Sponger ACL Rules

Introduction

The Virtuoso Sponger can be controlled via ACLs (Access Control Lists); basically, rules which define who is allowed to Sponge and who is not. It is also possible to restrict use of particular Sponger Cartridges. The ACL system is optional, and is enabled using a SPARQL pragma and the ACL Scope system as described below.

ACL Checking Layers

The Sponger can be accessed via several routes. These are depicted below. Sponging is provided as an optional service utilized by other service endpoints layered on top. For sponging to occur, the service layers above the Sponger, and also the graph security settings (both enforced by VAL and the RDF Graph Security System), must all grant sponge permission.

Having sponge permission means that sponging might occur (i.e. sponge attempts will not be blocked by VAL); it doesn't guarantee that sponging will occur. Whether sponging is done depends on whether the Sponger cache for the target data source URI is stale (as determined by the Sponger cache invalidation rules) and whether a re-sponge is forced through a Sponger option (the re-sponge option depends on which service is used to invoke sponging: /about, /describe or SPARQL).

Scopes Applicable to the Sponger

Two scopes control access to the Sponger:

oplacl:Query
- Controls access to the Sponger in general and whether a user is able to sponge at all
oplacl:SpongerCartridges
- Restricts access to particular Sponger cartridges

Enabling ACLs for General Sponger Use

By default, Sponger ACLs are disabled in all realms. (See also ACL Scopes in VAL.)

To enable evaluation of SPARQL ACL rules in the default realm (which includes services /sparql, /describe and /about, all of which support sponging) to determine whether the user may Sponge, enable the oplacl:Query scope. This can be done through the Conductor UI or by executing the following SPARQL:

SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
  WITH  <urn:virtuoso:val:config>
    DELETE 
      { oplacl:DefaultRealm  oplacl:hasDisabledAclScope  oplacl:Query }
    INSERT
      { oplacl:DefaultRealm  oplacl:hasEnabledAclScope   oplacl:Query }
;

SPARQL ACLs refer to ACLs which regulate who has which SPARQL permissions (Read, Update, Sponge, List).

Enabling ACLs for Cartridge-Specific Control

By default, as with generic Sponger ACLs, Cartridge ACLs are disabled in all realms. (See also ACL Scopes in VAL.)

To enable evaluation of ACL rules in the default realm (which includes /sparql and /sponger, among others) for determination of whether the user may Sponge with a particular cartridge, execute the following SPARQL:

SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
  WITH  <urn:virtuoso:val:config>
    DELETE
      { oplacl:DefaultRealm  oplacl:hasDisabledAclScope  oplacl:SpongerCartridges }
    INSERT
      { oplacl:DefaultRealm  oplacl:hasEnabledAclScope   oplacl:SpongerCartridges }
;

Next, enable cartridge ACLs using the Conductor UI. To do so, navigate to the Sponger's 'Configuration' panel under the 'Linked Data' > 'Sponger' tabs, then select 'ABAC' as the cartridge ACL mode.

Cartridge ACL mode selection in Conductor

Note:

Virtuoso supports two types of cartridge ACLs for protecting access to Sponger cartridges - ABAC and RBAC ACLs. ABAC cartridge ACLs are VAL-based, and configured and managed through VAL. RBAC cartridge ACLs are SQL-role-based, and are configured and managed through the Conductor UI's 'Access Control List' panel accessible from the 'Linked Data' > 'Access Control' tab.
In the Configuration panel, option 'ABAC' is disabled if the VAL VAD isn't installed. 'None' results in no cartridge ACLs of either type being applied. If option 'ABAC' is selected, scope oplacl:SpongerCartridges must be enabled for VAL cartridge ACLs to take effect.
When the Cartridges VAD is first installed, the cartridge ACL mode is initialized to 'ABAC' if the VAL VAD is present, or 'None' otherwise. Once initialized, any cartridge ACL mode subsequently set through the Conductor UI remains in effect. If the VAL VAD is uninstalled and the cartridge ACL mode is 'ABAC', the mode is reset to 'None'.

Usage

Before using the ACL engine, it is important to load the Openlink ACL Ontology into the VAL ACL Schema graph:

SPARQL
  LOAD <http://www.openlinksw.com/ontology/acl#> 
    INTO <urn:virtuoso:val:acl:schema>
;

For Sponger ACL rules to be enforced by the SPARQL engine, the "get:enforce-acls" pragma must be set. When VAL is installed, /sparql will do this automatically:

SPARQL 
  DEFINE  get:enforce-acls  "yes" 
    SELECT ....

The Rules can be controlled via the RESTful VAL ACL API or the Internal VAL API. Alternatively, one can explicitly add the rules to the private graph matching the realm in which the rules should apply. Given the default realm --

http://www.openlinksw.com/ontology/acl#DefaultRealm

-- and default hostname "HOST" the graph IRI would be --

http://HOST/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm

-- and the groups will be stored in named graph --

http://HOST/acl/graph/groups/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm

Be aware that these graphs can be customized for better readability.

