path: root/doc/librejs.info

This is librejs.info, produced by makeinfo version 6.0 from
librejs.texi.

This manual is for GNU LibreJS (version 6.0.10, 25 October 2015), a GNU
IceCat extension to detect and block nonfree nontrivial JavaScript on
webpages.

   Copyright (C) 2011 2012 2014 2015 Loic J. Duros

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.3 or any later version published by the Free Software
     Foundation; with no Invariant Sections, with no Front-Cover Texts,
     and with no Back-Cover Texts.  A copy of the license is included in
     the section entitled "GNU Free Documentation License".
INFO-DIR-SECTION GNUzilla
START-INFO-DIR-ENTRY
* LibreJS: (librejs).               Detect nonfree nontrivial in GNU Icecat
END-INFO-DIR-ENTRY


File: librejs.info,  Node: Top,  Next: Overview,  Up: (dir)

LibreJS
*******

This manual is for GNU LibreJS (version 6.0.10, 25 October 2015).

* Menu:

* Overview::                            General purpose and information.
* Disclaimer::                          Emphasize what LibreJS does and does not.
* Installation::                        Installing LibreJS from source.
* How to Use::                          How to use LibreJS in IceCat.
* JavaScript Detection::                How LibreJS detects nontrivial Javascript.
* Free Licenses Detection::             List of licenses detected by LibreJS.
* Setting Your JavaScript Free::        Information for website owners/maintainers.
* LibreJS Development Notes::           Documentation about the development of
                                        LibreJS itself.
* Installation Requirements::           Requirements to build and install LibreJS.
* LibreJS Internals::                   How LibreJS works under the hood.
* Tests::                               Test LibreJS and better understand it.
* GNU Free Documentation License::      Copying and sharing this documentation.


File: librejs.info,  Node: Overview,  Next: Disclaimer,  Prev: Top,  Up: Top

1 Overview
**********

GNU LibreJS --an add-on for GNU IceCat and Mozilla Firefox-- detects and
blocks nonfree nontrivial JavaScript while allowing its execution on
pages containing code that is either trivial and/or free.

   Many websites run nontrivial JavaScript on your computer.  Some use
it for complex tasks; many use it gratuitously for minor jobs that could
be done easily with plain HTML. Sometimes this JavaScript code is
malicious.  Either way, the JavaScript code is often nonfree.  For
explanation of the issue, see "The JavaScript
Trap"(<http://www.gnu.org/philosophy/javascript-trap.html>).

   If you care about freedom in your computing, and don't wish to let
all and sundry make you run nonfree programs, now you can prevent it by
using LibreJS.


File: librejs.info,  Node: Disclaimer,  Next: Installation,  Prev: Overview,  Up: Top

2 Disclaimer
************

   * LibreJS is not a security tool.  Its goal is to detect nonfree
     nontrivial JavaScript, and it currently does not detect whether
     free or trivial code is malicious or not.  Other free Mozilla
     extensions and add-ons may be available for this purpose.

   * LibreJS is always a work in progress.  If you find a bug, please
     report it to <bug-librejs@gnu.org>.


File: librejs.info,  Node: Installation,  Next: How to Use,  Prev: Disclaimer,  Up: Top

3 Installation
**************

You can install LibreJS directly using a generated 'librejs.xpi' file,
or by building it from source.

3.1 Building the Package
========================

After installing 'jpm', you should be able to use the 'make' command to
build LibreJS from source.

   After running 'make', a new file, 'librejs.xpi' should be generated.
This is the file that can be installed in a Mozilla browser.

3.2 Installing LibreJS
======================

To install the add-on for all users, run:
     sudo make install

   or as root:
     make install

   Next time you open a Mozilla-browser as a user of your system, you
should be notified that a new add-on (in this case, LibreJS) as been
installed and whether to allow it to run or not.


File: librejs.info,  Node: How to Use,  Next: JavaScript Detection,  Prev: Installation,  Up: Top

4 How to Use
************

4.1 LibreJS in action
=====================

After installing the add-on, you will see the LibreJS widget in the
add-on bar at the bottom of the browser window.  After loading a page,
left-click on the widget to view the deactivated JavaScript code from
the page (both on page and external) and, if applicable, the scripts
that were accepted.

4.2 Complaint Feature
=====================

It is very important to complain when a site has nonfree JavaScript
code, especially if it won't work without that code.  LibreJS makes it
easy to complain by heuristically finding where to send the complaint.

   When nonfree/nontrivial code is detected in a page, LibreJS attempts
to find a relevant contact link or email for the website you are
visiting.  In order to do so, it will attempt to visit a few links from
the current page (for instance, a link labeled "contact" on the same
domain as the current page, ...)

   LibreJS detects contact pages, email addresses that are likely to be
owned by the maintainer of the site, Twitter and identi.ca links, and
phone numbers.

   After LibreJS detects any of the above, a "Complain" tab will appear
on the right of your web browser.  When you click on this tab, a large
panel will appear with contact information.  Ideally, at the top you
will find the email address of the maintainer, labeled as the "Email you
should use".

   When you complain to the website for their nonfree nontrivial
JavaScript, provide them with the link to the JavaScript Trap essay so
that they can get more information on what the issue is and how they can
solve it on their own site.

   LibreJS includes a default subject line and body for the complaint
email, with a link to the JavaScript Trap essay.  This can be configured
in the LibreJS add-on preferences in your web browser.

4.3 Options
===========

"Whitelist"
     LibreJS lets you whitelist domain names and subdomains to bypass
     the regular JavaScript check.  This might be useful, for example,
     if you are running your own code in a local web server.  In order
     to add a whitelisted domain or url, go to Tools >> Add-ons, or
     press 'Control + Shift + A'.  Inside the add-on window, click on
     "Extensions", and in the list, where you see LibreJS, click on the
     "Preferences" button.  You will see an input field labeled
     "Whitelist".  In the field, enter comma-separated domain names.  Do
     not enter the protocol.  For instance to whitelist all the pages of
     <http://www.gnu.org> and <https://gnu.org>, enter 'gnu.org'.  To
     allow all subdomains from gnu.org, enter: '*.gnu.org'.  This will
     match such sites as <http://savannah.gnu.org> and
     <http://audio-video.gnu.org>.

