PyCIRCLean/bin/filecheck.py

593 lines
24 KiB
Python

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import os
import mimetypes
import shlex
import subprocess
import zipfile
import argparse
import oletools.oleid
import olefile
import officedissector
import warnings
import exifread
from PIL import Image
# from PIL import PngImagePlugin
from pdfid import PDFiD, cPDFiD
from kittengroomer import FileBase, KittenGroomerBase
SEVENZ_PATH = '/usr/bin/7z'
class Config:
# Application subtypes (mimetype: 'application/<subtype>')
mimes_ooxml = ['vnd.openxmlformats-officedocument.']
mimes_office = ['msword', 'vnd.ms-']
mimes_libreoffice = ['vnd.oasis.opendocument']
mimes_rtf = ['rtf', 'richtext']
mimes_pdf = ['pdf', 'postscript']
mimes_xml = ['xml']
mimes_ms = ['dosexec']
mimes_compressed = ['zip', 'rar', 'bzip2', 'lzip', 'lzma', 'lzop',
'xz', 'compress', 'gzip', 'tar']
mimes_data = ['octet-stream']
# Image subtypes
mimes_exif = ['image/jpeg', 'image/tiff']
mimes_png = ['image/png']
# Mimetypes with metadata
mimes_metadata = ['image/jpeg', 'image/tiff', 'image/png']
# Commonly used malicious extensions
# Sources: http://www.howtogeek.com/137270/50-file-extensions-that-are-potentially-dangerous-on-windows/
# https://github.com/wiregit/wirecode/blob/master/components/core-settings/src/main/java/org/limewire/core/settings/FilterSettings.java
malicious_exts = (
# Applications
".exe", ".pif", ".application", ".gadget", ".msi", ".msp", ".com", ".scr",
".hta", ".cpl", ".msc", ".jar",
# Scripts
".bat", ".cmd", ".vb", ".vbs", ".vbe", ".js", ".jse", ".ws", ".wsf",
".wsc", ".wsh", ".ps1", ".ps1xml", ".ps2", ".ps2xml", ".psc1", ".psc2",
".msh", ".msh1", ".msh2", ".mshxml", ".msh1xml", ".msh2xml",
# Shortcuts
".scf", ".lnk", ".inf",
# Other
".reg", ".dll",
# Office macro (OOXML with macro enabled)
".docm", ".dotm", ".xlsm", ".xltm", ".xlam", ".pptm", ".potm", ".ppam",
".ppsm", ".sldm",
# banned from wirecode
".asf", ".asx", ".au", ".htm", ".html", ".mht", ".vbs",
".wax", ".wm", ".wma", ".wmd", ".wmv", ".wmx", ".wmz", ".wvx",
)
# Aliases
aliases = {
# Win executables
'application/x-msdos-program': 'application/x-dosexec',
'application/x-dosexec': 'application/x-msdos-program',
# Other apps with confusing mimetypes
'application/rtf': 'text/rtf',
}
# Sometimes, mimetypes.guess_type gives unexpected results, such as for .tar.gz files:
# In [12]: mimetypes.guess_type('toot.tar.gz', strict=False)
# Out[12]: ('application/x-tar', 'gzip')
# It works as expected if you do mimetypes.guess_type('application/gzip', strict=False)
override_ext = {'.gz': 'application/gzip'}
class File(FileBase):
def __init__(self, src_path, dst_path, logger):
super(File, self).__init__(src_path, dst_path, logger)
self.is_recursive = False
self._check_dangerous()
if self.is_dangerous():
return
self.log_details.update({'maintype': self.main_type,
'subtype': self.sub_type,
'extension': self.extension})
self._check_extension()
self._check_mime()
def _check_dangerous(self):
if not self.has_mimetype():
# No mimetype, should not happen.
self.make_dangerous()
if not self.has_extension():
self.make_dangerous()
if self.extension in Config.malicious_exts:
self.log_details.update({'malicious_extension': self.extension})
self.make_dangerous()
def _check_extension(self):
"""Guesses the file's mimetype based on its extension. If the file's
mimetype (as determined by libmagic) is contained in the mimetype
module's list of valid mimetypes and the expected mimetype based on its
extension differs from the mimetype determined by libmagic, then it
marks the file as dangerous."""
