NAME
    Catalyst::Plugin::HashedCookies - Tamper-resistant HTTP Cookies

VERSION
    version 1.123540

SYNOPSIS
     use Catalyst qw/HashedCookies/;
     MyApp->config->{hashedcookies} = {
         key       => $secret_key,
         algorithm => 'SHA1', # optional
         required  => 1,      # optional
     };
     MyApp->setup;

     # later, in another part of MyApp...

     print "this cookie tastes good!\n"
      if $c->request->valid_cookie('my_cookie_name');

DESCRIPTION
  Overview
    When HTTP cookies are used to store a user's state or identity it's
    important that your application is able to distinguish legitimate
    cookies from those that have been edited or created by a malicious user.

    This module allows you to determine whether a cookie presented by a
    client was created in its current state by your own application.

  Implementation
    HashedCookies adds a keyed cryptographic hash to each cookie that your
    application creates, and checks every client-provided cookie for a valid
    hash.

    This is done in a transparent way such that you do not need to change
    any application code that handles cookies when using this plugin. A
    cookie that fails to contain a valid hash will still be available to
    your application through "$c->request->cookie()".

    Two additional methods within the Catalyst request object allow you to
    check the status (in other words, the vailidity) of your cookies.

METHODS
  Catalyst Request Object Methods
    "$c->request->valid_cookie($cookie_name)"
        If a cookie was successfully authenticated then this method will
        return True, otherwise it will return False.

    "$c->request->invalid_cookie($cookie_name)"
        If a cookie failed its authentication, then this method will return
        True, otherwise it will return False. Please read the
        "CONFIGURATION" section below to understand what 'failed
        authentication' really means.

CONFIGURATION
    key
         MyApp->config->{hashedcookies}->{key} = $secret_key;

        This parameter is required, and sets the secret key that is used to
        generate a message authentication hash. Clearly, for a returned
        cookie to be authenticated the same key must be used both when
        setting the cookie and retrieving it.

    algorithm
         MyApp->config->{hashedcookies}->{algorithm} = 'SHA1';
           # or
         MyApp->config->{hashedcookies}->{algorithm} = 'MD5';

        This parameter is optional, and will default to "SHA1" if not set.
        It instructs the module to use the given message digest algorithm.

    required
         MyApp->config->{hashedcookies}->{required} = 0;
           # or
         MyApp->config->{hashedcookies}->{required} = 1;

        This parameter is optional, and will default to 1 if not set.

        If a cookie is read from the client but does not contain a
        HashedCookies hash (i.e. this module was not running when the cookie
        was set), then this parameter controls whether the cookie is
        ignored.

        Setting this parameter to True means that a cookie without a hash is
        treated as if it did have a hash, and therefore the authentication
        will fail. Setting this parameter to False means that the cookie
        will be ignored.

        When a cookie is ignored, neither "$c->request->valid_cookie()" nor
        "$c->request->invalid_cookie()" will return True, but you can of
        course still access the cookie through "$c->request->cookie()".

DIAGNOSTICS
    'Request for unknown digest algorithm to ...'
        You have attempted to configure this module with an unrecognized
        message digest algorithm. Please see the "CONFIGURATION" section for
        the valid algorithms.

    '"key" is a required configuration parameter to ...'
        You have forgotten to set the secret key that is used to generate a
        message authentication hash. See the "SYNOPSIS" or "CONFIGURATION"
        section for examples of how to set this parameter.

    'Attempted use of restricted ("_hashedcookies_*") value in cookie'
        This module adds values to your cookie, and to avoid clashes with
        your own values they are named in a special way. If you try to set a
        cookie with values matching this special name format, your Catalyst
        Engine's default error handler will be triggered, and the response
        status code will be set to "500".

        You cannot trap such errors because they are raised after all the
        application code has run, but you will see the above error in your
        log file, and your Application will certainly halt so that Catalyst
        can display its error page.

    'Please make a Request subclass for your application which isa
    Catalyst::Request::HashedCookies'
        In order to properly hook into Catalyst, you need a Class for the
        Catalyst Request object which isa
        "Catalyst::Request::HashedCookies". This error is thrown not if you
        are using "Catalyst::Request" as the Class (this is detected and
        worked around), but instead some 3rd party Class.

        It can happen, apparently, to "Catalyst::Action::REST" users. Please
        check the Catalyst wiki for some examples on how to fix your
        application.

DEPENDENCIES
    Other than the natural dependencies of Catalyst and the contents of the
    standard Perl distribution, you will need the following:

    *   Digest::HMAC

BUGS
    Please report any bugs or feature requests to
    "bug-catalyst-plugin-hashedcookies@rt.cpan.org", or through the web
    interface at
    <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Catalyst-Plugin-HashedCo
    okies>. I will be notified, and then you'll automatically be notified of
    progress on your bug as I make changes.

SEE ALSO
    Catalyst, Digest::HMAC_SHA1, Digest::HMAC_MD5

    <http://www.schneier.com/blog/archives/2005/08/new_cryptanalyt.html>

AUTHOR
    Oliver Gorwits <oliver@cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2012 by University of Oxford.

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