CGI::Application::Plugin::Session(3)

NAME
CGI::Application::Plugin::Session - Plugin that adds session support to CGI::Application

VERSION
version 1.06

SYNOPSIS
 use CGI::Application::Plugin::Session;

 my $language = $self->session->param('language');

DESCRIPTION
CGI::Application::Plugin::Session seamlessly adds session support to your CGI::Application modules by providing a CGI::Session object that is accessible from anywhere in the application.

Lazy loading is used to prevent expensive file system or database calls from being made if the session is not needed during this request. In other words, the Session object is not created until it is actually needed. Also, the Session object will act as a singleton by always returning the same Session object for the duration of the request.

This module aims to be as simple and non obtrusive as possible. By not requiring any changes to the inheritance tree of your modules, it can be easily added to existing applications. Think of it as a plugin module that adds a couple of new methods directly into the CGI::Application namespace simply by loading the module.

NAME
CGI::Application::Plugin::Session - Add CGI::Session support to CGI::Application

METHODS

  session
This method will return the current CGI::Session object. The CGI::Session object is created on the first call to this method, and any subsequent calls will return the same object. This effectively creates a singleton session object for the duration of the request. CGI::Session will look for a cookie or param containing the session ID, and create a new session if none is found. If "session_config" has not been called before the first call to "session", then it will choose some sane defaults to create the session object.

  # retrieve the session object
  my $session = $self->session;

  - or -

  # use the session object directly
  my $language = $self->session->param('language');

  session_config
This method can be used to customize the functionality of the CGI::Application::Plugin::Session module. Calling this method does not mean that a new session object will be immediately created. The session object will not be created until the first call to $self->session. This 'lazy loading' can prevent expensive file system or database calls from being made if the session is not needed during this request.

The recommended place to call "session_config" is in the "cgiapp_init" stage of CGI::Application. If this method is called after the session object has already been accessed, then it will die with an error message.

If this method is not called at all then a reasonable set of defaults will be used (the exact default values are defined below).

The following parameters are accepted:

CGI_SESSION_OPTIONS
    This allows you to customize how the CGI::Session object is created by providing a list of options that will be passed to the CGI::Session constructor. Please see the documentation for CGI::Session for the exact syntax of the parameters.

DEFAULT_EXPIRY
    CGI::Session Allows you to set an expiry time for the session. You can set the DEFAULT_EXPIRY option to have a default expiry time set for all newly created sessions. It takes the same format as the $session->expiry method of CGI::Session takes. Note that it is only set for new session, not when a session is reloaded from the store.

COOKIE_PARAMS
    This allows you to customize the options that are used when creating the session cookie. For example you could provide an expiry time for the cookie by passing -expiry => '+24h'. The -name and -value parameters for the cookie will be added automatically unless you specifically override them by providing -name and/or -value parameters. See the CGI::Cookie docs for the exact syntax of the parameters.

    NOTE: You can do the following to get both the cookie name and the internal name of the CGI::Session object to be changed:

      $self->session_config(
        CGI_SESSION_OPTIONS => [
          $driver,
          $self->query,
          \%driver_options,
          { name => 'new_cookie_name' } # change cookie and session name
        ]
      );

    Also, if '-name' parameter and 'name' of session don't match a warning will be emitted.

SEND_COOKIE
    If set to a true value, the module will automatically add a cookie header to the outgoing headers if a new session is created (Since the session module is lazy loaded, this will only happen if you make a call to $self->session at some point to create the session object). This option defaults to true. If it is set to false, then no session cookies will be sent, which may be useful if you prefer URL based sessions (it is up to you to pass the session ID in this case).

The following example shows what options are set by default (ie this is what you would get if you do not call session_config).

 $self->session_config(
          CGI_SESSION_OPTIONS => [ "driver:File", $self->query, {Directory=>'/tmp'} ],
          COOKIE_PARAMS       => {
                                   -path  => '/',
                                 },
          SEND_COOKIE         => 1,
 );

Here is a more customized example that uses the PostgreSQL driver and sets an expiry and domain on the cookie.

