/ 
CGI-Auth-FOAF_SSL-1.00_01
/ CGI::Auth::FOAF_SSL

NAME

CGI::Auth::FOAF_SSL - authentication using FOAF+SSL

SYNOPSIS

use CGI qw(:all);
use CGI::Auth::FOAF_SSL;

my $auth = CGI::Auth::FOAF_SSL->new_from_cgi( CGI->new );

print header('-type' => 'text/html', '-cookie' => $auth->cookie);

if (defined $auth && $auth->is_secure)
{
  if (defined $auth->agent)
  {
    printf("<p>Hello <a href='%s'>%s</a>!</p>\n",
           escapeHTML($auth->agent->homepage),
           escapeHTML($auth->agent->name));
  }
  else
  {
    print "<p>Hello!</p>\n";
  }
}
else
{
  print "<p>Greetings stranger!</p>\n";
}

VERSION

1.00_01

DESCRIPTION

FOAF+SSL is a simple authentication scheme described at http://esw.w3.org/topic/foaf+ssl. This module provides FOAF+SSL authentication for CGI scripts written in Perl.

This requires the web server to be using HTTPS and to be configured to request client certificates and to pass the certificate details on as environment variables for scripts. If you are using Apache, this means that you want to set the following directives in your SSL virtual host setup:

SSLEngine on
# SSLCipherSuite (see Apache documentation)
# SSLProtocol (see Apache documentation)
# SSLCertificateFile (see Apache documentation)
# SSLCertificateKeyFile (see Apache documentation)
SSLVerifyClient optional_no_ca
SSLVerifyDepth  1
SSLOptions +StdEnvVars +ExportCertData

Configuration

$CGI::Auth::FOAF_SSL::path_openssl = '/usr/bin/openssl'

Set the path to the OpenSSL binary.

$CGI::Auth::FOAF_SSL::ua_string = 'MyTool/1.0'

Set the User-Agent string for any HTTP requests.

Constructors

$auth = CGI::Auth::FOAF_SSL->new($pem_encoded)

Performs FOAF+SSL authentication on a PEM-encoded key. If authentication is completely unsuccessful, returns undef. Otherwise, returns a CGI::Auth::FOAF_SSL object. Use is_secure to check if authentication was completely successful.

You probably want to use new_from_cgi instead.

$auth = CGI::Auth::FOAF_SSL->new_from_cgi($cgi_object)

Performs FOAF+SSL authentication on a CGI object. This is a wrapper around new which extracts the PEM-encoded client certificate from the CGI request. It has the same return values as new.

If $cgi_object is omitted, uses CGI->new instead.

Public Methods

$bool = $auth->is_secure

Returns true iff the authentication process was completely successful.

What does it mean for the authentication process to have been partially successful? There are two such situations:

  • The rdf:type of the URI given in subjectAltName could not be established.

    Perhaps no RDF could be found which provides an rdf:type for the URI, or if an rdf:type is found, it is one that this module does not recognise.

  • The subjectAltName URI is established to be a foaf:OnlineAccount, but no account holder is confirmed.

    To confirm that the account in question belongs to someone, the RDF data associated with the account must provide the URI of an account holder. Whatsmore the RDF data associated with the account holder's URI must confirm that the account really does belong to them.

    This means that when dereferencing the subjectAltName and finding that it identifies an account ?account, the data must provide the following triples:

    ?webid foaf:account ?account .
?account a foaf:OnlineAccount .

    And when ?webid is dereferenced, it must also provide this triple:

    ?webid foaf:account ?account .

In either of these two situations, it is probably not safe to trust any data you get back from the agent, account or certified_thing methods (except perhaps $auth->certified_thing->identity).

$agent = $auth->agent

Returns a CGI::Auth::FOAF_SSL::Agent object which represents the agent making the request. Occasionally undef.

$account = $auth->account

Returns a CGI::Auth::FOAF_SSL::OnlineAccount object which represents the online account of the agent making the request. Usually undef.

$thing = $auth->certified_thing

Returns a CGI::Auth::FOAF_SSL::CertifiedThing object (or a descendent class) which represents the thing given in the certificate's subjectAltName.

Usually you will want to use agent or account instead.

$cookie = $auth->cookie

HTTP cookie related to the authentication process. Sending this to the client isn't strictly necessary, but it allows for a session to be established, greatly speeding up subsequent accesses. See also the COOKIES section of this documentation.

Utility Method

$model = $auth->get_trine_model($uri)

Get an RDF::Trine::Model corresponding to a URI.

COOKIES

FOAF+SSL is entirely RESTful: there is no state kept between requests. This really simplifies authentication for both parties (client and server) for one-off requests. However, because FOAF+SSL requires the server to make various HTTP requests to authenticate the client, each request is slowed down significantly.

Cookies provide us with a way of speeding this up. Use of cookies is entirely optional, but greatly increases the speed of authentication for the second and subsequent requests a client makes. If your FOAF+SSL-secured service generally requires clients to make multiple requests in a short period, you should seriously consider using cookies to speed this up.

The method works like this: on the first request, authentication happens as normal. However, all RDF files relevant to authenticating the client are kept on disk (usually somewhere like '/tmp') in N-Triples format. They are associated with a session that is given a randomly generated identifier. This random identifier is sent the client as a cookie. On subsequent requests, the client includes the cookie and thus CGI::Auth::FOAF_SSL is able to retrieve the data it needs from disk in N-Triples format, rather than having to reach out onto the web for it again.

To use this feature, you must perform authentication before printing anything back to the client, use CGI::Auth::FOAF_SSL's cookie method, and then pass that to the client as part of the HTTP response header.

use CGI qw(:all);
use CGI::Auth::FOAF_SSL;

my $auth = CGI::Auth::FOAF_SSL->new_from_cgi;

if (defined $auth && $auth->is_secure)
{
  print header('-type' => 'text/html',
               '-cookie' => $auth->cookie);

  my $user = $auth->agent;
  # ...
}
else # anonymous access
{
  print header('-type' => 'text/html');
  
  # ...
}

Old sessions are automatically purged after an hour of inactivity.

BUGS

Please report any bugs to http://rt.cpan.org/.

SEE ALSO

Helper modules: CGI::Auth::FOAF_SSL::CertifiedThing, CGI::Auth::FOAF_SSL::Agent, CGI::Auth::FOAF_SSL::OnlineAccount.

Related modules: CGI, RDF::Trine, RDF::ACL.

Information about FOAF+SSL: http://lists.foaf-project.org/mailman/listinfo/foaf-protocols, http://esw.w3.org/topic/foaf+ssl.

SSL in Apache: http://httpd.apache.org/docs/2.0/mod/mod_ssl.html.

Mailing list for general Perl RDF/SemWeb discussion and support: http://www.perlrdf.org/.

AUTHOR

Toby Inkster, <tobyink@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2009-2010 by Toby Inkster

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8 or, at your option, any later version of Perl 5 you may have available.