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NAME

       Catalyst::Manual::Tutorial::06_Authorization - Catalyst Tutorial - Chapter 6:
       Authorization

OVERVIEW

       This is Chapter 6 of 10 for the Catalyst tutorial.

       Tutorial Overview

       1.  Introduction

       2.  Catalyst Basics

       3.  More Catalyst Basics

       4.  Basic CRUD

       5.  Authentication

       6.  06_Authorization

       7.  Debugging

       8.  Testing

       9.  Advanced CRUD

       10. Appendices

DESCRIPTION

       This chapter of the tutorial adds role-based authorization to the existing authentication
       implemented in Chapter 5.  It provides simple examples of how to use roles in both TT
       templates and controller actions.  The first half looks at basic authorization concepts.
       The second half looks at how moving your authorization code to your model can simplify
       your code and make things easier to maintain.

       Source code for the tutorial in included in the /home/catalyst/Final directory of the
       Tutorial Virtual machine (one subdirectory per chapter).  There are also instructions for
       downloading the code in Catalyst::Manual::Tutorial::01_Intro.

BASIC AUTHORIZATION

       In this section you learn the basics of how authorization works under Catalyst.

   Update Plugins to Include Support for Authorization
       Edit "lib/MyApp.pm" and add "Authorization::Roles" to the list:

           # Load plugins
           use Catalyst qw/
               -Debug
               ConfigLoader
               Static::Simple

               StackTrace

               Authentication
               Authorization::Roles

               Session
               Session::Store::File
               Session::State::Cookie

               StatusMessage
           /;

       Once again, include this additional plugin as a new dependency in the Makefile.PL file
       like this:

           requires 'Catalyst::Plugin::Authorization::Roles';

   Add Role-Specific Logic to the "Book List" Template
       Open "root/src/books/list.tt2" in your editor and add the following lines to the bottom of
       the file:

           ...
           <p>Hello [% c.user.username %], you have the following roles:</p>

           <ul>
             [% # Dump list of roles -%]
             [% FOR role = c.user.roles %]<li>[% role %]</li>[% END %]
           </ul>

           <p>
           [% # Add some simple role-specific logic to template %]
           [% # Use $c->check_user_roles() to check authz -%]
           [% IF c.check_user_roles('user') %]
             [% # Give normal users a link for 'logout' %]
             <a href="[% c.uri_for('/logout') %]">User Logout</a>
           [% END %]

           [% # Can also use $c->user->check_roles() to check authz -%]
           [% IF c.check_user_roles('admin') %]
             [% # Give admin users a link for 'create' %]
             <a href="[% c.uri_for(c.controller.action_for('form_create')) %]">Admin Create</a>
           [% END %]
           </p>

       This code displays a different combination of links depending on the roles assigned to the
       user.

   Limit Books::add to 'admin' Users
       "IF" statements in TT templates simply control the output that is sent to the user's
       browser; it provides no real enforcement (if users know or guess the appropriate URLs,
       they are still perfectly free to hit any action within your application).  We need to
       enhance the controller logic to wrap restricted actions with role-validation logic.

       For example, we might want to restrict the "formless create" action to admin-level users
       by editing "lib/MyApp/Controller/Books.pm" and updating "url_create" to match the
       following code:

           =head2 url_create

           Create a book with the supplied title and rating,
           with manual authorization

           =cut

           sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
               # In addition to self & context, get the title, rating & author_id args
               # from the URL.  Note that Catalyst automatically puts extra information
               # after the "/<controller_name>/<action_name/" into @_
               my ($self, $c, $title, $rating, $author_id) = @_;

               # Check the user's roles
               if ($c->check_user_roles('admin')) {
                   # Call create() on the book model object. Pass the table
                   # columns/field values we want to set as hash values
                   my $book = $c->model('DB::Book')->create({
                           title   => $title,
                           rating  => $rating
                       });

                   # Add a record to the join table for this book, mapping to
                   # appropriate author
                   $book->add_to_book_authors({author_id => $author_id});
                   # Note: Above is a shortcut for this:
                   # $book->create_related('book_authors', {author_id => $author_id});

                   # Assign the Book object to the stash and set template
                   $c->stash(book     => $book,
                             template => 'books/create_done.tt2');
               } else {
                   # Provide very simple feedback to the user.
                   $c->response->body('Unauthorized!');
               }
           }

       To add authorization, we simply wrap the main code of this method in an "if" statement
       that calls "check_user_roles".  If the user does not have the appropriate permissions,
       they receive an "Unauthorized!"  message.  Note that we intentionally chose to display the
       message this way to demonstrate that TT templates will not be used if the response body
       has already been set.  In reality you would probably want to use a technique that
       maintains the visual continuity of your template layout (for example, using
       Catalyst::Plugin::StatusMessage as shown in the last chapter to redirect to an
       "unauthorized" page).

       TIP: If you want to keep your existing "url_create" method, you can create a new copy and
       comment out the original by making it look like a Pod comment.  For example, put something
       like "=begin" before "sub add : Local {" and "=end" after the closing "}".

   Try Out Authentication And Authorization
       Make sure the development server is running:

           $ script/myapp_server.pl -r

       Now trying going to <http://localhost:3000/books/list> and you should be taken to the
       login page (you might have to "Shift+Reload" or "Ctrl+Reload" your browser and/or click
       the "User Logout" link on the book list page).  Try logging in with both "test01" and
       "test02" (both use a password of "mypass") and notice how the roles information updates at
       the bottom of the "Book List" page. Also try the "User Logout" link on the book list page.

       Now the "url_create" URL will work if you are already logged in as user "test01", but
       receive an authorization failure if you are logged in as "test02".  Try:

           http://localhost:3000/books/url_create/test/1/6

       while logged in as each user.  Use one of the "logout" links (or go to
       <http://localhost:3000/logout> in your browser directly) when you are done.

ENABLE MODEL-BASED AUTHORIZATION

       Hopefully it's fairly obvious that adding detailed permission checking logic to our
       controllers and view templates isn't a very clean or scalable way to build role-based
       permissions into out application.  As with many other aspects of MVC web development, the
       goal is to have your controllers and views be an "thin" as possible, with all of the
       "fancy business logic" built into your model.

       For example, let's add a method to our "Books.pm" Result Class to check if a user is
       allowed to delete a book.  Open "lib/MyApp/Schema/Result/Book.pm" and add the following
       method (be sure to add it below the ""DO NOT MODIFY ..."" line):

           =head2 delete_allowed_by

           Can the specified user delete the current book?

           =cut

           sub delete_allowed_by {
               my ($self, $user) = @_;

               # Only allow delete if user has 'admin' role
               return $user->has_role('admin');
           }

       Here we call a "has_role" method on our user object, so we should add this method to our
       Result Class.  Open "lib/MyApp/Schema/Result/User.pm" and add the following method below
       the ""DO NOT MODIFY ..."" line:

           =head2 has_role

           Check if a user has the specified role

           =cut

           use Perl6::Junction qw/any/;
           sub has_role {
               my ($self, $role) = @_;

               # Does this user posses the required role?
               return any(map { $_->role } $self->roles) eq $role;
           }

       Let's also add Perl6::Junction to the requirements listed in Makefile.PL:

           requires 'Perl6::Junction';

       Note: Feel free to use "grep" in lieu of Perl6::Junction::any if you prefer.  Also, please
       don't let the use of the Perl6::Junction module above lead you to believe that Catalyst is
       somehow dependent on Perl 6... we are simply using that module for its easy-to-read
       <http://blogs.perl.org/users/marc_sebastian_jakobs/2009/11/my-favorite-module-of-the-
       month-perl6junction.html> "any" function.

       Now we need to add some enforcement inside our controller.  Open
       "lib/MyApp/Controller/Books.pm" and update the "delete" method to match the following
       code:

           =head2 delete

           Delete a book

           =cut

           sub delete :Chained('object') :PathPart('delete') :Args(0) {
               my ($self, $c) = @_;

               # Check permissions
               $c->detach('/error_noperms')
                   unless $c->stash->{object}->delete_allowed_by($c->user->get_object);

               # Saved the PK id for status_msg below
               my $id = $c->stash->{object}->id;

               # Use the book object saved by 'object' and delete it along
               # with related 'book_authors' entries
               $c->stash->{object}->delete;

               # Redirect the user back to the list page
               $c->response->redirect($c->uri_for($self->action_for('list'),
                   {mid => $c->set_status_msg("Deleted book $id")}));
           }

       Here, we "detach" to an error page if the user is lacking the appropriate permissions.
       For this to work, we need to make arrangements for the '/error_noperms' action to work.
       Open "lib/MyApp/Controller/Root.pm" and add this method:

           =head2 error_noperms

           Permissions error screen

           =cut

           sub error_noperms :Chained('/') :PathPart('error_noperms') :Args(0) {
               my ($self, $c) = @_;

               $c->stash(template => 'error_noperms.tt2');
           }

       And also add the template file by putting the following text into
       "root/src/error_noperms.tt2":

           <span class="error">Permission Denied</span>

       Log in as "test01" and create several new books using the "url_create" feature:

           http://localhost:3000/books/url_create/Test/1/4

       Then, while still logged in as "test01", click the "Delete" link next to one of these
       books.  The book should be removed and you should see the usual green "Book deleted"
       message.  Next, click the "User Logout" link and log back in as "test02".  Now try
       deleting one of the books.  You should be taken to the red "Permission Denied" message on
       our error page.

       Use one of the 'Logout' links (or go to the <http://localhost:3000/logout> URL directly)
       when you are done.

       You can jump to the next chapter of the tutorial here: Debugging

AUTHOR

       Kennedy Clark, "hkclark@gmail.com"

       Feel free to contact the author for any errors or suggestions, but the best way to report
       issues is via the CPAN RT Bug system at
       <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.

       Copyright 2006-2011, Kennedy Clark, under the Creative Commons Attribution Share-Alike
       License Version 3.0 (<https://creativecommons.org/licenses/by-sa/3.0/us/>).

perl v5.36.0                                2022Catalyst::Manual::Tutorial::06_Authorization(3pm)