"Complaint tab"
     This specifies whether the complaint tab appears when a site is
     running nonfree JavaScript.

"Display notifications of JavaScript analysis"
     This option enables an info bar of realtime JavaScript analysis.

"Complaint email subject"
     Configure the default subject used in complaint emails.

"Complaint email body"
     Configure the default body used in complaint emails.


File: librejs.info,  Node: JavaScript Detection,  Next: Free Licenses Detection,  Prev: How to Use,  Up: Top

5 JavaScript Detection
**********************

     LibreJS considers JavaScript on a page nontrivial if any of the
     following are true:

   * It makes an AJAX request or is loaded along with scripts that make
     an AJAX request,

   * It loads external scripts dynamically or is loaded along with
     scripts that do,

   * It defines functions or methods and either loads an external script
     (from HTML) or is loaded as one,

   * It uses dynamic JavaScript constructs that are difficult to analyze
     without interpreting the program or is loaded along with scripts
     that use such constructs.  These constructs are:
        * Using the eval function
        * Calling methods with the square bracket notation
        * Using any other construct than a string literal with certain
          methods ('Obj.write', 'Obj.createElement', ...).

   In practice, the JavaScript code in your page may be found trivial by
LibreJS if, as a whole:

   * It does not define functions and it does not load external scripts
     (with the HTML src attribute in a '<script>' tag).

   * It does not make AJAX calls.

   * It does not load external scripts with dynamic constructs.

   * It does not use constructs that may be used to do any of the above
     in a non-obvious way (use of the 'eval()' method, use of square
     bracket method calls, use of concatenation with certain constructs
     or method calls, ...).

   However, in some instances, you may be required by LibreJS to add a
stylized comment to JavaScript code that may be otherwise trivial.

   When an external file defines a function, it becomes available to all
other external scripts.  That is the case if another script defines a
function that makes AJAX calls, when an external script loads other
scripts dynamically (which in turn could also make AJAX calls, ...), or
when a script is written with constructs that may do any of these.

   For instance, if your page contains the following:
     <script src="jquery.js"></script>
     <script>
     $.doSomething();
     </script>

   While '$.doSomething();' may seem trivial, you will nevertheless have
to add a stylized license comment on your main HTML page because the
external script (in this case jQuery) has been found to define methods
that make AJAX calls.  '$.doSomething()' might make an AJAX call, and
LibreJS does not check for that.  The rule of thumb is that when you use
a library or code that handles AJAX, JSON, JSONP, the loading of scripts
dynamically, you should have license mentions for all your JavaScript
files and for your main page regardless.  In practice this is a case
that happens very often with code that uses libraries.

   In practice also, the JavaScript code in an external file (an
external '.js' file loaded on your page) may be found trivial if it does
not define functions/methods.

   And in the same manner it will be considered nontrivial if AJAX
calls, dynamic script loading, or non-obvious dynamic JavaScript
constructs are used in another script.

   If your JavaScript code makes AJAX requests, it's important to get an
accurate "Content-Type" in the response from the server.  For example,
if you're using JSON, set it to 'application/json'.  This is because
LibreJS alters the content of 'text/html' responses.


File: librejs.info,  Node: Free Licenses Detection,  Next: Setting Your JavaScript Free,  Prev: JavaScript Detection,  Up: Top

6 Free Licenses Detection
*************************

6.1 Detected Free Licenses
==========================

In order for a file to be detected as free, the license notice should
appear in a JavaScript file above all code, at the very top of the file.

   For inline JavaScript code inside '<script>' tags in HTML pages, the
license notice should appear once per page as a comment inside a
'<script>' tag, before all the code in that script.  When the only
inline JavaScript code is within element attributes ('onload',
'onclick'), place the license notice in an otherwise empty '<script>' at
the top of the page.  This is sometimes needed when an external script
performs AJAX calls or embeds scripts dynamically, and the only inline
JavaScript is an event attribute making a method call, e.g.: '<body
onload="methodCall('remote-data.xml');">'

   When people speak of the "MIT license" they mean either the X11
license or the Expat license.  Please see which license the code uses,
and label it accordingly.

   Currently LibreJS checks for the following licenses:

   * Apache License, Version 2.0
        * Identifier: 'Apache-2.0'
        * URL: <http://www.apache.org/licenses/LICENSE-2.0>
        * Magnet link:
          'magnet:?xt=urn:btih:8e4f440f4c65981c5bf93c76d35135ba5064d8b7&dn=apache-2.0.txt'

   * Artistic License 2.0
        * URL: <http://www.perlfoundation.org/artistic_license_2_0>
        * Magnet link:
          'magnet:?xt=urn:btih:54fd2283f9dbdf29466d2df1a98bf8f65cafe314&dn=artistic-2.0.txt'

   * Boost Software License
        * URL: <http://www.boost.org/LICENSE_1_0.txt>
        * Magnet link:
          'magnet:?xt=urn:btih:89a97c535628232f2f3888c2b7b8ffd4c078cec0&dn=Boost-1.0.txt'

   * BSD 3-Clause License
        * URL: <http://opensource.org/licenses/BSD-3-Clause>
        * Magnet link:
          'magnet:?xt=urn:btih:c80d50af7d3db9be66a4d0a86db0286e4fd33292&dn=bsd-3-clause.txt'

   * CPAL 1.0
        * Identifier: 'CPAL-1.0'
        * URL: <http://opensource.org/licenses/cpal_1.0>
        * Magnet link:
          'magnet:?xt=urn:btih:84143bc45939fc8fa42921d619a95462c2031c5c&dn=cpal-1.0.txt'

