django/tests/file_uploads/tests.py

import base64
import hashlib
import os
import shutil
import sys
import tempfile as sys_tempfile
import unittest
from io import BytesIO, StringIO
from unittest import mock
from urllib.parse import quote

from django.conf import DEFAULT_STORAGE_ALIAS
from django.core.exceptions import SuspiciousFileOperation
from django.core.files import temp as tempfile
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,
)
from django.test import SimpleTestCase, TestCase, client, override_settings

from . import uploadhandler
from .models import FileModel

UNICODE_FILENAME = "test-0123456789_中文_Orléans.jpg"
MEDIA_ROOT = sys_tempfile.mkdtemp()
UPLOAD_FOLDER = "test_upload"
UPLOAD_TO = os.path.join(MEDIA_ROOT, UPLOAD_FOLDER)

CANDIDATE_TRAVERSAL_FILE_NAMES = [
    "/tmp/hax0rd.txt",  # Absolute path, *nix-style.
    "C:\\Windows\\hax0rd.txt",  # Absolute path, win-style.
    "C:/Windows/hax0rd.txt",  # Absolute path, broken-style.
    "\\tmp\\hax0rd.txt",  # Absolute path, broken in a different way.
    "/tmp\\hax0rd.txt",  # Absolute path, broken by mixing.
    "subdir/hax0rd.txt",  # Descendant path, *nix-style.
    "subdir\\hax0rd.txt",  # Descendant path, win-style.
    "sub/dir\\hax0rd.txt",  # Descendant path, mixed.
    "../../hax0rd.txt",  # Relative path, *nix-style.
    "..\\..\\hax0rd.txt",  # Relative path, win-style.
    "../..\\hax0rd.txt",  # Relative path, mixed.
    "../hax0rd.txt",  # HTML entities.
    "../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=[]
)
class FileUploadTests(TestCase):
    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        os.makedirs(MEDIA_ROOT, exist_ok=True)
        cls.addClassCleanup(shutil.rmtree, MEDIA_ROOT)

    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 = {
                "name": "Ringo",
                "file_field": fp,
            }
            response = self.client.post("/upload/", post_data)
        self.assertEqual(response.status_code, 200)

    def test_large_upload(self):
        file = tempfile.NamedTemporaryFile
        with file(suffix=".file1") as file1, file(suffix=".file2") as file2:
            file1.write(b"a" * (2**21))
            file1.seek(0)

            file2.write(b"a" * (10 * 2**20))
            file2.seek(0)

            post_data = {
                "name": "Ringo",
                "file_field1": file1,
                "file_field2": file2,
            }

            for key in list(post_data):
                try:
                    post_data[key + "_hash"] = hashlib.sha1(
                        post_data[key].read()
                    ).hexdigest()
                    post_data[key].seek(0)
                except AttributeError:
                    post_data[key + "_hash"] = hashlib.sha1(
                        post_data[key].encode()
                    ).hexdigest()

            response = self.client.post("/verify/", post_data)

            self.assertEqual(response.status_code, 200)

    def _test_base64_upload(self, content, encode=base64.b64encode):
        payload = client.FakePayload(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    'Content-Disposition: form-data; name="file"; filename="test.txt"',
                    "Content-Type: application/octet-stream",
                    "Content-Transfer-Encoding: base64",
                    "",
                ]
            )
        )
        payload.write(b"\r\n" + encode(content.encode()) + b"\r\n")
        payload.write("--" + 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.json()["file"], content)

    def test_base64_upload(self):
        self._test_base64_upload("This data will be transmitted base64-encoded.")

    def test_big_base64_upload(self):
        self._test_base64_upload("Big data" * 68000)  # > 512Kb

    def test_big_base64_newlines_upload(self):
        self._test_base64_upload("Big data" * 68000, encode=base64.encodebytes)

    def test_base64_invalid_upload(self):
        payload = client.FakePayload(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    'Content-Disposition: form-data; name="file"; filename="test.txt"',
                    "Content-Type: application/octet-stream",
                    "Content-Transfer-Encoding: base64",
                    "",
                ]
            )
        )
        payload.write(b"\r\n!\r\n")
        payload.write("--" + 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.json()["file"], "")

