Net_WebFinger

WebFinger client library for PHP.

Discover meta data about users by just their email address. Discoverable data may be the user's OpenID, profile page URL, link to portable contacts, hcard, foaf and other user pages.

Distributed social networks use WebFinger to distribute public encryption keys, OStatus and Salmon URLs.

Package supports Webfinger (RFC 7033) and can fall back to RFC 6415 (host-meta + lrdd).

Contents

• Error handling
  • Error handling example
• Examples
  • OpenID discovery
  • Simple link access
  • Accessing all links
  • Caching
  • Security
  • Custom HTTP adapter
• Testing
• Links
  • References
  • Alternate implementations

Error handling

The package does not throw any exceptions. Technically, Net_WebFinger_Error objects are exceptions, but they are only set as $error property in the Net_WebFinger_Reaction object.

You can ignore them completely if you're just out to get the data.

Sometimes it's even necessary to ignore the data. Yahoo! for example has a host-meta file, but no LRDD files. The OpenID provider URL already noted in host-meta, so even though fetching the LRDD file fails, information about the OpenID provider is available.

Error handling example

The Net_WebFinger_Reaction object has an $error property that contains an exception with error message and code. It often even has a previous exception object with more underlying details:

<?php
require_once 'Net/WebFinger.php';
$wf  = new Net_WebFinger();
$react = $wf->finger('[email protected]');


if ($react->error !== null) {
    echo "Error when fetching " . $react->url . "\n";
    echo "Error: " . $react->error->getMessage() . "\n";
    if ($react->error->getPrevious()) {
        echo "Underlying error: "
            . $react->error->getPrevious()->getMessage() . "\n";
    }
}
?>

Examples

OpenID discovery

<?php
require_once 'Net/WebFinger.php';
$wf = new Net_WebFinger();
$react = $wf->finger('[email protected]');
if ($react->error) {
    echo 'There was an error: ' . $react->error->getMessage() . "\n";
}
$openIdProvider = $react->get('http://specs.openid.net/auth/2.0/provider');
if ($openIdProvider !== null) {
    echo 'OpenID provider found: ' . $openIdProvider . "\n";
}
?>

Simple link access

Some common link relations have a short name in Net_WebFinger. Those short names can be used to access them more easily:

<?php
require_once 'Net/WebFinger.php';
$wf  = new Net_WebFinger();
$react = $wf->finger('[email protected]');
if ($react->error) {
    echo 'There was an error: ' . $react->error->getMessage() . "\n";
}
if ($react->openid !== null) {
    echo 'OpenID provider found: ' . $react->openid . "\n";
}
?>

Currently supported short names:

• contacts
• hcard
• openid
• profile
• xfn

See the list $shortNameMap in class Net_WebFinger_Reaction.

Accessing all links

You can use foreach on the reaction object to get all links:

<?php
require_once 'Net/WebFinger.php';
$wf = new Net_WebFinger();
$react = $wf->finger('[email protected]');
foreach ($react as $link) {
    echo 'Link: ' . $link->rel . ' to ' . $link->href . "\n";
}
?>

Caching

With caching, the retrieved files will be stored locally which leads to faster lookup times when the same identifier (email address) is loaded again, and when another identifier on the same host is retrieved.

<?php
require_once 'Net/WebFinger.php';
require_once 'Cache.php';
$wf = new Net_WebFinger();
$wf->setCache(
    new Cache('file', array('cache_dir' => sys_get_temp_dir() . '/myapp'))
);
$react = $wf->finger('[email protected]');
$openIdProvider = $react->get('http://specs.openid.net/auth/2.0/provider');
?>

Note: PEAR's Cache_Lite package does not support per-item lifetimes, so we cannot use it: http://pear.php.net/bugs/bug.php?id=13297

Security

All files will be retrieved via SSL when possible, with fallback to normal HTTP.

The fallback for pure webfinger files does only happen when $fallbackToHttp is enabled. Fallback for host-meta and LRDD files is always on.

The XRD subject is also verified. When it does not match the host name of the email address, then the error object is set.

<?php
require_once 'Net/WebFinger.php';
$wf  = new Net_WebFinger();
$react = $wf->finger('[email protected]');
if ($react->error || !$react->secure) {
    die("Those data may not be trusted\n");
}

Custom HTTP adapter

If you want to send special HTTP headers or need e.g. proxy settings, you may use an own HTTP adapter that's used to fetch the files:

<?php
require_once 'HTTP/Request2.php';
require_once 'Net/WebFinger.php';

$req = new HTTP_Request2();
$req->setConfig('follow_redirects', true);//needed for full compatibility
$req->setHeader('User-Agent', 'MyApp 1.42');

$wf = new Net_WebFinger();
$wf->setHttpClient($req);
$react = $wf->finger('[email protected]');

Testing

You can use this identifiers to test the WebFinger functionality on various providers:

• Gmail: [email protected]
• Yahoo: [email protected]
• AOL: [email protected]
• other:
  • [email protected]
  • [email protected] https://github.com/intridea/redfinger/issues/2
• diaspora: [email protected]
• status.net: [email protected]

Links

References

• Webfinger mailing list
• First webfinger specification
• Common link relations
• IETF webfinger draft
• http://hueniverse.com/2009/09/implementing-webfinger/
• http://hueniverse.com/2009/09/openid-and-lrdd/
• http://paulosman.me/2010/02/01/google-webfinger.html Google have since rolled out WebFinger support for everyone with a Google Profile.
• Finger history
• XRD 1.0 specification

Alternate implementations

See http://www.packetizer.com/webfinger/software.html

• Ruby:
  • Redfinger
  • Webfinger
• Perl: WWW::Finger::Webfinger
• PHP: discovery-php
• PHP Wordpress plugin: Blogpost, webfinger-profile plugin