oracular (3) Web::ID::FAQ.3pm.gz
NAME
Web::ID::FAQ - frequently asked questions about WebID
FREQUENTLY ASKED QUESTIONS
So what is WebID?
Web Identification and Discovery.
Firstly it's the concept of identifying people with HTTP URIs. URI stands for Uniform Resource
Identifier. While often used as identifiers for web pages and other digital resources, they're just
string identifiers and may be used to identify anything - car parts, gorillas, abstract concepts, and,
yes, people.
WebID is also a protocol that allows websites to discover which URI identifies you, using a secure
certificate that is installed in your browser.
URIs can identify non-digital resources?
Yes. Of course, if you type a URI which identifies a web page into a web browser, you'd expect to see
that web page (or an error message explaining why you cannot), but if you type a URI which identifies a
car part, don't expect that spark plug to jump out of your screen into your hands.
URIs that identify non-digital resouces should either be unresolvable (e.g. "urn:isbn:978-0099800200"
which identifies a book - your browser can't do anything with that URI); should produce an error message
explaining why the resource cannot be provided; or should redirect to a digital resource (e.g.
"http://example.com/id/alice" might identify Alice, and redirect to "http://example.com/data/alice" which
is a document with information about Alice).
Further reading: Cool URIs for the Semantic Web, <http://www.w3.org/TR/cooluris/>.
So I can use WebID to limit who has access to my site?
On its own, no.
WebID allows a website to establish an identifier for a visitor, but what the website does with that
information (whether it uses it to block access to certain resources) is beyond the scope of WebID.
How does WebID work?
In summary, your browser establishes an HTTPS connection to a web server. As part of the SSL/TLS
handshake, the server can request that the browser identifies itself with a certificate. Your browser
then sends your certificate to the server. This certificate includes a URI that identifies you.
Behind the scenes, the server fetches that URI, and retrieves a profile document about you (this document
can include as much or as little personal data about you as you like). This document uses the RDF data
model, and contains data that allows the server to verify that the certificate exchanged as part of your
HTTPS request really belongs to you.
The user experience is that a WebID user visits a WebID-enabled site; their browser prompts them to pick
a certificate from the list of installed certificates; they choose; the site knows who they are.
No passwords are required (though many browsers do offer the option to protect the installed certificates
with a password).
So WebID requires HTTPS?
WebID could theoretically be used over other SSL/TLS protocols, such as OpenVPN, secure IMAP/POP3
connections, and so forth.
But yes, it only works over secure connections. Really, would you want to be identifying yourself over an
insecure channel?
How can I use WebID in Perl?
For Plack/PSGI-based websites, there exists a module Plack::Middleware::Auth::WebID to make things
(relatively) easy. It stuffs the client's WebID URI into "$env->{WEBID}".
For Catalyst-based websites, be aware that recent versions of Catalyst are built on Plack. See
Catalyst::PSGI for details.
Otherwise, you need to use Web::ID directly. Assuming you've configured your web server to request a
client certificate from the browser, and you've managed to get that client certificate into Perl in PEM
format, then it's just:
my $webid = Web::ID->new(certificate => $pem);
my $uri = $webid->uri;
And you have the URI.
What is PEM? Well, X509 certificates come in a variety of different interrelated formats. PEM is a common
one, and often what web servers make available. If you have DER though, it's easy to convert it to PEM:
my $pem = "\n-----BEGIN CERTIFICATE-----\n"
. encode_base64($der)
. "\n-----END CERTIFICATE-----\n";
If you have another format, then OpenSSL may be able to convert it.
Once you have the URI, you can use it as a plain old string identifier for the user, whenever you need to
identify them in databases, etc.
The $webid object in the above example, or in the Plack middleware, "$env->{WEBID_OBJECT}", is an object
blessed into the Web::ID package and will allow you to retrieve further information about the user -
their name, e-mail address, blog URL, interests, friends, etc - depending on what information they've
chosen to include in their profile.
How does WebID compare to OpenID?
Both use URIs to identify people, however the way they choose their URIs differs. In OpenID you use the
same URI string to identify your blog or homepage, and to identify yourself. In WebID you use different
URIs to identify different things - one URI for your blog, one for you.
In WebID you almost never have to type that URI - it's embedded into a certificate in your browser's
certificate store.
WebID doesn't require typing or passwords. This makes it more suitable than OpenID for non-interactive
processes (e.g. authenticated downloads run via a cron job).
WebID requires a secure connection.
WebID is built upon the architecture of the Semantic Web.
SEE ALSO
Web::ID.
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2012 by Toby Inkster.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
programming language system itself.
This FAQ document is additionally available under the Creative Commons Attribution-ShareAlike 2.0 UK:
England and Wales licence <http://creativecommons.org/licenses/by-sa/2.0/uk/>, and the GNU Free
Documentation License version 1.3, or at your option any later version <http://www.gnu.org/licenses/fdl>.
DISCLAIMER OF WARRANTIES
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.