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.\" ========================================================================
.\"
.IX Title "Catalyst::Plugin::Session 3pm"
.TH Catalyst::Plugin::Session 3pm "2018-12-22" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Catalyst::Plugin::Session \- Generic Session plugin \- ties together server side storage and client side state required to maintain session data.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    # 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\*(Aqve 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\*(Aq 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");
\&    }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The Session plugin is the base of two related parts of functionality required
for session management in web applications.
.PP
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.
.PP
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.
.PP
This plugin links the two pieces together.
.SH "RECOMENDED BACKENDS"
.IX Header "RECOMENDED BACKENDS"
.IP "Session::State::Cookie" 4
.IX Item "Session::State::Cookie"
The only really sane way to do state is using cookies.
.IP "Session::Store::File" 4
.IX Item "Session::Store::File"
A portable backend, based on Cache::File.
.IP "Session::Store::FastMmap" 4
.IX Item "Session::Store::FastMmap"
A fast and flexible backend, based on Cache::FastMmap.
.SH "METHODS"
.IX Header "METHODS"
.IP "sessionid" 4
.IX Item "sessionid"
An accessor for the session \s-1ID\s0 value.
.IP "session" 4
.IX Item "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.
.Sp
This method will automatically create a new session and session \s-1ID\s0 if none
exists.
.Sp
You can also set session keys by passing a list of key/value pairs or a
hashref.
.Sp
.Vb 3
\&    $c\->session\->{foo} = "bar";      # This works.
\&    $c\->session(one => 1, two => 2); # And this.
\&    $c\->session({ answer => 42 });   # And this.
.Ve
.IP "session_expires" 4
.IX Item "session_expires"
This method returns the time when the current session will expire, or 0 if
there is no current session. If there is a session and it already expired, it
will delete the session and return 0 as well.
.IP "flash" 4
.IX Item "flash"
This is like Ruby on Rails' flash data structure. Think of it as a stash that
lasts for longer than one request, letting you redirect instead of forward.
.Sp
The flash data will be cleaned up only on requests on which actually use
\&\f(CW$c\fR\->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.
.Sp
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 \s-1AJAX\s0
requests.
.Sp
Catalyst::Plugin::StatusMessage is the recommended alternative solution,
as this doesn't suffer from these issues.
.Sp
.Vb 2
\&    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
\&
\&        }
\&    }
.Ve
.IP "clear_flash" 4
.IX Item "clear_flash"
Zap all the keys in the flash regardless of their current state.
.ie n .IP "keep_flash @keys" 4
.el .IP "keep_flash \f(CW@keys\fR" 4
.IX Item "keep_flash @keys"
If you want to keep a flash key for the next request too, even if it hasn't
changed, call \f(CW\*(C`keep_flash\*(C'\fR and pass in the keys as arguments.
.IP "delete_session \s-1REASON\s0" 4
.IX Item "delete_session REASON"
This method is used to invalidate a session. It takes an optional parameter
which will be saved in \f(CW\*(C`session_delete_reason\*(C'\fR if provided.
.Sp
\&\s-1NOTE:\s0 This method will \fBalso\fR delete your flash data.
.IP "session_delete_reason" 4
.IX Item "session_delete_reason"
This accessor contains a string with the reason a session was deleted. Possible
values include:
.RS 4
.IP "\(bu" 4
\&\f(CW\*(C`address mismatch\*(C'\fR
.IP "\(bu" 4
\&\f(CW\*(C`session expired\*(C'\fR
.RE
.RS 4
.RE
.ie n .IP "session_expire_key $key, $ttl" 4
.el .IP "session_expire_key \f(CW$key\fR, \f(CW$ttl\fR" 4
.IX Item "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).
.Sp
For example:
.Sp
.Vb 2
\&    _\|_PACKAGE_\|_\->config(\*(AqPlugin::Session\*(Aq => { expires => 10000000000 }); # "forever"
\&    (NB If this number is too large, Y2K38 breakage could result.)
\&
\&    # later
\&
\&    $c\->session_expire_key( _\|_user => 3600 );
.Ve
.Sp
Will make the session data survive, but the user will still be logged out after
an hour.
