Files
@ 33b71a130b16
Branch filter:
Location: kallithea/docs/installation_puppet.rst
33b71a130b16
6.3 KiB
text/prs.fallenstein.rst
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)
<script>alert("It's a trap!");</script>
2) Escaped for insertion into HTML element or attribute context
>>> print h.escape(s)
<script>alert("It's a trap!");</script>
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.
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)
<script>alert("It's a trap!");</script>
2) Escaped for insertion into HTML element or attribute context
>>> print h.escape(s)
<script>alert("It's a trap!");</script>
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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 | .. _installation_puppet:
===================================
Installation and setup using Puppet
===================================
The whole installation and setup process of Kallithea can be simplified by
using Puppet and the `rauch/kallithea
<https://forge.puppetlabs.com/rauch/kallithea>`_ Puppet module. This is
especially useful for getting started quickly, without having to deal with all
the Python specialities.
.. note:: The following instructions assume you are not familiar with Puppet at
all. If this is not the case, you should probably skip directly to the
`Kallithea Puppet module documentation
<https://forge.puppetlabs.com/rauch/kallithea#puppet-kallithea>`_.
Installing Puppet
-----------------
This installation variant requires a Unix/Linux type server with Puppet 3.0+
installed. Many major distributions have Puppet in their standard repositories.
Thus, you will probably be ready to go by running, e.g. ``apt-get install
puppet`` or ``yum install puppet``, depending on your distro's favoured package
manager. Afterwards, check the Puppet version by running ``puppet --version``
and ensure you have at least 3.0.
If your distribution does not provide Puppet packages or you need a
newer version, please see the `Puppet Reference Manual
<https://docs.puppetlabs.com/puppet/4.2/reference/install_linux.html>`_ for
instructions on how to install Puppet on your target platform.
Installing the Puppet module
----------------------------
To install the latest version of the Kallithea Puppet module from the Puppet
Forge, run the following as ``root``:
.. code-block:: bash
puppet module install rauch/kallithea
This will install both the Kallithea Puppet module and its dependency modules.
.. warning:: Be aware that Puppet can do all kinds of things to your systems.
Third-party modules (like the ``kallithea`` module) may run
arbitrary commands on your system (most of the time as the
``root`` user), so do not apply them on production machines if
you don't know what you are doing. Instead, use a test system
(e.g. a virtual machine) for evaluation purposes.
Applying the module
-------------------
To trigger the actual installation process, we have to *apply* the
``kallithea`` Puppet class, which is provided by the module we have just
installed, to our system. For this, create a file named e.g. ``kallithea.pp``,
a *Puppet manifest*, with the following content:
.. _simple_manifest:
.. code-block:: puppet
class { 'kallithea':
seed_db => true,
manage_git => true,
}
To apply the manifest, simply run the following (preferably as root):
.. code-block:: bash
puppet apply kallithea.pp
This will basically run through the usual Kallithea :ref:`installation` and
:ref:`setup` steps, as documented. Consult the module documentation for details
on `what the module affects
<https://forge.puppetlabs.com/rauch/kallithea#what-kallithea-affects>`_. You
can also do a *dry run* by adding the ``--noop`` option to the command.
Using parameters for customizing the setup process
--------------------------------------------------
The ``kallithea`` Puppet class provides a number of `parameters
<https://forge.puppetlabs.com/rauch/kallithea#class-kallithea>`_ for
customizing the setup process. You have seen the usage of the ``seed_db``
parameter in the :ref:`example above <simple_manifest>`, but there are more.
For example, you can specify the installation directory, the name of the user
under which Kallithea gets installed, the initial admin password, etc.
Notably, you can provide arbitrary modifications to Kallithea's configuration
file by means of the ``config_hash`` parameter.
Parameters, which have not been set explicitly, will be set to default values,
which are defined inside the ``kallithea`` Puppet module. For example, if you
just stick to the defaults as in the :ref:`example above <simple_manifest>`,
you will end up with a Kallithea instance, which
- is installed in ``/srv/kallithea``, owned by the user ``kallithea``
- uses the Kallithea default configuration
- uses the admin user ``admin`` with password ``adminpw``
- is started automatically and enabled on boot
As of Kallithea 0.3.0, this in particular means that Kallithea will use an
SQLite database and listen on ``http://localhost:5000``.
See also the `full parameters list
<https://forge.puppetlabs.com/rauch/kallithea#class-kallithea>`_ for more
information.
Making your Kallithea instance publicly available
-------------------------------------------------
If you followed the instructions above, the Kallithea instance will be
listening on ``http://localhost:5000`` and therefore not publicly available.
There are several ways to change this.
The direct way
^^^^^^^^^^^^^^
The simplest setup is to instruct Kallithea to listen on another IP address
and/or port by using the ``config_hash`` parameter of the Kallithea Puppet
class. For example, assume we want to listen on all interfaces on port 80:
.. code-block:: puppet
class { 'kallithea':
seed_db => true,
config_hash => {
"server:main" => {
'host' => '0.0.0.0',
'port' => '80',
}
}
}
Using Apache as reverse proxy
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In a more advanced setup, you might instead want use a full-blown web server
like Apache HTTP Server as the public web server, configured such that requests
are internally forwarded to the local Kallithea instance (a so called *reverse
proxy setup*). This can be easily done with Puppet as well:
First, install the `puppetlabs/apache
<https://forge.puppetlabs.com/puppetlabs/apache>`_ Puppet module as above by running the following as root:
.. code-block:: bash
puppet module install puppetlabs/apache
Then, append the following to your manifest:
.. code-block:: puppet
include apache
apache::vhost { 'kallithea.example.com':
docroot => '/var/www/html',
manage_docroot => false,
port => 80,
proxy_preserve_host => true,
proxy_pass => [
{
path => '/',
url => 'http://localhost:5000/',
},
],
}
Applying the resulting manifest will install the Apache web server and setup a
virtual host acting as a reverse proxy for your local Kallithea instance.
|