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  1. Introduction ===============

libAuthentication is a PHP implementation of the FOAF+SSL protocol. Further details of FOAF+SSL can be obtained at

If you would like to learn how to get going quickly without diving to much into technical details, then read section 2. and 3.

The core classes of libAuthentication are tackled in section 4. and 5.

  1. How to set up Foaf+SSL authentication in a few lines of code ================================================================================

There are a few flavours of Foaf+SSL authentication. The following very simple example shows how to setup a Foaf+SSL authentication relying on an identity provider such as


  • Publicly available internet site
  • Apache 2.2 and PHP 5.2.x or higher

Checkout and create a script that will be the entry point for your application:

git clone git://

cat > index.php

$auth = new Authentication_FoafSSLDelegate();

if (!$auth->isAuthenticated()) 
  echo $auth->authnDiagnostic;
  echo '<a href="">Click here to Login</a>';
  echo 'Your have succesfully logged in.<pre>';

Make sure the "authreqissuer" points to YOUR site and...

You just set up you first Foaf+SSL powered site. Behind the scenes, libAuthentication has a copy of's certificate which is used in the authentication process.

Note that if you wish to use another delegated identity verification service (for instance ''), you maye need to change line 4 as :

$auth = new Authentication_FoafSSLDelegate(TRUE, NULL, Authentication_URL::parse(''));

Then you'd change the login link to :

echo '<a href="">Click here to Login</a>';

This will ensure that you wish to verify the server's response signature according to the proper certificate already present in Authentication_X509CertRepo.php

  1. A more complex setup ================================================================================

If you run your own database that contains Foaf profiles, you can use the Authentication class that handles all supported authentication methods automatically.

Note: config.php must be configured with the details of the db you have created for ARC2. Further details of ARC2 are at

Note: The current RDF library has a dependency on mysql, so it will only work if you have mysql installed.

You can find the code in examples/authenticationlogin.php

Calling new Authentication() tests if the user has presented a SSL Client Certificate that matches to public key as expressed in a FOAF file. Authentication can work with SSL Client Certificates presented to your server or with the FOAF+SSL login delegation server. To use the delegated FOAF+SSL version ask the user to click on something like the following:

In this case executes new Authentication($config). Alternatively configured your server to request Client Certificates on the https page the user tries to access. The page needs to execute new Authentication($config).

Authentication stores the result of the user login process in a session so subsequent calls to Authentication's constructor do not preform any further remote checks on FOAF files. To re-perform the FOAF fetch you need to execute



Authentication will try to create a session variable therefore it is very important to execute new Authentication() before any html is sent to the client. Further details here

  1. Brief overview of libAuthentication's core classes ================================================================================

libAuthentication provides the following core classes:

  • Authentication_AgentARC Parse a Foaf file identified by a Webid (e.g. )

  • Authentication Authenticate user by trying all supported authentication methods in a fixed and reasonable sequence

  • Authentication_FoafSSLDelegate Authenticate via the delegated Foaf+SSL method using a 3rd party FoafSSL identity provider ( by default)

  • Authentication_FoafSSLARC Authenticate via "native" Foaf+SSL by relying on a database that stores Foaf files. (currently the ARC RDF store is used as storage backend)

  • Authentication_Session Create a session cookie after successful authentication to speed up subsequent authentication attempts

A detailed description of the core classes an their usage follows.

  1. Detailed description of libAuthentication's core classes ================================================================================

class Authentication_AgentARC (implements Authentication_AgentAbstract)

This is basically a parser for a Foaf file identified by a URI, like

It relies on ARC RDF Store.

Assuming you pass it a valid URI and appropriate store configuration, it loads the corresponding foaf document.

$config =  array ('db_name'  => 'your_db_name',        // db name  
                  'db_user'    => 'your_db_username',  // db username  
                  'db_pwd'    => 'your_password',     // db password  
            'store_name'    => 'arc_tests',           // tmp table name  
$webid = '';  
$foafDoc = new Authentication_AgentARC($config, $webid);  

$foafDoc->agentURI contains the URI passed in.

On Success:

$foafDoc->agentId contains the value of the primaryTopic property if defined, otherwise it falls back to $this->agentURI.