 $self->session_config(
          CGI_SESSION_OPTIONS => [ "driver:PostgreSQL;serializer:Storable", $self->query, {Handle=>$dbh} ],
          COOKIE_PARAMS       => {
                                   -domain  => 'mydomain.com',
                                   -expires => '+24h',
                                   -path    => '/',
                                   -secure  => 1,
                                 },
 );

  session_cookie
This method will add a cookie to the outgoing headers containing the session ID that was assigned by the CGI::Session module.

This method is called automatically the first time $self->session is accessed if SEND_COOKIE was set true, which is the default, so it will most likely never need to be called manually.

NOTE that if you do choose to call it manually that a session object will automatically be created if it doesn't already exist. This removes the lazy loading benefits of the plugin where a session is only created/loaded when it is required.

It could be useful if you want to force the cookie header to be sent out even if the session is not used on this request, or if you want to manage the headers yourself by turning SEND_COOKIE to false.

  # Force the cookie header to be sent including some
  # custom cookie parameters
  $self->session_cookie(-secure => 1, -expires => '+1w');

  session_loaded
This method will let you know if the session object has been loaded yet. In other words, it lets you know if $self->session has been called.

  sub cgiapp_postrun {
    my $self = shift;
    $self->session->flush if $self->session_loaded;;
  }

  session_recreate
This method will delete the existing session, and create a brand new one for you with a new session ID. It copies over all existing parameters into the new session.

This can be useful to protect against some login attacks when storing authentication tokens in the session. Very briefly, an attacker loads a page on your site and creates a session, then tries to trick a victim into loading this page with the same session ID (possibly by embedding it in a URL). Then if the victim follows the link and subsequently logs into their account, the attacker will have a valid session ID where the session is now logged in, and hence the attacker has access to the victims account.

  sub mylogin {
    my $self = shift;
    if ($newly_authenticated) {
        $self->session_recreate;
    }
  }

  session_delete
This method will perform a more comprehensive clean-up of the session, calling both the CGI::Session delete() method, but also deleting the cookie from the client, if you are using cookies.

  sub logout {
    my $self = shift;
    $self->session_delete;
    # what now?  redirect user back to the homepage?
  }

EXAMPLE
In a CGI::Application module:

  # configure the session once during the init stage
  sub cgiapp_init {
    my $self = shift;

    # Configure the session
    $self->session_config(
       CGI_SESSION_OPTIONS => [ "driver:PostgreSQL;serializer:Storable", $self->query, {Handle=>$self->dbh} ],
       DEFAULT_EXPIRY      => '+1w',
       COOKIE_PARAMS       => {
                                -expires => '+24h',
                                -path    => '/',
                              },
       SEND_COOKIE         => 1,
    );

  }

  sub cgiapp_prerun {
    my $self = shift;

    # Redirect to login, if necessary
    unless ( $self->session->param('~logged-in') ) {
      $self->prerun_mode('login');
    }
  }

  sub my_runmode {
    my $self = shift;

    # Load the template
    my $template = $self->load_tmpl('my_runmode.tmpl');

    # Add all the session parameters to the template
    $template->param($self->session->param_hashref());

    # return the template output
    return $template->output;
  }

TODO

•   I am considering adding support for other session modules in the future, like Apache::Session and possibly others if there is a demand.

•   Possibly add some tests to make sure cookies are accepted by the client.

•   Allow a callback to be executed right after a session has been created

SEE ALSO
CGI::Application, CGI::Session, perl(1)

AUTHOR
Cees Hek <ceeshek@gmail.com>

LICENSE
Copyright (C) 2004, 2005 Cees Hek <ceeshek@gmail.com>

This library is free software. You can modify and or distribute it under the same terms as Perl itself.

AUTHOR
Cees Hek <ceeshek@gmail.com>

COPYRIGHT AND LICENSE
This software is copyright (c) 2024 by Cees Hek.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.