[otrs] Login from outside

Hi, I managed to make otrs use the same customer database as my e-commerce site does. I was wondering what would be the best way to make the user logged in otrs once it logs in the e-commerce site. I'm mentioning that i use sites like xyz.co.uk, xyz.de for localization and the otrs is located at support.xyz.com (might be some troubles with cookies). Thanks in advance, Alexandru Palade.