.Sp
Note that these values are not auto extended.
.IP "change_session_id" 4
.IX Item "change_session_id"
By calling this method you can force a session id change while keeping all
session data. This method might come handy when you are paranoid about some
advanced variations of session fixation attack.
.Sp
If you want to prevent this session fixation scenario:
.Sp
.Vb 5
\&    0) let us have WebApp with anonymous and authenticated parts
\&    1) a hacker goes to vulnerable WebApp and gets a real sessionid,
\&       just by browsing anonymous part of WebApp
\&    2) the hacker inserts (somehow) this values into a cookie in victim\*(Aqs browser
\&    3) after the victim logs into WebApp the hacker can enter his/her session
.Ve
.Sp
you should call change_session_id in your login controller like this:
.Sp
.Vb 8
\&      if ($c\->authenticate( { username => $user, password => $pass } )) {
\&        # login OK
\&        $c\->change_session_id;
\&        ...
\&      } else {
\&        # login FAILED
\&        ...
\&      }
.Ve
.ie n .IP "change_session_expires $expires" 4
.el .IP "change_session_expires \f(CW$expires\fR" 4
.IX Item "change_session_expires $expires"
You can change the session expiration time for this session;
.Sp
.Vb 1
\&    $c\->change_session_expires( 4000 );
.Ve
.Sp
Note that this only works to set the session longer than the config setting.
.SH "INTERNAL METHODS"
.IX Header "INTERNAL METHODS"
.IP "setup" 4
.IX Item "setup"
This method is extended to also make calls to
\&\f(CW\*(C`check_session_plugin_requirements\*(C'\fR and \f(CW\*(C`setup_session\*(C'\fR.
.IP "check_session_plugin_requirements" 4
.IX Item "check_session_plugin_requirements"
This method ensures that a State and a Store plugin are also in use by the
application.
.IP "setup_session" 4
.IX Item "setup_session"
This method populates \f(CW\*(C`$c\->config(\*(AqPlugin::Session\*(Aq)\*(C'\fR with the default values
listed in \*(L"\s-1CONFIGURATION\*(R"\s0.
.IP "prepare_action" 4
.IX Item "prepare_action"
This method is extended.
.Sp
Its only effect is if the (off by default) \f(CW\*(C`flash_to_stash\*(C'\fR configuration
parameter is on \- then it will copy the contents of the flash to the stash at
prepare time.
.IP "finalize_headers" 4
.IX Item "finalize_headers"
This method is extended and will extend the expiry time before sending
the response.
.IP "finalize_body" 4
.IX Item "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.
.IP "initialize_session_data" 4
.IX Item "initialize_session_data"
This method will initialize the internal structure of the session, and is
called by the \f(CW\*(C`session\*(C'\fR method if appropriate.
.IP "create_session_id" 4
.IX Item "create_session_id"
Creates a new session \s-1ID\s0 using \f(CW\*(C`generate_session_id\*(C'\fR if there is no session \s-1ID\s0
yet.
.IP "validate_session_id \s-1SID\s0" 4
.IX Item "validate_session_id SID"
Make sure a session \s-1ID\s0 is of the right format.
.Sp
This currently ensures that the session \s-1ID\s0 string is any amount of case
insensitive hexadecimal characters.
.IP "generate_session_id" 4
.IX Item "generate_session_id"
This method will return a string that can be used as a session \s-1ID.\s0 It is
supposed to be a reasonably random string with enough bits to prevent
collision. It basically takes \f(CW\*(C`session_hash_seed\*(C'\fR and hashes it using \s-1SHA\-1,
MD5\s0 or \s-1SHA\-256,\s0 depending on the availability of these modules.
.IP "session_hash_seed" 4
.IX Item "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.
.Sp
Currently it returns a concatenated string which contains:
.RS 4
.IP "\(bu" 4
A counter
.IP "\(bu" 4
The current time
.IP "\(bu" 4
One value from \f(CW\*(C`rand\*(C'\fR.
.IP "\(bu" 4
The stringified value of a newly allocated hash reference
.IP "\(bu" 4
The stringified value of the Catalyst context object
.RE
.RS 4
.Sp
in the hopes that those combined values are entropic enough for most uses. If
this is not the case you can replace \f(CW\*(C`session_hash_seed\*(C'\fR with e.g.
