man CGI::Application::Plugin::Authorization (3): Authorization framework for

SYNOPSIS

use base qw(CGI::Application);
use CGI::Application::Plugin::Authentication;
use CGI::Application::Plugin::Authorization;
# default config for runmode authorization
__PACKAGE__->authz->config(
DRIVER => [ 'HTGroup', FILE => 'htgroup' ],
);
# Using a named configuration to distinguish it from
# the above configuration
__PACKAGE__->authz('dbaccess')->config(
DRIVER => [ 'DBI',
DBH => $self->dbh,
TABLES => ['user', 'access'],
JOIN_ON => 'user.id = access.user_id',
CONSTRAINTS => {
'user.name' => '__USERNAME__',
'access.table' => '__PARAM_1__',
'access.item_id' => '__PARAM_2__'
}
],
);
sub admin_runmode {
my $self = shift;
# User must be in the admin group to have access to this runmode
return $self->authz->forbidden unless $self->authz->authorize('admin');
# rest of the runmode
...
}
sub update_widget {
my $self = shift;
my $widget = $self->query->param('widget_id');
# Can this user edit this widget in the widgets table?
return $self->authz->forbidden unless $self->authz('dbaccess')->authorize(widgets => $widget);
# save changes to the widget
...
}

DESCRIPTION

CGI::Application::Plugin::Authorization adds the ability to authorize users for specific tasks. Once a user has been authenticated and you know who you are dealing with, you can then use this plugin to control what that user has access to. It imports two methods ("authz" and "authorization") into your CGI::Application module. Both of these methods are interchangeable, so you should choose one and use it consistently throughout your code. Through the authz method you can call all the methods of the CGI::Application::Plugin::Authorization plugin.

Named Configurations

There could be multiple ways that you may want to authorize actions in different parts of your code. These differences may conflict with each other. For example you may have runmode level authorization that requires that the user belongs to a certain group. But secondly, you may have row level database authorization that requires that the username column of the table contains the name of the current user. These configurations would conflict with each other since they are authorizing using different information. To solve this you can create multiple named configurations, by specifying a unique name to the c<authz> method.

 __PACKAGE__->authz('dbaccess')->config(
     DRIVER => [ 'DBI', ... ],
 );
 # later
 $self->authz('dbaccess')->authorize(widgets => $widget_id);

EXPORTED METHODS

authz -and- authorization

These methods are interchangeable and provided for users that either prefer brevity, or clarity. Everything is controlled through this method call, which will return a CGI::Application::Plugin::Authorization object, or just the class name if called as a class method. When using the plugin, you will always first call $self->authz or __PACKAGE__->authz and then the method you wish to invoke. You can create multiple named authorization modules by providing a unique name to the call to authz. This will allow you to handle different types of authorization in your modules. For example, you could use the main configuration to do runmode level authorization, and use a named configuration to manage database row level authorization.

METHODS

config

This method is used to configure the CGI::Application::Plugin::Authorization module. It can be called as an object method, or as a class method.

The following parameters are accepted:

DRIVER

Here you can choose which authorization module(s) you want to use to perform the authorization. For simplicity, you can leave off the CGI::Application::Plugin::Authorization::Driver:: part when specifying the DRIVER parameter. If this module requires extra parameters, you can pass an array reference that contains as the first parameter the name of the module, and the required parameters as the rest of the array. You can provide multiple drivers which will be used, in order, to check the permissions until a valid response is received.

  DRIVER => [ 'DBI', dbh => $self->dbh ],
  - or -
  DRIVER => [
    [ 'HTGroup', file => '.htgroup' ],
    [ 'LDAP', binddn => '...', host => 'localhost', ... ]
  ],

FORBIDDEN_RUNMODE

Here you can specify a runmode that the user will be redirected to if they fail the authorization checks.

  FORBIDDEN_RUNMODE => 'forbidden'

FORBIDDEN_URL

If your forbidden page is external to this module, then you can use this option to specify a URL that the user will be redirected to when they fail the authorization checks. If both FORBIDDEN_URL and FORBIDDEN_RUNMODE are specified, then the latter will take precedence.

