NAME
    Catalyst::Plugin::Authorization::ACL - ACL support for Catalyst
    applications.

SYNOPSIS
            use Catalyst qw/
                    Authentication
                    Authorization::Roles
                    Authorization::ACL
            /;

            __PACKAGE__->setup;

            __PACKAGE__->deny_access_unless(
                    "/foo/bar",
                    [qw/nice_role/],
            );

            __PACKAGE__->allow_access_if(
                    "/foo/bar/gorch",
                    sub { return $boolean },
            );

DESCRIPTION
    This module provides Access Control List style path protection, with
    arbitrary rules for Catalyst applications. It operates only on the
    Catalyst private namespace, at least at the moment.

    The two hierarchies of actions and controllers in Catalyst are:

    Private Namespace
        Every action has it's own private path. This path reflects the Perl
        namespaces the actions were born in, and the namespaces of their
        controllers.

    External Namespace
        Some actions are also directly accessible from the outside, via a
        URL.

        The private and external paths will be the same, if you are using
        Local actions. Alternatively you can use "Path", "Regex", or
        "Global" to specify a different external path for your action.

    The ACL module currently only knows to exploit the private namespace. In
    the future extensions may be made to support external namespaces as
    well.

    Various types of rules are supported, see the list under "RULES".

    When a path is visited, rules are tested one after the other, with the
    most exact rule fitting the path first, and continuing up the path.
    Testing continues until a rule explcitly allows or denies access.

METHODS
  allow_access_if $path, $rule
    Check the rule condition and allow access to the actions under $path if
    the rule returns true.

    This is normally useful to allow acces only to a specific part of a tree
    whose parent has a "deny_access_unless" clause attached to it.

    If the rule test returns false access is not denied or allowed. Instead
    the next rule in the chain will be checked - in this sense the
    combinatory behavior of these rules is like logical OR.

  deny_access_unless $path, $rule
    Check the rule condition and disallow access if the rule returns false.

    This is normally useful to restrict access to any portion of the
    application unless a certain condition can be met.

    If the rule test returns true access is not allowed or denied. Instead
    the next rule in the chain will be checked - in this sense the
    combinatory behavior of these rules is like logical AND.

  allow_access $path
  deny_access $path
    Unconditionally allow or deny access to a path.

  acl_add_rule $path, $rule, [ $filter ]
    Manually add a rule to all the actions under $path using the more
    flexible (but more verbose) method:

            __PACKAGE__->acl_add_rule(
                    "/foo",
                    sub { ... }, # see FLEXIBLE RULES below
                    sub {
                            my $action = shift;
                            # return a true value if you want to apply the rule to this action
                            # called for all the actions under "/foo"
                    }
            };

    In this case the rule must be a sub reference (or method name) to be
    invoked on $c.

    The default filter will skip all actions starting with an underscore,
    namely "_DISPATCH", "_AUTO", etc (but not "auto", "begin", et al).

  acl_access_denied $c, $class, $action, $err
  acl_access_allowed $c, $class, $action
    The default event handlers for access denied or allowed conditions. See
    below on handling access violations.

  acl_allow_root_internals
    Adds rules that permit access to the root controller (YourApp.pm)
    "auto", "begin" and "end" unconditionally.

EXTENDED METHODS
  execute
    The hook for rule evaluation

  setup_actions
RULE EVALUATION
    When a rule is attached to an action the "distance" from the path it was
    specified in is recorded. The closer the path is to the rule, the
    earlier it will be checked.

    Any rule can either explicitly deny or explicitly allow access to a
    particular action. If a rule does not explicitly allow or permit access,
    the next rule is checked, until the list of rules is finished. If no
    rule has determined a policy, access to the path will be permitted.

PATHS
    To apply a rule to an action or group of actions you must supply a path.

    This path is what you should see dumped at the begining of the Catalyst
    server's debug output.

    For example, for the "foo" action defined at the root level of your
    application, specify "/foo". Under the "Moose" controller (e.g.
    "MyApp::C::Moose", the action "bar" will be "/moose/bar").

