NAME¶

SYNOPSIS¶

    # To get sessions to "just work", all you need to do is use these plugins:
    use Catalyst qw/
      Session
      Session::Store::FastMmap
      Session::State::Cookie
      /;
    # you can replace Store::FastMmap with Store::File - both have sensible
    # default configurations (see their docs for details)
    # more complicated backends are available for other scenarios (DBI storage,
    # etc)
    # after you've loaded the plugins you can save session data
    # For example, if you are writing a shopping cart, it could be implemented
    # like this:
    sub add_item : Local {
        my ( $self, $c ) = @_;
        my $item_id = $c->req->param("item");
        # $c->session is a hash ref, a bit like $c->stash
        # the difference is that it' preserved across requests
        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¶

RECOMENDED BACKENDS¶

Session::State::Cookie

The only really sane way to do state is using cookies.

Session::Store::File

A portable backend, based on Cache::File.

Session::Store::FastMmap

A fast and flexible backend, based on Cache::FastMmap.

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.

 

You can also set session keys by passing a list of key/value pairs or a hashref.

 

    $c->session->{foo} = "bar";      # This works.
    $c->session(one => 1, two => 2); # And this.
    $c->session({ answer => 42 });   # And this.
    

session_expires

This method returns the time when the current session will expire, or 0 if there is no current session. If there is a session and it already expired, it will delete the session and return 0 as well.

flash

This is like Ruby on Rails' flash data structure. Think of it as a stash that lasts for longer than one request, letting you redirect instead of forward.

 

The flash data will be cleaned up only on requests on which actually use $c->flash (thus allowing multiple redirections), and the policy is to delete all the keys which haven't changed since the flash data was loaded at the end of every request.

 

Note that use of the flash is an easy way to get data across requests, but it's also strongly disrecommended, due it it being inherently plagued with race conditions. This means that it's unlikely to work well if your users have multiple tabs open at once, or if your site does a lot of AJAX requests.

 

Catalyst::Plugin::StatusMessage is the recommended alternative solution, as this doesn't suffer from these issues.

 

    sub moose : Local {
        my ( $self, $c ) = @_;
        $c->flash->{beans} = 10;
        $c->response->redirect( $c->uri_for("foo") );
    }
    sub foo : Local {
        my ( $self, $c ) = @_;
        my $value = $c->flash->{beans};
        # ...
        $c->response->redirect( $c->uri_for("bar") );
    }
    sub bar : Local {
        my ( $self, $c ) = @_;
        if ( exists $c->flash->{beans} ) { # false
        }
    }
    

clear_flash

Zap all the keys in the flash regardless of their current state.

keep_flash @keys

If you want to keep a flash key for the next request too, even if it hasn't changed, call "keep_flash" and pass in the keys as arguments.

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.

 

NOTE: This method will also delete your flash data.

session_delete_reason

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

session_expire_key $key, $ttl

Mark a key to expire at a certain time (only useful when shorter than the expiry time for the whole session).

 

For example:

 

    __PACKAGE__->config('Plugin::Session' => { expires => 10000000000 }); # "forever"
    (NB If this number is too large, Y2K38 breakage could result.)
    # later
    $c->session_expire_key( __user => 3600 );
    

 

Will make the session data survive, but the user will still be logged out after an hour.

 

Note that these values are not auto extended.

change_session_id

By calling this method you can force a session id change while keeping all session data. This method might come handy when you are paranoid about some advanced variations of session fixation attack.

 

If you want to prevent this session fixation scenario:

 

    0) let us have WebApp with anonymous and authenticated parts
    1) a hacker goes to vulnerable WebApp and gets a real sessionid,
       just by browsing anonymous part of WebApp
    2) the hacker inserts (somehow) this values into a cookie in victim's browser
    3) after the victim logs into WebApp the hacker can enter his/her session
    

 

you should call change_session_id in your login controller like this:

 

      if ($c->authenticate( { username => $user, password => $pass } )) {
        # login OK
        $c->change_session_id;
        ...
      } else {
        # login FAILED
        ...
      }
    

change_session_expires $expires

You can change the session expiration time for this session;

 

    $c->change_session_expires( 4000 );
    

 

Note that this only works to set the session longer than the config setting.

INTERNAL METHODS¶

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('Plugin::Session')" with the default values listed in "CONFIGURATION".

prepare_action

This method is extended.

 

Its only effect is if the (off by default) "flash_to_stash" configuration parameter is on - then it will copy the contents of the flash to the stash at prepare time.

finalize_headers

This method is extended and will extend the expiry time before sending the response.

finalize_body

This method is extended and will call finalize_session before the other finalize_body methods run. Here we persist the session data if a session exists.

initialize_session_data

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

create_session_id

Creates a new session ID using "generate_session_id" if there is no session ID yet.

validate_session_id SID

Make sure a session ID is of the right format.

 

This currently ensures that the session ID string is any amount of case insensitive hexadecimal characters.

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 availability 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:

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

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

finalize_session

Clean up the session during "finalize".

 

This clears the various accessors after saving to the store.

dump_these

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

calculate_extended_session_expires

calculate_initial_session_expires

create_session_id_if_needed

delete_session_id

extend_session_expires

Note: this is *not* used to give an individual user a longer session. See 'change_session_expires'.

extend_session_id

get_session_id

reset_session_expires

session_is_valid

set_session_id

initial_session_expires

USING SESSIONS DURING PREPARE¶

    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('Plugin::Session' => {
        expires => 1234,
    });

expires

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

verify_address

When true, "<$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.

 

Defaults to false.

verify_user_agent

When true, "<$c-"request->user_agent>> will be checked at prepare time. If it is not the same as the user agent that initiated the session, the session is deleted.

 

Defaults to false.

flash_to_stash

This option makes it easier to have actions behave the same whether they were forwarded to or redirected to. On prepare time it copies the contents of "flash" (if any) to the stash.

SPECIAL KEYS¶

__expires

This key no longer exists. Use "session_expires" instead.

__updated

The last time a session was saved to the store.

__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 if "verify_address" is true in the configuration.

__user_agent

The value of "$c->request->user_agent" at the time the session was created. This value is only populated if "verify_user_agent" is true in the configuration.

CAVEATS¶

Round the Robin Proxies¶

Race Conditions¶

1.

request a starts, request b starts, with the same session ID

2.

session data is loaded in request a

3.

session data is loaded in request b

4.

session data is changed in request a

5.

request a finishes, session data is updated and written to store

6.

request b finishes, session data is updated and written to store, overwriting changes by request a

AUTHORS¶

Contributors¶

COPYRIGHT & LICENSE¶

    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.