  FORBIDDEN_URL => 'http://example.com/forbidden.html'

GET_USERNAME

This option allows you to provide a method that should return us the username of the currently logged in user. It will be passed the current authz objects as the only parameter. This is not a required option, and can be omitted if you use the Authentication plugin, or if your authentication system sets $ENV{REMOTE_USER}.

  GET_USERNAME => sub { my $authz = shift; return $authz->cgiapp->my_username }

authz_runmodes

This method takes a list of runmodes that are to be authorized, and the authorization rules for said runmodes. If a user tries to access one of these runmodes, then they will be redirected to the forbidden page unless authorization is granted.

The runmode names can be simple strings, regular expressions, coderefs (which are passed the name of the runmode as their only parameter), or special directives that start with a colon.

The authorization rules can be simple strings representing the name of the group that the user must be a member of, as a list-ref of group names (of which the user only has to be a member of any one of the groups, or as a code-ref that will be called (with no parameters).

This method is cumulative, so if it is called multiple times, the new values are appended to the list of existing entries. It returns a list containing all of the entries that have been configured thus far.

NOTE: compatibility with the interface as was defined in 0.06 is preserved. 0.06 allowed for runmodes to be passed in as a list-ref of two-element lists to specify authorization rules. Although this interface is supported, the extra list-refs aren't necessary.

:all - All runmodes in this module will require authorization

  # match all runmodes
  __PACKAGE__->authz->authz_runmodes(
      ':all' => 'admin',
      );
  # only protect runmodes one and two
  __PACKAGE__->authz->authz_runmodes(
      one => 'admin',
      two => 'admin',
      );
  # protect only runmodes that start with auth_
  __PACKAGE__->authz->authz_runmodes(
      qr/^authz_/ => 'admin',
      );
  # protect all runmodes that *do not* start with public_
  __PACKAGE__->authz->authz_runmodes(
      qr/^(?!public_)/ => 'admin',
      );
  # preserve the interface from 0.06:
  __PACKAGE__->authz->authz_runmodes(
      [':all' => 'admin'],
      );

is_authz_runmode

This method accepts the name of a runmode, and if that runmode requires authorization (ie the user needs to be a member of a particular group or has to satisfy some other authorization rule) then this method returns the corresponding authorization rule which must be satisfied (which could be either a scalar, a list-ref, or a code-ref, depending on how the rules were defined).

new

This method creates a new CGI::Application::Plugin::Authorization object. It requires as it's only parameter a CGI::Application object. This method should never be called directly, since the "authz" method that is imported into the CGI::Application module will take care of creating the CGI::Application::Plugin::Authorization object when it is required.

instance

This method works the same way as "new", except that it returns the same Authorization object for the duration of the request. This method should never be called directly, since the "authz" method that is imported into the CGI::Application module will take care of creating the CGI::Application::Plugin::Authorization object when it is required.

authorize

This method will test to see if the current user has access to the given resource. It will take the given parameters and test them against the DRIVER classes that have been configured. A true return value means the user should have access to the given resource.

 # is the current user in the admin group
 if ($self->authz->authorize('admingroup')) {
    # perform an admin action
 }

username

This method will return the name of the currently logged in user. It uses three different methods to figure out the username:

GET_USERNAME option: Use the subroutine provided by the GET_USERNAME option to figure out the current username
CGI::Application::Plugin::Authentication: See if the CGI::Application::Plugin::Authentication plugin is being used, and retrieve the username through this plugin
REMOTE_USER: See if the REMOTE_USER environment variable is set and use that value

drivers

This method will return a list of driver objects that are used for this authorization instance.

cgiapp

This will return the underlying CGI::Application object.

setup_runmodes

This method is called during the prerun stage to register some custom runmodes that the Authentication plugin requires in order to function.

CGI::Application CALLBACKS

We'll automatically add the "authz_forbidden" run mode if you are using CGI::Application 4.0 or greater.