   * Creative Commons CC0 1.0 Universal
        * Identifier: 'CC0-1.0'
        * URL:
          <http://creativecommons.org/publicdomain/zero/1.0/legalcode>
        * Magnet link:
          'magnet:?xt=urn:btih:90dc5c0be029de84e523b9b3922520e79e0e6f08&dn=cc0.txt'

   * Eclipse Public License 1.0
        * Identifier: 'EPL-1.0'
        * URL: <http://www.eclipse.org/legal/epl-v10.html>
        * Magnet link:
          'magnet:?xt=urn:btih:4c6a2ad0018cd461e9b0fc44e1b340d2c1828b22&dn=epl-1.0.txt'

   * Expat License (sometimes called the MIT license)
        * Identifier: 'Expat'
        * URL: <http://www.jclark.com/xml/copying.txt>
        * Magnet link:
          'magnet:?xt=urn:btih:d3d9a9a6595521f9666a5e94cc830dab83b65699&dn=expat.txt'

   * FreeBSD License
        * URL: <http://www.freebsd.org/copyright/freebsd-license.html>
        * Magnet link:
          'magnet:?xt=urn:btih:87f119ba0b429ba17a44b4bffcab33165ebdacc0&dn=freebsd.txt'

   * GNU General Public License (GPL) version 2
        * Identifier: 'GPL-2.0'
        * URL: <http://www.gnu.org/licenses/gpl-2.0.html>
        * Magnet link:
          'magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&dn=gpl-2.0.txt'

   * GNU General Public License (GPL) version 3
        * Identifier: 'GPL-3.0'
        * URL: <http://www.gnu.org/licenses/gpl-3.0.html>
        * Magnet link:
          'magnet:?xt=urn:btih:1f739d935676111cfff4b4693e3816e664797050&dn=gpl-3.0.txt'

   * GNU Lesser General Public License, version 2.1
        * Identifier: 'LGPL-2.1'
        * URL: <http://www.gnu.org/licenses/lgpl-2.1.html>
        * Magnet link:
          'magnet:?xt=urn:btih:5de60da917303dbfad4f93fb1b985ced5a89eac2&dn=lgpl-2.1.txt'

   * GNU Lesser General Public License, version 3
        * Identifier: 'LGPL-3.0'
        * URL: <http://www.gnu.org/licenses/lgpl-3.0.html>
        * Magnet link:
          'magnet:?xt=urn:btih:0ef1b8170b3b615170ff270def6427c317705f85&dn=lgpl-3.0.txt'

   * GNU Affero General Public License, version 3
        * Identifier: 'AGPL-3.0'
        * URL: <http://www.gnu.org/licenses/agpl-3.0.html>
        * Magnet link:
          'magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt'

   * The ISC License
        * URL:
          <https://www.isc.org/downloads/software-support-policy/isc-license/>
        * Magnet link:
          'magnet:?xt=urn:btih:b8999bbaf509c08d127678643c515b9ab0836bae&dn=ISC.txt'

   * Mozilla Public License 2.0
        * Identifier: 'MPL-2.0'
        * URL: <http://www.mozilla.org/MPL/2.0>
        * Magnet link:
          'magnet:?xt=urn:btih:3877d6d54b3accd4bc32f8a48bf32ebc0901502a&dn=mpl-2.0.txt'

   * Public Domain
        * Public domain is not a license (see
          <https://www.gnu.org/licenses/license-list.html#PublicDomain>).
          If you want to release your work to the public domain, the FSF
          recommends using CC0.
        * Magnet Link:
          'magnet:?xt=urn:btih:e95b018ef3580986a04669f1b5879592219e2a7a&dn=public-domain.txt'

   * Universal Permissive License
        * Identifier: 'UPL-1.0'
        * URL: <https://oss.oracle.com/licenses/upl/>
        * Magnet link:
          'magnet:?xt=urn:btih:478974f4d41c3fa84c4befba25f283527fad107d&dn=upl-1.0.txt'

   * WTFPL
        * Identifier: 'WTFPL'
        * URL: <http://www.wtfpl.net/txt/copying/>
        * Magnet link:
          'magnet:?xt=urn:btih:723febf9f6185544f57f0660a41489c7d6b4931b&dn=wtfpl.txt'

   * Unlicense
        * Identifier: 'Unlicense'
        * URL: <http://unlicense.org/UNLICENSE>
        * Magnet link:
          'magnet:?xt=urn:btih:5ac446d35272cc2e4e85e4325b146d0b7ca8f50c&dn=unlicense.txt'

   * X11 License
        * URL: <http://www.xfree86.org/3.3.6/COPYRIGHT2.html#3>
        * Magnet link:
          'magnet:?xt=urn:btih:5305d91886084f776adcf57509a648432709a7c7&dn=x11.txt'

   * XFree86 License
        * Identifier: 'Modified-BSD'
        * URLs: <http://www.xfree86.org/3.3.6/COPYRIGHT2.html#3>
          <http://www.xfree86.org/current/LICENSE4.html>
        * Magnet link:
          'magnet:?xt=urn:btih:12f2ec9e8de2a3b0002a33d518d6010cc8ab2ae9&dn=xfree86.txt'

6.2 Undetected Free Licenses
============================

If you are using a free license that isn't detected by LibreJS and isn't
listed in the previous section, please send a message to
<bug-librejs@gnu.org> regarding this license, where code released under
this license can be found, and where to find the license text and
information.

   Many free licenses are listed in this page:
<http://www.gnu.org/licenses/license-list.html>


File: librejs.info,  Node: Setting Your JavaScript Free,  Next: LibreJS Development Notes,  Prev: Free Licenses Detection,  Up: Top

7 Setting Your JavaScript Free
******************************

The first step is releasing your JavaScript under a free license.  If
you are already using a free library, or you're not using any
third-party libraries, it might only take a few minutes.

   All JavaScript code on a web page (inline, on-page, and external)
shares a common scope.  Thus, code is generally either rejected or
accepted as a whole by LibreJS. If some JavaScript code is found to be
nontrivial and nonfree, then most of the time, all the the rest is
discarded as well.

