From 7c240c2f1030daf455f04b163fa9807d6bb2a21a Mon Sep 17 00:00:00 2001
From: starlet-dx <15929766099@163.com>
Date: Tue, 16 May 2023 11:23:26 +0800
Subject: [PATCH 1/1] [4.1.x] Fixed CVE-2023-31047, Fixed #31710 -- Prevented
 potential bypass of validation when uploading multiple files using one form
 field.

Thanks Moataz Al-Sharida and nawaik for reports.

Co-authored-by: Shai Berger <shai@platonix.com>
Co-authored-by: nessita <124304+nessita@users.noreply.github.com>

Origin:
https://github.com/django/django/commit/e7c3a2ccc3a562328600be05068ed9149e12ce64
---
 django/forms/widgets.py                       | 26 ++++++-
 docs/topics/http/file-uploads.txt             | 64 +++++++++++++++--
 .../forms_tests/field_tests/test_filefield.py | 68 ++++++++++++++++++-
 .../widget_tests/test_clearablefileinput.py   |  5 ++
 .../widget_tests/test_fileinput.py            | 44 ++++++++++++
 5 files changed, 199 insertions(+), 8 deletions(-)

diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 972267b..ce0d4f7 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -413,17 +413,41 @@ class MultipleHiddenInput(HiddenInput):
 
 
 class FileInput(Input):
+    allow_multiple_selected = False
     input_type = "file"
     needs_multipart_form = True
     template_name = "django/forms/widgets/file.html"
 
+    def __init__(self, attrs=None):
+        if (
+            attrs is not None
+            and not self.allow_multiple_selected
+            and attrs.get("multiple", False)
+        ):
+            raise ValueError(
+                "%s doesn't support uploading multiple files."
+                % self.__class__.__qualname__
+            )
+        if self.allow_multiple_selected:
+            if attrs is None:
+                attrs = {"multiple": True}
+            else:
+                attrs.setdefault("multiple", True)
+        super().__init__(attrs)
+
     def format_value(self, value):
         """File input never renders a value."""
         return
 
     def value_from_datadict(self, data, files, name):
         "File widgets take data from FILES, not POST"
-        return files.get(name)
+        getter = files.get
+        if self.allow_multiple_selected:
+            try:
+                getter = files.getlist
+            except AttributeError:
+                pass
+        return getter(name)
 
     def value_omitted_from_data(self, data, files, name):
         return name not in files
diff --git a/docs/topics/http/file-uploads.txt b/docs/topics/http/file-uploads.txt
index 94b7432..52a7f09 100644
--- a/docs/topics/http/file-uploads.txt
+++ b/docs/topics/http/file-uploads.txt
@@ -139,19 +139,53 @@ a :class:`~django.core.files.File` like object to the
             instance = ModelWithFileField(file_field=content_file)
             instance.save()
 
+.. _uploading_multiple_files:
+
 Uploading multiple files
 ------------------------
 
-If you want to upload multiple files using one form field, set the ``multiple``
-HTML attribute of field's widget:
+..
+    Tests in tests.forms_tests.field_tests.test_filefield.MultipleFileFieldTest
+    should be updated after any changes in the following snippets.
+
+If you want to upload multiple files using one form field, create a subclass
+of the field's widget and set the ``allow_multiple_selected`` attribute on it
+to ``True``.
+
+In order for such files to be all validated by your form (and have the value of
+the field include them all), you will also have to subclass ``FileField``. See
+below for an example.
+
+.. admonition:: Multiple file field
+
+    Django is likely to have a proper multiple file field support at some point
+    in the future.
 
