Bleaching¶

When an end user copies rich text from other applications into Lino, the text can contain styles and other things that cause side effects when displaying or printing them. Or a malicious user might deliberately insert HTML with scripts or other diabolic things in order to harm your server. In order to avoid such problems, we remove any dangerous parts from content that gets entered into a rich text field using the web interface. This process is called to “sanitize” or to “bleach”.

This page contains code snippets (lines starting with >>>), which are being tested during our development workflow. The following snippet initializes the demo project used throughout this page.

>>> import os
>>> from lino_book.projects.noi1r.startup import *

Usage ¶

All rich text fields (RichHtmlField To activate bleaching of all rich text fields (:class:`RichHtmlField), get bleached by default. To deactivate this feature, set textfield_bleached to False in your settings.py file:

textfield_bleached = False

You might also set textfield_bleached to False, but keep in mind that this is only the default value.

The application developer can force bleaching to be activated or not for a specific field by explicitly saying a bleached argument when declaring the field.

How to bleach existing unbleached data ¶

The lino.modlib.system.BleachChecker data checker reports fields whose content would change by bleach. This is useful when you activate Bleaching on a site with existing data. After activating bleach, you can check for unbleached content by saying:

$ django-admin checkdata system.BleachChecker

After this you can use the web interface to inspect the data problems. To manually bleach a single database object, simply save it using the web interface. You should make sure that bleach does not remove any content which is actually needed. If this happens, you must manually restore the content of the tested database objects, or restore a full backup and then set your bleach_allowed_tags setting.

To bleach all existing data, you can say:

$ django-admin checkdata system.BleachChecker --fix

Which mdels have bleachable fields?¶

Which models have bleachable fields?

>>> checker = checkdata.Checkers.get_by_value('system.BleachChecker')
>>> lst = [str(m) for m in checker.get_checkable_models()]
>>> print('\n'.join(sorted(lst)))
<class 'lino.modlib.comments.models.Comment'>
<class 'lino.modlib.tinymce.models.TextFieldTemplate'>
<class 'lino_noi.lib.groups.models.Group'>
<class 'lino_noi.lib.tickets.models.Ticket'>
<class 'lino_xl.lib.accounting.models.PaymentTerm'>
<class 'lino_xl.lib.products.models.Category'>
<class 'lino_xl.lib.products.models.Product'>
<class 'lino_xl.lib.topics.models.Interest'>
<class 'lino_xl.lib.trading.models.InvoiceItem'>
<class 'lino_xl.lib.working.models.Session'>

Processing embedded images ¶

This section verifies that the lino.utils.soup.sanitize() function has the side effect of potentially creating uploads.Upload database rows.

Prepare the test examples:

>>> import base64
>>> import lino_book
>>> from pathlib import Path
>>> logo_file = Path(lino_book.__file__).parent.parent / 'docs/data/pr/lino-pen.png'
>>> with logo_file.open('rb') as f:
...     logo = base64.b64encode(f.read()).decode('ascii')

>>> from lino.core.gfks import gfk2lookup
>>> def tidy_up():
...     # find this file and delete it.
...     for u in uploads.Upload.objects.order_by('-pk').all():
...         deletable = False
...         if u.file:
...             with u.file.open('rb') as f:
...                 if base64.b64encode(f.read()).decode('ascii') == logo:
...                     deletable = True
...         if deletable:
...             Comment = comments.Comment
...             Comment.objects.filter(**gfk2lookup(Comment.owner, u)).delete()
...             u.file.delete()
...             u.delete()

>>> tidy_up()

>>> imageDataURL = f"data:image/png;base64,{logo}"

>>> ses = rt.login('robin')
>>> content = f"""\
... <p>Here is an image:</p>
... <p><img src="{imageDataURL}" class="bar"></p>\
... """
>>> from lino.utils.soup import sanitize
>>> print(sanitize(content, save=True, ar=ses))
...
<p>Here is an image:</p>
<p>[file ...]</p>

>>> content = f"""\
... <p>Here is an image without src attribute:</p>
... <p><img class="bar"></p>\
... """
>>> print(sanitize(content, save=True, ar=ses))
...
<p>Here is an image without src attribute:</p>
<p><img class="bar"/></p>

>>> tidy_up()
>>> dd.is_installed('uploads')
True

Restify ¶

The restify function converts reSTructuredText markup into HTML.

>>> from lino.utils.restify import restify
>>> print(restify("A *greatly* **formatted** text: \n\n- one \n\n -two"))
...
<p>A <em>greatly</em> <strong>formatted</strong> text:</p>
<ul class="simple">
<li>one</li>
</ul>
<blockquote>
-two</blockquote>

Historical notes ¶

Until November 2024, we used the bleach Python package for sanitizing HTML input. But this package had been deprecated in January 2023. Now we use our own function lino.utils.soup.sanitize(), which relies on BeautifulSoup and is inspired by a blog post by Chase Seibert.

bleach until 20170225 required html5lib` version 0.9999999 (7*”9”) while the current version is 0.999999999 (9*”9”). Which means that you might inadvertently break bleach when you ask to update html5lib:

$ pip install -U html5lib
...
Successfully installed html5lib-0.999999999
$ python -m bleach
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 163, in _run_module_as_main
    mod_name, _Error)
  File "/usr/lib/python2.7/runpy.py", line 111, in _get_module_details
    __import__(mod_name)  # Do not catch exceptions initializing package
  File "/site-packages/bleach/__init__.py", line 14, in <module>
    from html5lib.sanitizer import HTMLSanitizer
ImportError: No module named sanitizer

Bleaching¶

Usage¶

How to bleach existing unbleached data¶

Which mdels have bleachable fields?¶

Processing embedded images¶

Restify¶

Historical notes¶

Usage ¶

How to bleach existing unbleached data ¶

Processing embedded images ¶

Restify ¶

Historical notes ¶