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Fixed #20347 -- Allowed customizing the maximum number of instantiated forms in formsets. 

Co-authored-by: ethurgood <ethurgood@gmail.com>
This commit is contained in:
David Smith 2020-04-30 08:34:53 +01:00 committed by Mariusz Felisiak
parent b5aa9cb20f
commit 433dd737f9
8 changed files with 202 additions and 19 deletions
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15
django/forms/formsets.py
View File

@ -433,16 +433,21 @@ class BaseFormSet:
def formset_factory(form, formset=BaseFormSet, extra=1, can_order=False,
can_delete=False, max_num=None, validate_max=False,
min_num=None, validate_min=False):
min_num=None, validate_min=False, absolute_max=None):
"""Return a FormSet for the given form class."""
if min_num is None:
min_num = DEFAULT_MIN_NUM
if max_num is None:
max_num = DEFAULT_MAX_NUM
# hard limit on forms instantiated, to prevent memory-exhaustion attacks
# limit is simply max_num + DEFAULT_MAX_NUM (which is 2*DEFAULT_MAX_NUM
# if max_num is None in the first place)
absolute_max = max_num + DEFAULT_MAX_NUM
# absolute_max is a hard limit on forms instantiated, to prevent
# memory-exhaustion attacks. Default to max_num + DEFAULT_MAX_NUM
# (which is 2 * DEFAULT_MAX_NUM if max_num is None in the first place).
if absolute_max is None:
absolute_max = max_num + DEFAULT_MAX_NUM
if max_num > absolute_max:
raise ValueError(
"'absolute_max' must be greater or equal to 'max_num'."
)
attrs = {
'form': form,
'extra': extra,

10
django/forms/models.py
View File

@ -862,7 +862,8 @@ def modelformset_factory(model, form=ModelForm, formfield_callback=None,
can_order=False, max_num=None, fields=None, exclude=None,
widgets=None, validate_max=False, localized_fields=None,
labels=None, help_texts=None, error_messages=None,
min_num=None, validate_min=False, field_classes=None):
min_num=None, validate_min=False, field_classes=None,
absolute_max=None):
"""Return a FormSet class for the given Django model class."""
meta = getattr(form, 'Meta', None)
if (getattr(meta, 'fields', fields) is None and
@ -879,7 +880,8 @@ def modelformset_factory(model, form=ModelForm, formfield_callback=None,
error_messages=error_messages, field_classes=field_classes)
FormSet = formset_factory(form, formset, extra=extra, min_num=min_num, max_num=max_num,
can_order=can_order, can_delete=can_delete,
validate_min=validate_min, validate_max=validate_max)
validate_min=validate_min, validate_max=validate_max,
absolute_max=absolute_max)
FormSet.model = model
return FormSet
@ -1048,7 +1050,8 @@ def inlineformset_factory(parent_model, model, form=ModelForm,
can_delete=True, max_num=None, formfield_callback=None,
widgets=None, validate_max=False, localized_fields=None,
labels=None, help_texts=None, error_messages=None,
min_num=None, validate_min=False, field_classes=None):
min_num=None, validate_min=False, field_classes=None,
absolute_max=None):
"""
Return an ``InlineFormSet`` for the given kwargs.
@ -1078,6 +1081,7 @@ def inlineformset_factory(parent_model, model, form=ModelForm,
'help_texts': help_texts,
'error_messages': error_messages,
'field_classes': field_classes,
'absolute_max': absolute_max,
}
FormSet = modelformset_factory(model, **kwargs)
FormSet.fk = fk

6
docs/ref/forms/formsets.txt
View File

@ -11,8 +11,12 @@ Formset API reference. For introductory material about formsets, see the
``formset_factory``
===================
.. function:: formset_factory(form, formset=BaseFormSet, extra=1, can_order=False, can_delete=False, max_num=None, validate_max=False, min_num=None, validate_min=False)
.. function:: formset_factory(form, formset=BaseFormSet, extra=1, can_order=False, can_delete=False, max_num=None, validate_max=False, min_num=None, validate_min=False, absolute_max=None)
Returns a ``FormSet`` class for the given ``form`` class.
See :doc:`formsets </topics/forms/formsets>` for example usage.
.. versionchanged:: 3.2
The ``absolute_max`` argument was added.

