---+ Virtuoso Authentication Layer (VAL) - What, Why and How

%TOC%

---++ What Is the Virtuoso Authentication Layer (VAL)?

VAL, the Virtuoso Authentication Layer, is an open-standards-based, multi-protocol authentication layer, 
that provides fine-grained, attributed-based access controls (ABAC) to protected resources (HTTP-accessible 
documents, folders, services [via their endpoints], and SPARQL named graphs). In a nutshell, this solution 
uses logic, expressed in the form of entity relationships, to address issues such as identity, authorization, 
and restriction.

The key components of this solution are:

   * HTTP URI (Hyperlink) based Entity Identifiers (Names)
   * TLS based data transmission
   * RDF Language based Statements representing Entity Relationships and
     Entity Relationship Types
   * Vocabulary of terms from publicly accessible vocabularies such as 
      * <[[http://www.w3.org/ns/auth/acl#][http://www.w3.org/ns/auth/acl#]]>
      * <[[http://www.openlinksw.com/ontology/acl#][http://www.openlinksw.com/ontology/acl#]]>
      * <[[http://www.openlinksw.com/ontology/restrictions#][http://www.openlinksw.com/ontology/restrictions#]]>
      * <[[http://www.openlinksw.com/schemas/cert#][http://www.openlinksw.com/schemas/cert#]]>
   * Entity Relationship Type Semantics

Collectively, the components above enable:

   * Unambiguous Naming
   * Identity Claims Construction
   * Identity Claims Verification
   * Resource Access Rules (Authorizations) Creation and Evaluation
   * Resource Access Rate Rules (Restrictions) Creation and Evaluation
 
--++ Why Is VAL Important?

As access to data grows across users, private networks, public networks, and hybrid network dimensions, 
there is an ever-increasing demand for controlled access to this data, in a manner that covers a variety 
of operational and social dimensions. It is no longer feasible to secure data using naive literal 
identification that doesn't attend to entity relationship realities reflected in the nature of different 
kinds of entity relationships.

--++ How Do I Use VAL?

---+++ Prerequisites

   * Virtuoso Commercial Edition Instance
   * Virtuoso Authentication Layer (VAL) add-on module installation
   * Virtuoso Faceted Browser — optional; recommended for verification and troubleshooting
   * X.509 Certificates for Agents (Virtuoso Web Server and Client Software [e.g., SSH, HTTPS, ODBC, JDBC, ADO.NET applications]) that will communicate over TLS 
   * X.509 Certificates for Application Users ? optional; not necessary whn Identity Delegation is in use

---+++ Authorization Scoping

Every resource type protected by VAL is associated with a distinct ACL scope. Examples include:

   * Sponger - for the Virtuoso Sponger Middleware Layer
   * <nowiki>SpongerCartridges</nowiki> - for specific Sponger Cartridges (for finer granularity control of 
     access to the Sponger)
   * Query - for Query Services (SPARQL or SQL)
   * <nowiki>WebDAV</nowiki> - for all folders and documents accessible via <nowiki>WebDAV</nowiki> or 
     Linked Data Profile (LDP) protocols
   * OAuth - for OAuth protocol
   * Private Named Graphs -- for internal RDF documents controlled by the Virtuoso Quad Store
   * Basic Entity Description Services
   * Advanced Faceted Browsing based Entity Description Services
   * <nowiki>PivotViewer</nowiki> Data Visualization
   * URI Shortener
   * Custom Scopes created for custom applications

---+++ Virtuoso Realms

As a hybrid data server, Virtuoso provides access to data across two distinct (but interlinked) functionality 
realms: HTTP and SQL. Thus, configuring VAL requires creation of Authorization and Restrictions rules that 
target each of the aforementioned realms, individually.

VAL Authorizations apply to HTTP and/or SQL realms distinctly. Basically, you have an ACL Scope by Virtuoso 
Realms matrix per basic unit of ABAC functionality.

