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python3.11/00397-tarfile-filter.patch

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Security fix for CVE-2007-4559 Resolves: rhbz#263261
2023-06-30 10:32:35 +00:00
From 363474312808642b23840a26b4e812051a551e48 Mon Sep 17 00:00:00 2001
From: Petr Viktorin <encukou@gmail.com>
Date: Mon, 6 Mar 2023 17:24:24 +0100
Subject: [PATCH] CVE-2007-4559, PEP-706: Add filters for tarfile extraction
(downstream)
Add and test RHEL-specific ways of configuring the default behavior: environment
variable and config file.
---
Lib/tarfile.py | 42 +++++++++++++
Lib/test/test_shutil.py | 3 +-
Lib/test/test_tarfile.py | 128 ++++++++++++++++++++++++++++++++++++++-
3 files changed, 169 insertions(+), 4 deletions(-)
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 130b5e0..3b7d8d5 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -72,6 +72,13 @@ __all__ = ["TarFile", "TarInfo", "is_tarfile", "TarError", "ReadError",
"ENCODING", "USTAR_FORMAT", "GNU_FORMAT", "PAX_FORMAT",
"DEFAULT_FORMAT", "open"]
+# If true, use the safer (but backwards-incompatible) 'tar' extraction filter,
+# rather than 'fully_trusted', by default.
+# The emitted warning is changed to match.
+_RH_SAFER_DEFAULT = True
+
+# System-wide configuration file
+_CONFIG_FILENAME = '/etc/python/tarfile.cfg'
#---------------------------------------------------------
# tar constants
@@ -2211,6 +2218,41 @@ class TarFile(object):
if filter is None:
filter = self.extraction_filter
if filter is None:
+ name = os.environ.get('PYTHON_TARFILE_EXTRACTION_FILTER')
+ if name is None:
+ try:
+ file = bltn_open(_CONFIG_FILENAME)
+ except FileNotFoundError:
+ pass
+ else:
+ import configparser
+ conf = configparser.ConfigParser(
+ interpolation=None,
+ comment_prefixes=('#', ),
+ )
+ with file:
+ conf.read_file(file)
+ name = conf.get('tarfile',
+ 'PYTHON_TARFILE_EXTRACTION_FILTER',
+ fallback='')
+ if name:
+ try:
+ filter = _NAMED_FILTERS[name]
+ except KeyError:
+ raise ValueError(f"filter {filter!r} not found") from None
+ self.extraction_filter = filter
+ return filter
+ if _RH_SAFER_DEFAULT:
+ warnings.warn(
+ 'The default behavior of tarfile extraction has been '
+ + 'changed to disallow common exploits '
+ + '(including CVE-2007-4559). '
+ + 'By default, absolute/parent paths are disallowed '
+ + 'and some mode bits are cleared. '
+ + 'See https://access.redhat.com/articles/7004769 '
+ + 'for more details.',
+ RuntimeWarning)
+ return tar_filter
return fully_trusted_filter
if isinstance(filter, str):
raise TypeError(
diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
index 9bf4145..f247b82 100644
--- a/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@ -1665,7 +1665,8 @@ class TestArchives(BaseTest, unittest.TestCase):
def check_unpack_tarball(self, format):
self.check_unpack_archive(format, filter='fully_trusted')
self.check_unpack_archive(format, filter='data')
- with warnings_helper.check_no_warnings(self):
+ with warnings_helper.check_warnings(
+ ('.*CVE-2007-4559', RuntimeWarning)):
self.check_unpack_archive(format)
def test_unpack_archive_tar(self):
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index cdea033..4724285 100644
--- a/Lib/test/test_tarfile.py
+++ b/Lib/test/test_tarfile.py
@@ -2,7 +2,7 @@ import sys
import os
import io
from hashlib import sha256
-from contextlib import contextmanager
+from contextlib import contextmanager, ExitStack
from random import Random
import pathlib
import shutil
@@ -2999,7 +2999,11 @@ class NoneInfoExtractTests(ReadTest):
tar = tarfile.open(tarname, mode='r', encoding="iso8859-1")
cls.control_dir = pathlib.Path(TEMPDIR) / "extractall_ctrl"
tar.errorlevel = 0
- tar.extractall(cls.control_dir, filter=cls.extraction_filter)
+ with ExitStack() as cm:
+ if cls.extraction_filter is None:
+ cm.enter_context(warnings.catch_warnings())
+ warnings.simplefilter(action="ignore", category=RuntimeWarning)
+ tar.extractall(cls.control_dir, filter=cls.extraction_filter)
tar.close()
cls.control_paths = set(
p.relative_to(cls.control_dir)
@@ -3674,7 +3678,8 @@ class TestExtractionFilters(unittest.TestCase):
"""Ensure the default filter does not warn (like in 3.12)"""
with ArchiveMaker() as arc:
arc.add('foo')
- with warnings_helper.check_no_warnings(self):
+ with warnings_helper.check_warnings(
+ ('.*CVE-2007-4559', RuntimeWarning)):
with self.check_context(arc.open(), None):
self.expect_file('foo')
@@ -3844,6 +3849,123 @@ class TestExtractionFilters(unittest.TestCase):
self.expect_exception(TypeError) # errorlevel is not int
+ @contextmanager
+ def rh_config_context(self, config_lines=None):
+ """Set up for testing various ways of overriding the default filter
+
+ return a triple with:
+ - temporary directory
+ - EnvironmentVarGuard()
+ - a test archive for use with check_* methods below
+
+ If config_lines is given, write them to the config file. Otherwise
+ the config file is missing.