16
docs/ref/forms/models.txt
View File

@ -52,7 +52,7 @@ Model Form API reference. For introductory material about model forms, see the
``modelformset_factory``
========================
.. function:: modelformset_factory(model, form=ModelForm, formfield_callback=None, formset=BaseModelFormSet, extra=1, can_delete=False, can_order=False, max_num=None, fields=None, exclude=None, widgets=None, validate_max=False, localized_fields=None, labels=None, help_texts=None, error_messages=None, min_num=None, validate_min=False, field_classes=None)
.. function:: modelformset_factory(model, form=ModelForm, formfield_callback=None, formset=BaseModelFormSet, extra=1, can_delete=False, can_order=False, max_num=None, fields=None, exclude=None, widgets=None, validate_max=False, localized_fields=None, labels=None, help_texts=None, error_messages=None, min_num=None, validate_min=False, field_classes=None, absolute_max=None)
Returns a ``FormSet`` class for the given ``model`` class.
@ -62,16 +62,20 @@ Model Form API reference. For introductory material about model forms, see the
through to :func:`~django.forms.models.modelform_factory`.
Arguments ``formset``, ``extra``, ``max_num``, ``can_order``,
``can_delete`` and ``validate_max`` are passed through to
:func:`~django.forms.formsets.formset_factory`. See :doc:`formsets
``can_delete``, ``validate_max``, and ``absolute_max`` are passed through
to :func:`~django.forms.formsets.formset_factory`. See :doc:`formsets
</topics/forms/formsets>` for details.
See :ref:`model-formsets` for example usage.
.. versionchanged:: 3.2
The ``absolute_max`` argument was added.
``inlineformset_factory``
=========================
.. function:: inlineformset_factory(parent_model, model, form=ModelForm, formset=BaseInlineFormSet, fk_name=None, fields=None, exclude=None, extra=3, can_order=False, can_delete=True, max_num=None, formfield_callback=None, widgets=None, validate_max=False, localized_fields=None, labels=None, help_texts=None, error_messages=None, min_num=None, validate_min=False, field_classes=None)
.. function:: inlineformset_factory(parent_model, model, form=ModelForm, formset=BaseInlineFormSet, fk_name=None, fields=None, exclude=None, extra=3, can_order=False, can_delete=True, max_num=None, formfield_callback=None, widgets=None, validate_max=False, localized_fields=None, labels=None, help_texts=None, error_messages=None, min_num=None, validate_min=False, field_classes=None, absolute_max=None)
Returns an ``InlineFormSet`` using :func:`modelformset_factory` with
defaults of ``formset=``:class:`~django.forms.models.BaseInlineFormSet`,
@ -81,3 +85,7 @@ Model Form API reference. For introductory material about model forms, see the
the ``parent_model``, you must specify a ``fk_name``.
See :ref:`inline-formsets` for example usage.
.. versionchanged:: 3.2
The ``absolute_max`` argument was added.

5
docs/releases/3.2.txt
View File

@ -136,7 +136,10 @@ File Uploads
Forms
~~~~~
* ...
* The new ``absolute_max`` argument for :func:`.formset_factory`,
:func:`.inlineformset_factory`, and :func:`.modelformset_factory` allows
customizing the maximum number of forms that can be instantiated when
supplying ``POST`` data. See :ref:`formsets-absolute-max` for more details.
Generic Views
~~~~~~~~~~~~~

42
docs/topics/forms/formsets.txt
View File

@ -126,6 +126,38 @@ affect validation. If ``validate_max=True`` is passed to the
:func:`~django.forms.formsets.formset_factory`, then ``max_num`` will affect
validation. See :ref:`validate_max`.
.. _formsets-absolute-max:
Limiting the maximum number of instantiated forms
=================================================
.. versionadded:: 3.2
The ``absolute_max`` parameter to :func:`.formset_factory` allows limiting the
number of forms that can be instantiated when supplying ``POST`` data. This
protects against memory exhaustion attacks using forged ``POST`` requests::
>>> from django.forms.formsets import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, absolute_max=1500)
>>> data = {
... 'form-TOTAL_FORMS': '1501',
... 'form-INITIAL_FORMS': '0',
... 'form-MAX_NUM_FORMS': '',
... }
>>> formset = ArticleFormSet(data)
>>> len(formset.forms)
1500
>>> formset.is_valid()
False
>>> formset.non_form_errors()
['Please submit 1000 or fewer forms.']
When ``absolute_max`` is None, it defaults to ``max_num + 1000``. (If
``max_num`` is ``None``, it defaults to ``2000``).
If ``absolute_max`` is less than ``max_num``, a ``ValueError`` will be raised.
Formset validation
==================
@ -348,11 +380,11 @@ excessive.
.. note::
Regardless of ``validate_max``, if the number of forms in a data set
exceeds ``max_num`` by more than 1000, then the form will fail to validate
as if ``validate_max`` were set, and additionally only the first 1000
forms above ``max_num`` will be validated. The remainder will be
truncated entirely. This is to protect against memory exhaustion attacks
using forged POST requests.
exceeds ``absolute_max``, then the form will fail to validate as if
``validate_max`` were set, and additionally only the first ``absolute_max``
forms will be validated. The remainder will be truncated entirely. This is
to protect against memory exhaustion attacks using forged POST requests.
See :ref:`formsets-absolute-max`.
``validate_min``
----------------

