Fixed #34968 -- Made multipart parsing of headers raise an error on too long headers.

This also allow customizing the maximum size of headers via
MAX_TOTAL_HEADER_SIZE.

django/http/multipartparser.py

@@ -41,6 +41,7 @@ RAW = "raw"
 FILE = "file"
 FIELD = "field"
 FIELD_TYPES = frozenset([FIELD, RAW])
+MAX_TOTAL_HEADER_SIZE = 1024
 
 
 class MultiPartParser:
@@ -682,21 +683,30 @@ def parse_boundary_stream(stream, max_header_size):
     """
     Parse one and exactly one stream that encapsulates a boundary.
     """
-    # Stream at beginning of header, look for end of header
-    # and parse it if found. The header must fit within one
-    # chunk.
-    chunk = stream.read(max_header_size)
 
-    # 'find' returns the top of these four bytes, so we'll
-    # need to munch them later to prevent them from polluting
-    # the payload.
+    # Look for the end of headers and if not found extend the search to double
+    # the size up to the MAX_TOTAL_HEADER_SIZE.
+    headers_chunk_size = 1024
+    while True:
+        if headers_chunk_size > max_header_size:
+            raise MultiPartParserError("Request max total header size exceeded.")
+
+        # Stream at beginning of header, look for end of header and parse it if
+        # found. The header must fit within one chunk.
+        chunk = stream.read(headers_chunk_size)
+        # 'find' returns the top of these four bytes, so munch them later to
+        # prevent them from polluting the payload.
         header_end = chunk.find(b"\r\n\r\n")
+        if header_end != -1:
+            break
 
-    if header_end == -1:
-        # we find no header, so we just mark this fact and pass on
-        # the stream verbatim
+        # Find no header, mark this fact and pass on the stream verbatim.
         stream.unget(chunk)
+        # No more data to read.
+        if len(chunk) < headers_chunk_size:
             return (RAW, {}, stream)
+        # Double the chunk size.
+        headers_chunk_size *= 2
 
     header = chunk[:header_end]
 
@@ -740,4 +750,4 @@ class Parser:
         boundarystream = InterBoundaryIter(self._stream, self._separator)
         for sub_stream in boundarystream:
             # Iterate over each part
-            yield parse_boundary_stream(sub_stream, 1024)
+            yield parse_boundary_stream(sub_stream, MAX_TOTAL_HEADER_SIZE)

tests/file_uploads/tests.py

@@ -16,6 +16,7 @@ from django.core.files.storage import default_storage
 from django.core.files.uploadedfile import SimpleUploadedFile, UploadedFile
 from django.http.multipartparser import (
     FILE,
+    MAX_TOTAL_HEADER_SIZE,
     MultiPartParser,
     MultiPartParserError,
     Parser,
@@ -603,6 +604,57 @@ class FileUploadTests(TestCase):
             temp_path = response.json()["temp_path"]
             self.assertIs(os.path.exists(temp_path), False)
 
+    def test_upload_large_header_fields(self):
+        payload = client.FakePayload(
+            "\r\n".join(
+                [
+                    "--" + client.BOUNDARY,
+                    'Content-Disposition: form-data; name="my_file"; '
+                    'filename="test.txt"',
+                    "Content-Type: text/plain",
+                    "X-Long-Header: %s" % ("-" * 500),
+                    "",
+                    "file contents",
+                    "--" + client.BOUNDARY + "--\r\n",
+                ]
+            ),
+        )
+        r = {
+            "CONTENT_LENGTH": len(payload),
+            "CONTENT_TYPE": client.MULTIPART_CONTENT,
+            "PATH_INFO": "/echo_content/",
+            "REQUEST_METHOD": "POST",
+            "wsgi.input": payload,
+        }
+        response = self.client.request(**r)
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.json(), {"my_file": "file contents"})
+
+    def test_upload_header_fields_too_large(self):
+        payload = client.FakePayload(
+            "\r\n".join(
+                [
+                    "--" + client.BOUNDARY,
+                    'Content-Disposition: form-data; name="my_file"; '
+                    'filename="test.txt"',
+                    "Content-Type: text/plain",
+                    "X-Long-Header: %s" % ("-" * (MAX_TOTAL_HEADER_SIZE + 1)),
+                    "",
+                    "file contents",
+                    "--" + client.BOUNDARY + "--\r\n",
+                ]
+            ),
+        )
+        r = {
+            "CONTENT_LENGTH": len(payload),
+            "CONTENT_TYPE": client.MULTIPART_CONTENT,
+            "PATH_INFO": "/echo_content/",
+            "REQUEST_METHOD": "POST",
+            "wsgi.input": payload,
+        }
+        response = self.client.request(**r)
+        self.assertEqual(response.status_code, 400)
+
     def test_fileupload_getlist(self):
         file = tempfile.NamedTemporaryFile
         with file() as file1, file() as file2, file() as file2a:

tests/requests_tests/tests.py

@@ -11,7 +11,7 @@ from django.http import (
     RawPostDataException,
     UnreadablePostError,
 )
-from django.http.multipartparser import MultiPartParserError
+from django.http.multipartparser import MAX_TOTAL_HEADER_SIZE, MultiPartParserError
 from django.http.request import split_domain_port
 from django.test import RequestFactory, SimpleTestCase, override_settings
 from django.test.client import BOUNDARY, MULTIPART_CONTENT, FakePayload
@@ -691,6 +691,31 @@ class RequestsTests(SimpleTestCase):
         with self.assertRaisesMessage(MultiPartParserError, msg):
             request.POST
 
+    def test_multipart_with_header_fields_too_large(self):
+        payload = FakePayload(
+            "\r\n".join(
+                [
+                    "--boundary",
+                    'Content-Disposition: form-data; name="name"',
+                    "X-Long-Header: %s" % ("-" * (MAX_TOTAL_HEADER_SIZE + 1)),
+                    "",
+                    "value",
+                    "--boundary--",
+                ]
+            )
+        )
+        request = WSGIRequest(
+            {
+                "REQUEST_METHOD": "POST",
+                "CONTENT_TYPE": "multipart/form-data; boundary=boundary",
+                "CONTENT_LENGTH": len(payload),
+                "wsgi.input": payload,
+            }
+        )
+        msg = "Request max total header size exceeded."
+        with self.assertRaisesMessage(MultiPartParserError, msg):
+            request.POST
+
     def test_POST_connection_error(self):
         """
         If wsgi.input.read() raises an exception while trying to read() the