From d7094bbce8cb838f3b40f504f198c098ff1cf727 Mon Sep 17 00:00:00 2001 From: Aymeric Augustin Date: Tue, 12 Feb 2013 11:22:41 +0100 Subject: [PATCH] [1.3.x] Added a default limit to the maximum number of forms in a formset. This is a security fix. Disclosure and advisory coming shortly. --- django/forms/formsets.py | 12 ++- docs/topics/forms/formsets.txt | 6 +- docs/topics/forms/modelforms.txt | 4 +- tests/regressiontests/forms/tests/formsets.py | 85 ++++++++++++++++--- 4 files changed, 88 insertions(+), 19 deletions(-) diff --git a/django/forms/formsets.py b/django/forms/formsets.py index da92fbd408..da1ce7fe92 100644 --- a/django/forms/formsets.py +++ b/django/forms/formsets.py @@ -16,6 +16,9 @@ MAX_NUM_FORM_COUNT = 'MAX_NUM_FORMS' ORDERING_FIELD_NAME = 'ORDER' DELETION_FIELD_NAME = 'DELETE' +# default maximum number of forms in a formset, to prevent memory exhaustion +DEFAULT_MAX_NUM = 1000 + class ManagementForm(Form): """ ``ManagementForm`` is used to keep track of how many form instances @@ -104,7 +107,7 @@ class BaseFormSet(StrAndUnicode): def _construct_forms(self): # instantiate all the forms and put them in self.forms self.forms = [] - for i in xrange(self.total_form_count()): + for i in xrange(min(self.total_form_count(), self.absolute_max)): self.forms.append(self._construct_form(i)) def _construct_form(self, i, **kwargs): @@ -348,9 +351,14 @@ class BaseFormSet(StrAndUnicode): def formset_factory(form, formset=BaseFormSet, extra=1, can_order=False, can_delete=False, max_num=None): """Return a FormSet for the given form class.""" + if max_num is None: + max_num = DEFAULT_MAX_NUM + # hard limit on forms instantiated, to prevent memory-exhaustion attacks + # limit defaults to DEFAULT_MAX_NUM, but developer can increase it via max_num + absolute_max = max(DEFAULT_MAX_NUM, max_num) attrs = {'form': form, 'extra': extra, 'can_order': can_order, 'can_delete': can_delete, - 'max_num': max_num} + 'max_num': max_num, 'absolute_max': absolute_max} return type(form.__name__ + 'FormSet', (formset,), attrs) def all_valid(formsets): diff --git a/docs/topics/forms/formsets.txt b/docs/topics/forms/formsets.txt index a3721fdcdf..078597e14d 100644 --- a/docs/topics/forms/formsets.txt +++ b/docs/topics/forms/formsets.txt @@ -102,8 +102,10 @@ If the value of ``max_num`` is greater than the number of existing objects, up to ``extra`` additional blank forms will be added to the formset, so long as the total number of forms does not exceed ``max_num``. -A ``max_num`` value of ``None`` (the default) puts no limit on the number of -forms displayed. Please note that the default value of ``max_num`` was changed +A ``max_num`` value of ``None`` (the default) puts a high limit on the number +of forms displayed (1000). In practice this is equivalent to no limit. + +Please note that the default value of ``max_num`` was changed from ``0`` to ``None`` in version 1.2 to allow ``0`` as a valid value. Formset validation diff --git a/docs/topics/forms/modelforms.txt b/docs/topics/forms/modelforms.txt index 24e000ece0..04b0d76b64 100644 --- a/docs/topics/forms/modelforms.txt +++ b/docs/topics/forms/modelforms.txt @@ -691,8 +691,8 @@ so long as the total number of forms does not exceed ``max_num``:: .. versionchanged:: 1.2 -A ``max_num`` value of ``None`` (the default) puts no limit on the number of -forms displayed. +A ``max_num`` value of ``None`` (the default) puts a high limit on the number +of forms displayed (1000). In practice this is equivalent to no limit. Using a model formset in a view ------------------------------- diff --git a/tests/regressiontests/forms/tests/formsets.py b/tests/regressiontests/forms/tests/formsets.py index 4451fc76b1..f50c2b28c7 100644 --- a/tests/regressiontests/forms/tests/formsets.py +++ b/tests/regressiontests/forms/tests/formsets.py @@ -1,5 +1,5 @@ # -*- coding: utf-8 -*- -from django.forms import Form, CharField, IntegerField, ValidationError, DateField +from django.forms import Form, CharField, IntegerField, ValidationError, DateField, formsets from django.forms.formsets import formset_factory, BaseFormSet from django.utils.unittest import TestCase @@ -47,7 +47,7 @@ class FormsFormsetTestCase(TestCase): # for adding data. By default, it displays 1 blank form. It can display more, # but we'll look at how to do so later. formset = ChoiceFormSet(auto_id=False, prefix='choices') - self.assertEqual(str(formset), """ + self.assertEqual(str(formset), """ Choice: Votes:""") @@ -623,8 +623,8 @@ class FormsFormsetTestCase(TestCase): # Limiting the maximum number of forms ######################################## # Base case for max_num. - # When not passed, max_num will take its default value of None, i.e. unlimited - # number of forms, only controlled by the value of the extra parameter. + # When not passed, max_num will take a high default value, leaving the + # number of forms only controlled by the value of the extra parameter. LimitedFavoriteDrinkFormSet = formset_factory(FavoriteDrinkForm, extra=3) formset = LimitedFavoriteDrinkFormSet() @@ -671,8 +671,8 @@ class FormsFormsetTestCase(TestCase): def test_max_num_with_initial_data(self): # max_num with initial data - # When not passed, max_num will take its default value of None, i.e. unlimited - # number of forms, only controlled by the values of the initial and extra + # When not passed, max_num will take a high default value, leaving the + # number of forms only controlled by the value of the initial and extra # parameters. initial = [ @@ -805,6 +805,65 @@ class FormsFormsetTestCase(TestCase): self.assertEqual(str(reverse_formset[1]), str(forms[-2])) self.assertEqual(len(reverse_formset), len(forms)) + def test_hard_limit_on_instantiated_forms(self): + """A formset has a hard limit on the number of forms instantiated.""" + # reduce the default limit of 1000 temporarily for testing + _old_DEFAULT_MAX_NUM = formsets.DEFAULT_MAX_NUM + try: + formsets.DEFAULT_MAX_NUM = 3 + ChoiceFormSet = formset_factory(Choice) + # someone fiddles with the mgmt form data... + formset = ChoiceFormSet( + { + 'choices-TOTAL_FORMS': '4', + 'choices-INITIAL_FORMS': '0', + 'choices-MAX_NUM_FORMS': '4', + 'choices-0-choice': 'Zero', + 'choices-0-votes': '0', + 'choices-1-choice': 'One', + 'choices-1-votes': '1', + 'choices-2-choice': 'Two', + 'choices-2-votes': '2', + 'choices-3-choice': 'Three', + 'choices-3-votes': '3', + }, + prefix='choices', + ) + # But we still only instantiate 3 forms + self.assertEqual(len(formset.forms), 3) + finally: + formsets.DEFAULT_MAX_NUM = _old_DEFAULT_MAX_NUM + + def test_increase_hard_limit(self): + """Can increase the built-in forms limit via a higher max_num.""" + # reduce the default limit of 1000 temporarily for testing + _old_DEFAULT_MAX_NUM = formsets.DEFAULT_MAX_NUM + try: + formsets.DEFAULT_MAX_NUM = 3 + # for this form, we want a limit of 4 + ChoiceFormSet = formset_factory(Choice, max_num=4) + formset = ChoiceFormSet( + { + 'choices-TOTAL_FORMS': '4', + 'choices-INITIAL_FORMS': '0', + 'choices-MAX_NUM_FORMS': '4', + 'choices-0-choice': 'Zero', + 'choices-0-votes': '0', + 'choices-1-choice': 'One', + 'choices-1-votes': '1', + 'choices-2-choice': 'Two', + 'choices-2-votes': '2', + 'choices-3-choice': 'Three', + 'choices-3-votes': '3', + }, + prefix='choices', + ) + # This time four forms are instantiated + self.assertEqual(len(formset.forms), 4) + finally: + formsets.DEFAULT_MAX_NUM = _old_DEFAULT_MAX_NUM + + data = { 'choices-TOTAL_FORMS': '1', # the number of forms rendered 'choices-INITIAL_FORMS': '0', # the number of forms with initial data @@ -900,12 +959,12 @@ class TestIsBoundBehavior(TestCase): # The empty forms should be equal. self.assertEqual(empty_forms[0].as_p(), empty_forms[1].as_p()) -class TestEmptyFormSet(TestCase): +class TestEmptyFormSet(TestCase): "Test that an empty formset still calls clean()" - def test_empty_formset_is_valid(self): - EmptyFsetWontValidateFormset = formset_factory(FavoriteDrinkForm, extra=0, formset=EmptyFsetWontValidate) - formset = EmptyFsetWontValidateFormset(data={'form-INITIAL_FORMS':'0', 'form-TOTAL_FORMS':'0'},prefix="form") - formset2 = EmptyFsetWontValidateFormset(data={'form-INITIAL_FORMS':'0', 'form-TOTAL_FORMS':'1', 'form-0-name':'bah' },prefix="form") - self.assertFalse(formset.is_valid()) - self.assertFalse(formset2.is_valid()) + def test_empty_formset_is_valid(self): + EmptyFsetWontValidateFormset = formset_factory(FavoriteDrinkForm, extra=0, formset=EmptyFsetWontValidate) + formset = EmptyFsetWontValidateFormset(data={'form-INITIAL_FORMS':'0', 'form-TOTAL_FORMS':'0'},prefix="form") + formset2 = EmptyFsetWontValidateFormset(data={'form-INITIAL_FORMS':'0', 'form-TOTAL_FORMS':'1', 'form-0-name':'bah' },prefix="form") + self.assertFalse(formset.is_valid()) + self.assertFalse(formset2.is_valid())