The Fedora WebAC authorization module is an implementation of the W3C's still evolving draft of an RDF-based decentralized authorization policy mechanism.
W3C's definition of WebAccessControl
From the WebAccessControl description at the W3C website:
WebAccessControl is a decentralized system for allowing different users and groups various forms of access to resources where users and groups are identified by HTTP URIs.
The WebAC module will enforce access control based on the Access Control List (ACL) RDF resource associated with the requested resource. In WebAC, an ACL consists of a set of Authorizations. Each Authorization is a single rule for access, such as "users alice and bob may write to resource foo", described with a set of RDF properties. Authorizations have the RDF type http://www.w3.org/ns/auth/acl#Authorization.
For the remainder of this document, the http://www.w3.org/ns/auth/acl# namespace will be abbreviated with the prefix acl:.
Authorizations
The properties that may be used on an acl:Authorization are:
| Property | Meaning |
|---|---|
acl:accessTo |
the URI of the protected resource |
acl:agent |
the user (in the W3C WebAC ontology, the user is named with a URI, but Fedora's implementation supports both URI- and string-based usernames) |
acl:mode |
the type of access (WebAC defines several modes: acl:Read, acl:Write, acl:Append, and acl:Control; Fedora implements acl:Read and acl:Write) |
acl:accessToClass |
an RDF class of protected resources |
acl:agentClass |
a group of users (defined as a foaf:Group resource listing its users with the foaf:member property) |
For a more detailed explanation of Authorizations and their properties, see WebAC Authorizations.
Examples of Authorizations
The user userA can Read document foo
Users in NewsEditor group can Write to any resource of type ex:News
/agents/NewsEditors
The user userB can Read document foo (This involves setting a system property for the servlet container, e.g.
-Dfcrepo.auth.webac.userAgent.baseUri=http://example.org/agents/)
Storing WebAC ACLs in Fedora 4
In Fedora 4, an ACL is a ldp::BasicContainer resource with the additional RDF type of http://fedora.info/definitions/v4/webac#Acl. This class is part of the Fedora WebAC ontology. Its children should each be resources of type acl:Authorization. It is given the namespace prefix webac: by convention.
Protecting Resources
A resource specifies the location of its ACL using the acl:accessControl property. If a resource itself does not specify an ACL, its parent containers are inspected, and the first specified ACL found is used as the ACL for the requested resource. If no ACLs are found, a filesystem-based ACL will be checked, the default policy of which is to deny access to the requested resource.
Example Scenarios
These scenarios assume that Fedora has been configured to use fcrepo.auth.webac.userAgent.baseUri=http://example.org/agent/ and fcrepo.auth.webac.groupAgent.baseUri=http://example.org/group/
I want to allow a user with username "smith123" to have read, write access to resource http://localhost:8080/rest/webacl_box1.
I want to let the group "Editors" have read, write access on all the items in the collection "http://localhost:8080/rest/box/bag/collection"
I would like the collection http://localhost:8080/rest/dark/archive to be viewable only by the groupId "Restricted", but I would like to allow anyone to view the resource http://localhost:8080/rest/dark/archive/sunshine.
The collection http://localhost:8080/rest/public_collection should be readable by anyone but only editable by users in the group Editors.
Only the ex:publicImage type objects in the container http://localhost:8080/rest/mixedCollection are viewable by anyone, all others are only viewable by the group Admins.