<img style="display: block; margin-left: auto; margin-right: auto;" src="%ATTACHURLPATH%/ACL_Configuration_UI.png"/>
<div style="text-align: center; width: 100%;"><b>Conductor's VAL Configuration UI</b></div>

---+++ Creating an ABAC ACL

You achieve this by writing a collection of RDF language statements to a special VAL system named graph. 
These statements describe an instance of an authorization, and where additional restrictions apply they 
are also used to describe resource usage rate restrictions.

----++++ Example of ABAC ACL

<verbatim>
## Declaring an Authorization granting read-access to the named graph identified by the IRI 
## <OpenPermID-bulk-assetClass-20151111_095807.ttl.gz>
 
SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
PREFIX     acl:  <http://www.w3.org/ns/auth/acl#>

WITH
   <http://linkeddata.uriburner.com/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23DefaultRealm>
INSERT
   {
     <#PrivateNamedGraphRule1> 
       a                     acl:Authorization ;
       foaf:maker            <http://kingsley.idehen.net/dataspace/person/kidehen#this> ;
       oplacl:hasAccessMode  oplacl:Read ;
       acl:accessTo          <OpenPermID-bulk-assetClass-20151111_095807.ttl.gz> ;
       acl:agent             <https://s3.amazonaws.com/webid-sandbox/Profile/Basic-Identity-Claims-And-Profile-Document.ttl#i> ;
       oplacl:hasScope       oplacl:PrivateGraphs ;
       oplacl:hasRealm       oplacl:DefaultRealm .
  };
</verbatim>

---+++Protecting an HTTP Realm (aka <nowiki>DefaultRealm</nowiki>) Service

To protect HTTP Services provided by a Virtuoso instance such as: SPARQL endpoints, <nowiki>WebDAV</nowiki> 
and LDP file systems, Faceted Browsing, Sponger Entity Description Pages, <nowiki>PivotViewer</nowiki>, 
URL Shortener, and SPARQL/SQL Interactive Query Builder, etc., you need create the following:

   1 Describe your ACL using RDF Statements based on terms from the 
     &lt;[[http://www.w3.org/ns/auth/acl#][http://www.w3.org/ns/auth/acl#]]&gt;, 
     &lt;[[http://www.openlinksw.com/ontology/acl#][http://www.openlinksw.com/ontology/acl#]]&gt;, 
     and &lt;[[http://www.openlinksw.com/ontology/restrictions#][http://www.openlinksw.com/ontology/restrictions#]]&gt; 
     vocabularies.
   1 Load your ACLs to the Virtuoso Quad Store hosted VAL system named graph using one of the following:
      * Virtuoso's RDF document loader
      * SPARQL
      * SPARQL inside SQL - via Conductor or command-line ISQL interfaces.
   1 Test your ACL

---++++ Troubleshooting ACLs on HTTP Realm

If your ACL doesn't perform as expected please check the following:

   * <b>Your desired ACL scope is enabled</b> - this will be visible via the Conductor Configuration URI 
     for VAL or it can be looked up via its HTTP URI using the Faceted Browser or SPARQL.
   * <b>The enabled ACL scope is associated with the <nowiki>DefaultRealm</nowiki></b> - this is what 
     binds an ACL to the HTTP functionality realm and this will be visible via the Conductor Configuration 
     UI for VAL or it can be lookedup via its HTTP URI using the Faceted Browser or SPARQL.

---+++ Protecting a SQL Realm (aka <nowiki>SqlRealm</nowiki>) Service

To protect SQL Services provided by a Virtuoso instance (e.g., ODBC, JDBC, ADO.NET, OLE-DB connectivity and 
access; SPASQL (SPARQL inside SQL); etc.), you need to take the following steps:

   1 Create RDF statements, based on terms from the 
     &lt;[[http://www.w3.org/ns/auth/acl#][http://www.w3.org/ns/auth/acl#]]&gt;, 
     &lt;[[http://www.openlinksw.com/ontology/acl#][http://www.openlinksw.com/ontology/acl#]]&gt;, and 
     &lt;[[http://www.openlinksw.com/ontology/restrictions#][http://www.openlinksw.com/ontology/restrictions#]]&gt; 
     vocabularies, that describe each of the following
      * a SQL Realm access authorization, for example &mdash;
<verbatim>
-- SQLRealm ACL
-- Cleanup

SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#>
PREFIX     acl:  <http://www.w3.org/ns/auth/acl#>

WITH 
  <http://id.myopenlink.net/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23SqlRealm>
DELETE 
  {
     <#WebIDTLSSQLAccessRule1>  ?p  ?o . 
  };

-- ACL Definition 

-- SQL Access Privileges Grant to a Specific WebID --

SPARQL
PREFIX  oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX     acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX    foaf:  <http://xmlns.com/foaf/0.1/>

WITH GRAPH 
  <http://id.myopenlink.net/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23SqlRealm>
INSERT 
  {
    <#WebIDTLSSQLAccessRule1> 
       a                     acl:Authorization ;
       foaf:maker            <http://kingsley.idehen.net/dataspace/person/kidehen#this> ;
       rdfs:label            "SQL Realm Access Authorization ACL" ;
       rdfs:comment          """Mandatory ACL for granting access to SQL Realm which then enables ODBC, JDBC, ADO.NET, OLE-DB compliant
                                application access, subject to Agent & User Identity.""" ;
       oplacl:hasAccessMode  oplacl:Read ;
       acl:accessTo          <urn:virtuoso:access:sparql> ;
       acl:agent             <http://id.myopenlink.net/dataspace/person/kidehen#this> ,
                             <http://kingsley.idehen.net/dataspace/person/kidehen#this> ,
                             <https://s3.amazonaws.com/webid-sandbox/Profile/Basic-Identity-Claims-And-Profile-Document.ttl#i> ,
                             <http://kingsley.idehen.net/public_home/kidehen/profile.ttl#i> , 
                             <https://dbfff61d85d4da9b5aefce09723385e78a93f731.googledrive.com/host/0B-Mx14cLTEsaczdJdk96UVQ0aVE/profile.ttl#identity> ;
       oplacl:hasScope       oplacl:Query ;
       oplacl:hasRealm       oplacl:SqlRealm .
  };

</verbatim>
      * a SQL Realm usage rate per second restriction, for example &mdash;
<verbatim>
-- SQL Query Access Restrictions (SQLRealm re. ODBC, JDBC, ADO.NET) -- 
-- Query Request Rate
-- Cleanup

SPARQL 

PREFIX   oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX      acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX     foaf:  <http://xmlns.com/foaf/0.1/>
PREFIX  oplrest:  <http://www.openlinksw.com/ontology/restrictions#>

WITH GRAPH 
  <http://id.myopenlink.net/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23SqlRealm>
DELETE
  {
     <#IDMyOpenLinkTLSSQLAccessRestriction1>  ?p  ?o . 
  };

-- Restriction Definition

SPARQL 

PREFIX   oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX      acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX     foaf:  <http://xmlns.com/foaf/0.1/>
PREFIX  oplrest:  <http://www.openlinksw.com/ontology/restrictions#>

WITH GRAPH
   <http://id.myopenlink.net/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23SqlRealm>
INSERT
  {
    <#IDMyOpenLinkTLSSQLAccessRestriction1> 
       a                              oplrest:Restriction ;
       foaf:maker                     <http://kingsley.idehen.net/dataspace/person/kidehen#this> ;
       rdfs:label                     "SQL Realm Query Rate Restriction" ;
       rdfs:comment                   """Mandatory Restriction for metering Query Request Rates per second.""" ;
       oplrest:hasRestrictedResource  <urn:virtuoso:restrictions:sql-request-rate> ;
       oplrest:hasMaxValue            "100"^^xsd:integer ;
       acl:agent                      <http://id.myopenlink.net/dataspace/person/kidehen#this> ,
                                      <http://kingsley.idehen.net/dataspace/person/kidehen#this> ,
                                      <https://s3.amazonaws.com/webid-sandbox/Profile/Basic-Identity-Claims-And-Profile-Document.ttl#i> ,
                                      <http://kingsley.idehen.net/public_home/kidehen/profile.ttl#i> , 
                                      <https://dbfff61d85d4da9b5aefce09723385e78a93f731.googledrive.com/host/0B-Mx14cLTEsaczdJdk96UVQ0aVE/profile.ttl#identity> ;
       oplacl:hasRealm                oplacl:SqlRealm .
};