    def test_unicode_file_name(self):
        with sys_tempfile.TemporaryDirectory() as temp_dir:
            # This file contains Chinese symbols and an accented char in the name.
            with open(os.path.join(temp_dir, UNICODE_FILENAME), "w+b") as file1:
                file1.write(b"b" * (2**10))
                file1.seek(0)
                response = self.client.post("/unicode_name/", {"file_unicode": file1})
            self.assertEqual(response.status_code, 200)

    def test_unicode_file_name_rfc2231(self):
        """
        Receiving file upload when filename is encoded with RFC 2231.
        """
        payload = client.FakePayload()
        payload.write(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    'Content-Disposition: form-data; name="file_unicode"; '
                    "filename*=UTF-8''%s" % quote(UNICODE_FILENAME),
                    "Content-Type: application/octet-stream",
                    "",
                    "You got pwnd.\r\n",
                    "\r\n--" + client.BOUNDARY + "--\r\n",
                ]
            )
        )

        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/unicode_name/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        self.assertEqual(response.status_code, 200)

    def test_unicode_name_rfc2231(self):
        """
        Receiving file upload when filename is encoded with RFC 2231.
        """
        payload = client.FakePayload()
        payload.write(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    "Content-Disposition: form-data; name*=UTF-8''file_unicode; "
                    "filename*=UTF-8''%s" % quote(UNICODE_FILENAME),
                    "Content-Type: application/octet-stream",
                    "",
                    "You got pwnd.\r\n",
                    "\r\n--" + client.BOUNDARY + "--\r\n",
                ]
            )
        )

        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/unicode_name/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        self.assertEqual(response.status_code, 200)

    def test_unicode_file_name_rfc2231_with_double_quotes(self):
        payload = client.FakePayload()
        payload.write(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    'Content-Disposition: form-data; name="file_unicode"; '
                    "filename*=\"UTF-8''%s\"" % quote(UNICODE_FILENAME),
                    "Content-Type: application/octet-stream",
                    "",
                    "You got pwnd.\r\n",
                    "\r\n--" + client.BOUNDARY + "--\r\n",
                ]
            )
        )
        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/unicode_name/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        self.assertEqual(response.status_code, 200)

    def test_unicode_name_rfc2231_with_double_quotes(self):
        payload = client.FakePayload()
        payload.write(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    "Content-Disposition: form-data; name*=\"UTF-8''file_unicode\"; "
                    "filename*=\"UTF-8''%s\"" % quote(UNICODE_FILENAME),
                    "Content-Type: application/octet-stream",
                    "",
                    "You got pwnd.\r\n",
                    "\r\n--" + client.BOUNDARY + "--\r\n",
                ]
            )
        )
        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/unicode_name/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        self.assertEqual(response.status_code, 200)

    def test_blank_filenames(self):
        """
        Receiving file upload when filename is blank (before and after
        sanitization) should be okay.
        """
        filenames = [
            "",
            # Normalized by MultiPartParser.IE_sanitize().
            "C:\\Windows\\",
            # Normalized by os.path.basename().
            "/",
            "ends-with-slash/",
        ]
        payload = client.FakePayload()
        for i, name in enumerate(filenames):
            payload.write(
                "\r\n".join(
                    [
                        "--" + client.BOUNDARY,
                        'Content-Disposition: form-data; name="file%s"; filename="%s"'
                        % (i, name),
                        "Content-Type: application/octet-stream",
                        "",
                        "You got pwnd.\r\n",
                    ]
                )
            )
        payload.write("\r\n--" + client.BOUNDARY + "--\r\n")

        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/echo/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        self.assertEqual(response.status_code, 200)

        # Empty filenames should be ignored
        received = response.json()
        for i, name in enumerate(filenames):
            self.assertIsNone(received.get("file%s" % i))

    def test_non_printable_chars_in_file_names(self):
        file_name = "non-\x00printable\x00\n_chars.txt\x00"
        payload = client.FakePayload()
        payload.write(
            "\r\n".join(
                [
                    "--" + client.BOUNDARY,
                    f'Content-Disposition: form-data; name="file"; '
                    f'filename="{file_name}"',
                    "Content-Type: application/octet-stream",
                    "",
                    "You got pwnd.\r\n",
                ]
            )
        )
        payload.write("\r\n--" + client.BOUNDARY + "--\r\n")
        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/echo/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        # Non-printable chars are sanitized.
        received = response.json()
        self.assertEqual(received["file"], "non-printable_chars.txt")

