Simple authorization with FastCGI

FastCGI is a high-performance API supported by the Zeus Web Server. It is an open standard, and is language and platform independent. FastCGI provides both authorization and content generation services, and has a simple, quick development cycle. FastCGI is recommended as a general purpose solution for almost any task.

Here is a simple example of using FastCGI to perform authorization. It is written in Perl, using the Perl FastCGI library described in the Hello World example.

#!/usr/bin/perl

use FCGI;

while (FCGI::accept >= 0)
{
    if( $ENV{'REMOTE_USER'  } eq "foo" &&
        $ENV{'REMOTE_PASSWD'} eq "bar"  )
    {
        print( "Status: 200\n\n" );
    }
    else
    {
        print( "Status: 401\n\n" );
        print( "WWW-Authenticate: basic realm=\"foo\"\n\n" );
    }
}

A FastCGI authorizer simply retrieves the information about the request using FCGI::accept() , and then returns a response of either 'Status: 200' if the request should be allowed, or 'Status: 401' if the username or password is invalid.

In this case, any requests passed to the authorizer will be allowed only is the user supplied a username of 'foo' and a password of 'bar'. Otherwise the authorizer will disallow the request and prompt the user to enter a new password.
Running this example

In order to run this code, you'll need to enable FastCGI authorizer support in the Zeus Web Server and have installed a copy of Perl and the FCGI perl module.
Authenticating against a database

As a more advanced example, imagine wanting to authenticate the customers request from a backend SQL customer data which holds all the information about your customers. This is such a common task we explain how to do this in detail.

For this example, we are going to use the popular MySQL, and a simple database schema to hold our customer information. The database is running on a machine called 'db', and is a schema that comprises of a single table called 'users' which looks like:

Thus to retrieve a password for a given user, we would issue the following SQL statement:

/* the question mark is a marker for a `bound parameter'*/
select password from users where username = ?;

Altering our FastCGI application to connect to this database and check the user supplied password against it is very easy, here's a mysql version.

Note, one of the key advantages of FastCGI is its ability to have persistent database-connections. Establishing a new connection to a database is generally a very time-consuming and CPU-intensive task, so persistent database connections provide a huge performance increase. When doing database queries in FastCGI one can spawn multiple instances of the authorizer process to allow multiple database queries to be running in parallel
Authenticating against a LDAP server

Instead of using a general purpose database, many large ISPs and corporations are now choosing to keep their customer data in a global LDAP database, commonly known as a white pages server. Again, altering the FastCGI example to query the LDAP server is an easy task.

For this example, OpenLDAP slapd server (http://www.openldap.org/) with the following configuration:

Our 'minimal' slapd.conf file contained:

schemacheck     off
database        ldbm
suffix          "o=Zeus Technology, c=UK"
directory       /tmp
defaultaccess   read
rootdn          "cn=root, o=Zeus Technology, c=UK"
rootpw          secret

All access was disabled to the LDAP server unless the client provided the rootdn/rootpw. Different access control rules between the web server and your LDAP server will probably apply to your setup.

The database we used, in `ldif' format was:

dn: o=Zeus Technology, c=UK
o: Zeus Technology

dn: cn=fred_bloggs, ou=People, o=Zeus Technology, c=UK
cn: fred_bloggs
password: secret

dn: cn=john_doe, ou=People, o=Zeus Technology, c=UK
cn: john_doe
userid: john.doe
password: notverysecret

This defined two users, each with a password. In this example we have stored the plaintext passwords in the LDAP server for simplicity, but a hash of the passwords could easily be stored instead.

The FastCGI application will need to be able to retrieve the password for a given user name. Queries are encoded in the standard LDAP URL format (see http://search.ietf.org/rfc/rfc2255.txt for a full specification).

Using our example database schema above, and the knowledge that our test LDAP server was setup on a machine named `olympus', the LDAP query URL we need is:

ldap://olympus/o=Zeus Technology, c=UK?password?sub?userid=$u

Content Manager [Administrator] 16 December 2005