122 lines
3.9 KiB
Python
122 lines
3.9 KiB
Python
#!/usr/bin/python
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# -*- coding: utf-8 -*-
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#
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# Copyright 2013 The Plaso Project Authors.
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# Please see the AUTHORS file for details on individual authors.
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#
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# Licensed under the Apache License, Version 2.0 (the 'License');
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""This file contains the Bencode Parser.
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Plaso's engine calls BencodeParser when it encounters bencoded files to be
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processed, typically seen for BitTorrent data.
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"""
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import logging
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import re
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import os
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import bencode
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from plaso.lib import errors
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from plaso.parsers import interface
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from plaso.parsers import manager
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class BencodeParser(interface.BasePluginsParser):
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"""Deserializes bencoded file; produces a dictionary containing bencoded data.
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The Plaso engine calls parsers by their Parse() method. This parser's
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Parse() has GetTopLevel() which deserializes bencoded files using the
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BitTorrent-bencode library and calls plugins (BencodePlugin) registered
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through the interface by their Process() to produce event objects.
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Plugins are how this parser understands the content inside a bencoded file,
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each plugin holds logic specific to a particular bencoded file. See the
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bencode_plugins / directory for examples of how bencode plugins are
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implemented.
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"""
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# Regex match for a bencode dictionary followed by a field size.
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BENCODE_RE = re.compile('d[0-9]')
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NAME = 'bencode'
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DESCRIPTION = u'Parser for bencoded files.'
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_plugin_classes = {}
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def __init__(self):
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"""Initializes a parser object."""
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super(BencodeParser, self).__init__()
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self._plugins = BencodeParser.GetPluginObjects()
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def GetTopLevel(self, file_object):
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"""Returns deserialized content of a bencoded file as a dictionary object.
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Args:
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file_object: A file-like object.
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Returns:
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Dictionary object representing the contents of the bencoded file.
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"""
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header = file_object.read(2)
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file_object.seek(0, os.SEEK_SET)
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if not self.BENCODE_RE.match(header):
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raise errors.UnableToParseFile(u'Not a valid Bencoded file.')
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try:
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data_object = bencode.bdecode(file_object.read())
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except (IOError, bencode.BTFailure) as exception:
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raise errors.UnableToParseFile(
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u'Unable to parse invalid Bencoded file with error: {0:s}'.format(
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exception))
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if not data_object:
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raise errors.UnableToParseFile(u'Not a valid Bencoded file.')
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return data_object
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def Parse(self, parser_context, file_entry, parser_chain=None):
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"""Parse and extract values from a bencoded file.
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Args:
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parser_context: A parser context object (instance of ParserContext).
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file_entry: A file entry object (instance of dfvfs.FileEntry).
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parser_chain: Optional string containing the parsing chain up to this
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point. The default is None.
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"""
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file_object = file_entry.GetFileObject()
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data_object = self.GetTopLevel(file_object)
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if not data_object:
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file_object.close()
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raise errors.UnableToParseFile(
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u'[{0:s}] unable to parse: {1:s}. Skipping.'.format(
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self.NAME, file_entry.name))
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parser_chain = self._BuildParserChain(parser_chain)
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for plugin_object in self._plugins:
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try:
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plugin_object.Process(
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parser_context, data=data_object, file_entry=file_entry,
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parser_chain=parser_chain)
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except errors.WrongBencodePlugin as exception:
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logging.debug(u'[{0:s}] wrong plugin: {1:s}'.format(
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self.NAME, exception))
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file_object.close()
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manager.ParsersManager.RegisterParser(BencodeParser)
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