   On your website, take a look at your HTML source.  You can identify
distinct pieces of JavaScript that might be free and some other that are
nonfree.

   _Tip_: By running LibreJS on your page, you will get a list of all
the JavaScript that was blocked.  This gives you an overview of the
JavaScript in your page.

   Imagine a page that contains several pieces of JavaScript from
various sources:
   * On top, within the '<head>' tag, it includes jQuery

   * Then, some JavaScript code that you have written

   * At the bottom, a JavaScript-based Facebook widget

   * Also, there's some analytics tracking code

"JavaScript that is already free"
     First, you must ensure that the library is free.  If the file
     contains a copyright and a license notice, you won't need to look
     any further.  But if there's no mention of the license, or if it's
     too brief, you'll have to look for a COPYING or LICENSE file within
     the original library's source package, or on the library's official
     website.

"Your own JavaScript"
     The free license given to your code should be compatible with the
     rest of the JavaScript on a page.  A good way to check is to read
     up on them: <http://www.gnu.org/licenses/license-list.html>

"Nonfree JavaScript"
     This might be the case with an analytics tracker, social media
     widgets, and code that runs ads.  Removing these pieces of code
     from your site is required to have the rest accepted as free.
     There are often alternatives to nonfree libraries or to third-party
     services:

        * If you have used nonfree third-party code as the base to write
          your own code, try to find a free alternative.

        * If you're using a third-party service such as an analytics
          service, replace it with a free alternative like Piwik.

        * If you can't find free JavaScript that has already been
          developed, write it yourself!  Who knows, your own solution
          might be the start of a brilliant project!

7.1 JavaScript Web Labels
=========================

One way to make your website work with LibreJS is by defining a
JavaScript Web Labels table.

   A JavaScript Web Labels table is informative to both site visitors
and the LibreJS program.  You make a Web Labels table on a new HTML page
that's linked to from your main page.  The table lists each of your
site's JavaScript files, that file's corresponding human-readable source
file, and the canonical url of its free license.

   When using a JavaScript Web Labels table for your own files, it's
important to put a copying permission statement at the top of each
source file listed in right-most column of the Web Labels table.  For
info on how properly release your code as free software, see
<https://www.gnu.org/licenses/gpl-howto.html>.  Future versions of
LibreJS will require a copying permission statement or other license
notice for source files listed in a Web Labels table.

   More information on JavaScript Web Labels is detailed here:
<https://www.gnu.org/software/librejs/free-your-javascript.html#step3>
and here: <https://www.gnu.org/licenses/javascript-labels.html>.

7.1.1 Specifying multiple licenses for a single JavaScript file
---------------------------------------------------------------

If you compile or concatenate your JavaScript into a single file, the
source files you're combining may be released under different licenses.
You can specify multiple licenses for the file in a JavaScript Web
Labels table, like this:

<table id="jslicense-labels1">
    <tr>
        <td><a href="all.min.js">all.min.js</a></td>
        <td>
            <a href="http://www.gnu.org/licenses/gpl-3.0.html"
                >GPL-3.0+</a>
            <br />
            <a href="http://www.apache.org/licenses/LICENSE-2.0"
                >Apache-2.0</a>
        </td>
        <td>
            <a href="gpl-script.js">gpl-script.js</a>
            <br />
            <a href="apache-script.js">apache-script.js</a>
        </td>
    </tr>
</table>

   The '<br />' tags just make the table more understandable when
looking at the rendered version of it on the license page.  They aren't
required by LibreJS.

   If all the licenses contained in the second column are recognized by
LibreJS to be free licenses, then LibreJS will allow the file in the
first column to be run.

7.2 Adding a stylized comment in your JavaScript files and on your page
=======================================================================

See a "Convention for releasing free JavaScript programs" in the
JavaScript Trap <http://www.gnu.org/philosophy/javascript-trap.html>

   Adding this notice will ensure LibreJS will find the JavaScript file
to be free.  The '@licstart' and '@licend' lines at the beginning and
end of the stylized comment are necessary to make a clear statement that
the _entire code_ in the file is free.  This means that you must ensure
that no nonfree code was carelessly appended at the end of the file.

   In the main HTML page, the license notice covers JavaScript contained
in all '<script>' tags with on-page code and the inline JavaScript (in
event attributes such as onload, onclick, etc, ...).  Since external
files have their own stylized comment, they are not covered by the
notice in the main HTML page.  Make sure to identify all the licenses
available.  LibreJS will only ensure it matches a notice of an allowed
license once, so the order does not matter, but the responsibility is on
you to make sure all code is under the free licenses mentioned between
'@licstart' and '@licend'.

   You should make _only_ one '@licstart' '@licend' comment in your
page, since it pertains to the entire code on page across all '<script>'
tags and inline html attributes.

When you use the JavaScript Web Labels method, you should still include
a license notice at the top of each of your source files.  This ensures
that if someone copies the file and uses it for something else, the
license remains intact.

   For more info on making your JavaScript LibreJS-compliant, see this
web page:
<https://www.gnu.org/software/librejs/free-your-javascript.html>


File: librejs.info,  Node: LibreJS Development Notes,  Next: Installation Requirements,  Prev: Setting Your JavaScript Free,  Up: Top

8 LibreJS Development Notes
***************************

8.1 Running LibreJS from the source directory
=============================================

Download 'jpm', then do something like this in the LibreJS directory:

     jpm run -b `which abrowser`

8.2 Debugging
=============

Uncomment lines 22 and 23 in 'lib/main.js' to enable printing of
'console.debug()' statements.

8.3 Adding new whitelisted libraries
====================================

Run the 'data/script_libraries/gethash.sh' script, using the URL to a
JavaScript file as the argument, then add the output of that command to
'data/script_libraries/script-libraries.json'.

