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[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.
This commit is contained in:
Aymeric Augustin 2013-02-12 11:22:41 +01:00
parent d3a45e10c8
commit d7094bbce8
4 changed files with 88 additions and 19 deletions
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12
django/forms/formsets.py
View File

@ -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):

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

@ -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

4
docs/topics/forms/modelforms.txt
View File

@ -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
-------------------------------

85
tests/regressiontests/forms/tests/formsets.py
View File

@ -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), """<input type="hidden" name="choices-TOTAL_FORMS" value="1" /><input type="hidden" name="choices-INITIAL_FORMS" value="0" /><input type="hidden" name="choices-MAX_NUM_FORMS" />
self.assertEqual(str(formset), """<input type="hidden" name="choices-TOTAL_FORMS" value="1" /><input type="hidden" name="choices-INITIAL_FORMS" value="0" /><input type="hidden" name="choices-MAX_NUM_FORMS" value="1000" />
<tr><th>Choice:</th><td><input type="text" name="choices-0-choice" /></td></tr>
<tr><th>Votes:</th><td><input type="text" name="choices-0-votes" /></td></tr>""")
@ -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())