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python-Django
CVE-2021-31542.patch
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File CVE-2021-31542.patch of Package python-Django
commit 8f122c009eb4ade5d253504035df1fa5850a076e Author: Florian Apolloner <florian@apolloner.eu> Date: Wed Apr 14 18:23:44 2021 +0200 [2.2.x] Fixed CVE-2021-31542 -- Tightened path & file name sanitation in file uploads. (cherry picked from commit 04ac1624bdc2fa737188401757cf95ced122d26d) (cherry picked from commit c2c3c23bdeacea4d5f78892f94270068870d6a54) diff --git a/django/core/files/storage.py b/django/core/files/storage.py index df92f0af8a28..6e27ade9b7d7 100644 --- a/django/core/files/storage.py +++ b/django/core/files/storage.py @@ -1,5 +1,6 @@ import errno import os +import pathlib import warnings from datetime import datetime @@ -7,6 +8,7 @@ from django.conf import settings from django.core.exceptions import SuspiciousFileOperation from django.core.files import File, locks from django.core.files.move import file_move_safe +from django.core.files.utils import validate_file_name from django.utils._os import abspathu, safe_join from django.utils.crypto import get_random_string from django.utils.deconstruct import deconstructible @@ -77,6 +79,9 @@ class Storage(object): available for new content to be written to. """ dir_name, file_name = os.path.split(name) + if '..' in pathlib.PurePath(dir_name).parts: + raise SuspiciousFileOperation("Detected path traversal attempt in '%s'" % dir_name) + validate_file_name(file_name) file_root, file_ext = os.path.splitext(file_name) # If the filename already exists, add an underscore and a random 7 # character alphanumeric string (before the file extension, if one @@ -109,6 +114,8 @@ class Storage(object): """ # `filename` may include a path as returned by FileField.upload_to. dirname, filename = os.path.split(filename) + if '..' in pathlib.PurePath(dirname).parts: + raise SuspiciousFileOperation("Detected path traversal attempt in '%s'" % dirname) return os.path.normpath(os.path.join(dirname, self.get_valid_name(filename))) def path(self, name): diff --git a/django/core/files/uploadedfile.py b/django/core/files/uploadedfile.py index 20eaecea755d..bcd438d39337 100644 --- a/django/core/files/uploadedfile.py +++ b/django/core/files/uploadedfile.py @@ -9,6 +9,7 @@ from io import BytesIO from django.conf import settings from django.core.files import temp as tempfile from django.core.files.base import File +from django.core.files.utils import validate_file_name from django.utils.encoding import force_str __all__ = ('UploadedFile', 'TemporaryUploadedFile', 'InMemoryUploadedFile', @@ -51,6 +52,8 @@ class UploadedFile(File): ext = ext[:255] name = name[:255 - len(ext)] + ext + name = validate_file_name(name) + self._name = name name = property(_get_name, _set_name) diff --git a/django/core/files/utils.py b/django/core/files/utils.py index 8cc212fe1fae..1e14c677edae 100644 --- a/django/core/files/utils.py +++ b/django/core/files/utils.py @@ -1,3 +1,19 @@ +import os + +from django.core.exceptions import SuspiciousFileOperation + + +def validate_file_name(name): + if name != os.path.basename(name): + raise SuspiciousFileOperation("File name '%s' includes path elements" % name) + + # Remove potentially dangerous names + if name in {'', '.', '..'}: + raise SuspiciousFileOperation("Could not derive file name from '%s'" % name) + + return name + + class FileProxyMixin(object): """ A mixin class used to forward file methods to an underlaying file diff --git a/django/db/models/fields/files.py b/django/db/models/fields/files.py index 20374ba8e69a..011a0040bf7e 100644 --- a/django/db/models/fields/files.py +++ b/django/db/models/fields/files.py @@ -8,6 +8,7 @@ from django.core import checks from django.core.files.base import File from django.core.files.images import ImageFile from django.core.files.storage import default_storage +from django.core.files.utils import validate_file_name from django.db.models import signals from django.db.models.fields import Field from django.utils import six @@ -343,6 +344,7 @@ class FileField(Field): Until the storage layer, all file paths are expected to be Unix style (with forward slashes). """ + filename = validate_file_name(filename) if callable(self.upload_to): filename = self.upload_to(instance, filename) else: diff --git a/django/http/multipartparser.py b/django/http/multipartparser.py index 176f953b5cd3..396a2bcd995a 100644 --- a/django/http/multipartparser.py +++ b/django/http/multipartparser.py @@ -9,7 +9,7 @@ from __future__ import unicode_literals import base64 import binascii import cgi -import