8.4 Releasing a new version
===========================

Update the version number in:
   * 'configure.ac'
   * 'package.json'
   * 'doc/version.texi'
   * 'data/display_panel/content/display-panel.html'
   * 
   Then run 'make info' to build the docs with 'gendocs.sh'.
   * 'git commit' and 'git tag 6.0.4'
   * Export a tarball:
        * 'git archive --format=tar.gz --prefix=librejs-6.0.4/ 6.0.4
          >librejs-6.0.4.tar.gz'
        * 'mv librejs-6.0.4.tar.gz ~/releases/librejs-6.0.4/'
   * Make xpi file: 'jpm xpi; mv librejs.xpi librejs-6.0.4.xpi'


File: librejs.info,  Node: Installation Requirements,  Next: LibreJS Internals,  Prev: LibreJS Development Notes,  Up: Top

Appendix A Installation Requirements
************************************

A.1 Mozilla Browser
===================

You will need one of the many flavors of the Mozilla browser to use
LibreJS. It can be installed on the following:

   GNU IceCat, Mozilla Firefox, Trisquel Abrowser, Debian Iceweasel.

   LibreJS works on these browsers starting from version 29.  We
recommend that you use the latest version of your Mozilla browser.
LibreJS has been tested extensively on multiple GNU/Linux distributions,
but it is compatible any operating system as long as you're using a
compatible Mozilla browser.

A.2 Mozilla's Jetpack Manager for Node.js
=========================================

LibreJS uses the Mozilla 'jpm' tool, a set of utilities for creating,
testing, running and packaging Mozilla Jetpack Addons.

   You do not need 'jpm' to use the LibreJS xpi file or to install it
using the packaged version, but it is required in order to package the
LibreJS source code into an xpi file.  If you would like to run the
tests for LibreJS or make changes to the source files, you will need
'jpm' as well.  For the "make" command to work properly, you must have
the 'jpm' command available on your system from the command line.

   You can find information on getting 'jpm' at these links:

   <https://www.npmjs.com/package/jpm>

   <https://developer.mozilla.org/en-US/Add-ons/SDK/Tutorials/Getting_Started_%28jpm%29>

   JPM is released under the Mozilla Public License 2.0.


File: librejs.info,  Node: LibreJS Internals,  Next: Tests,  Prev: Installation Requirements,  Up: Top

Appendix B LibreJS Internals
****************************

LibreJS intercepts HTTP responses and rewrites their contents after
analyzing JavaScript within them.  It does not remove script nodes and
attributes from the page, but instead "deactivates" them by modifying
the 'type' and 'src' attributes on script elements and by moving the
contents of inline JavaScript attributes such as onClick into harmless
attributes.

   LibreJS detects the most common cases using the HTTP response method
described above, but in extremely rare cases, or when running code
locally, LibreJS cannot detect JavaScript during the response stage.

   To remedy this issue, and as a final safeguard, LibreJS takes a look
at the scripts that are about to be executed while the browser engine is
parsing the page.  If the script is not found in a list of accepted
scripts populated earlier, the execution will be prevented.  This is to
ensure content types that are not regular HTML (binhex with HTML in it,
...) and JavaScript do not fall through the cracks and get executed.


File: librejs.info,  Node: Tests,  Next: GNU Free Documentation License,  Prev: LibreJS Internals,  Up: Top

Appendix C Tests
****************

In order to better understand how LibreJS works, you can try to visit
these pages with LibreJS installed and enabled and see how they are
being processed:

   * 
     <http://lduros.net/assets/librejs/tests/trivial-inline-trivial-external/>
     This page contains trivial on-page JavaScript code, and an external
     script that contains trivial JavaScript code.  Therefore, all
     JavaScript is being executed.

   * 
     <http://lduros.net/assets/librejs/tests/trivial-inline-nontrivial-external/>
     The on-page script here is trivial and uses a built-in method, but
     the external script in this page is nontrivial (defines a
     function.)  The external script is blocked, the inline script is
     executed.

   * 
     <http://lduros.net/assets/librejs/tests/nontrivial-inline-trivial-external/>
     This page contains nontrivial code on page, and trivial code in its
     external page.  All JavaScript is _removed_ from the page, and the
     external script is never analyzed, since the nontrivial conditions
     are already met in the page.

   * <http://lduros.net/assets/librejs/tests/free-inline-free-external/>
     This page contains free on-page (GPL 3) JavaScript, and free
     external Javascript.  Therefore all JavaScript is being executed.

   * 
     <http://lduros.net/assets/librejs/tests/free-inline-nonfree-nontrivial-external/>
     This page contains free on-page JavaScript.  The external script
     contains nonfree nontrivial JavaScript (AJAX request).  The free
     code that is inline is executed, but the external file is blocked.

   * <http://lduros.net/assets/librejs/tests/intrinsec-event/> This page
     contains trivial on-page code, with an intrinsic event in an html
     attribute (onload).  All JavaScript is being executed.

   * 
     <http://lduros.net/assets/librejs/tests/trivial-inline-free-external-defines-function/>
     This page contains on-page trivial JavaScript (only makes a window
     alert and loads an external script using the html <script> tag with
     the src attribute.  The external script is free (GPL v3), and since
     it is only nontrivial because it defines a function, the on-page
     trivial code is allowed to use it.  All JavaScript is being
     executed.

   * 
     <http://lduros.net/assets/librejs/tests/trivial-inline-free-external-writes-script/>
     This page contains trivial on-page JavaScript code, and loads an
     external script that is free.  Since no function is defined, the
     external script is being analyzed.  The external script is free.
     Trivial here is not allowed because the external script, although
     free, writes a script.  The inline trivial script should also have
     a free license notice for it to be interpreted.

   * 
     <http://lduros.net/assets/librejs/tests/shelltypist/demo/real-life-example-with-jquery-free.html>
     This is a real-life example of a small jQuery plugin.  The on-page
     JavaScript code has a free license.  The jQuery external file has a
     free licensed.  The shelltypist.js file has a free license as well.
     All licenses are defined between '@licstart' and '@licend'.  All
     JavaScript is executed.

