Warning
-------

Use at your own risk -- cgi-bin is powerful and thus has many serious
security implications.


Installation
------------

This example was designed for an Ubuntu installation of apache2 (see
discussion of Arch , below); maybe you can just run

  sudo make install
  sudo apache2ctl restart
  
and it will work.  You should probably check the paths at the top of
Makefile and test.apache to confirm that they correspond to your
system's web root.

Then browse to http://localhost/ajex/test.php to see what has been
installed.


Debugging
---------

You should see a dumb web form at http://localhost/ajex/test.php.  If you
don't, then the files are not getting installed into the right place
for your web server.

When the cgi-bin is working, you'll see a line with the date, and it
will update whenever you click a Submit button.  If you see the form,
but it doesn't "work", then the cgi-bin part of the web-server isn't
working.  Browse to http://localhost/ajex/cgi-bin/test.py.  If you see
the text of the python script, that's bad -- this is that security
issue we warned (or will warn) you about.  When cgi-bin is working,
your browser should print some JSON data, like:

  {"date": "Wed Feb 22 09:30:39 2017", "also": "Button=None",
   "message": "telescopes are 95"}


Security
--------

There are many dangers associated with cgi-bin.  I think the two
things that you should be really careful about, going forward, are:

- Assume that the code you have in the cgi-bin directory will, at some
  point, be readable by the public.  This means that you can't store
  database passwords (and so on) in the scripts that live in your
  cgi-bin directory.  Instead, have your cgi-bin executable, when it
  is run, call or import or load those secrets from some other part of
  the file-system that is not in the web server's DocumentRoot.

- Always "sanitize" input data before "doing" anything with it.  The
  degree of sanitization required depends on what you're doing with
  it.  This includes "escaping" strings that you're passing into
  database queries, or sanity checking inputs that you will be passing
  to other executables.


Arch Linux
----------

The default DocumentRoot for apache on Arch is /srv/http instead of
/var/www.  And "virtual hosts" are often sorted in
/etc/httpd/conf/vhosts.  So change the Makefile paths to say:

  WEB_INSTALL=/srv/http/ajex
  CGI_INSTALL=/srv/http/ajex/cgi-bin
  CFG_INSTALL=/etc/httpd/conf/vhosts/ajex.conf

Before you make install, edit test.apache (which will become
ajex.conf) so it's talking about the right directories:

  sed -i 's/var\/www/srv\/http/g' test.apache

In the apache configuration, cgi scripts aren't enabled by default.
To enable cgi-bin (note this is dangerous, you have been warned,
etc.), edit /etc/httpd/conf/httpd.conf:

  #LoadModule cgid_module modules/mod_cgid.so
  #LoadModule cgi_module modules/mod_cgi.so

and uncomment them.  You can also tell httpd to include your virtual
host.  Somewhere near the end add:

  Include conf/vhosts/ajex.conf

Because python3 is the default on Arch, you will probably have to
change the top line of test.py to invoke python2, i.e.

  #!/usr/bin/env python2