.Sp
.Vb 6
\&    sub session_hash_seed {
\&        open my $fh, "<", "/dev/random";
\&        read $fh, my $bytes, 20;
\&        close $fh;
\&        return $bytes;
\&    }
.Ve
.Sp
Or even more directly, replace \f(CW\*(C`generate_session_id\*(C'\fR:
.Sp
.Vb 6
\&    sub generate_session_id {
\&        open my $fh, "<", "/dev/random";
\&        read $fh, my $bytes, 20;
\&        close $fh;
\&        return unpack("H*", $bytes);
\&    }
.Ve
.Sp
Also have a look at Crypt::Random and the various openssl bindings \- these
modules provide APIs for cryptographically secure random data.
.RE
.IP "finalize_session" 4
.IX Item "finalize_session"
Clean up the session during \f(CW\*(C`finalize\*(C'\fR.
.Sp
This clears the various accessors after saving to the store.
.IP "dump_these" 4
.IX Item "dump_these"
See \*(L"dump_these\*(R" in Catalyst \- ammends the session data structure to the list of
dumped objects if session \s-1ID\s0 is defined.
.IP "calculate_extended_session_expires" 4
.IX Item "calculate_extended_session_expires"
.PD 0
.IP "calculate_initial_session_expires" 4
.IX Item "calculate_initial_session_expires"
.IP "create_session_id_if_needed" 4
.IX Item "create_session_id_if_needed"
.IP "delete_session_id" 4
.IX Item "delete_session_id"
.IP "extend_session_expires" 4
.IX Item "extend_session_expires"
.PD
Note: this is *not* used to give an individual user a longer session. See
\&'change_session_expires'.
.IP "extend_session_id" 4
.IX Item "extend_session_id"
.PD 0
.IP "get_session_id" 4
.IX Item "get_session_id"
.IP "reset_session_expires" 4
.IX Item "reset_session_expires"
.IP "session_is_valid" 4
.IX Item "session_is_valid"
.IP "set_session_id" 4
.IX Item "set_session_id"
.IP "initial_session_expires" 4
.IX Item "initial_session_expires"
.PD
.SH "USING SESSIONS DURING PREPARE"
.IX Header "USING SESSIONS DURING PREPARE"
The earliest point in time at which you may use the session data is after
Catalyst::Plugin::Session's \f(CW\*(C`prepare_action\*(C'\fR has finished.
.PP
State plugins must set \f(CW$c\fR\->session \s-1ID\s0 before \f(CW\*(C`prepare_action\*(C'\fR, and during
\&\f(CW\*(C`prepare_action\*(C'\fR Catalyst::Plugin::Session will actually load the data from
the store.
.PP
.Vb 2
\&    sub prepare_action {
\&        my $c = shift;
\&
\&        # don\*(Aqt touch $c\->session yet!
\&
\&        $c\->NEXT::prepare_action( @_ );
\&
\&        $c\->session;  # this is OK
\&        $c\->sessionid; # this is also OK
\&    }
.Ve
.SH "CONFIGURATION"
.IX Header "CONFIGURATION"
.Vb 3
\&    $c\->config(\*(AqPlugin::Session\*(Aq => {
\&        expires => 1234,
\&    });
.Ve
.PP
All configuation parameters are provided in a hash reference under the
\&\f(CW\*(C`Plugin::Session\*(C'\fR key in the configuration hash.
.IP "expires" 4
.IX Item "expires"
The time-to-live of each session, expressed in seconds. Defaults to 7200 (two
hours).
.IP "expiry_threshold" 4
.IX Item "expiry_threshold"
Only update the session expiry time if it would otherwise expire
within this many seconds from now.
.Sp
The purpose of this is to keep the session store from being updated
when nothing else in the session is updated.
.Sp
Defaults to 0 (in which case, the expiration will always be updated).
.IP "verify_address" 4
.IX Item "verify_address"
When true, \f(CW\*(C`$c\->request\->address\*(C'\fR will be checked at prepare time. If it is
not the same as the address that initiated the session, the session is deleted.