    def test_dangerous_file_names(self):
        """Uploaded file names should be sanitized before ever reaching the view."""
        # This test simulates possible directory traversal attacks by a
        # malicious uploader We have to do some monkeybusiness here to construct
        # a malicious payload with an invalid file name (containing os.sep or
        # os.pardir). This similar to what an attacker would need to do when
        # trying such an attack.
        payload = client.FakePayload()
        for i, name in enumerate(CANDIDATE_TRAVERSAL_FILE_NAMES):
            payload.write(
                "\r\n".join(
                    [
                        "--" + client.BOUNDARY,
                        'Content-Disposition: form-data; name="file%s"; filename="%s"'
                        % (i, name),
                        "Content-Type: application/octet-stream",
                        "",
                        "You got pwnd.\r\n",
                    ]
                )
            )
        payload.write("\r\n--" + client.BOUNDARY + "--\r\n")

        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/echo/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        # The filenames should have been sanitized by the time it got to the view.
        received = response.json()
        for i, name in enumerate(CANDIDATE_TRAVERSAL_FILE_NAMES):
            got = received["file%s" % i]
            self.assertEqual(got, "hax0rd.txt")

    def test_filename_overflow(self):
        """File names over 256 characters (dangerous on some platforms) get fixed up."""
        long_str = "f" * 300
        cases = [
            # field name, filename, expected
            ("long_filename", "%s.txt" % long_str, "%s.txt" % long_str[:251]),
            ("long_extension", "foo.%s" % long_str, ".%s" % long_str[:254]),
            ("no_extension", long_str, long_str[:255]),
            ("no_filename", ".%s" % long_str, ".%s" % long_str[:254]),
            ("long_everything", "%s.%s" % (long_str, long_str), ".%s" % long_str[:254]),
        ]
        payload = client.FakePayload()
        for name, filename, _ in cases:
            payload.write(
                "\r\n".join(
                    [
                        "--" + client.BOUNDARY,
                        'Content-Disposition: form-data; name="{}"; filename="{}"',
                        "Content-Type: application/octet-stream",
                        "",
                        "Oops.",
                        "",
                    ]
                ).format(name, filename)
            )
        payload.write("\r\n--" + client.BOUNDARY + "--\r\n")
        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/echo/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        response = self.client.request(**r)
        result = response.json()
        for name, _, expected in cases:
            got = result[name]
            self.assertEqual(expected, got, "Mismatch for {}".format(name))
            self.assertLess(
                len(got), 256, "Got a long file name (%s characters)." % len(got)
            )

    def test_file_content(self):
        file = tempfile.NamedTemporaryFile
        with (
            file(suffix=".ctype_extra") as no_content_type,
            file(suffix=".ctype_extra") as simple_file,
        ):
            no_content_type.write(b"no content")
            no_content_type.seek(0)

            simple_file.write(b"text content")
            simple_file.seek(0)
            simple_file.content_type = "text/plain"

            string_io = StringIO("string content")
            bytes_io = BytesIO(b"binary content")

            response = self.client.post(
                "/echo_content/",
                {
                    "no_content_type": no_content_type,
                    "simple_file": simple_file,
                    "string": string_io,
                    "binary": bytes_io,
                },
            )
            received = response.json()
            self.assertEqual(received["no_content_type"], "no content")
            self.assertEqual(received["simple_file"], "text content")
            self.assertEqual(received["string"], "string content")
            self.assertEqual(received["binary"], "binary content")

    def test_content_type_extra(self):
        """Uploaded files may have content type parameters available."""
        file = tempfile.NamedTemporaryFile
        with (
            file(suffix=".ctype_extra") as no_content_type,
            file(suffix=".ctype_extra") as simple_file,
        ):
            no_content_type.write(b"something")
            no_content_type.seek(0)

            simple_file.write(b"something")
            simple_file.seek(0)
            simple_file.content_type = "text/plain; test-key=test_value"

