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python-Django.34948
CVE-2023-24580-DOS_file_upload.patch
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File CVE-2023-24580-DOS_file_upload.patch of Package python-Django.34948
From a665ed5179f5bbd3db95ce67286d0192eff041d8 Mon Sep 17 00:00:00 2001 From: Markus Holtermann <info@markusholtermann.eu> Date: Tue, 13 Dec 2022 10:27:39 +0100 Subject: [PATCH] [3.2.x] Fixed CVE-2023-24580 -- Prevented DoS with too many uploaded files. Thanks to Jakob Ackermann for the report. --- django/conf/global_settings.py | 4 + django/core/exceptions.py | 9 ++++ django/core/handlers/exception.py | 4 - django/http/multipartparser.py | 62 +++++++++++++++++++++++----- django/http/request.py | 6 +- docs/ref/exceptions.txt | 5 ++ docs/ref/settings.txt | 23 ++++++++++ tests/handlers/test_exception.py | 28 ++++++++++++ tests/requests/test_data_upload_settings.py | 51 ++++++++++++++++++++++- 9 files changed, 175 insertions(+), 17 deletions(-) --- a/django/conf/global_settings.py +++ b/django/conf/global_settings.py @@ -303,6 +303,10 @@ DATA_UPLOAD_MAX_MEMORY_SIZE = 2621440 # # SuspiciousOperation (TooManyFieldsSent) is raised. DATA_UPLOAD_MAX_NUMBER_FIELDS = 1000 +# Maximum number of files encoded in a multipart upload that will be read +# before a SuspiciousOperation (TooManyFilesSent) is raised. +DATA_UPLOAD_MAX_NUMBER_FILES = 100 + # Directory in which upload streamed files will be temporarily saved. A value of # `None` will make Django use the operating system's default temporary directory # (i.e. "/tmp" on *nix systems). --- a/django/core/exceptions.py +++ b/django/core/exceptions.py @@ -55,6 +55,15 @@ class TooManyFieldsSent(SuspiciousOperat pass +class TooManyFilesSent(SuspiciousOperation): + """ + The number of fields in a GET or POST request exceeded + settings.DATA_UPLOAD_MAX_NUMBER_FILES. + """ + + pass + + class RequestDataTooBig(SuspiciousOperation): """ The size of the request (excluding any file uploads) exceeded --- a/django/core/handlers/exception.py +++ b/django/core/handlers/exception.py @@ -6,7 +6,7 @@ from django.conf import settings from django.core import signals from django.core.exceptions import ( PermissionDenied, RequestDataTooBig, SuspiciousOperation, - TooManyFieldsSent, + TooManyFieldsSent, TooManyFilesSent, ) from django.http import Http404 from django.http.multipartparser import MultiPartParserError @@ -61,7 +61,7 @@ def response_for_exception(request, exc) response = get_exception_response(request, get_resolver(get_urlconf()), 400, exc) elif isinstance(exc, SuspiciousOperation): - if isinstance(exc, (RequestDataTooBig, TooManyFieldsSent)): + if isinstance(exc, (RequestDataTooBig, TooManyFieldsSent, TooManyFilesSent)): # POST data can't be accessed again, otherwise the original # exception would be raised. request._mark_post_parse_error() --- a/django/http/multipartparser.py +++ b/django/http/multipartparser.py @@ -12,6 +12,7 @@ from urllib.parse import unquote from django.conf import settings from django.core.exceptions import ( RequestDataTooBig, SuspiciousMultipartForm, TooManyFieldsSent, + TooManyFilesSent, ) from django.core.files.uploadhandler import ( SkipFile, StopFutureHandlers, StopUpload, @@ -37,6 +38,7 @@ class InputStreamExhausted(Exception): RAW = "raw" FILE = "file" FIELD = "field" +FIELD_TYPES = frozenset([FIELD, RAW]) class MultiPartParser: @@ -98,6 +100,22 @@ class MultiPartParser: self._upload_handlers = upload_handlers def parse(self): + # Call the actual parse routine and close all open files in case of + # errors. This is needed because if exceptions are thrown the + # MultiPartParser will not be garbage collected immediately and + # resources would be kept alive. This is only needed for errors because + # the Request object closes all uploaded files at the end of the + # request. + try: + return self._parse() + except Exception: + if hasattr(self, "_files"): + for _, files in self._files.lists(): + for fileobj in files: + fileobj.close() + raise + + def _parse(self): """ Parse the POST data and break it into a FILES MultiValueDict and a POST MultiValueDict. @@ -143,6 +161,8 @@ class MultiPartParser: num_bytes_read = 0 # To count the number of keys in the request. num_post_keys = 0 + # To count the number of files in the request. + num_files = 0 # To limit the amount of data read from the request. read_size = None @@ -155,6 +175,20 @@ class MultiPartParser: self.handle_file_complete(old_field_name, counters) old_field_name = None + if ( + item_type in FIELD_TYPES and + settings.DATA_UPLOAD_MAX_NUMBER_FIELDS is not None + ): + # Avoid storing more than DATA_UPLOAD_MAX_NUMBER_FIELDS. + num_post_keys += 1 + # 2 accounts for empty raw fields before and after the + # last boundary. + if settings.DATA_UPLOAD_MAX_NUMBER_FIELDS + 2 < num_post_keys: + raise TooManyFieldsSent( + "The number of GET/POST parameters exceeded " + "settings.DATA_UPLOAD_MAX_NUMBER_FIELDS." + ) + try: disposition = meta_data['content-disposition'][1] field_name = disposition['name'].strip() @@ -167,15 +201,6 @@ class MultiPartParser: field_name = force_text(field_name, encoding, errors='replace') if item_type == FIELD: - # Avoid storing more than DATA_UPLOAD_MAX_NUMBER_FIELDS. - num_post_keys += 1 - if (settings.DATA_UPLOAD_MAX_NUMBER_FIELDS is not None and - settings.DATA_UPLOAD_MAX_NUMBER_FIELDS < num_post_keys): - raise TooManyFieldsSent( - 'The number of GET/POST parameters exceeded ' - 'settings.DATA_UPLOAD_MAX_NUMBER_FIELDS.' - ) - # Avoid reading more than DATA_UPLOAD_MAX_MEMORY_SIZE. if settings.DATA_UPLOAD_MAX_MEMORY_SIZE is not None: read_size = settings.DATA_UPLOAD_MAX_MEMORY_SIZE - num_bytes_read @@ -201,6 +226,16 @@ class MultiPartParser: self._post.appendlist(field_name, force_text(data, encoding, errors='replace')) elif item_type == FILE: + # Avoid storing more than DATA_UPLOAD_MAX_NUMBER_FILES. + num_files += 1 + if ( + settings.DATA_UPLOAD_MAX_NUMBER_FILES is not None and + num_files > settings.DATA_UPLOAD_MAX_NUMBER_FILES + ): + raise TooManyFilesSent( + "The number of files exceeded " + "settings.DATA_UPLOAD_MAX_NUMBER_FILES." + ) # This is a file, use the handler... file_name = disposition.get('filename') if file_name: @@ -266,8 +301,13 @@ class MultiPartParser: # Handle file upload completions on next iteration. old_field_name = field_name else: - # If this is neither a FIELD or a FILE, just exhaust the stream. - exhaust(stream) + # If this is neither a FIELD nor a FILE, exhaust the field + # stream. Note: There could be an error here at some point, + # but there will be at least two RAW types (before and + # after the other boundaries). This branch is usually not + # reached at all, because a missing content-disposition + # header will skip the whole boundary. + exhaust(field_stream) except StopUpload as e: self._close_files() if not e.connection_reset: --- a/django/http/request.py +++ b/django/http/request.py @@ -11,7 +11,9 @@ from django.core.exceptions import ( DisallowedHost, ImproperlyConfigured, RequestDataTooBig, ) from django.core.files import uploadhandler -from django.http.multipartparser import MultiPartParser, MultiPartParserError +from django.http.multipartparser import ( + MultiPartParser, MultiPartParserError, TooManyFilesSent, +) from django.utils.datastructures import ImmutableList, MultiValueDict from django.utils.deprecation import RemovedInDjango30Warning from django.utils.encoding import escape_uri_path, force_bytes, iri_to_uri @@ -288,7 +290,7 @@ class HttpRequest: data = self try: self._post, self._files = self.parse_file_upload(self.META, data) - except MultiPartParserError: + except (MultiPartParserError, TooManyFilesSent): # An error occurred while parsing POST data. Since when # formatting the error the request handler might access # self.POST, set self._post and self._file to prevent --- a/docs/ref/exceptions.txt +++ b/docs/ref/exceptions.txt @@ -88,12 +88,17 @@ Django core exception classes are define * ``SuspiciousMultipartForm`` * ``SuspiciousSession`` * ``TooManyFieldsSent`` + * ``TooManyFilesSent`` If a ``SuspiciousOperation`` exception reaches the WSGI handler level it is logged at the ``Error`` level and results in a :class:`~django.http.HttpResponseBadRequest`. See the :doc:`logging documentation </topics/logging/>` for more information. +.. versionchanged:: 3.2.18 + + ``SuspiciousOperation`` is raised when too many files are submitted. + ``PermissionDenied`` -------------------- --- a/docs/ref/settings.txt +++ b/docs/ref/settings.txt @@ -1004,6 +1004,28 @@ could be used as a denial-of-service att servers don't typically perform deep request inspection, it's not possible to perform a similar check at that level. +.. setting:: DATA_UPLOAD_MAX_NUMBER_FILES + +``DATA_UPLOAD_MAX_NUMBER_FILES`` +-------------------------------- + +.. versionadded:: 3.2.18 + +Default: ``100`` + +The maximum number of files that may be received via POST in a +``multipart/form-data`` encoded request before a +:exc:`~django.core.exceptions.SuspiciousOperation` (``TooManyFiles``) is +raised. You can set this to ``None`` to disable the check. Applications that +are expected to receive an unusually large number of file fields should tune +this setting. + +The number of accepted files is correlated to the amount of time and memory +needed to process the request. Large requests could be used as a +denial-of-service attack vector if left unchecked. Since web servers don't +typically perform deep request inspection, it's not possible to perform a +similar check at that level. + .. setting:: DATABASE_ROUTERS ``DATABASE_ROUTERS`` @@ -3430,6 +3452,7 @@ HTTP ---- * :setting:`DATA_UPLOAD_MAX_MEMORY_SIZE` * :setting:`DATA_UPLOAD_MAX_NUMBER_FIELDS` +* :setting:`DATA_UPLOAD_MAX_NUMBER_FILES` * :setting:`DEFAULT_CHARSET` * :setting:`DEFAULT_CONTENT_TYPE` * :setting:`DISALLOWED_USER_AGENTS` --- a/tests/handlers/test_exception.py +++ b/tests/handlers/test_exception.py @@ -1,6 +1,8 @@ from django.core.handlers.wsgi import WSGIHandler from django.test import SimpleTestCase, override_settings -from django.test.client import FakePayload +from django.test.client import ( + BOUNDARY, MULTIPART_CONTENT, FakePayload, encode_multipart, +) class ExceptionHandlerTests(SimpleTestCase): @@ -25,3 +27,27 @@ class ExceptionHandlerTests(SimpleTestCa def test_data_upload_max_number_fields_exceeded(self): response = WSGIHandler()(self.get_suspicious_environ(), lambda *a, **k: None) self.assertEqual(response.status_code, 400) + + @override_settings(DATA_UPLOAD_MAX_NUMBER_FILES=2) + def test_data_upload_max_number_files_exceeded(self): + payload = FakePayload( + encode_multipart( + BOUNDARY, + { + "a.txt": "Hello World!", + "b.txt": "Hello Django!", + "c.txt": "Hello Python!", + }, + ) + ) + environ = { + "REQUEST_METHOD": "POST", + "CONTENT_TYPE": MULTIPART_CONTENT, + "CONTENT_LENGTH": len(payload), + "wsgi.input": payload, + "SERVER_NAME": "test", + "SERVER_PORT": "8000", + } + + response = WSGIHandler()(environ, lambda *a, **k: None) + self.assertEqual(response.status_code, 400) --- a/tests/requests/test_data_upload_settings.py +++ b/tests/requests/test_data_upload_settings.py @@ -1,11 +1,14 @@ from io import BytesIO -from django.core.exceptions import RequestDataTooBig, TooManyFieldsSent +from django.core.exceptions import ( + RequestDataTooBig, TooManyFieldsSent, TooManyFilesSent, +) from django.core.handlers.wsgi import WSGIRequest from django.test import SimpleTestCase from django.test.client import FakePayload TOO_MANY_FIELDS_MSG = 'The number of GET/POST parameters exceeded settings.DATA_UPLOAD_MAX_NUMBER_FIELDS.' +TOO_MANY_FILES_MSG = 'The number of files exceeded settings.DATA_UPLOAD_MAX_NUMBER_FILES.' TOO_MUCH_DATA_MSG = 'Request body exceeded settings.DATA_UPLOAD_MAX_MEMORY_SIZE.' @@ -166,6 +169,52 @@ class DataUploadMaxNumberOfFieldsMultipa self.request._load_post_and_files() +class DataUploadMaxNumberOfFilesMultipartPost(SimpleTestCase): + def setUp(self): + payload = FakePayload( + "\r\n".join( + [ + "--boundary", + ( + 'Content-Disposition: form-data; name="name1"; ' + 'filename="name1.txt"' + ), + "", + "value1", + "--boundary", + ( + 'Content-Disposition: form-data; name="name2"; ' + 'filename="name2.txt"' + ), + "", + "value2", + "--boundary--", + ] + ) + ) + self.request = WSGIRequest( + { + "REQUEST_METHOD": "POST", + "CONTENT_TYPE": "multipart/form-data; boundary=boundary", + "CONTENT_LENGTH": len(payload), + "wsgi.input": payload, + } + ) + + def test_number_exceeded(self): + with self.settings(DATA_UPLOAD_MAX_NUMBER_FILES=1): + with self.assertRaisesMessage(TooManyFilesSent, TOO_MANY_FILES_MSG): + self.request._load_post_and_files() + + def test_number_not_exceeded(self): + with self.settings(DATA_UPLOAD_MAX_NUMBER_FILES=2): + self.request._load_post_and_files() + + def test_no_limit(self): + with self.settings(DATA_UPLOAD_MAX_NUMBER_FILES=None): + self.request._load_post_and_files() + + class DataUploadMaxNumberOfFieldsFormPost(SimpleTestCase): def setUp(self): payload = FakePayload("\r\n".join(['a=1&a=2;a=3', '']))
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