if self.extension in Config.override_ext:
expected_mimetype = Config.override_ext[self.extension]
else:
expected_mimetype, encoding = mimetypes.guess_type(self.src_path, strict=False)
if expected_mimetype in Config.aliases:
expected_mimetype = Config.aliases[expected_mimetype]
is_known_extension = self.extension in mimetypes.types_map.keys()
if is_known_extension and expected_mimetype != self.mimetype:
self.log_details.update({'expected_mimetype': expected_mimetype})
self.make_dangerous()
def _check_mime(self):
"""Takes the mimetype (as determined by libmagic) and determines
whether the list of extensions that are normally associated with
that extension contains the file's actual extension."""
if self.mimetype in Config.aliases:
mimetype = Config.aliases[self.mimetype]
else:
mimetype = self.mimetype
expected_extensions = mimetypes.guess_all_extensions(mimetype, strict=False)
if expected_extensions:
if len(self.extension) > 0 and self.extension not in expected_extensions:
self.log_details.update({'expected_extensions': expected_extensions})
self.make_dangerous()
def has_metadata(self):
if self.mimetype in Config.mimes_metadata:
return True
return False
class KittenGroomerFileCheck(KittenGroomerBase):
def __init__(self, root_src, root_dst, max_recursive_depth=2, debug=False):
super(KittenGroomerFileCheck, self).__init__(root_src, root_dst, debug)
self.recursive_archive_depth = 0
self.max_recursive_depth = max_recursive_depth
self.log_name = self.logger.log
subtypes_apps = [
(Config.mimes_office, self._winoffice),
(Config.mimes_ooxml, self._ooxml),
(Config.mimes_rtf, self.text),
(Config.mimes_libreoffice, self._libreoffice),
(Config.mimes_pdf, self._pdf),
(Config.mimes_xml, self.text),
(Config.mimes_ms, self._executables),
(Config.mimes_compressed, self._archive),
(Config.mimes_data, self._binary_app),
]
self.app_subtype_methods = self._make_method_dict(subtypes_apps)
types_metadata = [
(Config.mimes_exif, self._metadata_exif),
(Config.mimes_png, self._metadata_png),
]
self.metadata_mimetype_methods = self._make_method_dict(types_metadata)
self.mime_processing_options = {
'text': self.text,
'audio': self.audio,
'image': self.image,
'video': self.video,
'application': self.application,
'example': self.example,
'message': self.message,
'model': self.model,
'multipart': self.multipart,
'inode': self.inode,
}
# ##### Helper functions #####
def _make_method_dict(self, list_of_tuples):
"""Returns a dictionary with mimetype: method pairs."""
dict_to_return = {}
for list_of_subtypes, method in list_of_tuples:
for subtype in list_of_subtypes:
dict_to_return[subtype] = method
return dict_to_return
def _write_log(self):
"""Print the logs related to the current file being processed."""
# TODO: move to helpers
tmp_log = self.logger.log.fields(**self.cur_file.log_details)
if self.cur_file.is_dangerous():
tmp_log.warning(self.cur_file.log_string)
elif self.cur_file.log_details.get('unknown') or self.cur_file.log_details.get('binary'):
tmp_log.info(self.cur_file.log_string)
else:
tmp_log.debug(self.cur_file.log_string)
def _run_process(self, command_string, timeout=None):
"""Run command_string in a subprocess, wait until it finishes."""
args = shlex.split(command_string)
with open(self.logger.log_debug_err, 'ab') as stderr, open(self.logger.log_debug_out, 'ab') as stdout:
try:
subprocess.check_call(args, stdout=stdout, stderr=stderr, timeout=timeout)
except (subprocess.TimeoutExpired, subprocess.CalledProcessError):
return
return True
#######################
# ##### Discarded mimetypes, reason in the docstring ######
def inode(self):
"""Empty file or symlink."""
if self.cur_file.is_symlink():
self.cur_file.log_string += 'Symlink to {}'.format(self.cur_file.log_details['symlink'])
else:
self.cur_file.log_string += 'Inode file'
def unknown(self):
"""Main type should never be unknown."""
self.cur_file.log_string += 'Unknown file'
def example(self):
"""Used in examples, should never be returned by libmagic."""
self.cur_file.log_string += 'Example file'
def multipart(self):
"""Used in web apps, should never be returned by libmagic"""
self.cur_file.log_string += 'Multipart file'
# ##### Treated as malicious, no reason to have it on a USB key ######
def message(self):
"""Process a message file."""