            response = self.client.post(
                "/echo_content_type_extra/",
                {
                    "no_content_type": no_content_type,
                    "simple_file": simple_file,
                },
            )
            received = response.json()
            self.assertEqual(received["no_content_type"], {})
            self.assertEqual(received["simple_file"], {"test-key": "test_value"})

    def test_truncated_multipart_handled_gracefully(self):
        """
        If passed an incomplete multipart message, MultiPartParser does not
        attempt to read beyond the end of the stream, and simply will handle
        the part that can be parsed gracefully.
        """
        payload_str = "\r\n".join(
            [
                "--" + client.BOUNDARY,
                'Content-Disposition: form-data; name="file"; filename="foo.txt"',
                "Content-Type: application/octet-stream",
                "",
                "file contents" "--" + client.BOUNDARY + "--",
                "",
            ]
        )
        payload = client.FakePayload(payload_str[:-10])
        r = {
            "CONTENT_LENGTH": len(payload),
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/echo/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": payload,
        }
        self.assertEqual(self.client.request(**r).json(), {})

    def test_empty_multipart_handled_gracefully(self):
        """
        If passed an empty multipart message, MultiPartParser will return
        an empty QueryDict.
        """
        r = {
            "CONTENT_LENGTH": 0,
            "CONTENT_TYPE": client.MULTIPART_CONTENT,
            "PATH_INFO": "/echo/",
            "REQUEST_METHOD": "POST",
            "wsgi.input": client.FakePayload(b""),
        }
        self.assertEqual(self.client.request(**r).json(), {})

    def test_custom_upload_handler(self):
        file = tempfile.NamedTemporaryFile
        with file() as smallfile, file() as bigfile:
            # A small file (under the 5M quota)
            smallfile.write(b"a" * (2**21))
            smallfile.seek(0)

            # A big file (over the quota)
            bigfile.write(b"a" * (10 * 2**20))
            bigfile.seek(0)

            # Small file posting should work.
            self.assertIn("f", self.client.post("/quota/", {"f": smallfile}).json())

            # Large files don't go through.
            self.assertNotIn("f", self.client.post("/quota/", {"f": bigfile}).json())

    def test_broken_custom_upload_handler(self):
        with tempfile.NamedTemporaryFile() as file:
            file.write(b"a" * (2**21))
            file.seek(0)

            msg = (
                "You cannot alter upload handlers after the upload has been processed."
            )
            with self.assertRaisesMessage(AttributeError, msg):
                self.client.post("/quota/broken/", {"f": file})

    def test_stop_upload_temporary_file_handler(self):
        with tempfile.NamedTemporaryFile() as temp_file:
            temp_file.write(b"a")
            temp_file.seek(0)
            response = self.client.post("/temp_file/stop_upload/", {"file": temp_file})
            temp_path = response.json()["temp_path"]
            self.assertIs(os.path.exists(temp_path), False)

    def test_upload_interrupted_temporary_file_handler(self):
        # Simulate an interrupted upload by omitting the closing boundary.
        class MockedParser(Parser):
            def __iter__(self):
                for item in super().__iter__():
                    item_type, meta_data, field_stream = item
                    yield item_type, meta_data, field_stream
                    if item_type == FILE:
                        return

        with tempfile.NamedTemporaryFile() as temp_file:
            temp_file.write(b"a")
            temp_file.seek(0)
            with mock.patch(
                "django.http.multipartparser.Parser",
                MockedParser,
            ):
                response = self.client.post(
                    "/temp_file/upload_interrupted/",
                    {"file": temp_file},
                )
            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:
            file1.write(b"a" * (2**23))
            file1.seek(0)

            file2.write(b"a" * (2 * 2**18))
            file2.seek(0)

            file2a.write(b"a" * (5 * 2**20))
            file2a.seek(0)

            response = self.client.post(
                "/getlist_count/",
                {
                    "file1": file1,
                    "field1": "test",
                    "field2": "test3",
                    "field3": "test5",
                    "field4": "test6",
                    "field5": "test7",
                    "file2": (file2, file2a),
                },
            )
            got = response.json()
            self.assertEqual(got.get("file1"), 1)
            self.assertEqual(got.get("file2"), 2)