ACL Resources

Generic Sponger ACL Resource

To grant the right to Sponge in general, there is only one resource of importance: urn:virtuoso:access:sparql. Whoever has oplacl:Sponge permissions on this virtual resource can sponge in the given realm. (See SPARQL and named graph ACLs for details).

Sponger Cartridge ACLs

Each Cartridge is described as an RDF resource, and has a URI uniquely identifying it. These URIs must be used in ACL rules governing the use of that specific cartridge. As with generic Sponger access, the access mode is oplacl:Sponge.

To date, Sponger cartridge URIs are built from a common prefix, http://data.openlinksw.com/oplweb/component/xc_, plus the lowercase internal name of the cartridge. For example, the Wine cartridge has URI http://data.openlinksw.com/oplweb/component/xc_wine. Graph <urn:virtuoso:sponger:cartridges> contains the full list of cartridge URIs.

There is one special URI, which denotes all installed cartridges in a given Virtuoso instance: http://data.openlinksw.com/oplweb/component/xc_all.

Be aware that the ACL graphs can be customized for better readability.

Sponger ACL Rule Examples

In the following examples --

The default realm oplacl:DefaultRealm is used for creating the ACL resources.

"HOST" is used as a placeholder for the default hostname of the system the ACL resource are created on.

Generic Sponging ACL Examples

See SPARQL and named graph ACLs for more examples.

Allow everyone to sponge

SPARQL
PREFIX     acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
PREFIX    foaf:  <http://xmlns.com/foaf/0.1/>
  WITH  <http://HOST/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm>
    INSERT 
      {
        <#a1>                    a  acl:Authorization ;
                        foaf:maker  <http://HOST/dataspace/person/dba#this> ; 
              oplacl:hasAccessMode  oplacl:Sponge ;
                      acl:accessTo  <urn:virtuoso:access:sparql> ;
                    acl:agentClass  foaf:Agent ;
                   oplacl:hasScope  oplacl:Query ;
                   oplacl:hasRealm  oplacl:DefaultRealm 
      };

Allow user "demo" to grant Sponging permissions

By default, only "dba" and administrators can grant sponging permissions. When this rule in in place, user "demo" can create additional ACL rules granting sponging permissions to others.

SPARQL
PREFIX     acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
PREFIX    foaf:  <http://xmlns.com/foaf/0.1/>
  WITH  <http://HOST/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm>
    INSERT
      {
        <#a1>                     a  acl:Authorization ;
                         foaf:maker  <{ADMIN-IRI}> ;
               oplacl:hasAccessMode  oplacl:GrantSponge ;
                       acl:accessTo  <urn:virtuoso:access:sparql> ;
                          acl:agent  <http://HOST/dataspace/person/demo#this> ;
                    oplacl:hasScope  oplacl:Query ;
                    oplacl:hasRealm  oplacl:DefaultRealm .
      };

Grant Sponge Permissions to a Group Of People

There are two types of groups:

static -- a simple list of individuals
conditional -- a set of conditions which define a dynamic group of individuals

The rule to grant Sponge permissions to a group looks exactly like the one for granting permissions to an individual:

SPARQL
PREFIX     acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
PREFIX    foaf:  <http://xmlns.com/foaf/0.1/>
  WITH  <http://HOST/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm>
    INSERT
      {
        <#a1>                     a  acl:Authorization ;
                         foaf:maker  <{ADMIN-IRI}> ;
               oplacl:hasAccessMode  oplacl:Sponge ;
                       acl:accessTo  <urn:virtuoso:access:sparql> ;
                          acl:agent  <#group> ;
                    oplacl:hasScope  oplacl:Query ;
                    oplacl:hasRealm  oplacl:DefaultRealm .
      };

Grant Sponge Permissions to a Static Group

SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX    foaf:  <http://xmlns.com/foaf/0.1/>
  WITH  <http://HOST/acl/graph/groups/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm>
    INSERT
     {
       <#group>            a  foaf:Group, 
                              oplacl:StaticGroup ;
                   foaf:name  "Some people" ;
                 foaf:member  <http://dduck.wordpress.com> ,
                              <http://peterparker.tumblr.com/> .
     };

Grant Sponge Permissions to Anyone Who Is Authenticated

The Required Group in a conditional group which includes every authenticated NetID?:

SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX    foaf:  <http://xmlns.com/foaf/0.1/>
  WITH  <http://HOST/acl/graph/groups/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm>
    INSERT
      {
        <#group>                   a  foaf:Group , 
                                      oplacl:ConditionalGroup ;
                           foaf:name  "Valid Identifiers" ;
                 oplacl:hasCondition  [
                                                           a  oplacl:GroupCondition , 
                                                              oplacl:GenericCondition ;
                                          oplacl:hasCriteria  oplacl:NetID ;
                                        oplacl:hasComparator  oplacl:IsNotNull ;
                                             oplacl:hasValue  1
                                      ] 
      };

Grant Sponge Permissions to any Verified WebID