self.cur_file.log_string += 'Message file'
self.cur_file.make_dangerous()
self._safe_copy()
def model(self):
"""Process a model file."""
self.cur_file.log_string += 'Model file'
self.cur_file.make_dangerous()
self._safe_copy()
# ##### Files that will be converted ######
def text(self):
"""Process an rtf, ooxml, or plaintext file."""
for mt in Config.mimes_rtf:
if mt in self.cur_file.sub_type:
self.cur_file.log_string += 'Rich Text file'
# TODO: need a way to convert it to plain text
self.cur_file.force_ext('.txt')
self._safe_copy()
return
for mt in Config.mimes_ooxml:
if mt in self.cur_file.sub_type:
self.cur_file.log_string += 'OOXML File'
self._ooxml()
return
self.cur_file.log_string += 'Text file'
self.cur_file.force_ext('.txt')
self._safe_copy()
def application(self):
"""Processes an application specific file according to its subtype."""
for subtype, method in self.app_subtype_methods.items():
if subtype in self.cur_file.sub_type:
method()
self.cur_file.log_string += 'Application file'
return
self.cur_file.log_string += 'Unknown Application file'
self._unknown_app()
def _executables(self):
"""Processes an executable file."""
self.cur_file.add_log_details('processing_type', 'executable')
self.cur_file.make_dangerous()
self._safe_copy()
def _winoffice(self):
"""Processes a winoffice file using olefile/oletools."""
self.cur_file.add_log_details('processing_type', 'WinOffice')
# Try as if it is a valid document
oid = oletools.oleid.OleID(self.cur_file.src_path)
if not olefile.isOleFile(self.cur_file.src_path):
# Manual processing, may already count as suspicious
try:
ole = olefile.OleFileIO(self.cur_file.src_path, raise_defects=olefile.DEFECT_INCORRECT)
except:
self.cur_file.add_log_details('not_parsable', True)
self.cur_file.make_dangerous()
if ole.parsing_issues:
self.cur_file.add_log_details('parsing_issues', True)
self.cur_file.make_dangerous()
else:
if ole.exists('macros/vba') or ole.exists('Macros') \
or ole.exists('_VBA_PROJECT_CUR') or ole.exists('VBA'):
self.cur_file.add_log_details('macro', True)
self.cur_file.make_dangerous()
else:
indicators = oid.check()
# Encrypted ban be set by multiple checks on the script
if oid.encrypted.value:
self.cur_file.add_log_details('encrypted', True)
self.cur_file.make_dangerous()
if oid.macros.value or oid.ole.exists('macros/vba') or oid.ole.exists('Macros') \
or oid.ole.exists('_VBA_PROJECT_CUR') or oid.ole.exists('VBA'):
self.cur_file.add_log_details('macro', True)
self.cur_file.make_dangerous()
for i in indicators:
if i.id == 'ObjectPool' and i.value:
# FIXME: Is it suspicious?
self.cur_file.add_log_details('objpool', True)
elif i.id == 'flash' and i.value:
self.cur_file.add_log_details('flash', True)
self.cur_file.make_dangerous()
self._safe_copy()
def _ooxml(self):
"""Processes an ooxml file."""
self.cur_file.add_log_details('processing_type', 'ooxml')
try:
doc = officedissector.doc.Document(self.cur_file.src_path)
except Exception:
# Invalid file
self.cur_file.make_dangerous()
self._safe_copy()
return
# There are probably other potentially malicious features:
# fonts, custom props, custom XML
if doc.is_macro_enabled or len(doc.features.macros) > 0:
self.cur_file.add_log_details('macro', True)
self.cur_file.make_dangerous()
if len(doc.features.embedded_controls) > 0:
self.cur_file.add_log_details('activex', True)
self.cur_file.make_dangerous()
if len(doc.features.embedded_objects) > 0:
# Exploited by CVE-2014-4114 (OLE)
self.cur_file.add_log_details('embedded_obj', True)
self.cur_file.make_dangerous()
if len(doc.features.embedded_packages) > 0:
self.cur_file.add_log_details('embedded_pack', True)
self.cur_file.make_dangerous()
self._safe_copy()
def _libreoffice(self):
"""Processes a libreoffice file."""