os +import HTMLParser import sys from django.conf import settings @@ -21,7 +21,6 @@ from django.utils import six from django.utils.datastructures import MultiValueDict from django.utils.encoding import force_text from django.utils.six.moves.urllib.parse import unquote -from django.utils.text import unescape_entities __all__ = ('MultiPartParser', 'MultiPartParserError', 'InputStreamExhausted') @@ -277,10 +276,25 @@ class MultiPartParser(object): break def sanitize_file_name(self, file_name): - file_name = unescape_entities(file_name) - # Cleanup Windows-style path separators. - file_name = file_name[file_name.rfind('\\') + 1:].strip() - return os.path.basename(file_name) + """ + Sanitize the filename of an upload. + + Remove all possible path separators, even though that might remove more + than actually required by the target system. Filenames that could + potentially cause problems (current/parent dir) are also discarded. + + It should be noted that this function could still return a "filepath" + like "C:some_file.txt" which is handled later on by the storage layer. + So while this function does sanitize filenames to some extent, the + resulting filename should still be considered as untrusted user input. + """ + file_name = HTMLParser.HTMLParser().unescape(file_name) + file_name = file_name.rsplit('/')[-1] + file_name = file_name.rsplit('\\')[-1] + + if file_name in {'', '.', '..'}: + return None + return file_name IE_sanitize = sanitize_file_name diff --git a/django/utils/text.py b/django/utils/text.py index db7b5e00ad0c..fad5b18818c1 100644 --- a/django/utils/text.py +++ b/django/utils/text.py @@ -6,6 +6,7 @@ import warnings from gzip import GzipFile from io import BytesIO +from django.core.exceptions import SuspiciousFileOperation from django.utils import six from django.utils.deprecation import RemovedInDjango19Warning from django.utils.encoding import force_text @@ -231,7 +232,7 @@ class Truncator(SimpleLazyObject): return out -def get_valid_filename(s): +def get_valid_filename(name): """ Returns the given string converted to a string that can be used for a clean filename. Specifically, leading and trailing spaces are removed; other @@ -240,8 +241,11 @@ def get_valid_filename(s): >>> get_valid_filename("john's portrait in 2004.jpg") 'johns_portrait_in_2004.jpg' """ - s = force_text(s).strip().replace(' ', '_') - return re.sub(r'(?u)[^-\w.]', '', s) + s = str(name).strip().replace(' ', '_') + s = re.sub(r'(?u)[^-\w.]', '', s) + if s in {'', '.', '..'}: + raise SuspiciousFileOperation("Could not derive file name from '%s'" % name) + return s get_valid_filename = allow_lazy(get_valid_filename, six.text_type) diff --git a/docs/releases/2.2.21.txt b/docs/releases/2.2.21.txt new file mode 100644 index 000000000000..f32aeadff767 --- /dev/null +++ b/docs/releases/2.2.21.txt @@ -0,0 +1,17 @@ +=========================== +Django 2.2.21 release notes +=========================== + +*May 4, 2021* + +Django 2.2.21 fixes a security issue in 2.2.20. + +CVE-2021-31542: Potential directory-traversal via uploaded files +================================================================ + +``MultiPartParser``, ``UploadedFile``, and ``FieldFile`` allowed +directory-traversal via uploaded files with suitably crafted file names. + +In order to mitigate this risk, stricter basename and path sanitation is now +applied. Specifically, empty file names and paths with dot segments will be +rejected. diff --git a/tests/file_storage/test_generate_filename.py b/tests/file_storage/test_generate_filename.py index 44320138509b..6f79da39278e 100644 --- a/tests/file_storage/test_generate_filename.py +++ b/tests/file_storage/test_generate_filename.py @@ -1,8 +1,9 @@ import os import warnings +from django.core.exceptions import SuspiciousFileOperation from django.core.files.base import ContentFile -from django.core.files.storage import Storage +from django.core.files.storage import FileSystemStorage, Storage from django.db.models import FileField from django.test import SimpleTestCase @@ -37,6 +38,44 @@ class AWSS3Storage(Storage): class GenerateFilenameStorageTests(SimpleTestCase): + def test_storage_dangerous_paths(self): + candidates = [ + ('/tmp/..', '..'), + ('/tmp/.', '.'), + ('', ''), + ] + s = FileSystemStorage() + msg = "Could not derive file name from '%s'" + for file_name, base_name in candidates: + with self.subTest(file_name=file_name): + with self.assertRaisesMessage(SuspiciousFileOperation, msg % base_name): + s.get_available_name(file_name) + with self.assertRaisesMessage(SuspiciousFileOperation, msg % base_name): + s.generate_filename(file_name) + + def test_storage_dangerous_paths_dir_name(self): + file_name = '/tmp/../path' + s = FileSystemStorage() + msg = "Detected path traversal attempt in '/tmp/..'" + with self.assertRaisesMessage(SuspiciousFileOperation, msg): + s.get_available_name(file_name) + with self.assertRaisesMessage(SuspiciousFileOperation, msg): + s.generate_filename(file_name) + + def test_filefield_dangerous_filename(self): + candidates = ['..', '.', '', '???', '$.