xAuth

xAuth aims to provide a relatively simple, secure and flexible cross site authentication mechanism. This could be used for one-directional Single Sign On (SSO) between a non-Drupal system and your Drupal instance.

Firstly, xAuth is not a perfect SSO solution. If you are looking for seemless SSO between sites, then you probably want to look into other solutions that make use of SAML.

Setting up true-blue SSO between disparate systems can sometimes pose a real challenge. xAuth may help your requirements somewhat.

xAuth creates a url that looks like http://our.drupal.site/xa/ccknode/bevan/sessid12345/703173eda5

From this, we log the user bevan into drupal and redirect to a page specified by the node of type xauth_path idenfified by ccknode. The final parameter is a hash.

* sessid1235 is used in combination with username to authenticate an open session on dotCMS for that user
* 703173eda5 is the first 10 chars of an MD5 checksum of the username, session_key, a shared secret key and a timestamp.