 .. code-block:: python
     :caption: ``forms.py``
 
     from django import forms
 
+    class MultipleFileInput(forms.ClearableFileInput):
+        allow_multiple_selected = True
+
+
+    class MultipleFileField(forms.FileField):
+        def __init__(self, *args, **kwargs):
+            kwargs.setdefault("widget", MultipleFileInput())
+            super().__init__(*args, **kwargs)
+
+        def clean(self, data, initial=None):
+            single_file_clean = super().clean
+            if isinstance(data, (list, tuple)):
+                result = [single_file_clean(d, initial) for d in data]
+            else:
+                result = single_file_clean(data, initial)
+            return result
+
+
     class FileFieldForm(forms.Form):
-        file_field = forms.FileField(widget=forms.ClearableFileInput(attrs={'multiple': True}))
+        file_field = MultipleFileField()
 
 Then override the ``post`` method of your
 :class:`~django.views.generic.edit.FormView` subclass to handle multiple file
@@ -171,14 +205,32 @@ uploads:
         def post(self, request, *args, **kwargs):
             form_class = self.get_form_class()
             form = self.get_form(form_class)
-            files = request.FILES.getlist('file_field')
             if form.is_valid():
-                for f in files:
-                    ...  # Do something with each file.
                 return self.form_valid(form)
             else:
                 return self.form_invalid(form)
 
+        def form_valid(self, form):
+            files = form.cleaned_data["file_field"]
+            for f in files:
+                ...  # Do something with each file.
+            return super().form_valid()
+
+.. warning::
+
+   This will allow you to handle multiple files at the form level only. Be
+   aware that you cannot use it to put multiple files on a single model
+   instance (in a single field), for example, even if the custom widget is used
+   with a form field related to a model ``FileField``.
+
+.. versionchanged:: 3.2.19
+
+   In previous versions, there was no support for the ``allow_multiple_selected``
+   class attribute, and users were advised to create the widget with the HTML
+   attribute ``multiple`` set through the ``attrs`` argument. However, this
+   caused validation of the form field to be applied only to the last file
+   submitted, which could have adverse security implications.
+
 Upload Handlers
 ===============
 
diff --git a/tests/forms_tests/field_tests/test_filefield.py b/tests/forms_tests/field_tests/test_filefield.py
index 56aaa31..00c74a7 100644
--- a/tests/forms_tests/field_tests/test_filefield.py
+++ b/tests/forms_tests/field_tests/test_filefield.py
@@ -2,7 +2,8 @@ import pickle
 
 from django.core.exceptions import ValidationError
 from django.core.files.uploadedfile import SimpleUploadedFile
-from django.forms import FileField
+from django.core.validators import validate_image_file_extension
+from django.forms import FileField, FileInput
 from django.test import SimpleTestCase
 
 
@@ -109,3 +110,68 @@ class FileFieldTest(SimpleTestCase):
 
