Sunbelt Computer Software

Welcome to Microblog

(c) 2003-2007 Peter A. Dinda, pdinda@cs.northwestern.edu

This is a tiny web log implementation based on Perl CGI, DBI, and an
Oracle database.  It is instructional code to support CS 339,
Introduction to Databases in the CS Department at Northwestern
University.

Requirements
------------

You must have the following software running:

   Perl 5.8  (expected to be installed in /usr/local/bin)
     CGI
     DBI
     DBI::Oracle
     Time::ParseDate
   Oracle    (tested with Oracle 9i Enterprise 9.2)
   Apache    (or other web server)

We assume the following:
   
   machine     Name of your machine
   you         Linux username
   yourgroup   Your Linux group
   youora      Your Oracle username
   orapasswd   Your Oracle password

Your oracle account must have permissions to allow the creation of
tables and sequences, inserts, deletes, updates, and selects.  Here 
is a minimal set of sysdba commands to do this if it isn't already the
case:

$ sqlplus /nolog
SQL> connect / as sysdba;
SQL> create user youora identified by orapasswd default tablespace users;
SQL> grant connect, resource to youora;
SQL> quit;

We assume that ~you/public_html is served by Apache as 
http://machine/~you.  We also assume that ~you/public_html and
its children are CGI-enabled and support CGI scripts with the 
extension ".pl".  

Your web browser must support frames and accept cookies.


Contents
--------

   README
   blog.sql        SQL code for creating the blog schema
   drop_blog.sql   SQL code for deleting the blog schema
   blog.pl         Perl CGI code that implements the blog
                   It produces output for the right frame
   blog-handout.pl Copy of blog.pl ("what we handed out")
   blog.html       HTML code that creates the frames
   actions.html    HTML code for the left frame
   blog.css        CSS style file for rendering pages


Installing Microblog
--------------------

cd public_html
tar xvfz microblog.tgz
cd microblog
sqlplus youora/orapasswd @blog.sql

Now edit blog.pl to reflect your environment.  

These lines reflect where oracle is installed:

$ENV{ORACLE_HOME}="/opt/oracle/product/9.2.0";
$ENV{ORACLE_BASE}="/opt/oracle/product/9.2.0";
$ENV{ORACLE_SID}="URGIS";

These lines reflect your oracle user and password:

my $dbuser="cs339";
my $dbpasswd="cs339";


Using Microblog
---------------

Point a web browser at

http://machine/~you/microblog/blog.html

You should see two side-by-side frames.  The left frame
shows the high level actions that are possible
(read/write/users/login).  The right frame should be showing a login
screen.  Two users are available by default:  root (with password
rootroot), who can do anything, and none (with password nonenone), who
can do nothing.

Understanding Microblog
-----------------------

No matter what the assignment is, you first want to understand how
Microblog works.  Both blog.sql and blog.pl are extensively commented
to help you do that.  They also generate tons of debugging output to
the browser by default.  This is controlled by the following lines in
the blog.pl script:

my $show_params=1;
my $show_cookies=1;
my $show_sqlinput=1;
my $show_sqloutput=1;

When you load http://machine/~you/microblog/blog.html, you get an HTML
frameset that consists of two frames.  The left frame loads
actions.html, while the right frame load blog.pl with "query" as the
requested action.  blog.pl expects to get a cookie containing the
username and password.  If that cookie doesn't exist, then it asks you
to log in and gives you an appropriate cookie.  A cookie is just a way
in which a script or other can store some state in your browser.  The
script then gives (or doesn't give) you access to different actions
based on your cookie.  

NOTE: Passing a cookie with an unencrypted username/password
combination is NOT a secure way of handling sessions.  First, it is
sent in cleartext and so could be intercepted.  Second, it is stored
in the browser or the browser cookie file in cleartext and so could be
vulnerable to attack there.  


Extending Microblog
-------------------

The first project in CS 339 involves extending Microblog in various
ways.  The best way to do this is generally the following:

0. UNDERSTAND HOW IT WORKS FIRST
1. Write the SQL needed for the task
2. Verify that instances of the SQL work using sqlplus
3. Embed the SQL into a Perl function (look at UserAdd for an example)
4. Finally, write the Perl logic to call the function at the
   right time.