The Fedora WebAC authorization Fedora module is an implementation of the W3C's still evolving draft by the W3C that proposes a of an RDF-based decentralized authorization policy mechanism. See WebAccessControl specifications at the W3C website.

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. The ACL resource should specify the types of access, allowed users or groups, and applicable resources.

User -> Read/Write/Append/Control -> Resource/ResourceType

Example:

1. userA can Read document foo
@prefix acl: <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#>

</acls/read> acl:accessTo </foo> ;
acl:mode acl:Read;
acl:agent </agents/userA> .

acl#Authorization.

For the remainder of this document, the 2. users in NewsEditor group can Write to any resource of type News
@prefix acl: <http://www.w3.org/ns/auth/acl#>

</acls/write> acl:accessToClass </objecttype/news> ;
acl:mode acl:Read, acl:Write;
acl:agentClass </agents/newsEditor> .

Steps in determining the effective authorization:

Get the ACL of the requested resource.
1. if ACL exists:
  1. Find union of authorizations that specify access for the requesting user. This includes:
    1. authorizations that specify accessTo to the requested resource.
    2. authorizations that specify accessToClass of the requested resource type.
  2. Find union of authorizations that specify access for the requesting user's group. This includes:
    1. authorizations that specify accessTo to the requested resource.
    2. authorizations that specify accessToClass of the requested resource type.
  3. If authorizations exist for user or group:
    1. Find the union of authorizations found from steps 1.a.i and 1.a.ii.
    2. Go to step 4.
  4. if no authorization exist for user or group:
    1. Deny Access. ~~Go to step 2.~~
2. if no ACL exists for requested resource:
  1. Go to step 2.
Get the ACL of the next ancestor (using either ldp:contains or fedora:hasParent).
1. if ACL exists:
  1. Find union of authorizations that specify access for the requesting user. This includes:
    1. authorizations that specify accessTo to the requested resource.
    2. authorizations that specify accessToClass of the requested resource type.
  2. Find union of authorizations that specify access for the requesting user's group. This includes:
    1. authorizations that specify accessTo to the requested resource.
    2. authorizations that specify accessToClass of the requested resource type.
  3. If authorizations exist for user or group:
    1. Find the union of authorizations found from steps 2.a.i and 2.a.ii.
    2. Go to step 4.
  4. Find union of authorizations that specify access for the requesting user. This includes:
    1. authorizations that specify accessTo to the requested resource's ancestor.
  5. Find union of authorizations that specify access for the requesting user's group. This includes:
    1. authorizations that specify accessToClass of to the requested resource's ancestor.
  6. If authorizations exist for user or group:
    1. Find the union of authorizations found from steps 2.a.iv and 1.a.v.
    2. Go to step 4.
  7. if no authorization exist for user or group:
    1. Deny Access. ~~Go to step 2.~~
2. if no ACL exists for the current ancestor resource:
  1. Go to step 2.
If no more ancestor exist (root node reached) and no ACL or no matching authorization is found:
1. Deny access.
Use the most permissive from the set of authorizations found.
1. Grant access if the authorizations permit requested access mode (read, write, append).
2. Deny access if the authorizations does not permit requested access mode.

Example Request Authorization Flow:

...

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

Code Block

language	text

@prefix acl: <http://www.w3.org/ns/auth/acl#>

<> a acl:Authorization ;
    acl:accessTo </foo> ;
    acl:mode acl:Read;
    acl:agent "userA" .

Users in NewsEditor group can Write to any resource of type ex:News

Code Block

language	text

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
@prefix ex: <http://example.org/ns#> .

<> a acl:Authorization ;
    acl:accessToClass ex:News ;
    acl:mode acl:Read, acl:Write;
    acl:agentClass </agents/NewsEditor> .

Code Block

language	text
title	/agents/NewsEditors

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

<> a foaf:Group;
    foaf:member "editor1", "editor2".

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/)
Code Block
language text
@prefix acl: <http://www.w3.org/ns/auth/acl#> <> a acl:Authorization ; acl:accessTo </foo> ; acl:mode acl:Read; acl:agent <http://example.org/agents/userB> .