You can get the parsed foaf file properties as an associative map.

$foafProperties = $foafDoc->getAgent()

These properties are currently (only those appear that are found in the foaf file): name, mbox, homepage, nick, weblog, img, RSAKey (with mod and exp) and more. The semantics of these properties are defined in

On Error:

You can retrieve error message by inspecting the content of


(an array).

Note: If the ARC store doesn't exists (first run), it will be created and setup automatically. However, the parsing will obviously fail, since the store is empty.

class Authentication

This class provides easy access to all supported authentication mechanisms. On instantiation, it performs the following operations:

  1. Checks if an authentication session cookie is present

  2. If 1. fails, it tries to authenticate via delegated Foaf+SSL (see Authentication_FoafSSLDelegate)

  3. If 2. fails, it tries to authenticate via native Foaf+SSL (see Authentication_FoafSSLARC)

  4. If authentication is successful, it loads the corresponding foaf file

    $auth = new Authentication($config) // $config is optional,  
                                        // only necessary if ARC is used

On Success:

  • $auth->isAuthenticated() returns true
  • $auth->webid contains the authenticated webid
  • $auth->getAgent() returns the parsed foaf profile that is tied to the authenticated webid (as in Authentication_AgentARC)

On Error:

If an error occurs, an explanation can be retrieved by inspecting $auth->$authnDiagnostic. If you want to terminate the authenticated session, it is a good idea to call $auth->logout.

class Authentication_Session

This class usually won't be instantiated directly. If a given authentication method succeeds, it can optionally persist that information by instantiating Authentication_Session. It stores the authenticated webid and the parsed foaf file in $_SESSION. This results in a significant speed up in successive authentication attempts. If you want to create it manually, you can do that as follows:

$authSession = new Authentication_Session( 1, $agent, $webid)

where 1 indicates the fact of successful authentication, $agent is an associative array representation of the Foaf file that is associated with $webid, which is a URI string.

class Authentication_FoafSSLDelegate

Using the delegated Foaf+SSL method is probably the easiest way to get you start quickly leveraging this powerful authentication method. It is also the easiest to set up. Refer to Section 2. for an example and make sure you set up the example using a public domain name or a public IP address. I you want find out more details how the identity provider works, see

You need to instantiate Authentication_FoafSSLDelegate at a common entry point to your site (e.g. index.php):

$auth = new Authentication_FoafSSLDelegate();

Most of the input is automatically retrieved from the global php context variables ($_REQUEST, $_SERVER etc.), so using the default constructor parameters is fine.

On Success:

  • $auth->isAuthenticated() returns true
  • $auth->webid contains the authenticated webid

If not explicitly disabled, on successful authentication an instance of Authentication_Session will also be created, to speed up further authentication attempts. If that something you don't want to happend, you need to call the constructor as follows:

$auth = new Authentication_FoafSSLDelegate( false );

On Error:

If an error occurs, an explanation can be retrieved by inspecting $auth->$authnDiagnostic. If you want to terminate the authenticated session, it is a good idea to call $auth->logout.

class Authentication_FoafSSLARC (implements Authentication_FoafSSLAbstract)

This implements the "native" Foaf+SSL authentication. The current implementation relies on the ARC RDF store. The public key tied to the webid is extracted via Sparql query, as are other properties of the corresponding foaf file. To perform the authentication, you only need

$auth = new Authentication_FoafSSLARC($config)

where $config is the same configuration you used for Authentication_AgentARC. The rest of the constructor parameters are better left at their default value.

On Success:

  • $auth->isAuthenticated() returns true
  • $auth->webid contains the authenticated webid
  • $auth->certModulus modulus of the associated public key
  • $auth->certExponent exponent of the associated public key
  • $auth->certSubjectAltName subjectAltName from the x509 extension section

FoafSSLARC (FoafSSLAbstract) also instantiates a Authentication_Session. You can disable that by passing "false" as 3rd parameter.

$auth = new Authentication_FoafSSLARC($config, NULL, false);

On Error:

If an error occurs, an explanation can be retrieved by inspecting $auth->$authnDiagnostic. If you want to terminate the authenticated session, it is a good idea to call $auth->logout.


For detailed information on libAuthentication classes please refer to the API documentation.

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