django/tests/file_storage/test_generate_filename.py

import os

from django.core.exceptions import SuspiciousFileOperation
from django.core.files.base import ContentFile
from django.core.files.storage import FileSystemStorage, Storage
from django.db.models import FileField
from django.test import SimpleTestCase


class AWSS3Storage(Storage):
    """
    Simulate an AWS S3 storage which uses Unix-like paths and allows any
    characters in file names but where there aren't actual folders but just
    keys.
    """

    prefix = "mys3folder/"

    def _save(self, name, content):
        """
        This method is important to test that Storage.save() doesn't replace
        '\' with '/' (rather FileSystemStorage.save() does).
        """
        return name

    def get_valid_name(self, name):
        return name

    def get_available_name(self, name, max_length=None):
        return name

    def generate_filename(self, filename):
        """
        This is the method that's important to override when using S3 so that
        os.path() isn't called, which would break S3 keys.
        """
        return self.prefix + self.get_valid_name(filename)


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):
        candidates = [
            ("tmp/../path", "tmp/.."),
            ("tmp\\..\\path", "tmp/.."),
            ("/tmp/../path", "/tmp/.."),
            ("\\tmp\\..\\path", "/tmp/.."),
        ]
        s = FileSystemStorage()
        for file_name, path in candidates:
            msg = "Detected path traversal attempt in '%s'" % path
            with self.subTest(file_name=file_name):
                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 = [
            ("..", "some/folder/.."),
            (".", "some/folder/."),
            ("", "some/folder/"),
            ("???", "???"),
            ("$.$.$", "$.$.$"),
        ]
        f = FileField(upload_to="some/folder/")
        for file_name, msg_file_name in candidates:
            msg = f"Could not derive file name from '{msg_file_name}'"
            with self.subTest(file_name=file_name):
                with self.assertRaisesMessage(SuspiciousFileOperation, msg):
                    f.generate_filename(None, file_name)

    def test_filefield_dangerous_filename_dot_segments(self):
        f = FileField(upload_to="some/folder/")
        msg = "Detected path traversal attempt in 'some/folder/../path'"
        with self.assertRaisesMessage(SuspiciousFileOperation, msg):
            f.generate_filename(None, "../path")

    def test_filefield_generate_filename_absolute_path(self):
        f = FileField(upload_to="some/folder/")
        candidates = [
            "/tmp/path",
            "/tmp/../path",
        ]
        for file_name in candidates:
            msg = f"Detected path traversal attempt in '{file_name}'"
            with self.subTest(file_name=file_name):
                with self.assertRaisesMessage(SuspiciousFileOperation, msg):
                    f.generate_filename(None, file_name)

    def test_filefield_generate_filename(self):
        f = FileField(upload_to="some/folder/")
        self.assertEqual(
            f.generate_filename(None, "test with space.txt"),
            os.path.normpath("some/folder/test_with_space.txt"),
        )

    def test_filefield_generate_filename_with_upload_to(self):
        def upload_to(instance, filename):
            return "some/folder/" + filename

        f = FileField(upload_to=upload_to)
        self.assertEqual(
            f.generate_filename(None, "test with space.txt"),
            os.path.normpath("some/folder/test_with_space.txt"),
        )

    def test_filefield_generate_filename_upload_to_overrides_dangerous_filename(self):
        def upload_to(instance, filename):
            return "test.txt"

        f = FileField(upload_to=upload_to)
        candidates = [
            "/tmp/.",
            "/tmp/..",
            "/tmp/../path",
            "/tmp/path",
            "some/folder/",
            "some/folder/.",
            "some/folder/..",
            "some/folder/???",
            "some/folder/$.$.$",
            "some/../test.txt",
            "",
        ]
        for file_name in candidates:
            with self.subTest(file_name=file_name):
                self.assertEqual(f.generate_filename(None, file_name), "test.txt")

    def test_filefield_generate_filename_upload_to_absolute_path(self):
        def upload_to(instance, filename):
            return "/tmp/" + filename

        f = FileField(upload_to=upload_to)
        candidates = [
            "path",
            "../path",
            "???",
            "$.$.$",
        ]
        for file_name in candidates:
            msg = f"Detected path traversal attempt in '/tmp/{file_name}'"
            with self.subTest(file_name=file_name):
                with self.assertRaisesMessage(SuspiciousFileOperation, msg):
                    f.generate_filename(None, file_name)

    def test_filefield_generate_filename_upload_to_dangerous_filename(self):
        def upload_to(instance, filename):
            return "/tmp/" + filename

        f = FileField(upload_to=upload_to)
        candidates = ["..", ".", ""]
        for file_name in candidates:
            msg = f"Could not derive file name from '/tmp/{file_name}'"
            with self.subTest(file_name=file_name):
                with self.assertRaisesMessage(SuspiciousFileOperation, msg):
                    f.generate_filename(None, file_name)

    def test_filefield_awss3_storage(self):
        """
        Simulate a FileField with an S3 storage which uses keys rather than
        folders and names. FileField and Storage shouldn't have any os.path()
        calls that break the key.
        """
        storage = AWSS3Storage()
        folder = "not/a/folder/"

        f = FileField(upload_to=folder, storage=storage)
        key = "my-file-key\\with odd characters"
        data = ContentFile("test")
        expected_key = AWSS3Storage.prefix + folder + key

        # Simulate call to f.save()
        result_key = f.generate_filename(None, key)
        self.assertEqual(result_key, expected_key)

        result_key = storage.save(result_key, data)
        self.assertEqual(result_key, expected_key)

        # Repeat test with a callable.
        def upload_to(instance, filename):
            # Return a non-normalized path on purpose.
            return folder + filename

        f = FileField(upload_to=upload_to, storage=storage)

        # Simulate call to f.save()
        result_key = f.generate_filename(None, key)
        self.assertEqual(result_key, expected_key)

        result_key = storage.save(result_key, data)
        self.assertEqual(result_key, expected_key)