    The "distance" a path has from an action that is contained in it is the
    the difference in the number of slashes between the path of the action,
    and the path to which the rule was applied.

RULES
  Easy Rules
    There are several kinds of rules you can create without using the
    complex interface described in "FLEXIBLE RULES".

    The easy rules are all predicate list oriented. "allow_access_if" will
    explicitly allow access if the predicate is true, and
    "deny_access_unless" will explicitly disallow if the predicate is false.

    Role Lists
                __PACAKGE__->deny_access_unless( "/foo/bar", [qw/admin moose_trainer/] );

        When the role is evaluated the
        Catalyst::Plugin::Authorization::Roles will be used to check whether
        the currently logged in user has the specified roles.

        If "allow_access_if" is used, the presence of all the roles will
        immediately permit access, and if "deny_access_unless" is used the
        lack of any of the roles will immediately deny access.

        When specifying a role list without the
        Catalyst::Plugin::Authorization::Roles plugin loaded the ACL engine
        will throw an error.

    Predicate Code Reference / Method Name
        The code reference or method is invoked with the context and the
        action objects. The boolean return value will determine the behavior
        of the rule.

                __PACKAGE__->allow_access_if( "/gorch", sub { ... } );
                __PACKAGE__->deny_access_unless( "/moose", "method_name" );

        When specifying a method name the rule engine ensures that it can be
        invoked using "can" in UNIVERSAL.

    Constant
        You can use "undef", 0 and '' to use as a constant false predicate,
        or 1 to use as a constant true predicate.

  Flexible Rules
    These rules are the most annoying to write but provide the most
    flexibility.

    All access control is performed using exceptions -
    $Catalyst::Plugin::Authorization::ACL::Engine::DENIED, and
    $Catalyst::Plugin::Authorization::ACL::Engine::ALLOWED (these can be
    imported from the engine module).

    If no rule decides to explicitly allow or deny access, access will be
    permitted.

    Here is a rule that will always break out of rule processing by either
    explicitly allowing or denying access based on how much mojo the current
    user has:

            __PACKAGE__->acl_add_rule(
                    "/foo",
                    sub {
                            my ( $c, $action ) = @_;        

                            if ( $c->user->mojo > 50 ) {
                                    die $ALLOWED;
                            } else {
                                    die $DENIED;
                            }
                    }
            );

HANDLING DENIAL
    There are two plugin methods that can be called when a rule makes a
    decision about an action:

    acl_access_allowed
        A no-op

    acl_access_denied
        Looks for a private action named "access_denied" from the denied
        action's controller and outwards (much like "auto"), and if none is
        found throws an access denied exception.

    forcibly_allow_access
        Within an "access_denied" action this will immediately cause the
        blocked action to be executed anyway.

    This means that you have several alternatives:

  Provide an "access_denied" action
        package MyApp::Controller::Foo;

        sub access_denied : Private {
            my ( $self, $c, $action ) = @_;

            ...
            $c->forcibly_allow_access
                if $you->mean_it eq "really";

        }

    If you call "forcibly_allow_access" then the blocked action will be
    immediately unblocked. Otherwise the execution of the action will cease,
    and return to it's caller or end.

  Cleanup in "end"
        sub end : Private {
            my ( $self, $c ) = @_;

            if ( $c->error and $c->error->[-1] eq "access denied" ) {
                $c->error(0); # clear the error
                
            # access denied
            } else {
                # normal end
            }
        }

  Override the plugin event handler methods
        package MyApp;

        sub acl_access_allowed {
            my ( $c, $class, $action ) = @_;
            ...
        }

        sub acl_access_denied {
            my ( $c, $class, $action, $err ) = @_;
            ...
        }

    $class is the controller class the $action object was going to be
    executed in, and $err is the exception cought during rule evaluation, if
    any (access is denied if a rule raises an exception).

SEE ALSO
    Catalyst::Plugin::Authentication,
    Catalyst::Plugin::Authorization::Roles,
    <http://catalyst.perl.org/calendar/2005/24>

AUTHOR
    Yuval Kogman, "nothingmuch@woobling.org"

    Jess Robinson

COPYRIGHT & LICENCE
            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.