    def test_fileuploads_closed_at_request_end(self):
        file = tempfile.NamedTemporaryFile
        with file() as f1, file() as f2a, file() as f2b:
            response = self.client.post(
                "/fd_closing/t/",
                {
                    "file": f1,
                    "file2": (f2a, f2b),
                },
            )

        request = response.wsgi_request
        # The files were parsed.
        self.assertTrue(hasattr(request, "_files"))

        file = request._files["file"]
        self.assertTrue(file.closed)

        files = request._files.getlist("file2")
        self.assertTrue(files[0].closed)
        self.assertTrue(files[1].closed)

    def test_no_parsing_triggered_by_fd_closing(self):
        file = tempfile.NamedTemporaryFile
        with file() as f1, file() as f2a, file() as f2b:
            response = self.client.post(
                "/fd_closing/f/",
                {
                    "file": f1,
                    "file2": (f2a, f2b),
                },
            )

        request = response.wsgi_request
        # The fd closing logic doesn't trigger parsing of the stream
        self.assertFalse(hasattr(request, "_files"))

    def test_file_error_blocking(self):
        """
        The server should not block when there are upload errors (bug #8622).
        This can happen if something -- i.e. an exception handler -- tries to
        access POST while handling an error in parsing POST. This shouldn't
        cause an infinite loop!
        """

        class POSTAccessingHandler(client.ClientHandler):
            """A handler that'll access POST during an exception."""

            def handle_uncaught_exception(self, request, resolver, exc_info):
                ret = super().handle_uncaught_exception(request, resolver, exc_info)
                request.POST  # evaluate
                return ret

        # Maybe this is a little more complicated that it needs to be; but if
        # the django.test.client.FakePayload.read() implementation changes then
        # this test would fail.  So we need to know exactly what kind of error
        # it raises when there is an attempt to read more than the available bytes:
        try:
            client.FakePayload(b"a").read(2)
        except Exception as err:
            reference_error = err

        # install the custom handler that tries to access request.POST
        self.client.handler = POSTAccessingHandler()

        with open(__file__, "rb") as fp:
            post_data = {
                "name": "Ringo",
                "file_field": fp,
            }
            try:
                self.client.post("/upload_errors/", post_data)
            except reference_error.__class__ as err:
                self.assertNotEqual(
                    str(err),
                    str(reference_error),
                    "Caught a repeated exception that'll cause an infinite loop in "
                    "file uploads.",
                )
            except Exception as err:
                # CustomUploadError is the error that should have been raised
                self.assertEqual(err.__class__, uploadhandler.CustomUploadError)

    def test_filename_case_preservation(self):
        """
        The storage backend shouldn't mess with the case of the filenames
        uploaded.
        """
        # Synthesize the contents of a file upload with a mixed case filename
        # so we don't have to carry such a file in the Django tests source code
        # tree.
        vars = {"boundary": "oUrBoUnDaRyStRiNg"}
        post_data = [
            "--%(boundary)s",
            'Content-Disposition: form-data; name="file_field"; '
            'filename="MiXeD_cAsE.txt"',
            "Content-Type: application/octet-stream",
            "",
            "file contents\n",
            "--%(boundary)s--\r\n",
        ]
        response = self.client.post(
            "/filename_case/",
            "\r\n".join(post_data) % vars,
            "multipart/form-data; boundary=%(boundary)s" % vars,
        )
        self.assertEqual(response.status_code, 200)
        id = int(response.content)
        obj = FileModel.objects.get(pk=id)
        # The name of the file uploaded and the file stored in the server-side
        # shouldn't differ.
        self.assertEqual(os.path.basename(obj.testfile.path), "MiXeD_cAsE.txt")

    def test_filename_traversal_upload(self):
        os.makedirs(UPLOAD_TO, exist_ok=True)
        tests = [
            "../test.txt",
            "../test.txt",
        ]
        for file_name in tests:
            with self.subTest(file_name=file_name):
                payload = client.FakePayload()
                payload.write(
                    "\r\n".join(
                        [
                            "--" + client.BOUNDARY,
                            'Content-Disposition: form-data; name="my_file"; '
                            'filename="%s";' % file_name,
                            "Content-Type: text/plain",
                            "",
                            "file contents.\r\n",
                            "\r\n--" + client.BOUNDARY + "--\r\n",
                        ]
                    ),
                )
                r = {
                    "CONTENT_LENGTH": len(payload),
                    "CONTENT_TYPE": client.MULTIPART_CONTENT,
                    "PATH_INFO": "/upload_traversal/",
                    "REQUEST_METHOD": "POST",
                    "wsgi.input": payload,
                }
                response = self.client.request(**r)
                result = response.json()
                self.assertEqual(response.status_code, 200)
                self.assertEqual(result["file_name"], "test.txt")
                self.assertIs(
                    os.path.exists(os.path.join(MEDIA_ROOT, "test.txt")),
                    False,
                )
                self.assertIs(
                    os.path.exists(os.path.join(UPLOAD_TO, "test.txt")),
                    True,
                )