.Sp
Defaults to false.
.IP "verify_user_agent" 4
.IX Item "verify_user_agent"
When true, \f(CW\*(C`$c\->request\->user_agent\*(C'\fR will be checked at prepare time. If it
is not the same as the user agent that initiated the session, the session is
deleted.
.Sp
Defaults to false.
.IP "flash_to_stash" 4
.IX Item "flash_to_stash"
This option makes it easier to have actions behave the same whether they were
forwarded to or redirected to. On prepare time it copies the contents of
\&\f(CW\*(C`flash\*(C'\fR (if any) to the stash.
.SH "SPECIAL KEYS"
.IX Header "SPECIAL KEYS"
The hash reference returned by \f(CW\*(C`$c\->session\*(C'\fR contains several keys which
are automatically set:
.IP "_\|_expires" 4
.IX Item "__expires"
This key no longer exists. Use \f(CW\*(C`session_expires\*(C'\fR instead.
.IP "_\|_updated" 4
.IX Item "__updated"
The last time a session was saved to the store.
.IP "_\|_created" 4
.IX Item "__created"
The time when the session was first created.
.IP "_\|_address" 4
.IX Item "__address"
The value of \f(CW\*(C`$c\->request\->address\*(C'\fR at the time the session was created.
This value is only populated if \f(CW\*(C`verify_address\*(C'\fR is true in the configuration.
.IP "_\|_user_agent" 4
.IX Item "__user_agent"
The value of \f(CW\*(C`$c\->request\->user_agent\*(C'\fR at the time the session was created.
This value is only populated if \f(CW\*(C`verify_user_agent\*(C'\fR is true in the configuration.
.SH "CAVEATS"
.IX Header "CAVEATS"
.SS "Round the Robin Proxies"
.IX Subsection "Round the Robin Proxies"
\&\f(CW\*(C`verify_address\*(C'\fR could make your site inaccessible to users who are behind
load balanced proxies. Some ISPs may give a different \s-1IP\s0 to each request by the
same client due to this type of proxying. If addresses are verified these
users' sessions cannot persist.
.PP
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 \s-1OK\s0 for the address of the client to change. When the server sees that
this box is checked it should delete the \f(CW\*(C`_\|_address\*(C'\fR special key from the
session hash when the hash is first created.
.SS "Race Conditions"
.IX Subsection "Race Conditions"
In this day and age where cleaning detergents and Dutch football (not the
American kind) teams roam the plains in great numbers, requests may happen
simultaneously. This means that there is some risk of session data being
overwritten, like this:
.IP "1." 4
request a starts, request b starts, with the same session \s-1ID\s0
.IP "2." 4
session data is loaded in request a
.IP "3." 4
session data is loaded in request b
.IP "4." 4
session data is changed in request a
.IP "5." 4
request a finishes, session data is updated and written to store
.IP "6." 4
request b finishes, session data is updated and written to store, overwriting
changes by request a
.PP
For applications where any given user's session is only making one request
at a time this plugin should be safe enough.
.SH "AUTHORS"
.IX Header "AUTHORS"
Andy Grundman
.PP
Christian Hansen
.PP
Yuval Kogman, \f(CW\*(C`nothingmuch@woobling.org\*(C'\fR
.PP
Sebastian Riedel
.PP
Tomas Doran (t0m) \f(CW\*(C`bobtfish@bobtfish.net\*(C'\fR (current maintainer)
.PP
Sergio Salvi
.PP
kmx \f(CW\*(C`kmx@volny.cz\*(C'\fR
.PP
Florian Ragwitz (rafl) \f(CW\*(C`rafl@debian.org\*(C'\fR
.PP
Kent Fredric (kentnl)
.PP
And countless other contributers from #catalyst. Thanks guys!
.SH "Contributors"
.IX Header "Contributors"
Devin Austin (dhoss) <dhoss@cpan.org>
.PP
Robert Rothenberg <rrwo@cpan.org> (on behalf of Foxtons Ltd.)
.SH "COPYRIGHT & LICENSE"
.IX Header "COPYRIGHT & LICENSE"
.Vb 3
\&    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.
.Ve