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/

Example Scenarios

I want to allow a user with username "smith123" to have read, write access to resource http://localhost:8080/rest/webacl_box1.

Expand

Using the two "files" below to create our Authorization and ACL resources..

Code Block

title	Acl.ttl

@prefix webac: <http://fedora.info/definitions/v4/webac#> .

Code Block

title	Acl.ttl

<> a ???webac:WebAclAcl .

Code Block

title	Authorization.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
<> a acl:Authorization ;
   acl:agent "smith123"<http://example.org/agent/smith123> ;
   acl:mode acl:Read, acl:Write ;
   acl:accessTo <http://localhost:8080/rest/webacl_box1> .

We would execute the following commands.

Code Block

> curl -X POSTPUT -H "Content-type: text/turtle" --data-binary "@Acl.ttl" "http://localhost:8080/rest"

http://localhost:8080/rest/acl

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Authorization.ttl" "http://localhost:8080/rest/acl/auth1"

http://localhost:8080/rest/acl/auth1

> echo "PREFIX acl: <http://www.w3.org/ns/auth/acl#>
INSERT INTODATA {
<> acl:accessControl <http://localhost:8080/rest/acl> .
}" | curl -X PATCH -H "Content-type: application/sparql-update" --upload-file - "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"

Expand

Using the two "files" below to create our Authorization and ACL resources.

.

Code Block

title	Acl.ttl

@prefix webac: <http://fedora.info/definitions/v4/webac#> .

Code Block

title	Acl.ttl

<> a ???webac:WebAclAcl .

Code Block

title	Authorization.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
<> a acl:Authorization ;
   acl:agent "Editors"<http://example.org/group/Editors> ;
   acl:mode acl:Read, acl:Write ;
   acl:accessTo <http://localhost:8080/rest/box/bag/collection> .

We would execute the following commands.

Code Block

> curl -X POST -H "Content-type: text/turtle" --data-binary "@Acl.ttl" "http://localhost:8080/rest"

http://localhost:8080/rest/acl

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Authorization.ttl" "http://localhost:8080/rest/acl/auth1"

http://localhost:8080/rest/acl/auth1

> echo "PREFIX acl: <http://www.w3.org/ns/auth/acl#>
INSERT INTODATA {
<> acl:accessControl <http://localhost:8080/rest/acl> .
}" | curl -X PATCH -H "Content-type: application/sparql-update" --upload-file - "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.

Expand

Using the three "files" below to create our Authorization and ACL resources..

Code Block

title	Acl.ttl

@prefix webac: <http://fedora.info/definitions/v4/webac#> .

Code Block

title	Acl.ttl

<> a ???webac:WebAclAcl .

Code Block

title	Auth_restricted.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
<> a acl:Authorization ;
   acl:agent "Restricted"<http://example.org/group/Restricted> ;
   acl:mode acl:Read ;
   acl:accessTo <http://localhost:8080/rest/dark/archive> .

Code Block

title	Auth_open.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
<> a acl:Authorization ;
   acl:agent foaf:Agent ;
   acl:mode acl:Read ;
   acl:accessTo <http://localhost:8080/rest/dark/archive/sunshine> .

The I would execute the following commands.

Code Block

> curl -X POST -H "Content-type: text/turtle" --data-binary "@Acl.ttl" "http://localhost:8080/rest"

http://localhost:8080/rest/acl_lock

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Auth_restricted.ttl" "http://localhost:8080/rest/acl_lock/auth1"

http://localhost:8080/rest/acl_lock/auth1

> echo "PREFIX acl: <http://www.w3.org/ns/auth/acl#>
INSERT INTODATA {
<> acl:accessControl <http://localhost:8080/rest/acl_lock> .
}" | curl -X PATCH -H "Content-type: application/sparql-update" --upload-file - "http://localhost:8080/rest/dark/archive"

> curl -X POST -H "Content-type: text/turtle" --data-binary "@Acl.ttl" "http://localhost:8080/rest"

http://localhost:8080/rest/acl_open

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Auth_open.ttl" "http://localhost:8080/rest/acl_open/auth2"

http://localhost:8080/rest/acl_open/auth2

> echo "PREFIX acl: <http://www.w3.org/ns/auth/acl#>
INSERT INTODATA {
<> acl:accessControl <http://localhost:8080/rest/acl_open> .
}" | curl -X PATCH -H "Content-type: application/sparql-update" --upload-file - "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.