self.cur_file.add_log_details('processing_type', 'libreoffice')
# As long as there ar no way to do a sanity check on the files => dangerous
try:
lodoc = zipfile.ZipFile(self.cur_file.src_path, 'r')
except:
self.cur_file.add_log_details('invalid', True)
self.cur_file.make_dangerous()
for f in lodoc.infolist():
fname = f.filename.lower()
if fname.startswith('script') or fname.startswith('basic') or \
fname.startswith('object') or fname.endswith('.bin'):
self.cur_file.add_log_details('macro', True)
self.cur_file.make_dangerous()
self._safe_copy()
def _pdf(self):
"""Processes a PDF file."""
self.cur_file.add_log_details('processing_type', 'pdf')
xmlDoc = PDFiD(self.cur_file.src_path)
oPDFiD = cPDFiD(xmlDoc, True)
# TODO: other keywords?
if oPDFiD.encrypt.count > 0:
self.cur_file.add_log_details('encrypted', True)
self.cur_file.make_dangerous()
if oPDFiD.js.count > 0 or oPDFiD.javascript.count > 0:
self.cur_file.add_log_details('javascript', True)
self.cur_file.make_dangerous()
if oPDFiD.aa.count > 0 or oPDFiD.openaction.count > 0:
self.cur_file.add_log_details('openaction', True)
self.cur_file.make_dangerous()
if oPDFiD.richmedia.count > 0:
self.cur_file.add_log_details('flash', True)
self.cur_file.make_dangerous()
if oPDFiD.launch.count > 0:
self.cur_file.add_log_details('launch', True)
self.cur_file.make_dangerous()
self._safe_copy()
def _archive(self):
"""Processes an archive using 7zip. The archive is extracted to a
temporary directory and self.process_dir is called on that directory.
The recursive archive depth is increased to protect against archive
bombs."""
self.cur_file.add_log_details('processing_type', 'archive')
self.cur_file.is_recursive = True
self.cur_file.log_string += 'Archive extracted, processing content.'
tmpdir = self.cur_file.dst_path + '_temp'
self._safe_mkdir(tmpdir)
extract_command = '{} -p1 x "{}" -o"{}" -bd -aoa'.format(SEVENZ_PATH, self.cur_file.src_path, tmpdir)
self._run_process(extract_command)
self.recursive_archive_depth += 1
self.logger.tree(tmpdir)
self.process_dir(tmpdir, self.cur_file.dst_path)
self.recursive_archive_depth -= 1
self._safe_rmtree(tmpdir)
def _handle_archivebomb(self, src_dir):
self.cur_file.make_dangerous()
self.cur_file.add_log_details('Archive Bomb', True)
self.log_name.warning('ARCHIVE BOMB.')
self.log_name.warning('The content of the archive contains recursively other archives.')
self.log_name.warning('This is a bad sign so the archive is not extracted to the destination key.')
self._safe_rmtree(src_dir)
if src_dir.endswith('_temp'):
bomb_path = src_dir[:-len('_temp')]
self._safe_remove(bomb_path)
def _unknown_app(self):
"""Processes an unknown file."""
self.cur_file.make_unknown()
self._safe_copy()
def _binary_app(self):
"""Processses an unknown binary file."""
self.cur_file.make_binary()
self._safe_copy()
#######################
# Metadata extractors
def _metadata_exif(self, metadata_file_path):
img = open(self.cur_file.src_path, 'rb')
tags = None
try:
tags = exifread.process_file(img, debug=True)
except Exception as e:
print("Error while trying to grab full metadata for file {}; retrying for partial data.".format(self.cur_file.src_path))
print(e)
if tags is None:
try:
tags = exifread.process_file(img, debug=True)
except Exception as e:
print("Failed to get any metadata for file {}.".format(self.cur_file.src_path))
print(e)
img.close()
return False
for tag in sorted(tags.keys()):
# These are long and obnoxious/binary
if tag not in ('JPEGThumbnail', 'TIFFThumbnail'):
printable = str(tags[tag])