@override_settings(MEDIA_ROOT=MEDIA_ROOT)
class DirectoryCreationTests(SimpleTestCase):
    """
    Tests for error handling during directory creation
    via _save_FIELD_file (ticket #6450)
    """

    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        os.makedirs(MEDIA_ROOT, exist_ok=True)
        cls.addClassCleanup(shutil.rmtree, MEDIA_ROOT)

    def setUp(self):
        self.obj = FileModel()

    @unittest.skipIf(
        sys.platform == "win32", "Python on Windows doesn't have working os.chmod()."
    )
    @override_settings(
        STORAGES={
            DEFAULT_STORAGE_ALIAS: {
                "BACKEND": "django.core.files.storage.FileSystemStorage",
            }
        }
    )
    def test_readonly_root(self):
        """Permission errors are not swallowed"""
        os.chmod(MEDIA_ROOT, 0o500)
        self.addCleanup(os.chmod, MEDIA_ROOT, 0o700)
        with self.assertRaises(PermissionError):
            self.obj.testfile.save(
                "foo.txt", SimpleUploadedFile("foo.txt", b"x"), save=False
            )

    def test_not_a_directory(self):
        default_storage.delete(UPLOAD_TO)
        # Create a file with the upload directory name
        with SimpleUploadedFile(UPLOAD_TO, b"x") as file:
            default_storage.save(UPLOAD_TO, file)
        self.addCleanup(default_storage.delete, UPLOAD_TO)
        msg = "%s exists and is not a directory." % UPLOAD_TO
        with self.assertRaisesMessage(FileExistsError, msg):
            with SimpleUploadedFile("foo.txt", b"x") as file:
                self.obj.testfile.save("foo.txt", file, save=False)


class MultiParserTests(SimpleTestCase):
    def test_empty_upload_handlers(self):
        # We're not actually parsing here; just checking if the parser properly
        # instantiates with empty upload handlers.
        MultiPartParser(
            {
                "CONTENT_TYPE": "multipart/form-data; boundary=_foo",
                "CONTENT_LENGTH": "1",
            },
            StringIO("x"),
            [],
            "utf-8",
        )

    def test_invalid_content_type(self):
        with self.assertRaisesMessage(
            MultiPartParserError, "Invalid Content-Type: text/plain"
        ):
            MultiPartParser(
                {
                    "CONTENT_TYPE": "text/plain",
                    "CONTENT_LENGTH": "1",
                },
                StringIO("x"),
                [],
                "utf-8",
            )

    def test_negative_content_length(self):
        with self.assertRaisesMessage(
            MultiPartParserError, "Invalid content length: -1"
        ):
            MultiPartParser(
                {
                    "CONTENT_TYPE": "multipart/form-data; boundary=_foo",
                    "CONTENT_LENGTH": -1,
                },
                StringIO("x"),
                [],
                "utf-8",
            )

    def test_bad_type_content_length(self):
        multipart_parser = MultiPartParser(
            {
                "CONTENT_TYPE": "multipart/form-data; boundary=_foo",
                "CONTENT_LENGTH": "a",
            },
            StringIO("x"),
            [],
            "utf-8",
        )
        self.assertEqual(multipart_parser._content_length, 0)

    def test_sanitize_file_name(self):
        parser = MultiPartParser(
            {
                "CONTENT_TYPE": "multipart/form-data; boundary=_foo",
                "CONTENT_LENGTH": "1",
            },
            StringIO("x"),
            [],
            "utf-8",
        )
        for file_name in CANDIDATE_TRAVERSAL_FILE_NAMES:
            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))