handler_requests.append(
              rdf_objects.MessageHandlerRequest(
                  client_id=msg.source.Basename(),
                  handler_name=queue_manager.session_id_map[session_id],
                  request_id=msg.response_id,
                  request=msg.payload))
        else:
          unprocessed_msgs.append(msg)

    if dropped_count:
      logging.info("Dropped %d unauthenticated messages for %s", dropped_count,
                   client_id)

    if unprocessed_msgs:
      flow_responses = []
      for message in unprocessed_msgs:
        flow_responses.append(
            rdf_flow_objects.FlowResponseForLegacyResponse(message))

      data_store.REL_DB.WriteFlowResponses(flow_responses)

      for msg in unprocessed_msgs:
        if msg.type == rdf_flows.GrrMessage.Type.STATUS:
          stat = rdf_flows.GrrStatus(msg.payload)
          if stat.status == rdf_flows.GrrStatus.ReturnedStatus.CLIENT_KILLED:
            # A client crashed while performing an action, fire an event.
            crash_details = rdf_client.ClientCrash(
                client_id=client_id,
                session_id=msg.session_id,
                backtrace=stat.backtrace,
                crash_message=stat.error_message,
                nanny_status=stat.nanny_status,
                timestamp=rdfvalue.RDFDatetime.Now())
            events.Events.PublishEvent(
                "ClientCrash", crash_details, token=self.token)

    if message_handler_requests:
      data_store.REL_DB.WriteMessageHandlerRequests(message_handler_requests)

    logging.debug("Received %s messages from %s in %s sec", len(messages),
                  client_id,
                  time.time() - now)

Response: Receives and processes messages for flows stored in the relational db.


Instruction:
Given the following Python 3 function, write the documentation
def ReceiveMessages(self, client_id, messages):
    if data_store.RelationalDBEnabled():
      return self.ReceiveMessagesRelationalFlows(client_id, messages)

    now = time.time()
    with queue_manager.QueueManager(token=self.token) as manager:
      for session_id, msgs in iteritems(
          collection.Group(messages, operator.attrgetter("session_id"))):

        # Remove and handle messages to WellKnownFlows
        leftover_msgs = self.HandleWellKnownFlows(msgs)

        unprocessed_msgs = []
        for msg in leftover_msgs:
          if (msg.auth_state == msg.AuthorizationState.AUTHENTICATED or
              msg.session_id == self.unauth_allowed_session_id):
            unprocessed_msgs.append(msg)

        if len(unprocessed_msgs) < len(leftover_msgs):
          logging.info("Dropped %d unauthenticated messages for %s",
                       len(leftover_msgs) - len(unprocessed_msgs), client_id)

        if not unprocessed_msgs:
          continue

        for msg in unprocessed_msgs:
          manager.QueueResponse(msg)

        for msg in unprocessed_msgs:
          # Messages for well known flows should notify even though they don't
          # have a status.
          if msg.request_id == 0:
            manager.QueueNotification(session_id=msg.session_id)
            # Those messages are all the same, one notification is enough.
            break
          elif msg.type == rdf_flows.GrrMessage.Type.STATUS:
            # If we receive a status message from the client it means the client
            # has finished processing this request. We therefore can de-queue it
            # from the client queue. msg.task_id will raise if the task id is
            # not set (message originated at the client, there was no request on
            # the server), so we have to check .HasTaskID() first.
            if msg.HasTaskID():
              manager.DeQueueClientRequest(msg)

            manager.QueueNotification(
                session_id=msg.session_id, last_status=msg.request_id)

            stat = rdf_flows.GrrStatus(msg.payload)
            if stat.status == rdf_flows.GrrStatus.ReturnedStatus.CLIENT_KILLED:
              # A client crashed while performing an action, fire an event.
              crash_details = rdf_client.ClientCrash(
                  client_id=client_id,
                  session_id=session_id,
                  backtrace=stat.backtrace,
                  crash_message=stat.error_message,
                  nanny_status=stat.nanny_status,
                  timestamp=rdfvalue.RDFDatetime.Now())
              events.Events.PublishEvent(
                  "ClientCrash", crash_details, token=self.token)

    logging.debug("Received %s messages from %s in %s sec", len(messages),
                  client_id,
                  time.time() - now)

Response: Receives and processes the messages from the source.


Instruction:
Write a Python 3 function that can
handle well known flows.

Response:
def HandleWellKnownFlows(self, messages):
    """Hands off messages to well known flows."""
    msgs_by_wkf = {}
    result = []
    for msg in messages:
      # Regular message - queue it.
      if msg.response_id != 0:
        result.append(msg)
        continue

      # Well known flows:
      flow_name = msg.session_id.FlowName()

      if flow_name in self.well_known_flows:
        # This message should be processed directly on the front end.
        msgs_by_wkf.setdefault(flow_name, []).append(msg)

        # TODO(user): Deprecate in favor of 'well_known_flow_requests'
        # metric.
        stats_collector_instance.Get().IncrementCounter(
            "grr_well_known_flow_requests")

        stats_collector_instance.Get().IncrementCounter(
            "well_known_flow_requests", fields=[str(msg.session_id)])
      else:
        # Message should be queued to be processed in the backend.

        # Well known flows have a response_id==0, but if we queue up the state
        # as that it will overwrite some other message that is queued. So we
        # change it to a random number here.
        msg.response_id = random.UInt32()

        # Queue the message in the data store.
        result.append(msg)

    for flow_name, msg_list in iteritems(msgs_by_wkf):
      wkf = self.well_known_flows[flow_name]
      wkf.ProcessMessages(msg_list)

    return result