$.$'] + f = FileField(upload_to='some/folder/') + msg = "Could not derive file name from '%s'" + for file_name in candidates: + with self.subTest(file_name=file_name): + with self.assertRaisesMessage(SuspiciousFileOperation, msg % file_name): + f.generate_filename(None, file_name) + + def test_filefield_dangerous_filename_dir(self): + f = FileField(upload_to='some/folder/') + msg = "File name '/tmp/path' includes path elements" + with self.assertRaisesMessage(SuspiciousFileOperation, msg): + f.generate_filename(None, '/tmp/path') def test_filefield_get_directory_deprecation(self): with warnings.catch_warnings(record=True) as warns: diff --git a/tests/file_uploads/tests.py b/tests/file_uploads/tests.py index d08bc8016eda..fbda6995021b 100644 --- a/tests/file_uploads/tests.py +++ b/tests/file_uploads/tests.py @@ -10,8 +10,9 @@ import shutil import tempfile as sys_tempfile import unittest +from django.core.exceptions import SuspiciousFileOperation from django.core.files import temp as tempfile -from django.core.files.uploadedfile import SimpleUploadedFile +from django.core.files.uploadedfile import SimpleUploadedFile, UploadedFile from django.http.multipartparser import MultiPartParser, parse_header from django.test import TestCase, client, override_settings from django.utils.encoding import force_bytes @@ -40,6 +41,16 @@ CANDIDATE_TRAVERSAL_FILE_NAMES = [ '../hax0rd.txt', # HTML entities. ] +CANDIDATE_INVALID_FILE_NAMES = [ + '/tmp/', # Directory, *nix-style. + 'c:\\tmp\\', # Directory, win-style. + '/tmp/.', # Directory dot, *nix-style. + 'c:\\tmp\\.', # Directory dot, *nix-style. + '/tmp/..', # Parent directory, *nix-style. + 'c:\\tmp\\..', # Parent directory, win-style. + '', # Empty filename. +] + @override_settings(MEDIA_ROOT=MEDIA_ROOT, ROOT_URLCONF='file_uploads.urls', MIDDLEWARE_CLASSES=()) class FileUploadTests(TestCase): @@ -55,6 +66,22 @@ class FileUploadTests(TestCase): shutil.rmtree(MEDIA_ROOT) super(FileUploadTests, cls).tearDownClass() + def test_upload_name_is_validated(self): + candidates = [ + '/tmp/', + '/tmp/..', + '/tmp/.', + ] + if sys.platform == 'win32': + candidates.extend([ + 'c:\\tmp\\', + 'c:\\tmp\\..', + 'c:\\tmp\\.', + ]) + for file_name in candidates: + with self.subTest(file_name=file_name): + self.assertRaises(SuspiciousFileOperation, UploadedFile, name=file_name) + def test_simple_upload(self): with open(__file__, 'rb') as fp: post_data = { @@ -638,6 +665,15 @@ class MultiParserTests(unittest.TestCase): with self.subTest(file_name=file_name): self.assertEqual(parser.sanitize_file_name(file_name), 'hax0rd.txt') + def test_sanitize_invalid_file_name(self): + parser = MultiPartParser({ + 'CONTENT_TYPE': 'multipart/form-data; boundary=_foo', + 'CONTENT_LENGTH': '1', + }, StringIO('x'), [], 'utf-8') + for file_name in CANDIDATE_INVALID_FILE_NAMES: + with self.subTest(file_name=file_name): + self.assertIsNone(parser.sanitize_file_name(file_name)) + def test_rfc2231_parsing(self): test_data = ( (b"Content-Type: application/x-stuff; title*=us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A", diff --git a/tests/utils_tests/test_text.py b/tests/utils_tests/test_text.py index 5fe66e7b900b..c3dcbf42f8fd 100644 --- a/tests/utils_tests/test_text.py +++ b/tests/utils_tests/test_text.py @@ -5,6 +5,7 @@ import json import warnings from unittest import skipUnless +from django.core.exceptions import SuspiciousFileOperation from django.test import SimpleTestCase, ignore_warnings from django.test.utils import reset_warning_registry from django.utils import six, text @@ -217,6 +218,13 @@ class TestUtilsText(SimpleTestCase): def test_get_valid_filename(self): filename = "^&'@{}[],$=!-#()%+~_123.txt" self.assertEqual(text.get_valid_filename(filename), "-_123.txt") + msg = "Could not derive file name from '???'" + with self.assertRaisesMessage(SuspiciousFileOperation, msg): + text.get_valid_filename('???') + # After sanitizing this would yield '..'. + msg = "Could not derive file name from '$.$.$'" + with self.assertRaisesMessage(SuspiciousFileOperation, msg): + text.get_valid_filename('$.$.$') def test_compress_sequence(self): data = [{'key': i} for i in range(10)]
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