NAME

Catalyst::Plugin::Session - Generic Session plugin - ties together server side storage and client side tickets required to maintain session data.

SYNOPSIS

use Catalyst qw/Session Session::Store::FastMmap Session::State::Cookie/;

sub add_item : Local {
    my ( $self, $c ) = @_;

    my $item_id = $c->req->param("item");

    # $c->session is stored across requests, so
    # other actions will see these values

    push @{ $c->session->{items} }, $item_id;

    $c->forward("MyView");
}

sub display_items : Local {
    my ( $self, $c ) = @_;

    # values in $c->session are restored
    $c->stash->{items_to_display} =
        [ map { MyModel->retrieve($_) } @{ $c->session->{items} } ];

    $c->forward("MyView");
}

DESCRIPTION

The Session plugin is the base of two related parts of functionality required for session management in web applications.

The first part, the State, is getting the browser to repeat back a session key, so that the web application can identify the client and logically string several requests together into a session.

The second part, the Store, deals with the actual storage of information about the client. This data is stored so that the it may be revived for every request made by the same client.

This plugin links the two pieces together.

METHODS

sessionid

An accessor for the session ID value.

session

Returns a hash reference that might contain unserialized values from previous requests in the same session, and whose modified value will be saved for future requests.

This method will automatically create a new session and session ID if none exists.

session_delete_reason

This accessor contains a string with the reason a session was deleted. Possible values include:

• address mismatch

• session expired

setup

This method is extended to also make calls to check_session_plugin_requirements and setup_session.

check_session_plugin_requirements

This method ensures that a State and a Store plugin are also in use by the application.

setup_session

This method populates $c->config->{session} with the default values listed in "CONFIGURATION".

prepare_action

This methoid is extended, and will restore session data and check it for validity if a session id is defined. It assumes that the State plugin will populate the sessionid key beforehand.

finalize

This method is extended and will extend the expiry time, as well as persist the session data if a session exists.

delete_session REASON

This method is used to invalidate a session. It takes an optional parameter which will be saved in session_delete_reason if provided.

initialize_session_data

This method will initialize the internal structure of the session, and is called by the session method if appropriate.

generate_session_id

This method will return a string that can be used as a session ID. It is supposed to be a reasonably random string with enough bits to prevent collision. It basically takes session_hash_seed and hashes it using SHA-1, MD5 or SHA-256, depending on the availibility of these modules.

session_hash_seed

This method is actually rather internal to generate_session_id, but should be overridable in case you want to provide more random data.

Currently it returns a concatenated string which contains:

• A counter

• The current time

• One value from rand.

• The stringified value of a newly allocated hash reference

• The stringified value of the Catalyst context object

In the hopes that those combined values are entropic enough for most uses. If this is not the case you can replace session_hash_seed with e.g.

sub session_hash_seed {
    open my $fh, "<", "/dev/random";
    read $fh, my $bytes, 20;
    close $fh;
    return $bytes;
}

Or even more directly, replace generate_session_id:

sub generate_session_id {
    open my $fh, "<", "/dev/random";
    read $fh, my $bytes, 20;
    close $fh;
    return unpack("H*", $bytes);
}

Also have a look at Crypt::Random and the various openssl bindings - these modules provide APIs for cryptographically secure random data.

dump_these

See "dump_these" in Catalyst - ammends the session data structure to the list of dumped objects if session ID is defined.

USING SESSIONS DURING PREPARE

The earliest point in time at which you may use the session data is after Catalyst::Plugin::Session's prepare_action has finished.

State plugins must set $c->session ID before prepare_action, and during prepare_action Catalyst::Plugin::Session will actually load the data from the store.

sub prepare_action {
	my $c = shift;

	# don't touch $c->session yet!
	
	$c->NEXT::prepare_action( @_ );

	$c->session;  # this is OK
	$c->sessionid; # this is also OK
}

CONFIGURATION

$c->config->{session} = {
    expires => 1234,
};

All configuation parameters are provided in a hash reference under the session key in the configuration hash.

expires

The time-to-live of each session, expressed in seconds. Defaults to 7200 (two hours).

verify_address

When false, $c->request->address will be checked at prepare time. If it is not the same as the address that initiated the session, the session is deleted.

SPECIAL KEYS

The hash reference returned by $c->session contains several keys which are automatically set:

__expires

A timestamp whose value is the last second when the session is still valid. If a session is restored, and __expires is less than the current time, the session is deleted.

__updated

The last time a session was saved. This is the value of $c->{session}{__expires} - $c->config->{session}{expires}.

__created

The time when the session was first created.

__address

The value of $c->request->address at the time the session was created. This value is only populated of verify_address is true in the configuration.

CAVEATS

verify_address could make your site inaccessible to users who are behind load balanced proxies. Some ISPs may give a different IP to each request by the same client due to this type of proxying. If addresses are verified these users' sessions cannot persist.

To let these users access your site you can either disable address verification as a whole, or provide a checkbox in the login dialog that tells the server that it's OK for the address of the client to change. When the server sees that this box is checked it should delete the __address sepcial key from the session hash when the hash is first created.

AUTHORS

Andy Grundman Christian Hansen Yuval Kogman, nothingmuch@woobling.org Sebastian Riedel

COPYRIGHT & LICNESE

Copyright (c) 2005 the aforementioned authors. All rights
reserved. This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.