# Exifreader truncates data.
if len(printable) > 25 and printable.endswith(", ... ]"):
value = tags[tag].values
if isinstance(value, str):
printable = value
else:
printable = str(value)
with open(metadata_file_path, 'w+') as metadata_file:
metadata_file.write("Key: {}\tValue: {}\n".format(tag, printable))
self.cur_file.add_log_details('metadata', 'exif')
img.close()
return True
def _metadata_png(self, metadata_file_path):
warnings.simplefilter('error', Image.DecompressionBombWarning)
try:
img = Image.open(self.cur_file.src_path)
for tag in sorted(img.info.keys()):
# These are long and obnoxious/binary
if tag not in ('icc_profile'):
with open(metadata_file_path, 'w+') as metadata_file:
metadata_file.write("Key: {}\tValue: {}\n".format(tag, img.info[tag]))
self.cur_file.add_log_details('metadata', 'png')
img.close()
# Catch decompression bombs
except Exception as e:
print("Caught exception processing metadata for {}".format(self.cur_file.src_path))
print(e)
self.cur_file.make_dangerous()
self._safe_copy()
return False
def extract_metadata(self):
metadata_file_path = self.cur_file.create_metadata_file(".metadata.txt")
mt = self.cur_file.mimetype
metadata_processing_method = self.metadata_mimetype_methods.get(mt)
if metadata_processing_method:
# TODO: should we return metadata and write it here instead of in processing method?
metadata_processing_method(metadata_file_path)
#######################
# ##### Media - audio and video aren't converted ######
def audio(self):
"""Processes an audio file."""
self.cur_file.log_string += 'Audio file'
self._media_processing()
def video(self):
"""Processes a video."""
self.cur_file.log_string += 'Video file'
self._media_processing()
def _media_processing(self):
"""Generic way to process all media files."""
self.cur_file.add_log_details('processing_type', 'media')
self._safe_copy()
def image(self):
"""Processes an image.
Extracts metadata if metadata is present. Creates a temporary
directory, opens the using PIL.Image, saves it to the temporary
directory, and copies it to the destination."""
if self.cur_file.has_metadata():
self.extract_metadata()
# FIXME make sure this works for png, gif, tiff
# Create a temp directory
dst_dir, filename = os.path.split(self.cur_file.dst_path)
tmpdir = os.path.join(dst_dir, 'temp')
tmppath = os.path.join(tmpdir, filename)
self._safe_mkdir(tmpdir)
# Do our image conversions
warnings.simplefilter('error', Image.DecompressionBombWarning)
try:
imIn = Image.open(self.cur_file.src_path)
imOut = Image.frombytes(imIn.mode, imIn.size, imIn.tobytes())
imOut.save(tmppath)
# Copy the file back out and cleanup
self._safe_copy(tmppath)
self._safe_rmtree(tmpdir)
# Catch decompression bombs
except Exception as e:
print("Caught exception (possible decompression bomb?) while translating file {}.".format(self.cur_file.src_path))
print(e)
self.cur_file.make_dangerous()
self._safe_copy()
self.cur_file.log_string += 'Image file'
self.cur_file.add_log_details('processing_type', 'image')
#######################
def process_file(self, srcpath, dstpath, relative_path):
self.cur_file = File(srcpath, dstpath, self.logger)
self.log_name.info('Processing {} ({}/{})',
relative_path,
self.cur_file.main_type,
self.cur_file.sub_type)
if not self.cur_file.is_dangerous():
self.mime_processing_options.get(self.cur_file.main_type, self.unknown)()
else:
self._safe_copy()
if not self.cur_file.is_recursive:
self._write_log()
def process_dir(self, src_dir, dst_dir):
"""Main function coordinating file processing."""
if self.recursive_archive_depth > 0:
self._write_log()
if self.recursive_archive_depth >= self.max_recursive_depth:
self._handle_archivebomb(src_dir)
for srcpath in self.list_all_files(src_dir):
dstpath = srcpath.replace(src_dir, dst_dir)
relative_path = srcpath.replace(src_dir + '/', '')
self.process_file(srcpath, dstpath, relative_path)
def run(self):
self.process_dir(self.src_root_dir, self.dst_root_dir)
def main(kg_implementation, description):
parser = argparse.ArgumentParser(prog='KittenGroomer', description=description)
parser.add_argument('-s', '--source', type=str, help='Source directory')
parser.add_argument('-d', '--destination', type=str, help='Destination directory')
args = parser.parse_args()
kg = kg_implementation(args.source, args.destination)
kg.run()
if __name__ == '__main__':
main(KittenGroomerFileCheck, 'File sanitizer used in CIRCLean. Renames potentially dangerous files.')