/ 
RDF-ACL-0.104
River stage zero No dependents
/ RDF::ACL

NAME

RDF::ACL - access control lists for the semantic web

SYNOPSIS

use RDF::ACL;

my $acl  = RDF::ACL->new('access.ttl');
my $auth = $acl->allow(
  webid => 'http://example.com/joe#me',
  item  => 'http://example.com/private/document',
  level => ['Read', 'Write'],
  );
$acl->save('turtle', 'access.ttl');

# later...

if ($acl->check('http://example.com/joe#me',
                'http://example.com/private/document',
                'Read'))
{
  print slurp("private/document");
}
else
{
  print "Denied";
}

# later...

foreach my $reason ($acl->why('http://example.com/joe#me',
                              'http://example.com/private/document',
                              'Read'))
{
  $acl->deny($reason) if defined $reason;
}
$acl->save('turtle', 'access.ttl');

DESCRIPTION

Note that this module provides access control and does not perform authentication!

Constructors

$acl->new($input, %args)

Creates a new access control list based on RDF data defined in $input. $input can be a serialised string of RDF, a file name, a URI or any other input accepted by the parse function of RDF::TrineX::Functions.

new() can be called with no arguments to create a fresh, clean ACL containing no authorisations.

$acl->new_remote($endpoint)

Creates a new access control list based on RDF data accessed via a remote SPARQL Protocol 1.0 endpoint.

Public Methods

$acl->check($webid, $item, $level, @data)

Checks an agent's authorisation to access an item.

$webid is the WebID (URI) of the agent requesting access to the item.

$item is the URL (URI) of the item being accessed.

$level is a URI identifying the type of access required. As special cases, the case-insensitive string 'read' is expanded to the URI <http://www.w3.org/ns/auth/acl#Read>, 'write' to <http://www.w3.org/ns/auth/acl#Write>, 'append' to <http://www.w3.org/ns/auth/acl#Append> and 'control' to <http://www.w3.org/ns/auth/acl#Control>.

If the access control list is local (not remote), zero or more additional RDF graphs can be passed (i.e. @data) containing data to take into consideration when checking the agent's authorisation. This data is trusted blindly, so should not include data that the user has themselves supplied. If the access control list is remote, then this method throws an error if any additional data is provided. (A remote ACL cannot take into account local data.)

If $level is provided, this method returns a boolean.

If $level is undefined or omitted, this method returns a list of URIs which each represent a type of access that the user is authorised.

$acl->why($webid, $item, $level, @data)

Investigates an agent's authorisation to access an item.

Arguments as per check, however $level is required.

Returns a list of authorisations that justify a user's access to the item with the given access level. These authorisations are equivalent to $authid values provided by allow().

In some cases (especially if the authorisation was created by hand, and not via allow()) an authorisation may not have an identifier. In these cases, the list will contain undef.

$acl->allow(%args)

Adds an authorisation to the ACL. The ACL must be mutable.

The method takes a hash of named arguments:

my $authid = $acl->allow(
  webid => 'http://example.com/joe#me',
  item  => 'http://example.com/private/document',
  level => ['Read', 'Write'],
  );

'item' is the URI of the item to authorise access to. As an alternative, 'item_class' may be used to authorise access to an entire class of items (using classes in the RDFS/OWL sense of the word). If neither of these arguments is provided, then the method will throw an error. Both may be provided. Either or both may be an arrayref, because an authorisation may authorise access to more than one thing.

'container' is an alternative to using 'item' or 'item_class'. It specifies the URI for a resource which in some way is a container for other resources. Setting authorisations for a container allows you to set a default authorisation for new items created within that container. (You must use the created() method to notify the ACL about newly created items.)

'webid' is the WebID (URI) of the person or agent being granted access. As an alternative, 'agent_class' may be used to authorise access to an entire class of agents. If neither is provided, an agent_class of <http://xmlns.com/foaf/0.1/Agent> is assumed. Both may be provided. Either or both may be an arrayref, because an authorisation may authorise access by more than one agent. (For consistency with 'item', 'agent' is supported as a synonym for 'webid'.)

'level' is the access level being granted. As with the check method, the shortcuts 'read', 'write', 'append' and 'control' may be used. An arrayref may be used. If no level is specified, 'read' is assumed.

This authorisation is not automatically saved, so it is probably useful to call save() after adding authorisations.

The method returns an identifier for the authorisation. This identifier may be needed again if you ever need to deny() the authorisation.

This method is aware of i_am()/who_am_i().

$acl->deny($authid)

Completely removes all traces of an authorisation from the ACL.

The authorisation identifier can be found using why() or you may have remembered it when you first allowed the access. In some cases (especially if the authorisation was created by hand, and not via allow()) an authorisation may not have an identifier. In these cases, you will have to be creative in figuring out how to deny access.

Returns the number of statements removed from the ACL's internal model as a result of the removal. (This will normally be at least 3.)

This authorisation is not automatically saved, so it is probably useful to call save() after removing authorisations.

This method is aware of i_am()/who_am_i().

$acl->created($item, $container)

Finds all authorisations which are the default for new items within $container and clones each of them for newly created $item.

Returns a list of authorisation identifiers.

$acl->i_am($webid)

Tells the ACL object to "act like" the agent with the given WebID.

If the ACL object is acting like you, then methods that make changes to the ACL (e.g. allow() and deny()) will only work if you have 'Control' permission over the resources specified.

$webid can be null to restore the usual behaviour.

Returns the previous WebID the ACL was acting like as a URI object.

$acl->who_am_i

Returns the WebID of the agent that ACL is acting like (if any).

$acl->save($format, $filename)

Serialises a local (not remote) ACL.

$format can be any format supported by the serialize function from RDF::TrineX::Functions.

If $filename is provided, this method writes to the file and returns the new file size in bytes.

If $filename is omitted, this method does not attempt to write to a file, and simply returns the string it would have written.

$acl->is_remote

Returns true if the ACL is remote; false if local.

$acl->is_mutable

Can this ACL be modified?

$acl->model

The graph model against which authorisation checks are made.

Returned as an RDF::Trine::Model object.

$acl->endpoint

The endpoint URI for remote (non-local) ACL queries.

Returned as a URI object.

BUGS

Please report any bugs to http://rt.cpan.org/.

SEE ALSO

Web::ID.

http://www.w3.org/ns/auth/acl.n3.

http://www.perlrdf.org/, http://lists.foaf-project.org/mailman/listinfo/foaf-protocols.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2010-2013 by Toby Inkster.

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

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.