+ """
+ tempdir = pathlib.Path(TEMPDIR) / 'tmp'
+ configfile = tempdir / 'tarfile.cfg'
+ with ArchiveMaker() as arc:
+ arc.add('good')
+ arc.add('ugly', symlink_to='/etc/passwd')
+ arc.add('../bad')
+ with (
+ os_helper.temp_dir(tempdir),
+ support.swap_attr(tarfile, '_CONFIG_FILENAME', str(configfile)),
+ os_helper.EnvironmentVarGuard() as env,
+ arc.open() as tar,
+ ):
+ if config_lines is not None:
+ with configfile.open('w') as f:
+ for line in config_lines:
+ print(line, file=f)
+ yield tempdir, env, tar
+
+ def check_rh_default_behavior(self, tar, tempdir):
+ """Check RH default: warn and refuse to extract dangerous files."""
+ with (
+ warnings_helper.check_warnings(
+ ('.*CVE-2007-4559', RuntimeWarning)),
+ self.assertRaises(tarfile.OutsideDestinationError),
+ ):
+ tar.extractall(tempdir / 'outdir')
+
+ def check_trusted_default(self, tar, tempdir):
+ """Check 'fully_trusted' is configured as the default filter."""
+ with (
+ warnings_helper.check_no_warnings(self),
+ ):
+ tar.extractall(tempdir / 'outdir')
+ self.assertTrue((tempdir / 'outdir/good').exists())
+ self.assertEqual((tempdir / 'outdir/ugly').readlink(),
+ pathlib.Path('/etc/passwd'))
+ self.assertTrue((tempdir / 'bad').exists())
+
+ def test_rh_default_no_conf(self):
+ with self.rh_config_context() as (tempdir, env, tar):
+ self.check_rh_default_behavior(tar, tempdir)
+
+ def test_rh_default_from_file(self):
+ lines = ['[tarfile]', 'PYTHON_TARFILE_EXTRACTION_FILTER=fully_trusted']
+ with self.rh_config_context(lines) as (tempdir, env, tar):
+ self.check_trusted_default(tar, tempdir)
+
+ def test_rh_empty_config_file(self):
+ """Empty config file -> default behavior"""
+ lines = []
+ with self.rh_config_context(lines) as (tempdir, env, tar):
+ self.check_rh_default_behavior(tar, tempdir)
+
+ def test_empty_config_section(self):
+ """Empty section in config file -> default behavior"""
+ lines = ['[tarfile]']
+ with self.rh_config_context(lines) as (tempdir, env, tar):
+ self.check_rh_default_behavior(tar, tempdir)
+
+ def test_rh_default_empty_config_option(self):
+ """Empty option value in config file -> default behavior"""
+ lines = ['[tarfile]', 'PYTHON_TARFILE_EXTRACTION_FILTER=']
+ with self.rh_config_context(lines) as (tempdir, env, tar):
+ self.check_rh_default_behavior(tar, tempdir)
+
+ def test_bad_config_option(self):
+ """Bad option value in config file -> ValueError"""
+ lines = ['[tarfile]', 'PYTHON_TARFILE_EXTRACTION_FILTER=unknown!']
+ with self.rh_config_context(lines) as (tempdir, env, tar):
+ with self.assertRaises(ValueError):
+ tar.extractall(tempdir / 'outdir')
+
+ def test_default_from_envvar(self):
+ with self.rh_config_context() as (tempdir, env, tar):
+ env['PYTHON_TARFILE_EXTRACTION_FILTER'] = 'fully_trusted'
+ self.check_trusted_default(tar, tempdir)
+
+ def test_empty_envvar(self):
+ """Empty env variable -> default behavior"""
+ with self.rh_config_context() as (tempdir, env, tar):
+ env['PYTHON_TARFILE_EXTRACTION_FILTER'] = ''
+ self.check_rh_default_behavior(tar, tempdir)
+
+ def test_bad_envvar(self):
+ with self.rh_config_context() as (tempdir, env, tar):
+ env['PYTHON_TARFILE_EXTRACTION_FILTER'] = 'unknown!'
+ with self.assertRaises(ValueError):
+ tar.extractall(tempdir / 'outdir')
+
+ def test_envvar_overrides_file(self):
+ lines = ['[tarfile]', 'PYTHON_TARFILE_EXTRACTION_FILTER=data']
+ with self.rh_config_context(lines) as (tempdir, env, tar):
+ env['PYTHON_TARFILE_EXTRACTION_FILTER'] = 'fully_trusted'
+ self.check_trusted_default(tar, tempdir)
+
+ def test_monkeypatch_overrides_envvar(self):
+ with self.rh_config_context(None) as (tempdir, env, tar):
+ env['PYTHON_TARFILE_EXTRACTION_FILTER'] = 'data'
+ with support.swap_attr(
+ tarfile.TarFile, 'extraction_filter',
+ staticmethod(tarfile.fully_trusted_filter)
+ ):
+ self.check_trusted_default(tar, tempdir)
+
+
def setUpModule():
os_helper.unlink(TEMPDIR)
os.makedirs(TEMPDIR)
--
2.41.0
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