python/samba/safe_tarfile.py

   1 # Unix SMB/CIFS implementation.
   2 # Copyright (C) Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
   3 #
   4 # This program is free software; you can redistribute it and/or modify
   5 # it under the terms of the GNU General Public License as published by
   6 # the Free Software Foundation; either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17
  18 import os
  19 import tarfile
  20 from pathlib import Path
  21 from tarfile import ExtractError, TarFile as UnsafeTarFile
  22
  23
  24 class TarFile(UnsafeTarFile):
  25     """This TarFile implementation is trying to ameliorate CVE-2007-4559,
  26     where tarfile.TarFiles can step outside of the target directory
  27     using '../../'.
  28     """
  29
  30     try:
  31         # New in version 3.11.4 (also has been backported)
  32         # https://docs.python.org/3/library/tarfile.html#tarfile.TarFile.extraction_filter
  33         # https://peps.python.org/pep-0706/
  34         extraction_filter = staticmethod(tarfile.tar_filter)
  35     except AttributeError:
  36         def extract(self, member, path="", set_attrs=True, *,
  37                     numeric_owner=False):
  38             self._safetarfile_check()
  39             super().extract(member, path, set_attrs=set_attrs,
  40                             numeric_owner=numeric_owner)
  41
  42         def extractall(self, path, members=None, *, numeric_owner=False):
  43             self._safetarfile_check()
  44             super().extractall(path, members,
  45                                numeric_owner=numeric_owner)
  46
  47         def _safetarfile_check(self):
  48             for tarinfo in self.__iter__():
  49                 if self._is_traversal_attempt(tarinfo=tarinfo):
  50                     raise ExtractError(
  51                         "Attempted directory traversal for "
  52                         f"member: {tarinfo.name}")
  53                 if self._is_unsafe_symlink(tarinfo=tarinfo):
  54                     raise ExtractError(
  55                         "Attempted directory traversal via symlink for "
  56                         f"member: {tarinfo.linkname}")
  57                 if self._is_unsafe_link(tarinfo=tarinfo):
  58                     raise ExtractError(
  59                         "Attempted directory traversal via link for "
  60                         f"member: {tarinfo.linkname}")
  61
  62         def _resolve_path(self, path):
  63             return os.path.realpath(os.path.abspath(path))
  64
  65         def _is_path_in_dir(self, path, basedir):
  66             return self._resolve_path(os.path.join(basedir,
  67                                       path)).startswith(basedir)
  68
  69         def _is_traversal_attempt(self, tarinfo):
  70             if (tarinfo.name.startswith(os.sep)
  71                or ".." + os.sep in tarinfo.name):
  72                 return True
  73             return False
  74
  75         def _is_unsafe_symlink(self, tarinfo):
  76             if tarinfo.issym():
  77                 symlink_file = Path(
  78                     os.path.normpath(os.path.join(os.getcwd(),
  79                                      tarinfo.linkname)))
  80                 if not self._is_path_in_dir(symlink_file, os.getcwd()):
  81                     return True
  82             return False
  83
  84         def _is_unsafe_link(self, tarinfo):
  85             if tarinfo.islnk():
  86                 link_file = Path(
  87                     os.path.normpath(os.path.join(os.getcwd(),
  88                                                   tarinfo.linkname)))
  89                 if not self._is_path_in_dir(link_file, os.getcwd()):
  90                     return True
  91             return False
  92
  93
  94 open = TarFile.open