Expand

Using the three "files" below to create our Authorization and ACL resources..

Code Block

title	Acl.ttl

@prefix webac: <http://fedora.info/definitions/v4/webac#> .

Code Block

title	Acl.ttl

<> a ???webac:WebAclAcl .

Code Block

title	Auth1.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
<> a acl:Authorization ;
   acl:agent foaf:Agent ;
   acl:mode acl:Read ;
   acl:accessTo <http://localhost:8080/rest/public_collection> .

Code Block

title	Auth2.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
<> a acl:Authorization ;
   acl:agent "Editors"<http://example.org/group/Editors> ;
   acl:mode acl:Read, acl:Write ;
   acl:accessTo <http://localhost:8080/rest/public_collection> .

I would execute the following code:

Code Block

> curl -X POST -H "Content-type: text/turtle" --data-binary "@Acl.ttl" "http://localhost:8080/rest"

http://localhost:8080/rest/acl

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Auth1.ttl" "http://localhost:8080/rest/acl/auth1"

http://localhost:8080/rest/acl/auth1

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Auth2.ttl" "http://localhost:8080/rest/acl/auth2"

http://localhost:8080/rest/acl/auth2

> echo "PREFIX acl: <http://www.w3.org/ns/auth/acl#>
INSERT INTODATA {
<> acl:accessControl <http://localhost:8080/rest/acl> .
}" | curl -X PATCH -H "Content-type: application/sparql-update" --upload-file - "http://localhost:8080/rest/public_collection"

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.

Expand

Using the three "files" below to create our Authorization and ACL resources.

Code Block

title	Acl.ttl	Acl.ttl

@prefix webac: <http://fedora.info/definitions/v4/webac#> .
<> a ???webac:WebAclAcl .

Code Block

title	Auth_restricted.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
<> a acl:Authorization ;
   acl:agent 'Admins'<http://example.org/group/Admins> ;
   acl:mode acl:Read ;
   acl:accessTo <http://localhost:8080/rest/mixedCollection> .

Code Block

title	Auth_open.ttl

@prefix acl: <http://www.w3.org/ns/auth/acl#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
<> a acl:Authorization ;
   acl:agent foaf:Agent ;
   acl:mode acl:Read ;
   acl:accessToClass ex:publicImage .

I would execute the following commands:

Code Block

> curl -X POST -H "Content-type: text/turtle" --data-binary "@Acl.ttl" "http://localhost:8080/rest"

http://localhost:8080/rest/acl

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Auth_restricted.ttl" "http://localhost:8080/rest/acl/auth1"

http://localhost:8080/rest/acl/auth1

> curl -X PUT -H "Content-type: text/turtle" --data-binary "@Auth_open.ttl" "http://localhost:8080/rest/acl/auth2"

http://localhost:8080/rest/acl/auth2

> echo "PREFIX acl: <http://www.w3.org/ns/auth/acl#>
INSERT INTODATA {
<> acl:accessControl <http://localhost:8080/rest/acl> .
}" | curl -X PATCH -H "Content-type: application/sparql-update" --upload-file - "http://localhost:8080/rest/mixedCollection"

...

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Versions Compared

Old Version 19

New Version Current

Key

W3C's definition of WebAccessControl

Example:

Steps in determining the effective authorization:

Example Request Authorization Flow:

Authorizations

Examples of Authorizations

Storing WebAC ACLs in Fedora 4

Protecting Resources

Example Scenarios

Example Scenarios

How-To Guides

More Detailed Documentation

Page tree

Page History

Versions Compared

Old Version 19

New Version Current

Key

W3C's definition of WebAccessControl

Example:

Steps in determining the effective authorization:

Example Request Authorization Flow:

Authorizations

Examples of Authorizations

Storing WebAC ACLs in Fedora 4

Protecting Resources

Example Scenarios

Example Scenarios

How-To Guides

More Detailed Documentation