templates: properly escape inline JavaScript values TLDR: Kallithea has issues with escaping values for use in inline JS. Despite judicious poking of the code, no actual security vulnerabilities have been found, just lots of corner-case bugs. This patch fixes those, and hardens the code against actual security issues. The long version: To embed a Python value (typically a 'unicode' plain-text value) in a larger file, it must be escaped in a context specific manner. Example: >>> s = u'<script>alert("It\'s a trap!");</script>' 1) Escaped for insertion into HTML element context >>> print cgi.escape(s) &lt;script&gt;alert("It's a trap!");&lt;/script&gt; 2) Escaped for insertion into HTML element or attribute context >>> print h.escape(s) &lt;script&gt;alert(&#34;It&#39;s a trap!&#34;);&lt;/script&gt; This is the default Mako escaping, as usually used by Kallithea. 3) Encoded as JSON >>> print json.dumps(s) "<script>alert(\"It's a trap!\");</script>" 4) Escaped for insertion into a JavaScript file >>> print '(' + json.dumps(s) + ')' ("<script>alert(\"It's a trap!\");</script>") The parentheses are not actually required for strings, but may be needed to avoid syntax errors if the value is a number or dict (object). 5) Escaped for insertion into a HTML inline <script> element >>> print h.js(s) ("\x3cscript\x3ealert(\"It's a trap!\");\x3c/script\x3e") Here, we need to combine JS and HTML escaping, further complicated by the fact that "<script>" tag contents can either be parsed in XHTML mode (in which case '<', '>' and '&' must additionally be XML escaped) or HTML mode (in which case '</script>' must be escaped, but not using HTML escaping, which is not available in HTML "<script>" tags). Therefore, the XML special characters (which can only occur in string literals) are escaped using JavaScript string literal escape sequences. (This, incidentally, is why modern web security best practices ban all use of inline JavaScript...) Unsurprisingly, Kallithea does not do (5) correctly. In most cases, Kallithea might slap a pair of single quotes around the HTML escaped Python value. A typical benign example: $('#child_link').html('${_('No revisions')}'); This works in English, but if a localized version of the string contains an apostrophe, the result will be broken JavaScript. In the more severe cases, where the text is user controllable, it leaves the door open to injections. In this example, the script inserts the string as HTML, so Mako's implicit HTML escaping makes sense; but in many other cases, HTML escaping is actually an error, because the value is not used by the script in an HTML context. The good news is that the HTML escaping thwarts attempts at XSS, since it's impossible to inject syntactically valid JavaScript of any useful complexity. It does allow JavaScript errors and gibberish to appear on the page, though. In these cases, the escaping has been fixed to use either the new 'h.js' helper, which does JavaScript escaping (but not HTML escaping), OR the new 'h.jshtml' helper (which does both), in those cases where it was unclear if the value might be used (by the script) in an HTML context. Some of these can probably be "relaxed" from h.jshtml to h.js later, but for now, using h.jshtml fixes escaping and doesn't introduce new errors. In a few places, Kallithea JSON encodes values in the controller, then inserts the JSON (without any further escaping) into <script> tags. This is also wrong, and carries actual risk of XSS vulnerabilities. However, in all cases, security vulnerabilities were narrowly avoided due to other filtering in Kallithea. (E.g. many special characters are banned from appearing in usernames.) In these cases, the escaping has been fixed and moved to the template, making it immediately visible that proper escaping has been performed. Mini-FAQ (frequently anticipated questions): Q: Why do everything in one big, hard to review patch? Q: Why add escaping in specific case FOO, it doesn't seem needed? Because the goal here is to have "escape everywhere" as the default policy, rather than identifying individual bugs and fixing them one by one by adding escaping where needed. As such, this patch surely introduces a lot of needless escaping. This is no different from how Mako/Pylons HTML escape everything by default, even when not needed: it's errs on the side of needless work, to prevent erring on the side of skipping required (and security critical) work. As for reviewability, the most important thing to notice is not where escaping has been introduced, but any places where it might have been missed (or where h.jshtml is needed, but h.js is used). Q: The added escaping is kinda verbose/ugly. That is not a question, but yes, I agree. Hopefully it'll encourage us to move away from inline JavaScript altogether. That's a significantly larger job, though; with luck this patch will keep us safe and secure until such a time as we can implement the real fix. Q: Why not use Mako filter syntax ("${val|h.js}")? Because of long-standing Mako bug #140, preventing use of 'h' in filters. Q: Why not work around bug #140, or even use straight "${val|js}"? Because Mako still applies the default h.escape filter before the explicitly specified filters. Q: Where do we go from here? Longer term, we should stop doing variable expansions in script blocks, and instead pass data to JS via e.g. data attributes, or asynchronously using AJAX calls. Once we've done that, we can remove inline JavaScript altogether in favor of separate script files, and set a strict Content Security Policy explicitly blocking inline scripting, and thus also the most common kind of cross-site scripting attack.