   * 
     <http://lduros.net/assets/librejs/tests/shelltypist/demo/same-page-without-free-license.html>
     This is the same page than the previous example, except it does not
     have a free license for the main HTML page on-page script.  While
     the actual code there is trivial, since jQuery defines methods that
     make use of AJAX, trivial code is not allowed, and no JavaScript is
     executed.

   * <http://lduros.net/assets/librejs/tests/test-labels/> This page
     contains JavaScript (jQuery minified) that does not have proper
     license information in the file, as it has no '@licstart' '@licend'
     comment.  It would be considered nonfree, however, the page itself
     uses the JavaScript Web Labels method.  On the page itself, you
     will find a link labeled "JavaScript License Information", which
     leads to a page that contains a properly formatted table with the
     required data on the external JavaScript file.  LibreJS visits this
     link and determines the version of jQuery linked from the original
     page is the one listed there, and flags it as free.  All JavaScript
     is executed (and the title should turn green.)


File: librejs.info,  Node: GNU Free Documentation License,  Prev: Tests,  Up: Top

Appendix D GNU Free Documentation License
*****************************************

                     Version 1.3, 3 November 2008

     Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     <http://fsf.org/>

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

  0. PREAMBLE

     The purpose of this License is to make a manual, textbook, or other
     functional and useful document "free" in the sense of freedom: to
     assure everyone the effective freedom to copy and redistribute it,
     with or without modifying it, either commercially or
     noncommercially.  Secondarily, this License preserves for the
     author and publisher a way to get credit for their work, while not
     being considered responsible for modifications made by others.

     This License is a kind of "copyleft", which means that derivative
     works of the document must themselves be free in the same sense.
     It complements the GNU General Public License, which is a copyleft
     license designed for free software.

     We have designed this License in order to use it for manuals for
     free software, because free software needs free documentation: a
     free program should come with manuals providing the same freedoms
     that the software does.  But this License is not limited to
     software manuals; it can be used for any textual work, regardless
     of subject matter or whether it is published as a printed book.  We
     recommend this License principally for works whose purpose is
     instruction or reference.

  1. APPLICABILITY AND DEFINITIONS

     This License applies to any manual or other work, in any medium,
     that contains a notice placed by the copyright holder saying it can
     be distributed under the terms of this License.  Such a notice
     grants a world-wide, royalty-free license, unlimited in duration,
     to use that work under the conditions stated herein.  The
     "Document", below, refers to any such manual or work.  Any member
     of the public is a licensee, and is addressed as "you".  You accept
     the license if you copy, modify or distribute the work in a way
     requiring permission under copyright law.

     A "Modified Version" of the Document means any work containing the
     Document or a portion of it, either copied verbatim, or with
     modifications and/or translated into another language.

     A "Secondary Section" is a named appendix or a front-matter section
     of the Document that deals exclusively with the relationship of the
     publishers or authors of the Document to the Document's overall
     subject (or to related matters) and contains nothing that could
     fall directly within that overall subject.  (Thus, if the Document
     is in part a textbook of mathematics, a Secondary Section may not
     explain any mathematics.)  The relationship could be a matter of
     historical connection with the subject or with related matters, or
     of legal, commercial, philosophical, ethical or political position
     regarding them.

     The "Invariant Sections" are certain Secondary Sections whose
     titles are designated, as being those of Invariant Sections, in the
     notice that says that the Document is released under this License.
     If a section does not fit the above definition of Secondary then it
     is not allowed to be designated as Invariant.  The Document may
     contain zero Invariant Sections.  If the Document does not identify
     any Invariant Sections then there are none.

     The "Cover Texts" are certain short passages of text that are
     listed, as Front-Cover Texts or Back-Cover Texts, in the notice
     that says that the Document is released under this License.  A
     Front-Cover Text may be at most 5 words, and a Back-Cover Text may
     be at most 25 words.

     A "Transparent" copy of the Document means a machine-readable copy,
     represented in a format whose specification is available to the
     general public, that is suitable for revising the document
     straightforwardly with generic text editors or (for images composed
     of pixels) generic paint programs or (for drawings) some widely
     available drawing editor, and that is suitable for input to text
     formatters or for automatic translation to a variety of formats
     suitable for input to text formatters.  A copy made in an otherwise
     Transparent file format whose markup, or absence of markup, has
     been arranged to thwart or discourage subsequent modification by
     readers is not Transparent.  An image format is not Transparent if
     used for any substantial amount of text.  A copy that is not
     "Transparent" is called "Opaque".

     Examples of suitable formats for Transparent copies include plain
     ASCII without markup, Texinfo input format, LaTeX input format,
     SGML or XML using a publicly available DTD, and standard-conforming
     simple HTML, PostScript or PDF designed for human modification.
     Examples of transparent image formats include PNG, XCF and JPG.
     Opaque formats include proprietary formats that can be read and
     edited only by proprietary word processors, SGML or XML for which
     the DTD and/or processing tools are not generally available, and
     the machine-generated HTML, PostScript or PDF produced by some word
     processors for output purposes only.

     The "Title Page" means, for a printed book, the title page itself,
     plus such following pages as are needed to hold, legibly, the
     material this License requires to appear in the title page.  For
     works in formats which do not have any title page as such, "Title
     Page" means the text near the most prominent appearance of the
     work's title, preceding the beginning of the body of the text.

     The "publisher" means any person or entity that distributes copies
     of the Document to the public.

     A section "Entitled XYZ" means a named subunit of the Document
     whose title either is precisely XYZ or contains XYZ in parentheses
     following text that translates XYZ in another language.  (Here XYZ
     stands for a specific section name mentioned below, such as
     "Acknowledgements", "Dedications", "Endorsements", or "History".)
     To "Preserve the Title" of such a section when you modify the
     Document means that it remains a section "Entitled XYZ" according
     to this definition.

     The Document may include Warranty Disclaimers next to the notice
     which states that this License applies to the Document.  These
     Warranty Disclaimers are considered to be included by reference in
     this License, but only as regards disclaiming warranties: any other
     implication that these Warranty Disclaimers may have is void and
     has no effect on the meaning of this License.