     def test_file_picklable(self):
         self.assertIsInstance(pickle.loads(pickle.dumps(FileField())), FileField)
+
+
+class MultipleFileInput(FileInput):
+    allow_multiple_selected = True
+
+
+class MultipleFileField(FileField):
+    def __init__(self, *args, **kwargs):
+        kwargs.setdefault("widget", MultipleFileInput())
+        super().__init__(*args, **kwargs)
+
+    def clean(self, data, initial=None):
+        single_file_clean = super().clean
+        if isinstance(data, (list, tuple)):
+            result = [single_file_clean(d, initial) for d in data]
+        else:
+            result = single_file_clean(data, initial)
+        return result
+
+
+class MultipleFileFieldTest(SimpleTestCase):
+    def test_file_multiple(self):
+        f = MultipleFileField()
+        files = [
+            SimpleUploadedFile("name1", b"Content 1"),
+            SimpleUploadedFile("name2", b"Content 2"),
+        ]
+        self.assertEqual(f.clean(files), files)
+
+    def test_file_multiple_empty(self):
+        f = MultipleFileField()
+        files = [
+            SimpleUploadedFile("empty", b""),
+            SimpleUploadedFile("nonempty", b"Some Content"),
+        ]
+        msg = "'The submitted file is empty.'"
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(files)
+        with self.assertRaisesMessage(ValidationError, msg):
+            f.clean(files[::-1])
+
+    def test_file_multiple_validation(self):
+        f = MultipleFileField(validators=[validate_image_file_extension])
+
+        good_files = [
+            SimpleUploadedFile("image1.jpg", b"fake JPEG"),
+            SimpleUploadedFile("image2.png", b"faux image"),
+            SimpleUploadedFile("image3.bmp", b"fraudulent bitmap"),
+        ]
+        self.assertEqual(f.clean(good_files), good_files)
+
+        evil_files = [
+            SimpleUploadedFile("image1.sh", b"#!/bin/bash -c 'echo pwned!'\n"),
+            SimpleUploadedFile("image2.png", b"faux image"),
+            SimpleUploadedFile("image3.jpg", b"fake JPEG"),
+        ]
+
+        evil_rotations = (
+            evil_files[i:] + evil_files[:i]  # Rotate by i.
+            for i in range(len(evil_files))
+        )
+        msg = "File extension “sh” is not allowed. Allowed extensions are: "
+        for rotated_evil_files in evil_rotations:
+            with self.assertRaisesMessage(ValidationError, msg):
+                f.clean(rotated_evil_files)
diff --git a/tests/forms_tests/widget_tests/test_clearablefileinput.py b/tests/forms_tests/widget_tests/test_clearablefileinput.py
index fb6a2f6..0b34335 100644
--- a/tests/forms_tests/widget_tests/test_clearablefileinput.py
+++ b/tests/forms_tests/widget_tests/test_clearablefileinput.py
@@ -232,3 +232,8 @@ class ClearableFileInputTest(WidgetTest):
             '<input type="file" name="clearable_file" id="id_clearable_file"></div>',
             form.render(),
         )
+
+    def test_multiple_error(self):
+        msg = "ClearableFileInput doesn't support uploading multiple files."
+        with self.assertRaisesMessage(ValueError, msg):
+            ClearableFileInput(attrs={"multiple": True})
diff --git a/tests/forms_tests/widget_tests/test_fileinput.py b/tests/forms_tests/widget_tests/test_fileinput.py
index ea73e57..a49f481 100644
--- a/tests/forms_tests/widget_tests/test_fileinput.py
+++ b/tests/forms_tests/widget_tests/test_fileinput.py
@@ -1,4 +1,6 @@
+from django.core.files.uploadedfile import SimpleUploadedFile
 from django.forms import FileField, FileInput, Form
+from django.utils.datastructures import MultiValueDict
 
 from .base import WidgetTest
 
@@ -48,3 +50,45 @@ class FileInputTest(WidgetTest):
             'name="field" required type="file"></div>',
             form.render(),
         )
+
+    def test_multiple_error(self):
+        msg = "FileInput doesn't support uploading multiple files."
+        with self.assertRaisesMessage(ValueError, msg):
+            FileInput(attrs={"multiple": True})
+
+    def test_value_from_datadict_multiple(self):
+        class MultipleFileInput(FileInput):
+            allow_multiple_selected = True
+
+        file_1 = SimpleUploadedFile("something1.txt", b"content 1")
+        file_2 = SimpleUploadedFile("something2.txt", b"content 2")
+        # Uploading multiple files is allowed.
+        widget = MultipleFileInput(attrs={"multiple": True})
+        value = widget.value_from_datadict(
+            data={"name": "Test name"},
+            files=MultiValueDict({"myfile": [file_1, file_2]}),
+            name="myfile",
+        )
+        self.assertEqual(value, [file_1, file_2])
+        # Uploading multiple files is not allowed.
+        widget = FileInput()
+        value = widget.value_from_datadict(
+            data={"name": "Test name"},
+            files=MultiValueDict({"myfile": [file_1, file_2]}),
+            name="myfile",
+        )
+        self.assertEqual(value, file_2)
+
+    def test_multiple_default(self):
+        class MultipleFileInput(FileInput):
+            allow_multiple_selected = True
+
+        tests = [
+            (None, True),
+            ({"class": "myclass"}, True),
+            ({"multiple": False}, False),
+        ]
+        for attrs, expected in tests:
+            with self.subTest(attrs=attrs):
+                widget = MultipleFileInput(attrs=attrs)
+                self.assertIs(widget.attrs["multiple"], expected)
-- 
2.30.0