django-constrainedfilefield 5.0.0
This Django app adds a new field type, ConstrainedFileField, that has the capability of checking the document size and type.
License: BSD
Keywords: django filefield validation file

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ConstrainedFileField for Django
===============================

This Django app adds a new field type, ``ConstrainedFileField``, that
has the capability of checking the file size and type. Also provides a
javascript checker for the form field.

Features
--------

-  File size limitation
-  File type limitation
-  Javascript file size checker

Requirements
------------

-  `Python <https://www.python.org/>`__ >= 3.5
-  `Django <https://www.djangoproject.com/>`__>= 2.2.28
-  ``python-magic`` >= 0.4.2 *iff* you want to check the file type

Installation
------------

Using PyPI
~~~~~~~~~~

1. Run

   -  ``pip install django-constrainedfilefield``, or
   -  ``pip install django-constrainedfilefield[filetype]`` to ensure
      ``python-magic`` is installed.

2. For windows, you must download the dll files and .magic file at
   https://github.com/pidydx/libmagicwin64 (32-bit version:
   http://gnuwin32.sourceforge.net/packages/file.htm)), add them to
   C:\Windows\System32 (or to a folder in your PATH), and set
   MAGIC_FILE_PATH=“…” to the path of your .magic file in your
   settings.py. For more information about the files to download, go to:
   https://github.com/ahupp/python-magic/blob/43df08c5ed63d7aad839695f311ca1be2eeb1ecb/README.md#dependencies

Using the source code
~~~~~~~~~~~~~~~~~~~~~

1. Make sure `Pandoc <http://pandoc.org/index.html>`__ is installed
2. Run ``./pypi_packager.sh``
3. Run
   ``pip install dist/django_constrainedfilefield-x.y.z-[...].wheel``,
   where ``x.y.z`` must be replaced by the actual version number and
   ``[...]`` depends on your packaging configuration
4. For windows, you must download the dll files and .magic file at
   https://github.com/pidydx/libmagicwin64 (32-bit version:
   http://gnuwin32.sourceforge.net/packages/file.htm)), add them to
   C:\Windows\System32 (or to a folder in your PATH), and set
   MAGIC_FILE_PATH=“…” to the path of your .magic file in your
   settings.py. For more information about the files to download, go to:
   https://github.com/ahupp/python-magic/blob/43df08c5ed63d7aad839695f311ca1be2eeb1ecb/README.md#dependencies

Usage
-----

Validate single file
~~~~~~~~~~~~~~~~~~~~

The field can be used in forms or model forms like a normal
``FileField``. If a user tries to upload a file which is too large or
without a valid type, a form validation error will occur.

Note that the validation does not occur on the field itself (on
``save()``), but when validated through a form.

Creating form from model
^^^^^^^^^^^^^^^^^^^^^^^^

Create a model and add a field of type ``ConstrainedFileField``. You can
add a maximum size in bytes and a list of valid mime types that will be
allowed. The list of all mime types is available here:
http://www.iana.org/assignments/media-types/index.html. Setting none of
the above, it behaves like a regular ``FileField``.

::

   from django.db import models
   from constrainedfilefield.fields import ConstrainedFileField

   class TestModel(models.Model):
       the_file = ConstrainedFileField(
                               null=True,
                               blank=True,
                               upload_to='testfile',
                               content_types=['image/png'],
                               max_upload_size=10240
                                       )

::

   from django import forms
   from myproject.models import TestModel

   class TestModelForm(forms.ModelForm):
       class Meta:
           model = TestModel
           fields = ['the_file']

Building a form
^^^^^^^^^^^^^^^

::

   from django import forms
   from constrainedfilefield.fields import ConstrainedFileField

   class TestNoModelForm(forms.Form):
       the_file = ConstrainedFileField(
                               null=True,
                               blank=True,
                               upload_to='testfile',
                               content_types=['image/png'],
                               max_upload_size=10240
                                       ).formfield()

Javascript file size validation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Additionally, to prevent user uploading too large files, a javascript
checker can be set to the form field. In order to achieve that, you need
to

1. Add ``constrainedfilefield`` to the ``INSTALLED_APPS``. This will
   load the javascripts from the static files.

2. Activate this feature by setting ``js_checker=True`` when
   instantiating the ``ConstrainedFileField``.

3. Include the javascript in the template where the form field is used

   .. code:: django

      {% load static %}
      <script src="{% static 'constrainedfilefield/js/file_checker.js' %}"></script>

Validate single image
~~~~~~~~~~~~~~~~~~~~~

Same as above, using ``ConstrainedImageFileField`` instead.

The ``ConstrainedImageField`` offers additional constraints: \*
``[min|max]_upload_[width|height]`` to define min/max dimensions,
respectively width and height.

Note on DOS attacks
-------------------

Important note: the check of the file size is made by Django once the
whole file has been uploaded to the server and stored in a temp
directory (or in memory if the file is small). Thus, this is useful to
guarantee the quota of the users, for example, but will not stop an
attacking user that wants to block the server by sending huge files (e.
g. of several Gb).

To avoid this, you need to configure your front end to limit the size of
uploaded files. How to do it depends on the software you are using. For
example, if you use apache, you should use
`LimitRequestBody <http://httpd.apache.org/docs/2.2/mod/core.html#limitrequestbody>`__
directive.

This is a complementary measure, because you’ll usually want normal
users that exceed the size by a reasonable amount to get a friendly form
validation message, while attacking users will see how their connection
is abruptly cut before the file finishes uploading. So the recommended
setting is to give ``max_upload_size`` a small value (e.g. 5Mb) and
``LimitRequestBody`` a higher one (e.g. 100Mb).

Credits
-------

This is a fork of
`django-validated-file <https://github.com/kaleidos/django-validated-file>`__
from `Kaleidos <https://github.com/kaleidos>`__.

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