  2. VERBATIM COPYING

     You may copy and distribute the Document in any medium, either
     commercially or noncommercially, provided that this License, the
     copyright notices, and the license notice saying this License
     applies to the Document are reproduced in all copies, and that you
     add no other conditions whatsoever to those of this License.  You
     may not use technical measures to obstruct or control the reading
     or further copying of the copies you make or distribute.  However,
     you may accept compensation in exchange for copies.  If you
     distribute a large enough number of copies you must also follow the
     conditions in section 3.

     You may also lend copies, under the same conditions stated above,
     and you may publicly display copies.

  3. COPYING IN QUANTITY

     If you publish printed copies (or copies in media that commonly
     have printed covers) of the Document, numbering more than 100, and
     the Document's license notice requires Cover Texts, you must
     enclose the copies in covers that carry, clearly and legibly, all
     these Cover Texts: Front-Cover Texts on the front cover, and
     Back-Cover Texts on the back cover.  Both covers must also clearly
     and legibly identify you as the publisher of these copies.  The
     front cover must present the full title with all words of the title
     equally prominent and visible.  You may add other material on the
     covers in addition.  Copying with changes limited to the covers, as
     long as they preserve the title of the Document and satisfy these
     conditions, can be treated as verbatim copying in other respects.

     If the required texts for either cover are too voluminous to fit
     legibly, you should put the first ones listed (as many as fit
     reasonably) on the actual cover, and continue the rest onto
     adjacent pages.

     If you publish or distribute Opaque copies of the Document
     numbering more than 100, you must either include a machine-readable
     Transparent copy along with each Opaque copy, or state in or with
     each Opaque copy a computer-network location from which the general
     network-using public has access to download using public-standard
     network protocols a complete Transparent copy of the Document, free
     of added material.  If you use the latter option, you must take
     reasonably prudent steps, when you begin distribution of Opaque
     copies in quantity, to ensure that this Transparent copy will
     remain thus accessible at the stated location until at least one
     year after the last time you distribute an Opaque copy (directly or
     through your agents or retailers) of that edition to the public.

     It is requested, but not required, that you contact the authors of
     the Document well before redistributing any large number of copies,
     to give them a chance to provide you with an updated version of the
     Document.

  4. MODIFICATIONS

     You may copy and distribute a Modified Version of the Document
     under the conditions of sections 2 and 3 above, provided that you
     release the Modified Version under precisely this License, with the
     Modified Version filling the role of the Document, thus licensing
     distribution and modification of the Modified Version to whoever
     possesses a copy of it.  In addition, you must do these things in
     the Modified Version:

       A. Use in the Title Page (and on the covers, if any) a title
          distinct from that of the Document, and from those of previous
          versions (which should, if there were any, be listed in the
          History section of the Document).  You may use the same title
          as a previous version if the original publisher of that
          version gives permission.

       B. List on the Title Page, as authors, one or more persons or
          entities responsible for authorship of the modifications in
          the Modified Version, together with at least five of the
          principal authors of the Document (all of its principal
          authors, if it has fewer than five), unless they release you
          from this requirement.

       C. State on the Title page the name of the publisher of the
          Modified Version, as the publisher.

       D. Preserve all the copyright notices of the Document.

       E. Add an appropriate copyright notice for your modifications
          adjacent to the other copyright notices.

       F. Include, immediately after the copyright notices, a license
          notice giving the public permission to use the Modified
          Version under the terms of this License, in the form shown in
          the Addendum below.

       G. Preserve in that license notice the full lists of Invariant
          Sections and required Cover Texts given in the Document's
          license notice.

       H. Include an unaltered copy of this License.

       I. Preserve the section Entitled "History", Preserve its Title,
          and add to it an item stating at least the title, year, new
          authors, and publisher of the Modified Version as given on the
          Title Page.  If there is no section Entitled "History" in the
          Document, create one stating the title, year, authors, and
          publisher of the Document as given on its Title Page, then add
          an item describing the Modified Version as stated in the
          previous sentence.

       J. Preserve the network location, if any, given in the Document
          for public access to a Transparent copy of the Document, and
          likewise the network locations given in the Document for
          previous versions it was based on.  These may be placed in the
          "History" section.  You may omit a network location for a work
          that was published at least four years before the Document
          itself, or if the original publisher of the version it refers
          to gives permission.

       K. For any section Entitled "Acknowledgements" or "Dedications",
          Preserve the Title of the section, and preserve in the section
          all the substance and tone of each of the contributor
          acknowledgements and/or dedications given therein.

       L. Preserve all the Invariant Sections of the Document, unaltered
          in their text and in their titles.  Section numbers or the
          equivalent are not considered part of the section titles.

       M. Delete any section Entitled "Endorsements".  Such a section
          may not be included in the Modified Version.

       N. Do not retitle any existing section to be Entitled
          "Endorsements" or to conflict in title with any Invariant
          Section.

       O. Preserve any Warranty Disclaimers.

     If the Modified Version includes new front-matter sections or
     appendices that qualify as Secondary Sections and contain no
     material copied from the Document, you may at your option designate
     some or all of these sections as invariant.  To do this, add their
     titles to the list of Invariant Sections in the Modified Version's
     license notice.  These titles must be distinct from any other
     section titles.

     You may add a section Entitled "Endorsements", provided it contains
     nothing but endorsements of your Modified Version by various
     parties--for example, statements of peer review or that the text
     has been approved by an organization as the authoritative
     definition of a standard.

     You may add a passage of up to five words as a Front-Cover Text,
     and a passage of up to 25 words as a Back-Cover Text, to the end of
     the list of Cover Texts in the Modified Version.  Only one passage
     of Front-Cover Text and one of Back-Cover Text may be added by (or
     through arrangements made by) any one entity.  If the Document
     already includes a cover text for the same cover, previously added
     by you or by arrangement made by the same entity you are acting on
     behalf of, you may not add another; but you may replace the old
     one, on explicit permission from the previous publisher that added
     the old one.