.. _installation:

==========================
Installation on Unix/Linux
==========================

The following describes three different ways of installing Kallithea:

- :ref:`installation-source`: The simplest way to keep the installation
  up-to-date and track any local customizations is to run directly from
  source in a Kallithea repository clone, preferably inside a virtualenv
  virtual Python environment.

- :ref:`installation-virtualenv`: If you prefer to only use released versions
  of Kallithea, the recommended method is to install Kallithea in a virtual
  Python environment using `virtualenv`. The advantages of this method over
  direct installation is that Kallithea and its dependencies are completely
  contained inside the virtualenv (which also means you can have multiple
  installations side by side or remove it entirely by just removing the
  virtualenv directory) and does not require root privileges.

- :ref:`installation-without-virtualenv`: The alternative method of installing
  a Kallithea release is using standard pip. The package will be installed in
  the same location as all other Python packages you have ever installed. As a
  result, removing it is not as straightforward as with a virtualenv, as you'd
  have to remove its dependencies manually and make sure that they are not
  needed by other packages.

Regardless of the installation method you may need to make sure you have
appropriate development packages installed, as installation of some of the
Kallithea dependencies requires a working C compiler and libffi library
headers. Depending on your configuration, you may also need to install
Git and development packages for the database of your choice.

For Debian and Ubuntu, the following command will ensure that a reasonable
set of dependencies is installed::

    sudo apt-get install build-essential git python-pip python-virtualenv libffi-dev python-dev

For Fedora and RHEL-derivatives, the following command will ensure that a
reasonable set of dependencies is installed::

    sudo yum install gcc git python-pip python-virtualenv libffi-devel python-devel

.. _installation-source:


Installation from repository source
-----------------------------------

To install Kallithea in a virtualenv_ using the stable branch of the development
repository, follow the instructions below::

        hg clone https://kallithea-scm.org/repos/kallithea -u stable
        cd kallithea
        virtualenv ../kallithea-venv
        . ../kallithea-venv/bin/activate
        pip install --upgrade pip setuptools
        pip install -e .
        python2 setup.py compile_catalog   # for translation of the UI

You can now proceed to :ref:`setup`.

.. _installation-virtualenv:


Installing a released version in a virtualenv
---------------------------------------------

It is highly recommended to use a separate virtualenv_ for installing Kallithea.
This way, all libraries required by Kallithea will be installed separately from your
main Python installation and other applications and things will be less
problematic when upgrading the system or Kallithea.
An additional benefit of virtualenv_ is that it doesn't require root privileges.

- Assuming you have installed virtualenv_, create a new virtual environment
  for example, in `/srv/kallithea/venv`, using the virtualenv command::

    virtualenv /srv/kallithea/venv

- Activate the virtualenv_ in your current shell session and make sure the
  basic requirements are up-to-date by running::

    . /srv/kallithea/venv/bin/activate
    pip install --upgrade pip setuptools

.. note:: You can't use UNIX ``sudo`` to source the ``virtualenv`` script; it
   will "activate" a shell that terminates immediately. It is also perfectly
   acceptable (and desirable) to create a virtualenv as a normal user.

.. note:: Some dependencies are optional. If you need them, install them in
   the virtualenv too::

     pip install psycopg2
     pip install python-ldap

   This might require installation of development packages using your
   distribution's package manager.

- Make a folder for Kallithea data files, and configuration somewhere on the
  filesystem. For example::

    mkdir /srv/kallithea

- Go into the created directory and run this command to install Kallithea::

    pip install kallithea

  Alternatively, download a .tar.gz from http://pypi.python.org/pypi/Kallithea,
  extract it and run::

    pip install .

- This will install Kallithea together with all other required
  Python libraries into the activated virtualenv.

You can now proceed to :ref:`setup`.

.. _installation-without-virtualenv:


Installing a released version without virtualenv
------------------------------------------------

For installation without virtualenv, 'just' use::

    pip install kallithea

Note that this method requires root privileges and will install packages
globally without using the system's package manager.

To install as a regular user in ``~/.local``, you can use::

    pip install --user kallithea

You can now proceed to :ref:`setup`.


.. _virtualenv: http://pypi.python.org/pypi/virtualenv