If you are using an older version of CGI::Application you will need to add it yourself.

 sub cgiapp_prerun {
    my $self = shift;
    $self->run_modes( authz_forbidden => \&CGI::Application::Plugin::Authorization::authz_forbidden, );
 }

prerun_callback

This method is a CGI::Application prerun callback that will be automatically registered for you if you are using CGI::Application 4.0 or greater. If you are using an older version of CGI::Application you will have to create your own cgiapp_prerun method and make sure you call this method from there.

 sub cgiapp_prerun {
    my $self = shift;
    $self->CGI::Application::Plugin::Authorization::prerun_callback();
 }

redirect_to_forbidden

This method is be called during the prerun stage if the current user is not authorized, and they are trying to access an authz runmode. It will redirect to the page that has been configured as the forbidden page, based on the value of FORBIDDEN_RUNMODE or FORBIDDEN_URL If nothing is configured then the default forbidden page will be used.

forbidden

This will return a forbidden page. It checks the configuration to see if there is a custom runmode or URL to redirect to, otherwise it calls the builtin authz_forbidden runmode.

CGI::Application RUNMODES

authz_forbidden

This runmode is provided if you do not want to create your own forbidden runmode. It will display a simple error page to the user.

authz_dummy_redirect

This runmode is provided for convenience when an external redirect needs to be done. It just returns an empty string.

EXAMPLE

In a CGI::Application module:

  package MyCGIApp;
  use base qw(CGI::Application);
  use CGI::Application::Plugin::AutoRunmode;
  use CGI::Application::Plugin::Authentication;
  use CGI::Application::Plugin::Authorization;
  
  # Configure Authentication
  MyCGIApp->authen->config(
        DRIVER => 'Dummy',
  );
  MyCGIApp->authen->protected_runmodes(qr/^admin_/);
  # Configure Authorization (manages runmode authorization)
  MyCGIApp->authz->config(
      DRIVER => [ 'DBI',
          DBH         => $self->dbh,
          TABLES      => ['user', 'usergroup', 'group'],
          JOIN_ON     => 'user.id = usergroup.user_id AND usergroup.group_id = group.id',
          CONSTRAINTS => {
             'user.name'  => '__USERNAME__',
             'group.name' => '__GROUP__',
          }
      ],
  );
  MyCGIApp->authz->authz_runmodes(
     [a_runmode => 'a_group'],
     [qr/^admin_/ => 'admin'],
     [':all' => 'all_group'],
     [sub {my $rm = shift; return ($rm eq "dangerous_rm")} => 'super_group'],
  );
  # Configure second Authorization module using a named configuration
  __PACKAGE__->authz('dbaccess')->config(
      DRIVER => [ 'DBI',
          DBH   => $self->dbh,
          TABLES      => ['user', 'access'],
          JOIN_ON     => 'user.id = access.user_id',
          CONSTRAINTS => {
              'user.name'      => '__USERNAME__',
              'access.table'   => '__PARAM_1__',
              'access.item_id' => '__PARAM_2__'
          }
      ],
  );
  sub start : Runmode {
    my $self = shift;
  }
  sub admin_one : Runmode {
    my $self = shift;
    # The user will only get here if they are logged in and
    # belong to the admin group
  }
  sub admin_widgets : Runmode {
    my $self = shift;
    # The user will only get here if they are logged in and
    # belong to the admin group
    # Can this user edit this widget in the widgets table?
    my $widget_id = $self->query->param('widget_id');
    return $self->authz->forbidden unless $self->authz('dbaccess')->authorize(widgets => $widget_id);
    
  }

TODO

The module is definitely in a usable state, but there are still some parts missing that I would like to add in:

provide easy methods for authorizing runmode access automatically
allow subroutine attributes to configure authorization for a runmode
write a tutorial/cookbook to include with the docs

BUGS

This is alpha software and as such, the features and interface are subject to change. So please check the Changes file when upgrading.

AUTHOR

Cees Hek <[email protected]>

CREDITS

Thanks to SiteSuite (http://www.sitesuite.com.au) for funding the development of this plugin and for releasing it to the world.

LICENCE AND COPYRIGHT

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

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.