     The author(s) and publisher(s) of the Document do not by this
     License give permission to use their names for publicity for or to
     assert or imply endorsement of any Modified Version.

  5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under
     this License, under the terms defined in section 4 above for
     modified versions, provided that you include in the combination all
     of the Invariant Sections of all of the original documents,
     unmodified, and list them all as Invariant Sections of your
     combined work in its license notice, and that you preserve all
     their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
     copy.  If there are multiple Invariant Sections with the same name
     but different contents, make the title of each such section unique
     by adding at the end of it, in parentheses, the name of the
     original author or publisher of that section if known, or else a
     unique number.  Make the same adjustment to the section titles in
     the list of Invariant Sections in the license notice of the
     combined work.

     In the combination, you must combine any sections Entitled
     "History" in the various original documents, forming one section
     Entitled "History"; likewise combine any sections Entitled
     "Acknowledgements", and any sections Entitled "Dedications".  You
     must delete all sections Entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other
     documents released under this License, and replace the individual
     copies of this License in the various documents with a single copy
     that is included in the collection, provided that you follow the
     rules of this License for verbatim copying of each of the documents
     in all other respects.

     You may extract a single document from such a collection, and
     distribute it individually under this License, provided you insert
     a copy of this License into the extracted document, and follow this
     License in all other respects regarding verbatim copying of that
     document.

  7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other
     separate and independent documents or works, in or on a volume of a
     storage or distribution medium, is called an "aggregate" if the
     copyright resulting from the compilation is not used to limit the
     legal rights of the compilation's users beyond what the individual
     works permit.  When the Document is included in an aggregate, this
     License does not apply to the other works in the aggregate which
     are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these
     copies of the Document, then if the Document is less than one half
     of the entire aggregate, the Document's Cover Texts may be placed
     on covers that bracket the Document within the aggregate, or the
     electronic equivalent of covers if the Document is in electronic
     form.  Otherwise they must appear on printed covers that bracket
     the whole aggregate.

  8. TRANSLATION

     Translation is considered a kind of modification, so you may
     distribute translations of the Document under the terms of section
     4.  Replacing Invariant Sections with translations requires special
     permission from their copyright holders, but you may include
     translations of some or all Invariant Sections in addition to the
     original versions of these Invariant Sections.  You may include a
     translation of this License, and all the license notices in the
     Document, and any Warranty Disclaimers, provided that you also
     include the original English version of this License and the
     original versions of those notices and disclaimers.  In case of a
     disagreement between the translation and the original version of
     this License or a notice or disclaimer, the original version will
     prevail.

     If a section in the Document is Entitled "Acknowledgements",
     "Dedications", or "History", the requirement (section 4) to
     Preserve its Title (section 1) will typically require changing the
     actual title.

  9. TERMINATION

     You may not copy, modify, sublicense, or distribute the Document
     except as expressly provided under this License.  Any attempt
     otherwise to copy, modify, sublicense, or distribute it is void,
     and will automatically terminate your rights under this License.

     However, if you cease all violation of this License, then your
     license from a particular copyright holder is reinstated (a)
     provisionally, unless and until the copyright holder explicitly and
     finally terminates your license, and (b) permanently, if the
     copyright holder fails to notify you of the violation by some
     reasonable means prior to 60 days after the cessation.

     Moreover, your license from a particular copyright holder is
     reinstated permanently if the copyright holder notifies you of the
     violation by some reasonable means, this is the first time you have
     received notice of violation of this License (for any work) from
     that copyright holder, and you cure the violation prior to 30 days
     after your receipt of the notice.

     Termination of your rights under this section does not terminate
     the licenses of parties who have received copies or rights from you
     under this License.  If your rights have been terminated and not
     permanently reinstated, receipt of a copy of some or all of the
     same material does not give you any rights to use it.

  10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of
     the GNU Free Documentation License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.  See
     <http://www.gnu.org/copyleft/>.

     Each version of the License is given a distinguishing version
     number.  If the Document specifies that a particular numbered
     version of this License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that specified version or of any later version that has been
     published (not as a draft) by the Free Software Foundation.  If the
     Document does not specify a version number of this License, you may
     choose any version ever published (not as a draft) by the Free
     Software Foundation.  If the Document specifies that a proxy can
     decide which future versions of this License can be used, that
     proxy's public statement of acceptance of a version permanently
     authorizes you to choose that version for the Document.

  11. RELICENSING

     "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
     World Wide Web server that publishes copyrightable works and also
     provides prominent facilities for anybody to edit those works.  A
     public wiki that anybody can edit is an example of such a server.
     A "Massive Multiauthor Collaboration" (or "MMC") contained in the
     site means any set of copyrightable works thus published on the MMC
     site.

     "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
     license published by Creative Commons Corporation, a not-for-profit
     corporation with a principal place of business in San Francisco,
     California, as well as future copyleft versions of that license
     published by that same organization.

     "Incorporate" means to publish or republish a Document, in whole or
     in part, as part of another Document.

     An MMC is "eligible for relicensing" if it is licensed under this
     License, and if all works that were first published under this
     License somewhere other than this MMC, and subsequently
     incorporated in whole or in part into the MMC, (1) had no cover
     texts or invariant sections, and (2) were thus incorporated prior
     to November 1, 2008.

     The operator of an MMC Site may republish an MMC contained in the
     site under CC-BY-SA on the same site at any time before August 1,
     2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents
====================================================

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

       Copyright (C)  YEAR  YOUR NAME.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts."  line with this:

         with the Invariant Sections being LIST THEIR TITLES, with
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
         being LIST.

   If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.



Tag Table:
Node: Top832
Node: Overview1982
Node: Disclaimer2829
Node: Installation3325
Node: How to Use4171
Node: JavaScript Detection7413
Node: Free Licenses Detection10821
Node: Setting Your JavaScript Free17682
Node: LibreJS Development Notes24516
Node: Installation Requirements25859
Node: LibreJS Internals27466
Node: Tests28629
Node: GNU Free Documentation License33136

End Tag Table