[3.2.x] Fixed CVE-2023-24580 -- Prevented DoS with too many uploaded files.

Thanks to Jakob Ackermann for the report.

1 files changed, 51 insertions, 11 deletions

diff --git a/django/http/multipartparser.py b/django/http/multipartparser.py
index 35a54f4ca1..d8a304d4ba 100644
--- a/django/http/multipartparser.py
+++ b/django/http/multipartparser.py
@@ -14,6 +14,7 @@ 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,
@@ -38,6 +39,7 @@ class InputStreamExhausted(Exception):
 RAW = "raw"
 FILE = "file"
 FIELD = "field"
+FIELD_TYPES = frozenset([FIELD, RAW])
 
 
 class MultiPartParser:
@@ -102,6 +104,22 @@ 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.
@@ -147,6 +165,8 @@ 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
         # Whether a file upload is finished.
@@ -162,6 +182,20 @@ class MultiPartParser:
                     old_field_name = None
                     uploaded_file = True
 
+                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()
@@ -174,15 +208,6 @@ class MultiPartParser:
                 field_name = force_str(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
@@ -208,6 +233,16 @@ class MultiPartParser:
 
                     self._post.appendlist(field_name, force_str(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:
@@ -276,8 +311,13 @@ 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: