Provided by: libcatalyst-manual-perl_5.9009-1_all 
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 (<http://creativecommons.org/licenses/by-sa/3.0/us/>).
perl v5.20.2 2014Catalyst::Manual::Tutorial::06_Authorization(3pm)