=============================
 Deploying Docutils Securely
=============================

:Author: David Goodger
:Contact: docutils-develop@lists.sourceforge.net
:Date: $Date: 2020-09-14 12:26:03 +0200 (Mo, 14. Sep 2020) $
:Revision: $Revision: 8565 $
:Copyright: This document has been placed in the public domain.

.. contents::

Introduction
============

Initially, Docutils was intended for command-line tools and
single-user applications.  Through-the-web editing and processing was
not envisaged, therefore web security was not a consideration.  Once
Docutils/reStructuredText started being incorporated into an
ever-increasing number of web applications (blogs__, wikis__, content
management systems, and others), several security issues arose and
have been addressed.  This document provides instructions to help you
secure the Docutils software in your applications.

Docutils does not come in a through-the-web secure state, because this
would inconvenience ordinary users.

__ ../../FAQ.html#are-there-any-weblog-blog-projects-that-use-restructuredtext-syntax
__ ../../FAQ.html#are-there-any-wikis-that-use-restructuredtext-syntax


The Issues
==========

External Data Insertion
-----------------------

There are several `reStructuredText directives`_ that can insert
external data (files and URLs) into the immediate document.  These
directives are:

* "include_", by its very nature
* "raw_", through its ``:file:`` and ``:url:`` options
* "csv-table_", through its ``:file:`` and ``:url:`` options

The "include_" directive and the other directives' file insertion
features can be disabled by setting "file_insertion_enabled_" to
0/false.

.. _reStructuredText directives: ../ref/rst/directives.html
.. _include: ../ref/rst/directives.html#include
.. _raw: ../ref/rst/directives.html#raw-directive
.. _csv-table: ../ref/rst/directives.html#csv-table
.. _file_insertion_enabled: ../user/config.html#file-insertion-enabled


Raw HTML Insertion
------------------

The "raw_" directive is intended for the insertion of
non-reStructuredText data that is passed untouched to the Writer.
This directive can be abused to bypass site features or insert
malicious JavaScript code into a web page.  The "raw_" directive can
be disabled by setting "raw_enabled_" to 0/false.

.. _raw_enabled: ../user/config.html#raw-enabled


CPU and memory utilization
--------------------------

Parsing complex reStructuredText documents may require high processing
ressources. This enables `Denial of Service` attacs using specially crafted
input.

It is recommended to enforce limits for the computation time and resource
utilization of the Docutils process when processing untrusted input.

In addition, the "line_length_limit_" can be adapted.

.. _line_length_limit: ../user/config.html#line-length-limit


Securing Docutils
=================

Programmatically Via Application Default Settings
-------------------------------------------------

If your application calls Docutils via one of the `convenience
functions`_, you can pass a dictionary of default settings that
override the component defaults::

    defaults = {'file_insertion_enabled': 0,
                'raw_enabled': 0}
    output = docutils.core.publish_string(
        ..., settings_overrides=defaults)

Note that these defaults can be overridden by configuration files (and
command-line options if applicable).  If this is not desired, you can
disable configuration file processing with the ``_disable_config``
setting::

    defaults = {'file_insertion_enabled': 0,
                'raw_enabled': 0,
                '_disable_config': 1}
    output = docutils.core.publish_string(
        ..., settings_overrides=defaults)

.. _convenience functions: ../api/publisher.html


Via a Configuration File
------------------------

You may secure Docutils via a configuration file:

* if your application executes one of the `Docutils front-end tools`_
  as a separate process;
* if you cannot or choose not to alter the source code of your
  application or the component that calls Docutils; or
* if you want to secure all Docutils deployments system-wide.

If you call Docutils programmatically, it may be preferable to use the
methods described in the section above.

Docutils automatically looks in three places for a configuration file:

* ``/etc/docutils.conf``, for system-wide configuration,
* ``./docutils.conf`` (in the current working directory), for
  project-specific configuration, and
* ``~/.docutils`` (in the user's home directory), for user-specific
  configuration.

These locations can be overridden by the ``DOCUTILSCONFIG``
environment variable.  Details about configuration files, the purpose
of the various locations, and ``DOCUTILSCONFIG`` are available in the
`"Configuration Files"`_ section of `Docutils Configuration`_.

To fully secure a recent Docutils installation, the configuration file
should contain the following lines::

    [general]
    file-insertion-enabled: off
    raw-enabled: no

.. _Docutils front-end tools: ../user/tools.html
.. _"Configuration Files": ../user/config.html#configuration-files
.. _Docutils Configuration: ../user/config.html


Version Applicability
=====================

The ``file_insertion_enabled`` & ``raw_enabled`` settings were added
to Docutils 0.3.9; previous versions will ignore these settings. 

A bug existed in the configuration file handling of these settings in
Docutils 0.4 and earlier: the right-hand-side of the  (the
values) needed to be left blank::
   
       [general]
       file-insertion-enabled:
       raw-enabled:

The bug was fixed with the 0.4.1 release on 2006-11-12.


Related Documents
=================

`Docutils Runtime Settings`_ explains the relationship between
component settings specifications, application settings
specifications, configuration files, and command-line options

`Docutils Configuration`_ describes configuration files (locations,
structure, and syntax), and lists all settings and command-line
options.

.. _Docutils Runtime Settings: ../api/runtime-settings.html
