Best practice with polymorphic constructors

[Ovid]

I have a class, we'll call it Foo::Database, which is a base class for three other classes:

• Foo::Security
• Foo::Database::Select
• Foo::Database::Modify

The Foo::Database class, amongst other things, connects to the database and controls all direct use of the DBI module. However, each of the child classes connects to the database as a different user. This is done for security reasons. I see no reason to give a Foo::Database::Select object the ability to modify the database if it doesn't need to. I view this as "defense in depth". If there's a security hole in another portion of code, hopefully the security built into the objects is a nice fallback.

Since I connect to the database in the constructor, the obvious idea is to make the constructor polymorphic by adding a unique constructor to each class. However, only the username and password for these constructors is unique and I didn't see the need to have repetitious code. This is what I used in the base class (well, there's more, but this is stripped down):

{
    my $config_file = '/Inetpub/Secure/foo.dat';
    my $data        = do ( $config_file ) or die "Cannot process $conf
+ig_file: $!";

    sub new {
        my $class  = shift;
        my ( $module ) = ( $class =~ /.*::(.*)$/ );
        my $objref = { _dbh => _connect( data_source => $data->{ data_
+source },
                                         user        => $data->{ $modu
+le }{ user },
                                         pass        => $data->{ $modu
+le }{ pass } ),
                       _error => 0 };
        bless $objref, $class;
    }
}

Note that all sensitive data is in a file (currently just a simple data structure) that's not Web-accessible. The problem that I don't like is that the config file now must have the module names hard-coded into it. As I wrote in a node about orthogonal code and security, I'm not wild about having to build something that requires different parts of a system to be synchronized. Any suggestions for improvement?

Cheers,
Ovid

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