</verbatim>
      * a SQL Realm Max Rows per query result set [solution] restriction, for example &mdash;
<verbatim>
-- Query Results Size 
-- Cleanup

SPARQL 

PREFIX   oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX      acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX     foaf:  <http://xmlns.com/foaf/0.1/>
PREFIX  oplrest:  <http://www.openlinksw.com/ontology/restrictions#>

WITH GRAPH
   <http://id.myopenlink.net/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23SqlRealm>
DELETE
  {
     <#IDMyOpenLinkTLSSQLAccessRestriction2>  ?p  ?o . 
  };


-- Restriction Definition
SPARQL 

PREFIX   oplacl:  <http://www.openlinksw.com/ontology/acl#> 
PREFIX      acl:  <http://www.w3.org/ns/auth/acl#>
PREFIX     foaf:  <http://xmlns.com/foaf/0.1/>
PREFIX  oplrest:  <http://www.openlinksw.com/ontology/restrictions#>

WITH GRAPH
   <http://id.myopenlink.net/acl/graph/rules/http%3A%2F%2Fwww.openlinksw.com%2Fontology%2Facl%23SqlRealm>
INSERT
  {
    <#IDMyOpenLinkTLSSQLAccessRestriction2> 
       a                              oplrest:Restriction ;
       foaf:maker                     <http://kingsley.idehen.net/dataspace/person/kidehen#this> ;
       rdfs:label                     "SQL Realm Resultset [Query Solution] Size Restriction" ;
       rdfs:comment                   """Mandatory Restriction for restrictng maximum size of query resultsets [solutions].""" ;
       oplrest:hasRestrictedResource  <urn:virtuoso:restrictions:sql-result-rows> ;
       oplrest:hasMaxValue            "200"^^xsd:integer ;
       acl:agent                      <http://id.myopenlink.net/dataspace/person/kidehen#this> ,
                                      <http://kingsley.idehen.net/dataspace/person/kidehen#this> ,
                                      <https://s3.amazonaws.com/webid-sandbox/Profile/Basic-Identity-Claims-And-Profile-Document.ttl#i> ,
                                      <http://kingsley.idehen.net/public_home/kidehen/profile.ttl#i> , 
                                      <https://dbfff61d85d4da9b5aefce09723385e78a93f731.googledrive.com/host/0B-Mx14cLTEsaczdJdk96UVQ0aVE/profile.ttl#identity> ;
       oplacl:hasRealm                oplacl:SqlRealm .
};

</verbatim>
   1 Load your ACLs to the Virtuoso Quad Store hosted VAL system named graph using one of the following:
      * Virtuoso's RDF document loader
      * SPARQL
      * SPARQL inside SQL - via Conductor or command-line ISQL interfaces.
   1 Test your ACL

---++++ Troubleshooting ACLs on SQL Realm 

If your ACL doesn't perform as expected, please check the following:

   * <b>Existence of an Authorization</b> - You can look up the existence of your Authorization via its HTTP URI using the 
     Faceted Browser or SPARQL.
   * <b>Existence of a Restriction</b> - You can look up the existence of your Restriction via its HTTP URI using the 
     Faceted Browser or SPARQL.
   * <b>Your desired ACL scope is enabled</b> - this will be visible via the Conductor Configuration UI for VAL or 
     it can be looked up via its HTTP URI using the Faceted Browser or SPARQL.
   * <b>The enabled ACL scope is associated with the <nowiki>DefaultRealm</nowiki></b> - this is what binds an ACL 
     to the HTTP functionality realm and will be visible via the Conductor Configuration UI for VAL or it can 
     be looked-up via its HTTP URI using the Faceted Browser or SPARQL.

---

---++ Further Reading

   * [[ValQuickStartGuide][Virtuoso Authentication Layer - ACL System Quickstart Guide]]

---