49
tests/forms_tests/tests/test_formsets.py
View File

@ -892,6 +892,55 @@ class FormsFormsetTestCase(SimpleTestCase):
)
self.assertEqual(formset.absolute_max, 2000)
def test_absolute_max(self):
data = {
'form-TOTAL_FORMS': '2001',
'form-INITIAL_FORMS': '0',
'form-MAX_NUM_FORMS': '0',
}
AbsoluteMaxFavoriteDrinksFormSet = formset_factory(
FavoriteDrinkForm,
absolute_max=3000,
)
formset = AbsoluteMaxFavoriteDrinksFormSet(data=data)
self.assertIs(formset.is_valid(), True)
self.assertEqual(len(formset.forms), 2001)
# absolute_max provides a hard limit.
data['form-TOTAL_FORMS'] = '3001'
formset = AbsoluteMaxFavoriteDrinksFormSet(data=data)
self.assertIs(formset.is_valid(), False)
self.assertEqual(len(formset.forms), 3000)
self.assertEqual(
formset.non_form_errors(),
['Please submit 1000 or fewer forms.'],
)
def test_absolute_max_with_max_num(self):
data = {
'form-TOTAL_FORMS': '1001',
'form-INITIAL_FORMS': '0',
'form-MAX_NUM_FORMS': '0',
}
LimitedFavoriteDrinksFormSet = formset_factory(
FavoriteDrinkForm,
max_num=30,
absolute_max=1000,
)
formset = LimitedFavoriteDrinksFormSet(data=data)
self.assertIs(formset.is_valid(), False)
self.assertEqual(len(formset.forms), 1000)
self.assertEqual(
formset.non_form_errors(),
['Please submit 30 or fewer forms.'],
)
def test_absolute_max_invalid(self):
msg = "'absolute_max' must be greater or equal to 'max_num'."
for max_num in [None, 31]:
with self.subTest(max_num=max_num):
with self.assertRaisesMessage(ValueError, msg):
formset_factory(FavoriteDrinkForm, max_num=max_num, absolute_max=30)
def test_more_initial_form_result_in_one(self):
"""
One form from initial and extra=3 with max_num=2 results in the one

78
tests/model_formsets/tests.py
View File

@ -1838,3 +1838,81 @@ class TestModelFormsetOverridesTroughFormMeta(TestCase):
form = BookFormSet.form(data={'title': 'Foo ' * 30, 'author': author.id})
self.assertIs(Book._meta.get_field('title').__class__, models.CharField)
self.assertIsInstance(form.fields['title'], forms.SlugField)
def test_modelformset_factory_absolute_max(self):
AuthorFormSet = modelformset_factory(Author, fields='__all__', absolute_max=1500)
data = {
'form-TOTAL_FORMS': '1501',
'form-INITIAL_FORMS': '0',
'form-MAX_NUM_FORMS': '0',
}
formset = AuthorFormSet(data=data)
self.assertIs(formset.is_valid(), False)
self.assertEqual(len(formset.forms), 1500)
self.assertEqual(
formset.non_form_errors(),
['Please submit 1000 or fewer forms.'],
)
def test_modelformset_factory_absolute_max_with_max_num(self):
AuthorFormSet = modelformset_factory(
Author,
fields='__all__',
max_num=20,
absolute_max=100,
)
data = {
'form-TOTAL_FORMS': '101',
'form-INITIAL_FORMS': '0',
'form-MAX_NUM_FORMS': '0',
}
formset = AuthorFormSet(data=data)
self.assertIs(formset.is_valid(), False)
self.assertEqual(len(formset.forms), 100)
self.assertEqual(
formset.non_form_errors(),
['Please submit 20 or fewer forms.'],
)
def test_inlineformset_factory_absolute_max(self):
author = Author.objects.create(name='Charles Baudelaire')
BookFormSet = inlineformset_factory(
Author,
Book,
fields='__all__',
absolute_max=1500,
)
data = {
'book_set-TOTAL_FORMS': '1501',
'book_set-INITIAL_FORMS': '0',
'book_set-MAX_NUM_FORMS': '0',
}
formset = BookFormSet(data, instance=author)
self.assertIs(formset.is_valid(), False)
self.assertEqual(len(formset.forms), 1500)
self.assertEqual(
formset.non_form_errors(),
['Please submit 1000 or fewer forms.'],
)
def test_inlineformset_factory_absolute_max_with_max_num(self):
author = Author.objects.create(name='Charles Baudelaire')
BookFormSet = inlineformset_factory(
Author,
Book,
fields='__all__',
max_num=20,
absolute_max=100,
)
data = {
'book_set-TOTAL_FORMS': '101',
'book_set-INITIAL_FORMS': '0',
'book_set-MAX_NUM_FORMS': '0',
}
formset = BookFormSet(data, instance=author)
self.assertIs(formset.is_valid(), False)
self.assertEqual(len(formset.forms), 100)
self.assertEqual(
formset.non_form_errors(),
['Please submit 20 or fewer forms.'],
)